Chute recovery on gap-staged booster

[Murdnunoc]

I have a 1.6" BFR/Starship I'm trying to get built up. I didn't know you could stage over a long gap until I saw another thread where a rocket staged over a 14" gap and used the sustainer's pressure to both separate the stages and push a chute out of the booster using a rear ejection system.

I've based a design off this system, but would love to adapt it to get the chute out the front of the booster so it comes down right side up, if possible.

I'd like to use simple staging rather than electronic ignition. I have vent holes at the top of the booster's motor tube, and in the centering rings all the way down the back of the rocket.

Any thoughts on getting a chute to come out the top of the booster?

 

[neil_w]

The motors (both booster and sustainer) are worrisomely recessed inside the body tubes. Looks like a good candidate for the Krushnic effect. Any reason they're so far in there?

Sorry I don't have any good suggestions for deploying a streamer or parachute out of there.

 

[Murdnunoc]

I've only read a little bit on the Krushnic effect, but the little I've seen leads me to understand there's only a problem when they're recessed over one body tube width.
I was actually going for a little increased stability since I'd also read that you can gain some stability by having them recessed, just not too far.
But they could move if needed.

 

[Murdnunoc]

With a little more research, I did find this setup.


I might try surrounding the extended booster motor tube with coupler, and have the chute tucked up between the motor tube and coupler. That way the chute would be contained in the booster rather than having to pull out of the sustainer past the engine plume.

 

[BABAR]

I did a rocket recently where I put a pod on the sustainer with a chute attached to the booster.
16” gap.
The rocket functioned as designed......but the shroud lines all ripped out of the chute.

I SHOULD have expected it.

Think about a single stage black powder rocket. The delay charge puts out smoke without significant thrust, allows the rocket to slow down so hopefully some time close to ejection charge firing is traveling at a low velocity so the shock cord can take up the stress.

Now think about multistage. with Black powder you do not have (nor do you WANT TO HAVE) any delay. So separation occurs at high velocity, which is exactly how you do NOT want to deploy a chute.

Streamers on the other hand are more forgiving.

They don’t give you as much recovery slowing as chutes, but you may not need it. If your booster engine sticks out the back a bit, and The back ends of your fins sweep forward, a streamer out the front may enough to slow the puppy down, lands on the engine casing, and you should be good assuming booster isn’t too heavy to begin with—- should be just three or four fins, and empty tube, and a motor casing.

 

[Murdnunoc]

Sobering scenario. And also completely legit. I hadn't thought about the deployment speed.
Looks like the only way to deploy a chute on the booster would be with a chute release, or a separate, timed ejection on the booster chute.
I had hoped to do the Super Heavy booster fins the same as the Starship fins, which would make them very delicate. But with the higher landing speed that will be needed to avoid shredding a chute, I better go with Lexan fins that don't extend behind the body.

Thanks for the reality check, Babar.

(... maybe a tough, little chute??
That way it still looks a little more scale!)

 

[BABAR]

Sobering scenario. And also completely legit. I hadn't thought about the deployment speed.
Looks like the only way to deploy a chute on the booster would be with a chute release, or a separate, timed ejection on the booster chute.
I had hoped to do the Super Heavy booster fins the same as the Starship fins, which would make them very delicate. But with the higher landing speed that will be needed to avoid shredding a chute, I better go with Lexan fins that don't extend behind the body.

Thanks for the reality check, Babar.

(... maybe a tough, little chute??
That way it still looks a little more scale!)

How committed are you to scale?

https://www.rocketryforum.com/threa...rt-sustainer-15-gap-stage-paint-scheme.60249/

There are a number of black powder solutions. The above has been my go to technique for long gaps and has worked pretty well.

 

[Murdnunoc]

Oooh, I like that rocket. It doesn't want your eyes to focus on any given part. And I like the planning that went into making it go off right.

Looks like the 3 tube setup has the advantage of three individual bodies for the booster and ejection operations. I'll have to see if I could work up a way to get one or two engines into a cluster around the main to drive the ejection operation, all within a single body tube.

 

[Murdnunoc]

Hmm...
The 13mm ejection engines won't share the body tube, even if I were to go from the planned D12 down to an 18mm C engine.

Here's the only setup that would allow a booster engine and an ejection engine in the same tube. 2x C6-0 and 1x C6-5ish

 

[BABAR]

Symmetry is over-rated.
Put the 13 mm right next to the 18 mm. MIGHT be able to do it with the 24.....
Yup, your 18 or 24 mm will be off center a tich. It’ll fly fine.
You can eithr choose to do the same with the sustainer so they match, or angle your internal chimney motor mount so it will be on center where it mates up with booster.

