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Purpose

The Hermes recovery system follows a dual-separation, dual-deploy architecture. The drogue deployment event is initiated at apogee by a pyrotechnically operated piston. The main parachute is retained via a Tender Descender until approximately 2,000ft. Subsystem and component designs, testing procedures and results, and research is summarized here.

Requirements

The following requirements come from the DTEG.

RequirementDescriptionComponentCompliance
3.1Dual Deploy CONOPSArchitectureVehicle is Single-Separation Dual-Deploy
3.1.1Apogee EventAvionicsSystem can accurately detect Apogee
3.1.1Drogue Descent RateDGB ParachuteDescent velocity is between 75-150 ft/s. Compliance is TBD
3.1.2Main EventAvionicsEvent Shall be no higher than 1500 ft AGL. Exemption Obtained. 2,000 ft AGL acceptable for larger parachute
3.1.2Main Descent RateMain ParachuteLanding velocity is less than 30 ft/s.
3.1.4Torsion ReliefSwivelsSwivels are implemented to relieve recovery system to airframe torsion
3.1.5Drogue ColorDGB ParachuteDrogue is orange and white
3.1.5Main ColorMain ParachuteMain Is red and black.
3.5 (4.0)Energetic DevicesFireboltTBD
3.5 (4.0)Energetic DevicesTender DescenderTBD
3.6Testing ComplianceProceduresEHS and MIT Facilities procedures followed during all testing
3.6.1Successful Ground TestArchitectureFlight components have a successful ground test prior to flight
3.6.2Successful Flight TestArchitectureFlight Test Indefinitely Postponed
4.2SRAD Pressure VesselPistonTBD
6.2.2Recovery Attachment PointsU-BoltsU-bolt made of steel other than stainless steel


Design

The design considerations associated the Hermes recovery system are summarized in the following pages:

Procedures

Testing

Component Level Testing

Ground Testing

A general description of ground tests can be found here.

Analysis

Failure Tree

Planned Areas of Research and/or Improvement

As of 1/10/2018, there are several planned areas of research and/or improvement as well as "things to do" regarding Hermes' Recovery System. A more complete list of tasks and details can be found for team members on Asana.

  1. Solidify parachute, webbing, and other component packing volumes and arrangement: Unknown User (janssonm@mit.edu)
  2. Improved SRAD piston design: Unknown User (janssonm@mit.edu)
    1. Consider dampening system at the end of the piston (eg. spring) so that it doesn't slam violently
    2. Verify margin of safety on premature piston firing due to pressure buildup during ascent
    3. Consider small orifice to prevent premature piston firing
  3. Mass saving cuts to Cup and Diaphragm assembly: Unknown User (amel@mit.edu) and @Shannon Cassady
  4. Validate landing speed w.r.t webbing lengths and provide this information to all other subteams
  5. Research Nitrocellulose as an alternative to black powder: Unknown User (janssonm@mit.edu)
  6. Validate current piston by means of thorough testing: Unknown User (jhz@mit.edu)
    1. Gather data from P-tap: Unknown User (jhz@mit.edu)
    2. Gather data from accelerometer: Unknown User (janssonm@mit.edu)
    3. Finish theoretical model: Unknown User (janssonm@mit.edu)
    4. Machine testing assembly: Unknown User (jhz@mit.edu)
  7. Develop and run tests on Firebolts: Unknown User (alexlam@mit.edu)
  8. Finish drogue parachute design: Unknown User (jcoray@mit.edu)
  9. Finish alternative webbing research: Unknown User (jcoray@mit.edu) & Unknown User (janssonm@mit.edu)
  10. Maintain webbing lengths for Pathfinder & develop lengths for Hermes: Unknown User (valeriam@mit.edu)
  11. Research alternative forms of shear pins: Unknown User (lukeqi7@mit.edu)
  12. Research quicklink efficiencies and run load simulations/tests: @Claire Buffington
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