ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
As the Pushrod is retracted still further into the drill, it de-couples the Auger Chuck from the Breakoff  Shaft as shown in Figure 8. During the drilling routine, the Auger Chuck (3) and Breakoff Shaft (5) are  coupled together by way of a pair of locking balls held in place by the Pushrod (1). After drilling is  complete, the Pushrod is retracted upwards until the balls are unlocked by “falling into” a groove in the Pushrod (4). This decouples the Auger Chuck from the Breakoff Shaft, allowing the latter to rotate relative to the chuck so that the rock core can be sheared.  Finally, as the Auger Chuck and Breakoff Shaft are decoupled, this movement raises the Breakoff Cluster  Gear (Component 2 as shown in Figure 7), engaging the teeth with the main Breakoff Gear (Component  3 as shown in Figure 7) as previously described. The drill is now ready to break off a core. While the Pushrod is no longer necessary in the “One Bit-One Core” architecture, it serves an important  role in the ROPEC Drill by actuating a number of critical mechanisms. Figure 9. ROPEC Drill Pushrod Subsystem (1) Pu shrod (2) Breakoff Sh aft (3) Ground Tube (4)  Pushrod Threaded Section (5) Pushrod Deep  Threaded Nut (6) Pushrod Output Gear ROPEC Butterfly Subassembly Design The Butterfly sub-assembly design is based on a similar mechanism on the MER Rock Abrasion Tool,  and is shown in Figure 10. This sub-assembly is connected to the base of the Z-Axis Guide Roller Rail. The Butterfly sub-assembly allows the ROPEC drill to be placed on the surface of a rock at an angle of up to 15 degrees from the local surface normal of the target. This angle is limited by mechanical Angular Hard Stops (3). Once placed on the target, the Butterfly sub-assembly is preloaded against the rock to  help stabilize the drilling process. Contact Tines (2) have a raised diamond pattern knurl feature on them to help grip uneven rock surfaces.  The Butterfly sub-assembly utilizes two micro Contact Switches (1) for redundancy. These switches can  be used by the control system as a safeguard in case the drill loses preload during an operation. A  Pushrod Fully  Retracted Pushrod Fully  Extended12 5 364 204
Figure 11. ROPEC Drill End Effectors (1) Standard  Coring Bit (2) Rock Abrasion Brushing Bit (3)  Powder and Regolith Acquisition Bit (4) Core PreView Bit (5) Slot Bit 1. Standard Coring Bit – The current ROPEC Coring Bit is designed to obtain a 1-cm diameter by  5-cm rock core. This size was based on Mars Sample Return requirements at the time of  requirements definition. Honeybee Robotics has also developed a BigTooth cutter arrangement [3] where a single larger tooth cuts the outer diameter of the core. This allows the rock core to be ejected using a combination of gravity and drill percussion. 2. Rock Abrasion Brushing Bit (RABBit) – The RABBit adds rock abrasion and brushing capability to  the ROPEC similar to the Rock Abrasion Tool on the MER rovers. The RABBit allows the ROPEC Drill to penetrate through the weathered surface rind of Martian rocks, allowing science instruments to view the actual rock composition. The RABBit can also be integrated with a small scoop for capture and delivery of abraded rock cuttings, rock cuttings remaining from a drilling  operation, or surface regolith. 3. Powder and Regolith Acquisition Bit (PRABit) – The PRABit is a full-faced drill bit attachment that  can be used to collect drill cuttings or regolith samples. Cuttings from the drilling process are transported up the drill flutes and into a collection chamber. The internal sleeve collection chamber can be fully open, fully closed, or rotated to expose up to two different sized sieve screens, such as a 1-mm or 150-micron screen. Using the sieve screens, powder can be delivered to science instruments at a desired size fraction. A prototype bit has been successfully tested in five different rock powders [9]. 4. Core PreView Bit – This bit enables science instruments and imaging systems to view a small  core from a rock target before the decision is made to cache a full length core. Once a core is  acquired, the PreView Bit “window” can be exposed through rotation of the inner sleeve to view  the core. Figure 11 shows the PreView window partially open with a core inside. 