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Flying a Cessna On Other Worlds: xkcd Gets Noticed By a Physics Professor 148

Posted by Soulskill
from the make-sure-your-insurance-is-up-to-date dept.
djl4570 writes "xkcd's 'What If' series consists of humorous takes on highly implausible but oddly interesting hypothetical physics questions, like how to cook a steak with heat from atmospheric re-entry. The most recent entry dealt with flying a Cessna on other planets and moons in the solar system. Mars: 'The tricky thing is that with so little atmosphere, to get any lift, you have to go fast. You need to approach Mach 1 just to get off the ground, and once you get moving, you have so much inertia that it’s hard to change course—if you turn, your plane rotates, but keeps moving in the original direction.' Venus: 'Unfortunately, X-Plane is not capable of simulating the hellish environment near the surface of Venus. But physics calculations give us an idea of what flight there would be like. The upshot is: Your plane would fly pretty well, except it would be on fire the whole time, and then it would stop flying, and then stop being a plane.' There are also a bunch of illustrations for flightpaths on various moons (crashpaths might be more apt), which drew the attention of physics professor Rhett Allain, who explained the math in further detail and provided more accurate paths."
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Flying a Cessna On Other Worlds: xkcd Gets Noticed By a Physics Professor

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  • by Gordonjcp (186804) on Saturday February 02, 2013 @05:04PM (#42773669) Homepage

    ... but I think it went over his head.

  • by Anonymous Coward on Saturday February 02, 2013 @05:11PM (#42773703)

    In the What-if it's explicitly stated that the gas tanks have been replaced with batteries and had an electric engine installed.

  • by KeensMustard (655606) on Saturday February 02, 2013 @05:19PM (#42773729)
    This is covered in the simulations as well. Is there something in particular preventing you from reading it?
  • by alphatel (1450715) * on Saturday February 02, 2013 @05:24PM (#42773769)

    This is covered in the simulations as well. Is there something in particular preventing you from reading it?

    Although I am not the poster you asked this question of, I have to admit not ever reading xkcd, having more important things on my Kindle.
    Having left my e-ink display in the car, I read through what-if and if nothing else, the penny exercise had me laughing out loud. Tough to force on a rocket scientist with humor less moist than a block of dry ice, but it happens.
    Thanks to / for not posting a slashvertisement and giving me the giggles.

  • by MichaelSmith (789609) on Saturday February 02, 2013 @05:39PM (#42773843) Homepage Journal

    Load liquid oxygen into the fuel tanks. Methane comes into the engine from the atmosphere. An engine with minor modifications might be made to operate.

  • by kraut (2788) on Saturday February 02, 2013 @05:47PM (#42773895)

    Although I am not the poster you asked this question of, I have to admit not ever reading xkcd, having more important things on my Kindle

    Like slashdot?

  • by Anonymous Coward on Saturday February 02, 2013 @07:20PM (#42774513)
    One of Einstein's what-ifs when something like this. Light moves at the same speed for all observers. So imagine a space ship travelling at near the speed of light relative to Observer A. Observer B is in the space ship and shines a laser straight up and back down off of a mirror. To Observer A the laser appears to move along the top of a triangle as the ship goes by at near light speed. Observer A sees the light travel a greater distance than Observer B. Both observers see light traveling at 299 792 458 m / s. So the only way this can be true is if time is moving slower for Observer B than A.

    Feel free however to point that we don't know how to make a space ship go that fast. Point out the difficulty in actually observing such an event. Deride imagination.
  • by Runaway1956 (1322357) on Saturday February 02, 2013 @08:33PM (#42774849) Homepage Journal

    It is explained that on one world, you burn then crash - as opposed to crash and burn - and why it would happen in that order. And, on another world, you would crash, but not burn, and why.

    This little "what if" is a reasonable explanation of conditions on other worlds, as we understand them, and how they would affect flight in a particular type and model of aircraft.

    If the story teller were addressing an international physics conference, he might sound a bit stupid with this presentation. As he is addressing an audience of nerds, with the intent of amusing and possibly educating them - he's done an excellent job.

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