Advanced-Lightweight PCM Actuated Pin-Puller Release Mechanism for Spacecraft

Team: Logan Hales, Jacob Heninger, Whitney Stewart

Sponsor: Thermal Management Technologies

Project Description

The team was tasked with developing a scalable PCM-driven (Phase Change Material) actuated pin puller that can handle significant axial and lateral loads with a large stroke length. This product would be used to secure and deploy hardware of many shapes and sizes in space, from solar panels, to small satellites, to antennas. The actuator must operate in space conditions as well as conform to the following requirements:

  1. Electrical: Operate on 24-32 V with proof of actuation and redundancy
  2. Temperature: Operational: -75 C to +85 C, survival: -200 C to +85 C, non-actuation temperature: +90 C, and external Surfaces: <5 C above interface temperature
  3. Shaft Size: Baseline: 0.25-in diameter with scaled designs of 0.187-in and 0.375-in
  4. Shaft Force:
    1. Axial baseline: 150 lbf with scaled designs of 100 lbf and 275 lbf
    2. Lateral: 375 lbf
  5. Stroke Length: 0.5-in
  6. Volume: Baseline: Dia. <1.5-in; Height <3.0-in plus shaft
  7. Actuation time: <60 sec (goal) and repeatable in+/- 1 second over temperature range
  8. Test for and survive more than 250 cycles
  9. Mass: Baseline must have a mass of less than 100 grams
  10. Easily resettable
  11. Use all space approved materials

Performance Review

Testing Results and Methods

Testing Stand/Setup

  • Extruded Aluminum Parts
  • Lever arm design to test all required loading cases
  • ~25 V Power source, Type T-Thermocouple

Conclusions

  • Weight added to the testing system does not dramatically affect actuation time
  • Test Day 1 data was closer to the desired 0.5" actuation amount
  • More data is needed to prove effectiveness
  • Current predicted full actuation time 711.33 s, at which the actuator would reach very high temperatures
graph of performance review

Design Description

The major components can be seen in Figure 2. Note the insulator is removed for clarity. In Figure 1 the three different sized components are shown.

Figure 2: Exploded view of the Actuator with major components.

Figure 2: Exploded view of the Actuator with major components.

  1. Shaft (piston, seals)
  2. Chamber
  3. Wax (Rubitherm RTC 100 HC)
  4. External Components (heating element)
Figure 1: The three actuator designs with 0.375", 0.25", and 0.187" diameters in order.

Figure 1: The three actuator designs with 0.375", 0.25", and 0.187" diameters in order.

Conclusion

Challenges of the Design:

  • This project showed the importance of early testing.
  • Initial designs were delayed which led to a long development time and delays for seals.
  • Finding manufacturing for the internal diameter surface finish proved difficult.

Lessons Learned:

  • A Streamlined design process would have moved the final project forward 1-2 months.
  • Focusing on designs and creating feasible products before the wax was chosen would have created a better design.
  • Considering manufacturing feasibility from the onset would have prevented many difficulties such as the internal surface finish and part acquisition.

Recommended Future Work:

  • Redesigning the seals or the internal surface finish to prevent leaking and make it more manufacturable