NEW ORLEANS — On the eve of the first launch of a reused Dragon capsule on a Falcon 9 with a reused first stage, both NASA and SpaceX said they were comfortable with the level of risk involved with the mission.
The Falcon 9 was scheduled to lift off at 11:46 a.m. Eastern Dec. 12 from Space Launch Complex 40 at Cape Canaveral Air Force Station in Florida, the first launch from that pad since it was repaired following a September 2016 pad explosion.
SpaceX announced late Dec. 11 that was delaying the launch a day “to allow for additional time for pre-launch ground systems checks.” The launch is now scheduled for approximately 11:24 a.m. Eastern. Forecasts projected an 80 percent chance of acceptable weather for the launch, with winds the primary concern.
The Dragon is carrying 2,205 kilograms of cargo to the station, ranging from crew supplies and hardware to a wide range of science experiments to be carried out inside the station as well as mounted on the station’s exterior.
While the mission will be the 13th in SpaceX’s Commercial Resupply Services (CRS) contract with NASA, this flight does mark a first: SpaceX will use a previously-flown first stage on this mission, which first launched another Dragon spacecraft to the space station six months earlier.
“We’re very comfortable that the risk posture on this vehicle is not significantly greater than a new booster,” Kirk Shireman, NASA ISS program manager, said at a pre-launch press conference Dec. 11.
Some risks, he said, are actually less with a reflown booster, while some are a little greater. He didn’t elaborate on specific issues that had higher or lower risks. “The net result is about equivalent risk,” he said.
Discussions about using a reflown booster on a CRS mission started nearly a year ago, said Jessica Jensen, director of Dragon mission management at SpaceX. “We’ve been working with NASA since January of this year on the process for ensuring that a flight-proven booster is of equivalent risk to a new booster,” she said, with technical meetings between NASA and SpaceX on various aspects of booster reuse.
Shireman, as other NASA officials have previously indicated, said that the agency has only approved this single use of a previously-flown booster, and one that carried out a similarly “benign” mission that did not subject the stage to as much stress as launches of satellites to geostationary orbit. NASA finally approved the use of a reflown booster only about two weeks ago, after SpaceX completed its readiness reviews.
While NASA is still getting comfortable with reused boosters, it is more accepting of reflown Dragon spacecraft. This flight will use a Dragon capsule that first flew on SpaceX’s sixth CRS mission in April 2015. It marks the second CRS mission to use a reflown capsule.
“For the remainder of the current CRS contract, we are planning to continue to just use refurbished Dragons,” Jensen said. “We have enough in our fleet.” She later said there are about seven Dragon spacecraft available for reuse.
After this launch, SpaceX has one more mission planned for this year, launching 10 Iridium Next satellites Dec. 22 on a Falcon 9 from Vandenberg Air Force Base in California, a mission that will also use a previously-flown booster. Jensen said that will be followed in early January by the classified “Zuma” mission, which was to launch from Florida in November but was postponed to study a potential payload fairing issue during tests for another mission.
SpaceX is also preparing for the first launch of the Falcon Heavy. A static-fire test of the rocket from Launch Complex 39A is still scheduled before the end of the year, she said. “The launch will then happen about a few weeks after that,” she said.
That launch complex, which had been hosting all SpaceX launches this year while Space Launch Complex 40 is being repaired, will now host Falcon Heavy and commercial crew missions. SpaceX is scheduled to perform two commercial crew test flights, one without a crew and one with NASA astronauts on board, in April and August, respectively.
Shireman, though, cautioned those test flights, as well as two scheduled by Boeing for 2018, may encounter additional delays. “They’ll fly when they’re ready, and while we want them to be ready as soon as possible, we also don’t want them to fly until they are ready,” he said.
He added there are no discussions with Russia about buying additional Soyuz seats. A deal with Boeing signed earlier this year provided NASA with two additional near-term Soyuz seats, and an option for three more in first half of 2019. NASA exercised that option in October. “We have seats to fly U.S. astronauts on Soyuz vehicles through the first half of 2019,” he said.
Shireman said there is a “whole spectrum of options” to get additional schedule margin of commercial crew vehicles are not ready by then. “But our confidence in the launch dates for SpaceX and for Boeing in their commercial crew vehicles is increasing as well,” he said.