Ballistic Approach Recovery

next saturday, here in Quebec someone will lauch this rocket with a very special recovery system have a look here



https://www.youtube.com/watch?v=L8ntuUXfYoM

That is rather different, cool, but different.

Obviously believes passionately in 'rear deployment'. I hope he's using eleventeen bazillion pound rated kevlar straps. It could work!

This give me an idea to not use Black Powder for the main chute, but an Arduino with 1 or few servo, on an electro magnet to open the lock of the altimeter bay and the main chute. Since the drone is already pulling , you don't need ejection charge, I will see this week end, and work on my Arduino idea this winter, this and something else I reserve for another tread.

Was I supposed to be wearing a pair of these for that video?

I think he is going to have a long walk... He is relying on a couple shear pins to support the entire rocket while the drogue deploys. My feeble mind believes that he will shear the pins early and end up with apogee deployment of the main, especially if his delay is off....

LW Bercini said:

Was I supposed to be wearing a pair of these for that video?

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yup!-I just thot my blood sugar was really low......

LW Bercini said:

Was I supposed to be wearing a pair of these for that video?

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I have some of those glasses and all they did was clean up the video. No 3D speshul effex......

LW Bercini said:

Was I supposed to be wearing a pair of these for that video?

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Or just turn off the "3D" in the settings panel of the video...

T-Rex said:

I think he is going to have a long walk... He is relying on a couple shear pins to support the entire rocket while the drogue deploys. My feeble mind believes that he will shear the pins early and end up with apogee deployment of the main, especially if his delay is off....

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+1 to that. Shear pin calculation and balancing between force needed to hold during drogue versus force needed to shear during main deployment is probably too fine line to navigate repeatably/reliably.

I don't know why the thrust isn't transferred to the rear of the airframe directly instead of through that "drogue tube". Sounds like a recipe for tangling.

Unless there's something to prevent the ebay from wanting to move foward, when the drogue charge fires, it's going to snap the shear pins and push the ebay forward, as well as throwing the motor mount backwards.

In addition, on motor burnout, his motor mount may begin to fall out of the airframe, prematurely.

All told, it's an interesting idea. I'd love to see it in person.

-Kevin

troj said:

Unless there's something to prevent the ebay from wanting to move foward, when the drogue charge fires, it's going to snap the shear pins and push the ebay forward, as well as throwing the motor mount backwards.

In addition, on motor burnout, his motor mount may begin to fall out of the airframe, prematurely.

All told, it's an interesting idea. I'd love to see it in person.

-Kevin

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This is why my idea of electro-mecanical lock insted of BP will be great, no shear pins, O scale trains work with electric coupler, this is an adaptation of that I want to use. I'm in this hobby to try new things.

Interesting idea. I too think the shear pins might be the weak link. I was thinking maybe a cable cutter would be better way to release the ebay and main chute.

I wish him luck!

Derek said:

Interesting idea. I too think the shear pins might be the weak link. I was thinking maybe a cable cutter would be better way to release the ebay and main chute.

I wish him luck!

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Also I was thinking of the cable cutter to release the AV Bay.

I am curious what motor this will be flown with the first time, and the altitude it sims to.

The other thing that comes to mind is whether or not the motor thrust is directed onto shear pins. If so.....oops!

Though, if I remember correctly, in the video he says something about a thrust ring up at the top.

I'd love to get my hands on the rocket, and look it over.

-Kevin

BLKKROW said:

I am curious what motor this will be flown with the first time, and the altitude it sims to.

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a CTI 867-J244 the rocket is a 3" dia, 71" long and weight 2,60 kg. He will use a droge of 24" and a main of 40"

Many moons ago Nick @ Aerosleeves had a rocket like this. It was high performance and it came down ballistic to 5,000'. Then he had the fincan and the airframe separate at that point with a lot of cord. at 1,000' the main deployed. It worked more than once, I recollect. He was proud of it - I've always wanted to do something similar.

Edward

Area66 if you will be witnessing the launch please keep us updated.

