mach buster type rocket

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bachsta

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im going to be building a mach buster/ minimum diameter type rocket does anyone who has built one before have any tips?
 

Chuck Rudy

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This is being discussed in the scratch build forum by G80Rocketbyoy
 

DynaSoar

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Originally posted by bachsta
im going to be building a mach buster/ minimum diameter type rocket does anyone who has built one before have any tips?
There's too many to list. It'd help to know what you already know. What have you built?
 

bachsta

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ive just built a few estes kits that ive modded myself but what i really want to know is stuff like fin design and diameter to length ratios, nose cones to use, and how to keep it light, stuff like that
 

DynaSoar

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Originally posted by bachsta
ive just built a few estes kits that ive modded myself but what i really want to know is stuff like fin design and diameter to length ratios, nose cones to use, and how to keep it light, stuff like that
The WAC Corporal is a design used very often. Conical nose, clipped delta fins. The GoFast rocket used this design. It went Mach 4.5 or so and 77 miles up. Trapezoidal fins are also good. See the Nike booster or Nike Smoke.

For Mach+ speeds, the fewer the transitions from one shape to another is best. Every transition will form a wavefront. These will interact until they merge. The more there are the more drag. For subsonic flight, having the fins set slightly foward of the aft end is good. For supersonic, not -- it's another transition.

The optimal design would be a cone. Two transitions: tip and aft edge.

Mine is 30" of 29mm motor tube, a PML conical urethane nose and three asymetric trapezoidal fins, with a longer leading edge than trailing; 30 degree angle between body and leading edge, 60 degree between body and trailing. They look like the fins on an AT Mustang. Good, but not best. My next one will use an Acme fin can; trapezoidal fins and all one piece for strength.

Caliber (length:diameter ratio) doesn't matter so much once it's stable.

You don't want it to be as light as possible. It has to have enough mass to fight its way through the Mach wall. I don't know how to calculate the optimal mass.
 

bachsta

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triangle fins seem really popular on high alt. and mach busters are they good too?
 

GL-P

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Mine is 30" of 29mm motor tube, a PML conical urethane nose and three asymetric trapezoidal fins, with a longer leading edge than trailing; 30 degree angle between body and leading edge, 60 degree between body and trailing. They look like the fins on an AT Mustang. Good, but not best. My next one will use an Acme fin can; trapezoidal fins and all one piece for strength.
That's what I use. What's better? Hard question to answer but I'm curious what people tend to use. I find the 30-60-90 shape to be big enough to be stable, the shape is strong on side to side motion and in some computer testing to be very good.
 
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