4 ms·

Buoyancy is an easier equation to solve than lift.

BitsAndObjects 7mo ago
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.
- stackghost 7mo ago
  >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 7mo ago
    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-recovery.pdf https://www3.nasa.gov/sites/default/files/files/orion-recove...
    - tedd4u 7mo ago
      The other reason is that the capsule can splashdown far away from the ship. In this case it was close (3km or so). It can possibly fall much farther away. In which case boats would be much slower. Add in the possibility of rough seas & bad weather the helos make sense. And just to keep things simple I think they just use them no matter what. Prevent errors. Also gives a chance to rehearse and debug the full recovery process in case it’s actually really needed the next time.
- _moof 7mo ago
  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.
stackghost 7mo ago
>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.
- JumpCrisscross 7mo ago
  > 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.
  - stackghost 7mo ago
    >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 7mo ago
      There are multiple mathematical and physical approaches to understand lift, but they have the same results and are correct.
  - _moof 7mo ago
    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.

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.

stackghost 7mo ago
>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 7mo ago
  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-recovery.pdf https://www3.nasa.gov/sites/default/files/files/orion-recove...
  - tedd4u 7mo ago
    The other reason is that the capsule can splashdown far away from the ship. In this case it was close (3km or so). It can possibly fall much farther away. In which case boats would be much slower. Add in the possibility of rough seas & bad weather the helos make sense. And just to keep things simple I think they just use them no matter what. Prevent errors. Also gives a chance to rehearse and debug the full recovery process in case it’s actually really needed the next time.
_moof 7mo ago
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.

stackghost 7mo ago

>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.

JumpCrisscross 7mo ago
> 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.
- stackghost 7mo ago
  >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 7mo ago
    There are multiple mathematical and physical approaches to understand lift, but they have the same results and are correct.
- _moof 7mo ago
  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.