Composite staging

[JacobD]

Okay so true to tradition we are thinking about building a 4x upscale Sam-x. Having not done high power staging, some questions have come up.

Do the two stages seperate simply off of the motor ignition, or is a small charge used to seperatte booster from sustainer?

If motor ignition is used to seperate the stages, how do you protect the booster couple from the flame as it seperates?

Is it common practice to use redundant timers for sustainer ignition, or is this just overkill?

Any other words of wisdom would also be appreciated, Thanks a lot.

 

[jetra2]

Originally posted by JacobD
Okay so true to tradition we are thinking about building a 4x upscale Sam-x. Having not done high power staging, some questions have come up.

Do the two stages seperate simply off of the motor ignition, or is a small charge used to seperatte booster from sustainer?

It depends, really. If you use a long coupler with a very smooth fit like on Carl Tulanko's Upscale Tres, you can just use the pressure from the motor to have it separate. If you have a bigger booster where you'd have to use a rod-and-tube suspension system to hold it all together, you could use a smaller charge to push them off each other.

If motor ignition is used to seperate the stages, how do you protect the booster couple from the flame as it seperates?

Epoxy. Use a thin layer on the inside of everything, and you'll have an easy to clean area. Just wipe it down with some water or rubbing alchohol and you'll be OK.

Is it common practice to use redundant timers for sustainer ignition, or is this just overkill?

It's normally not needed if you do everything right. If you have an altimeter in the sustainer, and in the event the sustainer doesn't light, the alt should deploy the chutes.

Any other words of wisdom would also be appreciated, Thanks a lot.

I'd recommend you take a look at the pics from Carl Tulanko's Upscale Tres build pics in this HPR forum. You can search the HPR forum at the bottom of the page.

Jason

 

[Austin]

Jacob,

I use "Drag Seperation" on my HPR models. The upper stage fits loose enough over the lower stage coupler to pull of with no resistance, yet it is long enough to hold the rocket in place during boost. When the booster burns out, it immediately begins to slow, while the upper stage having less resistance is litterally flung off the coupler.

A timer is located in the upper stage and is used to start the second stage sustainer motor. I set the timer delay to just after the burn time of the boosters; if the booster burns for 2.2 seconds, I set the timer to fire the upper stage ignitor at 2.4 seconds, as it will take a second or so for the motor to actually ignite. By this time, it has seperated quite a distance from the booster, so the booster should not suffer from burn marks.

As added insurance, I connect a electric match with a small baggie of black powder in parallel to the upper stage ignitor and let the bag hang past the booster and just sit inside the chamber of the seperation coupler. This charge helps the two stages blow apart in case they bind up for some reason...just added insurance.

On larger scale rockets, additional rods and sleeves would be used for additional support during boost instead of just a coupler. PML's website has some good pics of their multistage rockets and setups...you should also look there.

As Jason said, you may find some good info on my latest two stage rocket, which can be found here:
https://www.rocketryforum.com/showthread.php?s=&threadid=5606&highlight=Tres

Moreover, the picture gallery I have put together of its assembly can be very useful and found here:
https://www.rocketryforum.com/ctulanko/album/index.php?dir=tres

It stands just over 9 feet tall. A couple pics of it on boost can be found here:
https://www.rocketryforum.com/attachment.php?s=&postid=126183

https://www.rocketryforum.com/attachment.php?s=&postid=126184

Good luck and keep us posted,

Carl

 

[Papa Elf]

My Super Glotova rocket uses Drag seperation. Yesterday it had a perfect flight where the stage seperated just before the sustainer ignited. This flight used a H242 staging to a H128. I used a G-WIZ three event altimeter, where it senses burnout, apogee, and main at 400.
You can read about it here.

 

[Ray Dunakin]

Originally posted by JacobD
Okay so true to tradition we are thinking about building a 4x upscale Sam-x. Having not done high power staging, some questions have come up.

Do the two stages seperate simply off of the motor ignition, or is a small charge used to seperatte booster from sustainer?

You can do it either way. I usually just let the sustainer ignition blow off the booster.

If motor ignition is used to seperate the stages, how do you protect the booster couple from the flame as it seperates?

Usually I line the inside of the coupler with a bit of fiberglass, mainly to stiffen the coupler but it also protects it. A coating of epoxy or polyester resin would probably protect it just as well.

Is it common practice to use redundant timers for sustainer ignition, or is this just overkill?

Some do, but I don't think it's common. One thing I'd recommend, if possible, is to smear a little pyrogen on the inside of the top grain of the sustainer motor prior to assembly.

BTW, I have some pics and info about staging high power rockets on my site:

https://albums.photo.epson.com/j/AlbumIndex?u=3009006&a=30072909&f=0

 

[Rocketboy25]

Is there a replacement on the market, since thermalite is out of production?

 

[Ray Dunakin]

Originally posted by Rocketboy25
Is there a replacement on the market, since thermalite is out of production?

As far as I know there is no replacement for real Thermalite. There is something similar which is sometimes called "Thermolite" or "Brazilian Thermalite", but it doesn't work the same as the real stuff. Real Thermalite burns almost instantly when confined (as in heat-shrink tubing). The fake stuff doesn't do that, which makes it unsuitable for igniting most composite motors.

That's because the fuse has to be confined to prevent ignition until the flame reaches the top of the motor core. The fuse burns at a rate of 1 inch per second. Most composite motors have core that is several inches long, and you'll rarely need a delay of more than 2-3 seconds.

Real Thermalite is still available but can be hard to find, and usually requires a LEUP for purchase.