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Iannovation

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Regarding materials and geometric shape,
How would you mount 3 fins on a tube such that they can rotate in position (for steering) yet be securely mounted to withstand Airspeed of Mach 5?
 

Speaknoevil

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Although I am sure there a few people on this forum that could answer your question, this forum is for upper end hobby participation only, and not guided missle applications. For a deep dive into that subject matter get accepted into an appropriate branch of the DoD or NASA.
 

lakeroadster

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Finite Element Analysis... Or old school long hand Mechanical Engineering calculations.

When it comes to Mach 5..... WWSRD... What Would Speed Racer Do? :D

Mach 5.jpg
 
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dhbarr

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Work your way up to m5, then after you've got the safe-recovery thing handled you can add complications such as turning straighter up.
 

BDB

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The GoFast rocket, the only "amateur" rocket to break the Karman line, hit Mach 5 with slightly canted fins, but they weren't rotatable. I hope I'm wrong, but I don't think anyone in our community has built a rocket with rotatable canards that can operate at those speeds.
 

Mushtang

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You could use balsa wood if you soak it in CA and then give it at least 4 coats of paint to make them strong enough. Then you could mount them on pencils to rotate but you have to go with #4 or higher to withstand those speeds, a #2 pencil would snap in half around Mach 1.

I hope your guided missile works well. Post pictures later!
 

BDB

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For that matter, the canards will only be effective in dense air, I suspect that by the time you hit Mach 5, your project will be in pretty thin air. If you are thinking about a 2 stage rocket, you may want to consider having the canards on the booster or interstage coupler. I suspect that is Jim Jarvis' logic. Check out his thread here.
 
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Andrew_ASC

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You need to find the exact drag coefficient for the exact fin at Mach five. Which is harder than making a rocket go Mach five. Then you compute forces with fluid mechanics. Then this gets into University of Queensland classes on hypersonic flow because you’ve theoretically superpassed my “trivial” mechanical engingeering advanced fluids supersonic flow knowledge. Then you need masters in mechanical or aeronautical engineering to understand CFD. Go find a hypersonic flow expert. I’ve met one Dr. Sreenivas at UTC for computational fluids work he does to Mach 25, he has twenty years experience.

If you are asking these questions you will struggle to hit Mach 5. If just curious. The theory is hard. The practical aspect is even harder. Very few people know hypersonic flow patterns well. I can make a hypersonic airfoil shape. I can’t find a drag coefficient at Mach 5, not smart enough. You start talking of national resources to just wind tunnel something once hypersonic. Private companies have to enter a test matrix with the United States Air Force with a facility like Tullahoma for example which has hypersonic wind tunnels. You’ve exceeded UTSI Mach 4 wind tunnel at this point for real world data.

Forget moveable canards. It’s hard enough with a solid fixed fin. Moving that canard takes a solid background in linkage design. Thermodynamically you’ll want a metal with a higher melt temp than the air temp at Mach 5.
 
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Bat-mite

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You know, the pigeon-shaped robot that came out of the back of the Mach 5 when he pushed button G, and could deliver a message back to Pops at home. They didn't have GPS in 1967, and that thing seemed to have an inexhaustible power supply.
 

Andrew_ASC

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Then it needs a controls system and algorithms to not shear pins or rods in linkages. It has to know as Mach increases to decrease control input. This would not be a linear system.
 

dr wogz

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You need to find the exact drag coefficient for the exact fin at Mach five. Which is harder than making a rocket go Mach five. Then you compute forces with fluid mechanics. Then this gets into University of Queensland classes on hypersonic flow because you’ve theoretically superpassed my “trivial” mechanical engingeering advanced fluids supersonic flow knowledge. Then you need masters in mechanical or aeronautical engineering to understand CFD. Go find a hypersonic flow expert. I’ve met one Dr. Sreenivas at UTC for computational fluids work he does to Mach 25, he has twenty years experience.

If you are asking these questions you will struggle to hit Mach 5. If just curious. The theory is hard. The practical aspect is even harder. Very few people know hypersonic flow patterns well. I can make a hypersonic airfoil shape. I can’t find a drag coefficient at Mach 5, not smart enough. You start talking of national resources to just wind tunnel something once hypersonic. Private companies have to enter a test matrix with the United States Air Force with a facility like Tullahoma for example which has hypersonic wind tunnels. You’ve exceeded UTSI Mach 4 wind tunnel at this point for real world data.

Forget moveable canards. It’s hard enough with a solid fixed fin. Moving that canard takes a solid background in linkage design. Thermodynamically you’ll want a metal with a higher melt temp than the air temp at Mach 5.
For someone who called up ITAR regs in another post, you seem awfully helpful to a guy who'se made this is their 1st post.. (no one seems to know this guy, nor know where they're from..)
 

Andrew_ASC

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I don’t think it’s a model rocket for it to go Mach 5...I’ll shut up. lol.
 
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lakeroadster

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You know, the pigeon-shaped robot that came out of the back of the Mach 5 when he pushed button G, and could deliver a message back to Pops at home. They didn't have GPS in 1967, and that thing seemed to have an inexhaustible power supply.
You sir are a steely eyed Speed Racer fanatic..
 

markkoelsch

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You know, the pigeon-shaped robot that came out of the back of the Mach 5 when he pushed button G, and could deliver a message back to Pops at home. They didn't have GPS in 1967, and that thing seemed to have an inexhaustible power supply.
Was Pops Racer somehow attached to the forerunner of gps? Affectionately called the pops positioning system one pps.
 

