Hi All

A quick little essay from Gerald Nordley...

Going to Mars?

...which discusses the trade-off between due haste and ideal trajectories. If we use chemical rockets it's actually cheaper in propellant to get to Mars in 108 days than a minimum energy Hohmann of 257 days. The extra supplies and mass-protection against solar storms (plus the extra fuel they need to be pushed into a transfer orbit) make a minimum energy orbit less economical than a 'sprint' - so long as we aerobrake at the other end.

Most Mars planning assumes 2-year free return orbits taking ~ 150 days (130 to 180 days, depending on Mars' position on its orbit) - no one could seriously advocate manned missions crawling along a 9 month Hohmann transfer. Only under-powered ion-drive advocates ask for longer trip times - like Stuhlinger's slow-crawl ion-drive fleet for Disney's Mars and Beyond" - which could well be superseded if fusion power gets a leg-up. Robert Bussard, of interstellar ramjet fame, believes his Energy/Matter Conversion Corporation (EMC2) has built a working, light-weight fusion reactor - the first models will supply 100 MW with a mass of just 25 tons (4 kWe/kg.) A souped-up VASIMR powered by a Bussard fusor can cross to Mars in just 39 days.

Alternatively a bank of fusors could power a 300 MW mag-beam and push cargo shuttles to Mars in just 35 days.

Adam