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 | |
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.
Altitude, velocity, acceleration, how they compare to expected values.
Comparison to pre-flight simulations
May just be a link to the P9100 #2 page, but a dedicated write-up would be appreciated.
We lit the motor fast and hard this year. Good job laying the chuffing from Hermes Flight 1 to rest.
Estimate the centripetal acceleration that caused the nozzle to be ejected.
Estimate the time that the nozzle was liberated
Was the nozzle erosion we saw on this flight a factor of flight, stochasticity, or did it occur after the failure?
Why do we think we couldn't find them? When do we think they fell out of the rocket?
Away team - great
Telemetry - great
Cameras remote start - big improvement, ways to go
Can we get a table of all the batteries we flew and all of them that blew up here?
Discuss TeleMega GPS lock status, proposed resolutions here
Weather it was the impetus or symptom of the failure, Hermes 2 returned to the ground 4 fins short of a rocket.
Do we think it worked? Might it have buckled?
Should we consider better paint for next year?
Looks like it did an admirable job
Acrylic Bad
Was this the p-tap? Systemic? From the board?
Gas in cars. 2 SUVs was good. Coffee shop purchases bad
How'd it go?
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