G77 RMS Mishap Yesterday

[DaveHein]

Originally posted by Graham Orr
all it took was 35psi to pop it out.

Graham,

What did you use for motor retention? Was it friction fitted or did you use positive retention? It's interesting that the motor retention failed at 35psi. It seems that the upper section should have ejected instead. Of course, this probably saved your rocket from being fried, but a free motor under acceleration is a scary thing.

How far away did the motor land? Did it fly horizontally the whole way, or did it execute a number of random sky-writing loops? This must have been quite exciting!

Dave

 

[paparoof]

Graham:

Thanks for the supplying me with my new desktop image on my computer. That's awesome.

 

[Graham Orr]

Hey Dave,
Since this was a test flight, we were using a 38mm motor in a 54mm MMT. The adapter was held in by a very strong motor retainer made of 7075. However, because we are not using motor ejection, we figured a tape fit woud be good enough to retain the 38/240 casing in the adapter.

The booster section is actually sealed (besides a few small vents). This, in combination with the tape-fit motor saved the booster from getting scorched horribly. The booster took several weeks to make (full-time) because it has 15 sensors embedding in the composite...and all those wires had to be routed discretely... I'm just glad that this mishap didn't sever any of those connections.

 

[Graham Orr]

"Thanks for the supplying me with my new desktop image on my computer. That's awesome."

Paparoof: No problem. It happens to be my desktop pic as well (as well as the whole team...lol)!

(If you look closely, you can see one of the rail guides broken off an floating in the air just left of the rocket)

 

[Graham Orr]

"How far away did the motor land? Did it fly horizontally the whole way, or did it execute a number of random sky-writing loops? This must have been quite exciting!" - Dave

The moto zipped around a little bit but it was interesting that it actually had a definite "net path" to its flight. While under thrust, it was rapidly spinning (roughly 30 RPS) but it shot pretty quickly to the left (as shown) and went horizontal for about 1000 ft at an extremely high speed (probably on the order of 700 fps).

The video can be found on our website (which needs more updating... soon to come) on the right side of the page.

https://www.eng.hmc.edu/NewE80/TestFlights.htm

Enjoy!

 

[deandome]

I noticed that this launch has been immortalized on the Tripoli Wisconsin website...note the photo titles they gave 'em :lol:

https://www.tripoliwisconsin.org/Y2007PIX/photos/pre-boom2.jpg
https://www.tripoliwisconsin.org/Y2007PIX/photos/kaboom2.jpg


:surprised::surprised:

1) I'm surprised at the amount of smoke on the ground, given it's a redline not BJ or anything.

2) You can really see how/why the tubular nylon cord was literally melted for a good 18".

3) you can see how lucky I was that the chute got outta the 'burn-path'...that was a brand new 24" Tac-1 on it's maiden flight!

It ended up going a bit higher, and it cracked a fin on landing. I dug out the TTW root, made a new one, epoxied it in & it's all set for a sunday launch.

Truly a Phoenix!!!!