Manufacturer: | Scratch |
Push-Me, Pull-Me
A DesconX Entry
(Contributed - by Nick
Esselman)
Wow, did time sneak up on me or what? I wanted to design and build a rocket for this Descon but kept putting it off. Then it was May and I hadn't started. So it was time to get busy. I have a great design and unique from all the other entries. Not extremely sophisticated but definitely functional. And, I was finally able to fly it this weekend. So here goes......
My design is a two-stager. It has a cluster-motor booster to a single-motor sustainer. I'm always afraid of staged-rockets because of the potential altitude (and my relatively small field), so I decided to add a feature to create more drag. I named the rocket Push-me, Pull-me. The motors "push" while the big cone-fin increase the drag "pull".
Get the RockSim file here.
As with the other entries, I have started with the Estes Gemini DC. The following steps are what I used to build the rocket:
SUSTAINER:
BOOSTER:
For finishing, I went with the quick-and-ready approach so that I could get the rocket flown before the deadline. I painted the sustained Navy blue. I could/should have applied some of the decals but didn't. I painted the booster orange.
FLIGHT:
I used friction-fit on all the motors. The sustainer was loaded with an A8-3.
This is pushed in until it is even with the sustainer tubing. The booster was
loaded with two B6-0's. These are also friction-fit until they are sticking out
about 1/2".
The launch rod fits in the gap between the pod-tubes and the cone-fin and then through the two launch lugs.
Upon pushing the launch button both B6's lit and off she flew. It was stable and straight up until the B6 thrust stopped. RockSim suggests the booster carried it to ~80 feet and I would agree by sight. It seemed to slow fast (see the graph below and look at the change in Drag).
Then the A8 lit and the rocket was off. Direction changed slightly (5 degrees?) but it was still straight.
I saw the ejection pop of smoke but noticed the nose cone did not come out and therefore no parachute. It came in ballistic and thumped into the soft ground.
Conclusion, the pre-cut exhaust ports reduced the exhaust pressure too fast and therefore the nose cone was not pushed out. That is the only explanation! I should have covered those with some of the scraps from the Estes Insert card.
BEFORE and AFTER:
These pictures show how I used epoxy to protect the booster from the
sustainer's motor. You can see that it held up. Yes, it got black, but it did
hold up.
NEXT STEPS:
I'm going to repair this rocket, because it was a nice performer without too
much altitude. It also demonstrates several rocketry techniques, including
cluster, gap-staging, and the use of a fin-cone. Not bad from a kitbash!
These are some things that I will now do to improve the design (going outside of the strictness of this contest):
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