ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
244 The results in Figure 9 for the NyeTorr 6200 which is made from the X -2000 Ultra (further refined MAC)  and PTFE are very interesting as the amount of particle generation trends higher throughout the entire test  than the 2000F and is classified one order of  magnitude higher in both the 1200 and 2400 RPM tests.  Beyond this difference, the NyeTorr 6200 generated ten times  the amount of particles less than 1 µ when  compared to the 2000F. Although this is within the allowed error for the Federal Cleanliness standards, it  is a significant difference when it comes to space critical applications. The issue is certainly not created by volatility as the X -2000 Ultra has lower ASTM E -595 results as well as Knudsen Vapor Pressures compared  to the traditional X -2000 fluids. Since the manufacturing process, additives, and PTFE polymer type are all  the same, this leads us to conclude t here must be some effect from the X -2000 Ultra on the particle  generation of the 6200.    While  the X -2000 Ultra contains less volatiles and has demonstrated that it  has superior outgassing  properties to the standard grade, the particle generation is negatively affected. The reasons for this could be as simple as the refinement of  the X -2000 has caused a change in the tribological properties of the fluid  which has led  increased friction between the fluid, PTFE polymer, and bearing surface. This additional  friction could lead to degradation of the lubricant which then leads to shedding of particles from the lubricant system. Another possible cause for this particle generation could also be the removal of something from  the X -2000 fluid that helped with the film strength or the compatibility with the PTFE polymer and its removal  has promoted the increase in particle generation.     

Figure 9 .  Dynamic Particle Generation of NyeTorr 6200     0200400600800100012001400 1 56 111 166 221 276 331 386 441 496 551 606 661 716 771 826 881 936 991 1046 1101 1156 1211 1266 1321 1376 1431 1486 1541 1596 1651NyeTorr 6200 2400 RPM 1200 RPM 200 RPM
245   Figure 10.   Comparison of the Dynamic Particle Generation  

In Figure 10, all of the samples tested in this study have been graphically plotted on the same axis to  visually illustrate the differences in the particle generation between different materials. The 2000F clearly  has the best performance of any of the materia ls tested.  

Conclusions  

Determining the volume of contamination generated from a lubricant through particle generation in dynamic  conditions is a new area just starting to be explore d. As presented in this  study, many factors play into the  behavior of a grease in respect to particle generation characteristics . Variables such as run speed, base oil  chemistry, and thickening agent properties all play into how much contamination a lubricant will generate  through particle generation .    This study has also shown  that the 2000F which is a PTFE -thickened MAC grease produced the least  amount of contamination due to particle generation as well as the least amount of change in particle generation over speed. It was also illustrated that while MAC lubricants have an advantage over PFPE base ones, it certainly depends on other factors like the thickener, additives, processing, etc. This dependency  was clearly seen in the sodium -thickened Rheolube 2000. The organic soap thickener forms  a strong matrix of entanglements but at higher speeds it generated m ore particles as a result of the shear  stability of the sodium soap vs. the PTFE -thickened greases . This is  due to the fact that PTFE is a very  stable molecule with Carbon- Fluorine bonds being one the strongest known. This combined  with the higher  RPM creating higher shear on the thickener at the metal surface causing more particles to generate over   time. This leads to the conclusion that PTFE is the superior to sodium soap in particle generation and based  on the differences in thickener stability under the shear conditions of the test .     The ability to plot particle generation over time and see differences in the distributions of various materials, will help us to form hypothesis about particle generation over time using normalized probability. Utilizing this type of analysis can also be used to predict lubricant service life. From these estimations, we could  also look into ways to predict  saturation by contamination in a space mechanism or the probability for  success/ failure when using a certain lubricant.
246 Future Work  

The expansion of this work will include using Residual Gas Analysis  to determine the molecular weight and  chemical species of all contamination materials being generated in the particle generation test. Further  research will also be placed on the difference of PTFE polymers, X -2000 Ultra, manufacturing techniques,  etc. an d how this relates to bonding strength and in turn particle generation.  We will also investigate the  particle generation of a rolling element bearing system in atmospheric and vacuum conditions.  The main  goal of this work is to create a model and methodolo gy to be able to predict the failure probability of a  mechanism due to contamination when a certain lubricant is used.  

