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Modelling of Soyuz Docking and Radar Systems

1. 2 04 Phase angle between Soyuz vehicle and ISS Far phase of rendezvous ee et tan Target offset during rendezvous phase ooo Block diagram of Kalman filter and its parameters Near phase of rendezvous o oo 444 a a ae a nn Soyuz vehicle docked to the International Space Station Image courtesy ONASA peoria HA PRES a a a he a Model of Soyuz capsule at the Space Systems Institute Image courtesy Simulator cockpit Image courtesy of IRS ss s rs 04 es Ground station of the IRS simulator Image courtesy of IRS Schematic of KURS operating modes Functional schematic of the motion control system SUD View SUMING cg ea ve ne rc AE SOR Se ww a Main view and b Soyuz systems view of MFD a Off display and b long test display of KURS LIST OF FIGURES 4 6 a Search display and b Frequency picker subview of KURS 39 4 7 a SNC display and b lock on display of KURS 40 4 8 a Approach display and b docking port subview of KURS 40 4 9 Docking ports on the implemented ISS model 41 4 10 a Flyaround display and b Final approach display of KURS 42 5 1 a Format 43 Rendezvous b format 44 Final Approach both ee ee ee Se ee ee dern Ar ee ee ae 47 vi List of Tables 2 1 Soyuz TMA spacecraft specifications 3 2222202
2. One option would also be to implement a model of the onboard computer including its state vector propagation This propagation could be implemented in the simulator as an actual integration of the state vector Another maybe simpler approach would be to mo del the propagation by taking the actual correct state vector and randomly tamper with the values to simulate the integration errors Thus the relative motion parameters provided from the onboard computer would differ from those provided by the KURS model In this way the importance of a Kalman filter could be demonstrated to the students The Kalman filter itself can be implmented as an algorithm slowly decreasing the scope of how much the correct state vector is tempered with An additional feature would be procedures concerning the mechanical docking Even though the single steps of the mechanical docking process cannot be implemented in the simulator due to software restrictions the leak checks following the docking for example could be modelled and included in the procedures In order to be able to perform a fully automated docking the motion control system and its onboard computer need to be expanded So far the rendezvous burns have to be per formed manually or can are pre set in the scenario file For an automated docking the motion control system needs to determine the desired interception point and the resul ting maneuver time to meet up with the station The maneuver time is
3. All in all object oriented programming offers an easy way to enhance and reuse existing programs Due to the application of the messaging system the connection between a service request sending of a message and the method executable part of the program only happens during runtime which makes this a very dynamic programming paradigm 25 3 Method and tools Objects are easy to extend and specialize using additional attributes and methods which only lead to a larger interface However extended objects still match the old interface which makes extended objects easy to implement 3 2 Introduction to C The C programming language development started in the Bell Labs in Murray New Jersey in 1979 and aimed at extending the C programming language by adding object orientation It is a statically typed compiled general purpose case sensitive free form programming language Note that just because a program is written in C this does not automatically imply object orientation C supports procedural object oriented and generic programming For the Orbiter space flight simulator the C language holds many advantages 6 It offers a simple and safe usage and a high reusability It enables easy to maintain and well written code which makes the simulator easy to extend and enhance without great expense Additionally C is a compiled language meaning that programs can be dis tributed to people who do not need to have the respec
4. the time between launch and start of rendezvous varies as well as the time between start of rendezvous and docking 13 2 Description of the modelling problem Soyuz Insertion Timeline Time 11 58 min __ 2 38 min 4 48 min 8 48 min j 1 7492 mis 208 wi 3809 m s o 3 Stage Cut off 176 km v4 amp j 2 d Stage Separation ee Soyuz Separation amp 3 Stage Ignition 85 km Escape tower Orbital Phase 6 amp launch shroud jettison bPhasing Phase orbit until required phase angle 1560 h s then initiate transfer orbit bRendezvous Phase bFar Phase P starts as soon as BZWK 41 5 km FA begins integrating state vector N PA st A Near Phase y D 1 Stage Separation starts when Soyuz is 400 m away from the Station Lift off3 5 7 9 2 59 _ es Og k f i Range 39 km 1109 km 500 km 1640 km Figure 2 13 Soyuz flight phases Image courtesy of ESA Figure 2 14 Phase angle between Soyuz vehicle and ISS 14 2 Description of the modelling problem 2 1 4 2 Timeline Rendezvous usually starts with the beginning of the first orbit on the respective day orbit 33 in the long approach During the phasing phase ground control MCC measures the position and orientation of both the station and the Soyuz spacecraft In the meantime the crew onboard the Soyuz starts preparing the rendezvous phase by setting up the on board computer BZWK selecting the thruster set
5. 12 2 Description of the modelling problem Figure 2 12 Soyuz docking interface Image courtesy of NASA 2 1 4 Soyuz rendezvous and docking sequence 2 1 4 1 Overview After the Soyuz vehicle is launched on board the Soyuz rocket from the Baikonour Cos modrome it takes approximately nine minutes until the Soyuz vehicle is separated from the launcher vehicle indicating the end of the insertion phase and the start of the orbital phase see figure 2 13 Depending on the chosen approach method short or long the phasing phase that follows lasts either a few hours or two days The critical parameter is the phase angle This is the angle from the Earth to the ISS to the Soyuz as shown in fi gure 2 14 As the two vehicles have different orbital periods the phase angle changes over time Before initiating the transfer orbit the phase angle has to be exactly such that when the Soyuz vehicle reaches the Station s orbit the Station will be at the same position and hence their phase angle is zero Taking the short approach the phase angle is already comparatively small when the orbital phase starts and it is only allowed to be within a narrow range Taking the long approach the phase angle is not quite as constrained as the two days in the phasing orbit are used to decrease it over a longer period of time However no matter which approach is chosen the rendezvous and docking phase is still identical from a qualitative point of view Only
6. 2 2 Description of KURS antennas 2 2 on none 2 3 Major hardware and components of active ASA and passive PSA docking Mechanist se eee a Eo oa aa EEE a aa e vii 11 Nomenclature BZWK Ooprosom UN POBOH BEIUHCHHTEIIBHLM Komusiekc BIIBK Soyuz digital computer complex DPO menrarezm upwuanuBaHuaA u opuveHtanuu JIIIO Soyuz attitude and approach control thrusters Insertion phase Flight phase that starts with launch and ends with separation from the launcher KDU komOuHupoBaHHad MBnraTtenbHan ycraHoBKa KJLY Combined pro pulsion system Operating mode Current state of radar system depending on the rendezvous progress Orbital phase Flight phase that starts with separation from the launcher and ends with reentry Phasing phase This flight phase is part of the orbital phase and begins as soon as the vehicle is in its desired orbit It ends with the onboard computer propagating the state vector Rendezvous Far phase This flight phase is part of the orbital phase and begins as soon as the onboard computer starts propagating the state vector Rendezvous Near phase This flight phase is part of the orbital phase and starts at a relative distance of 400 m from the station Scenario Initial state of a simulation viii 0 Nomenclature Simpit An artificial word madeup by combining simulator and cockpit It describes a simulator environment which is designed to replicate a vehicle cockpit SKD
7. At the same time the measurement channels for the relative distance and closing rate p and p respectively are activated Once the vehicle receives measurements for p and p the command Lock on is issued Now the vehicle KURS system is able to measure p p Qy and Q Then the onboard computer starts a Kalman filter on the integrated state vector to match it with the measured values and correct its prediction as shown in the block diagram in figure 2 17 Regardless of whether Lock on has already been issued or not the motion control sy stem determines the next burn Veorr Which usually takes place approximately a quarter orbit after the first large engine burn v1 As this is only a small correction burn only the DPO B engines are employed and the vehicle does not have to change its orientation for the burn After the correction burn is completed the vehicle continues along the internal transfer orbit to the offset target At the specific time that the onboard computer has calculated for firing the second burn Ug the vehicle is rotated in the correct attitude and the SKD is fired for the calculated burn duration Afterwards LOS orientation is acquired again The vehicle then continues to the offset target which is still located one kilometer from the station in off plane direction The completion of both of the burns v orr and va marks the time T gt at which the distance to the station is around 60 80 km If by this
8. DPO MI or DPO M2 and closing the hatch to the orbital module They then check the parameters for the pressure tanks as well as the remaining fuel and prepare the propulsion system the optical devices and the hand controllers The onboard computer is activated which sends an automatic signal to pressurize the fuel tanks The crew also activates the accelerometer and the sensors for angular rate Then the crew turns on the monitors on the control panel The next step is the activation of the onboard motion control system SUD which then in turn comman ds the DPO in order for the vehicle to acquire LVLH orientation Once the vehicle is in LVLH the infared sensors are activated which measure Earth s horizon in order to keep the spacecraft at its orientation At To the far phase of the rendezvous starts during which a bi elliptical transfer from the phasing to the final orbit is performed see figure 2 15 From this point on the onboard computer of the vehicle starts integrating the equations of motion in order to determine its current state vector position and velocity as well as the current state vector of the station The calculations are based on measurements from ground control which the ve hicle received shortly before To The crew monitors p p Q and 2 Then the onboard computer calculates the first correction burn ignition time The vehicle is rotated such that the SKD thrust vector points in the direction of the rendezvous b
9. a signal from the station for the first time Lock on mode starts when the vehicle is in LOS orientation and is auto tracking the station and final approach is assumed once the vehicle is pointing towards the docking port instead of the KURS antenna positioned on the far end of the solar array Antenna Description AKRI AKR2 receive the signal Target Acquired measure p and p 2AO measures n and 9 used for LOS orientation retracted before docking AKR3 operates together with 2AO AC 1 measures p p 7 V y Q AC 2 measures bearing angles nn Vy Table 2 2 Description of KURS antennas 10 2 Description of the modelling problem ASFI Antenna Onboard ERBE Measurement Ass nn Filter Receiver of parameters computer 2AO AKRI AKR2 l AKR3 Transmitter Standard frequency generator Built in checkout system Logic unit Power unit Figure 2 10 KURS system overview ASA PSA docking mechanism receiving cone interface sealing mechanism MGS interface sealing mechanism MGS hatch sealing mechanism MGK hatch sealing mechanism MGK electrical connectors electrical connectors spring loaded pushers spring loaded pushers contact sensors contact sensors Table 2 3 Major hardware and components of active ASA and passive PSA docking me chanism 2 1 3 Docking system SSWP The docking and internal transfer system SSWP has the purpose of establishing and ma
