Overview
The launch of Hermes 2 occurred at 11AM on July 6, 2019 from Friends of Amateur Rocketry in the Mojave Desert, CA. The launch operations were some of the smoothest in team history, due to great effort in rehearsals and procedures planning.
The Hermes 2 vehicle was 138.2 inches long and weighed 167.4 lbs at liftoff. For the second year in a row the FAR ignition system experienced difficulties on the first launch attempt. A quick recycle of the count and a hot-swap to FAR's wireless system yielded positive results and the motor lit successfully. A timeline of flight events is presented below. The onboard video is considered the timing master for all events.
| Event | Time [s] | Altitude [m] | Velocity [m/s] | Notes |
|---|---|---|---|---|
| Ignition | -0.80 | 0 | 0 | Audio transient used. Flames not visible for another .14s |
| Liftoff | 00.00 | 0 | 0 | Absolute time reference at first vehicle motion |
| Tower Clear | 00.33 | 6 | 47 | |
| Start of Constant Roll Increase | 03.37 | 749 | 516 | \dot\omega_z = 336\degree/s^2 |
| Pitch Event | 03.69 | 886 | 569 | |
| High-G Event | 06.07 | 2849 | 918 | This event likely saturated the on board accelerator for .02s at a reading of 32 G |
| Vehicle Disintegration | 06.35 | 3011 | 920 | Body rates jump from <10 degrees/s to >300 degrees/s. Tilt angle exceeds 45 degrees (previously 16 degrees) |
| Piston Actuates | 11.67 | 3679 | Unknown | Velocity measurements likely inaccurate |
| Mission Package Impact | 70.40 | 0 | 70 | Interpolated. Last data point logged at 34m altitude and -28 m/s, which is almost certainly inaccurate. Previous recorded value used. |
| Booster Impact | 108.60 | 0 | 46.5 | Booster impact velocity estimated from kinematic model with estimated terminal velocity. |
The exact cause of the anomaly is unlikely to be conclusively determined, but we have several open fault trees which provide a path forward to resolve high-risk items prior to flying again.
Telemetry Analysis
Systems
Flight Performance
Altitude, velocity, acceleration, how they compare to expected values.
- \dot\omega_z
- Fourier Transform of vehicle pitch and yaw rates
Comparison to pre-flight simulations
Projected Flight Performance
- Expected Apogee
- Expected burnout velocity and altitude
Propulsion
Flight Overview
May just be a link to the P9100 #2 page, but a dedicated write-up would be appreciated.
Ignition Transient
We lit the motor fast and hard this year. Good job laying the chuffing from Hermes Flight 1 to rest.
Nozzle Liberation
Estimate the centripetal acceleration that caused the nozzle to be ejected.
Estimate the time that the nozzle was liberated
Nozzle Erosion
Was the nozzle erosion we saw on this flight a factor of flight, stochasticity, or did it occur after the failure?
Recovery
Overview
Piston Actuation
Soft Goods
Why do we think we couldn't find them? When do we think they fell out of the rocket?
Avionics
Flight Overview
Away team - great
Telemetry - great
Cameras remote start - big improvement, ways to go
Lithium Polymer Battery Review
Can we get a table of all the batteries we flew and all of them that blew up here?
TeleMega GPS Lock
Discuss TeleMega GPS lock status, proposed resolutions here
Structures
Flight Overview
Fin Failure
Weather it was the impetus or symptom of the failure, Hermes 2 returned to the ground 4 fins short of a rocket.
Uncertain Fate of Nose Cone
Do we think it worked? Might it have buckled?
Paint
Should we consider better paint for next year?
LE Recovery Guard
Looks like it did an admirable job
Avionics Shield
Acrylic Bad
Payload
Flight Overview
Camera Arming Difficulties
Payload DAQ Fate Unknown
Noise on LE DAQ
Was this the p-tap? Systemic? From the board?
Operations
Flight Overview
Radio Comms
- Freaking awesome
- Ensure people know how to use them, especially people high up the chain of command
- Radio discipline, especially for the away team
- Have a 'CapCom' who narrates the launch for people not on the flight line
Transport
Gas in cars. 2 SUVs was good. Coffee shop purchases bad
Camping
How'd it go?
Recovery Operations
Running to the booster - bad, need to improve discipline after a failure
Search Line - went too far, need to plan search area before leaving
More people watching in other directions, temptation is too high just to stare down-range. We may have missed soft goods or nose cone coming down elsewhere on the range