Acknowledgements  

I would like to thank my colleagues in the Application Development and Validation Testing Lab at Nye  Lubricants Inc. who conducted the Dynamic Particle Generation testing, specifically Mason Wood. I  would  also like to thank William Galary for all of his support and consultation about the Clean Room Industry and  its technologies. Finally I would like to thank Gus Flaherty for his work with me on designing and  constructing the Dynamic Particle Generation testing equipment.    References    [1] Galary, William: Ultraclean Grease. Journal of Advancing Applications in Contamination Control 1999; Volume 2, No. 7:23- 27   [2] Cleanrooms and associated controlled environments Part 1: Classification of air cleanliness. ISO 146441 1999;    [3] Classification of air cleanliness for cleanrooms. JIS B 9920 2002;    [4] Cleanroom and Work Station Requirements, Contr olled Environments. Federal Standard 209 1963;    [5] Galary, Jason and Flaherty, Gus: Investigation into the Dynamic Particle Generation of Lubricating  Greases. NLGI Annual Journal, 2016    [6] Lince, Jeffrey and Fleischauer: Solid Lubricants. Space Vehicle Mechanisms, 1997    [7] C.G. Venier, E.W. Casserly, Lubricants comprising novel cyclopentanes, cyclopentadienes,  cyclopentenes, and mixtures thereof and methods of manufacture, US 4,929,782 (1990).
248     Figure 1.   Inters atellite Link –  Principle  

For constellat ion program s, the components ’ cost ha ve a higher impact  than in nominal single satellite  missions.  A consequent design- to-cost approach was followed using open- loop stepper motors and as  many standard off -the shelf elements as possible. In Figure 2 the different elements can be seen.   

An elevation over azimuth axes approach was used for  the APM design. An indirect  (using gear wheels)   actuation principle was chosen to ameliorate the power (holding current reduction) and pointing (gear  ratio) budget.  The Azimuth axis is supported by a bearing in O -configuration. In the azimuth axis there is  a slip ring ins talled, transferring the power and signals to the elevation stage. The RF signal is transferred  using a waveguide and two rotary joints (one to the spacecraft  and one to the elevation stage). On top of  the azimuth stage a stiff supporting structure (Yoke) is installed, providing the interfaces for the Elevation  Axis with its Antenna Supporting Bracket, the elevation actuation chain (comparable to Azimuth actuation chain) , and the interface for the HRM. The HRM is locking all relative movements of the Azimut h and  Elevation Stage by transferring the loads into the spacecraft  structure.  

Figure 2.   Inters atellite Link Mechanism  

Slip Ring  Elevation Rotary Joint   Base  bracket   HRM   NEA  MLI Antenna Inertia Dummy   Elevation Stage    Azimuth Stage   Azimuth   Stepper Motor  Waveguide   Elevation Rotary Joint
249 Compared to the heritage projects , the motor size had to be significantly increased in order to achieve  the  demanding  velocities and motor torque margins  according to ECSS . Besides  this, the reference sensor of  the azimuth axis  had to be changed (2.7 million activations) from a mechanical precision  switch  to a Hall  sensor switch. A demanding change was also the adaptatio n of the thermal management. As a  constellation by nature has an orbit with a very high sun illuminati on and an orbit with almost no sun  illumination;  the variety of the thermal environment is more complex than for a sun- synchronous orbit . 

All described c hanges led to increased masses and therefore higher  vibration loads. The Hold Down and  Release Mechanism and the bearings had to be adapted in order t o handle these increased vibration   loads.  

Qualification Approach   

An Engineering Model (EM) philosophy was decided. The EM qualification approach is  shown in F igure 3.  The qualification test program was accompanied by a bearing breadboard test and a life test  with a   simplified  life test model . This life test was started i n an early project phase. The life test verifies  the  demanding life time requirement of 12 years active in- orbit time  with 2.6 million revolutions.     As a cost  saving action  for the life test , it was decided that the life test model  will be driven by Commercial  Off-the-Shelf (COTS ) electronic s.  

