Reverse tapered Hybrid

[kramer714]

Just posted a bunch of pictures on the tapered hybrid rocket I'm
building for rocstock. Im designing it for the Skyripper 54mm K engines

All the pieces are complete or nearly complete, the fins are bonded and the motor tube and retainer attached. Working on the e-bay now, dual altimeters and main ejections.

The concept is to have a rocket that tapers from large to small over
the entire length. Think the worlds shortest body tube with the
longest boat tail. Originally I was planning to have a straight
section where the nosecone meets the body tube, dumped that idea for a
totally tapered look. The wides part is in the nosecone around 2
inches from the body tube.

Another unique feature is the way I'm doing dual deploy. I have a mid
bay that opens out from the side of the rocket. I have a charge
holder that mounts into a bulkhead I built, a cap is fixed to the
door. I ma adding a few spring latches to keep it shut until the
charge goes off.

I ended up making another tube for the parachute, making a tapered
nosecone seal, yet release when the charge went off became too much of
a pain. The cheater tube makes the main deployment very conventional.

 

[Wingarcher]

I'm curious about your deployment scheme.... The "usual" thing to do at apogee is to destroy the stability of the rocket- usually by cutting it in half. Two fairly non-stable pieces fall sideways, etc etc.

Do you fire a drogue out the side hatch? The main?

Maybe I'm just still sleepy.

N

 

[kramer714]

yup, a drogue will come out the side hatch. It is near the CG and should keep the speed in check. i'm thinking of using a 24 inch drogue, if the attach point is aft of the CG (with the spent engine) the rocket should continue nose down but be significantly slower, if the attach point is forward of the cg it will fall unstable (but slow) with the rocket doing a falling leaf type of motion. If it is perfectly between the cg and the sideways cp, it will point like a weather vane.

This all assumes that the shock cord doesn't get tangled in the fins...

The side door comes out using a black powder charge, actually i designed the charge holder to fit one of the Newtons Third charge holders, it loads in like a bullet. I think you can see the top (pink colored) of the charge holder. when i tested it with the door facing up, rocket on it's side, the door flys off around 20-30 feet. I'm not sure exactly how I am going to pack the side bay. I want it to pull the chute out and let the shock cord follow it. I even thought of having a 'leaf spring' push the chute out or a 'sabot' to insure it comes out cleanly. I can fill the bay with foam and then shape it so there is a clean path out.

 

[kramer714]

details of the electronics bay.

I cut a small acess hole in the side of the rocket. Inside I have room to mount 4 'plates'. the plates are made from LE phenolic sheet, tis is a paper saturated phenolic plate used for insulators (McMaster Carr) . Each plate has a bonded in place floating nut plate. The nut can float around 1/16th of an inch making installation much simpler. These are 1/4 inch nuts, waay overkill but I had them left over at work.

I made 2 battery plates, each olds 2 batteries using a metal 9 volt mount. I added a plate that screws down between the batteries making them VERY secure. 2 batteries wired in parallel will give a good reliable 9v source, if one battery becomes disconnected I still have one in the circuit. I will be adding a wire with a molex connector to the battery plates.

I plan to run dual altimeters, yes this is way overkill but im using this project as a wrm up to my level three cert. I have one of the altimeters mounted in the picture. They use press in inserts again from McMaster Carr. Dont try to tap th phenolic plate material, you can get away with it on larger screws but the #4 threads work so well into a pressed in insert.

The door that will cover the access hole will have the safe/arm switches and the jumper plate to attach the charge wires. simple and easy to get to.

 

[kramer714]

And it flew!!!!

Worked great, I did get a bunch of double takes on the tapered bodytube. The side deployed drogue worked perfectly!

This picture is from Rocstock in November.

 

[Firefox]

Wow! Now thats cool, and just a little bit different from the norm. The tapered body reminds me of a LPR egglofter, and creates the optical illusion that the rocket has weathercocked towards you... from anywhere on the range!

 

[jj94]

Dang! That's awesome! How high did it reach?

 

[kramer714]

Rocksim showed around 6400 feet, I think is was closer to 4500 actual. I
had a little, um, operator error reading the altimeter.