How to Safely Recover a NC?

I need advice on how to safely bring down the nosecone of a rocket.

For the rocketry project I'm currently working on, I need to drop a payload at apogee. I think that the best way to do this is to leave the nosecone unsecured; as the rocket tips over after apogee, the payload will slide forward, push out the NC, and both will fall to the ground.

Obviously, I don't want to put anyone in danger, so I'd like to have a recovery device on the nosecone - I'm thinking a big streamer. I'm not sure if attaching a shock cord between the NC and payload section is another option - worried the payload will get hung up on it.

The nosecone is a LOC 2.6" ogive that is 11.75" long (including the shoulder) and weighs 95g.

That seems big and heavy enough to put a small parachute (maybe 12"?) on it. If you're just bringing down the nose cone you don't need a shock cord, so it should pack in there very compactly. I would think a small chute would be simpler to deal with than a large streamer, although the streamer will be more visible.

Thanks @neil_w I was concerned that the nosecone wouldn't weigh enough even for a 12" chute and would blow away in the wind. I agree that it will make packing considerably easier.

Nothing wrong with an appropriately-sized streamer. It's not a readily breakable part, like a fin can.

That’s true, the nose is not a delicate part. Maybe 9” for 95g would be good. Need to check the parachute sizing charts.

JCRL said:

...I think that the best way to do this is to leave the nosecone unsecured; as the rocket tips over after apogee, the payload will slide forward, push out the NC, and both will fall to the ground.
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I don't think you can depend on gravity to push the payload out. When the rocket is descending, everything is in free fall and there isn't any force between components other than small drag differences between the fin can and the nose cone. If the rocket doesn't drag separate at motor burnout, it probably won't on the way back down either. That said, the ejection charge should do the trick just fine. Will you still have the regular parachute on the end of the regular shock cord for the fin can?

JCRL said:

I need advice on how to safely bring down the nosecone of a rocket.

For the rocketry project I'm currently working on, I need to drop a payload at apogee. I think that the best way to do this is to leave the nosecone unsecured; as the rocket tips over after apogee, the payload will slide forward, push out the NC, and both will fall to the ground.

Obviously, I don't want to put anyone in danger, so I'd like to have a recovery device on the nosecone - I'm thinking a big streamer. I'm not sure if attaching a shock cord between the NC and payload section is another option - worried the payload will get hung up on it.

The nosecone is a LOC 2.6" ogive that is 11.75" long (including the shoulder) and weighs 95g.

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Your premise is faulty. When your rocket reaches apogee and tips over it’s unlikely that the payload will slide forward. Gravity is accelerating the entire rocket equally, not just the payload. The payload certainly will not have enough force to push out a nosecone that’s tight enough to avoid drag separation at burnout. If that were true it would be a great way to detect apogee.
Now maybe you meant that you intend to suspend a payload bay beneath a chute and that’s when the payload will slide forward and knock out the nosecone. That could work but it could also happen at burnout. I’ve had nosecones separate at burnout. It’s not pretty.
I think you should secure the nosecone which means you’ll need to eject the nosecone somehow. I’d put a small brightly colored chute on it to help with visibility.

I might be explaining my plan incorrectly (I'm still new at this). The order of events that I have in mind is: ignition > motor burnout > apogee > ejection charge -- at this stage the rocket is in two pieces: fin can and payload+NC with the shock cord and main parachute connecting them. As the rocket is descending in the traditional manner, the 350g payload slides forward and pushes out the NC, and both fall to the ground under their own parachutes. Rocket is recovered in three pieces: Fin Can + empty payload section; payload; nosecone.

[I hope I explained myself correctly this time]

JCRL said:

I might be explaining my plan incorrectly (I'm still new at this). The order of events that I have in mind is: ignition > motor burnout > apogee > ejection charge -- at this stage the rocket is in two pieces: fin can and payload+NC with the shock cord and main parachute connecting them. As the rocket is descending in the traditional manner, the 350g payload slides forward and pushes out the NC, and both fall to the ground under their own parachutes. Rocket is recovered in three pieces: Fin Can + empty payload section; payload; nosecone.

[I hope I explained myself correctly this time]

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You want to pull out your payload with an ejection charge. Like Steve said, you can't rely on gravity or the rocket's position to do that. It has to be a repeatable process.

Also, the amount of force needed to push out a nose cone far exceeds a that provided by a little bump from an object.

How big a rocket/motor are we talking here?

It sounds like you're dealing with a smaller mid power rocket, and you aren't planning on including deployment electronics

JCRL said:

I might be explaining my plan incorrectly (I'm still new at this). The order of events that I have in mind is: ignition > motor burnout > apogee > ejection charge -- at this stage the rocket is in two pieces: fin can and payload+NC with the shock cord and main parachute connecting them. As the rocket is descending in the traditional manner, the 350g payload slides forward and pushes out the NC, and both fall to the ground under their own parachutes. Rocket is recovered in three pieces: Fin Can + empty payload section; payload; nosecone.

