ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
-F  Figure 11. Section View of Rollers (2 of 8 shown)  Root Cause  A Slot in the body was enlarged to allow room for a larger diameter flywheel pin. The pin was enlarged to  allow for threads in the pin, to add a fastener to secure the main drive spring connection. This change  was made to address usability feedback from customers regarding difficulty with reset. What was not  considered at the time of the change was that the body slot was a stop feature for the roller cage, which  locates the rollers relative to flywheel in the latched condition (Figure 11). The result was that the rollers  were moved closer to detents in latched condition compared to the Gen 1 design. The new position was  nominally on the radius transition into the detent. This did not adversely affect nominal operation, but  under pyroshock exposure, especially in an over-test environment, a loss of preload occurred.  Corrective Actions  The problem was corrected by relocating the stop feature on the cage, returning the rollers to a nominal  position. The roller location was revised to be slightly further from the detents than the original position to  allow for tolerance stack-up and achieve a more balanced roller position. Units which were retested in  pyroshock with the corrected design did not lose preload. The change was implemented and the  qualification program was re-started with the corrected cage corrected design. All Gen 2 units were rebuilt  with the corrected roller location, and the Gen 3 design was similarly revised.  Discussion and Lessons Learned  This failure is an example of an unintended consequence of a simple change that was made from Gen 1  to the Gen 2 designs. The reason for the change was to prevent the difficulty resetting the mechanism  that can occur when the main drive spring rides up on the pin. The pin was enlarged to allow a fastener to  retain the spring, and the body feature was revised to accommodate the pin. Revising the body feature  shifted the roller position and affected mechanism performance. This change, along with other changes  made between Gen 1 and Gen 2 designs, was heavily reviewed on multiple occasions. Even with  thorough review, subtle interactions can be missed and changes can have unintended consequences.  Product Status  Gen 1 production has been phased out. The Gen 2 and Gen 3 qualification programs are underway and  contain all cumulative engineering improvements and lessons learned. Tolerances, fits and geometry of  all parts have been extensively reviewed and optimized for these next generation designs. The programs  are due for completion in mid-2006.  At present, there are at least 30 Gen 1 QWKNUTs integrated for pending flight missions. While this  delivered Gen 1 hardware has met all test requirements and remains extremely flight-worthy, the  robustness of the product has been greatly enhanced as a result of problems we've addressed.  86
showed ample stroke margins in the QWKNUT, the variability of the production environment resulted in  margins well below the analysis.  When failures do occur, a disciplined approach to investigation is vital to ensure true root cause is  identified and corrected, and that the approach does not compromise hardware. During a failure  investigation, multiple tests, combined with non-standard testing to resolve a specific issue, can lead to  over-stress of other parts in the system. In addressing the vibration failure, we did not expect to trigger  another failure due to overstress. We can frequently become so consumed with solving one problem that  we create another problem with the hardware. Continued testing and resolution can sequentially fail one  part, then the next, and so on. This can be painful process, but ultimately one that makes the hardware  better.  Failures present an opportunity to make significant improvements in a product. Close scrutiny of a design  during failure investigations allows discovery and resolution of issues outside the scope of the failure,  resulting in a more robust product. The learning that takes place during a failure investigation can far  surpass the most effective design review process. In the course of our investigations we found ourselves  saying "we never would have discovered this problem if. .."Specifically, if the discrepant lot of levers had  not caused a vibration failure, the dual spring design change would not have been made. Performance  margin variation would not have been detected, and the mature process controls now in place may not  exist. Though our industry can be intolerant of products with a history of anomalies, the investigation  process is an effective and perhaps necessary path to a truly robust and reliable product.  88
