Winter Project - Two Stage AP

Hello,

I\'ve been thinking about a project for next year, and thought I would run it by some people to see if it seems reasonable.

The objective is to do a two-stage AP rocket.

This is the general plan:
- 24 mm E28T or F39T first stage.
- Booster carries a timer to ignite the second stage. Probably 1/4 to 1/2 second after first stage burn-out.
- Booster carries its own parachute that is deployed by the ejection charge on the motor a couple seconds after separation.
- 24 mm E18W or E11J second stage.
- Sustainer carries an altimeter to handle deployment (possibly dual deploy).

I think the E28 could safely lift 20-22 oz of the pad. Guessing 3oz for altimeter & battery, 2oz timer & battery (in booster), 4.5 oz for 2 24 mm motors. That is 9.5 oz, so leaves about 12oz for structure and recovery. Seems reasonable.

I\'m thinking about 2\" diameter, so a BT-80 body tube. By doing a first-pass in RockSim, I think I can fit a chute and timer in a 12\" booster (not including the length of the coupler to connect to the sustainer). The sustainer could be somewhere between 30\" and 36\" long with the electronics bay at the top.

With the altimeter in the nose and the long booster, it seems that stability won\'t be a problem. So the fins could be reasonably small.

Some things I am concerned with.
- reliably igniting the second stage. I\'m going to go back through Boris\' article on clustering.
- recovery if the second stage fails to ignite. Part of the reason for carrying the altimeter for deployment.
- lots of joints in the rocket (booster recovery, booster/sustainer, and sustainer recovery).
- strength of the BT-80. It is a pretty light-wall tube, but something like the LOC tubes seems overkill (and gets heavy fast).
- dealing with the motor blast from the sustainer during separation.

What do you think?

Thanks,
David

Hello,

Ah, that makes sense.

From a brief look at the Raven, it has 4 programmable outputs. So a single unit in the sustainer could be used to light the sustainer, separate at apogee, and deploy the main. That would save the weight of a separate unit and battery in the booster as well.

Howard, is that what you are intending to do? If I recall, both of the Aerotech birds have 29 mm mounts? I look forward to seeing how it goes.

Thank you!
David

Hello Howard,

I have been looking at how to modify my design to carry the Raven and use it for both deployment and ignition of the sustainer. It seems that it needs to be firmly attached to the lower body tube or it presents problems getting the igniter wire down to the motor. Doing so means I can\'t use the motor ejection charge as a backup, but it looks like a second ejection charge could be wired up to the Raven as a backup. Impressive little device.

It seems that you could easily reach 2500\' with that combination of motors. Are you setting up for dual deployment? With two compartments? How are you getting the igniter wire down to the motor?

Sorry about all the questions... but I\'m very glad someone else is working on a similar project.

David