Boeing Wins U.S. Patent for Stacking Electric Satellites on Rocket
PARIS — Boeing Space and Intelligence has received a U.S. patent on a process that places one electric-powered satellite atop another under a rocket’s fairing, without the need for a satellite support structure.
Patent No. 8,915,472 B2, shown here, was issued Dec. 23.
In it, Boeing describes how it will take advantage of the substantial weight savings offered by all-electric satellites — and those using a chemical/electric mix — by placing two of them on a rocket that otherwise could carry only one satellite at a time.
The first two of Boeing’s all-electric 702SP satellites are scheduled for launch in late February aboard a SpaceX Falcon 9 rocket. A second pair owned by the same two satellite fleet operators — Eutelsat of Paris and ABS of Bermuda — are scheduled to launch on a Falcon 9 late this year.
Launch provider Arianespace of Evry, France, almost always launches two satellites at a time on its heavy-lift Ariane 5 rocket. But these launches employ a support structure over the satellite in lower position to support the weight of the upper-position satellite. The support structure weighs around 700 kilograms.
The Ariane 5 also launched four Cluster science satellites for the European Space Agency under the same fairing, with two spacecraft on top of each other and the other two separated by a support structure. These did not use all-electric propulsion, however — which appears to be an important element in Boeing’s patent.
Russia’s Proton heavy-lift rocket has deployed two satellites at a time with no support structure, but Boeing said its invention differs from that insofar as its two satellites are interchangeable between the top and bottom positions.
“The primary difference is that while the Proton may have stacked, the satellites were not both all-electric propulsion system or hybrid-system satellites,” Boeing said in a Jan. 12 statement explaining its patent. “It’s not clear that the Russians patented what they did, but as we know it, theirs was not all-electric propulsion or a hybrid, in which case Boeing has the original patent.”
The Boeing patent is not limited to satellites launched in pairs, although that is the configuration it is using for its first commercial spacecraft.
“In the Russian system, the lower vehicle is a workhorse bus and the upper is a liquid propulsion satellite,” Boeing said. “Their configuration will not support two high-power satellites — more than 7.5 kilowatts each — of nearly identical configurations. The Boeing design has the outer module, which is identical, and different internal cores, which for all intents and purposes makes them interchangeable from upper to lower position in the stack. The Russian configuration cannot switch the payload modules from upper to lower.”
The ability to launch two satellites at a time on a single Falcon 9 rocket was key to the Boeing contract award, signed with ABS and Satmex of Mexico. Satmex has been purchased by Eutelsat. ABS and Eutelsat have an option for four more Boeing spacecraft under the contract, signed in March 2012.