SoftRide Vibration and Shock Isolation Systems that Protect Spacecraft from  Launch Dynamic Environments  Conor D. Johnson*, Paul S. Wilke* and Scott C. Pendleton*  Abstract  Reduction of the vibration and shock loads seen by spacecraft during launch greatly reduce the risk that  the spacecraft and its instruments will be damaged during their ascent into orbit, and also allow more  sensitive equipment to be included in missions. Protecting the satellite from these loads by whole-  spacecraft vibration and shock isolation systems has now been demonstrated. The basic concept of  whole-spacecraft isolation is to isolate the entire spacecraft from the dynamics of the launch vehicle. This  paper discusses two different systems: the SoftRide system and the ShockRing system. This paper  discusses each of these types of systems and presents flight data that demonstrates their effectiveness.  Introduction  Satellites are perhaps among the most amazing products in use today, used for many purposes from  communications to reconnaissance to weather prediction, and much more. Like all other products,  satellites undergo design, fabrication, test, and shipment. However, the shipment of a satellite to its final  destination in orbit is far more complicated than for all other products. Since the launch of the world's first  satellite in 1957, the capability and reliability of launch vehicles have improved dramatically. What has not  improved in 48 years of launching satellites is the launch vehicle-induced vibration and shock environment  that a satellite must endure on its trip to orbit. Excessive dynamic and shock loads can be a satellite killer  causing permanent damage to electronics, optics, and other sensitive equipment. To compensate for the  harsh dynamic environment, payloads must be designed and tested to very high dynamic levels, greatly  increasing the cost of many payload components. An excellent alternative is to reduce the launch dynamic  loads through the use of whole-spacecraft passive vibration isolation.  Whole-s acecraft vibration isolation has been developed to attenuate dynamic loads for some launch  vehiclest2, has been successfully flown several times, and is in development for other vehicles and  loading conditions. Whole-spacecraft vibration isolation systems can be discussed as systems that  significantly reduce the dynamic loads in both the low frequency range (coupled loads analysis range) and  in the high frequency range (shock loading range) or systems that only reduce the high frequency shock  loads (Figure 1).  W hole-spacecraft shock 001  I I I  10 Hz 70 Hz  Figure 1. Frequency ranges for attenuation for shock and vibration isolation systems  W hole-spacecraft vibration isolation systems have typically been designed to date to attenuate launch  dynamic loads from about 12 Hz and upward. This is very useful for mitigation of vibration loads on launch  * CSA Engineering, Inc., Mountain View, CA  Proceedings of the 38'" Aerospace Mechanisms Symposium, Langley Research Center, May 17- 19,2006  89
that type of isolation system will be referred to as a lateral or shear isolator. Whole-spacecraft vibration  isolation systems may also be a combination of these.  The SoftRide whole-spacecraft vibration isolation  systems have flown on two different launch vehicles  to date: Orbital Science Corporation’s Taurus  launch vehicle and the Air Force Minotaur launch  vehicle (Figure 2). This paper discusses axial and  combined axial + lateral SoftRide systems designed  for and flown on these launch vehicles. Even  though these systems were designed to reduce  transient vibration loads below 80 Hz, they  performed extremely well at reducing high-  frequency loads. W hole-spacecraft vibration  isolation systems are now offered as a launch  option in the Taurus Launch System Payload User’s  Guide’ and in the Minotaur Payload User’s Guide2.  Minotaur is a four-stage, ground-launched solid  propellant, inertially guided spacelift vehicle from  Orbital Sciences Corporation. It uses the first two  stages from the Minuteman II intercontinental  ballistic missile (ICBM) combined with the upper  two stages, structure, and fairing from the orbital  Pegasus XL air-launched space vehicle3. Figure 2. I rie I uurus and Minotaur  launch vehicles A -rL,  Passive Whole-Spacecraft Vibration Isolation Systems  Two types of passive whole-spacecraft vibration isolation systems have been flown. These are (1) a  patented uniaxial damped flexure system called SoftRide UniFlex, and (2) a patented multi-axis damped  flexure system called SoftRide MultiFlex. These systems are intended to attenuate low-frequency launch  vibration loads from about 20 Hz and higher.  