wiki/ news/ 2011-07-31 - Attempted July Launch

July Launch of LV2.3

July 31st 2011 we headed to central Oregon to launch our rocket with the same roll control as the previous launch, but this time with much of the full flight computer we have been planning for years in in place and running. This included the PowerPC flight computer, a Hemisphere Crescent GPS receiver board, and our new 2.4 GHz Amateur TV broadcast system with overlay.

Unfortunately the rocket motor failed on ignition, ejecting the fuel (unburnt) from the motor casing. The force of the depressurization lifted the rocket off of the launch rails, to about 30-40 feet into the air. Although the drogue parachute did eject, the rocket came down fairly hard and suffered minor damage to the fin canister and aeroshell.

Launch Day

Photos

Video

Loading the rocket on the rail and hoisting the rail to launch position

Tower Cam

600 FPS High Speed Footage

View from the flight line

Cropped:

Failure Analysis

Critical failures

Major failures

Minor failures

Important Airframe Damage

CATO Analysis

We know that the motor stopped almost immediately after ignition. The rocket continued into the air for a short period of time unpowered and came to a rest just behind the tower. When the recovery team reached the rocket we discovered that the aft enclosure and nozzle were missing and most of the fuel had ejected from the motor casing.

Examining the motor casing we found the forward enclosure was also dislodged, though not entirely. Most interestingly the threads on both sides were undamaged. When cleaned and screwed back into the casing the aft enclosure still fit. This suggests that the motor casing expanded under motor pressure enough to disengage the threads of the two enclosures. What remains to be seen is why the pressure was high enough to allow this to happen.

Images

The tower cam had a wide angle lens that captured the event at 30 frames per second. Here we see four consecutive frames around the event:

The motor comes up to pressure in the first and second frame, then the enclosure appears to fail in the third. By the last frame there is little flame left, the motor has already failed and rapid depressurization extinguished the fuel (dP/dt failure).

A fuel grain is seen leaving the end of the motor two frames (0.667 seconds) after the event:

We can see the leftover debris from inside the motor scattered on the ground after the smoke cleared.

There were three fuel grains missing from the motor when we recovered it. The other three were stuck inside the casing with some kind of spacer wedged sideways blocking their escape. Only one grain was seen leaving the motor in the video so the other two must have been ejected in the initial event both so fast -- also suggested because they were found heavily damaged -- and still masked by flame and smoke.