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Why getting BACK from space is harder than getting there
Why getting BACK from space is harder than getting there
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When a spaceship or meteor enters our
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atmosphere, it becomes a fireball. But
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that heat doesn't come from friction
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with the atmosphere like most people
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think. There's actually something way
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more interesting going on. It takes so
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much kinetic energy to get a spacecraft
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to the moon. I mean, that's why the
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rockets are so huge. But when you slow
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down, all of that kinetic energy has to
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go away somewhere, right? Well, you
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could fire giant rockets to slow you
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down and shave off some kinetic energy,
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but you'd also have to carry all that
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fuel up with you, too. That's why
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spacecraft use the atmosphere as a break
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instead. It's a genius way to take all
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that kinetic energy and just convert it
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to heat. Here's why friction isn't
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what's happening. A spacecraft like
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Orion slams into the atmosphere at
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25,000 mph. That's something like 40
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times faster than a passenger jet. At
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that velocity, the air in front of the
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spacecraft can't get out of the way. So,
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it just gets squeezed and compressed
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really violently. That heat is not from
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air molecules rubbing against each
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other. It's because the spacecraft acts
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like a giant piston, compressing the air
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into this impossibly thin layer. And
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when you compress a gas, it heats up.
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The air gets so hot as it gets squeezed,
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it stops being air and becomes a
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superheated plasma. It's a whole other
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state of matter. That plasma can reach
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10,000°,
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hotter than the surface of the sun. And
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it works really well. squishing the
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atmosphere into a hot plasma removes
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more than 99.9%
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of Orion's kinetic energy before it
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deploys those parachutes. And this is
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why it's so important that space
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capsules are the opposite of pointy
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because that blunt shape creates a shock
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wave that's pushed out away from the
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surface. So almost all of that heat
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stays out in front of the heat shield
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and not touching the ship and the inside
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of the spacecraft stays a comfortable
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room temperature. Sharp, streamlined
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shapes, which works basically everywhere
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else in aerodynamics, actually makes
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re-entry worse. And that's why every
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crude capsule ever built is shaped like
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a pudgy little cone. Follow me for more
2:01
cool science videos.
