The Incredible Ions of Space Transportation

After a successful test during NASA’s Deep Space 1 mission, scientists say ion propulsion is here to stay. Formerly among the least viable propulsion systems for space travel, the pioneering efforts of scientists at the NASA Glenn Research Center and the Jet Propulsion Laboratory (JPL) have meant ion propulsion systems are a reality.

Dr. John Brophy, of JPL, discussed the past, present and future of ion propulsion systems during a session last week at the 11th annual Advanced Space Propulsion Research Workshop in Pasadena, CA.

After a development history spanning nearly 40 years and following the successful flight of Deep Space 1 in 1998-1999, ion propulsion has now entered the mainstream of propulsion options available for deep-space missions, according to an abstract written by Brophy.

‘Ion propulsion has been around for a long time,’ Brophy said. ‘The first one was tested back in 1959 at NASA Glenn (then NASA Lewis) and was found to have excellent performance.’

There were two main problems that stood in the way of successfully demonstrating the ion propulsion systems. The first problem was to demonstrate that the engines could last long enough to be useful,’ said Brophy. ‘The second problem was to figure out how to guide and navigate a spacecraft with ion propulsion, which no one had done before.’

Deep Space 1, outfitted with BMDO’s solar array and the NSTAR ion propulsion system was a success, with both working exactly as planned. New demands have followed for ion systems with increased capabilities. ‘The NSTAR system was conservative on purpose,’ said Brophy. ‘We wanted to see if it would work first. Now it is a legitimate option that is being considered for many new missions.’

Brophy explained that many of the deep-space missions that are relatively easy to perform from a propulsion standpoint, such as planetary flybys, have already been accomplished. However, future high priority mission classes, which include sample returns and outer planet orbiters, place substantially greater demands on the onboard propulsion systems.

Ion propulsion systems make missions more affordable and scientifically more attractive by enabling the use of much smaller, lower cost launch vehicles, and by reducing flight times, according to Brophy. Some proposed mission concepts considering ion propulsion include the Comet Nucleus Sampler Return (CNSR), the Saturn Ring Observer, the Titan Explorer, the Neptune Orbiter, and the Europa Lander.

The most likely candidate to use ion propulsion next will be CNSR,’ said Brophy. ‘As an example, take the European Space Agency spacecraft Rosetta, which is designed to rendezvous with comet Wirtanen in 2011. Using a conventional engine, Rosetta will take 9 years to reach the comet. The CNSR spacecraft could sieze the opportunity of an ion propulsion system to get there in only 2 ? years. Furthermore it could collect samples of the comet, and be back to Earth before the Rosetta spacecraft even arrived.’

‘At the moment, we are mostly working on improving how long the thrusters last,’ said Brophy. ‘We are hoping to double the engines’ designed operating time, which is approximately 1 year at full power.’

Propulsion experts think that improved ion engines could eventually propel space probes to nearby comets and asteroids faster than conventional engines.