[I hope I explained myself correctly this time]

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You'd want to do a bunch of ground testing. If you can make it all work so that the nose cone and payload bay pass the shake test but the nose cone falls off when the payload/nose are held upside down, then it may work. You'll also get a little more oomph for ejecting the nose when the payload bay comes to the end of the shock cord.

boatgeek said:

You'd want to do a bunch of ground testing. If you can make it all work so that the nose cone and payload bay pass the shake test but the nose cone falls off when the payload/nose are held upside down, then it may work.

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The problem is, the loose payload is more likely to pop the nosecone off at burnout when the rocket decelerates and the loose payload surges forward.

JCRL said:

I might be explaining my plan incorrectly (I'm still new at this). The order of events that I have in mind is: ignition > motor burnout > apogee > ejection charge -- at this stage the rocket is in two pieces: fin can and payload+NC with the shock cord and main parachute connecting them. As the rocket is descending in the traditional manner, the 350g payload slides forward and pushes out the NC, and both fall to the ground under their own parachutes. Rocket is recovered in three pieces: Fin Can + empty payload section; payload; nosecone.

[I hope I explained myself correctly this time]

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That’s a better explanation.
You will have three events when the payload might press against the nosecone. The first will be right at burnout when drag decelerates the rocket but the contents such as the payload are not acted upon by drag. Depending on how much drag you have that could be when the nosecone gets knocked out. Not totally predictable. Not reliable.
Next will be when the chute opens. If the chute comes out right at apogee the opening might be pretty soft. The nosecone might come out due to weight, or not. Again, not reliable, but without electronics this is the best opportunity.
If the chute opens fast or late stuff will move and it’s very likely the payload would get shook loose even with a snug nosecone. Timing a chute is voodoo. I wouldn’t rely on it.
Compared to the deceleration experienced when the chute opens the weight of the payload against the butt of the nosecone is minor. That’s the third opportunity. Not at all reliable. If it doesn’t come out when the chute opens, it probably would not ever come out.
I would still recommend a controlled ejection of the nosecone.
If you’re using motor ejection you might skip separating the payload as a separate section and place the payload and main chute ahead of a piston in a single tube rocket. Also the payload chute if needed.

Nytrunner said:

How big a rocket/motor are we talking here?

It sounds like you're dealing with a smaller mid power rocket, and you aren't planning on including deployment electronics

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F motors mostly. The rocket in question is a LOC Graduator that's 40" x 2.6".

You might want to look at the design of a CANSAT carrier.

JCRL said:

Thanks @neil_w I was concerned that the nosecone wouldn't weigh enough even for a 12" chute and would blow away in the wind. I agree that it will make packing considerably easier.

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There are many rockets that have a 12" chute, and they all weigh less than 2 oz (56 grams) which is about half the weight of your nose cone, and they seem to recover fine. 95 grams on a 12" chute will fall pretty fast.

UhClem said:

You might want to look at the design of a CANSAT carrier.

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This is excellent! Thank you for sharing.

I forgot to thank everyone for your comments and to let you know that I'm putting this project on hold until I design a reliable way of ejecting the satellites at apogee.

I don't check in here enough.... I was actually doing this, providing launch services for NMSU's Electrical and Computer Engineering Department senior projects for several years (sadly, they're doing their senior projects differently now, so they aren't supplying me with free motors any more). My requirement was to eject the student payload after apogee, at 1500'.

What I did was basically dual-deploy using the drogue charge to deploy the main parachute at apogee (rear eject) and the main charge to eject the student payload at the programmed altitude.

Up in the forward end, I made a carrier for the payload out of some coupler tubing and a bulkhead, so it was essentially a piston ejection system. The coupler was long enough to hold the student payload. I used a too-short (10 foot? I'd have to measure), 1500 lb Kevlar shock cord, so I could be confident the payload would leave the carrier when it reached the end of its travel. Finally, a couple of 2-56 shear pins made sure the nose cone didn't come off when the main chute deployed. Set the altimeter to eject at 1500' and it worked perfectly.

I'm attaching an openrocket file. Note the spacer below the payload carrier; that was to keep from having the piston rest directly on the black powder canister. Also, the styrofoam spacer in the payload carrier was to keep from having the student payload resting on the the eye bolt at the bottom of the piston.

JCRL said:

I need to drop a payload at apogee.

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Seems like we are overthinking this.

All events required events can occur at Apogee.
Release payload
Deploy rocket body chute
Deploy nose cone chute.

Put a piston in front of the motor.
In front of the piston, from bottom to top, go the rocket chute, the payload, and the nose cone chute, and the nose cone. Make sure piston move easily (consider graphite dry lubricant, if it won’t mess up your payload.)

Ejection charge fires, shoves EVERYTHING out the front. May want to use and external shock cord mount to hold the rocket body chute and the piston. May cut a small “channel” in the nose cone shoulder for cord to pass through.