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."
It depends on how large the spaceship is going to be, of course, but I don't think they could even get all that water to low earth orbit for a billion dollars. Interesting idea, though.
/johnny
Water is only the mechanism to transfer solar energy into motion.
It would be the same as calling our cars rubber powered since the tires provide the force against the road to move us.
Read some interesting sci fi stories about this technology. The primary problem is having a platform to launch from in space.
Yeah, getting the water was my first thought as well. However not having to launch from earth is always a good idea.
I’m not convinced they did the math.
What’s the specific impulse of water used in this way?
The problem is.... it will cost one hell of a lot of money to find water and then move it to a place where it can be put in the tank.
The practicalities of moving huge masses of water into and between orbits are not to be trifled with.
Steam-powered spaceship!
I spent last weekend at Old Sturbridge Village with my CubScout pack. Sturbridge is a museum set up as a replica of an early 1800’s New England village. While visiting the blacksmith’s shop, the smith qupped that back then everything was powered by fire and steam. My answer was that it still is...
I wonder why they saved that for the third from last paragraph.
Depends. If you could create really high-temp, high-pressure steam, then you could probably achieve a pretty good Isp.
But I'm pretty sure they didn't do the math.... the problem of getting water from source to space ship is pretty unattractive.
Cool.
They can get it from the moon
I used to have one of those water rockets as a kid. You’d fill up the plastic rocket half full with water, then pump compressed air into it, pull the release latch, and the rocket would shoot up about 50 feet and land on the roof. Pretty fun stuff.
Yeah, me too.
Fund to dream about, even if it never happens. Collectivism has a way of crumpling these kinds of dreams and tossing them into the waste basket. People will be more occupied with dreaming of how to find a crust of bread.
Water weighs a lot (about 8.3 lbs per gallon), could it add to the amount of thrust needed to move and maneuver? There must be fuels with as great or greater energy capacity than water and less weight.
How many grams of Uranium would it take to power a small reactor to power a space ship for years? Would it’s reactor weigh more than all the weight needed for other fuels?
Our modern navies seem to think, for large ocean going vessels - aircraft carriers - and vessels with trips that last a very long time - strategic submarines, that nuclear power is the best? Why would space travel be any different?
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