Rockets that use charged particles to propel fast
missions to Mars are one step closer, now a small-scale prototype
has been demonstrated at full power.
The ion engine may be used to maintain the orbit of the
International Space Station within the next five years, and could
lay the groundwork for rockets that could one day travel to Mars in
about a month.
Since 2005, the Ad Astra Rocket Company of Webster, Texas, has
been working to perfect a type of engine it calls VASIMR (Variable
Specific Impulse Magnetoplasma Rocket).
It uses radio waves to heat argon gas, turning it into a hot
plasma – a state of matter in which electrons are no longer bound
to atomic nuclei. Magnetic fields then squirt the superheated
plasma out the back of the engine, producing thrust in the opposite
direction.
It shoots the propellant out at much higher velocity than
conventional engines, resulting in far more acceleration per
kilogram of fuel consumed.
In the near term, the company hopes to use a 200-kilowatt VASIMR
engine to provide periodic boosts to the orbit of the International
Space Station (ISS), which gradually drops in altitude due to
atmospheric drag.
Now, the company has run such an engine at full power for the
first time. On Wednesday, it ran its VX-200 engine at 201 kilowatts
in a vacuum chamber in Houston, passing the 200-kilowatt mark for
the first time.
NASA deal
"It's the most powerful plasma rocket in the world right now,"
says Franklin Chang-Diaz, the former NASA astronaut who heads the
company.
The nearest thing to a competitor is NASA's 50-kilowatt Hall
thruster, an engine based on accelerating electrically charged
atoms, or ions, that the agency stopped developing in 2005 due to
budget cuts.
Ad Astra has signed an agreement with NASA to test a
200-kilowatt VASIMR engine on the ISS in 2013. The company is
talking to two space firms, SpaceX and Orbital Sciences, about the
possibility of delivering the engine to the ISS on one of their
launch vehicles.
If the tests go well, the company hopes to offer regular boosts
to the space station's orbit on a commercial basis starting the
following year.
More efficient
Previously, spacecraft – including Russian and European cargo
ships – have provided these boosts by firing their engines while
docked with the space station.
But with conventional thrusters, the boosts consume 7.5 tonnes
of propellant each year. VASIMR could do the same job with just 0.3
tonnes of argon per year, Chang-Diaz says. Since it is expensive to
launch fuel into orbit, that could save millions of dollars per
year, he says.
The revenue generated by the ISS boosts would help the company
"make the technology better and enable human missions to Mars",
Chang-Diaz told New Scientist.
Less radiation
A 10- to 20-megawatt class VASIMR engine could propel human
missions to Mars in as little as 39 days, he says, compared to the
six months or more required with conventional rockets.
The shorter trip would reduce astronaut exposure to space
radiation, which could otherwise be a major barrier for human
missions to Mars, especially given signs that radiation levels may
be particularly high in coming decades.
Propelling fast trips to Mars may one day be very profitable for
the company, says Chang-Diaz. "But for now, profit is not at Mars,
it's closer to Earth," he says.