New Radiofrequency Thrusters May Yield Big Savings

By | November 10, 2003 | Feature

PARIS–The planned deployment of radiofrequency ion thrusters (RIT) in satellites later this decade could produce savings in the range of 10 to 20 million euros ($11.5 million to $23.0 million) for each mission, compared to traditional chemical propulsion, said Thomas Froehlich, the project manager of electric propulsion at EADS Space Transportation, a unit of the European Aeronautic Defence and Space Co. (EADS).

The intent is to hold the critical design review in 2004 and to finalize qualification testing of the ion thrusters through prototype flights by 2007, Froehlich told SATELLITE NEWS during a Nov. 5 interview. Once the technology is proven, EADS officials envision working with satellite manufacturers worldwide to develop lighter and less expensive satellites that could be launched for a fraction of the current price, he explained. EADS officials are convinced the technology is going to be a breakthrough.

Testing of the ion propulsion technology already has reached 47,000 hours, including 7,000 hours of in-orbit service with the still-functioning Artemis satellite, Froehlich said.

The ion thrusters would need only one-tenth or less of the propellant mass now required with traditional chemical propellant. EADS is interested in making the technology available to satellite builders worldwide, in addition to providing it to Astrium, its satellite-manufacturing sister company.

Prospective customers are wary about using new propulsion systems, in light of in-orbit problems incurred by Boeing’s [NYSE: BA] use of a Xexon ion propulsion system, but EADS uses a radio-frequency ionization approach providing a few inherent reliability advantages rather than Boeing’s Kaufman technique that features electron bombardment. EADS already has successfully flight-tested its ion propulsion system, and is the only European company to have accomplished that feat.

A key technical difference between the ion propulsion thrusters under development by EADS Space Transportation and the traditional chemical propulsion is that EADS uses an RF field on a discharge chamber to accelerate electrons. The collision between electrons and neutral Xenon atoms will ionize the Xenon.

The new, high-thrust RIT-22 system designed by EADS uses an electrostatic, high-voltage field of 1,500 to 2,000 volts to accelerate ions and expel them from the thrusters. That procedure creates thrust of 150 milli-Newtons to 250 milli-Newtons at very high impulse values.

The specific impulse is between 4,000 to 6,000 seconds. That performance is 10 to 15 times higher than any traditional chemical propulsion could achieve, Froehlich said.

Certain scientific missions that are not feasible now with chemical propulsion due to the excessive amount of propellant required could be fulfilled with the RITA ion propulsion system.

The biggest challenge ahead may be to convince the buyers of satellites that the technology is proven sufficiently to use in high-stakes missions. Insurers also may have concerns that will enter into the decision-making process of operators.

“Efforts to develop reliable electric propulsion thrusters with efficiencies higher than their chemical versions have now been underway for close to 30 years now,” said D.K. Sachdev, president of the Vienna, Va.-based SpaceTel Consultancy. “The potential payoffs are in terms of smaller spacecraft and lower launch costs. There is also a well-recognized potential for deep-space applications.”

However, a variety of different approaches have been “exhaustively tested” on the ground, Sachdev said. Unfortunately, the in-orbit reliability has not been very successful so far.

The European Space Agency and EADS have led the radiofrequency approach for quite a number of years, Sachdev said.

“The anomaly in the Artemis launch gave an ample opportunity to demonstrate the potential of this technology for orbit-raising. However, much longer in-orbit experience may be necessary than the 7,000 hours accumulated so far to convince commercial operators to rely exclusively on this technology,” Sachdev said. –Paul Dykewicz

(Thomas Froehlich, EADS Space Transportation, 49 (0) 89 607-2 91 67; D.K. Sachdev, SpaceTel Consultancy, 703/757-5880)

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