Will The Next Generation of Spacecraft Land In the Water? 318
Reservoir Hill writes "Work is progressing on the design of the new Orion Crew Exploration Vehicle (CEV), the next generation of NASA spacecraft that will take humans to the International Space Station, back to the Moon, and hopefully on to Mars. One major question about the spacecraft has yet to be answered. On returning to Earth, should the CEV land in water or on terra firma? After initial studies, the first assessment by NASA and the contractor for the CEV, Lockheed Martin, was that landing on land was preferred in terms of total life cycle costs for the vehicles. Getting the CEV light enough for the Ares rockets to be able to launch it, and therefore eliminating the 1500 lb airbags for landing has its appeal. A splashdown in water seems to be favored."
Re:Thought about something like this (Score:2, Informative)
Water or land? (Score:5, Informative)
Re:surface of earth is mostly water (Score:3, Informative)
Re:Water or land? (Score:1, Informative)
Lack of understanding. (Score:3, Informative)
"Landing on land lets it be lighter, check."
The airbags are used for landing on LAND.
They are not flotation devices. Any thing that can fly is going to light enough float on water if it doesn't leak.
The airbags are to reduce the impact.
Re:Simple Answer (Score:5, Informative)
Re:What is the downside? (Score:3, Informative)
Skip water recovery weight (Score:5, Informative)
To use the ISS, the spacecraft would need to perform a complex aerobraking maneuver (basically, a partial re-entry), then have the fuel needed to circularize its new orbit so that it can rendesvous with the ISS. By the time this is done, the design for the capsule is far heavier than the 1,500lb penalty that airbags impose.
My idea, make the water landing a known 'capsule loss' scenario, the same way it is with the Shuttle. If things go _so wrong_ that a water landing is unavoidable (say, launch failure) then design the capsule for quick-egress after a water landing. Airplanes ditch in water and people have time to get out before they sink. My Piper Cherokee will float long enough for me to climb out onto the wing, and for a real shock look at the survival training that helicopter passengers go through in the military, that's some pretty intense worst case scenario stuff.
With Rogallo steerable parachutes, landfall should be available at all times except the first few minutes of launch. Skip the airbags, make the capsule so it stays afloat just long enough for egress, and train the astronauts on how to get out fast.
Re:Theyy could always ask Paul Revere ... (Score:5, Informative)
You put the package in whatever orbit is convenient (as opposed to the ISS, which isn't convenient), and you know its position as surely as you know that of the ISS, or any other sattelite. Space navigation doesn't involve any "finding", ever.
Re:Theyy could always ask Paul Revere ... (Score:5, Informative)
Recall: Apollo's flight plan was an initial burn to get into earth orbit, another burn to leave orbit on course for the moon (trans-lunar injection), another burn to get in orbit of the moon, and another burn to leave orbit on course for earth (trans-earth injection). That's it. They didn't return to orbit after leaving the moon. They left the moon, coasted for a couple days, hit their entry interface, then hit the Pacific.
Why? Going back into orbit requires adding two more burns: one to enter Earth orbit, and another to leave it. Adding a rendezvous with the ISS (or any other floating payload) means an additional 1-2 burns to match the orbital planes, an additional burn to raise or lower your orbit, and God knows how long until the orbits of the two vehicles sync. Look at the space shuttle: even with matching the orbital planes and scheduling launch for an ideal rendezvous profile, it takes them 36-48 hours to catch up with the space station.
Trans-earth injection is complicated enough without adding all that. Extra burns means extra propellant, which means extra weight, which is exactly what you're trying to avoid. Not to mention, each of those steps is another opportunity for failure, and how do you abort if you don't have landing gear?
This is why they are Rocket Scientists(TM).
SpaceshipOne * 30 (Score:5, Informative)
Or you can stick to the simple way of doing it with rockets and parachutes.
Re:Theyy could always ask Paul Revere ... (Score:2, Informative)
Re:Thought about something like this (Score:1, Informative)
Here's a link to a really old (1963) article on a variant of the concept: http://www.time.com/time/magazine/article/0,9171,829711,00.html [time.com]
Re:Simple Answer (Score:3, Informative)
Part of the goal with Ares is to use what worked from the man-rated Shuttle program (inexpensive and expendable main tank, reusable, recoverable SRBs) and what worked from Apollo (updated and enlarged crew module) with refinements that mean the vehicle will be flexible and have room for growth. Saturn V was a nice rocket, but didn't meet these goals. You have to build a whole new one every time.
