90 Days to Mars?
With NASA being shut down, it seems like a particularly appropriate time to visit a recent FISO (Future in Space Operations) presentation covering an interesting proposal which will likely never be funded. The presentation, (PDF) and audio file are archived here, a University of Texas site, which is not shut down.
Recent years have seen a number of different Mars exploration architectures incorporating nuclear propulsion, including NASA’s own most recent Design Reference Architecture, DRA 5.0 Whereas the NASA scenario envisions what could be considered a fairly conventional nuclear thermal propulsion system, last week’s FISO presentation focuses on something bit more exotic; a FRC, or Field Reversed Configuration drive in which which pill sized slugs of deuterium or tritium, termed “target plasmoids” are inductively driven into the combustion chamber throat where they are instantly coated by thin strips or hoops of a lithium overlay and then collapsed by magnetic fields.
At that point, the “converging shell fragments form a fusion blanket compressing the target FRC plasmoid to fusion conditions, ” allowing the resulting plasma to react against the magnetic nozzle resulting in pulsed thrust. . With shock absorbers and a base plate at the forward end of the drive section to provide a protective cone or “shadow zone” from radiation, a conventional spacecraft designed around NASA’s own requirements could reach Mars in roughly 90 days through a trip comprised of steady acceleration followed by steady deceleration to achieve a parking orbit. Following a 30 day stay on the surface, the crew lander/ascent vehicle would rendezvous with the awaiting spacecraft, comprised of a hab module, MPCV and drive assembly, for a similarly brief sprint back to Earth.
While there are a number of issues to be worked out, and there are apparently serious questions centering around the design and operation of the magnetic nozzle, according to the presentation’s authors, the basic FRC fusion process has already been demonstrated in a lab setting. Interestingly, for the sake of simplicity, the system presented does not attempt to capture electricity from the system, using it only for propulsion, with solar panels hooked to capacitors providing the initial energy source for the magnetic fields, as well as for the spacecraft overall.