Buoyancy is an easier equation to solve than lift.

EdNutting 15 hours ago | parent | next [-]

So why do they need to use helicopters and a risky airlift to return the astronauts to the main vessel? Why not just use the speedboats to take them back? Seems really odd and I can’t find any reasonable explanation.

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_moof 15 hours ago | parent | next [-]

Helicopter -> large boat is much easier, and much faster, than small boat -> large boat. And it's not riskier. I know the inherent risk in flight is greater, but it's also much more managed, so the actual risk is less.

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stackghost 15 hours ago | parent | prev [-]

>Why not just use the speedboats to take them back?

They actually covered this in the broadcast: Helicopters are faster to get the astronauts to medical, smoother in rough seas, and there's less risk of being swamped by a rogue wave. Plus, since the astronauts might have fatigue/muscle atrophy/whatever, it complicates potential boat transfers.

	▲	Brybry 14 hours ago \| parent [-]
		The public information sheet implies that in poor weather/rough seas they would do crew recovery in the well deck, sort of like how Dragon works. [1] From the broadcast, they made it sound like a big factor is the 2 hour program requirement to get the crew out of the capsule. Maybe they can't reliably hit that mark with a well deck recovery? [1] https://www3.nasa.gov/sites/default/files/files/orion-recove...

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stackghost 15 hours ago | parent | prev [-]

>Buoyancy is an easier equation to solve than lift.

That's a snappy one-liner but it doesn't address the real concerns.

First of all, subsonic lift is well understood and has been for decades. The answer is much more mundane: The Artemis mission profile does not require payload doors that open, no Canadarm, no requirement to service, launch, and/or capture satellites in orbit, and so like good engineers they designed the minimum vehicle that satisfies the requirements.

Also, the Shuttle was actually much more expensive to reuse than originally predicted.

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JumpCrisscross 15 hours ago | parent [-]

> subsonic lift is well understood and has been for decades

I said easy. Not well understood. I can fly planes. It’s hard, and has limited room for fucking up. (It’s also hyperbole to suggest we understand lift. We don’t.)

Piloting a boat is easier and more forgiving. Hence, splashdown. You don’t need direction. You don’t need lift. Parachute physics is a backbreaker, but it’s symmetrical. Same for splash.

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_moof 13 hours ago | parent | next [-]

You're a VC arguing with an aerospace engineer about aerospace engineering.

I'm also a pilot (CFI). My day job is space operations. And I can tell you've had too many hangar arguments about how wings work.

Pilots don't understand lift. Aero engineers understand it just fine.

	▲	JumpCrisscross 5 hours ago \| parent [-]
		I love this comment. Thank you. For what it’s worth, I’m not a CFI but I did study actual astronautical engineering. Not much good once we’re in an atmosphere, which, granted, is where the boats and planes go. But I’ll stand by my statement that nobody—apart from interplanetary reëntry and drone teams—fundamentally understands lift. (I certainly didn’t when I was solving analytic solutions by hand.)

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stackghost 14 hours ago | parent | prev [-]

>Piloting a boat is easier and more forgiving. Hence, splashdown.

At no point were the astronauts piloting a boat. The reasons they splash down into the ocean has nothing to do with buoyancy being easier to solve, and even less to do with the ease of piloting a boat.

>It’s also hyperbole to suggest we understand lift. We don’t.

Maybe you personally do not understand lift, but "we" do in fact understand it. Please educate yourself before continuing this discussion any further.

	▲	WalterBright 12 hours ago \| parent [-]
		There are multiple mathematical and physical approaches to understand lift, but they have the same results and are correct.