Integrity, visual  inspection RF Power, RF  Frequency Band,  Insertion Loss,  maximum, VSWR  (GISL-6) microvibration Accuracy, Stability,  velocity profile,  motor current  (GISL-1, 2,3,4,13)Measurement of  Weight, CoG, MoI,  (GISL-7)Full Electrical Test EGSE Start-Up ASM &  EGSE01 ASM Physical properties  measurement 03 ASM Functional  Performance Test 05 ASM Micro-Vibration  Characterisation02 ASM RF performance  verification06 ASM Vibration/Shock  Test Degradation test of  EM under TV  condition (GISL-21)07 ASM TV-Cycling Test RF Power, RF  Frequency Band,  Insertion Loss,  maximum, VSWR  (GISL-6)02 ASM RF performance  verificationFunctionality under  TV condition 08 ASM TV Performance  TestAccuracy, Stability,  velocity profile,  motor current  (GISL-1,2, 3,4,13)03 ASM Functional  Performance Test Magn. Moment          < 0,2 (GISL-20)04 ASM Magnetic Moment  TestRF Power, RF  Frequency Band,  Insertion Loss,  maximum, VSWR  (GISL-6)02 ASM RF performance  verification

Figure 3.  Qualification Test Sequence
250 During the start -up of the APM with COTS  electronics  no significant anomalies (e. g., wrong cabling or  communication error)  were found. An overall mass of 10.8 kg (as designed) was verified during the  physical measurements.  

Testing  

All testing was  to be performed in the Friedrichshafen test ing facilit y. Due to availability at the v ibration  test facility , it was decided to perform the vibration test at Airbus DS  Ottobrunn.  After a non- conformance  report,  the test was continued in Friedrichshafen.  

Bearing Characterization Breadboard Test  As the chosen bearings were increased in diameter  compared to the heritage design,  a breadboard test  was performed to measure the impact on torque with the required velocity and  temperature inputs.  A  customizable  (all different types bearings used for the APM can be installed) bearing breadboard test   setup was de veloped and manufactured.  The test setup provides the ability  to compare the influence of  different bearing types, lubrication,  materials and combinations. Performing the bearing characterization  test as a breadboard test  supports monitoring the quality of the procured components and provides the  input data for the  torque margin and the bearing analysis.  

Figure 4.  Bearing Characterization Test Set -up in a TV chamber    ISL bearing characterization was performed at seven different velocity levels (1 rpm, 3 rpm, 17 rpm,   25 rpm, 35 rpm, 45 rpm and 100 rpm) and four different temperature levels ( -40°C, 0°C, 25°C and 65°C).  Each characterization was started with a run- in test, turning the bearing clockwise and counter -clockwise  for several minutes. After the run- in, the different velocity levels were repeated multiple times, deriving  multiple resistive torque measurements.    Compar ing the results of the measurements (see Figure 5) , it can be concluded that the bearing  performance was as expected in  the torque margin analysis. The worst case torque assumed in the  analysis was 75 N-mm and verified by a measurement of 72 N-mm (-40°C measurement) . At a lower  velocity level a higher , but still acceptable, deviation of 6 N-mm between analysis and measurement was  found.    An interesting phenomenon was the higher rate increase of the resistive torque for hot and fast  conditions. This was not investigated further, but viscous effects could be a possible source of such a  behavior.   

Conductive  heater/cooler   Bearing Setup   Actuator  Torque Sensor   TVAC chamber
251  Breadboard test ing gives Airbus DS GmbH the confidence of having a sufficient torque margin and that  the friction behavior of the preloaded bearing configuration is modelled correct ly. 

Figure 5.  Results of the Bearing Characterization measurements  

Life Test   The i nitially  planned life test ing at the end of the qualification campaign was skipped in favor of a separate  life test program  with a  simplified model  running in parallel to the EM test  campaign. The aim was to  provide a life -tested mechanism at the end of the 1. 5-year EM design and qualification phase.  

