NEXT Ion Propulsion : Getting About In Space

43,000 hours, Now How About a Spin Around the Moon
Credit :NASA Glenn

NASA Glenn recently announced that it has passed the 43,000 hour mark of continuous operation of its NEXT  (NASA Evolutionary Xenon Thruster) ion thruster.  Although coverage focused on the long running duration, the more relevent statistic is that NEXT represents a significant advancement over the first generation NSTAR ion thruster which powered Deep Space 1, and is currently accelerating the DAWN mission towards an encounter with the dwarf  planet Ceres, in the main asteroid belt.  The NEXT engine offers a maximum thrust of 232 millinewtons compared to 92 for NSTAR  and wider throttle range and a significantly higher specific impulse,  at 4100 seconds compared to  3100 for the previous generation engine.

Considering the remarkable accomplishments of the Dawn mission, which visited the asteroid Vesta, revealing a number of surprising discoveries before departing for Ceres, one might think that there was a long line of missions waiting to employ the NEXT technology.  Unfortunately, that is not the case, as  the combination of space science budget cuts and massive spending programs such as the Space Launch System and James Webb Space Telescope have had an effect on other, lower priority efforts such as NEXT.

Although NEXT may continue setting records on the ground,  which is useful in demonstrating the long term reliability of a deep space engine,  what is really needed before it is slated for any new science mission,  is a test run in space. This too is problematical, due to budgetary concerns and of course, high launch costs.  It bears remembering that another NASA Glenn program aimed at achieving a much higher propulsion system, HiPEP, (High Power Electric Propulsion) as part of Project Prometheus and the Jupiter Icy Moons Orbiter (JIMO) was cancelled  in 2005 specifically to make room for Project Constellation.

While it is of course never possible to fund every worthy NASA project, if there is one area where the nation continually keeps missing the mark, it is in failing to aggressively pursue those technologies or systems which have could have a leveraging effect on everything else.  The complete abandonment of reusable launch technology comes to mind, but it is hardly an isolated case.  One of the biggest limiting factors on the future of any larger electric propulsion system, such as HiPeP or VASIMR, is the lack of advancement in space nuclear power,  even though the potential benefits are obvious.  Stunningly, the U.S. has even allowed its stock of plutonium-238 pellets, such as that which powers the Mars Curiosity Rover to drop so low that only a further few missions can be contemplated anyway, which has resulted in NASA getting into a contract dispute with alternate supplier Russia, which in a story with a familiar ring to it, wants to raise prices.