Posted on 03/25/2011 12:01:39 PM PDT by LibWhacker
Spaceships powered primarily by water could open up the solar system to exploration, making flights to Mars and other far-flung locales far cheaper, a recent study has found.
A journey to Mars and back in a water-fueled vehicle could cost as little as one space shuttle launch costs today, researchers said. And the idea is to keep these "space coaches" in orbit between trips, so their relative value would grow over time, as the vehicles reduce the need for expensive one-off missions that launch from Earth.
The water-powered space coach is just a concept at the moment, but it could become a reality soon enough, researchers said. [Video: Space Engines: The New Generation]
"It's really a systems integration challenge," said study lead author Brian McConnell, a software engineer and technology entrepreneur. "The fundamental technology is already there."
Space coach: The basics
The space coach concept vehicle is water-driven and water-centric, starting with its solar-powered electrothermal engines. These engines would super-heat water, and the resulting steam would then be vented out of a nozzle, producing the necessary amount of thrust.
Electrothermal engines are very efficient, and they're well-suited for sustained, low-thrust travel, researchers said. This mode of propulsion would do the lion's share of the work, pushing the space coach from Earth orbit to Mars.
Smaller chemical rockets could be called into service from time to time when a rapid change in velocity is needed, McConnell said.
The space coach's living quarters would be composed of a series of interconnected habitat modules. These would be expandable and made of fabric, researchers said — much like Bigelow Aerospace's inflatable modules, which have already been deployed and tested in low-Earth orbit.
Water would be a big part of the space coach's body, too, according to the study. Packed along the habitat modules, it would provide good radiation shielding. It could also be incorporated into the fabric walls themselves, freezing into a strong, rigid debris shield when the structure is exposed to the extreme cold of space.
Rotating the craft could also generate artificial gravity approximating that of Earth in certain parts of the ship, researchers said.
Slashing the cost of space travel
The dependence on water as the chief propellant would make the space coach a relatively cheap vehicle to operate, researchers said. That's partly because electrothermal engines are so efficient, and partly because the use of water as fuel makes most of the ship consumable, or recyclable.
Because there are fewer single-use materials, there's much less dead weight. Water first used for radiation shielding, for example, could later be shunted off to the engines. Combined, these factors would translate into huge savings over a more "traditional" spacecraft mission to Mars using chemical rockets, according to the study.
"Altogether, this reduces costs by a factor of 30 times or better," McConnell told SPACE.com. He estimates a roundtrip mission to the Martian moon Phobos, for example, could be made for less than $1 billion.
A space coach journey would also be more comfortable, McConnell added. The ship would carry large quantities of water, so astronauts could conceivably grow some food crops and — luxury of luxuries — even take hot baths now and again.
McConnell and co-author Alexander Tolley published their study last March in the Journal of the British Interplanetary Society.
A fleet of space coaches?
McConnell envisions space coaches cruising around the solar system, each individual vehicle fueling up with water in low-Earth orbit when the need arises. In the future, fuel could be sourced along a space coach's travels — for example, water could be mined from an asteroid or a Martian moon.
Parts could be swapped out and upgraded on orbit as well, helping to keep the space coaches in good operating condition for several decades, McConnell said. Each mission undertaken from low-Earth orbit would be far cheaper than anything launching from the ground.
McConnell thinks an entire fleet of space coaches could one day populate the heavens, flying a variety of different flags — as long as somebody takes the initial plunge.
"If one party decides to do this, I think it would spur a lot of other activity," McConnell said. "I think countries wouldn't want to get left behind."
From vision to reality
No huge technological leaps are required to make the space coach a reality, McConnell said. Bigelow's expandable habitats are already space-tested, for example, as are several varieties of electrothermal engine.
"There's not a lot of new technology that needs to be built," McConnell said.
Electrothermal engines that use water as fuel, however, have not been flight-tested, so some work needs to be done on the propulsion system. McConnell envisions holding a design competition for the engines, as well as one for the overall ship design — cash-reward contests that would be like smaller versions of the Google Lunar X Prize, which is a $30 million private race to the moon.
Once winners of these competitions emerge, ground-testing and, eventually, flight-testing would follow. McConnell declined to put forth any specific timelines, but he's optimistic about the possibilities.
"I think things could happen very quickly," he said. "It's really just a matter of convincing decision-makers that this is worth getting into."
The way the article is written, it seems like the guy promoting the idea is saying, “We still have bugs to work out, but all we need is money from somewhere . . .”
From what little searching I did, this seems to be the method of choice -
http://www.nasa.gov/vision/space/travelinginspace/future_propulsion.html
"It runs on *water*, man!"This is a little bit interesting; Asimov's standard engine for jettin' around the Solar System was fission-based, the nuclear pile heated water to steam.