Cost savings for  the life test  were realized by  performing the test with the azimuth stage only. This  solution was selected as the loads  for the azimuth bearings (environmentally and in- orbit) were   considered to be the worst case. The azimuth motor and both gears have the higher number of revolution  during in-orbit life.    Prior to life testing,  a proper  environmental conditioning was  essential for the credibility of the life test.  This environmental conditioning consists of a vibration test and a thermal settling. The thermal settling in general is not a problem , and was performed directly before the start of the life test under the specified   acceptance temperature level in a  thermal vacuum chamber.    A higher effort  was the task to set up the proper  vibration level of the Life Test Model.  The applied l oad  levels  for the life test  model  vibration test were not known or they had a low confidence level . This was  the case due to the reconfiguration of the elevation axis and due to the early stage of the development   phase.  This conflict leads to a very high effort in the estimation of the vibration test levels for the life test  model.  The goal  was to load the single components as high as possible (identical to the EM) , but not to  damage the bearings .   The decision was made to estimate the test levels for the center of gravity. With those test levels it was  possible to predict the loading of the bearings and the actuator during the vibration test .  

Bearing  loads were applied with an elevation stage  dummy mass implemented in the t est setup.  Initial   approach to leave the dummy mass unsupported at  the Hold-Down and Release Mechanism ( HRM ) led  to unacceptable high bearing  loads . An additional support structure became necessary  and was  implemented in the test setup. Designing and implementing a support structure,  different from the EM  launch lock des ign, required much more effort  than expected. The additional  change of the initial motor  location induced further changes of the life test set -up. Those changes consumed the schedule margin for  life test ing.   During the performance of the accelerated life test, the time span of no motion (27 sec), due to  communication , was removed. This was necessary to perform the 12-year in -orbit operation within about
252 7 months. Active cooling of the motor was necessary as the motor was  continuously operating during the  life time test without any interruption. Without cooling the motor would heat up too much.  

Figure 6.   ISL L ife Test Model  Vibration Test Setup  

The life test motion set was derived from the current link  budget analysis. The motion set of 25 positioning  commands was  to be repeated during the whole life time test while the environment al condition was  changed. The life test also verif ies the rotation capability of the motor bearings, the correct function of  the  planetary gear stage and the spur gear . According to ESSS no  significant degradation during the required  lifetime  was allowed.  

Four main parameter s were measured (Figure 7) . The starting current with (blue) and without (green)  detent torque, the r esistance of all main and redundant windings (just one shown in r ed) and the s lip ring  resistance (yellow).  

Figure 7.  ISL L ife Test Model  Intermediate results for starting current, motor coil   and slip -ring resistance  

012345678910 050100150200250300350400 Resistancy (Ohm) Conducted CyclesCurrent (mA) Abs. Starting Current (mA) - Phase 1 main Abs. Starting Current (mA) - Phase 1 main clean SR Resistancy (Ohm) SR 1 Winding Reistancy (Ohm) - mainDummy Mass   Azimuth Stage   Support structure
253 Having tested about 90% of the total  life time (January 2016) , it can be stated that all measured values  indicate  a full success of the life test. The starting motor current, slip ring resistance and motor coil  resistance did not show any non- tolerable performance change.  

Performance Test   Test setup for performance testing (see Figure 8) allows  a stiff installation of two high- resolution absolute  encoders to avoid additional measurement errors. The performance tests  include measuring:   • pointing accuracy and stability   • starting current measurements (with/without detent torque)   • reference switch characteristic   • power consumption of the motors under ambient conditions  

Figure 8.  ISL A PM EM Performance Test Setup  

Evaluation of the results  showed that the test can be concluded successfully even under worst case  ambient conditions with a maximum pointing error of about 0.08 deg. The max imum pointing error is  shown in Figure 9 – left side (25 nominal positioning commands in a time span of 100 sec are plotted) .  The power consumption of a single motor is about 14  W per motor. Power consumption for one  APM  with  two axes  is estimated to be 28 W. Due to the long transmitting time in relation to the motion time an  average power  consumption of about 6 W is estimated.  

