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Falcon 9 Performance: Mid-size GEO?

Last month commercial fleet operator SES said it plans to launch the 5.3-tonne SES-10 communications satellite on a SpaceX Falcon 9 rocket in 2016.

The Luxembourg-based company – the world's second largest fleet operator by revenue – said SES-10 would be based on the Eurostar 3000 bus, be equipped with 50 Ku-band transponders, generate 13kw of power and operate from an orbital slot at 67 deg. west.

Satellite manufacturer Airbus Defense and Space said the 5,300-kg SES-10 is expected to have a nominal in-orbit life of 15 years.

The problem, however, is that SpaceX caps the advertised GTO performance of Falcon 9 from Cape Canaveral AFS, Fla., at 4,850 kg.

SpaceX founder, CEO and Chief Designer Elon Musk says while Falcon 9 is capable of lofting more mass to orbit than advertised, he says the current performance from the Cape is closer to 3,500 kg.

“The tricky thing is that we have to compete with people like Arianespace,” Musk said in a Feb. 20 interview, referring to the European launch services provider that manages heavy-lift Ariane 5 missions from Kourou, French Guiana, near the equator.

“So for Falcon 9 to compete with them, we have to do supersynchronous orbit, go to like 80,000 km or more, instead of 36,000 km for GTO,” Musk said. “We've also got to do a partial plane change, and that reduces our payload. So our current payload capacity is more like 3.5 tonnes (3,500 kg) to 1,500 meters per second delta-v.”

Musk said while the Falcon 9 is able to compete in the mid-sized geosynchronous satellite range, it is “not quite at the 5-ton (5,000-kg) level when you consider plane-change maneuvers and higher altitude.”

With the Falcon Heavy still in development, but expected to debut next year, he said the Falcon 9 would will be used to launch less massive satellites. But given SpaceX's plan to gradually introduce fully and rapidly reusable first-stage rocket cores, both Falcon 9 and Falcon Heavy will see weight penalties affect performance.

In the meantime, Musk said SpaceX is not planning any major revisions to the Falcon 9, though minor changes are expected to yield improved performance in the near-term.

“For example, we'll be chilling the propellant to densify it, to get more propellant load for the given volume,” he said, adding that other minor mass improvements would be aided by the removal of sensors and associated wiring used to gather data on the new rocket's early flights.

“Where I basically see this netting out is Falcon 9 will do satellites up to roughly 3.5 tonnes, with full reusability of the boost stage, and Falcon Heavy will do satellites up to 7 tonnes with full reusability of the all three boost stages,” he said, referring to the three Falcon 9 booster cores that will comprise the Falcon Heavy's first stage. He also said Falcon Heavy could double its payload performance to GTO “if, for example, we went expendable on the center core.”

SpaceX President Gwynne Shotwell says in general, heavier satellites will require more propellant to reach operational orbit.

“It really depends on how much the satellite is willing to do,” she said in a Feb. 27 interview. “So the more fuel you use, the trade there is mission life. Folks like to go 20 years, a minimum is generally 11 or 12, so that's where your trade ends up.”

SES did not respond to questions about the expected operational life of SES-10.

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