Electric Rocket

New satellite will use electric rockets known as ion thrusters.

In March 2012, the Boeing Company announced a revolutionary change in the way communications satellites would be built and operated. The company unveiled a $400 million deal to build the first all-electric geosynchronous communications satellite.

Boeing's new satellite will use electric rockets known as ion thrusters to maneuver into an orbit 22,236 miles (35,786 kilometers) high and to keep itself in its orbital slot. This will mark the first use of this promising electric rocket system in a commercial spacecraft.

Electric rocket Ion Thruster

A xenon ion engine being tested at NASA's Jet Propulsion Laboratory showing the faint blue glow of charged atoms being emitted from the engine.

Current communications satellites use large amounts of chemical propulsion, which results in very large spacecraft due to the need for fuel tanks, piping, and engines. Boeing's comsat will be maneuvered by small, light-weight xenon-fueled thrusters, which will greatly reduce the size of the vehicle and its launch cost. A satellite builder could also keep the size of the spacecraft the same while devoting more space aboard it to transponders that generate revenue.

An electric rocket creates thrust by accelerating beams of ions using either electromagnetic or electrostatic force. Ion rockets are highly efficient although the amount of thrust they produce is very small compared to the amount produced by chemical propulsion. This low thrust makes ion thrusters unsuited for launching spacecraft into orbit, but they are ideal for in-space propulsion applications.

The main trade-off with using electric rockets with geosynchronous satellites is the amount of time it takes to get to its final orbit. Ion propulsion uses slow pulses, meaning it could take up to six months for a satellite to reach its orbital slot instead of weeks with chemical propulsion. This is time that the spacecraft is not generating income for its owners. The long transit time through the Van Allen Belts may require additional shielding to protect the electronics from radiation.

The origins of electric rockets go back to the early days of rocket experimentation. Robert Goddard mentioned the possibility in a notebook on Sept. 6, 1906. A decade later, he conducted the first experiments with ion propulsion at Clark University. Hermann Oberth further elaborated on the idea in his book, "Ways to Spaceflight," in 1923.

Despite the enormous potential of electric rockets, it took many decades to develop them for use on spacecraft. The Soviet Union used a form of electric rocket, known as the Hall effect thruster, to stabilize satellites beginning in 1972. In 1992, the United States began to use Soviet designs in its thrusters.

Electric rockets could be quite useful in getting humans beyond Earth orbit. For example, they could efficiently transport fuel to planned fuel depots in Earth and lunar orbit much more efficiently than a chemically powered rocket. They could also make regular trips between the Earth and the moon, asteroids, and Mars.

Ion thrusters

 

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