Madsen Pirie

BBC News regularly featured the story that any spacefarers headed for Mars will face radiation that is over the acceptability limits NASA tries to keep its astronauts within.  The robot Curiosity on its long voyage to the red planet monitored radiation from two principal sources.  One was that emitted by the sun, and the other was the stream of much higher energy particles coming in from deep space that are the legacy of cosmic collisions and supernovae.  The latter are much more damaging, and are the source of the light blips that affect the eyes of astronauts even when closed.  It is the long voyage that builds up the unacceptable levels.  Once on Mars the atmosphere provides some protection.

Shielding has been suggested, but it would need to be very thick to afford appreciable protection, and would greatly increase the mass that had to be accelerated.  The other is a shorter journey time, cutting six months down to a few weeks, and people have suggested waiting for higher technology propulsion such as ion drives and plasma engines.  A simpler route to a shorter trip might be to burn more fuel with conventional engines, but that in turn would raise the vehicle’s mass.

The solution might be modular construction of a craft in low Earth orbit, with sections being lifted off separately and assembled in space before departure towards Mars.  This would mean that extra fuel for a faster velocity could be achieved with additional launches.  It is rather surprising that none of the outline plans call for material to be sent to Mars ahead of the astronauts.  The technology that landed Curiosity could send ahead supplies and equipment, and even the ascent vehicle for Mars lift-off, and the return craft waiting in Mars orbit to bring the crew home.  Then the outward voyage could be a high-velocity one in a relatively light craft whose function was simply to get the crew there quickly before they were exposed to damagingly high levels of radiation.

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