SpaceX Falcon Heavy

davdue

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I've been thinking about building a HPR Falcon Heavy rocket. I would like to make it somewhat realistic to the real rocket in that it will separate the boosters from the main rocket. I'm pretty sure I can use the a MissileWorks RRC3 to signal the aux output to fire X seconds after launch. But what do I do with that signal. I thought about exploding bolts but then I have the safety factor of those to be concerned about. I thought about some sort of a solenoid that releases a latch. There is a LPR version on here that plans on having them released when the nosecone deploys from the motor ejection. That's ok but not as realistic. Anybody have any other ideas or suggestions for me?
 

gwh

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I'd try this:
Use mounting hooks that allow for the boosters to push up the center core but are able to fall off freely, then use a solenoid to retract a restraint pin or latch that prevents the boosters from falling off until its been activated. Time it to be ~0.5 seconds prior to booster engine burn out.
There is a decent chance your solenoids wouldn't be able to retract under the loaded weight of the boosters in the event the motors didn't fire correctly.
 

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afadeev

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I've been thinking about building a HPR Falcon Heavy rocket. I would like to make it somewhat realistic to the real rocket in that it will separate the boosters from the main rocket.

I have one under construction that uses an ejection charge to release the boosters.

I have done something similar, using Apogee's parallel booster's hooks and notches setup.
Technically, it should work with HPR rockets as well.

shuttle.jpg

Apogee's kit:
https://www.apogeerockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/Strap-on-Booster-Pods



I'm pretty sure I can use the a MissileWorks RRC3 to signal the aux output to fire X seconds after launch. But what do I do with that signal.

Now you are talking about air-starting the second stage, which is doable, but that's a different problem.
Parallel boosters will burn alongside the main core engine, simultaneously.

Air starts could be used to ignite the second stage, and could be triggered by the the G-shock from main stage end-of-burn. That's how regular 2+stage rockets do it.

I thought about exploding bolts but then I have the safety factor of those to be concerned about. I thought about some sort of a solenoid that releases a latch. There is a LPR version on here that plans on having them released when the nosecone deploys from the motor ejection. That's ok but not as realistic. Anybody have any other ideas or suggestions for me?

I think you need to accept the fact that your rocket will not be a 1:1 scaled replica of the SpaceX FH, unless you also incorporate thrust vectoring for stability control and find ways to loose additional rear fins. FH doesn't have them, but your rocket will absolutely require them.

Nose cone hook release works, and is reasonably realistic.
Anything more complicated will be heavier, more expensive, and more error prone.

a
 

Charles_McG

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Now you are talking about air-starting the second stage, which is doable, but that's a different problem.
Parallel boosters will burn alongside the main core engine, simultaneously.

The OP doesn't necessarily mean that. He could use the airstart ignitor channel to fire a separation charge, pushing off the boosters after their burnout, but before apogee. I'm planning something similar - but using the analogous capabilities of an eggtimer Quantum to cut a line holding the boosters on. (Instead of a BP charge pushing them off.) The boosters then need to have their own deployment ability - motor or altimeter.

More complicated than 'nose-blow', but should avoid the high speed deployment issue that nose-blow boosters can run into if you are aiming for separation during core burn profile.
 

davdue

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The OP doesn't necessarily mean that. He could use the airstart ignitor channel to fire a separation charge, pushing off the boosters after their burnout, but before apogee. I'm planning something similar - but using the analogous capabilities of an eggtimer Quantum to cut a line holding the boosters on. (Instead of a BP charge pushing them off.) The boosters then need to have their own deployment ability - motor or altimeter.

More complicated than 'nose-blow', but should avoid the high speed deployment issue that nose-blow boosters can run into if you are aiming for separation during core burn profile.

Correct that is what I was thinking. I also like the thought of using the Eggtimer Quantum airstart mode. From my real quick reading it looks like I can use the second output to fire a "drogue" the main parachute on each booster for single deploy. Or I can just use motor deploy on those. I would be a little concerned about early or late deployment with that though.

I have done something similar, using Apogee's parallel booster's hooks and notches setup.
Technically, it should work with HPR rockets as well.

View attachment 339828

Apogee's kit:
https://www.apogeerockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/Strap-on-Booster-Pods


I think you need to accept the fact that your rocket will not be a 1:1 scaled replica of the SpaceX FH, unless you also incorporate thrust vectoring for stability control and find ways to loose additional rear fins. FH doesn't have them, but your rocket will absolutely require them.

Nose cone hook release works, and is reasonably realistic.
Anything more complicated will be heavier, more expensive, and more error prone.

a

I will have to look at those hooks from Apogee. I thought I had looked at about everything that they carry. I might be able to use them at the bottom of the boosters with a mechanism at the top to release them after booster burn out.

I definitely will have to use fins so yes it won't be complete replica. The models used in this build have lexan fins. I may do something like that with thicker lexan since this will be a high power rocket. I am thinking 3" with a 54mm core engine mount and 38mm in the boosters. The "Second stage" would be a 4" tube. I won't have an engine in it. But that I could separate at the transition for a dual deploy setup. I need to play around in Open Rocket first. Problem is that the current OR V15.03 doesn't support pods so I can't simulate the boosters. I understand there is a version in work for that though.
 

Charles_McG

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I asked Egg.Cris about doing a servo instead of an ignitor in 'airstart' mode - but he said there weren't enough CPU cycles available during boost phase to reliably generate a servo output.
 

davdue

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I talked to Chris at Egg Timer about a servo as well. He said the same thing about a servo but he did say this: "You CAN have it operate a motor with a gearbox to do the release since that's an on-off function, you can probably just hack a servo and take out the control board. Set the "on-time" for about 2 seconds to make sure it does its thing and you should be fine. I would recommend using a dedicated deployment battery for that, so any power surges can't cause a processor brownout. You probably don't need a very large battery, a little 180 mAH 2S LiPo should do it. You'll want to add a few filter capacitors, such as I recommend for servos." So I think I will try that when I get my first quantum built.

I plan to do a ball and socket type of top latch similar to the real Falcon Heavy. I will use the "servo motor" to operate a latch that holds the booster on the main. I am also toying with a two stage main like the real rocket. I may just go with a single stage for the first version and add a 2nd stage later.
 
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davdue

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I am having another possible problem with the design of this rocket, well at least with the simulation, I am using beta version 17.11-rc2.1 of OpenRocket so I can simulate the side boosters. The problem I am having is that it always gives me an error that the recovery device opened while motor is still burning. I have double checked all of the parachute deployment settings and they all look right. Is this a problem with the beta version? I attached my OR file.

View attachment SpaceX Falcon Heavy - 3 inch.ork
 
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