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Researchers led by NASA's former chief technologist are hoping to launch a satellite carrying water as the source of its fuel. The team from Cornell University, guided by Mason Peck, want their device to become the first shoebox-sized "CubeSat" to orbit the moon, while demonstrating the potential of water as a source of spacecraft fuel. It's a safe, stable substance that's relatively common even in space, but could also find greater use here on Earth as we search for alternatives to fossil fuels.
Water is a way around this issue because it is essentially an energy carrier rather than a fuel. The Cornell team isn't planning to use water itself as a propellant but to rather use electricity from solar panels to split the water into hydrogen and oxygen and use them as the fuel. The two gasses, when recombined and ignited will burn or explode, giving out the energy that they took in during the splitting process. This combustion of gasses can be used to drive the satellite forward, gaining speed or altering its position in orbit of whichever desired planet or moon is the target.
Solar panels, with high reliability and no moving parts, are ideally suited to operate in zero gravity and in the extreme environments of space, producing current from sunlight and allowing the satellite to actively engage on its mission. Traditionally this energy is stored in batteries. But the Cornell scientists want to use it to create their fuel source by splitting the on-board water.
Source: http://phys.org/news/2016-09-space-rocket-fuel-power-revolution.html
(Score: 1) by RS3 on Thursday September 29 2016, @11:05PM
It's a bit difficult- lossy and expensive- to "ship" electricity from sunny desert areas to populated cities. I've long envisioned large solar-powered generating systems out in desert areas, or floating on the ocean, producing hydrogen and oxygen from water. You can pipe the H and O with far less loss than conduct electricity over long distances. True it would need to be built really well and well protected, safety shutdowns, etc. You could then run the H and O into fuel cells for electricity or use it for vehicles, etc...
(Score: 2) by Immerman on Thursday September 29 2016, @11:13PM
Have we worked out any way to pipe H2 long distances without massive losses though? Even at atmospheric pressure, you're still dealing with roughly zero partial pressure on the outside of the pipe wall, so you need a wall that H2 can't flow through.
(Score: 1) by RS3 on Friday September 30 2016, @12:39AM
I don't know about these things of which you speak. You're saying H2 can leech through things? Such that over long distances, the huge surface area of the pipe would be a sieve? Could we coat it with PTFE or something similar? How about a small gauge rail system with canisters?
(Score: 0) by Anonymous Coward on Friday September 30 2016, @01:33AM
Send the hydrogen-filled canisters through the Hyperloop.
(Score: 2) by Immerman on Friday September 30 2016, @05:37PM
In case that wasn't humor...
Yes H2 is pretty much the smallest stable particle in the universe - a tiny "barbell" about as long as a Helium atom is wide, and considerably narrower, capable of slipping right through most molecular lattices. One of the major obstacles to hydrogen usage is that H2 will rapidly leak right through the walls of pretty much any container you put it in. I looked for info suggesting that PTFE could be used for containment, but from what I found it sounds like it's only good by the generally low standards of polymers. And strings of canisters only make it worse by increasing the surface area for a given volume of hydrogen.
That's not to say that it couldn't be done, but it's worth asking whether it would actually be significantly more efficient than standard power lines, especially after the higher construction and maintenance costs are factored in (in energy as well as money).
And of course there's also another alternative for transporting electricity long distances - superconducting power lines. As I recall there's long been a project in the works to build such a line between Europe and the vast solar potential of the Sahara, stalled in large part due to the political instability in Africa rather than any technical or economic objections.
(Score: 2) by WalksOnDirt on Thursday September 29 2016, @11:29PM
The losses of energy of gasses flowing through a pipe depends on the speed. If you are willing to wait forever then it's free. If you want if faster it gets expensive.
(Score: 1) by RS3 on Friday September 30 2016, @12:42AM
Would larger ID pipe cause less loss?
(Score: 2) by WalksOnDirt on Friday September 30 2016, @01:17AM
Yes.
(Score: 2) by Immerman on Friday September 30 2016, @05:41PM
I hadn't even considered those losses, and they're definitely worth factoring in.
Hydrogen specifically though offers some unique challenges, because it can leak right through seamless steel, and pretty much anything else. An H2 molecule is the smallest stable particle in the universe, and can fit through all but the tiniest intermolecular gaps.
(Score: 2) by stormwyrm on Friday September 30 2016, @12:31AM
If you had an easy way to make hydrogen, why not turn that hydrogen into methane? Last I checked, storing methane safely for extended periods is comparatively easy: in my own kitchen, I have some stored methane in a gas cylinder. Transporting methane long distances is also a lot easier: it's something the petroleum industry has long done. Just about any ordinary motorcar can very easily be modified to use methane as fuel instead of petrol. The analogous problems for plain hydrogen don't yet seem to have practical solutions. There seems to be something called the Sabatier reaction [wikipedia.org] which can convert H and CO2 into methane and oxygen with a nickel catalyst. Methane produced this way would be carbon-neutral, provided that the hydrogen it was made from were also carbon-neutral.
Numquam ponenda est pluralitas sine necessitate.
(Score: 0) by Anonymous Coward on Friday September 30 2016, @04:56PM
(Score: 0) by Anonymous Coward on Saturday October 01 2016, @12:37AM
That's what the Fischer-Tropsch process [wikipedia.org] is for. It's already being used by petroleum refineries on large scales today.
(Score: 2) by Immerman on Friday September 30 2016, @05:45PM
An interesting idea. I would wonder though how losses to inefficiencies in the process, and the energy required to collect and concentrate CO2 to feed it, would compare to those of electrical transmission lines.