Venting Parallel Boosters

[MetMan]

Hello everybody,

I'm building a rocket which will use two parallel BT-55 boosters. These will be fixed and I'm not planning to use them for recovery.

- Do I need to vent them? (I'm thinking yes!)

- Is a subtle 1/4 inch hole in each sufficient for A-B-C engines?

Thanks!

MetMan

 

[flying_silverad]

I would think at least 2 would be better. Possibly 4. I also would paint the inside of the tube area with epoxie to keep it from charring. You could make neat little shrouds to for the vents...

 

[Ryan S.]

good idea with the epoxy, the tube will get worn fast I saw someones Gemini DC with two holes in the side pods because the ejection charge was vented straight out and most of the force would hit the side pods

 

[Silverleaf]

This is a great topic !

I've been considering asking the experts here about their efforts with venting.

I have an idea in regards to having a centralized motor, with a vent tube running back down to the rear of the rocket, which could be used for a number of reasons:

1) To eject a rear-mounted chute

2) To be used to activate a spring-device that would cause fins to drop into a non stable flight - causing a tumble recovery

3) To activate a spring mechanism that would cause the rocket/object to become a gliding body.

In part, my question deals with just how much of a bent tube could I use ?

Could I indeed create a tube attached to the front of the MM that would literally loop in 1/2 and run parallel back down beside the MM to the bottom of the rocket ?

What materials would be best for such a design ?

What glueing options would be best ?

Would an aluminum sleeve, or similar material, be able to be used, without making the rocket illegal

All based on B to D size engine mounts...

 

[Zippy]

I hate to ask the obvious, but why not just use plugged motors?
Granted not a lot of choice in plugged rounds but enough to do the job since their just fixed boosters anyway eh?

 

[Silverleaf]

Well, suffice to say that I'm thinking about a type of launch pad-platform that will lift off, and as it reaches apogee, the platform fins will snap upwards, to form the flat top, causing it to float back down..or thereabouts.

Its not a huge project, just something to occupy my time while i wait on projects to dry, and drawings to print out..

 

[Zippy]

SilverLeaf,

Yes what you'r looking at is more complex and maybe you need an ejection charge but MetMan's glued on booster's could be simplified by just using plugged motors don't you think?

 

[Silverleaf]

Oh geez.. My apologies, I just got over a Cluster headache, and wasn't thinking clearly.

Your right, plugged would work perfectly for Met's dilemma.

*blush*

 

[MetMan]

Plugged motors would be great, but I'm using 18mm mounts and I don't believe there are any current plugged motors for this size. I'm not sure I'm allowed to modify motors by plugging them--probably its own thread, eh?

I like the idea of shrouds around the vent holes. The model is of the sci-fi space ship genre so I could make it fit with the theme.

I had also kicked around the idea of using long delay motors in the boosters and having them deploy supplemental recovery chutes or streamers. I'm not sure I like the idea of blasting a nose cone into a deployed recovery system, though...

MetMan

 

[Chr$]

Use a C6-P

"A C6-P???"

You can make a C6-P one of two ways:

1. Wrap foil tape over the top and around the top of a C6-0 ensuring that you seal it.

2. Pour 1/8 inch of epoxy in the top of a C6-0 to make a little cap. Give it a few days to cure. (This works best)

Of course, this would constitute modifying a motor, and you could only fly it at an EX launch.

You can also design your MMT tube to have a closed top. Use some foil tape to line the top of the MMT tube. You still use a dash-0 motor, but it is not "modified" this way.

 

[powderburner]

Or you could leave the motors alone in the side-pods, and simply build those pods with a plug or solid disc just ahead of the motors. Do not tape up the motors tightly (use only enough so they don't slide out) and let them leave when the ejection charge fires.

Silverleaf, I think you may be trying to make things harder than they need to be (and I am a certified expert at doing exactly that). Maybe just vent the main ejection charge into a small chamber, plugged/blocked/sealed front and rear, and vent the chamber out the rear through a small-diam piece of regular BT?

 

[prowlerguy]

Using the KISS priciple, what is wrong with this?

Since he is using BT55 to hold 18mm engines, why not just take slices out of the CRs, leaving enough material to hold the MMT in place and also leaving enough gaps for the gas to escape aft. Just seal/plug the top, and you have no moving parts, no extra tubes, no ejected engines, and the gasses venting will add a small amount of thrust.