Nuclear Fusion and Starship design – a few thoughts – part 1

I’ve been re-reading ‘The Sky Full of Stars‘ again, trying to poke holes (well, more holes than necessary) in the narrative, and thought I might blog a few explanatory notes behind my vision of the technology. Today’s subject is Nuclear Fusion as a means for providing the energy for a Starship Drive. This is nothing new. Fusion as a literary device has a long and venerable history. Nuclear Fusion, and the wealth of energy it could theoretically deliver is a goal (currently) beyond the dreams of Physicists.

Real world Nuclear Fusion ‘in the wild’ occurs when a sufficient mass of hydrogen atoms are sufficiently compressed to create the fireball that becomes a star. ‘Star nurseries‘, where this process has been observed are a well known astronomical phenomenon. It is also observable in H-Bombs, which are a relatively crude means of getting hydrogen to fuse in sufficient quantities for a multi-megaton yield explosive device.

With Fusion, the first trick seems to be to get plasma at sufficient heat, pressure and density into a single point to initiate a self sustaining reaction. The second is getting usable power out of such a reactor without melting the entire installation. Such is the potential violence from the theoretical energy release.

Creating a controlled superheated plasma has been achieved many times before, including actual incidences of fusion, but only sporadically. Part of the problem seems to be in the plasma streams themselves, which tend to ‘arc’ to earth quite readily like lightning bolts. Stopping the plasma behaving in this fashion is heavy on power input, because even with heavy duty superconductors, the amount of electricity needed for the required electromagnetic containment field outstrips any output many times over. Focussing a super powerful laser at a single pellet of hydrogen isotope has also been tried.

The only current means of achieving even partially controlled Nuclear Fusion require huge amounts of energy to spark off a reaction. This is the current reality of nuclear fusion technology. Unless some new fusion milestone has been passed recently, and skipped merrily under my radar.

In my fictional world, I have a vision of a controllable nuclear fusion reaction as a hybrid between the ‘Wiffleball’ or Polywell (WB-6, 7, 8 After the theoretical work of Robert Bussard, later Richard Nebel) and the more ‘conventional’ Tokamak based designs (ITER etc). A critical point of fusing hydrogen atoms (Forgetting the technicalities surrounding Isotopes of Hydrogen for the moment) is developed by focussing a number of plasma streams into a ‘pinch point’ at which the conditions for a fusion reaction become possible.

One of the phenomena that may make this vision possible is the ability of plasma to ‘self organise’ into helices if a sufficient charge of electric current is passed through the plasma itself (See this result from the RFP Experiment, Padova Italy in 2009). Thus reducing the propensity of the heated plasma to arc to the nearest earth. What I propose is arranging several lower power Tokamak type toroids on edge so they form a kind of ring doughnut shape with a pinch point in the centre, where all the plasma streams converge in a narrow central core; charging the plasma so it forms helices, then synchronising the helical plasma streams to create one or a series of hot spots where sustainable heat, pressure and plasma density for continuous and controllable nuclear fusion may be created.

Getting any power out, of course might prove a little tricky. Although a charged particle stream from a Fusion reaction should be enough to induce electrical current via a series of coil windings or discharge points, as well as some form of rapid heat transfer mechanism to create steam to drive an electricity generating turbine. Preventing those melting might prove an issue, but those are mere technicalities.

At the moment my conjecture is purely a literary device, rather like the use of the hypothetical realm of ‘subspace’ for faster than light travel, or ‘space warp’. Yet like so many literary devices, perhaps my version might give a real world physicist a second thought, which in turn might go some way to provide a workable solution for the dream of almost limitless energy. With Fusion, there is always the constant feeling that we are on the cusp of something great and powerful. Yet like so many other other inventions, like heavier than air powered flight and the mass mobility of the automobile, there are one or two missing pieces in the jigsaw before we have the whole picture.