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Falcon 9’s Second Stage Restart was Just as Important as Sticking the Landing

Falcon 9's second-stage Merlin engine, shown above during its pre-deployment burn, demonstrated its ability to restart after all 11 Orbcomm satellites were successfully deployed. Credit: SpaceX webcast screen grab

​PARIS — SpaceX’s successful deployment Dec. 21 of 11 Orbcomm machine-to-machine messaging satellites and the apparently clean return and landing of the upgraded Falcon 9 rocket’s first stage also validated the ability of the redesigned second-stage propulsion system to restart in orbit after a coast phase, SpaceX said.

​The mission’s first two goals – deploying Orbcomm into low Earth orbit and especially the on-target return of the first stage to its landing zone – were the focus of most of the attention during and after the launch.

​At one point in the SpaceX webcast of the launch the moderator had to remind viewers looking at SpaceX employees whooping and hugging after the landing that the mission’s main objective, after all, was to deploy the Orbcomm fleet.

​But it is the second stage’s performance that will position SpaceX to conduct commercial operations the way it has long intended. SpaceX said the second stage engine performed the full re-ignition and burn sequence needed for geostationary satellites.

​Hawthorne, California-based SpaceX said its new-version Falcon 9 is 33-percent more powerful than the Falcon 9 v1.1 version it replaces. Only one more v1.1 variant is being planned, for the Jan. 17 launch of the U.S.-European Jason-3 ocean altimetry satellite, from Vandenberg Air Force Base, California.

​After that, all future Falcon 9 rockets will be of the upgraded version, whose main goal is to permit SpaceX to recover the first stage even when launching heavy telecommunications satellites into geostationary transfer orbit.

​Despite the growing popularity of smaller satellites and previously unheard-of orbital architectures, placing telecommunications spacecraft into geostationary orbit remains the biggest commercial space market. This is where the money is made, and where SpaceX wants to be active as it pursues its long-term goal of sending humans to Mars.

​The Falcon 9 v1.1 rocket had already proved its ability to place telecommunications satellites into geostationary transfer orbit. But the energy needed to do so meant the rocket could not retain the fuel needed to return itself to a landing point.

​The Falcon 9 upgrade now makes that possible.

​Until October, SpaceX’s next commercial customer, telecommunications fleet operator SES of Luxembourg, had been set to place its 5,300-kilogram SES-9 satellite aboard the inaugural flight of the Falcon 9 upgrade.

​SpaceX ultimately decided to test the upper stage propulsion system’s performance and restart ability on a mission that did not need either: The 172-kilogram Orbcomm satellites were dropped off at around 630 kilometers in altitude.

​SpaceX said that after dropping off the Orbcomm satellites, the upper stage performed the required re-ignition and coast phase that will be needed to place telecommunications satellites into their transfer orbits.

​SES on Dec. 22 said all the information it had from the launch reinforced its plans to launch SES-9 by late January aboard the upgraded Falcon 9. SES, which has four other launches contracted with SpaceX after SES-9, has stated it is willing to be the first commercial customer to launch with a used Falcon 9 first stage.

​Even before the Orbcomm launch, SES officials had informed their insurance underwriters that they were willing to be the inaugural customer of the Falcon 9 upgrade even if it meant doing without a launch insurance policy.

​European launch officials have been eyeing the Falcon 9 upgrade’s development with trepidation, having agreed 12 months ago to invest some $9 billion into their own Ariane 5 and future Ariane 6 expendable rockets over 10 years.

​In recent weeks European officials – whose Ariane 5 rocket depends heavily on the commercial launch market — have reiterated that they always assumed SpaceX would succeed in a clean return and landing of the Falcon 9 first stage.

​But that’s not the hardest part, they said, pointing to the difficulties of refurbishing used stages at a rhythm that permits SpaceX to maintain a launch cadence high enough to bring down per-unit costs even as its rocket production facility loses a part of its own economy of scale by virtue of the fact of making fewer first stages.

SpaceNews.com

Source: Space News

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Falcon 9’s Second Stage Restart was Just as Important as Sticking the Landing

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