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How do spacecraft slow down?

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NASA

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Well, there are primarily two methods of thought\h
for how spacecraft slow down

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and you really have\hto ask yourself, "Are we landing in an area that\hhas an atmosphere?"

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If not, you definitely want to\hgo with retropropulsion, where you use retro\hthrusters pointed down at the surface of the\h\h

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planet to slow yourself down as you're coming in.\h
If you do have an atmosphere, that makes it a lot\heasier,\h

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as the atmosphere acts as kind of a giant\h
break as you slow down. So you have your missions\h\h

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like Apollo that used retropropulsion when we\h
went to the Moon. When you're able to use the\hatmosphere,

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you have your heat shield on the blunt\hend of your spacecraft coming into the atmosphere.

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And then the parachutes will come out and slow you down the rest of the way to provide that safe landing.

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Here at NASA, we're constantly developing\hnew technologies to help with that entry,\hdescent and landing, or EDL.

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Some of the trick in\hentering atmosphere is when you do have it but\hit's really thin.

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One of the technologies NASA\his developing to handle those is called HIAD,

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Hypersonic Inflatable Aerodynamic Decelerator.\h
The HIAD can come as a heat shield much like\h\h

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the blunt body heat shields of those older\hmissions that were made out of ceramics or\hmetals, but were very hard.

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However, HIAD is a flexible\hwoven system that compacts really, really small.\h

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So you're able to actually get a very small heat\h
shield inside your rocket diameter.

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With HIAD,\hwhen the fairing comes off, the heat shield\hcan then inflate and expand to a diameter\hmuch larger than your rocket.

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Therefore you're\hable to bring in a much larger payload than\hyou were before.

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So how do spacecraft slow\hdown?

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We have retropropulsion, you've got your\hrigid aeroshells and parachutes,

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and coming soon,\hwe've got these inflatable heat shields.