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Model Rocketry Discussion Thread

ZodiaK

By ZodiaK
in Science & Spaceflight

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Budgie

Budgie

Posted
Posted
/me looks at necro rule... eh not old enough yet for that to kick in...

Also i am longingly looking at the Ultimate Endeavor from PML... https://publicmissiles.com/secure/kits.asp?groupid=6

That's a really nice looking rocket, but it'll cost a fortune per launch, if you're clustering what it suggests to cluster.

All the same I want one too :)

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Exosphere

Exosphere

Posted
Posted (edited)

I've managed to find a place to conduct static tests, and I've tested a few r-candy motors I've made. I've decided to try out a GALCIT end-burner, but I've come up against a minor problem -- the acquisition of bitumen. I've found plenty of places to buy asphalt cement, but that's mixed with chunks of cement, so unless I can extract the bitumen, it's of limited utility. A friend of mine had a bucket of partially used asphalt cement he was willing to give to me, and I've tried extracting the bitumen by boiling it in water with hydrogen peroxide as a solvent (a technique that's kinda-sorta similar to a method of extracting bitumen from tar sands, which is why I decided to use it), and I've managed to get a small amount from that, but the procedure is rather long and inefficient and it would be easier to just buy pure bitumen. Does anyone know where I could get some?

Also, does anyone have any experience with asphalt/KClO4 rocket motors? I'm thinking about using them because the high regression rate might allow me to make an end-burner and because it's got a specific impulse higher than r-candy propellants, but any other information regarding that type of propellant would be greatly appreciated.

Edited by Exosphere
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Exosphere

Exosphere

Posted
Posted
Exo even with a GLACIT motor i would still think coring would be a good idea... gives you are surface area to play with

Yeah, I ran a few calculations on the thrust of a theoretical GALCIT end burner, and came to that conclusion. Even assuming a propellant density unrealistically close to theoretical, an unrealistically high Ve, and a burn rate much higher than I'd be likely to achieve (even after doping the propellant with Al/Fe2O3/other burn rate enhancers), the thrust produced by such a motor would not be great enough to propel a rocket larger than about two or three inches in diameter without resorting to a very short motor, which would significantly reduce the propellant fraction of the rocket.

The problem is that even with no burn rate enhancers, GALCIT burns at about one inch per second. In a cored design, this would tend to give a very short burn time (relative to an r-candy rocket). This would indicate a very high TWR, which would cause pretty significant drag losses.

Because of this issue, I figured it would be better to either stick with r-candy or APCP. Since the former is less expensive than the latter, I think I'll just stick to r-candy.

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  • 3 weeks later...
tg626

tg626

Posted
Posted (edited)

2 of mine from years ago. The V2 was made from an Estes comet, which was its self a remake of their older v2!

Estes-Comet-V2.jpg

Estes Comet (of the time, now discontinued, I had to glue the die cut balsa fins back into complete sheets and then cut the V2 fins from them, shorten the body tube, and smooth off the "cockpit" details from the nose cone)

mods_silver_comet01.jpg

Edited by tg626
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Budgie

Budgie

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Its a Madcow Level 2. I've basically finished it, just need to sand down the fillets and finish the avionics section. Oh and paint, paint is important. I'm looking at launching it early next year, as soon as the local club releases their launch dates I'll know

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Beowolf

Beowolf

Posted
Posted

Back around 1972 I had a Vashon Valkyrie freon-powered rocket I adored. It was so much cooler looking than the little cardboard toys I'd launched before!

It lost a fin on its maiden flight, flew off in a wide parabola, and was never seen again. :(

Forty years later I still feel sick inside when I remember.

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