The SoftRide vibration isolation systems seek to reduce dynamic loads on a payload by blocking the  transmission of dynamic loads present in a base structure to which the payload is attached. The design of  classical vibration isolation systems typically assumes that the base is rigid and the isolated payload has  dynamics only well above the isolation frequency. Contrary to this, the design of a SoftRide system must  be done with full knowledge that the structures on either side of the isolation system, namely the launch  vehicle and the spacecraft, are both very rich in dynamics. This necessitates that the SoftRide system  must be approached from the perspective of system-level dynamics.  Some of the typical design constraints are weight, volume, and strength. Two other major constraints on  the design of the isolation systems are:  0 Do not introduce excessive spacecraft to fairing relative displacement.  Do not introduce modes that are too low in frequency or high in amplitude such that they interfere with  the LV attitude control system.  The design of the isolation system therefore requires coupled-loads analysis (CLA), along with detailed  design analysis. The basic procedure involves the following steps:  0 Preliminary CLA with worst load cases to optimize system-level isolator performance and get  component-level requirements  0  0 Isolator concept design to meet component-level performance requirements  Isolator loads analysis to determine design loads for isolator strength design  91
Isolator detailed design to arrive at a design that meets all strength and performance requirements  Complete CLA using final detailed isolator models in the system model to verify system-level  performance  The CLA must be performed with actual launch vehicle and spacecraft models. The typical procedure at  CSA is to obtain LV models and loads for worst case conditions from the LV manufacturer and perform  CLA with the latest model of the spacecraft supplied by its manufacturer. Once the detailed isolator design  analysis is completed, then a model of the isolation system is delivered to the LV manufacturer for a  complete and final CLA.  The following sections describe the isolation systems and present flight telemetry data.  H.LW*d.IRnpanr SoftRide UniFlex  The patented SoftRide UniFlex whole-spacecraft vibration  isolation system is intended to reduce dynamic launch  loads that are predominantly axial (thrust-direction) in P..tRmo-O 14 -1  nature. The design procedure requires CLA to accurately  predict the responses of the spacecraft with an isolation  system. As an example, CLA showed that the isolation  system significantly reduced spacecraft responses due to  the resonant burn load. For example, the spacecraft net  C.G. response in the axial direction was reduced by a  factor of seven by using the isolation system (Figure 3).  I L  I  Figure 3. Spacecraft axial C.G. response,  resonant burn load I  The stiffness and damping of the isolators are  sized to mission-specific requirements for  reduction of these dynamic loads. This system  consists of a set of damped flexure elements that  connect the spacecraft to the launch vehicle.  Figure 4 shows a UniFlex isolator. This consists  of a titanium flexure and a constrained layer  damping treatment. The metallic load path of this  isolator allows a strong, predictable, stable  connection between the spacecraft and the  launch vehicle. The damping treatment provides  sufficient damping to control resonant  amplification of loads. The typical application of  this isolation svstem is to replace each bolt at a  Figure 4. SoftRide UniFlex and its installation  SoftRide MultiFlex  92
