Mach Speed Club

Discussions on high/extreme altitude and mach busting rockets.

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Re: Mach Speed Club

Postby Sumo310 » Wed Dec 27, 2017 9:25 pm

Thanks for the encouragement to post this Drew ;)

I've spent far too much time digging through an old and dying laptop, a backup drive, an old camera and and 2 phones to try and get some photos - without a lot of success.

Additional stats on the 38mm rocket Dave (Pink Hat as he liked to be called) and I built, posted above:
Length - 77cm CF plus 2 inches of motor overhang
Nosecone - 5:1 Von Karman fibreglassed
Weight: 270g plus 20-30g of nose weight.

The rocket was optimised as a sustainer so couldve been improved further. We chose not to fly it in the 2 stage configuration as a delay in sustainer ignition would have potentially pushed us to over 30,000. Significant time was soent modelling in OpenRocket and RASAero to identify optimal rocket shape, safe stability margin and also sustainer ignition timing. We spent time studying the work of others, namely Curt VD and Adrian Adamson. We didnt beat Curts altitude as the then J-record holder but topped his speed.

What made it a success was the integrated avbay / dual deployment tube and head end ignition setup.

We started with a plugged 38mm fwd closure and removed the threaded extension. What was left of the closure was then drilled to take a 3mm insert which the HEI wires were to be passed through. The setup was sealed with JB Weld and a gasket sealer and worked quite well in testing. 2 further holes were drilled to retain the avionics to the motor as the original plan to use a larger bolt wasnt going to work with the limited thread we had left to grip into. The avbay was split in 2 with a sled in the middle, which held 1 raven and a lipo.

Ontop of the Avbay was the main chute tube. The nosecone would be deployed at apogee via the charge seen ontop of the avbay, next to the chute bay, with the 12" chute deployed from within this tube. Testing of this setup revealed 0.3g of FFFG was enough to punch the nosecone across the yard and through the side of Daves garden shed.

The avbay and single-break dual deploy chute setup was readied outside the rocket, fastened to the motor and slid into place as a single unit. The top of the avbay was pushed up against the dual-deploy cylinder and then fixed to the body tube - the cylinder is propping up the nosecone in the airframe picture below. A single screw was inserted through the airframe and retained the avbay and motor.

Tracking was via a Walston transmitter tied to the nose cone shockcord. 2 nosecones were purchased but none were the right shape, with 1 of the cones significantly out of round so was promptly binned. A 5:1 VK nose was machined and used as a mould for us to glass over.

I dont have too many pictures of the rocket that are of decent quality, the bits I found interesting are shown below.

1. Original fwd closure.
2. Modified fwd closure.
3. Closure, avbay and parachute tube.





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Re: Mach Speed Club

Postby SpaceManMat » Fri Dec 29, 2017 10:11 am

Sumo, can you please expand on your chute setup?
How was DD acheived and why the tube especially given how small the 38mm frame is?
QRS: 124
Highest Altitude: 13,647 feet
Fastest Flight: Mach 1.55
Largest Motor: CTI 1115J530 IM
Current Project: X Wing

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Re: Mach Speed Club

Postby drew » Thu Jan 11, 2018 3:09 pm

SpaceManMat wrote:Sumo, can you please expand on your chute setup?
How was DD acheived and why the tube especially given how small the 38mm frame is?

It's a "Shotgun recovery system" similar to what GLR's Mariah 38 and 54 utilises. Effectively the value add from utilising this type of single break dd setup is that you can minimise airframe length as the "shotgun tube" can be all the way into the NC which minimises wasted space.

Simon, thanks so much for posting this data. I'm still in awe of that flight and I'm mightily impressed by the custom HEI hardware y'all built but didn't leverage. Speaking of which, would you be interested in selling that forward closure? :wink:
Andrew Hamilton
AMRS 28 L3
AMRS Records Committee Chairman
Max Alt AGL - 23,908ft - K300 - Balls 22
Max V - 2,488 ft/s, ~Mach 2.2 - M2250 - THUNDA 2015

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