10. additional operating modes AP PROACH and FLYAROUND were introduced These extra modes makes it easier to distinguish between parameters that are currently available and those that are not The main difference between this format and the simulator implementation is the lack of diagrams in the simulator The diagram on the left depicts the relationship of p to p along the horizontal axis the relative range is plotted in logarithmic scale and along the vertical axis the rendezvous range rate is plotted On the right hand side there is an indicator for the line of sight angular position relative to the vehicle s local coordinate system Along the upper horizontal axis the mutual roll angle is displayed on the lower horizontal axis the LOS yaw deviation and along the vertical axis the LOS pitch deviation The implementation of these charts was mainly omitted because the view model in the IRS simulator cannot display that many characters However a similar chart as the right one displaying the LOS angles can be reached through the built in Docking instrument from the main view yet this docking view does not display the data of the KURS model Figure 5 1b shows the Final Approach format 44 The crew always has to switch to this format manually as the borderline between rendezvous and final approach is not always obvious The displayed data is very similar to the one in the previous format 43 The major differen
11. an orbital maneuvering engi ne SKD and twenty eight approach and attitude control thrusters DPO Twelve of 2 Description of the modelling problem Figure 2 6 Crew members inside command module reading procedures Image courtesy of ESA nee x ze LVLH Station Orbit Ga Flight Direction ZLVLH We ZLOS Vehicle Orbit A Vehicle Orbit ehicie Orbi a b YLVLH Flight Direction Figure 2 7 Vehicle orienation in space a LVLH b LOS the latter are DPO M small thrusters and sixteen are DPO B large thursters They are supplied from two fully redundant manifolds the first manifold supplies propellant to fourteen of the DPO B and six of the DPO M thrusters DPO MI the second manifold supplies two of the DPO B and six of the DPO M thrusters DPO M2 The small DPO M1 and DPO M2 thrusters are only used for vehicle attitude whereas the large DPO B thrusters are used for both attitude and translation While in orbit the vehicle can be commanded into different orientations The two main orientations are called LVLH Local Vertical Local Horizontal and LOS Line of Sight Both orientations are shown in figure 2 7 LVLH is acquired during phasing and rendez vous When the vehicle starts getting closer to the station LOS is acquired Only in this orientation the main radar antennas can measure all the parameters correctly 2 Description of the modelling problem F ee Station Orbit pea Vehicl
12. axis see figure 2 18 while decreasing the relative distance to p 150 m and targeting the antenna on the station whose signal was used as a target for the Lock on command Once the flyaround is completed the vehicle shortly enters the station keeping mode keeping both the relative velocity p and the angular rates Q and Q at zero KURS then switches to Final Approach mode and shifts from being locked on to the ho ming beacon antenna of the station to the KURS antenna on the selected station docking port As a consequence the vehicle acquires the new LOS orientation A second flyaround is executed this time while keeping the relative distance of 150 m Once the vehicle is ali gned with the desired docking port it performs station keeping again The crew then issues the final approach command and the vehicle approaches the station while maintai ning the LOS orientation relative to the docking port At a relative distance of 40 m the 2AO antenna boom automatically retracts as docking with the antenna still deployed is prohibited due to safety reasons As soon as the probe head touches the cone the motion control system enters the touchdown mode which causes the thrusters to push the ve hicle forward Due to the present microgravity two spacecraft touching each other might lead to the effect of the two vessels pushing themselves away from each other Therefore upon touchdown the thrusters give the Soyuz an extra push
13. c mkarome Koppektupyrommn asurartesib CKJI Soyuz orbital ma neuvering engine SNC curHan Hanmuna nenm CHIL Target Signal Acquisition Vessel An object or class derived from the VESSEL class It is usually a spacecraft e g spaceship satellite station or an aircraft View An object or class derived from the VIEW class Consists of a set of MFD displays depending on the current MFD settings Latin Symbols ch channel number of navigation device f MHz frequency of navigation device S navigation signal strength arbitrary Orbiter units r m distance between signal transmitter and receiver Greek Symbols y deg roll misalignment angle n deg heading attitude Nm deg heading bearing v deg pitch attitude Un deg pitch bearing p m relative range from vehicle to station p m s relative range rate Q deg s line of sight angular rate Acronyms 3D Three Dimensional AP Autopilot API Application Programming Interface ASA Active Docking Assembly 1X BZWK CM DPO EAC ESA EVA GCTC IDE IDS IRS ISS KDU KURS LOS LVLH MCC MFD MGK MGS MSVC MSVS NASA OAPI OM PG PSA SDK SKD SM SNC SSWP SUD XPDR 0 Nomenclature Digital Computer Complex Command Module Approach and Attitude Control Thruster European Astronaut Center European Space Agency Extra Vehicular Activity Gagarin Cosmonaut Training Center Integrated Development Environment Instrument Docking System Institut fiir Raumfahrtsysteme Space
14. cmd cmd commandClass APCMD_TLIMIT cmd local _V 0 15 0 15 0 15 pAP gt ExecuteCommand amp cmd cmd commandClass APCMD_TPOS cmd local _V 0 0 0 0 0 0 pAP gt ExecuteCommand amp cmd 4 3 KURS front end A front end is an interface between the user and the back end In the IRS Soyuz simulator the front end consists of the control panel the periscope screen and the two control sticks Concerning the implemented KURS model however only the MFDs are part of the front end The student pilot can interact with KURS through a series of different views In the real Soyuz spacecraft these views are called format The implemented views in the simulator are not identical to the formats but try to find a balance in the issue described at the beginning of this chapter about how realistic versus how simple the displayed data should be In the Orbiter simulator all MFD views belong to the VIEW class and for each system KDU SUD KURS etc a derived subclass is constructed Each view can have subviews which also belong to the VIEW class Figure 4 3 shows the super and subordinate views of the KURS view It should be noted that one view can actually consist of different displays That is even though there is only a single KURS view different information and data might be shown on the screen depending on the current KURS operating mode The latter is always displayed in the top center of the screen when in the K
15. current vehicle state in the rendezvous and docking sequence KURS has several different operating modes These modes determine for example which parameters are currently evaluated and what actions have to be taken As the KURS system usually acquires these modes in a chronological order from the far phase to near phase to mechanical docking they will be described in the same order in the following Figure 4 1 illustrates the relationship between the different modes The system is desigend such that it is turned on after the rendezvous far phase has started This means that at this point the vehicle has already left its insertion orbit and is in the transfer orbit The rendezvous burns are not calculated by KURS but by the onboard computer BZWK which is part of the motion control system SUD see figure 4 2 The BZWK then in turn commands the KDU system to perform the burns As neither the BZWK nor SUD were part of the present thesis the automatic calculation and execution of the necessary burns is not implemented in the simulator at this point but can be added in the future Until then the burns have to be performed manually When the KURS system is started in the simulator it automatically assumes that all an tennas have been deployed successfully and that the docking probe head is fully extended The KURS system is implemented in the simulator as a C class and the Soyuz OM 29 4 Model and implementation Angular Rate Senso
16. extended latches enters the receiving socket of the PSA When the head enters the socket the latches over come the force of the springs which keep the stops in place The stops prevent the head from backing out of the cone socket To break this connection either the latches need to be retracted or the stops have to be unlocked During an emergency pyrotechnics separate the docking mechanism from the hatch cover and the latter remains in the receiving cone socket The interface sealing mechanism MGS is identical for both the passive and active part Figure 2 12 shows the MGS on the Soyuz vehicle It contains an interface sealing device eight locking mechanisms two rubber seals and a braided cable connection Each locking mechanism has an active and a passive part Both of them consist of hooks The active hooks can be controlled by the interface sealing device the passive hooks are stationary They are mounted such that an active hook on the station is always facing a passive hook on the Soyuz vehicle and vice versa In case of an emergency pyrotechnic devices can open both types of hooks The second mechanical connection is established as the hooks close and the docking rings are drawn together The interface is sealed when the rubber sealing rings are compressed by the docking ring on the PSA This is also called the rubber on metal contact In order to increase the load bearing capacity the crew manually adds several screw clamps
17. framework the free software Orbiter Space Flight Simulator developed by Dr Martin Schweiger is run For the software to include the control of the cockpit and the Soyuz systems so called add ons were implemented at the IRS These add ons consist of approximately 25 000 lines of code A more detailed 19 2 Description of the modelling problem ER Oe Figure 2 19 Soyuz vehicle docked to the International Space Station Image courtesy of NASA 20 2 Description of the modelling problem Figure 2 20 Model of Soyuz capsule at the Space Systems Institute Image courtesy of IRS Figure 2 21 Simulator cockpit Image courtesy of IRS 21 2 Description of the modelling problem Figure 2 22 Ground station of the IRS simulator Image courtesy of IRS description of the Orbiter software can be found in section 2 2 2 More information on the implementation at the IRS can be found in 8 The flight instructors can load different flight scenarios from the ground control station and supervise the practicing student They can also intervene a running simulation to assist the student from outside the cockpit in case of any deviations from the flight plan as well as purposely cause a malfunction in a subsystem of the vehicle 2 2 2 Orbiter space flight simulator Orbiter is a real time 3D space flight simulator for Windows PC developed to simulate space flight using realistic Newtonian physics Its concept is very
18. model 5 4 1 Displays In order to differentiate between reality and model the different MFD displays are cal led either format in the real system or view and display in the IRS simulation In the real system the selection of the different formats can be done both automatically by the BZWK or manually by the crew There are two main formats the crew uses during rendezvous and docking procedures which can be seen in figure 5 1 Figure 5 la shows the rendezvous format 43 which is used for most of the rendezvous phase In the top right corner the roll yaw and pitch angle y n measured by KURS are displayed if available as well as the respective angular rates wy Wy wz In the center the components of the next required burn are displayed with respect to the vehicle s center of mass AV X AVY AV Z In the bottom left the relative range the range rate p p and the LOS angular rates QZ QY are displayed So far these displayed values are similar to the ones implemented in the KURS view It should be noted that not all of these values are available in the real system on any occa sion The roll angle for example is not measured by KURS during the entire rendezvous sequence In reality of course only those values are displayed that were actually measure d calculated In the implementation the calculation of these values is possible throughout the rendezvous phase Therefore the above mentioned