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Yep - I’m aware of that. The Mass it will use is not nearly as heavy as H2O. It can use electricity from any source solar or nuclear to do the job it’s doing. It’s estimated that a 1MW Vasimr system could get us to Mar in 13.
http://www.thespacereview.com/article/1690/1
Summary: Vasimr could get us to Mars in 39 days with direct, constant acceleration. It would use Argon as the fuel source - a LOT lighter than H2O.
I'm about 40% of the way through the faux-ars-nouveau movie Sky Captain and the World of Tomorrow. It reminds me of the children's literature I devoured a half-century ago, which echoed a forgotten motif of the 1930s -- the astonished appreciation of how fast progress could happen, and the breathless speculation about what could happen next.
There was reason for soaring optimism. A single generation had gone from clattering motorized kites to ocean-spanning aluminum monoplanes. From horse-and-buggy to the first car to travel a mile a minute (a Stanley Steamer). To the first car to travel two miles a minute (a Stanley Steamer). From telegraph to commercial radio programs. From still photos to motion pictures with sound. "The Wizard of Menlo Park" cranked out a continuous stream of new marvels from his "invention factory."
So, who slammed on the brakes? Who killed the dream? And why? Answer these questions, and maybe I will indeed get to retire on the moon.
how are you going to change that energy into something you can use for thrust?
—
Explode it against a preasure plate a ka the Orion Project from the early 60s, before the US went wimpy on nuclear power.
Steam, water - all green, which is in.
LEO per pound costs:
Low - $1672/$2341
High - $5806/$6452
Geo syc orbit per pound costs:
Low - $5051/$7071
High - $13,953/$15,504
How high you want to lift the water depends on the orbit picked for the fueling/refueling - costs are comenserate. The further into the gravity well you go for your fuel (water), the more fuel you need to enter and depart.
Exactly how much water fuel does one need to get to Mars? The faster one goes the more water one needs.
BAH ... Orion or bust.
forget about the solar BS
holding multi tonnage of water
No small step there getting that water into orbit.
this is a solar system ship...a huge non take off and landing type of vessel meant for moving large amounts of people/freight...you take off and land with separate small units...get just enough water on board to mine the ice farther out in the solar system..either from Keiper belt ice or in closer from ice moons(europa etc) that have much lower gravity to fight...
Correct. The proper term for the water would be reaction mass, not fuel.
Regarding getting the water into orbit...chemical rockets would not be the way to do it. Freezing the water and launching it with electromagnetic rail guns or ground based lasers would be the way to go. If humans don't have to go along for that ride there would be no limit on how many gees the launch system could generate.
Short term you are correct, but long term the same drive system could be attached to large chunck of ice in the outer system and boosted anywhere we need it. Short term see my earlier post about using ground based rail guns or lasers to boost to Earth orbit.
chunck = chunks
Nice thought, that stops short of the full solution. Example: rail guns cannot put anything into orbit.
Lasers would be the best choice. Rail guns would be a good solution in low gravity/thin atmo situations. When I wrote that I wasn't thinking about the problems with using rail guns out of a deep gravity well with dense atmo. I assume that is why you say rail guns can't put anything into orbit.
Lasers can't put anything into orbit, either.
Either could (theoretically, neglecting the problems with being a burning ball of plasma) launch something to orbit altitude, which is not the same as putting something into orbit. The problem is that you've got to apply another large delta-V at some point and in the right direction, to actually put the vehicle in orbit.
Best case from the flaming ball of plasma perspective is to launch straight up -- which happens also to be the worst case from the perspective of applying a delta-V to put the thing actually into orbit.
Best case from a delta-V perspective has you launching at a pretty low elevation angle, which roughly doubles the amount of atmosphere you'd have to be a flaming ball of plasma in.
Assuming you surmount that problem, there's still the problem of getting the water from where you put it in orbit, to a position where it can be loaded into your space ship (which, in a practical sense, means your target vehicle will have to do the rendezvous).
You've no doubt spotted the fly in the ointment here: how much delta-V (and how much propellant) will have to be expended just to fuel your water-powered space ship?
Note, too, this little nugget:
McConnell envisions space coaches cruising around the solar system, each individual vehicle fueling up with water in low-Earth orbit when the need arises. In the future, fuel could be sourced along a space coach's travels — for example, water could be mined from an asteroid or a Martian moon.
Yup .... all you've got to do, is just pop out of that interplanetary trajectory, down into Low Earth Orbit; or, into the orbit of an asteroid or a Martian moon.....
How? Does our author understand the orbital mechanics of his "simple" solution?
Chances are the author doesn't understand the issues. To keep the system going they will have to boost the reaction mass to match orbit with the spacecraft.
Recently read a science fiction book which described a similar concept, but I forget what the drive system was. May have been solar powered ion drive. That author called them cyclers with three cyclers continually cycling between Earth and Mars.
Done right, once the cycle is going the system won't require a lot of additional delta v. Shuttle craft would be required to boost cargo and consumables to matching orbits, but the cyclers themselves would be very efficient.
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