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This is the flight motor for Hermes Flight 1.
The motor is almost identical to the second 4G 152mm OW static, but uses 8.5" long grains to increase propellant mass slightly. It was decided that this was reasonable deviation from the tested motor as it was only 3% more propellant. Another modification was the addition of a thrust ring to the nozzle carrier, but this was also a safe change as it did not modify how the motor functioned internally. The burn was perfect and propelled Hermes 1 to around 32,000', RT's highest flight yet and our first use of custom propellant in a rocket.
Statistic | Value |
|---|---|
| Propellant Weight | 34.96 lbs |
| Impulse | 32900 Ns |
| Max Pressure | Unknown |
| Classification | O-4300 |
| Delivered ISP | 211s |
| Grains |
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*propellant mass estimated by delivered impulse prior to anomaly, improved estimate to come after failure analysis
Unfortunately, a failure of the liner at the splice point led to propellant gases burning through the middle of the case at approximately 3.1 seconds into the burn.
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Data
Issues
OW-152 #25-28 |
Media
Data
To determine data about the motor, the acceleration graph from the telemetrum was exported and combined with velocity data, estimated rocket mass at the time of each datapoint, and the CD from Ras Aero to calculate the thrust of the motor at each sample. The result matched the expected value based on the previous test, so this method seems to work well. The spreadsheet for the calculation is attached.
Transport Pictures
MIT's FSAE graciously transported our grains and liner most of the way to Los Angeles, but we probably should have put more care into packing. Given how thick the liner is, though, none of these imperfections proved to be a problem and the motor fired and cleaned up as usual.
Detail 1 - Gross Acreage Damage
Phenolic tube Liner sustained damage during transit. Root cause Cause appears to be insufficient packaging.
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Detail 2 - Nozzle End Damage
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Is - Slightly buckled and chipped phenolic and excess of polyurethane glueTube likely dropped or rolled into object during transit.
Detail 3 - Head End Damage
Should Be - Nominal Tube
Is - Plys of the tube are buckled inwards and slightly laminated.Tube likely dropped or rolled into object during transit.