19. number and therefore also the frequency increases the channel number by 100 by 10 and by 1 The buttons on the left decrease the channel number by the respective amount Once the desired frequency has been reached the pilot can use the lt button to return to the previous in this case search view SNC In the SNC mode the display is very similar to the one before in the SEARCH mode see figure 4 7a The current frequency is shown as well as a bar indicating the received signal strength Likewise there is a FRQ button on the right in case the fre quency needs to be changed Additionally the pilot now can also monitor the current line of sight pitch and yaw angles Note that during the SNC mode the vehicle is aligning with the line of sight and therefore the pitch and yaw angles should decrease to zero if the KURS model is working properly LOCK ON During LOCK ON even more flight data is available to the pilot In ad dition to the previous information frequency signal strength LOS pitch and yaw now 38 4 Model and implementation OM SM OM SM a Figure 4 6 a Search display and b Frequency picker subview of KURS also the values for the LOS pitch and yaw rates are available as well as the range and the range rate Just as before the frequency can be adjusted by pressing the FRQ button on the right An example lock on
20. principle is also called information hiding The executing object receives the message and has the corresponding method to respond to it and this is all the client object needs to know An example for this is the communication between the Soyuz OM and the KURS system When the OM wants to know the LOS angles it asks KURS to compute them and KURS provides the desired answer The OM only knows that KURS has a method to calculate those angles and it knows what information is required by KURS to do so It does not know however what particular calculations are performed Another important principle of object oriented programming is classification and inheri tance A class defines all the methods and properties which all its objects have in com mon Classes can be organized hierarchically Superior classes only own those properties that the subsidiary classes objects have in common Subsidiary classes inherit properties and methods from the superior classes Those properties and methods only need to be defined once for the superior class However inherited methods can be further adjusted and defined in more detail in the respective class In Orbiter for example the OM SM and CM are modelled as sub classes of the VESSEL3 class which is itself derived from the VESSEL class Thus the OM SM and CM inherit all the methods and properties of the superior VESSEL class and in addition they each have their own specialized properties
21. similar to traditional flight simulator softwares however without being limited to atmospheric flight Orbiter was first released in November 2000 and its latest version was launched in August 2010 Originally the software was developed by Dr Martin Schweiger a senior research fel low at the University College London who was unsatisfied with space flight simulators lacking in realistic physics based flight models It is written in C and uses DirectX for 3D rendering In Orbiter the user can experience manned and unmanned space flight missions from a pilot s point of view This includes all phases of a mission Launch orbital insertion ren dezvous with space stations deploy and recapture of satellites reentry and landing on a planetary surface However there are no predefined missions to accomplish or opponents to be defeated Moreover Orbiter is about learning what is involved in real space flight What do you need to know when you want to launch into a certain orbit What is im portant when trying to rendezvous with a space station Or what are the difficulties when 22 2 Description of the modelling problem flying to another planet The Orbiter software itself is basically just a skeleton that defines the physcial model Included in the core software are a few spacecraft and most of the bodies in our solar system Even though the program source code is not published in return there is an ex tensive Application Programming
22. the time the ISS needs from the maneuver starting point to the interception point From there the resulting transfer orbits of the bi elliptic transfer can be calculated Finally special KURS training scenarios should be developed for the Soyuz Rendezvous and Docking Seminar This would offer the students training environments in which they 49 6 Summary conclusions and outlook can get to know the KURS system and its operating modes as well as familiarize themsel ves with the according procedures Within the present thesis only one exemplary scenario was developed to demonstrated the full capabilities of the KURS system However the development of such scenarios ranging from the orbit insertion to docking is complicated as so far there is no automated calculation of the required main engine burns 50 References 1 D Churkin Personal communication 2013 Astronaut Training Division EAC E SA 2 S Fasoulas Personal communication 2013 Professor at Space Systems Institute 3 A Fink and M Schmitz Soyuz rendevous and docking simulator training Univer sity Lecture Notes 2013 University of Stuttgart 4 Gagarin Russian State Scientific Research Testing Center for Cosmonaut Training Soyuz TMA Crew Operations Manual 2006 5 J Liberty Teach Yourself C in 21 days Sams Publishing Indianapolis Indiana 2001 6 D Louis C C Die praktische Referenz Markt Technik Verlag Munich Germa ny 2007
23. time KURS has not generated the command Lock on a switch is made to the alternate system at Ta 2 min That is if KURS 1 was runnning so far it is switched to KURS 2 if this one is functional At at relative distance of p 15 km a short test on the hot KURS system is performed in order to prevent any errors in relative range measurements during the close approach Finally the onboard computer calculates the firing time for the third engine burn v3 This rendezvous burn which cancels out all relative velocity between the vehicle and the target actually consists of two parts During the first part the vehicle is rotated almost by 180 and the SKD engine is used to rapidly decrease the relative velocity between the two vehicles The offset target is first reduced to a distance of 750 m from the station then to 300 m The second part of v3 itself again consists of several smaller burns of the DPO engines The completion of the third engine burn also marks the end of the far phase of 17 2 Description of the modelling problem Flight Direction Figure 2 18 Near phase of rendezvous the rendezvous In order to transition to the near phase certain requirements need to be fulfilled The relative distance p has to be less than 400 m the relative velocity p less than 2 m s and the relative angular rate has to be smaller than 0 3 2 The vehicle then performs a flyaround to align the vehicle axis with the station
24. transmitter signal is lost While the test is performed no KURS data is generated and therefore not available for the crew to monitor 4 2 7 APPROACH mode The APPROACH mode is acquired once the vehicle is within 400 m of the target The start of this mode also marks the beginning of the rendezvous near phase Each time step as in the previous mode both the received signal strength and the line of sight attitude are verified and if necessary the KURS model switches back to SEARCH or SNC respectively During the APPROACH mode the vehicle slowly acquires a station keeping position facing the XPDR antenna mounted on the solar array of the Zvesda module at a distance of 150 m This is achieved by using the motion control system again First the maximum 33 4 Model and implementation relative velocity is set to 2 m s in all directions Second SUD is instructed to acquire the station keeping position AP_COMMAND cmd cmd commandClass APCMD_TLIMIT cmd local _V 2 0 2 0 2 0 pAP gt ExecuteCommand amp cmd cmd commandClass APCMD_TPOS cmd local vRefApproach pAP gt ExecuteCommand amp cmd The exact location of the XPDR signal source on the ISS is not known in the Orbiter simulator Therefore the coordinates of this position are predefined in the KURS model vRefApproach with respect to the center of gravity of the target and so far only represent the correct antenna position w
25. 1 2 Approach methods and organization 204 2 Description of the modelling problem 2 1 Soyuz radar and docking systems A short introduction ALI Soyuz TMA vehicle o a ae wd ey aw OS Hes 2 1 2 Radar system KURS 2 26426 24 su 2 8 BEY ESE nn 213 Docking system SSWP 2 2 suu sacros eee ee ana 2 1 4 Soyuz rendezvous and docking sequence SAAL API oe a Se ar EE Rae SE SOY Ses 2 142 Timeline ac eek saw wu Bar sad RS 2 2 Soyuz simulator at the Space Systems Institute 2 2 1 Soyuz simulator facilities 22 sa ss as Bar kan 222 Orbiter space flight simulator 2 4 de ae Ha a was 3 Method and tools 3 1 Object oriented programming 000 3 2 Introduction to C BREESE KG ER EES RERE PES HEA 29 Frogamming tool cc ds chk ae ew wo a re SEA 4 Model and implementation BA ee fo cls oe BEERS RE OEE SEE ORE SEK SESE RS SEG 42 KURS backend oc 2 Ka 2 aa a an a ee a 121 SPF mode o oo bk SS 2 bw oe bBo oS ee eS 422 LONG TEST mode 24644444 24445 4 oe HESS ill ii vi vii viii 4 2 3 SEARCH mode 222 424 SNC mode 2 2 22220 nn 4 2 5 LOCK ON mode 2 22 2 22 nn 42 6 SHORT TEST mode 22 22 22 4 2 7 APPROACH mode 2 22 222 nn 4 2 3 FLYAROUND mode 4 2 9 FINAL APPROACH mode 4 3 KURS frontend 2 esa csa 6 ed Se ee a we ws 44 Procedures ss
26. 7 M Schmitz RTT Wiki gt Soyuz Simulator URL http phobos irs uni stuttgart de wiki mediawiki index php5 Simulator 8 M Schmitz A simpit framework based on the orbiter space simulator and imple mentation of a soyuz style simpit Studienarbeit 2010 Sapce Systems Institute University of Stuttgart 9 M Schweiger Orbiter Scenario Editor Orbiter 2010 Edition SDK 2006 10 M Schweiger Orbiter Programmer s Guide Orbiter 2010 Edition SDK 2009 11 M Schweiger Orbiter API Reference Manual Orbiter 2010 Edition SDK 2010 12 M Schweiger Orbiter User Manual Spaceflight Simulator Orbiter 2010 Edition SDK 2010 13 M Schweiger Orbiter Spaceflight Simulator July 2013 URL http orbit medphys ucl ac uk index html 51
27. Das Institut f r Raumfahrtsysteme an der Universit t Stuttgart bietet den Studierenden die einzigartige M glichkeit ein Modell des russischen Soyuz Raumschiffs im instituts eigenen Soyuz Simulator zu fliegen Im Rahmen des Soyuz Rendezvous and Docking Seminars welches jedes Jahr im Sommersemster statt findet erhalten die Teilnehmer zu n chst eine theoretische Einf hrung bevor es dann zu den eigentlichen Flugstunden geht Das Ziel der vorliegenden Arbeit ist es sowohl die Komplexit t als auch die Realit ts n he des Simulators zu erh hen und dabei die ersten n tigen Schritte f r ein vollautoma tisches Rendezvous und Docking zu entwickeln Der Schwerpunkt liegt hierbei auf der Implementierung des Radar Systems KURS Bei der Entwicklung des Modells muss die richtige Balance zwischen Realit tsn he und einfacher Bedienung f r unerfahrene Piloten wie die teilnehmenden Luft und Raumfahrtstudenten gefunden werden Die daraus ent stehenden Unterschiede zwischen der Implementierung und dem realen System k nnen sowohl Vereinfachungen als auch zus tzliche Optionen im Modell sein Dar ber hinaus wurde ein Entwurf der sogenannten Procedures d h Verfahrensanweisungen f r die Nutzung der Systeme erweitert und f r die neu hinzu gekommenen Systeme weiter ent wickelt ii Contents Abstract Kurzzusammenfassung List of Figures List of Tables Nomenclature 1 Introduction 1 1 Motivation and objectives 2 22 22 more
28. Interface APD which allows users to contribute to the software by creating so called add ons A multitude of such add ons has been developed by the Orbiter community and is largely available on the web There are additional space craft celestial bodies enhanced instruments etc The Soyuz and ISS models used at the IRS and among others also further developed as part of the present thesis are basically also add ons to the core software 23 Chapter 3 Method and tools 3 1 Object oriented programming The simulator framework i e the Orbiter space flight simulator is written in the object oriented programming language C The following section aims at giving a short in troduction to both the object oriented programming paradigm and the C programming language in order to gain a better understanding of the underlying programming concepts of the IRS simulator and the advantages they bring about Different approaches to programming have developed over time and the resulting lan guages are defined by differentiating between paradigms There are four main paradigms 5D imperative functional object oriented and logic programming Different program ming paradigms use different ways to model the information and how it is processed and they have different concepts on how information and processing interact Some languages are designed to support only one particular paradigm while other languages can support multiple paradigms As the O