The patented SoftRide MultiFlex whole-spacecraft vibration isolation system is intended to reduce  dynamic launch loads that are both axial (thrust-direction) and lateral in nature. Again, CLA is required to  design the MultiFlex for the particular LV / spacecraft. Sample results for the design analysis showing  responses non-isolated and isolated is given in Figure 5.  The stiffness and damping of the isolators are sized to mission-specific requirements for reduction of  these dynamic loads. Similar to UniFlex, this system consists of a set of damped flexure elements that  connect the spacecraft to the launch vehicle. Figure 6 shows a MultiFlex isolator.  -7 hM M WI(U -  -bh YI-7 -YII 0s. w OUR.-  --, I-- , -,-  i - r--  :i1 i:  to the SoftRide system  Figure 6. SoftRide  MultiFlex and its installation  This consists of a pair of UniFlex isolators separated from one another by a central post. The axial  isolation is achieved by virtue of the UniFlex isolators in ries with one another. The lateral  achieved by the shearing of the assembly with bending oc rring in the flexures. The typical ap  lation system is to replace each bolt at a field joint with a MultiFlex isolator element, a  Figure 6.  Flight Heritage of Whole-Spacecraft Vibration Isolation  There is significant flight heritage for  whole-spacecraft vibration isolation.  These systems have, to date, flown on  six separate missions. Flight telemetry  data indicating the flight performance of  the isolation systems is available from  all missions except the MightySat  mission and will be presented in the  following sections. Table 1 summarizes  the missions on which SoftRide has  flown.  93
side of the isolation system. The remaining spacecraft  histories. The isolation system significantly reduces the -151 0 10 XI 30 40 50 60 70 60  R58Z55-hlrrllliS vibration level to the payload by 50% for all load events. Time (sec) - Above iwlaton  Figure 7. GFO flight data - below and Taurus 3 / STEX .. The Taurus/STEX SoftRide isolation system was very  similar to that of GFO but "tuned for this mission. The sm MDh. meIdWMl2 H2 wjpn  ''1 I--&hVbhtm II  STEX spacecraft was heavier than the GFO and  therefore the isolation system was larger. With one  successful flight of this system, the program offices  allowed a slightly more aggressive design (lower in  frequency) to be flown. Finite element models of the LV -  and spacecraft were obtained and full coupled-loads  analyses were performed to design the isolation  system. While the first mission (TaurudGFO) required  both component-level and system-level testing of the  isolation system, only component-level tests were  For the Taurus/STEX mission, data from two  accelerometers, again one below and one above the  isolators, was obtained. An overplot of this data is  shown in Figure 8 (this data has been high-pass filtered  to eliminate the quasi-static accelerations). This data  shows a factor of five reduction in the broadband acceleration levels above the isolators. 10-  ,.  i a--  -I-  performed on the TaurudSTEX system. -10 -  0 io Za sa a 5n e4  B57E-hn-1888 -lo  Figure 8. STEX flight data - below  and above isolators  It is of great interest to examine the performance of the SoftRide isolation system in the frequency  domain. This allows inspection of the broadband attenuation characteristics of the SoftRide system. The  dynamic system made up of the launch vehicle and spacecraft is non-stationary due to continual  propellant depletion and stage separations. Also, the highly transient nature of most launch load events  precludes digital signal processing of the flight data averaged over the entire launch window. Therefore,  the frequency content of the transient flight data is best observed by creating waterfall PSD plots. These  plots show the PSDs of 2-second windows of transient data, overlapped by 1 second, and stacked up next  to each other.  Figure 9 shows the waterfall plots for the axial acceleration below and above the isolators from the STEX  flight. Note that the sample rate of 4000 Hz only allows data to be examined up to 2000 Hz. Examination  of these plots shows that the SoftRide system provided significant reductions in the acceleration levels  across the broadband spectrum. The high frequency accelerations below the isolators may be due to  structural-borne acoustic energy. The SoftRide system has greatly reduced the structural-borne acoustic  vibration on the spacecraft.  94
Figure 9. Waterfall PSD of STEX data - below and above the isolators  Taurus 5 / MTI  obtained below and above the isolators in both the  axial and the radial directions. The instrumentation AblPn IMlstaS  and data processing were done similarly to the GFO  and STEX missions. Transient data and waterfall  PSD plots for the axial direction are similar to the  previous flight data. Transient data plot for the radial  direction is shown in Figure 10. Note that the UniFlex  axial direction, but also provides significant reduction  in dynamic responses in the radial direction. For the TaurudMTI mission, flight telemetry data was MTI ngm w.. FIW stape. Ramd  15  ~ wowlsdalom  5 Lateral  isolation system not only provides attenuation in the -* r '  I  10 20 30 40 50  Tim (sac) -15'  61  Figure 10. MTI flight data - below and  above isolators  Taurus 6 / QuickTOMS & OrbView4  The Taurus 6 /QuickTOMS & OrbView 4 mission (see Figure 11) was the first dual mission where both  satellites were protected by separate SoftRide systems. Flight telemetry data was obtained below and  above the isolators in the axial direction for both satellites. Transient data plots for the axial direction are  shown in Figure 11 for both QuickTOMS and OrbView4. This data shows that the isolators provided  excellent response reductions, similar to other Taurus flights.  95