5. Slot Bit – This bit allows science instruments and imaging systems to view a small width of the  core along its entire length prior to caching the Slot Bit in the Sample Cache. This allows mission  planners to have a better understanding of the quality of core that they will ultimately return to Earth. Figure 11 shows the Slot Bit fully open with a partially fractured core inside. Mechanism Design and Test Lessons Learned Flex Cable Design As shown in Figure 3, the ROPEC Flex Cable makes a number of complex bends in order to reach four  actuators. In the first iteration of the design, not all of the connectors were on one side of the flex cable.This was not communicated appropriately to the team responsible for fabricating the flex cable, and it was assumed that all connectors were on the same side. Prior to integrating the flex cable with the control system, a pin-to-pin continuity test was performed, and the results showed that the main input connector  1 2 3 4 5 206
References 1. Mustard, et al, (2013). Report of the Mars 2020 Science Definition Team. Online at  http://mepag.jpl.nasa.gov/reports/MEP/Mars_2020_SDT_Report_Final.pdf (as of July, 2013). 2. Gorevan, S., et al. (2003). Rock Abrasion Tool: Mars Exploration Rover Mission. /g45/g82/g88/g85/g81/g68/g79/g3 /g82/g73/g3 /g42/g72/g82/g83/g75/g92/g86/g76/g70/g68/g79/g3/g53/g72/g86/g72/g68/g85/g70/g75 , 108(E12), 8068  3. Zacny K., Chu, P., Davis K., Paulsen, G., Craft, J. (2014). Mars 2020 Sample Acquisition and Caching  Technologies and Architectures. In /g44/g40/g40/g40/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g38/g82/g81/g73/g72/g85/g72/g81/g70/g72 , Big Sky, Montana.   4. Zacny K., Chu, P. et al. (2013). Sample Acquisition and Caching Architecture for the Mars Sample  Return Mission. In /g44/g40/g40/g40/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g38/g82/g81/g73/g72/g85/g72/g81/g70/g72 , Big Sky, Montana. 5. Mattingly, R. (2005). The many faces of the Mars Sample Return Mission Architecture. In /g42/g88/g76/g71/g68/g81/g70/g72/g3 /g68/g81/g71/g3/g38/g82/g81/g87/g85/g82/g79/g3/g38/g82/g81/g73/g72/g85/g72/g81/g70/g72 , Breckenridge, CO 6. Zacny, K., Wilson, J., Chu, P., Craft, J. (2011). Prototype Rotary Percussive Drill for the Mars Sample  Return Mission. In /g44/g40/g40/g40/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g38/g82/g81/g73/g72/g85/g72/g81/g70/g72 , Big Sky, Montana. 7. Myrick, T., Core Break-off Mechanism. US Patent No. 6,550,549, April 22, 2003. 8. Zacny K., et al. (2013). Sample Acquisition and Caching Architectures for the Mars 2020 Rover  Mission. In /g36/g44/g36/g36/g3/g54/g83/g68/g70/g72/g3/g21/g19/g20/g22 , San Diego, CA. 9. Zacny K., et al. (2011) Development of the Brushing, Abrading, Regolith, Core PreView and the  Coring Bits for the Mars Sample Return Mission. In /g36/g44/g36/g36/g3/g54/g51/g36/g38/g40/g3/g21/g19/g20/g20/g3/g38/g82/g81/g73/g72/g85/g72/g81/g70/g72/g3/g9/g3/g40/g91/g83/g82/g86/g76/g87/g76/g82/g81 , Long Beach, CA 210
Figure 1. MOMA Mass Spectrometer with Aperture Valve Initial Aperture Valve Design Over 125 requirements for the valve were levied, which were then ranked according to importance and  distilled down to the 25 top “driving” requirements. The initial Aperture Valve design is illustrated in Figure 2. Sealing the inlet was accomplished by means of a Sliding Pin, which operated to open and close off  the Ion Tube. A solenoid was connected to the sliding pin connected to a pull-type solenoid, which when  energized, pulled the Pin to the open position, allowing ions to travel from a Martian sample below the valve, up the inlet cone and thru the hole at the base of the cone. After power to the solenoid was removed, the solenoid rapidly closed from stored energy in a recoil spring. Close tolerance between the sliding Pin and Valve Body produced a pressure leak rate consistent with the requirement of 10E-3 cc/sec  He for beginning of life and 10E-2 cc/sec He, end of life, which was defined as 125,000 actuation cycles. Table 1.  Requirements Pressure leak rate 10E-3 cc/sec He Operational cycle life 125,000 cycles Operational temperature -20°C to 50°C Valve open/close time <50 ms Mass 90 grams Failure Mode Fail closed Power 5 watts Material limitations Non-magnetic 212