RocketPro

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Assuming that this is a legit question...I’d start with reading the Wikipedia article on the X-15, a hypersonic vehicle. Things that go hypersonic don’t use fins for guidance...
 

Andrew_ASC

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Otherwise he can post his hypersonic guided ICBM in the what did you do rocket wise today thread. I don’t think it’s a legit question anymore.

ICBMs are guided and hypersonic.
 

Iannovation

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For that matter, the canards will only be effective in dense air, I suspect that by the time you hit Mach 5, your project will be in pretty thin air. If you are thinking about a 2 stage rocket, you may want to consider having the canards on the booster or interstage coupler. I suspect that is Jim Jarvis' logic. Check out his thread here.
Thinking 3 stage rocket, still have to get certified for this level, what do you think about clipped delta fins- carbon fiber/ styrene
 

Bat-mite

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Loved Speed Racer as a kid. Went back and watched it about a year ago. Kids could not stand it, and I laughed my butt off.
I'm watching with my kids right now and they love it! We don't let them watch much TV, so they have not been dazzled by modern shows.
 

BDB

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Thinking 3 stage rocket, still have to get certified for this level, what do you think about clipped delta fins- carbon fiber/ styrene
Look for Jim Jarvis’ other thread on here titled “So maybe I’ll try a three stager.” He has been working in this stuff for years. I assume you are at a University, which means you likely have a bigger budget than most of us, but what you are proposing to do has a very steep learning curve.
 

markkoelsch

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Thinking 3 stage rocket, still have to get certified for this level, what do you think about clipped delta fins- carbon fiber/ styrene
At this velocity the heat is a very real issue. I think you are likely looking at metal fins.
 

georgegassaway

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First off..... CANARDS are aerodynamic surfaces up front. Far too many posts here refer to "canards" as a catch-all for aerodynamic control surfaces regardless of where. For example the original Patriot Missile uses tail fin steering, which are NOT canards. The Sidewinder missile has movable nose fins for steering, which ARE canards.

Whichever is used sometimes the whole surface rotates, and sometimes most of the surface is fixed while a small part of the aft end is hinged as with most airplanes (fixed vertical tail plus movable rudder, horizontal stabilizer with movable elevator)

Although I am sure there a few people on this forum that could answer your question, this forum is for upper end hobby participation only, and not guided missle applications..
Onboard guidance that is NOT useable for targeting *IS* allowed for our hobby models (indeed part of the "upper end of the hobby"). Usually used for making models fly vertically or near-vertically.


Assuming that this is a legit question...I’d start with reading the Wikipedia article on the X-15, a hypersonic vehicle. Things that go hypersonic don’t use fins for guidance...
Nope, LOTS of hypersonic vehicles use aerodynamic control surfaces for guidance. INCLUDING the X-15, which had no vectored thrust and whose RCS thrusters were useless in the atmosphere. The X-15 used elevators for pitch (which also rotated differentially for roll control), and the top half of the upper vertical tail moved for rudder control. The Sprint ABM flew over Mach-10, and used small aerodynamic control fins.


Back in the 60's, when D12's ruled, the same could have been said about a Mach 1 model rocket.
D12 did not exist until 1971. Replacing the Cato-prone D13 that came out in 1970. ENERJET composite engines (sold by Centuri) came out about 1971 and were capable of making a model rocket fly Mach-1 if designed/built properly (claiming it and proving it were totally different things).
 
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Andrew_ASC

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40A2C7F5-F1A4-4950-8B7C-B9E20B6F3DCC.jpeg
I got bored about how hot something at Mach 5 gets. So if we assume calorically perfect conditions starting from room temp from advanced fluid mechanics compressible gas flow, I churned out 1788 Kelvins at Mach 5. Or about 2,758.73 Fahrenheit.

This calculation does not include oblique shock behavior since nosecone angle is unknown. The oblique shock would lower this prediction slightly. Back of the envelope student is bored math stuff.
 

Andrew_ASC

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At this velocity the heat is a very real issue. I think you are likely looking at metal fins.
That’s why I solved it with math in a theory. It’s a very rough theory. The NASA method is slightly more accurate but a pain in the arse. They would have compressible gas dynamics textbook spacecraft capsule problems heating up at Mach 23 on re-enter phase. Without knowing OP’s fin or nosecone angles is impossible to include oblique shock effects.

His styrene material selection is poor for a 2,758.73 degree Fahrenheit environment as it boils at 293 degrees Fahrenheit.
 
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markkoelsch

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That’s why I solved it with math in a theory. It’s a very rough theory. The NASA method is slightly more accurate but a pain in the arse. They would have compressible gas dynamics textbook spacecraft capsule problems heating up at Mach 23 on re-enter phase. Without knowing OP’s fin or nosecone angles is impossible to include oblique shock effects.

His styrene material selection is poor for a 2,758.73 degree Fahrenheit environment as it boils at 293 degrees Fahrenheit.
Carbon carbon. Some really advanced alloy maybe. Do they make ceramics that are strong enough to take the forces involved?
 
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