Laser fusion and the internal combustion engine

As Formula One continues to deliberate upon the nature of the new engine formula due to commence in 2013, an international collaboration involving nuclear, plasma and laser physicists, is considering a petrol/diesel engine model of commercial fusion power.

In the interests of efficiency, Formula One is moving towards turbocharged, KERS-assisted, petrol engines, with the added possibility of direct injection to boot. However, whilst the motor industry debates the relative merits of petrol and diesel engines, no-one has yet seriously raised the dreaded prospect of introducing the D-word into Formula One.

Strangely, diesel engines and petrol engines have direct analogues in the world of laser-driven fusion. In the latter, a pellet of deuterium-tritium (D-T) fuel is compressed in a target chamber to very high pressures by blasting the outer surface with a collection of lasers. The outer surface of the pellet is transformed into a plasma, and it is the plasma pressure which compresses the D-T fuel to the temperature at which nuclear fusion can be triggered.

As explained by Mike Dunne, of the Rutherford Appleton Laboratory, in the freely-downloadable May 2010 issue of Physics World, once the D-T fuel is at the necessary high density, the fusion can either be ignited by a separate laser, which thereby functions as a sparkplug, or it can be triggered by the temperatures produced by the compression alone (p32). The former case therefore corresponds to a petrol engine model, whilst the latter corresponds to a diesel engine model.

Exploiting such laser-driven fusion as a source of commercial power, requires the design of a fuel cycle, in which multiple D-T pellets can be injected into the target chamber, ignited, and removed, every second. Dunne claims that "the high-repetition-rate technology used in the welding and machining industry" could be used to this effect.

Possible methods of improving the efficiency of the combustion in an internal combustion engine include the use of laser sparkplugs, and conversely, perhaps the power-generating capacity of laser fusion could be improved by developing some analogue of the direct injection systems used on certain modern internal combustion engines. An interesting reciprocity.