Testing on the space station
On December 10, 2008, Ad Astra Company signed an agreement with NASA to arrange the placement and testing of a flight version of the VASIMR, the VF-200, on the International Space Station (ISS). Its launch is anticipated to be in 2011 or 2012, though it may be later. Since the available power from the ISS is less than 200 kW, the ISS VASIMR will include a trickle-charged battery system allowing for 15 min pulses of thrust.
The ISS orbits at a relatively low altitude, so as to make it easily accessible from Earth. The downside of this, however, is that the ISS experiences fairly high levels of atmospheric drag, making periodic boosts of altitude necessary. Currently, altitude reboosting by chemical rockets fulfills this requirement. If the tests of VASIMR reboosting of the ISS goes according to plan, the increase in specific impulse could mean that the cost of fuel for altitude reboosting will be one-twentieth of the current $210 million annual cost. Hydrogen is generated by the ISS as a by-product, which is currently vented into space.
The Universe : Secret of the space-probe