Figure 9.  ISL A PM EM Performance exemplary Pointing & Power Test Results   2 4 6 8 10 12 14 16 18 20 22 24-0.1-0.0500.050.1 MotionPositioning Error in deg      Measurement 1 Measurement 2 Measurement 3 Measurement 4 Measurement 5 Measurement 6Mean Error Azimuth = 0.01308 deg and STD = 0.0028098 deg 2     4     6      8    10    12   14   16   18    20   22   24   Motion      0.1     

 0.05 

      0 

-0.05        

  -0.1  Positioning  Error in deg   -50 -40 -30 -20 -10 0 10 20 30 40012345678 Time in SecPower in Watt  Power in Watt   -50  -40   -30    -20   -10     0     10     20     30    40    50   8     

7 

6 

5 

4 

3 

2 

1 

0  Time in Sec  ISL APM  Engineering Model  Azimuth Encoder   Elevation Encoder
254 RF Test   The RF Link  (Wave Guide with Rotary Joints) was a new development  subsystem  from M IRAD AG  Switzerland. RF-performance measurement was done by a set of 24 static two- port measurements  (changing azimuth and elevation pointing angle). An intermediate meas urement can be seen in Figure 10.  

Figure 10 .  ISL APM  EM RF Test Setup  

Evaluating the Return Loss  (Figure 11 – left) and Insertion Loss (Figure 11 – right) over the full motion  spectrum showed successful  performance results . The return loss was below 1.2 dB and the insertion  loss was below 0.8 dB. The angular variation of the Return Loss  was slightly above the expected 0.1 dB .  

Figure 11.  ISL APM  EM Return Loss  (left) & insertion Loss (right) Test Results over the complete  motion range  

All in all the performed work from MIRAD AG was fully in line with the required RF performance of the  subsystem.  

Vibration Test   The specification for the launch loads was given as 20G from 5 to 60 Hz and 6G from 60 to 100 Hz for the  Sine Vibration and 0. 12 g²/Hz x (M+20  kg)/(M + 1 kg)  for Random Vibration.  The Vibration Test was  performed at Airbus  DS in Ottobrunn and Friedrichshafen. The vibration was controlled via base force  notching. The base force was directly measured by four force sensors installed underneath the mounting  interface (see Figure 12). The base force limits are defined via the quasi static design loads. In order to  protect  the Azimuth main bearings and the Actuator from over testing,  secondary notches were used. The  22                                23                                   24   Frequency in GHz   -10 

-20 

-30 

-40 

-50 

-60    

-70  Return Loss   Return Loss S 22  22                                23                                   24   X10 Frequency  in GHz   -0.45 

-0.5 

-0.55 

-0.6 

-0.65 

-0.7 

-0.75    

-0.8 

-0.85 

-0.9  Insertion  Loss in dB   Insertion Loss S 21 COTS EGSE   Port 1   Port 2   APM
255 bearings were limited to a peak  Hertzian stress of 3360 MPa (including all ECSS ratings) and the  Actuators were limited to 40 G acceleration at the center of gravity .  The X and Z axes could be qualified successfully with just minor usage of secondary notches. The Y axis  was qualified to an input level of 5G. A load dependent behavior was found in intermediate testing (1/4  level limited to 10g response of the motor) . The load dependent effect was investigated (see Figure 13).  The ISL heritage design had to be adapted due to the more demanding requirements. The heritage HRM  system did perfectly work for X and Z axis  of the ISL, while enabling a frictionless release. In the Y axis,  due to the design changes, too much load was transferred over the HRM Base interface. The  enhancement of this i nterface, combined with some minor  structural strengthening, will enable a  qualification up to 20G load input.  

Figure 12.   ISL APM  EM Vibration Test Setup  

Figure 1 3.  ISL APM  EM Y- Axis  Vibration Test (Acceleration on Elevation Motor)   As a series of subsequent qualification tests had to be done, the rework will be realized after the completion of the qualification test campaign. The residual risk for this rework and the final vibration  quali fication of the Y axis up to 20 G load input is limited. In summary , the EM vibration testing has  proven its importance by identifying the need for the rework, while the equipment has nevertheless  proven its viability for the usage in the constellation program.  

Vibration Adapter  APM in locked  configuration   Load cells for Base  Force notching