29. Modelling of Soyuz Docking and Radar Systems for Implementation in the IRS Simulator Modellierung des Docking und Radarsystems f r Soyuz Raumschiffe im Simulator des IRS Diplomarbeit von cand aer Karin Schlottke IRS 13 S 118 Betreuer Prof Dr Ing Stefanos Fasoulas Dipl Ing Manuel Schmitz Institut f r Raumfahrtsysteme Universit t Stuttgart Dezember 2013 Abstract The Space Systems Institute at the University of Stuttgart offers its students the unique possibility of flying a model Russian Soyuz spacecraft in the institute s own Soyuz si mulator Within the Soyuz Rendezvous and Docking Seminar which takes place each summer semester the participating students first have a few theoretical lectures then the actual flight training begins The goal of the present thesis is to increase both the com plexity and the realism of the simulator and develop the first steps for a fully automated rendezvous and docking Focus is put on the implementation of the radar system KURS During the design of the model a trade off often takes place between being realistic and being simple enough for unexperienced pilots such as the training aerospace students This leads to differences between the implementation and the actual systems both by omitting details in the model and by adding extra features Additionally an existing draft of flight procedures is enhanced and adapted to include the newly implemented systems Kurzzusammenfassung
30. Propulsion Power Optics Guidance Generic Orbiter instrument L IRS instrument view E RE EEN ine er Frequency Docking Port Newly implemented view i Picker Selector B L Figure 4 3 View structure MODE SELECT a b Figure 4 4 a Main view and b Soyuz systems view of MFD 37 4 Model and implementation OM SM LONGTEST Figure 4 5 a Off display and b long test display of KURS is to turn it off using the OFF button Otherwise no data is displayed An example is shown in figure 4 5b SEARCH While the KURS model is in SEARCH mode the user can see the current frequency of the navigation device and how good the reception of the signal is The green bar visualizes the received signal strength If it is above the yellow line the vehicle is in range of the transmitter In case the pilot needs to tune the navigation device to a different frequency he can press the FRQ button in order to reach the frequency picker subview depicted in figure 4 6b In this view the current frequency and channel number of the vehicle s navigation device are displayed In the Orbiter simulator each navigation device has channels ranging from 0 to 639 To convert a channel number ch into a frequency use 11 f 108 0 0 05 ch MHz 4 2 The buttons on the left and right can be used to change the channel
31. Systems Institute International Space Station Combined Propulsion System Radio Technical Rendezvous System Line Of Sight Local Vertical Local Horizontal Mission Control Center Multi Function Display Hatch Sealing Mechanism Interface Sealing Mechanism Microsoft Visual C Microsoft Visual Studio National Aeronautics and Space Administration Orbiter API Orbital Module Personal Computer Passive Docking Assembly Software Development Kit Orbital Maneuvering Engine Service Module Target Signal Acquisition Docking and Internal Transfer System Motion Control System Transponder Chapter 1 Introduction 1 1 Motivation and objectives The Space Systems Institute IRS at the University of Stuttgart is the largest European research institution in various areas of aerospace science The institute has a large variety of test stands and laboratories which are used for both research and teaching One of these facilities is the IRS Soyuz simulator which includes a simulation cockpit simpit resembling the actual Soyuz spacecraft The simulator is used as part of the Soyuz Rendezvous and Docking Seminar which con sists of a theoretical and a practical part In the theoretical part students learn about the International Space Station ISS and its docking ports the rendezvous and docking ma neuvers of the Soyuz vehicle its modules control systems and docking mechanism and how all of this is modelled in the simulator Additional
32. URS view There is one main view as shown in figure 4 4a through which all implemented instruments of the Orbiter simulator can be accessed This is also the view the MFD turns to when pressing the SEL button in the bottom center After selecting Soyuz Systems the user will be able to choose one of the implemented Soyuz systems This view is shown in figure 4 4b In order to be consistent with the previous section on the KURS back end the different displays will be explained in chronological order in the following OFF While KURS is still turned off selecting the KURS view from the main menu leads to the screen shown in figure 4 5a There are only two buttons carrying a label ON and lt The latter is a built in default button and is inherited from the VIEW class It will always lead the user to the superordinate view e g when pressing this button while figure 4 5a is displayed it will lead back to the main view The ON button will activate the modelled KURS system During all other modes the same button will be labelled OFF and will deactivate the KURS system at any given point LONG TEST During the long system test the pilot only receives information about how far the test has proceeded so far via a bar The only way he can interact with the system 36 4 Model and implementation Main VOR Alien Syne COM Radiomps Soyuz VTOL Planes Orbit NAV Panel Systems KDU SEP OVP SUD
33. activated and antenna ASFI is activated and connected to the receiver and transmitter Now ASFI measures the angles 7 and The navigation control and guidance system SUD now uses KURS data for attitude control to keep the vehicle in 15 2 Description of the modelling problem Veorr I I I I I L Parking Orbit Station Orbit N intermediate Transfer Orbit g Incident Trajectory Figure 2 15 Far phase of rendezvous DO EEEE E E E EEEE gt target offset 1 km I I DO BREI IE REN EAEN ARIEN gt target offset 750m I projected Soyuz I trajectories I I I DO PESPEPEPRFLLFEFFELFFPFFCPEPFPEFERR PEERTLTFESFEPFFRFEER gt target offset 300 m I off plane direction orbital a m nri a LU LIDL flight direction Figure 2 16 Target offset during rendezvous phase 16 2 Description of the modelling problem initial state vector quce integrated state vector quzwx measured state vector qkurs P P P p p Qy Qy Qy Q Q Q source MCC source BZWK source KURS corrected state vector qkar P p QT Q source Kalman filter Kalman filter Aq Ipzwe eunsl Figure 2 17 Block diagram of Kalman filter and its parameters LOS orientation instead of predictions from the onboard computer The measured angles correspond to remaining misalignments which SUD needs to correct
34. al functions Of course during real astronaut training preparing for malfunctions is what most of the training is about However in the IRS simulator the training is more about getting to know the system in general without worrying about malfunctions In addition the present project only implemented that part of the automated docking pro cess that is provided by the KURS radar system and takes place in proximity of the station However what is beyond the scope of this thesis is that part of the motion control system calculating and executing the required rendezvous and correction burns to get the Soyuz vehicle from its phasing orbit to the station At this point of time a fully automated ren dezvous and docking is not yet possible Only when the vehicle is within 400 m of the station the implemented motion control system takes over and docks the vehicle automa tically Approaching the station up to this distance so far has to be achieved manually 43 5 Results Comparison of reality and model 5 2 KURS antennas and electronics In the design process of the hardware component models not all components are modelled as separate objects in the implemented KURS system First of all the different KURS antennas on the Soyuz vehicle are not each modelled as separate objects Moreover only a single built in navigation device of the Orbiter simulator is used No differentiation is made between which antenna currently receives a signal or measu
35. alanced solution to attain a simple yet realistic implementation Usually the implementation starts off as a rough representation of reality and gets more realistic and refined over multiple develop ment cycles Very often decisions have to be made on prioritizing some systems or their components over others Within the present thesis these decisions included for example the modelling of the KURS antennas A separate class was initialized for the KURS system itself but its single antennas were not implemented as extra objects The IRS simulator holds an additional concept which has to be kept in mind when de veloping models That is the fact that the simulator is not intended to train and prepare astronauts for an actual space mission Instead it aims at giving aerospace students an opportunity to get a first hand impression of what flying a spacecraft feels like except without microgravity of course In this way the students have the possibility to receive a practical experience for example of the consequences of a diminishing drag while per forming attitude control In addition they also get a deeper insight in orbital mechanics when performing rendezvous maneuvers Taking the above into account did not just result for example in leaving out malfunctions in order to keep the vehicle handling simple Indeed some extra features were added to the implemented model for the training to be engineers It is possible in the IRS simulator t
36. and the two vehicles finally dock As soon as the probe head is captured by the station socket the command capture is generated KURS shuts down and the motion control system enters the free drift 18 2 Description of the modelling problem mode This prevents the thrusters from trying to correct the vehicle attitude while the probe head gets retracted Figure 2 19 shows the Soyuz vehicle and the ISS in the docked configuration Twenty minutes after the vehicle and station docking mechanisms engage the motion control system is automatically deactivated The crew then performs a series of leak checks before they are finally able to open the hatch which connects them to the station where they are usually greeted by the current crew of the station 2 2 Soyuz simulator at the Space Systems Institute 2 2 1 Soyuz simulator facilities The project Soyuz simulator at the Space Systems Institute started in 2007 under the di rection of Prof Ernst Messerschmid who is a former astronaut and was in space in 1985 The very first version of the simulator consisted of two off the shelf personal computers and control sticks which were directly purchased from the Gagarin Cosmonaut Training Center GCTC in Russia In summer 2008 the first training seminar for students had an overwhelming response and over the course of the past years the simulator has been upgraded step by step Today the simulator includes a model of the Soyuz caps
37. angles which now also inlcude the measure ment of the roll misalignment Note that now the line of sight has changed and extends from the Soyuz docking port to the selected docking port on the station Additionally the bearing angles are displayed These are the LOS angles as seen from the station In other words the LOS angles measured by Soyuz represent the orientation of the vehicle in reference to the selected station docking port whereas the bearing angles represent the translational position with respect to the latter Just like before the range and range rate 39 4 Model and implementation Figure 4 7 a SNC display and b lock on display of KURS a b Figure 4 8 a Approach display and b docking port subview of KURS 40 4 Model and implementation Figure 4 9 Docking ports on the implemented ISS model are also displayed As the vehicle is now fairly close to the station there is no need to display the current frequency or received signal strength of the navigation device as the Soyuz should not be moving out of its range Once the station keeping position in front of the docking port has been acquired an additional line appears on the display saying Start FINAL approach Figure 4 10a shows the display in this configuration By pressing the EXE button the pilot commands the Soyuz to star
