Comment by Ifkaluva
13 hours ago
Can somebody help me understand why this does a water landing, like the old Apollo missions, instead of like the space shuttle that lands like a plane?
13 hours ago
Can somebody help me understand why this does a water landing, like the old Apollo missions, instead of like the space shuttle that lands like a plane?
A big part of the reason is that Orion (and Apollo) reentry speeds are way higher due to the orbital mechanics involved in going to the moon and back. Today's was actually the fastest manned reentry ever attempted.
For reference the shuttle generally reentered at ~17.5K mph, and today's was 24K-25K mph.
It's not clear that we could build a craft with wings that could survive that. So then you're looking at adding fuel just to slow down, plus fuel for the weight of the wings themselves, plus fuel to carry all this extra fuel to the right place, etc.
The space shuttle landed like something resembling a plane, but it is more accurate to say it landed like a concrete brick traveling faster than the speed of sound.
Splashdown-style landings are the simplest and safest, parachutes are always good but adding water makes for another layer of safety (and of risk, to be fair, it could sink).
Wings and rudders and landing gear are very heavy. Then there's the flight control system in all its complexity, along with redundant hydraulic systems and so on.
Lot of the world is ocean & they basically decided the landing point the moment they entered the free return trajectory, 9 days prior - easier to shift the landing point a little to a different place in the ocean place with better weather tha. to switch to a backup airport.
With lunar landing flights they would still have to choose 4 days before, as long as they do direct return.
Eventually you want to break to Earth orbit (propulsively or aerodynamically) and board a dedidacted craft for landing. But till then water landing capsules work.
A Space Planes is needed to land at a runway like a plane.
Space Planes are not only much more dangerous, but are not ideal for this type of mission. They carry a lot of extra weight (wings) that would affect how much fuel is needed to launch them to the Moon.
Capsules are safer and more lean in terms of weight.
The Shuttle was not ideal in many ways. It was used so long not because it was the best option, but because Congress wanted it to keep it going for jobs.
Buoyancy is an easier equation to solve than lift.
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.
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.
>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.
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>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.
> 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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Aerospace engineer here: The simple answer is that the Shuttle form factor is unnecessarily complex for this mission.
A small Apollo-style capsule that parachutes into the ocean has a simpler mission profile, which allows for simpler technical and operational requirements, which in turn reduces program cost.
Too fast. The space shuttle used to reenter sometimes over us in California. I remember in elementary school the entire building shook, and that was just one building! The amount of energy being dissipated is literally astronomical! If you've never experienced the sonic boom of reentry it is something to marvel at. It literally feels like an earthquake!