Figure 2- Aperture Valve early design To meet operational and performance requirements, materials for Aperture Valve components were comprised of Titanium 6AL-4V. Titanium is well known material of choice for aerospace design with  benefits including: high strength-to-weight ratio, corrosion resistance and non-magnetic. Coatings applied  to the Titanium were added for surface hardness, lower coefficient of friction, and prevented galling  between the Sliding Pin and Valve body. The choice of coatings on these parts and application of the coatings to the Titanium base metal would prove problematic. Figure 3 illustrates two versions of the initial Valve design. Both feature the same mechanical sliding pin type concept. Clearance between the outside diameter of the Sliding Pin and bore hole within the Valve body were tightly controlled to 5 micron  (.0002 in) clearance. The valve body was coated with Titanium Nitride (TiN) by means of physical vapor  deposition or PVD, a process of sublimating pure titanium with nitrogen in a high energy, vacuum oven. The result is an extremely hard, thin, gold-colored film, commonly found on tool bits. The sliding pin was coated with Diamond-Like Carbon (DLC), another PVD coating having a desirable combination of a low  coefficient of friction and high micro hardness. In general, PVD coatings have a micro-hardness greater  than 80Rc, well above the hardness of tool steel. Both coatings were applied at 2.5 micron (.0001 in)thickness. Figure 3.  variations of coated valves 213
Problems with TiN and DLC Coatings Traditionally, the largest inherent problem with ceramic based coatings such as TiN and DLC has been  the issue of adhesion; typically the higher the diamond percentage in a DLC film, the harder the DLC film  but the higher the compressive stress within that film. In extreme cases, such stresses can create unstable interfaces (i.e., adhesion and/or cohesion issues) and the film may become prone to delamination. Figure 4 illustrates the results of Aperture Valve testing after less than 100 actuations. Figure 4 (left)  illustrates the bore of the valve body coated with TiN. Flaking of gold colored material inside the bore and  complete film separation from the base substrate is evident. From our experience, the PVD process used to apply TiN onto internal cavities and bore holes does not produce acceptable adhesion of the TiN film. It is not clear whether additional factors associated with substrate preparation within the bore were contributing factors. Figure 4 (right) illustrates excessive wear of DLC coating on the Sliding Pin. This was  probably the result of delaminated TiN flakes abrading the DLC surface. TiN on the cone and smaller  shaft feature on the Sliding Pin were requested by the science team. While monolithic coatings are most common, multi-layer PVD coatings are applied with acceptable results, depending on number of layers,  layer thickness, hardness of the coatings, etc. In this case, TiN was applied over the DLC coating with poor results, as flaking was evidenced here as well.  Figure 4. Coating delamination on valve parts In the laboratory, the assembled valve initially operated well, meeting open and close times of <50 ms per  the requirement. Leak rate on the valve was also initially within requirement of 1E-3 cc/sec He. After less  than 100 open-close cycles however, there was a notable sticking of the sliding pin; the solenoid could  quickly open the valve, however the recoil spring could not return the pin quickly due to particulates generated from TiN fragments. Finally, the valve pin ceased to open or close, overwhelmed by friction  between sliding surfaces. Moreover, scratches on the sliding surfaces prevented the valve from being refurbished resulting in a failure. The valve test chamber is illustrated in Figure 5. The Valve operates at  5-7 torr (Mars ambient pressure) in a CO 2environment. Upper Chamber (not shown) operates at 1E-6  torr. Physical dimensions of the initial Valve are 98 mm x 20 mm x 20 mm (LxWxH).  214
Figure 5. Aperture Valve test chamber ETU / Flight Aperture Valve design The second generation Aperture Valve for ETU and Flight was designed to specifically avoid the issues  associated with PVD coatings and the Sliding Pin sealing concept requiring 5 micron (.0002 in) clearance to the Valve body bore to create the seal. While the previous design was based on creating hard, durable sliding surfaces between the Sliding Pin and Valve Body to minimize friction and particulate wear, the initial Aperture Valve never achieved more than 1200 cycles before failing due to particulates. Obviously,  the initial Valve design could not meet the open-close requirement of 125,000 cycles. Therefore, another valve design was developed which specifically avoided the design weaknesses described. Figure 6 illustrates the improved valve design. Common features to the initial Valve include a pull-type solenoid, sliding carrier (not pin), valve body and recoil spring. Figure 6a illustrates the principle components of the new valve design. The innovation in the design may be found in the method of sealing the valve open and closed, similar to a check-ball design, whereby a ball