Question about side boosters

[user 32360]

Hello fellow rocketeers,
I'm currently interested in building a multi stage rocket (2 boosters on the sides and one main engine) however I have some questions about the process. How would the 2nd stage (middle) engine ignite in mid air after the boosters have fallen off? And also, how do the boosters fall off the rocket, do I have to redirect the ejection charge somehow to push the boosters away from the main body?
Cheers.

 

[AfterBurners]

You want the side boosters to fall off before the second stage ignites if using black powder motors? As far as the side boosters separated they are to be designed so when the ejection charge pushes the nose cone its causes tben to disengage. Someone else show be able to give more detail.

 

[user 32360]

You want the side boosters to fall off before the second stage ignites if using black powder motors? As far as the side boosters separated they are to be designed so when the ejection charge pushes the nose cone its causes tben to disengage. Someone else show be able to give more detail.

Yes, I want the 2 boosters on the side to burn up and fall off before the main engine (probably a d engine) starts. So I would like to know how the main engine can ignite in mid-air.

 

[Charles_McG]

You need to use a flight computer. Preferably with some safety limits.
And talk to your RSO if club flying - airstarting the core is unusual.

 

[user 32360]

Ok, are there any flight computer recommendations? Hopefully something that's cheap? And I assume it'll also need it's own electronics bay?

 

[Charles_McG]

Since I can solder, I like the Eggtimer rocketry kits. The Quantum will do an airstart channel with minimum altitude and velocity safety checks. It will fit in BT55 - BT50 if you’re creative. The Eggtimer Proton has more channels for things like pyro or hot wire cutting events to release the boosters. And an accelerometer that can detect launch before the barometer based detection. But fits BT60 or bigger. Either -can- do an Estes igniter, but using an ematch is probably more reliable.
and remember to save the space for a battery. 2S 300-500 mAh >30C Lipo.

 

[user 32360]

Hm, it seems that the eggtimer website doesn't really show what the actual products look like, and they don't have a dedicated website purchase system, they aren't on Amazon easier. Could some simple timer work? I can set the delay to 2 seconds because that's how long the first stage rockets will burn.

 

[Charles_McG]

If you fly with a club, it’s unlikely you would be allowed to fly a clustered-parallel staged rocket with a simple time. It’s not considered safe enough.
There are other options. Try looking at Apogee rockets.

 

[user 32360]

I don't fly with a club, but I do want my rockets to be safe. I'll take a look at what apogee has to offer.

 

[user 32360]

yet I am still unsure about how the boosters separate, I have seen some concepts online that attach the boosters to the rocket on a rail and when the ejection charge is blown the boosters slide off the rocket, is this a good way to separate?

 

[Charles_McG]

I’ve done it that way. That works best when the boosters separate after the rocket has slowed down, so the wind doesn’t catch the chute so hard. But it doesn’t look as cool as separating at high speed. That’s harder to arrange, but can be done.

if you search for threads I’ve started, you’ll find an example of each with my scale space shuttle and Titan IIIe.
But plenty of other people here have more experience than I.

 

[user 32360]

Alright then, thanks so much for your help.

 

[afadeev]

yet I am still unsure about how the boosters separate, I have seen some concepts online that attach the boosters to the rocket on a rail and when the ejection charge is blown the boosters slide off the rocket, is this a good way to separate?

You have a lot of basic questions, yet are pursuing and extremely complex problem with little experience as a guide.
Before things get expensive and frustrating for your, I strongly suggest you start small, and build up your competency one project at a time.

For simple side-booster solution, look here: https://www.apogeerockets.com/Rocket-Kits/Skill-Level-2-Model-Rocket-Kits/Strap-on-Booster-Pods

For mid-flight electronics ignition - you are far from ready, if you can't make sense of the Eggtimer product offering.
Join a club, and ask for advise from folks who successfully fly high-power multi-stage rockets.
Or google and learn on your own.
Or none of the above.

 

[Gramparocket]

This is my boosted design the engines are lit together as a cluster.
The core engine burns longer and the boosters fall away on streamers.
Boosters are a kit you can order from Apogee.

 

[AstroArlo]

Here's a video of a launch of the apogee strap on boosters.



The most difficult part is getting all 3 engines ignited, but not difficult if you have experience with clusters.

The good part is if a side booster engine doesn't ignite, it stays attached to the main rocket and comes down on the main chute.

Only a problem if the main rocket engine doesn't ignite - then either the two booster engines may not have enough thrust to get the rocket off the pad or high enough. If it gets high enough, the booster will come down ballistically since the chute won't be ejected.

I think the most reliable cluster ignition is with clip whips and 12 volt battery. Had more problems with trying to twist igniter wires together.

 

[cerving]

Hm, it seems that the eggtimer website doesn't really show what the actual products look like, and they don't have a dedicated website purchase system, they aren't on Amazon easier. Could some simple timer work? I can set the delay to 2 seconds because that's how long the first stage rockets will burn.

The pictures are on the product pages (https://eggtimerrocketry.com/home/altimeters-av-bay/), and yes, we do not have a cart. That's because about 90% of our customers have pre-sale questions, and we want to make sure they get what they need. You email us your order and/or questions, we get back to you, and when you're satisfied we send you a PayPal invoice. We want you to be happy, and one way to do that is to make sure you don't spend money on the wrong thing.

An Eggtimer Quantum would be able to actuate your booster separation mechanism and ignite your central motor. If there are more events (i.e. booster separation, central motor ignition, first stage separation charge, second stage motor ignition, drogue chute, main chute) then you'll want to use an Eggtimer Proton. It has six outputs and any output can be configured to perform any function.