April 10, 2004

Today's rocket launch

I talked about it here.

The weather was beautiful, and the site of the launch, Middletown Park, is really nice.

We were on a tight schedule because one of the team had to be at work early, so the plan was to get there, make a practice flight, turn it around and do another 'official' flight to try to improve on their qualifying score. To speed things along, the team had pre-loaded the engines into the rocket so that on the field all they'd have to do was install igniters and the altimeter and eggs.

When we arrived they quickly got prepped and safety-checked, and set the rocket up on the pad. Then it was a short wait for their turn to launch.

Countdown and all three first-stage motors lit. The rocket took off straight as an arrow and it was looking to be a picture perfect flight. First stage burn-out, and the second stage should ignite... should ignite... should ignite any time now...

The rocket coasted upwards, and as it was beginning to arc over the upper stage lit. She powered into the ground about 150 yards away. We collected our gear and went to recover it, to see what could be salvaged for the next flight.

No chance at a second flight. The nosecone was embedded into the ground, and shattered. The egg capsule was smashed too, as were the eggs inside. Much of the second stage was waterlogged (it landed on the edge of a pond) and the motor mount ripped free from the impact. The altimeter was beeping out 620 feet, just about half of the target altitude.

We sat down and started to recreate the flight to figure out what went wrong. When the motors were pulled from the booster stage, we found the problem. Instead of using booster motors (no delay, instant upper-stage ignition), they used upper-stage motors with a seven second delay. So instead of igniting the upper stage immediately, while the rocket was still moving fast and vertical, it slowed down and tipped over during those long seven seconds.

The guy that loaded the wrong motors felt really bad, but it was a simple mistake. I reinforced the lesson about using the checklist when prepping complex rockets, and tried to make the point that everyone makes mistakes now and then. The team has a good qualifying flight to turn in, so they still have a strong chance at making the finals.

Three different teachers also stopped by while we were inspecting the rocket and talked to the kids. I really appreciated that, because they were all supportive and their kind words made the team feel better.

They should know by the end of the week if they made the finals. I'll keep you posted.

Posted by Ted at April 10, 2004 09:54 PM
Category: Rocketry

Dang. I'm sorry to hear that. It almost sounds as if the minutes they saved is going to cost them hours down the road. I'm curious about one thing, tho--did they get the motors mixed up (that is, upper stage motors on the rocket boost stage & boost motors on the second stage), or did they use upper-stage motors for both stages?

Posted by: Victor at April 11, 2004 02:18 PM

I am appreciative of the link to the prior post as the context gave me a clue as to the use of the eggs. I was confused with it being Easter and all. I need some cheese because my brain doesn't seem to be clicking. That is a dangerous situation to be in when Miss Kitty is on the prowl.

Posted by: Mr Mouse at April 11, 2004 03:43 PM

For that flight they had planned to use 3 "D" motors in the first stage, and a single "E" motor in the second stage. The upper-stage "E" was correct, and would have been hard to mix up, because the E's are about an inch longer than the "D" motors.
When staging with Estes-style motors, you always use zero delay motors because that's what they're designed to do - ignite the next stage. If they'd have put in even one zero delay "D" motor, they probably would have been ok.

Posted by: Ted at April 11, 2004 07:50 PM
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