38. ces are that there are no more AV parameters in the center and that the right chart displaying the LOS angles has disappeared as well The KURS angles that used to be displayed at the top right have disappeared too Instead additional KURS data is now displayed on the right hand side What is new is the display of the bearing angles ny and vy the range and range rate p and p and the LOS rates NZ and QY The pilots now have the possibility to compare the calculated relative motion paramters in the bottom left to the ones provided by KURS in the lower right As the implemented KURS model does not differentiate between data received from 46 5 Results Comparison of reality and model HH HET b Figure 5 1 a Format 43 Rendezvous b format 44 Final Approach both from 4 KURS antennas and data calculated by the onboard computer there is no need to dis play the range the range rate and the LOS angular rates twice in the simulator 47 Chapter 6 Summary conclusions and outlook 6 1 Summary and conclusions The goal of this thesis was to implement a realistic model of the Soyuz spacecraft s radar and docking systems in the IRS Soyuz simulator In order to obtain a deeper insight into the real systems the present study was carried out in collaboration with EAC ESA where the author spent four weeks at their facilities in Cologne When modelling real systems it is always important to find a well b
39. ction GetDockParams which is part of the Orbiter API Then the cross product of both of these vectors is calculated If the vehicle was perfectly aligned with the docking port the result would be zero However there are several control loops involved in the simulator which will always lead to a residual error Therefore in the implemented model the flyaround is considered complete when the result of the cross product is less than 0 3 and the relative velocity is less than 0 3 m s in all directions Finally KURS waits for a user command to switch into the FINAL APPROACH mode 4 2 9 FINAL APPROACH mode In the FINAL APPROACH mode the received signal strength of the IDS antenna is verified in every time step The implemented KURS model commands the SUD imple mentation to stay aligned with the docking port and adds the constraint that vehicle s rotation should also be aligned with the target Then the maximum relative velocity is set to 0 15 m s in all directions 1 Finally the command is issued to acquire the docked position or basically to move the vehicle to the origin of the port s coordinate system AP_COMMAND cmd cmd commandClass APCMD_ALIGN cmd local _V 0 0 0 0 1 0 cmd target APDIR_REFZ pAP gt ExecuteCommand amp cmd cmd commandClass APCMD_CONSTRAINT cma Locat _V 1 0 0 0 0 0 cmd target APDIR_REFY 35 4 Model and implementation pAP gt ExecuteCommand amp
40. display is shown in figure 4 7b SHORT TEST As the pilot cannot interact with the KURS system while it is performing the short system test except to turn it off the display looks exactly as during the long test at the beginning APPROACH The information available during the APPROACH mode is only slightly different from the LOCK ON mode see figure 4 8a There are only two differences First only the LOS rates are available now but not the actual values which should be very small anyway Second there is an additional button on the right labelled TGT This button leads the docking port selector Here all docking port numbers and their cor responding IDS signal frequency of the target vessel are displayed Figure 4 8b shows a list of the available docking ports of the ISS and figure 4 9 shows a screenshot of the im plemented ISS model with the respective docking ports With the up and dwn buttons on the right the pilot can switch between ports The SEL button on the left selects the port currently displayed in yellow Upon selection the view automatically switches to the next display of the KURS view The docking port selection can be performed any time during the approach even before the station keeping position is acquired The Soyuz will then immediately start the flyaround FLYAROUND While the vehicle is performing the flyaround to the selected docking port the pilot can monitor the line of sight
41. e Orbit a b Figure 2 8 Measured relative motion parameters a range p and radial closing rate p b heading attitude n pitch attitude v and line of sight angular rates Q and 2 1 2 Radar system KURS The radio technical rendezvous system KURS measures relative motion parameters bet ween the Soyuz vehicle and the station during rendezvous docking and re docking thus enabling automated rendezvous and docking to the station The measured parameters are depicted in figure 2 8 and listed below e range p e heading bearing nn e radial closing rate p e pitch bearing Jy e heading attitude 7 e roll misalignment angle y e pitch attitude V e line of sight angular rate Q The heading and pitch bearing nu and vy determine the chaser Soyuz position in the target station coordinate system This means they are the same angles as in figure 2 8b except with Soyuz and ISS positions swapped The roll misalignment angle y is the relati ve roll angle between the station s docking port and the vehicle Q is the LOS angular rate vector and consists of Q the pitch attitude rate and 2 the heading attitude rate The KURS system consists of a total of five antennas see table 2 2 which are mounted on the orbital and on the service module Figure 2 9 highlights the antennas on the vehicle Depending on the vehicle orientation with respect to the station the operating range of the KURS system changes When both the vehicle and
42. e more relevant interesting system for the aerospace engineering students participating in the Soyuz Seminar to be adressed in this time constraint thesis A general concern while performing the implementation of the systems is the question how close the model should resemble the real system On the one hand the simulator aims at providing the students with a realistic environment to experience and understand the challenges and tasks of a pilot as close to reality as possible On the other hand the training students should not be overwhelmed by the complexity of the simulator and they should be able to acquire appropriate spacecraft operation skills over the short training period of a few weeks Finding the right balance between being simple and being realistic and between what is feasible and what is reasonable is one of the many challenges of the present thesis 28 4 Model and implementation Nominal change of operating mode KURS deactivation via pilot Loss of navigation signal Serene Loss of LOS attitude Me ete a APPROACH Figure 4 1 Schematic of KURS operating modes 4 2 KURS back end As mentioned above the KURS back end basically consists of everything that the user i e the pilot cannot see or manipulate directly The scope of the back end goes from the modelling of the antenna signal range to the calculation of the relative motion parameters up to the commands sent to the autopilot Depending on the
43. ems First the actual radar and docking systems are explained A closer look is taken at each of their components and their configuration Focus is also put on the function and operation of the systems as well as the course of events during the rendezvous and docking phase Then both systems are modelled and implemented into the IRS Soyuz simulator in a highly simplified version Afterwards the systems are integrated to the already existing guidance system of the simulated Soyuz spacecraft Finally procedures are developed for the operation of the modelled systems and the automated apporoach to the station They can be used by the students participating in the Soyuz Rendezvous and Docking Seminar Chapter 2 Description of the modelling problem 2 1 Soyuz radar and docking systems A short introduc tion 2 1 1 Soyuz TMA vehicle The Soyuz vehicle family is the longest serving manned spacecraft in the world It was originally designed for the Soviet Manned Lunar program by the Korolyov Design Bu reau in the 1960s The spacecraft is launched on the Soyuz rocket from the Baikonur Cosmodrome in Kazakhstan see figure 2 1 and can carry a crew of up to three mem bers Life support can be provided for 30 days without being docked to a station Once docked it can stay at the station up to 180 days At least one Soyuz spacecraft is docked to the International Space Station at all times as an emergency escape craft The first unmanned Soyuz was
44. f the received signal transmitter Next it calculates the position of the CM s center of gravity in global coordinates via the function GetGlobalPos This function determines the position of a vessel s center of gravity and is also part of the OAPI By subtracting the two positions the BZWK line of sight is obtained and can be rotated into local Soyuz coordinates Now the LOS angles can be determined The LOS vector is projected into the vehicle s orbital plane and using the scalar product of the projected vector and the vehicle s z axis pointing towards the front of the spacecraft the azimuth angle can be evaluated The elevation angle is determined using the scalar product of the LOS vector and its projection Finally the LOS rates are calculated via the difference of the angles over the previous time step The LOS angles representing measured KURS data are calculated similarly to the BZWK values The only difference is that now instead of the CM s center of gravity the position of the docking port is used The latter can be determined via OAPI function GetDock Handle which returns the position of the docking port in local vessel coordinates 30 4 Model and implementation The KURS data set also contains the pitch and heading bearing angles ny and Vy A coordinate system is created for the station s docking port and then the line of sight vector is expressed with respect to these coordinates Afterwards the pitch and headin
45. g bearing angles can be calculated in the same way as the previous angles Finally the range and range rate are also calculated These values are once again calcula ted with respect to the CM s center of gravity After making sure a signal is received from the correct transmitter the line of sight vector to the station is calculated in local vessel coordinates The range p is simply the length of this vector The range rate p can be de termined using the OAPI function GetRelative Vel which calculates the relative velocity vector between two vessels As this vector is with respect to the global reference frame and contains the relative velocity in all three directions the actual range rate is the result of the scalar product of the relative velocity and the line of sight vector 4 2 1 OFF mode By default KURS is in the OFF mode No parameters are calculated and no commands issued This mode can be acquired while being in any other operating mode This means that the KURS system can be deactivated throughout the entire rendezvous and docking sequence see the black dashed line in figure 4 1 4 2 2 LONG TEST mode Once the system is activated it automatically goes into the LONG TEST mode During this mode a long system check of the two KURS systems is simulated by simply staying in this mode for a predefined amount of time 150 s 2 without actually doing anything For this purpose the SIMTIMER class was de
46. hen docking to the ISS When approaching another space station of course where the KURS antenna is positioned somewhere else these coordi nates might be different During the whole process the motion control system keeps the vehicle pointed at the station s center of gravity At some point during the APPROACH mode the KURS model expects a docking port selection from the user As soon as a port has been selected the system switches to the FLYAROUND mode even if the station keeping position in front of the solar array has not been reached yet 4 2 8 FLYAROUND mode During the FLYAROUND mode the vehicle is moved from its station keeping position in front of the XPDR antenna to a station keeping position in front of the selected docking port at a distance of 150 m As soon as a docking port is selected the OM s primary navigation device is tuned to the IDS signal of the respective port instead of the XPDR frequency of the station The KURS model checks whether an IDS signal is recieved and analogous to the XPDR signal the signal strength is verified Just as with the XPDR signal a hysteresis has been implemented in order to prevent the system of switching back and forth when the vehicle is on the edge of being in range of the transmitter Next the selected docking port is delivered to the implemented motion control system as the target docking port instead of the center of gravity of the station The KURS model the