fits into a spherical seat to create the seal. In this  design, the ball is placed into a socket forcing the ball onto the seat by a small spring. A sliding Carrier  containing the ball assembly translates to the right when pulled by the solenoid. Translation of the Carrier forces the ball out of the valve seat and into the Carrier. A hard stop prevents further motion of the Carrier, allowing a hole in the carrier to provide an open path for ions to travel thru the valve and up the inlet tube. When power to the solenoid is removed, the recoil spring sends the Carrier back, returning the  ball to the valve seat to complete the seal. Figure 6. ETU /Flight Aperture Valve    Figure 6a. ETU /Flight Valve Section 215
Results of ETU / Flight Aperture Valve Testing The ETU / Flight Aperture Valve design exceeded expectations for sealing and performance. The valve  seat design was unique for this application and routinely achieved sealing leak rates as high as <E-9cc/sec He. In fact, 5E-9 cc/sec in Helium was measured even after 125,000 cycles. Closure times also exceeded requirements; open and closure times of <50 ms (each way) were observed with a typical time  of 26 ms. The ETU / Flight Aperture Valve design proved superior to the original valve in meeting or exceeding design requirements. Tests were conducted on valve endurance beyond requirements, finding a small reduction in sealing leak rate after 250,000 cycles. Additional testing was subsequently performed  on the same valve to assess endurance when contaminates were introduced into the test chamber  environment. Mars regolith, an Earth-based concoction of materials to simulate a typical Martian bedrock soil was used for the test. The test valve was run again for an additional 30,000 cycles in the contamination environment without failure. Leak rate was measured at 2E-8 cc/sec He, approximately 5 orders of magnitude higher than the end of life requirement (1E-3 cc/sec He EOL spec vs. 2E-8 cc/sec He  on test valve). Conclusion The MOMA Aperture Valve development program was briefly discussed in terms of design improvements  resulting from prototype test results. The initial Valve design was based on over 125 requirements which  were distilled down to the top 25 “driving” design requirements. The initial Aperture Valve concept seemed promising, based on calculations and perceived merits. However, performance results of this design were disappointing, due to delamination of TiN and DLC coatings applied to the titanium base  metals, causing debris from the coatings to seize the valve.  Despite the loss, valuable information from weakness discovered in the initial Valve design was used to  develop a second, more robust Aperture Valve. Based on a check-ball design, the ETU / flight valve design resulted in significantly less surface area to create the seal. Moreover, PVD coatings were eliminated in favor of hardened, non-magnetic corrosion resistant alloys. Test results were impressive, with the valve achieving five orders of magnitude better sealing leak rate over end of life requirements. Cycle life was equally impressive, achieving 280,000 cycles without failure. Due to schedule constraints, the ETU / flight valve was never tested to actual end of life, however, it is estimated that the valve could  achieve 500,000 cycles, due to the relatively few particulates discovered during post-test inspection of valve components.  Acknowledgements The authors would like to thank Ken Blumenstock for engineering the solenoid design and Willie Barber  for his manufacturing expertise and support on this project.  216
these design choices helped in reaching a final drill mass of 2.9 kg, including cable harnessing (2.8 kg  without the cable harness as shown in Figure 1). Another major requirement was for the drill to interface with an existing Integrated Mars Sample  Acquisition and Handling (IMSAH) architecture developed by the Jet Propulsion Laboratory (JPL) [3, 4].This architecture relies on an embedded sample tube that collects the core during drilling. Once a core is drilled and captured, the bit must be docked to IMSAH and subsequently detached from the drill head. At  this stage, a mechanism within IMSAH is inserted into the back end of the drill bit to remove the sample  tube with the core. This full sample tube is then cached into a separate caching mechanism and a new clean sample tube is collected and reinserted into the back end of the drill bit. At this point the drill head can mate with the drill bit again to drill and capture a new core.   