NASA recently funded a University of Michigan design for spacecraft thrusters as part of its Next Space Technologies for Exploration Partnerships (NextSTEP). The NextSTEP program encompasses various projects, all aimed at bringing humans closer to manned missions to Mars.

The project at the University is led by Aerospace Engineering Prof. Alec Gallimore, who was named the next Engineering dean Thursday.

His design, called the X3, is the thruster component of a larger propulsion system called the XR-100, which is the project of major aerospace engineering firm Aerojet Rocketdyne. NASA awarded $6.5 million to Aerojet Rocketdyne for the XR-100, $1 million of which has been given for work on the X3 thruster taking place at the University. Prof. Gallimore said the University is a partner and subcontractor for the firm.

The X3, which is based on a series of thrusters developed at NASA, works by ejecting plasma at extremely high speeds out of the rear of a device, providing forward thrust. Plasma is ejected at speeds of up to 30,000 meters per second, which is equal to about 65,000 miles per hour.

Scott Hall, a Ph.D. candidate in the Department of Aerospace Engineering, is the lead graduate student on the project. He said while the NextSTEP funding has only occurred in the past week, development of the design has been underway for some time.

“The funding through NextSTEP has been active for about a week, and the proposal for that was originally made about a year ago,” he said. “However, the X3’s development started somewhere around 2010 and the thruster has been assembled and operational since September 2013.”

The X3 is competing against two other designs for use in the XR-100 system. According to Hall, this design is the only one of the three that has been created by members of a university.

The X3 design is also further ahead of competing designs in terms of development, Gallimore wrote in an email.

“It is more mature than any of the others, which means the risk of developing it is lower,” he wrote. “Also, it appears to be lighter and more efficient (in terms of converting spacecraft power to thrust) than the other systems.”

Hall also noted that the X3 design has a proven track record.

“The three different concepts are all electric propulsion, but they are all very different types,” he said. “The thruster we have developed here has a very proven track record: It is based on a series of thrusters developed at NASA.”

According to Gallimore, the short-term goal is to bring the design to a level of readiness within three years.

“The goal is to bring the technology up to a readiness level in three years, that a follow-on contract could get the system ready for use in space a few years after NextSTEP is done,” he wrote.

Even if the design is ready in three years’ however, it will be longer until the X3 design can be tested or put to use in space. Gallimore said he believes one of the limitations will not be the U-M thruster, but rather the spacecrafts that would use it.

“The power system needed to drive this thruster is years away from development, so while the XR100 system could be ready by 2020, I doubt we will have a spacecraft large enough or powerful enough by then to use it,” he said.

Hall agreed and said it will take some time for the design to be put to use.

“Realistically, it would probably be 10 years or so until something based on this work was operated in space,” he said. “But our project is ambitious and if successful will get us much closer than we are right now to being ready to fly for the first time.”

Hall added that there are several other potential uses of this technology beyond just propelling humans to Mars.

“The X3 was developed not only with Mars missions in mind, but also a range of other applications,” he said. “The thruster was designed to be run down to as low as 1 kW and up to 200 kW, so it has a huge range of ‘throttle ability,’ as we say. Something like it could be used to maneuver heavy satellites in orbit around Earth, for cargo tugs to places like Mars, to crewed mission to places like Mars, and as a way to get a very large probe to deep space much quicker than by traditional means.”


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