How fast can it go before car breaks up?

Discussion in 'Physics & Math' started by tablariddim, Feb 3, 2011.

  1. tablariddim forexU2 Valued Senior Member

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    Imagine there's an ordinary car let's say it's a Porsche Cayenne, and it can fly at supersonic speeds even almost at the speed of light. How fast could it go before it starts to break up?
     
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  3. Rhaedas Valued Senior Member

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    In the atmosphere, less than supersonic, as cars aren't designed to go that fast and resist the vibrations and temperatures produced.

    In space, as fast as you can push it.
     
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  5. cosmictraveler Be kind to yourself always. Valued Senior Member

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    In space, you can do the speed that you can attain but if you hit anything going those speeds, your dead. The car on earth won't handle much over 300 , if that because it isn't designed to go that speed. Just as Rhaedas has stated.
     
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  7. Pinwheel Banned Banned

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    A Robin Reliant falls apart at around 30mph.
     
  8. Pete It's not rocket surgery Registered Senior Member

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    Ordinary, you say? :bugeye:
     
  9. spidergoat pubic diorama Valued Senior Member

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  10. tablariddim forexU2 Valued Senior Member

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    I'm certain that a Cayenne could easily handle 300mph even on the road, I'm just wondering though if it could surpass supersonic speed, flying just a couple of hundred feet above sea level before it starts to break up. I'm thinking of around 10,000mph. I can imagine the bonnet and perhaps the front valance coming off probably followed by the front wings, I'm not sure how the windscreen could handle that speed though assuming nothing hits it.
     
  11. cosmictraveler Be kind to yourself always. Valued Senior Member

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    You asked if it could handle any speed to which I thought that you meant that the car is in its original configuration, not any modifications done to it. To start off with the tires alone won't exceed 200 MPH, even with the z rated ones that come as a additional feature on that car. So when the tires blow out the car can't achieve anywhere near your thinking.
     
  12. Pete It's not rocket surgery Registered Senior Member

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    But this car can fly, cosmic. It's an ordinary flying car.
     
  13. cosmictraveler Be kind to yourself always. Valued Senior Member

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    But flight can happen at 60 MPH if everything is there to help it fly, like wings, tail etc.
     
  14. billvon Valued Senior Member

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    Well, I would think that the addition of things like wings, tail, engines etc would significantly affect the aerodynamics of the car.

    It would undergo "rapid disassembly" before it melted.
     
  15. tablariddim forexU2 Valued Senior Member

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    Ok the tyres probably couldn't handle it on the road, I was thinking more of the chassis.

    The car flies because there's a super being sitting in it that can fly at light speed. There are no wings or anything else just a bog standard Cayenne.

    Would it melt at 10,000mph;what's the science behind that? I know it's friction but exactly at what speed would metal get too hot to be comfortable?
     
  16. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    I would imagine the fasteners that hold the body panels on would fail before anything else....Long before heat would be a factor. As soon as one fastener fails, wind would get under it, and tear off rest. At 300 mph, it would put 404 pound per square foot on the body. I doubt many panels could hold up to that.
     
  17. Pete It's not rocket surgery Registered Senior Member

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    Perhaps a wind tunnel would be more practical?

    It's the compression of the air rather than friction. When you compress air, it gets hot. How much it gets compressed in front of the car depends a lot on the car's aerodynamics.
    See http://en.wikipedia.org/wiki/Aerodynamic_heating
    Also check out http://en.wikipedia.org/wiki/Atmospheric_entry

    If my Google-fu is on the money, when the Space Shuttle leaves orbit it ploughs through the atmosphere at maybe 18,000mph at its fastest at around 250,000 feet, and heats up to around 1500°C (steel melts around here) as it slows to around 6000mph over a 10 minute descent to 130,000 ft. (mainly from http://www.bbc.co.uk/h2g2/approved_entry/A6381038)

    I don't know how the Shuttle's aerodynamics compare to a cars. I imagine it's deliberately bad during reentry, because they're using the air as brakes - ie they want to shed energy to the atmosphere. But, it's also carefully designed to keep the hottest air away from the surface, behind a cushion of cooler air. And this is at a very high altitude. And small flaws in the aerodynamics (a tiny gap between panels, a loose fastener like MacGyver said) lead to desctructive failure, as tragically demonstrated by the Columbia:
    http://en.wikipedia.org/wiki/Space_Shuttle_Columbia_disaster#Destruction_during_re-entry


    Anyway, I wouldn't like a car's chances in a 10,000mph wind tunnel.
     
    Last edited: Feb 3, 2011
  18. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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  19. Pete It's not rocket surgery Registered Senior Member

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    I think we should get Mythbusters onto this. They've done a rocket-propelled Chevy... they just need to upscale a bit and stick a Porsche on the end of an Ariane 5 launch vehicle!
     
  20. Dywyddyr Penguinaciously duckalicious. Valued Senior Member

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    More or less already done.
    Top Gear turned a Reliant Robin into a space shuttle.
     
  21. MacGyver1968 Fixin' Shit that Ain't Broke Valued Senior Member

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    I got this data by googling "pressure at 300 mph". Does anyone know the formula that it was derived from?
     
  22. Thoreau Valued Senior Member

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    There are way too many factors to determine this velocity at which the car would begin to fall apart.
     

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