Figure 11. QuickTOMS and OrbView4 satellites in the launch configuration and flight data  Minotaur 1 / JAWSAT  The Air Force funded a significant data acquisition system on Minotaur for the purpose of assessing the  performance of the SoftRide vibration isolation system. A total of 18 accelerometers were flown for  measuring accelerations on both the launch vehicle side and the spacecraft side of the isolation system.  These accelerometers were arranged into 6 triaxial sets: three triaxial sets on the hard side and three  triaxial sets on the soft side. Flight data was examined and the trends observed agreed very well with the  predictions of coupled loads analyses. An example of some SoftRide acceleration flight data from the  JAWSAT mission is shown in Figure 12.  Figure 12. Typical SoftRide flight data from the Minotaur/JAWSAT mission  The auasi-static acceleration measurements have not been filtered out of this data. Note that excellent  vibration isolation was achieved in both the axial  (thrust) and the lateral directions.  Data showing the fairing separation shock event from  the Minotaur/JAWSAT flight is shown in Figure 13.  The flight accelerometers were not shock  accelerometers and therefore some clipping of the  high-level “hard side’’ shocks has occurred. However,  the isolated “soft side” shows greatly reduced shock  inputs to the base of the spacecraft.  Minotaur 2 / MiahtvSat  The MinotaurIMightySat mission was the second flight  of the Minotaur launch vehicle. The auxiliary data  acquisition system for collecting SoftRide  performance data was not flown on this mission so  telemetry data is not available. The launch was a  complete success and the MightySat spacecraft, after  its soft ride to orbit, began operation as planned. .m 1 I I  116h I188 1111 117 1172 117A 1176 1178 116  m* (-1  I<Dlrn*rn  Figure 13. Fairing separation shock  flight data showing SoftRide attenuation  SoftRide Shock Isolation Systems (ShockRing)  96
W hole-spacecraft shock isolation systems have been designed, analyzed, tested, and flown and others  are currently in development. These isolators are optimally located in the stack just aft of the satellite in  order to attenuate all shock loads from the launch vehicle. Candidate locations include (1) at the top of the  payload attach fitting (PAF), just below the satellite separation system (Figure 14), (2) at the bottom of the  PAF, or (3) integrated somewhere within the PAF. One patented design for a whole-spacecraft shock  isolation system is shown in Figure 14. This is a continuous ring made of a series of highly damped  flexures. The designed-in compliance, the high damping, the contorted shock path, and the assembly  joints all combine to make this an effective light-weight isolation system. This isolator design, along with  several other designs that are in development, have been tested and results will be presented in the  following discussion. Flight results from the first flight are also presented.  Figure 14. Whole-spacecraft shock isolator at top of PAF  W hole-spacecraft shock isolation  systems are currently under development  for the purpose of attenuating shock  inputs from the launch vehicle to the  spacecraft. The major source of these  shock inputs is typically fairing separation  shock, dual payload attach fitting (DPAF)  separation shock, stage ignitions, and  stage shutdowns. While UniFlex and  MultiFlex vibration isolation systems are  tailored to mission-specific requirements  for low frequency isolation, the shock  isolation system is planned to be more of  an “off-the-shelf” component. It is  envisioned that, for each class of launch  vehicle, the shock isolator will be a \ I  riyuic IP. ratciircu wiiui~~pa~.cc.iai~ 3iiuc.n  isolation systems (ShockRing)  “couple sizes fits all” type of system for the purpose of attenuating launch dynamic loads from frequencies  of about 70 Hz and higher, depending on the design. Several patented shock isolators are shown in Figure  15. The largest is over 180 cm in diameter.  97