 

[kuririn]

Anybody thought of using good old fashioned safety fuse to pop a delayed ejection charge? Would be similar to dual deploy but instead of electronics firing an igniter in an ejection canister it would be a fuse, one end in the canister and the other in the stream of hot blowby gasses. Varying the length of the fuse will vary the delay time, according to the burn rate. The "canister" can be something as simple as a cut off latex glove fingertip.
There's a guy on eBay that periodically lists safety fuses of varying dia. and burn rates for sale.
And here's a link to a very dated kit that uses a fuse to ignite a delayed motor "retro rocket":
https://store.heavenlyhobbies.com/01-024-0001.html
Access could be as simple as a tube on the back with a removeable plug.
Just an idea.

 

[Murdnunoc]

24mm D + two mini engines fits into the BT-60 booster tube when the 24mm engine is offset.
I like having two ejection engines when set up in cluster, just in case one doesn't ignite. And if the two mini engines fired, but the main failed, it probably wouldn't even get off the pad before harmlessly ejecting. So seems a safe setup.

I'm also liking the simplicity of the fuse to a charge.

With either setup, I'm going to have to figure out a chamber for the chute that seals it to either the ejection engine chamber outside the main booster motor tube. Otherwise the ejection pressure could blow right past the chute.
Maybe a centering ring with a big slot cut out going to the chute chamber.

 

[Wallace]

I did a rocket recently where I put a pod on the sustainer with a chute attached to the booster.
16” gap.
The rocket functioned as designed......but the shroud lines all ripped out of the chute.

I SHOULD have expected it.

Think about a single stage black powder rocket. The delay charge puts out smoke without significant thrust, allows the rocket to slow down so hopefully some time close to ejection charge firing is traveling at a low velocity so the shock cord can take up the stress.

Now think about multistage. with Black powder you do not have (nor do you WANT TO HAVE) any delay. So separation occurs at high velocity, which is exactly how you do NOT want to deploy a chute.

Streamers on the other hand are more forgiving.

They don’t give you as much recovery slowing as chutes, but you may not need it. If your booster engine sticks out the back a bit, and The back ends of your fins sweep forward, a streamer out the front may enough to slow the puppy down, lands on the engine casing, and you should be good assuming booster isn’t too heavy to begin with—- should be just three or four fins, and empty tube, and a motor casing.

Yup, did exactly the same thing using 0 delays. High speed deployment zippered the pod tubes..Even with small mylar streamers. A short delay would be nice but doubt you'd find one short enough?

 

[Murdnunoc]

Yup, did exactly the same thing using 0 delays. High speed deployment zippered the pod tubes..Even with small mylar streamers. A short delay would be nice but doubt you'd find one short enough?

The Estes D12 has a 1.6sec burn time.
1/2A-3 motor with less than 1/2sec burn would give about 3 seconds delay between staging and booster recovery deployment. Seems about right??

And a fuse to a charge could give variable delay depending on fuse length.
My main struggle with the fuse idea is that the starter end of the fuse would have to burn through the booster motor tube wall, which could wear it out quickly. Reloading the fuse and ejection charge could also prove troublesome. Maybe with some design playing I can get it where the fuse and hare are accessible from the bottom of the parachute compartment at the top of the booster stage.

 

[Wallace]

My comment was relating to booster recovery deployment. With a "0" second delay (booster motor) you cannot avoid high speed deployment. But, since they tend to stage really low, the shortest delay "sustainer " type motor will probably deploy your gear after it's already on the ground. This is in relation to side pods only, I'd never reccomend a motor with a delay to light fhe sustainer, totally not safe. Follow?

 

[Murdnunoc]

My comment was relating to booster recovery deployment. With a "0" second delay (booster motor) you cannot avoid high speed deployment. But, since they tend to stage really low, the shortest delay "sustainer " type motor will probably deploy your gear after it's already on the ground. This is in relation to side pods only, I'd never reccomend a motor with a delay to light fhe sustainer, totally not safe. Follow?

Open Rocket has this thing staging at around 400'. With the additional gear to make this thing recover, weight will go up and that altitude will come down, I reckon.
One unknown is how long the booster will be in "coast" phase. I'll do some careful looking at the simulations to see how long it coasts after staging. Be nice to time the ejection, whether from fuse or separate ejection motor, to eject around the booster's apogee, whether that occurs a second after separation, or five seconds after.
Since the ejection motor will start firing at the same time as the booster, and since it has a quick burn time, it will already be a second into its delay when the booster motor stages. With A10-3, that leaves 2 seconds between separation and booster recovery deployment. Maybe about right?
If I need quicker, I could always run 1/2A3-2T for a real quick ejection.

