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NASA Space Hardware

Will The Next Generation of Spacecraft Land In the Water? 318

Posted by Zonk
from the splashdown-for-the-future dept.
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."
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Will The Next Generation of Spacecraft Land In the Water?

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  • by gentimjs (930934) on Friday December 14, 2007 @02:07PM (#21699800) Journal
    You'd spend more energy getting the buoyant "rocket" down deep underwater and keeping it there, and then it probably wouldnt 'bound' more then a few feet out of the water. Check out a video of a submarine doing an "emergency surface" then consider if it would help get the submarine into space. Interesting idea, but No-go.
  • Water or land? (Score:5, Informative)

    by GenKreton (884088) on Friday December 14, 2007 @02:08PM (#21699804) Journal
    As someone who worked partially on the CEV, it has been decided. it is in the requirements that Lockheed Martin furnish a vehicle that is capable of both. One of the design limitations now is that it must actually be stable in swells of up to 14 feet, which are not uncommon in the cold North Atlantic - emergency abort scenarios land all launches there during early lift-off stages. There are huge problems with ill-effects of ocean landings for crews and they really are looking to avoid it, but even with parachute and pillow systems, they are looking at potential damage,
  • by GenKreton (884088) on Friday December 14, 2007 @02:18PM (#21699968) Journal
    They want to land on land for recovery reasons and to save the crew the effects of being stuck out in the ocean in a waving buoy. With that said, you hit the nail on the head, finding land and aiming at it is significantly harder. That's why both systems are in the engineering specifications NASA gave us, and will be built into the final design, tentatively. The system for placing the capsule at a good location is not one of the design challenges facing Lockheed Martin's contract.
  • Re:Water or land? (Score:1, Informative)

    by Anonymous Coward on Friday December 14, 2007 @02:24PM (#21700040)
    You can lead into a water landing by piercing the surface before the bulk of the craft impacts, breaking surface tension and considerable pillowing the landing.
  • by LWATCDR (28044) on Friday December 14, 2007 @02:26PM (#21700062) Homepage Journal
    "eliminating the 1500 lb airbags for landing has its appeal"

    "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)

    by ianare (1132971) on Friday December 14, 2007 @02:32PM (#21700152)
    The planned Ares V has a mass to LEO [wikipedia.org] of 130,000 kg, the energia has 'only' 88,000 kg, so the solution isn't that simple. Besides, any weight savings on any system is obviously an advantage when the cost per kg is so high.
  • by CompMD (522020) on Friday December 14, 2007 @02:40PM (#21700272)
    Its not the water that is a problem, its the salt in that water. You run into accelerated corrosion problems with exposure to ocean water.
  • by Chairboy (88841) on Friday December 14, 2007 @02:40PM (#21700274) Homepage
    For the folks saying "use the ISS!': Won't work. When coming back from the moon, the approach speed is far too high to enter the orbit that the ISS or any other reasonable future space station is in. The braking is done through friction as the spacecraft enters the earth's atmosphere, and provides MUCH more delta-v than would be feasible by using rockets.

    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.
  • by 2short (466733) on Friday December 14, 2007 @02:44PM (#21700328)
    Yes, sending it "randomly flying" is exactly what I proposed.

    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.
  • by delta407 (518868) <slashdotNO@SPAMlerfjhax.com> on Friday December 14, 2007 @02:46PM (#21700372) Homepage
    Why not pick up the landing gear on the way back? Let's investigate.

    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)

    by Harmonious Botch (921977) * on Friday December 14, 2007 @02:48PM (#21700398) Homepage Journal
    Spaceship one was good for getting to the 'edge of space' and back. Being in orbit is a different thing. As a general rule, it takes 30 times as much energy to get into orbit as it does to just get up there. ( the number varies with altitude, of course, but 30 is a good back-of-the-envelope approximation ). The energy that has to be bled off when coming down is roughly 30-fold. So spaceshipOne is not even close to being able to do it. It requires new materials and/or a new design. Or stick with the high maintainence and unpleasant failure rate of the shuttle.

    Or you can stick to the simple way of doing it with rockets and parachutes.
  • by Robonaut (1134343) on Friday December 14, 2007 @02:51PM (#21700418)
    When returning from the moon, a spacecraft has significant excess velocity. Entering back into an Earth orbit (like rendezvousing with the ISS) means that the CEV would need to make a burn to slow down. This would consume a significant amount of fuel (that very well could weigh as much or more than the airbags). Instead, the Apollo CM and the CEV are designed to plunge directly into the Earth's upper atmosphere, literally burning off the excess velocity through atmospheric drag. This requires a larger heat shield, but lowers the mission complexity and fuel the spacecraft needs to carry.
  • by Anonymous Coward on Friday December 14, 2007 @03:18PM (#21700788)
    There have been serious studies into this idea for decades, generally involving a giant "gun barrel" submerged in water. Pump the water out, put the rocket in, let water in from the bottom to push the rocket out. Unfortunately, the NASA site with all the cool and futuristic science has been taken down (no doubt because Al Quaeoeida could build their own terrorist space elevator if they read about it on the web).

    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)

    by vought (160908) on Friday December 14, 2007 @03:40PM (#21701098)

    The Apollo program that sent men to the moon had a much better safety record than the Shuttle, which lost two crews, one on takeoff and another on re-entry.
    It also had a much smaller crew module and in part, was built to scare the crap out of the Soviets.

    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.
  • by Mercano (826132) <mercano@g[ ]l.com ['mai' in gap]> on Friday December 14, 2007 @03:55PM (#21701340)

    Based on my understanding, you're going to "break into earth orbit" upon return anyway; it's a matter of whether you keep breaking and re-enter, or orbit a bit first..

    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)

    by p3d0 (42270) on Friday December 14, 2007 @03:56PM (#21701356)
    Having taken the time to write all that, I'm not sure it's true now. I think it takes about the same fuel to get from the Moon to pretty much any low Earth orbit you want, including the one with the ISS in it.

    Too bad. I thought that was a pretty good explanation, except that it's wrong. :-)
  • Re:Simple Answer (Score:3, Informative)

    by timster (32400) on Friday December 14, 2007 @04:09PM (#21701502)
    Obsolete means it's just not a very good rocket compared to what can be built today. As for the parts, sure there are custom parts, but there are plenty of off-the-shelf parts also, and even the existing plans for manufacturing the custom parts call for the use of off-the-shelf parts or equipment to build.

    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!"
  • by geekoid (135745) <dadinportland&yahoo,com> on Friday December 14, 2007 @04:55PM (#21702186) Homepage Journal
    Anywhere, if you hit it hard enough.
  • by iamlucky13 (795185) on Friday December 14, 2007 @05:14PM (#21702400)
    Can't we simply vote for it to land on Cowboy Neal?

    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.
  • by IdeaMan (216340) on Friday December 14, 2007 @05:25PM (#21702554) Homepage Journal
    You are absolutely right.
    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.
  • by TempeNerd (410268) on Friday December 14, 2007 @05:57PM (#21702958)
    This group is trying the next step from that - they want to use a balloon to rapidly accelerate to the edge of the atmosphere and passing beyond (like a whale jumping from sea).

    http://www.jpaerospace.com/ascender175.html/ [jpaerospace.com]
  • Re:Actually... (Score:3, Informative)

    by AJWM (19027) on Friday December 14, 2007 @06:29PM (#21703342) Homepage
    Actually your explanation is mostly right -- you just omitted the fact that the gravitational force of a large body (the Earth, Moon, or Jupiter for outer solar system missions) can be used to change velocity (either direction or speed) too, as can aerobraking.

    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.

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