47. in taining a connection between the Soyuz vehicle and the Russian segment of the station This connection involves not only a pressurized passageway between the two vehicles but it also establishes connections of common electrical and hydraulic lines command and control and atmosphere exchange The system consists of an active docking assem bly ASA and passive docking assembly PSA This type of docking system is called the probe and cone or Classic type and is shown in figure 2 11 The ASA is located on the Soyuz orbital module the PSA is mounted on the station Table 2 1 lists all major hardware and components of both ASA and PSA The docking mechanism is attached to the transfer hatch of the Soyuz vehicle It corrects inital vehicle misalignments and dampens the impact energy The probe can be extended and retracted by the docking mechanism drive The head of the front probe has four lat ches which are extended and retracted by the latch drive The moment when the probe head first touches the cone is called touchdown Once the probe head latches are locked 11 2 Description of the modelling problem Y med latch receiving cone probe head socket extendable probe Figure 2 11 Docking mechanism and receiving cone design Image courtesy of ESA in the socket the docking mechanism draws both vehicles together and mutually aligns them The first mechanical connection is established once the probe head with
48. in However as mentioned above only one KURS model was implemented and malfunctions are not implemented in general For these re asons the implemented model cannot check any parameters and just has to pause for a given time Another possibility would have been to simply ignore these two test modes Nevertheless these test modes were still desired in the implementation in order to give the students a more realistic experience for example when there is no KURS data available during the short test while being fairly close 15 km to the station Another if yet smaller difference between the mode implementation of the model and the real system occurs at the end of the APPROACH mode In reality the vehicle is aligned with the station s axis in its station keeping position In the implementation however the vehicle acquires the same position but is pointed to the station s center of gravity This is due to the limitations of the IRS motion control system implementation its autopilot respectively In reality the rendezvous far phase begins at 7 with the onboard computer integrating the equations of motions to determine the current state vector of the vehicle This integration leads to some errors in the propagated vector later on which are corrected during the LOCK ON phase using a Kalman filter As the simulator does not propagate the state vector but calculates it again every time step there is no need to correct the state
49. is above the signal strength Sea that would be received at the real system s range r a Both can be done using the OAPI functions GetNavSource and oapiGetNavSignal To prevent the model from switching back and forth when the received signal is just around the threshold a hysteresis factor is implemented Thus a signal is processed as received when the signal strength is slightly above S On the other hand when a signal is currently received it will be processed as lost only when the signal strength is slightly below Speal Summing up this means for the SEARCH mode If a signal is received and its strength is above the required threshold the KURS model switches to the SNC Target Acqui red mode If the KURS model is in any later operating mode and the signal strength drops below the threshold or is lost completely it always returns to the SEARCH mode see red lines in figure 4 1 4 2 4 SNC mode The SNC mode starts as soon as the received XPDR signal is strong enough 1 e the vehicle is in the range of the transmitter This condition is checked for every time step while in SNC mode During this mode the vehicle is rotated until it points towards the received signal source This is achieved using the SUD model its autopilot respectively which is part of the oapiExt the extended OAPI developed at IRS First the SUD model is passed the target vessel the station usi
50. launched in 1966 the first manned mission Soyuz 1 on April 23 1967 Over the course of the years several development steps have been imple mented to constantly improve the vehicle The one currently in use is the sixth generation the Soyuz TMA M However as the IRS simulator is based on the fifth generation the specifications of the so called Soyuz TMA vehicle are described in the following The Soyuz TMA vehicle was first launched in 2002 and had its last descent on April 27 2012 It was used by the Russian Federal Space Agency to carry Russian cosmonauts and also NASA and ESA astronauts to and from the International Space Station Table 2 1 sum marises the spacecraft specifications The spacecraft consists of three parts the orbital module habitation the command mo dule used for reentry and the service module with solar panels attached as shown in figure 2 2 Only the command module is reusable and returns back to Earth with the crew Both orbital and service module are single use only They are jettisoned during the descent phase and burn up in the atmosphere during reentry The orbital module OM is a spheroid pressurized module and is also called the habitation 2 Description of the modelling problem Figure 2 1 Soyuz rocket launch from Baikonour Cosmodrome Image courtesy of NASA Dimensions Length 7 48 m Max diameter 2 72 m Span solar array 10 70 m Total mass 7 2t Crew 3 Launch vehicle Souyz FG Landing S
51. ly stress and human factors in space engineering are discussed 3 Then in the practical part the goal is for the students to learn and experience how to fly and operate a complex space vehicle within a typical mission scenario They employ their motor skills and use their personal audiovisual per ception while being in a stressful situation In this way they gain personal insights and experience realize and improve their audiovisual perception and motor skills and learn how to handle stress and increase their performance So far both the radar and the docking system of the Soyuz spacecraft have been simu lated using the standard routines from the underlying basis software Orbiter The main objective of the present thesis is to increase the complexity and realism of the simulated radar and docking system model in order to achieve a more realistic instrument based rendezvous and docking of the Soyuz to the ISS A second goal is to obtain procedures for the operation of the modelled systems and an automated approach to the station 1 Introduction 1 2 Approach methods and organization As mentioned above this thesis aims at modelling the radar and docking systems of the Soyuz spacecraft as realisticly as possible within the IRS Soyuz simulator This study is conducted in collaboration with the European Astronaut Center EAC in Cologne which belongs to the European Space Agency ESA in order to gain a better understanding of the two syst
52. modelling the Soyuz spacecraft but the code itself is generic and can also be used in other vessels It contains for example an 26 3 Method and tools autopilot AP and a timer for counting down the simulation time More information can be found in 7 All code developing debugging and management is done using Microsoft Visual Studio 2010 MSVS which is an integrated development environment IDE It contains the IDE Microsoft Visual C MSVC which is designed for C programming tasks 27 Chapter 4 Model and implementation 4 1 Overview This chapter describes how the existing simulator code was enhanced in order to imple ment the Soyuz KURS system First the so called back end of KURS is explained The internal parts of the systems the different operating modes etc Second the KURS front end i e the user interface is described The different views on the MFD the information available to the pilot and the decisions he has to make with respect to KURS Finally the procedures are presented These are the checklists telling the pilots for example which parameters they need to monitor and which systems they have to activate or deactivate at what time As stated in chapter 1 originally also the implementation of the internal docking and transfer system was part of the present thesis Throughout the project howe ver it became clear that focus was going to be put on the implementation of the radar system This seemed th
53. n commands the SUD model to acquire the station keeping position 150 m away from the docking port The maximum relative velocity in any direction during the flyaround is set to 1 5 m s FlyArSpeed As an additional constraint the KURS model commands SUD to align the the vehicle s x axis with that of the selected port AP_COMMAND cmd cemd commandClass APCMD_TPOS cmd local _V 0 0 0 0 150 0 4 pAP gt ExecuteCommand amp cmd 34 6 8 10 4 Model and implementation cmd commandClass APCMD_TLIMIT cmd local _V FlyArSpeed FlyArSpeed FlyArSpeed pAP gt ExecuteCommand amp cmd cmd commandClass APCMD_CONSTRAINT cmd local _V 1 0 0 0 0 0 cmd target APDIR_REFY pAP gt ExecuteCommand amp cmd Now that a docking port has been selected the line of sight is considered to go from the Soyuz vehicle to the docking port instead of the center of gravity of the station Hence during the entire maneuver the vehicle is pointed now to the docking port instead of the center of gravity In order to determine the completion of the flyaround the remaining misalignment and the remaining relative velocity are measured First both the current line of sight vector and the approach vector of the docking port are determined The line of sight vector is the difference between the position of the vehicle and the docking port in global coordinates The approach direction can directly be accessed through the fun
54. n rule out inconsistent or unphysical object states Objects are classified depending on their interface and these interfaces can be inherited by subsidiary classes A program can be understood as a system of cooperating objects These objects have a state a life span and they exchange messages with each other While an object is proces sing a received message it can change its own state send messages to other objects or itself create or destroy other objects Objects behave like items in the material world they are said to have an identity An object cannot be present at two places at the same time and it can change its state while still staying the same object Just like a propellant tank can either be full empty or somewhere in between and still stay the same propel lant tank This is also the main difference to mathematical objects like numbers and facts Object oriented programming models the real world as a virtual world Programs try to reflect as far as possible or as necessary that part of reality they are going to treat A central thought of object oriented programming is the separation of the task assignment and the task completion If one object needs a task to be done it will look for another object who is capable of performing the task It then sends a message to the object which has the corresponding method for the task completion The client object is ignorant of the details on how the executing object performs the task This
55. ng the function SetTar getObject SUD also requests a docking port but at this point in the rendezvous phase no docking port has been selected yet However the function provides an extra option for this flight phase in which the center of gravity of the target vessel is chosen instead of a physical docking port Next a command is issued to the SUD implementation to rotate the vehicle until it is pointed at the selected docking port in this case the center of gravi ty At the same time as a secondary constraint SUD is to maintain the vehicle s rotation attitude thus keep its y axis pointing upwards For every time step as always the KURS model evaluates the current azimuth and eleva tion angles and rates of the line of sight As soon as both azimuth and elevation angle are below 5 which means the vehicle is aligned with the station KURS switches to the next mode LOCK ON 32 4 Model and implementation 4 2 5 LOCK ON mode During the LOCK ON mode the Soyuz continues its flight towards the station In rea lity this is usually the mode in which the correction and the second burn take place As mentioned at the beginning of this chapter these burns are neither computed nor com manded by the KURS system and therefore are not implemented within the scope of the present thesis On the other hand however this allows the KURS model in the simula tor to operate fully independent of whether these burns are perfo
