Nuclear fusion strategies

Broadly, there are two realistic competing strategies for sustainable nuclear fusion. The first is plasma confinement in a large torus and the second uses laser induced implosion. The first approach has been the one that has gained the most attention in the press and with the comissioning of the ITER project to be housed in Cadarche, France. Using superheated Deuterium and Tritium plasma, the ITER reactor confines the plasma using a magnetic field and heats it using Ohmic heating (the heat generated when a current passes through a conductor). The plasma is held in a large torus. The heat is carried away from the reaction chamber through neutrons.

ITER fusion reactor
The second approach is to use a bunch of high energy lasers focussed on a small almost perfect sphere containing the reaction fuels and use the pressure from the resulting implosion to drive a fusion reactor. HiPer goes one step forward by having a gold cone inserted into the fuel capsule. The fuel capsule is first compressed using lasers and then a second laser superheats the gold cone, converting it into a plasma, which then compresses the fuel into a high density at the tip of the cone. This type of reaction is called a fast ignition reaction.

HiPER Reactor
Aside from the physics, the other difference between the two approaches is cost. The first will cost around $10Billion, the second around $1 Billion. However, there is a much more significant criteria here - competition. Governments are notoriously bad at selecting and developing technologies and so competition is one way to ensure that at least two different approaches are attempted.

Here is an even better suggestion. A couple of entries back, I suggested having a sort of government sponsored X-Prize of an order of magnitude greater than the current X-Prizes awarded for space colonization. Why not use a similar approach with nuclear fusion? Who is to say that these $billion+ dollar projects will ever reach the final answer.
Maybe there is a much more modest approach that will also yield sustainable fusion. For example, there are some tantalizing hints with recent results from an experiment carried out by Mosier-Boss and Szpak that came out just this year. This experiment is similar that infamous cold fusion experiment by Pons and Fleischman but seems to show that there are nuclear reactions going on. Reproducing this experiment is hard, which makes me skeptical but still...

While I am always skeptical of things that appear to good to be true (because they usually are), a prize awarded for the first commercially feasible fusion reactor would be an unambiguous way to say that someone's done it and it would sort out the good physics from the dodgy physics.

Chinese moon rover

The Chinese are bent on moon exploration and I can already see a mini-space race in the making. Unlike the West, China has no issues about using nuclear energy in space as is demonstrated by their intention to power their moon rover with nuclear energy. Indeed if we are really serious about establishing colonies on Mars and on the Moon, and further afield, there is no choice but nuclear. The power that one can derive from solar energy decreases as the square of the distance from the sun. Mars is approx 1.5 AU from the sun (with a max. distance of approx 1.6 AU). This means that the power that we are able to derive from the sun is between 2.2 - 2.6 times weaker than on Earth. This means that either the solar panels need to be twice as efficient or the collecting area twice as big to get the same power as on Earth.
Batteries are also problematic. For example, if we powered the Galileo space probe using conventional batteries instead of Radioctive Thermal Generators (RTGs) and expected the same duration for the mission (70000 hours), the probe would have batteries weighing 47T! This does not include the fact that the batteries themselves need to be kept warm.
Robert Zubrin in his excellent book Entering Space, discusses the use of nuclear power in space. He goes one step further and recommends the use of an actual nuclear reactor.

Not only do we need RTG's, we need to move beyond them to actual space nuclear power reactors that use nuclear fission, rather than mere radioisotope decay, to generate tens or hundreds of kilowatts. The reason for this is very simple. On Earth, it has been said, knowledge is power. IN the outer solar system, power is knowledge.

Perhaps its time to get past the neo-luddites and start to look at nuclear power more rationally.