Go to Mars in 39 days

Standing in the way of a manned mission to Mars is the journey time and funding. The radical Vasimr engine could reduce the journey from 9months to 39days and Nasa's recent course change might have freed up the money to help pay for it.

One of the biggest obstacles facing any manned Mars mission, aside from the financial one, is the sheer length of time it takes to get there. Using conventional rockets, the best journey time we can hope to achieve is six to seven months, during which time your Martian pioneers would lose a bit of their edge. Without gravity, the cardiovascular system weakens and the vertebrae will pull apart. Unused muscles will atrophy and bones will lose so much calcium they become fragile and prone to fracture. That’s not to mention the psychological effects of months of incarceration and isolation. In short, by the time your hero touches down, he will be more Supergran than Superman.

What is needed is a radical new, superfast propulsion method that will give your astronaut a chance to step down from his capsule and not fall down from it. Enter former seven-time astronaut and plasma physicist Franklin Chang-Diaz.

He and his colleagues at the Ad Astra Rocket Company are busy putting the finishing to touches to an engine that will transform a seven-month Martian odyssey into a 39-day Martian jaunt. The wonderfully named Variable Specific Impulse Magnetoplasma Rocket, or Vasimr, uses super-heated plasma to reach speeds of more than 193,000kph (the best conventional rockets top out at 64,000kph) while consuming only a fraction of the fuel.

Aside from the long journey times, the trouble with conventional rockets is they are terribly inefficient, meaning that the bulk of any Mars craft would, by necessity, have to be given over to fuel – leaving very little room for cargo or astronauts. The efficiency of a rocket engine is measured in terms of specific impulse (a kind of miles per gallon), which is a measure of how many seconds of thrust a rocket can get from a unit of fuel. A good chemical rocket has a specific impulse of about 450 seconds – it gets one pound of thrust from one pound of fuel for 450 seconds. Vasimr, however, can achieve a specific impulse of 30,000 seconds. This means it can go a long, long way on a relatively small amount of fuel.

Vasimr works by using radio waves and something called a magnetic mirror to heat hydrogen gas so that it forms a plasma that is similar, in property and temperature, to the material that makes up the Sun.
 

The superheated plasma is then ex pelled from the rocket’s exhaust to provide thrust. In rocketry, the higher the temperature of its exhaust, then the better it is.

A space shuttle exhaust gets to a few thousands degrees celsius but Vasimr reaches temperatures in excess of 1million˚C.Another advantage to Vasimr is, since hydrogen is the most abundant element in the Universe, a Vasimr-powered craft will need to carry only enough fuel to reach its destination, such as Mars, and then refuel on arrival for the return journey. Also, hydrogen is the best radiation shield known, so the fuel could be used to protect astronauts from potentially harmful radiation exposure. Vasimr is more than just a sci-fi fantasy, though. The engine has been tested at full power in the lab and in 2012 it will be tested on the International Space Station.

Why man+Mars = Nuclear power

In space, without power, you die. The International Space Station consumes 75kW of power, most of which is used to keep astronauts alive, which it derives from its 2,500sq m solar array.

Power estimates for a Mars colony range from 20kW to 60kW, which sounds do-able until you realise that, thanks to the weakness of the Sun’s rays at Mars, a solar array supplying just ten kilowatts would need to be about 68,000sq m. Solar panels of that magnitude are simply impractical. That’s not taking into account the 200mW of power your Vasimr-powered craft will need to get you to Mars in 39 days. The only practical solution to that sort of power requirement is a nuclear reactor (current Mars rovers use a sort of nuclear battery already to supplement their solar arrays) both onboard your Martian craft and on the planet’s surface.

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