Fusion Reactor in Space; When will it happen and what will the implications be?

I understand the technology currently available is not sufficient to build one but we are getting closer, I believe China is currently working on a Cold Fusion Reactor.

My question for the forum is assuming we can eventually get it to work,
1. When do you think that will be(Will China beat us to it)? Thiis pertains to both ground based and spaced based applications.
2. Speculate on the speed implications, would this be a good form of propulsion to get to the moon, to mars, or beyond? Supposedly Fusion Power can create gobs of power, many times more than fission.
3. Would we want to match this technology(fusion reactor) with another form of propulsion as such with a Turbo-jet?
4. What are the current and future limitations to a Fusion Powered Space Craft?

I know this is a bunch of speculation, but you have to start somewhere. Any help would be appreciated.


[edit on 10-4-2006 by Low Orbit]

Obviously you're coming into this with the Space-Channel idea of fusion power. First, no, no Cold Fusion Reactors are currently in production. Many people want to discover cold fusion, but no one has succeeded in TRUE Cold Fusion.

As for Fusion itself, a fusion reactor is simply a power source, not an engine unto itself. Also, it's not as self-sustaining as people think. Most people seem to think of it like Spider Man 2, once you turn on the switch, it'll stay on indefinitely. In truth, the idea of "self-sustaining" for Fusion Power is that the energy produced by the fusion process is enough that it keeps the heat up high enough for the fusion of other hydrogen atoms into helium atoms to continue. There would also then be leftover heat and light that could be harvested.

However, the energy that would be harvested wouldn't be anywhere near what would be required to split the helium back into Hydrogen, and you would still constantly need more Hydrogen to fuel the process. The sun keeps going because, simply put, it's got just massive amounts of Hydrogen and doesn't have to worry about running out any time soon. It still will eventually though.


Now, if Fusion did come out, a Fusion Powered space craft would need to have a drive system that can turn raw energy into thrust. That's the important thing you want to find for space travel, a sort of "warp engine". Without this, fusion-powered space-craft would be useless.

Now, we'll probably find a way to make Fusion work within thirty years, and cold fusion perhaps another century after that. Cold fusion would be useful since you could start putting it on things like space-craft and cars and stuff without having to worry about a massive containment system like what is currently needed (we can do Fusion currently, just not sustainable Fusion).

In the future, I think Fusion will end up being something of a pipe dream - lots of possible uses for it, but none that will actually jump right out. Nuclear power (fission) is very useful since it can be done with a small amount of fuel, and is actually very safe.

And no, I don't think China will beat us to it - because the nations of the world will really make it a joint effort. At least I would hope so.

Would there be any way to pair a fusion reactor with a fission reactor so it recycles some of its fuel?

No, there isn't - due to the fuel that would be used in particular, and the laws of physics in general.

In particular, the easiest thing to fuse is Hydrogen. With only a single proton for its nucleus, it fuses most readily with other Hydrogen atoms to produce Helium + some energy. The easiest thing we have to split in the process of fission is Plutonium, but I'll just go ahead and say Uranium since we're all familiar with it. Splitting Uranium-238 produces two smaller atoms with a proton count of 169 plus some energy.

And so splitting or fusing with these two only would be very difficult to do.

But beyond that there's a tipping point in physics. It's called Iron.

You know Supernova? They represent what happens when Fusion reaches that tipping point.

No, it's not that it releases so much energy, it's that anything below Iron CAN be fused to produce energy, and anything above Iron CAN be split to produce energy... but splitting or fusing above or below Iron will only CONSUME energy.

So, when a star goes supernova, it's because it got hot enough to fuse atoms into Iron (our sun will not do this - it'll fuse into Carbon-Neon at best). Once it ran out of that fuel, fusion ceased, the star collapsed, and any fusion that hadn't yet occurred was suddenly forced in to happen in the blink of an eye.


So, unfortunately, you couldn't produce a twin fusion-fission infinite energy reactor. The amounts of energy given off by the fusion and fission processes are no where NEAR the amounts that are required to force the opposite process in the other.

Yarium, thanks for the info, it has been helpful.

A follow up question,

So you are telling me we can turn the sun's rays into thrust(through solar sails) but we don't have the technology to turn fission or fusion energy into thrust? This baffles me?

Well, a solar sail works very differently from what you may think. In essence, the solar sail "catches" photons like a wind-sail, using it to provide momentum.

Now, you couldn't create a mini-sun to do this for you, because of Newton's laws, one of which being;

"For every action there is an opposite and equal reaction."

So although that photon will give some push on the solar sail, the amount of push it gives will only equal the opposite amount of the push against the mini-sun that sent out the photon.

Essentially, it's like Wil-E Coyote and his powermotor in the bucket of water attached to a skateboard. It doesn't work in real life because, although the motor is pushing the skateboard forward, the bucket of water is pushing in the opposite direction just as much, and so since both are attached to the skateboard, it doesn't go anywhere.


So, the lesson here:
Sun power is not turned into thrust, but into momentum through solar sails - which is why we can't turn fusion or fission, or hydro or wind, or really any straight-up power source into thrust. The best we have is a physical propellant, because of that really trippy Law of Motion.

Ok, so if fusion and fission arent practical for thrust. Could we send out Satelites with lasers in earth's orbit/the moon's and mar's orbit to provide supplemental power to help lift future crew and cargo via these laser/solarsale for space travel and maybe rockets to boost the object out of orbit.

Would this work, is it practical, thanks again for all the answers.

Actually, yes. There's a few research projects looking into using lasers and spinning reflective discs to propel them up into the air (though it's not a solar-sail, it creates little explosions like a car engine does, except it utilizes the natural elements in the air and the heat created by the laser being focused by the mirrors in the disc). The trajectory has to be perfectly straight, as does the laser beam - which is why this project hasn't gotten far off the ground, pardon the pun.

As the laser starts going through the air and atmosphere, it loses coherency and strength, since its running into more and more little particles and atoms in the air - which cause the beam to scatter and weaken. Also, gusts of air causes the disc to veer off course.

Now in space, it would be simpler at first, but the sheer size of space makes many difficulties - one of which being keeping things on course. A laser-beam travelling from the moon (where there is no atmosphere) not only would have to be constantly correcting its position due to the moon and earth's rotation around their axis, each other, and the sun - but also be scheduled and calculated in advance with extreme percision - since it would still take light some 5 minutes to get to Mars - and by then the satellite has moved somewhere else.

Not only that, but for something as necessarily precise as a laser, they might even have to take into account how light itself might curve due to gravity.


In the end, a Solar Sail using the sun's natural light is a great idea, and would do a lot better than a laser - although the idea behind it is essentially the same.

So travelling huge distances using a directed laser would be difficult because of the distortion of space-time through gravity. Would it be possible to use the distortion and redirection of light caused by the warping of space to direct, and steer a sail?

from what I understand, the main problem with interplanetary spacetravel is that fuel is too heavy and too expensive to carry.

In the future, might it be cheaper to beam fuel to spacecraft rather than tow-it-along.

Concept: Have a few Satelites that act as fuel stations circling the planet that can microwave the energy to earth and back. These satelites will aid spacecraft leaving and arriving planets.

In the short future, 20-30 years, might a hybrid(laser based and rockets) space shuttle be the best option for quick space flight from the earth to the moon/mars and back again.