NASA Orion Splashdown Safety Tests Completed 49
DevotedSkeptic sends this news from NASA:
"The 18,000-pound test article that mimics the size and weight of NASA's Orion spacecraft crew module recently completed a final series of water impact tests in the Hydro Impact Basin at the agency's Langley Research Center in Hampton, Va. The campaign of swing and vertical drops simulated various water landing scenarios to account for different velocities, parachute deployments, entry angles, wave heights and wind conditions the spacecraft may encounter when landing in the Pacific Ocean. The next round of water impact testing is scheduled to begin in late 2013 using a full-sized model that was built to validate the flight vehicle's production processes and tools."
Why water? (Score:4, Informative)
Why is it that USA space tech prefers water splashdowns instead of dry land like the Russians and Chinese?
"Softer landings" doesn't quite cut it as a reason, for at the speed of the impact, water is just as hard as terra firma. Then there's the risk of crew drowning and/or craft loss thru sinking. That doesn't occur in dry land.
Re:Why water? (Score:5, Informative)
Re:Why water? (Score:5, Informative)
Why is it that USA space tech prefers water splashdowns instead of dry land like the Russians and Chinese?
"Softer landings" doesn't quite cut it as a reason, for at the speed of the impact, water is just as hard as terra firma. Then there's the risk of crew drowning and/or craft loss thru sinking. That doesn't occur in dry land.
Because landing in water means you can get away with a higher landing speed without putting too many Gs on the astronauts - ref the Wikipedia article on splashdown [wikipedia.org]. The Russians (né Soviet) capsules lands on land because the Russians have so much open space available, but that means they have to carry either a larger parachute and/or one or more braking rockets to lower the impact speed to something tolerable. AFAIK the first Russian capsules that the cosmonauts rode all the way down - the jury-rigged Vostok they called Voskhod - carried their braking rockets attached to it's parachute lines...
A capsule landing on land also needs to be sturdier to take the increased shock loads, both from the impact and from the application of the braking rockets. This means you either needs a bigger rocket to get it up there, or less internal space for the astronauts / cosmonauts to move about in. A landing on land may not sink, but it does run the risk of taking a roll once it's down - ref Soyuz 18a [wikipedia.org].
Another reason given for the American preference for landing in water compared to the Russian preference for landing on land is the location of the launch sites. An American early abort will dump the capsule in the Atlantic ocean, whereas a Russian early abort will see the capsule come down on the steppe. That said, the current Russian capsules are rated for landing in water, just in cause - refer to Soyus 23 [wikipedia.org] landing on a frozen lake and punching through the ice.
The Chinese seems to favour a land landing as well, which makes sense considering their landmass, lack of a large blue water fleet and the simple fact that their Shenzhou spacecraft seems to be based on / borrows heavily from the Russian Soyuz capsule.
In short; landing on water lets you get away with a lighter spacecraft, and does away with the need for a very large parachute and/or braking rockets. This means you can get away with a smaller rocket, or carry more supplies for a given size rocket.
Re:Because gee, why not? (Score:5, Informative)
The Apollo Command Module was not "uncontrolled" on reentry. Its center of gravity was intentionally offset from the spacecraft's centerline. This gave it a semi-gliding (admittedly steep but not non-existent) capability. Thus they could control the direction of the reentry aerodynamically by using thrusters to rotate the spacecraft and so control the direction of "glide". There was a lot more capability to that Apollo-Saturn stack than is visible or well known!
Re:Why water? (Score:4, Informative)
IAAFRS. It's cheaper, safer, and fails more elegantly (more likely to give you a recoverable crew module that can be analyzed). Korolev might have preferred wet landings but the USSR's leadership did not trust the US Navy.
Nope, the capsules land very slowly, on the end of parachutes after significant braking.
Early Soviet designs eject the pilot & flight recorder on a sled which then parachutes down. The actual capsule pancakes at fairly high speed and is completely destroyed, unlike water-landed capsules.
Those are very real risks, but keep in mind that the capsule is a viable space environment, so pretty similar to a submarine.