56. o saco san pau eae eee eed eee Results Comparison of reality and model 5 1 Generalremarks i gk Nv ea eR ERE EE RS 5 2 KURS antennas and electronics 5 3 KURS operating modes and other software differences 5 4 Crew operations noaoo e SAN Ve ce iu a Kadun Ka ua a Summary conclusions and outlook 6 1 Summary and conclusions 62 Outlook ad a a ae radd a Re Ban ae iv CONTENTS List of Figures 21 22 23 2 4 23 2 6 2 7 2 8 2 9 2 10 21 2 12 213 2 14 2 15 2 16 en 2 18 2 19 2 20 221 2 22 4 1 4 2 4 3 4 4 4 5 Soyuz rocket launch from Baikonour Cosmodrome Image courtesy of Soyuz TMA vehicle with orbital module command module and service module Image courtesy of NASA 2 Cm none Inside view of the orbital module Image courtesy of NASA Command module with landing parachute Image courtesy of NASA Control panel inside the command module Image courtesy of NASA Crew members inside command module reading procedures Image cour Va ee we E E eS ee eee ee we Vehicle orienation in space a LVLH b LOS Measured relative motion parameters a range p and radial closing rate p b heading attitude n pitch attitude and line of sight angular rates Docking mechanism and receiving cone design Image courtesy of ESA Soyuz docking interface Image courtesy of NASA Soyuz flight phases Image courtesy of ESA
57. o select a docking port before performing the flyaround in proximity of the station In reality the docking port is preselected by ground control When choosing the desired docking port in the simulator not only the docking port number is displayed but also 48 6 Summary conclusions and outlook its respective antenna frequency In this way the students see and learn what is behind selecting a docking port It means setting the vehicle s navigational device to a specific frequency Following the received signal will then guide the spacecraft to the desired docking port When it comes to developing the procedures in general the same issues are taken into consideration as when implementing the models Of course procedures can only be writ ten for systems respresented in the simulator In addition it has to be ensured that all of the procedures are manageable by a single person In reality there is a crew of three but in the simulator the students usually practice one at a time 6 2 Outlook The implementation of such a highly complex system such as the radar and docking sy stem not even to mention the Soyuz vehicle in general always leaves room for extensions and improvements The implementation model could be refined with regards to modelling each antenna individually or implementing two seperate electronics sets In general these kind of enhancements will be most interesting if they also involve the implementation of malfunctions
58. rbiter code is mainly object oriented only this paradigm will be explained in more detail hereafter and an elaborate description of the other para digms is omitted Object oriented programming derives its basic principles from real world processes and objects These processes are modelled through acting individuals who perform and assign tasks In object oriented programming those individuals are called objects An object is an entity consisting of a data structure in concert with a definition of related operations All of the used data is distributed among the objects and additionally there are no global operations Each operation directly belongs to an object and can only be engaged by sending a message to the respective object This technique is called encapsulation The variables defined locally for an object are called attributes and the local operations are called methods The description of those local methods is usually done using procedural programming The code also contains procedural parts while at the same time lacking some typical object oriented concepts such as streams 24 3 Method and tools An object has a well defined interface which describes the properties of the object the messages or operators which the object understands and a list of those attributes acces sible from outside the object Ideally attributes can only be accessed through a method and the object has total control over its data This technique ca
59. res a relative motion parameter Instead the implemented model uses the built in navigation device to receive a signal in general Besides as this received signal does not contain any information about the relative motion parameters the latter are determined using built in functions of the Orbiter API The modelling of the different KURS antennas on the Soyuz vehicle is omitted for several reasons As mentioned in chapter 3 1 one principle of object oriented programming is to create objects that resemble reality only as far as necessary It is not the primary goal for the aerospace students training in the simulator to learn about radio signalling but about the rendezvous flight path and the operation of a complex vehicle One argument supporting the modelling of different antennas is that this would allow for the simulation of malfunctions of single antennas However as mentioned above malfunctions are not part of the IRS Soyuz simulator Therefore the modelling of separate KURS antennas and their respective received and transmitted signals was considered unnecessary In the real Soyuz the radar system not only consists of several antennas but also of a set of electronics filter receiver transmitter etc All these electronics were also not modelled in the IRS simulator for very similar reasons as the implementation of separate antennas was omitted The implemented KURS system itself does not contain any other components in general but i
60. rmed manually or not The only thing that matters to KURS is the attitude of the vehicle and its distance closing speed with respect to the target but not the way this position was acquired Just as in the previous modes the KURS model checks whether an XPDR signal is re ceived at a sufficient strength before every time step or else returns to the SEARCH mode Additionally while in the LOCK ON mode KURS also checks whether the line of sight angles are still below the threshold of 5 If this condition fails KURS returns to the SNC mode see the yellow lines in figure 4 1 As the SUD hasn t received any commands otherwise and LOCK ON can only be reached from the SNC mode SUD will keep the Soyuz pointed at the station s center of gravity while getting closer to it At a relative distance of 15 km the KURS model switches from LOCK ON to SHORT TEST mode After the test is completed the system returns to LOCK ON and pro ceeds its approach to the station Once the Soyuz is within 400 m of the station the APPROACH mode is acquired 4 2 6 SHORT TEST mode The short test is performed very similarly to the long test except that it is as in the name shorter Just as in the long test the KURS model uses the SIMTIMER class to count down the duration of the test 75s 2 This test will be performed again should the KURS model have to switch back to the SEARCH mode in case the
61. rs Hand Horizon String ate Controllers Sensors Accelerometer Control Panel Figure 4 2 Functional schematic of the motion control system SUD vessel automatically creates an instance of this class when the simulation is loaded and initialized Before every time step the OM checks the current operating mode of KURS using the built in function of all vessels clbkPreStep from the Orbiter API Depending on the operating mode different commands will be executed by the KURS object Independent of the current operating mode the KURS model always determines the cur rent LOS angles 7 J and Q In reality the angles are either calculated by the BZWK or measured by the KURS system In the implemented simulator model the values repre senting BZWK data are calculated from the CM s center of gravity to the position of the received KURS signal transmitter The real measured KURS data is calculated from the Soyuz KURS antenna to the signal source in the model Additionally the range and range rate p and p respectively are calculated similar to the BZWK data i e from the CM s center of gravity to the target transmitter The calculation of the LOS angles from the BZWK system takes place as follows First the KURS model determines whether a navigation signal is received and whether it is from the correct transmitter type XPDR or IDS Then the model uses the API function oapiGetNavPos to determine the position o
62. s treated as a single object that measures calculates most of the things on its own Besides the real KURS system consists of two of these electronics sets for redundancy So far only one KURS model is implemented in the simulator as a second system would only be interesting for simulating malfunctions If this is desired at a later point of time a second KURS system can be implemented by creating another instance of the KURS class and assigning one boolean parameter indicating which mo del is currently in use and another boolean parameter indicating whether the model is malfunctioning or not 5 3 KURS operating modes and other software differences In reality the KURS system switches directly from the LOCK ON mode to the FINAL APPROACH mode The implemented KURS model has additional operating modes The APPROACH and FLYAROUND modes were added at the end of LOCK on and at the beginning of FINAL APPROACH This decision was made for the sake of convenience in order to simplify the implementation of the different flight phases and the corresponding displays The two test modes LONG TEST and SHORT TEST are basically implemented as 44 5 Results Comparison of reality and model timers where the KURS model just waits for a certain amount of time before proceeding with its operation In reality during the long test both KURS sets are tested and during the short test the hot set is tested aga
63. s usually contain the surveillance of critical parameters like cabin pressure or oxygen levels During the automated docking process to the station the crew members supervise the correct operating sequence by constantly ensuring that all control parameters stay within certain limits and all systems work properly In case the automated docking fails the crew can also dock manually using the hand controllers Figure 2 6 shows crew members inside the command module together with a printed version of the procedures which contains a detailed description of all possible crew tasks and which the crew follows step by step at all times The figure also illustrates how little free space is available in the module The service module SM is the only non pressurized module It contains sytems for ther mal control power supply radio communications radio telemetry as well as instruments for orientation and control In addition to that it also contains the combined propulsion system KDU The module itself has a length of 2 26 m and is 2 15 2 72 m in diameter The solar arrays are also attached to this module They have a total span of 10 6 m and with a surface of 10 m they can produce a power of 1 kW The KDU is a pressure fed propulsion system which uses bi propellant liquid fuel reactive thrusters As propellants an oxidizer nitrogen tetroxide and fuel non symmetrical dimethylhydrazine are used and they are stored separately in different tanks There is
64. t the final approach to the docking port FINAL During the final approach to the docking port fewer relative motion parameters are available to the pilot than before see figure 4 10b Only the roll misalignment is displayed as well as the bearing angles the range and range rate Additionally the pilot receives information about whether the 2AO antenna boom has been retracted or not The retraction is usually takes place automatically Note that docking with the antenna still deployed is prohibited In the bottom of the display it now says Abort FINAL approach In case the pilot notices a malfunction pressing the button EXE will abort the final approach and put the KURS system back into the FLYAROUND mode In this way the motion of the vehicle will be stopped and it will be directed to move back to the station keeping position at 150 m distance The only other option for the pilot to interact with the KURS model at this point is to turn it off 4 4 Model and implementation FLYAROUND a b Figure 4 10 a Flyaround display and b Final approach display of KURS 4 4 Procedures In order to increase the authenticity of the IRS Soyuz simulator flight procedures are developed for the modelled systems The procedure are used in reality to guide the astro nauts through the many highly complex systems of the Soyuz spacecraft In the simulator so far no proced