BLKKROW said:

Area66 if you will be witnessing the launch please keep us updated.

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I will take pic.

What's to keep the relatively heavy motor mount from being pulled out of the back by deceleration after burnout? Sounds like it may pull out the drogue immediately after burnout, especially on a J with a light rocket...

CarVac said:

I don't know why the thrust isn't transferred to the rear of the airframe directly instead of through that "drogue tube". Sounds like a recipe for tangling.

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cerving said:

What's to keep the relatively heavy motor mount from being pulled out of the back by deceleration after burnout? Sounds like it may pull out the drogue immediately after burnout, especially on a J with a light rocket...

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The deceleration after burnout is caused by drag pushing on the front of the airframe. The motor would absolutely love to keep moving forward, but the airframe has drag pushing back on it. The motor is trying to go forward quickly, but the airframe is trying to slow down, so they stay together.

The Cable cutter for releasing the AV-bay is probably the only thing I would change. Does his motor mount come down by itself on its own parachute? Or is it attached to the drouge? He had alot of shear pins... I sure hope they all snap, and snap when he wants them to. The worst I see happening is the rocket deploying the drouge and main at apogee.

I have always wanted to do this also. A rocket coming in ballistic comes in far closer to the pad, but is obviously a bit more dangerous. I'd always call it in as a heads-up flight, just so that people are aware if something bad happens.

The other way I see to do this is with reefing lines and a cable cutter. Simply deploy the main chute almost entirely reefed, then pop the reefing cable off at main deploy altitude. Of course this works non-ballistic as well, but it gets rid of the need for the flying AV-bay.

It's not often that a completely new recovery idea comes along and most ideas are just wild imagination thrown about however this is the first time in a while I have seen a new idea that appears to have a decent chance of working. Sure hope he's done plenty of ground testing.

I wonder with the relative denser motor will fall faster than the relatively light and airy airframe thus will create a situation with the drogue near the motor that they will descend flat rather than nose first as intended. This will be interesting to see what happens.

-Dave

DAllen said:

Sure hope he's done plenty of ground testing.


-Dave

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I don't think so , but since I like the idea, I will also make testing in the same direction, but I want to use electro-mecanic devise instead of shear pins and BP

When Nick did this years ago - the one thing he always worried about was stripping a chute/some malfunction because then you'd be tossing out the main in a configuration that was purely ballistic. You'd toast everything when it comes out. With traditional drogue at apogee - your speeds should be much lower and you aren't trying to stop a moving train.

Edward

I wonder if you could pre-sew a single piece of thread through a kevlar shock cord. The thread would snap, absorbing energy, and these loops would snap until there was not enough momentum to break the next loop.

Kind of like shock cord shear pins, and absorbent in a way that wont snap back and bite you. You could do away with the entire drouge in this case...

In fact, you could realize this with a bunch of snap-buttons like you have on coats and things, mounted to a nylon or kevlar strap. That way it is reusable.

awseiger said:

I wonder if you could pre-sew a single piece of thread through a kevlar shock cord. The thread would snap, absorbing energy, and these loops would snap until there was not enough momentum to break the next loop.

Kind of like shock cord shear pins, and absorbent in a way that wont snap back and bite you. You could do away with the entire drouge in this case...

In fact, you could realize this with a bunch of snap-buttons like you have on coats and things, mounted to a nylon or kevlar strap. That way it is reusable.

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People use masking tape, electrical tape or rubber bands for this exact purpose. Easier than sewing thread.

Edward

Area66 said:

I don't think so , but since I like the idea, I will also make testing in the same direction, but I want to use electro-mecanic devise instead of shear pins and BP

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I keep trying to come up with an eletro-mechanical solution to ejecting parachutes too. It seems there has to be a more elegant way (but certainly not as cool) to deploy a chute than using an explosive.

AlphaHybrids said:

People use masking tape, electrical tape or rubber bands for this exact purpose. Easier than sewing thread.

Edward

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Yup, works very well with non-elastic shock cords.