Production of satellite with first all-electric propulsion system advances

  • 15-Jul-2014 01:29 EDT
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Because of the lower mass enabled by all-electric propulsion, two satellites can be launched on a single launch vehicle. Depicted here is the all-electric satellite for Boeing customer ABS. (Boeing)

Boeing is “running on schedule” as it continues to achieve production milestones for the first of its all-electric-propulsion 702SP (small platform) satellites.

The company says the 702SP will be the world’s first all-electric-propulsion satellite when it is launched later this year or early next.

Earlier this year, Boeing announced that it had completed static qualification testing, verification, and assembly of the primary structures for 702SP inaugural customers ABS and Eutelsat, with the spacecraft scheduled to be launched as a pair in a stacked configuration. The initial contract was signed in 2012 between Boeing and Satmex. Eutelsat acquired Satmex in January 2014.

Joanna E. Climer, Communications Specialist, Boeing Space & Intelligence Systems, confirmed to Aerospace Engineering on July 10 that the program is on track.

"We will be first to launch a commercial all-electric satellite, providing customers new flexibility, and next-generation technology for increased performance," Craig Cooning, Vice President and General Manager of Boeing Space & Intelligence Systems, said in a March 24 press release. "The all-electric propulsion design gives customers more affordable launch options and the ability to nearly double payload capacity."

Boeing is building two pairs of 702SP satellites under a joint four-satellite agreement with ABS and Eutelsat. Production on the 702SP satellites began in 2013, after the spacecraft passed its critical design review in May of that year.

The Boeing 702SP couples proven technology from Boeing’s previous designs with next-generation technology and processes, resulting in an affordable, lightweight alternative design to meet customer needs, according to Climer. She explained to Aerospace Engineering that the 702SP’s all-electric propulsion system relies exclusively on xenon as the propellant: “This propellant is an inert and non-hazardous element. Previous hybrid designs used a combination of xenon gas and other chemical propellants, such as hydrazine and nitrogen tetroxide. In the hybrid design, these other chemical propellants were used for both orbit-raising and positioning, while xenon gas was only used for positioning…The all-electric propulsion 702SP now uses xenon as the only propellant.”

Most satellites use something similar to combustion for propulsion, but since there is no oxygen in space they need to carry both the fuel and oxygen with them, “which is heavy,” Climer continued. “With the xenon ion propulsion system (XIPS) engine in the 702SP, instead of using fuel and an oxidizer, you have a gas—in this case xenon. The xenon gas is charged, electrically ionized, and travels at a high velocity through the XIPS engine to create thrust, propelling the satellite forward. This makes the 702SP more efficient and lighter in weight. Weight is a main factor in launch costs.”

The 702SP is an evolution of the Boeing 702 satellite. Its lightweight design accommodates launch on most commercial launch systems, including Falcon 9, Ariane 5, Sea Launch, Proton, Soyuz, Atlas V, and Delta IV.

Because of lower mass owing to the lighter-weight components of a xenon-ion propulsion system compared to that of a conventional one requiring liquid fuel, two satellites can be launched on a single launch vehicle, resulting in a cost savings of up to 20% when compared with existing launch options, according to Boeing.

A typical spacecraft will carry between 1800 and 2800 kg of liquid bi-propellant to achieve orbit-raising and on-station position / orbit slot change. An all-electric XIPS system only requires around 300 kg of xenon gas to do the same, said Climer.

The disadvantage of all-electric propulsion is that it generates less thrust than conventional propulsion and thus takes longer to move and position the satellite. Climer said a typical XIPS thruster provides 0.165 N thrust. When fired in pairs, this equates to 0.33 N. Typical chemical thrusters are 10 N and 22 N (for control jets), and up to 440 N LATs (liquid apogee thrusters).

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