Nuclear Fusion and Its Future Uses In Spacecraft

The other day I got confused about fission and fusion. So, what is the difference? Well it’s like the difference between chalk and cheese, one is cuddly and the other is prickly and very hard to get to know.

Fission is hard to get to know as it is the reaction that occurs in nuclear reactors in power stations. Nuclear fission happens when high-energy neutrons are thrown at heavy uranium atoms splitting them and causing large amounts of energy, radiation And waste.

Fission reaction

Unfortunately nuclear reactors have got bad publicity because of a few accidents and because of the waste that is produced. The publicity I think is not warranted as when people think of nuclear things the first thing that comes into their minds is a nuclear explosion. A nuclear explosion is impossible when fission is used for nuclear power as a nuclear explosion requires the atoms to be thrown at each other rather than in a nuclear reactor where they are gently brought into contact with each other.

Nuclear energy could have really helped us produce relatively clean energy compared to the other ones that we are using today which cause damage to the environment and a lot of pollution. I hear you say though what about the radioactive waste? That is a problem and the worst thing about it is that it stays around a very long time.

Disposal has been by burying it in a very big hole. This is where the nuclear waste is disposed of, so if you are looking to buy a house  or if you want to know where not to take up a job then have a good look. If nuclear power was a long term project than I would have thought that disposing of the radioactive material in space would be a better idea. How about setting it on a course for the sun?

Of course there is the problem of getting it out of the atmosphere. Perhaps a large balloon could take it to the outermost limits then a small spacecraft fly by hooking it up and taking it into orbit. From there speed could be increased around the Earth and from there the waste slingshot at the Sun.

Nuclear fusion on the other hand is great as there are no waste products to talk about. I expect as nuclear fusion has the word nuclear used there will be all sorts of protests by ignorant people of our society but it is totally unfounded. Instead of splitting atoms nuclear fusion makes helium, neutrons and an enormous amount of energy, just like a nuclear bomb or the sun, but controlled.

Nuclear fusion

Nuclear fusion is very hard to carry out as trying to force two hydrogen atoms together is like trying to force two extremely strong magnets together as hydrogen atoms are both on the same positive charge. The only reason the sun gets away with it is that the gravity is very very strong. Of course pushing these hydrogen atoms together is hard work but if we put in a lot of energy getting them to come together to produce fusion then that energy could be more than the energy we get out from the actual fusion reaction, which makes the whole thing a big waste of time.

The Sun by Hubble

Pressure and temperature (six times that of the Sun) is needed for nuclear fusion and this is achieved by using lasers, Magnetic fields or ion beams. Nuclear fusion has been produced for six minutes and 30 seconds but this isn’t really a replacement just yet for conventional fuels as it would not be much fun watching the TV for six minutes and 30 seconds, I can just see everybody sitting down at dinnertime and all the roads, parks and towns going quiet and who would say who could watch what? More could be built but, well it gets a bit silly then.

Progress is ongoing and there is a lot of research going on in this area. Unfortunately for the last 50 years scientists have been saying that they will have a useful type of fusion in the next 15 or 20 years but they are still saying that. Whoever develops an economical power source like this will be the talk of the town so it is quite a big thing.

Cold fusion other than nuclear fusion has been suggested but has never been reproduced since the experiments years back. The debate on cold fusion keeps coming back as it would be such a breakthrough. Cold fusion is fusion at room temperature. There are many obvious advantages to this.

There are many research facilities working on nuclear fusion all over the world such as ITER, HIPER & JET.

So what’s the point of going to all that trouble investigating nuclear fusion if it doesn’t do anything? Well it does. There is the obvious one of producing lots of nice clean power and not producing any waste to speak of. This power could be very useful to the military, especially the Americans with the nuclear powered aircraft carrier. Nuclear fusion powered spacecraft have been suggested in the past and with fusions extra power per unit volume and lack of waste fusion power would be the power of choice.

Microwave fusion jet

Building a nuclear fusion powered spacecraft is very similar to building a car on earth that does 7000 more miles per gallon than the cars of today. That’s quite an improvement and will allow a spacecraft to get to Mars in 50% of the time of anything else we have today travelling twice as fast. That cuts down time quite a bit but is no wormhole but it’s better than nothing. Speed of travel to Mars is very important because of the effect of radiation on the poor weak human frame and the harmful effect of weightlessness on the body. Fuel is not a problem either as hydrogen as it is available in space in small quantities but in much larger quantities in the atmosphere of most planets. This means that the occasional dip into the atmosphere of a suitable planet would fulfil the needs for the next part of the spacecraft’s journey.

Two types of spacecraft under research are the Variable Specific Impulse Magnetoplasma Rocket (VASIMR) and the gas dynamic mirror propulsion system

Round fusion powered spacecraft

VASIMR is really a plasma rocket as it uses hydrogen. It  is a precursor to  a nuclear fusion rocket. It converts hydrogen to plasma and then ejects it out of the back as plasma. Travelling to a planet in the solar system would require a constant acceleration and then at the halfway point turning around and then producing a constant deceleration. A variable exhaust plasma rocket could be extremely useful for a satellite in orbit as well helping it to maintain station.

Tube like fusion powered spacecraft

The gas dynamic nuclear fusion propulsion system is being developed simultaneously with VASIMR. In this engine, a long, slender, current-carrying coil of wire that acts like a magnet surrounds a vacuum chamber that contains plasma. The plasma is trapped within the magnetic fields created in the central section of the system. At each end of the engine are mirror magnets that prevent the plasma from escaping out the ends of the engine too quickly. Of course, some of the plasma is allowed to leak out to produce thrust.

Gas dynamic fusion propulsion

It looks as though nuclear fusion is the future but when that future is coming seems to be anyone’s guess. I can see nuclear fusion replacing the ordinary battery in the far future and therefore that annoying watch battery that keeps running out will be a thing of the past.

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