65. the station are not pointed at each other the range is only 50 km As soon as the vehicle is pointed at the station but the 2 Description of the modelling problem Figure 2 9 KURS antennas on the Soyuz vehicle Image courtesy of NASA station still has an arbitrary orientation the operating range increases to 200 km This is the usual case during rendezvous phase In case both vehicles are pointed at each other the operating range is as high as 400 km When the vehicle is pointing at the station du ring phasing it is actually not pointed at the desired docking port but at either one of the station s KURS antennas XPDR antennas positioned on each far end of the solar panel of the Zvesda module Only when the vehicle is close to the station the LOS orientati on is aiming at the KURS antennas of the selected docking port which are part of the instrument docking system IDS The electronics are made of two identical sets KURS1 and KURS2 They each contain amongst others a filter a receiver a logic unit and an interface exchange unit as shown in figure 2 10 When the system is activated both sets are tested and KURS1 is chosen by default Both crew and ground control can command the KURS system and observe displayed commands There are several operating modes of the KURS system the long test and short test mode which are assumed during the two test phases the SNC mode Target Acquired assu med after KURS has detected
66. tive compiler in order for them to use the program This makes the simulator a portable program where the end user does not have to be a software developer to be able to use it But on the other hand it still enables the user to enhance the program by the so called add ons if he desires to do so How this is done exactly is described in the following section about the Orbiter Software Development Kit SDK 3 3 Programming tools The Orbiter SDK can be downloaded from the same website as the simulator itself 13 It contains the application programming interface API in the form of some libraries code examples a few utilities and useful documentation 12 10 11 The API includes the interface methods a set of functions for getting and setting general simulation parameters in a running Orbiter simulation session These methods can be used by all types of plugin modules and their name always starts with oapi Furthermore the Orbiter API OAPI also contains the properties and methods of the VESSEL class and its two derivatives VESSEL2 and VESSEL3 These classes are the base classes for creating new vessels e g the Soyuz orbital module For creating new multi function display modes developers need the MFD and MFD2 classes which are also part of the API In addition to the API provided by Orbiter there is the so called oapiExt a function library developed at the IRS 7 It was developed for
67. ude of 9km a breaking parachute opens and at 7 5 km altitude the main parachute slows the vehicle down even further see figure 2 4 1 m above the ground the solid propellant breaking engines ignite to ensure a soft landing The command module also serves as the cockpit of the Soyuz vehicle and contains control panels which are depicted in figure 2 5 Additionally it holds life support systems and an independent guidance navigation and control system much simpler than the main one in the service module These systems are used during the return flight to Earth after the module has separated from the service module Moreover it also contains a 2 Description of the modelling problem 1SS014E18790 Figure 2 3 Inside view of the orbital module Image courtesy of NASA Figure 2 4 Command module with landing parachute Image courtesy of NASA 2 Description of the modelling problem Multi function displays MFDs Periscope monitor Translational hand controller Rotational hand controller Figure 2 5 Control panel inside the command module Image courtesy of NASA propulsion system for attitude control during reentry It has a periscope to allow the crew to see the docking target on the station or the Earth below The module is 2 4m long has a diameter of 2 17m and a habitable volume of 3 5m A payload of up to 50kg can be returned to Earth This value increases to 150 kg if only two crew members are present The crew task
68. ule which offers the students a semi realistic cockpit environment and a simplified ground station for the supervision by the flight instructor The capsule is an original sized model of the orbital module of the Soyuz spacecraft and was developed at EAC ESA in Cologne for their own simulator It has a basic diameter of 2 3 m and a height of 2m For an easy access the capsule can be opened in the middle as shown in figure 2 20 Inside the capsule features all the important elements of the cockpit as indicated in fi gure 2 21 First there is the integrated operational panel including two multi function displays MFD and several switches The view through the periscope of the vehicle is simulated on another monitor allowing to see what is in front of the spacecraft For mo tion control around all six degrees of freedom two control sticks are installed The left stick controls all translational movements i e forward backward right left and up down All rotations around the vehicle s three axes i e pitch yaw and roll are controlled by the right stick The crew is seated in three rather narrow seats with the flight engineer on the left the mission specialist on the right and the captain pilot in the center However during the Soyuz Rendezvous and Docking seminar usually only the pilot s seat is occupied Figure 2 22 shows the ground control station with its several personal computers and screens This is where the simulator
69. ures are available to the students Within the present thesis an existing procedures draft was enhanced and especially the procedures for an instrument based rendezvous were developed The simulator procedures try to reproduce the actual ones as close to reality as possible However procedures always need to be adapted to those systems that the training pilot is actually working with Including many items in the pro cedures that do not exist in the simulator only confuses the users and contradicts the point of procedures in general which is to help the pilot with the system usage The developed simulator procedures draft can be found on the DVD accompanying this thesis 42 Chapter 5 Results Comparison of reality and model 5 1 General remarks This chapter provides a comparison of the implemented KURS model and the real Soyuz system The comparison covers a variety of different aspects from the hardware modelling to the differences in the resulting rendezvous sequence up to the differences in the front end i e the MFD simulator views versus the Russian formats Most of the differences can be related back to the general idea that aerospace engineering students will be using the si mulator and not astronauts training for a real mission This often leads to simplifications but can result in some additional features as well as described in the following One major issue that is not implemented in the IRS simulator in general is system m
70. urn Av The SKD then completes the first correction burn and the vehicle returns to LVLH orientation afterwards and continues along the internal transfer orbit For saftey reasons the rendezvous target is offseted by one kilometer in the station s off plane direction see figure 2 16 in order to avoid any possibility of a crash in case the rendezvous phase should fail KURS is activated at T between the first and second burn approximately 800 km from the station After the long test Test D is completed and both set 2 and set 1 tested KURS switches to the normal operating mode The command Omni directional search is issued and antennas AKRI and AKR2 alternately connect to the receiver and transmitter at a frequency of 1 kHz By doing so they can receive signals emitted by the station s KURS antenna and transmit a nonmodulated 3240 or 3245 MHz homing beacon signal in any direction around the Soyuz As soon as one of the antennas receives a reliable signal the command SNC is issued and the search mode is terminated Whichever antenna generated the SNC command stays connected to the transmitter and receiver At the same time the LOS orientation mode and antenna 2AO are activated 2AO measures the heading and pitch angles 7 and and sends them to the control system When the angular misalignment of each angle is less than 5 KURS issues the command Auto tracking As a consequence antennas AKR1 and 2AO are de
71. vector Therefore no Kalman filter model is implemented in the simulator 5 4 Crew operations Most of the differences in crew operations either result from the fact that aerospace en gineering students will be operating the simulator instead of real astronauts Another great deal of variations are a consequence of another previous difference e g in the de termination of the relative motion paramters First the differences in the crew actions are described later the MFD views are compared to the equivalent formats After the KURS system is started and tested it will look for a signal from the station s KURS antennas In reality the KURS antennas on the Soyuz are tuned to pre set frequen cies and the crew cannot change them In the simulator a frequency picker view has been implemented This allows the crew to vary the frequency of the built in navigation device of the vehicle In this way the students can get a better idea of the operation of the radio system Later on during the near phase of the rendezvous the crew has to select a docking port in the simulator In reality the crew does not select the docking port yet they do know which port they are supposed to dock to The actual selection of the docking port is made by ground control 1 However to make the simulator students independent of ground control the docking port selection was implemented as a crew task 45 5 Results Comparison of reality and
72. veloped which enables the system to count down simulation time The LONG TEST mode is always acquired after the OFF mode Even if the test has already been performed before and KURS is deactivated while in another mode the long test will always be performed again upon re activation of the system 4 2 3 SEARCH mode In the SEARCH mode the KURS model checks whether the OM s primary navigation device receives a signal from the ISS XPDR By default each vessel in the Orbiter simu lator has two built in navigation devices Besides the station s XPDR frequency can be set in the scenario configuration file see 9 for more details on how to edit scenarios The KURS model is programmed such that by default the primary navigation device is already tuned to the ISS XPDR frequency However its frequency can still be modified by the pilot 31 4 Model and implementation The transmitter strength in the Orbiter simulator is modelled such that it drops off with the square of distance to the transmitter 11 Geht 4 1 where S is the received signal strength at the distance r So is set by Orbiter to a value such that a receiver will detect a signal strength of 1 when it is just in range of the transmitter The signal range of the station s XPDR predefined by Orbiter is longer than the range of the real system Therefore the implemented model not only checks whether an XPDR signal is received but also if it
73. ystems Parachute retro rockets landing on land Manufacturer RKK Reentry acceleration 5 8g Table 2 1 Soyuz TMA spacecraft specifications 3 2 Description of the modelling problem Figure 2 2 Soyuz TMA vehicle with orbital module command module and service module Image courtesy of NASA section Figure 2 3 shows the module from the inside It is mostly used as storage for equipment not needed during reentry e g cameras and experiments The kitchen and a toilet are also located in the orbital module as well as the radar system KURS the life support systems and the docking system It has a length of 3m a diameter of 2 25 m and a habitable volume of 4 8 m At its far end it contains the docking port The hatch at the other end which connects the orbital and the command module can be sealed turning the orbital module into an airlock in case the crew needs to exit the vehicle when it is not docked to the station There is an additional hatch on one of the sides through which the crew exits during an extra vehicular activity EVA This side hatch is also used by the crew to enter the vehicle on the launch pad The command module CM is also a pressurized module and is the only one returning to Earth at the end of the mission During ascent descent and landing the crew is seated inside the command module During reentry the module is protected by an ablative heat shield First it is slowed down by the atmosphere At an altit

Modelling of Soyuz Docking and Radar Systems

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