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| Parameter | Metric | Imperial | Other Units |
|---|---|---|---|
| Apogee | 10,187 m | 32,406 ft | 6.14 mi |
| Max Velocity | 557.7 m/s | 1830 fps | Mach 1.67 (at 10kft MSL) |
| Max Acceleration | 116.6 m/s^2 | 383 ft/s^2 | 11.9 G |
| Ground Impact Velocity | 9.6 m/s | 32 fps | 21.8 mph |
| Flight Duration | 363.0 s | - | - |
Simulation Accuracy
The last simulation before flight predicted an apogee of 31600', which proved to be very similar to the true performance of the rocket. At 2.5% error, it seems our RAS Aero model is accurate enough to predict future flights of comparable rockets. After the flight all of the data was plotted. The results are shown below. A discussion of the pre-
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flight vehicle descent velocity mis-estimation is in the recovery section. The University of Victoria payload altimeter cut out during vehicle descent. The cause of this failure is unknown.
Avionics
Payload
See the Hermes I Payload Analysis page
Propulsion
Thrust Curve
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See the motor data page.
Long Startup Time
The motor took significantly longer to light than previous tests, including the second P motor test that used an identical igniter with twice the significantly more propellant surface area. In the P motor test, the igniter lit the motor in less than a second because it was held in the core During static fires the igniter was retained by gravity until the motor had built up enough pressure to push eject it out. The smaller flight motor was almost certainly slower to light because the . Video evidence shows that the igniter fell out of the motor within a second of firing and thus was only able to light a small portion of the propellant. This theory is supported by the video as you see a bright spot hit the ground shortly after the ematch is heard popping. To prevent this from happening, make sure the igniter includes some faster-burning substance like pyrogen, uses more propellant dust , or is held to the stick with extra wire or something that won't burn like the tape did. Though just a minor inconvenience on a single stage flight, ignition time becomes much more critical on a .
Future efforts could faster-burning igniters (pyrogen or BKNO3), higher surface area propellants (pixie dust), or additional mechanical retention. While chuffing represents a minor issue on this flight, successful, rapid, and complete ignition is a necessary technical milestone for multistage flight. Care must still be taken to not overpressurize the motor, though, so unless it is determined to be essential to a flight, a relatively slow igniter is not a problem and is the safer solution.
Recovery
Piston Deployment
Firing Force
Comparison with Ground Test
Parachute Velocities
Parachute Drag Coefficients (Effective)
It is not possible to do perfect analysis of the Parachute Drag coefficients because we cannot back out the drag on the mission package and booster sections. However, we can determine the effective coefficients (including the drag on these bodies).
Drogue
We trimmed the data so that it didn't include opening shock loads or main opening. We then performed analysis at two different altitudes (~30k ft, ~20k ft, and ~10k ft) in order to see the difference between different altitudes.
Main
Parachute Shock Loads
Drogue
Main
Structures
over-pressurize the case or clog the nozzle with a large igniter.
Recovery
The Telemetrum was configured as the primary altimeter, and the Raven was configured to fire 2 seconds after the Telemetrum for drogue, and 500 ft lower for the main. This was seen reflected in the post flight data.
Parachute Drag Coefficients
The drag coefficients of the parachutes were calculated–drogue was calculated using data between 7k and 8k meters, while main was calculated at landing. These drag coefficients are effective for the flight, they also factor in the drag on the mission package as well as interactions with the fin can.
Drogue Effective CD between 7k m and 8k m: 0.48
Main Effective CD at landing: 1.33
The expected drogue Cd was .36. With a correction for the drag of the body, it was expected to be between .36 and .40. This error is probably due to a conservative body correction or a poorly characterized fabric porosity.
Knake gives hemesphericals a Cd of about 1. It seems that both the main and the drogue Cd are 33% high. It is possible that the glide ratio is .33.
E-match voltage anomaly
Post flight data review notes abnormal voltage readings on Telemetrum apogee channel. Despite commanding an apogee event, the Telemetrum continued reading 4.2V across the channel for the remainder of flight. The e-match should register a significant increase in resistance within 10 mS of exceeding it's no-fire current of 300 mA. This suggests that the initiator misfired. A fishbone analysis was conducted to classify the nature of the issue. Evidence collection is ongoing, however it appear probable that the Telemetrum e-match is internally shorted, either autogenously or to the piston.
We checked continuity post-flight and neither e-match had continuity. This is not a conclusive test because the wires could have been jostled during landing or travel, however this suggests that the e-match was not internally shorted to the piston.
In the future, component level testing should include resistance checks of the e-matches before and after firing. A design revision of the firebolts should also include insulation as a design requirement.
Structures
Videography
Flight Cameras
The initial design for the Hermes avionics bay supported 4 cameras, 3 radial facing, and one downward facing. Due to integration time constraints, only two radial cameras were integrated. Due to a configuration error, the cameras took a picture when powered on. The cameras were Hawkeye Firefly Q6 cameras recording in 4K at 24 fps. It is recommended that successful video capture is considered part of a successful ground test. The cameras were also not configured with the correct time stamp. The value of the time stamp as an engineering reference should be weighed against it's 'tackiness'.
Ground Cameras
The ground cameras were laid out as shown.
| # | Camera | Note |
|---|---|---|
| 1 | Hero 6 Black | Charlie's. Failed to Record - heatstroke |
| 2 | GoPro Hero 4 | Andrew R's. Good Video |
| 3 | GoPro Hero 4 Session | Charlie's. Fell Over prior to launch |
| 4 | GoPro Hero 5 Session | Maddie G's. Good Video |
| 5 | GoPro Hero5 | Sam's. Good Video |
| 6 | Dayna's Cellphone | |
| 7 | Ellen's Cellphone | |
| 8 | Sam's Cellphone | Highspeed Footage. Tracked to cloud ceiling |
| 9 | Cannon EOS T6 | Ender Kerr. Stills on Burst. Beautiful. |
The high rate of failure of ground cameras suggests that we should put additional effort into our ground camera array. Doug's Rail has provided invaluable footage in the past.
Integration
Integration began at roughly 1:30 pm PST and the rocket arrived on the pad at roughly 3:00 pm PST.
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- Having a good checklist would have been beneficial, even though we likely wouldn't have been able to integrate the rocket in the amount of time that we were given before the end of the launch window if we had been following a strict checklist.
- Regular batteries are NOT enough to fire 2 e-matches in parallel. We ran into this problem during the ground test, as well as a previous static fire.
Times are indicated as T+ or T- from the first vertical motion on the rail (liftoff). Times are indexed off of the nadir (aft) facing Mobius camera. The zenith camera timestamps lag by 4.076s. Values are taken from either Pyxida or TeleMetrum data. Most StratoLogger data was unavailable to the author of this document.
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