Re:Theyy could always ask Paul Revere ... (Score:4, Informative)
No, not really. The Apollos didn't preform any breaking maneuvers on the way back to Earth, they just hit the atmosphere at full speed and scrubbed off their speed there. If you enter shallow enough, you can burn off more speed in the upper atmosphere before you start getting into the thicker air, and a sufficiently durable heat shield turned out to be lighter then the fuel that would have been required to slow the ship down. In fact, even orbiting spacecraft generally burn as little fuel as possible to get themselves just bellow orbital velocity and then do the rest as atmospheric breaking.
Actually... (Score:3, Informative)
Too bad. I thought that was a pretty good explanation, except that it's wrong.
Re:Simple Answer (Score:3, Informative)
Here's a quote from http://www.space.com/news/spacehistory/saturn_five_000313.html [space.com]:
"There is no point in even contemplating trying to rebuild the Saturn 5. Having a complete set of Saturn 5 blueprints would do us no good whatsoever. True, we would still be able to bend the big pieces of metal fairly easily. But they are not the problem.
"The real problem is the hundreds of thousands of other parts, some as apparently insignificant as a bolt or a washer, that are simply not manufactured any more. Everything would have to be redone. So a simple rebuild would be impossible. The only real answer would be to start from scratch and build anew using modern parts and processes. Yet another immense challenge!"
Re:Goes without saying (Score:3, Informative)
Missing Option: Cowboy Neal (Score:3, Informative)
Sorry, had to get that in there. I couldn't help but feel the summary was asking us for our uninformed opinion.
It sounds to me like you're talking about the requirement that has been with the system from the beginning that it be able to ditch in the ocean, regardless of the nominal landing profile. What NASA is trying to decide now is if it should normally land in the ocean and face the added recovery hassle and risk, or on land and need to accomodate the added 1500 pounds of weight plus more complexity (it will either have to discard the heat shield in flight, which may be a falling debris hazard, or have dropout panels for the airbags to deploy through). Water landing is a requirement. Dry landing is an option.
Until just recently, NASA and Lockheed had moved ahead with plans for touchdown on land. However, there's been a lot of discussion over the past two years about the need to keep the weight down. They already reduced the diameter of the capsule by half a meter to keep the capsule within the weight budget. I think also the service module is above its original weight targets, and either the SRB or the second stage performance is below its original goal.
In the discussion section of the article, someone suggested doing an air capture, much like how the Air Force used to retrieve film capsules from the Corona spy satellites by snagging their parachutes and realing them in. However, I don't think he realized that those capsules weighed a few dozen pounds, while Orion will weigh around 8.5 tonnes. NASA also planned to do mid-air capture of the Genesis capsule, which was carrying solar wind particles. Unfortunately, the parachute failed to deploy and it dug a crater in New Mexico.
For comparison, Soyuz lands on dry land in Kazakhstan. Instead of airbags, it has a set of small retrorockets on the bottom that fire just before touchdown to slow from the 24 ft/s rate of the parachute to just 5 ft/s (5.5 km/hr). I'm not sure how they deal with fire through or around the heat shield.
Re:Thought about something like this (Score:2, Informative)
Instead of using water as the propellant directly, have the water press against a piston that compresses hot hydrogen.
The seal issues have been addressed for the HARP gun:
http://www.dunnspace.com/harp.htm [dunnspace.com]
http://www.astronautix.com/lvs/sharp.htm [astronautix.com]
http://www.astronautix.com/lvfam/gunnched.htm [astronautix.com]
http://en.wikipedia.org/wiki/Light_Gas_Gun [wikipedia.org]
I don't know if heat buildup is more of an issue with a longer, lower G force tube.
Re:Thought about something like this (Score:2, Informative)
http://www.jpaerospace.com/ascender175.html/ [jpaerospace.com]
Re:Actually... (Score:3, Informative)
Approaching the Earth from the Moon at a slight angle, ie aiming toward one pole or another rather than the equator, lets you use Earth's gravity to help change the orbital plane. You still need to shed a lot of velocity to establish Earth orbit, but can use some of that to change the orbital plane.
Going the other way (ISS to Moon) you have the opposite problem, you have to add energy to change the orbit and add more to extend that orbit to the Moon, and that all requires fuel. So ISS may be okay for returns (except that it's easier to just do a direct entry anyway) but is in wrong orbit for departure.