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Underground > Laboratory >

Fusion Drives

09:51 / 23.01.03

From New Scientist,

The journey time from Earth orbit to Mars could be slashed from six months to less than six weeks if NASA's idea for a nuclear fusion-powered engine takes off.

The space-flight engine is being developed by a team led by Bill Emrich, an engineer at NASA's Marshall Space Flight Center in Huntsville, Alabama. He predicts his fusion drive would be able to generate 300 times the thrust of any chemical rocket engine and use only a fraction of its fuel mass.

That means interplanetary missions would no longer need to wait for a "shortest journey" launch window. "You can launch when you want," Emrich says.

I wonder if this could signal the start of renewed interest in space exploration and serious attempts to establish an outpost on Mars within the next 50 years. Remember, the dinosaurs died out because they didn't have a space program.

10:29 / 23.01.03

LA - since the end of the Cold War and all that, I thought Nasa had slowed down as the space race had lost momentum. Even though I really wish people would try and sort it out (and not just in a Star-Ark way - ie to escape the poluted planet) - I don't genuinely think this'll change things too much as the will to explore (for want of a better word - has diminished. Out-post on Mars sounds great, but they haven't even got one on the moon. I can't even recall when the last moon landing was. Do you really think they'll pull their collective finger out and try and make this work?

10:42 / 23.01.03

I've no idea if things will really change and you are absolutely right about the lack of enthusiasm for space exploration.

Having said that, I think that Mars is different from the Moon in the sense that there was a great deal of disappointment that the Moon was just a big rock. Mars, on the other hand, is a whole planet which may have held life at some point and could provide minimal resources for an outpost. The biggest problem has always been that it takes too long to get there.

Also, on a more cynical note, a big space program now could distract people from the war on terrorism as well as providing another way to boost funding into military research.

14:05 / 23.01.03

The current paradigm is to do more missions for less money - there are a lot of satellites in the sky, and space shuttle launches are no longer headline news here in the shadow of Canaveral. Near space is routine.

A big press for Mars, though... that'd change things. Especially if there was a way to go: "See? Cheaper than we thought!"

On the other hand, this seems really way out. I mean this describes one hell of a hot fire:
Emrich is proposing a bold solution. He wants to use microwaves to heat the plasma to 600 million kelvin, triggering a different kind of fusion reaction that generates not neutrons but charged alpha particles - helium nuclei. These can then be fired from a magnetic nozzle to push the craft along.

And this seems like an awfully big 'if':
If fusion researchers can ever achieve stable, break-even fusion, Emrich believes a full-scale fusion drive - perhaps 100 metres long - could be ready and waiting within two decades.

Two decades, somehow, even seems too long. If he's got the hardware and someone comes up with the fire, then I'd be surprised if the drive took that long to build. I just don't know how you'd get the drive in a rocket ship without melting it or cooking the astronauts.

I've emailed a couple people who might have more insight....

17:31 / 23.01.03

One reply:

The temperature of the reaction's no problem - it
can't get at you through convection because there's no air in space, and with that kind of power you can carry plenty of radiation shielding. The magnetic field might contain radiation as well... and now that I think about it, it's going to be what's holding the plasma (you have to keep it from touching anything to avoid losing heat and cooling to the point where it no longer fuses). You probably wouldn't be adding anything to the background alpha-particle content of
space - remember, as the H-hiker's Guide points out, space is big, and the Sun's pumping out quadrillions of times more hydrogen nuclei (alpha particles).
The fly in the ointment is this phrase:
If fusion researchers can ever achieve stable, break-even fusion...
That's been "two decades away" ever since the mid-1950s.
For another perspective on plasma rockets, look here and here.

I met one of Chang-Diaz's postdocs in the fall at a conference in Houston and he told me they were in some kind of bureaucratic snit-fit involving Marshall Spaceflight Center in Alabama...maybe this guy's proposal has some connection to it.

17:33 / 23.01.03

On the other hand, there's also been noise lately about a messier way to do nearly the same thing.

Which might be a little scary.

17:55 / 23.01.03

Interesting. Your take on current small projects in space exploration is spot on, grant. But I thought that fusion really was getting to the break even point these days. Honest.

A bit of a google doesn't reveal anything happening in the field recently though. Almost as if they aren't making any progress...

20:23 / 23.01.03

An additional reply:

Nobody's proposed a nuclear-powered launch from
Earth's surface since
Project Orion, Freeman Dyson and Ted Taylor's
plan to use the detonations of
multiple nuclear *bombs* to blow an
ocean-liner-sized manned vehicle to
infinity... and beyond (their motto was "Saturn
by 1970"). It wasn't as
crazy as it sounded - it would only have required
two explosions to get it
out of the atmosphere, and at the time (late
'50s- early '60s) we were
setting off dozens of nukes in the atmosphere
every year in Nevada.

The idea was that the ship would ride on giant
shock absorbers, with a thick
steel plate between it and the nukes... it
wouldn't be around the detonation
long enough to soak up enough heat to vaporize
much of the steel. The Test
Ban Treaty of 1963 pretty much scuttled the
program, just after they'd done
scale model tests with conventional explosives.

05:42 / 25.01.03

Forget the heat. Won't the shockwave destroy the craft? If not the outer hull then perhaps the inner fragiles considering that the thing will go from zero to sixty miles per second in an instant. Also, won't the electromagnetic pulse produced by such an explosion render the whole thing useless?

gentleman loser

16:56 / 31.01.03

Not to pour cold water, but this article makes some valid points:

Media Hype Alone Cannot Fuel The Space Program

So, a mission to Mars is still probably a long way off, even if the U.S. was willing to fund it. When some environmentalists and anti nuke activists figure out what all of this means, they are bound to pitch a fit as well.

Supposedly the technology can be made safe, but how safe is the question? I presume that these rockets will not be operated in the Earth's atmosphere, but would be launched on a chemical booster.

What we're talking about here is likely more NERVA type rocket research. Here's a photo of one test I can't find any hard numbers on radiation hazards produced by these type of engines.

Some more info on nuclear engines.

grant:

I just don't know how you'd get the drive in a rocket ship without melting it or cooking the astronauts.

Someday they might look like this.