 

[BABAR]

But, since they tend to stage really low, the shortest delay "sustainer " type motor will probably deploy your gear after it's already on the ground. This is in relation to side pods only, I'd never reccomend a motor with a delay to light fhe sustainer, totally not safe. Follow?

First, totally agree that for nonelectronic black powder staging, you must have a zero delay motor in the booster to ignite the sustainer (or next booster if you go over 2 stages).

Second, however, I disagree that adding a delay motor will not deploy the recovery device until the booster is already on the ground. Surprisingly I have found an A8-3 on my booster “side pod” kicks out the chute in time to deploy the chute before the booster falls very far and before it picks up much velocity. My booster motors have always been C6-0 or D12-0, staging I am guessing between 100 and 400 feet. I think the shortest delay you can get on Estes is 2 seconds (?B6-2?). Your 1/2A3-2T would probably be fastest.

The reliability factor is that your booster is a cluster, if you don’t get both engines to light, it tends to be a bit entertaining.

 

[Wallace]

Ok, you got it. Odds are that booster's gonna slow down pretty quick. A 2 second delay might just be perfect. Or not...

 

[Wallace]

Only one way to know for sure.

 

[BABAR]

Crossing posts. If separation occurs at 400 feet you will be fine if chute comes out 2 or 3 seconds later.

 

[Murdnunoc]

The reliability factor is that your booster is a cluster, if you don’t get both engines to light, it tends to be a bit entertaining.

My guess is that a D12 booster, and two 1/2A3-2T for ejection, will be the most bomb proof setup for a cluster.
If the main D doesn't go, the minis won't lift it and just eject on the pad, but no sustainer ignition.
If one of the minis fails, the other mini should still be able to run the ejection event.
Only disaster would be if the main fires, but both mini engines fail. Then really high and no chute!

 

[BABAR]

Agree.
I had a D12-0 / A8-3 combo to D12-3
51" gap total length of stack about 6 feet
Only the A lit
Was JUST enough to get it off the rail

Then came down tail first and leaned drunkenly on the pad

Then the booster chute deployed.
Since the main never fired the sustainer never lit or separated

 

[Murdnunoc]

Here's a question regarding the actual staging ignition:
Can I reduce the 24mm booster engine tube down to 18mm midway up the booster?
The sustainer is an 18mm motor, so going to need to do that at some point anyway, but does there need to be the volume of the 24mm tube all the way up to where it meets the sustainer motor?
Reason I'd like to is that an 18mm inner tube would allow more room for a parachute bay inside the booster.

 

[mbeels]

Then came down tail first and leaned drunkenly on the pad

Then the booster chute deployed.

That would have been entertaining, specifically my 4-year old would have loved that.

 

[BABAR]

Here's a question regarding the actual staging ignition:
Can I reduce the 24mm booster engine tube down to 18mm midway up the booster?
The sustainer is an 18mm motor, so going to need to do that at some point anyway, but does there need to be the volume of the 24mm tube all the way up to where it meets the sustainer motor?
Reason I'd like to is that an 18mm inner tube would allow more room for a parachute bay inside the booster.

Absolutely. The 24mm ejection charge does tend to toast the smaller 18 mm tube for the first couple inches. I roll up a segment of aluminum can inside. The inner tube works like a chimney to duct the gas to your next stage.

 

[Murdnunoc]

I'm really excited to take this thing to the next level. Thinking I have enough info in my head to start putting parts together.
If anything doesn't fit, I'll scream here first!
And if any other details, thoughts or red flags pop into mind, I'd love to hear about it.
Thanks, all, for the guidance.
I'll post progress as it fleshes out.

 

[Murdnunoc]

So now this...


Is starting to look and feel better than either of these...



My mind has a little harder time underrating the symmetry when the main engine is all the way against the wall. And I just don't believe a C6 could do the job on its own.

A cluster of one C6-0 and two C6-3 would give more thrust than a D12, and a longer burn time.
I could still throttle it down with a CBB cluster.
All while maintaining that sweet, sweet symmetry!

 

[Murdnunoc]

Deleted. Double post.

 

[dhbarr]

24-18-13 Drillinge ?

 

[Murdnunoc]

24-18-13 Drillinge ?

Say again? Not following.