Will a carbon fiber rod degrade if in the exhaust plume of model rocket engine?

Looking at the latest design contest. Thinking of a MIRB design (Multiple Independent Recoverable Boosters), where the "fins" of the rocket in total make up the "wings" of the boosters, which will recover independently as gliders. Would like to put "tails" of the gliders, displaced posteriorly (AFT, as recent discussion noted). Tails need to be far enough back out of the exhaust plume. Was thinking of carbon fiber midline "spar" connecting the forward engine/body/wings of the booster gliders. The spar would be within the exhaust plume. How does carbon fiber stand up to that kind of transient heat?

BABAR said:

Looking at the latest design contest. Thinking of a MIRB design (Multiple Independent Recoverable Boosters), where the "fins" of the rocket in total make up the "wings" of the boosters, which will recover independently as gliders. Would like to put "tails" of the gliders, displaced posteriorly (AFT, as recent discussion noted). Tails need to be far enough back out of the exhaust plume. Was thinking of carbon fiber midline "spar" connecting the forward engine/body/wings of the booster gliders. The spar would be within the exhaust plume. How does carbon fiber stand up to that kind of transient heat?

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The carbon fiber will likely stand the heat much better than the resin that was used to make the part.

Alternate #1,
Could you just angle the rods outwards a bit and cant the tailfins at an equal and opposite angle. This would make the tail of the glider 'higher' than the fin/wings, but should work aerodynamically. That way the rods are out of the plume and you can use more conventional materials. Of course, that may not be as aesthetically pleasing.

Alternate #2,
You could make them 'spring' loaded (rubber bands) and have them extend (either sliding or unfolding) after separation.

If I knew anything about how CF would stand up to an exhaust blast, I'd answer your actual question, but I don't so I won't. :wink:

mpitfield said:

The carbon fiber will likely stand the heat much better than the resin that was used to make the part.

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+1. You could shield it though.

In my experience, mpitfield is right; the CF will be fine, but the epoxy will not survive. On my Nike-Asp test flight of the sustainer:



"As we got back to camp, I noticed that the back end of the rocket had been damaged by heat. The end of the nozzle is just about flush with the aft end of the sustainer, but apparently base drag had pulled enough of the exhaust heat into the airframe to burn off the fiberglass and epoxy on the inside of the aft end. The carbon fiber was still there, but the epoxy was gone and the cloth was flexible again!"

Will probably go with two carbon fiber rods per booster section glider. The forward attachments to the booster tube will be out of the plume, and the aft attachments hopefully will be distal to the plume (kind of the point.). The distal control surfaces (probably a wide "V" shape combine horizontal and vertical stab) must be oriented just like fins aligned with long axis of rocket as they will essentially BE functioning as fins for the rocket during boost phase (so will the "wings" for that matter.). I think two fuselage rods will help keep alignment better.