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physwil90
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Is there an equation for the rate of heating on a surface at any time, and at any angle?
That's usually the worst in transonic regime. An estimate from simple ballistics is all he really needs. Not that it's going to account for nearly everything, but he's not building a jet fighter.rcgldr said:I'm not aware of anything simple that is accurate. The mathematical models are usually empirical (based on actual experiements) and complex. It's a combination of friction and compression. At hypersonic speeds, it's mostly due to compression.
That's a transonic shock. The plane forcing its way through air acts like a venturi, so the air speeds up every time the fuselage gets thicker. That means as you gradually build speed, shock waves will first form off the widest part of the plane. That's what they usually show off at air shows.rcgldr said:Image of a f22's shockwave:
http://rcgldr.net/misc/f22.jpg
Are you building an interceptor SAM that's supposed to outrun planes going Mach 3.5? These things can go up to Mach 5. Yes, one of these will have supersonic flow behind primary shock wave. It will result in secondary shock wave around the fins. And that will generate huge amounts of heat.physwil90 said:Furthermore, I have a raytheon design guide on missile design and I am using as a reliable reference for this rocket. In this guide it states that "the highest heating rates on the missile are typically associated with stagnation heating...these include radome/nosecone tips (stagnation point), and control surface (fin) leading edges (attachment line, or stagnation line for control surface with no sweep)." (This is for all missiles, sub and supersonic) This statement leads me to believe that there is significant heating on the fins...
True, but the rocket will have to transition through this speed.K^2 said:That's a transonic shock.
I would assume that balsa would self destruct at high speed due to flutter issues, probably well below mach 1. I thought high speed model rockets would be made of composite (fiberglass, carbon, kevlar) materials or metal.So your fins will never experience anything over Mach 1, and heating from Mach 1 isn't bad enough to damage fins if you make them from balsa. Not that balsa is a good material here, due to problems with transonic.
My reply in the first thread he started:rcgldr said:True, but the rocket will have to transition through this speed.
K^2 said:In supersonic flight, fins will be in sub-sonic flow due to the shock produced by the nose. So you only have to worry about supersonic heating on the nose cone.
When punching through transonic, you might have supersonic flows forming around fins, but hopefully, your rocket will punch through transonic region fast enough for it not to be an issue.
rcgldr said:I would assume that balsa would self destruct at high speed due to flutter issues, probably well below mach 1.
That's where the effect is the worst. Though, yes, it might become a problem even earlier.K^2 said:Not that balsa is a good material here, due to problems with transonic.
Composites, most likely. I'm not sure if use of metals is actually illegal anywhere, but it certainly frowned on, and violates NAR member rules. If the engine explodes, and everything is made of plastics, no big. If there are metal shards, it's a different matter.rcgldr said:I thought high speed model rockets would be made of composite (fiberglass, carbon, kevlar) materials or metal.
Not generally. K^2 tried to use plane wings to explain. I'll use use laminar verses turbulent flow.physwil90 said:Is there an equation for the rate of heating on a surface at any time, and at any angle?
physwil90 said:First off, I do not understand why you are saying that the fins will be in a subsonic airflow and how this affects it being cooler. And secondly, I would be inclined to think that the heating on the fins would be greater than the rest of the rocket because they are protruding from the rocket. This leading edge will contribute to high localized aerodynamic heating and so I think the heating will be significant...
Aerodynamic heating is the process of heat transfer between an object and the surrounding air due to high speeds and frictional forces. It is a major concern for objects traveling at high speeds, such as spacecraft, missiles, and high-speed aircraft.
Aerodynamic heating is caused by the conversion of kinetic energy into thermal energy due to air resistance. As an object moves through the air, it experiences frictional forces which generate heat.
The rate of aerodynamic heating is calculated using the following equation: Q = 0.5 * ρ * V^3 * C * AWhere Q is the rate of heating, ρ is the density of the air, V is the velocity of the object, C is the aerodynamic heating coefficient, and A is the surface area of the object.
Aerodynamic heating can cause significant damage to spacecraft, as the extreme temperatures can melt or damage the outer surface of the spacecraft. It can also affect the performance of the spacecraft's systems and instruments.
Aerodynamic heating can be managed through various methods, such as using heat-resistant materials, designing aerodynamic shapes to minimize friction, and using cooling systems to dissipate heat. Extensive testing and simulation are also used to ensure that spacecraft can withstand the high temperatures caused by aerodynamic heating.