Hold Down and Release Mechanism Hardware Simulator for Ground Deployment Testing
The project involves developing a hardware simulator for testing a Hold Down and Release Mechanism used in Mars Sample Return missions. The simulator aims to replicate the functionality of expensive flight hardware at a lower cost and with reduced lead time. Key requirements include precise activation timing, load capability, and form factor similarity to flight hardware. Extensive research and trade studies have been conducted to select components such as linear solenoids and photointerrupters to meet these requirements effectively.
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Presentation Transcript
Hold Down and Release Mechanism Hardware Simulator for Ground Deployment Testing Intern: Kian Vilhauer Mentors: Jon Kraeuter, Joe Schepis, Trevin Dear
Background Mars Sample Return Mars Sample Return Capture, Contain and Return System Work supports Mars Sample Return (MSR) mission Specifically, supports testing of Spin Eject Mechanism (SEM) separation system Well-controlled separation of Earth Entry Vehicle from Earth Return Orbiter is essential for safe return of samples to Earth s surface Extensive testing is necessary Left: MSR mission architecture, SEM activation circled. Right: SEM shown circled in cross-section of Capture and Containment Module
Background Hold Down and Release Mechanisms (HDRMs) Mars Sample Return Capture, Contain and Return System HDRMs are a class of common spacecraft hardware Restrain components during launch and transit Allow components to deploy, separate, jettison, etc. later in a mission Various types of devices, e.g., pin pullers, cable cutters, separation nuts Work focused on separation nuts aka sep-nuts Flight HDRMs are expensive and have long lead times As much as $30k-50k per unit Up to 18 months lead time Many HDRMs cannot be reset after activation, those that can have a limited number of reset cycles Cost, lead time, limited reset capability make testing difficult Top: Sep-nut made by Eaton Bottom: HDRM made by Glenair
Driving Question Mars Sample Return Capture, Contain and Return System Can we make something that works the same for less money / with less lead time? Doesn t need to work for flight, just for ground testing Simulator requirements Simultaneity Current SEM requirements require less than 10ms between all 3 HDRM activations Load Capability Simulator must be able to support up to and activate under 200 N preload Form Factor Simulator should release a 1/4 bolt Simulator should be similar in size to flight HDRMs currently under consideration for SEM
Methods Research and Trade Studies Mars Sample Return Capture, Contain and Return System Researched existing HDRM designs Conducted trade studies for several elements of simulator Actuator Considered solenoids and various motor technologies Selected linear solenoid for high simplicity and actuation speed Sensor Considered off-the-shelf components as well as custom inductive and conductive sensors Selected photointerrupter for high electrical and mechanical simplicity Mechanism Considered designs based on flight HDRMs and simpler, more novel designs Selected sep-nut design based on existing design for high reliability
Methods Trade Matrices Mars Sample Return Capture, Contain and Return System Actuator Solenoid / Electromagnet DC Motor Servo Motor Stepper Motor Linear motion w/ very few moving parts Very simple to control Good for rotary motion Very simple to control Variety of sizes Good for rotary motion Position control Simple to control Variety of sizes Good for rotary motion Position and velocity control Advanced stepper drivers make lack of feedback a non-issue Advanced drivers provide many other functions Pros May be hard to buy May be difficult to design from scratch May have high power requirements More parts required for rotary motion Mechanisms using a solenoid are likely to revert to initial configuration when power is cut More parts required for linear motion No feedback No position control More parts required for linear motion No position feedback No velocity control / feedback More parts required for linear motion Significant amount of external control circuitry required Higher power requirements Often relatively large Cons Cost Medium Low Low Medium Complexity Medium Low Medium High Mechanism Design Retaining Pin Retaining Ball Bearing Retaining Wheel w/ Flat Rotary Retaining Hooks Modified Sep-Nut Quality Weight Reliability 0.3 2 3.5 4 3.5 5 Simplicity 0.3 4 4.5 4 3 2 Cost 0.1 5 5 4 4 3 Resettability 0.3 5 1 1 3 5 Totals 3.8 3.2 3.1 3.25 3.9
Methods Design and Prototyping Mars Sample Return Capture, Contain and Return System A model of the simulator was created in CREO Differences from a flight sep-nut Actuation force Bearings for rollers Application of solenoid force vs. release of restrained spring Separator springs The CREO model was exported, with some modifications, as 3D- printable models Changes made to enable 3D printing Threads made using threaded inserts No bearings Reduced preload force Difficulties unique to 3D printing Parts shrink holes smaller than specified Difficult-to-remove supports for some features Top: Cross-section view of simulator and bottom view showing slides for nut segments Bottom: Parts of prototype test of nut segment construction (left) and full-featured nut prior to splitting (right)
Results and Conclusions Mars Sample Return Capture, Contain and Return System Results A 3D-printed prototype will be completed to confirm the operational principle of the simulator A professionally-manufactured metal version of the simulator can be used to verify the device s operation at the full required load Conclusions It is possible to perform ground-based testing of HDRM-requiring mechanisms more efficiently by using devices that simulate flight HDRMs The general design of the device presented is suitable for a variety of applications requiring similar HDRM simulators Lessons learned First real experience working with other engineers Time / complexity everything takes longer / is more complicated than I expect Better appreciation for precision / dimensional accuracy Learned to use CREO / gained experience with CAD Be careful of scale real parts are often smaller / larger than you d think from how they look in CAD