RANCOR Drill Overview The core mechanical components of the RANCOR drill are shown in Figure 2. This includes everything  except for the drive motor, spring Z stage, and proximity sensor for homing the auger axis. In this cross  section it is evident how the auger and breakoff shaft are driven together with the cam/follower percussive mechanism while rotating the Cam Shaft Upper in one direction. When rotating this shaft in the opposite direction, the overrunning clutch (eventually replaced with a ratchet) decouples rotation of the cam andauger, thus rotating only the breakoff shaft. This is the mechanism that enables relative rotation between the breakoff shaft and auger to shear and capture cores. RANCOR Drill Bit At the working end of any drill is the drill  bit. The RANCOR coring drill bit is  comprised of 3 main components: the  auger, breakoff tube, and JPL sample  tube (Figure 3 and Figure 4). The auger was designed around the JPL Sampling tube and requirements for collecting a core sample of 6-cm length and 1-cm diameter. To break and capture the core,the Honeybee Robotics patentedeccentric tube technology was used [5]. The auger shank was designed to fit with the three sets of guide wheel rollers found  on the chuck. To make the chuck as  compact as possible, the shank of the drill bit became an almost equilateral hexagon. Weight reduction features were created in  the auger since this component alone comprised about 8% of the overall drill mass. Hence, there are three pockets on  the alternate hexagon surfaces. It should be noted that the bit was designed to survive the load from the theoretical rover slip condition under Mars gravity. A 180-kg rover on a 20-degree slope would apply approximately 173-N side force to the bit.  Figure 2. Details of the RANCOR drill components 218
Figure 3. CAD image of the drill  bit with its components labeledFigure 4. Picture of the drill bit in an exploded drawing  view, Auger, Breakoff Tube and JPL Sample Tube Visible Constraining the auger vertically in the drill are the small flanges that protrude from the hexagonal  surface. The side of this feature fits in flats in the front end of the chuck. The groove in the shank is for  mating with a cam in the bit lock mechanism to constrain the drill bit from falling out. Additionally, the rounded surface at the shank end mates with a seal to prevent dust or cuttings from entering the drill  when the auger is in place. Caution should be taken in regards to cuttings and other debris since the complete drill bit assembly (complete with the JPL sample tube) should be in place to form a dustprotective seal. However it is important to note that this assembly is not a perfect seal. Material selection for the auger was decided based primarily on previously designed and tested Honeybee bit designs. The RANCOR bit uses a 455 stainless steel that has been heat treated to condition H900. This specialty steel was selected for its high performance characteristics of strength, toughness, and hardness. After manufacturing and heat treatment of the auger was complete, four rotary grade carbide inserts were brazed into place at the nose of the auger to serve as the cutting surfaces. Harder grade carbide was selected because this grade of carbide has been shown to survive percussion well when operating at relatively low percussive energy levels. At approximately 0.6 J/blow, the RANCOR drill falls into the category of low percussive energy. The advantage to using harder grade carbide is  increased bit life, so long as the carbide doesn’t fracture.   The breakoff tube (Figure 5) was also designed around the existing JPL Sampling tube. This mechanism interfaces with an Oldham coupling which is part of the core breakoff system. Design challenges for the breakoff tube included manufacturing for tight tolerances and clearances between the auger and the Oldham coupling interfaces. Different JPL sample tubes were expected to be inserted into the breakoff  tube. Interfacing with multiple JPL sample tubes was expected to be difficult from a tolerance standpoint as they are thin walled structures and are vulnerable to deformation. To finalize the ID of the breakoff tube, multiple JPL sample tubes were measured and the statistical deviation of the maximum sample tube diameter was determined. Then the breakoff tubes were appropriately reamed to 0.4440 inch (11.28 mm) to accommodate all of the existing JPL sample tubes. The material used for the breakoff tube was 416 Stainless Steel which allowed for design flexibility in that a harder metal could be obtained through heat treatment if it was deemed necessary. 219