Hughes' satellite operation was acquired by The Boeing Company in 2000 and is now known as Boeing Satellite Systems. Most parts of this article were written before the acquisition.
Hughes' Xenon Ion Propulsion System (XIPS, pronounced: 'zips') generates thrust by heating xenon gas and expelling the ionised particles through fine, electrified, metal grids at a speed of 30 kilometers per second.
Ion propulsion systems had been under development since the 1950s, using for instance ionised caesium or mercury vapour. The breakthrough for ion propulsion systems came in 1984 when Hughes engineers found that they could ionise the inert gas xenon, eliminating the need to deal with aggressive chemicals that tended to corrode nozzles and/or have unwanted environmental impacts.
"The heart of the XIPS is the ion thruster. Two other key units include a tank containing xenon gas and a power processor. Because ion thrusters operate at lower force levels, attitude disturbances during thruster operation are reduced, further simplifying the stationkeeping task. A typical satellite will use up to four XIPS thrusters (two primary, two redundant) for stationkeeping, all connected to the same xenon supply. Each primary device will be switched on and off by a smart power unit that monitors and diagnoses operations automatically.
"The HS 601HP satellite uses the 13-centimeter XIPS to perform all north-south stationkeeping and spacecraft momentum control in two axes. The satellite flies four 13-centimeter xenon thrusters and two power processor units. Orbit and momentum control are accomplished through a series of two burns on each day of the stationkeeping cycle. Only two of the four thrusters are required to perform a complete mission of on-orbit maneuvers. "
(Condensed from Boeing's XIPS fact sheet)
With a XIPS system onboard, propellant mass on a satellite designed for 12 to 15 years of operation can be reduced by up to 90 percent. As a result, customers can opt to launch a satellite with reduced launch costs, or, because of the weight trade-offs possible with the XIPS system, can either extend satellite life or increase payload capabilities while holding satellite weight constant.
On the first Hughes satellites equipped with XIPS, the system was only used for North-South stationkeeping. The first Hughes satellite that fully relies on XIPS for stationkeeping is--coincidence or not--Galaxy VIII-i.
|SES||HS601HP: Astra 1H, Astra 2A, Astra 2C|
|Asiasat||HS601HP: Asiasat 4|
|DirecTV||HS601HP: DirecTV 1R, DirecTV 4S|
|Loral||HS601HP: Orion 3|
|XM Satellite Radio||Hughes GEM: XM-1, XM-2, XM-3|
|Telesat Canada||Hughes GEM: Anik F2|
|Spaceway||Hughes GEM [three satellites]|
|Satmex||HS601HP: Satmex 5|