LUNAR’clips 2003                        Volume 10, Number 6

Copyright © 2003 by LUNAR, All rights reserved.

Flying on 15 Year-old Engines

I am a Born Again Rocketeer (BAR) thanks to the efforts of a co-worker who is a member of LUNAR. I attended the October Launch and flew a couple of rockets, but the highlight of the day for me was flying a rocket of my own design.

I designed and built S.P.I.R.I.T. back in 1989, but I never launched it because I didn't have a launch system capable of igniting an engine cluster. LUNAR provided me that opportunity on October 18th. Little did I expect the maiden launch to go CATO.

S.P.I.R.I.T is a 2-stage payload rocket, the first stage being a cluster of 3 engines. The first stage core consists of an A to C size engine, which ignites an A to C size engine on the second stage. The first stage core is flanked by two mini engine "boosters". These boosters are selected such that their thrust duration is shorter than that of the core engine (for successful staging). The mini engines also use an ejection charge to deploy a streamer recovery system after the staging event has occurred.

For the first flight the first stage engine selection was a B6-0 with two A3-2T mini engines, and the second stage was an A8-3. All three engines ignited, but shortly after clearing the launch rod the core engine B6-0 exploded. The resulting fireball ignited the A8-3 in the upper stage and sent S.P.I.R.I.T. soaring to the heavens. Meanwhile, the first stage, with the mini booster engines still firing and its core engine ejected, flew in an arch back down to Earth, where the streamers were futilely deployed. If you enhance the image, you can see the two mini engines still providing thrust and the Second stage engine igniting and starting to produce thrust. That was failure number one.

Failure number 2 occurred at an altitude of several hundred feet when the ejection charge pushed the engine out of the back instead of deploying the 'chute out of the front of the stage. Stage two performed a brilliant impression of a lawn dart.

Damage: Amazingly, none!

Lessons learned:

1. Don't launch 15 year old engines.
2. Ensure a tight fit of the engines.
3. Ensure a loose fit of the parachute.
4. Rethink career as Rocket Scientist.

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