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.
| Requirement | Description | Component | Compliance |
|---|---|---|---|
| 3.1 | Dual Deploy CONOPS | Architecture | Vehicle is Single-Separation Dual-Deploy |
| 3.1.1 | Apogee Event | Avionics | System can accurately detect Apogee |
| 3.1.1 | Drogue Descent Rate | DGB Parachute | Descent velocity is between 75-150 ft/s. Compliance is TBD |
| 3.1.2 | Main Event | Avionics | Event Shall be no higher than 1500 ft AGL. Exemption Obtained. 2,000 ft AGL acceptable for larger parachute |
| 3.1.2 | Main Descent Rate | Main Parachute | Landing velocity is less than 30 ft/s. |
| 3.1.4 | Torsion Relief | Swivels | Swivels are implemented to relieve recovery system to airframe torsion |
| 3.1.5 | Drogue Color | DGB Parachute | Drogue is orange and white |
| 3.1.5 | Main Color | Main Parachute | Main Is red and black. |
| 3.5 (4.0) | Energetic Devices | Firebolt | TBD |
| 3.5 (4.0) | Energetic Devices | Tender Descender | TBD |
| 3.6 | Testing Compliance | Procedures | EHS and MIT Facilities procedures followed during all testing |
| 3.6.1 | Successful Ground Test | Architecture | Flight components have a successful ground test prior to flight |
| 3.6.2 | Successful Flight Test | Architecture | Flight Test Indefinitely Postponed |
| 4.2 | SRAD Pressure Vessel | Piston | TBD |
| 6.2.2 | Recovery Attachment Points | U-Bolts | U-bolt made of steel other than stainless steel |
Design
The design considerations associated the Hermes recovery system are summarized in the following pages:
- Webbing Lengths
- Webbing Material
- FireBolts
- Hermes Deployment Sequence
- Drogue Parachute
- Shear Pins
- HADES ("Piston-Cup-Diaphragm" System)
- Pyrotechnically Operated Piston (POP)
- HADES Piston (SRAD Redesign)
- HADES Cup
- HADES Diaphragm
Testing
Component Level Testing
Ground Testing
A general description of ground tests can be found here.
Analysis
Planned Areas of Research and/or Improvement
As of 12/16/2017, there are several planned areas of research and/or improvement as well as "things to do" regarding Hermes' Recovery System:
- Solidify parachute, webbing, and other component packing volumes and arrangement: Unknown User (janssonm@mit.edu)
- Improved SRAD piston design: Unknown User (janssonm@mit.edu)
- Consider dampening system at the end of the piston (eg. spring) so that it doesn't slam violently
- Verify margin of safety on premature piston firing due to pressure buildup during ascent
- Consider small orifice to prevent premature piston firing
- Mass saving cuts to Cup and Diaphragm assembly: Unknown User (amel@mit.edu) and @Shannon Cassady
- Validate landing speed w.r.t webbing lengths and provide this information to all other subteams
- Research Nitrocellulose as an alternative to black powder: Unknown User (janssonm@mit.edu)
- Validate current piston by means of thorough testing: Unknown User (jhz@mit.edu)
- Gather data from P-tap: Unknown User (jhz@mit.edu)
- Gather data from accelerometer: Unknown User (janssonm@mit.edu)
- Finish theoretical model: Unknown User (janssonm@mit.edu)
- Machine testing assembly: Unknown User (jhz@mit.edu)
- Develop and run tests on Firebolts: Unknown User (alexlam@mit.edu)
- Finish drogue parachute design: Unknown User (jcoray@mit.edu)
- Finish alternative webbing research: Unknown User (jcoray@mit.edu)