SpaceX’s oldest Crew Dragon spacecraft launched Sunday night on its fifth mission to the International Space Station, and engineers are crunching data to see if the fleet of Dragons can safely fly as many as 15 times.
It has been five years since SpaceX launched the first Crew Dragon spacecraft on an unpiloted test flight to the space station, and nearly four years since SpaceX’s first astronaut mission took off in May 2020. Since then, SpaceX has put its clan of Dragons to use ferrying astronauts and cargo to and from low-Earth orbit.
Now, it’s already time to talk about extending the life of the Dragon spaceships. SpaceX and NASA, which shared the cost of developing the Crew Dragon, initially certified each capsule for five flights. Crew Dragon Endeavour, the first in the Dragon fleet to carry astronauts, is now flying for the fifth time.
This ship has spent 466 days in orbit, longer than any spacecraft designed to transport people to and from Earth. It will add roughly 180 days to its flight log with this mission.
Crew Dragon Endeavour lifted off from Florida aboard a Falcon 9 rocket at 10:53 pm EST Sunday (03:53 UTC Monday), following a three-day delay due to poor weather conditions across the Atlantic Ocean, where the capsule would ditch into the sea in the event of a rocket failure during the climb into orbit.
Commander Matthew Dominick, pilot Michael Barratt, mission specialist Jeanette Epps, and Russian cosmonaut Alexander Grebenkin put on their SpaceX pressure suits and strapped into their seats inside Crew Dragon Endeavour Sunday evening at NASA’s Kennedy Space Center. SpaceX loaded liquid propellants into the rocket, while ground teams spent the final hour of the countdown evaluating a small crack discovered on Dragon’s side hatch seal. Managers ultimately cleared the spacecraft for launch after considering whether the crack could pose a safety threat during reentry at the end of the mission.
“We are confident that we understand the issue and can still fly the whole mission safely,” a member of SpaceX’s mission control team told the crew inside Dragon.
This mission, known as Crew-8, launched on a brand new Falcon 9 booster, which returned to landing a few minutes after liftoff at Cape Canaveral Space Force Station. The Falcon 9’s upper stage released the Dragon spacecraft into orbit about 12 minutes after liftoff. The four-person crew will dock at the space station around 3 am EST (0800 UTC) Tuesday.
Crew-8 will replace the four-person Crew-7 team that has been at the space station since last August. Crew-7 will return to Earth in about one week on SpaceX’s Crew Dragon Endurance spacecraft, which is flying in space for the third time.
The Crew-8 mission come home for a reentry and splashdown off the coast of Florida in late August of this year, wrapping up Crew Dragon Endeavour’s fifth trip to space. This is the current life limit for a Crew Dragon spacecraft, but don’t count out Endeavour just yet.
Fleet management
“Right now, we’re certified for five flights on Dragon, and we’re looking at extending that life out,” said Steve Stich, NASA’s commercial crew program manager. “I think the goal would be for SpaceX to say 15 flights of Dragon. We may not get there in every single system.”
One by one, engineers at SpaceX and NASA are looking at Dragon’s structural skeleton, composite shells, rocket engines, valves, and other components to see how much life is left in them. Some parts of the spacecraft slowly fatigue from the stresses of each launch, reentry and splashdown, along with the extreme temperature swings the capsule sees thousands of times in orbit. Each Draco thruster on the spacecraft is certified for a certain number of firings.
Some components are already approved for 15 flights, Stich said in a recent press conference. “Some, we’re still in the middle of working on,” he said. “Some of those components have to go through some re-qualification to make sure that they can make it out to 15 flights.”
Re-qualifying a component on a spacecraft typically involves putting hardware through extensive testing on the ground. Because SpaceX reuses hardware, engineers can remove a part from a flown Dragon spacecraft and put it through qualification testing. NASA will get the final say in certifying the Dragon spacecraft for additional flights because the agency is SpaceX’s primary customer for crew missions.
The Dragon fleet is flying more often than SpaceX or NASA originally anticipated. The main reason for this is that Boeing, NASA’s other commercial crew contractor, is running about four years behind SpaceX in getting to its first astronaut launch on the Starliner spacecraft.
When NASA selected SpaceX and Boeing for multibillion-dollar commercial crew contracts in 2014, the agency envisioned alternating between Crew Dragon and Starliner flights every six months to rotate four-person crews at the International Space Station. With Boeing’s delays, SpaceX has picked up the slack.
The Boeing delays have been good for SpaceX in the sense that NASA has awarded contract extensions to carry the Crew Dragon program through the end of the 2020s. NASA has purchased 14 operational Crew Dragon flights from SpaceX, compared to six Starliner flights from Boeing. On Sunday night, SpaceX launched the eighth operational Crew Dragon flight for NASA, and the 13th crew flight on Dragon overall.
While SpaceX is flying astronauts for NASA, the company is also launching all-private crews to orbit through deals with the Houston-based company Axiom Space and billionaire Jared Isaacman, who plans to perform the first commercial spacewalk later this year.
Business is booming, but SpaceX is reaching certification limits on the Dragon spacecraft faster than expected.
SpaceX has four human-rated Dragon spaceships, plus three Dragons designed for cargo missions. A fifth Crew Dragon is on track for completion later this year, and will probably make its first flight in early 2025, according to Stich. SpaceX officials have said this will be the final Crew Dragon spacecraft the company will build, and the fleet of five capsules will be enough to satisfy demand for Dragon missions until the next-generation Starship vehicle is ready to take over.
It will be at least several years, and possibly longer, until Starship is certified for human launches and landings. Until then, Dragons will continue launching on Falcon 9 rockets, even if some satellite missions shift to Starship.
SpaceX has flown some of its reusable Falcon 9 boosters as many as 19 times, nearly double the rocket’s original life expectancy, and is looking at certifying Falcon 9s for as many as 40 launches and landings.
Stich said NASA and SpaceX could settle on an intermediate number of flights, somewhere between five and 15, when they re-certify the Dragon spaceships. A later round of testing and reviews could eventually get to SpaceX’s 15-flight goal. “I would like to get out to seven to 10 flights for Dragon, but we’ll see where we get,” he said.
There are some parts, like heat shield material and parachutes, that SpaceX still needs to replace after each flight.
It’s always the valves
During preparations for the Crew-8 mission, SpaceX technicians swapped out valves inside the spacecraft’s propulsion system that appeared to show signs of corrosion. The valves control the flow of propellant to the Draco thrusters needed to maneuver the spacecraft in orbit, and to the more powerful SuperDraco engines that would only fire in the event of a launch abort.
“We’ve had some valve corrosion in the oxidizer valves, both on the low pressure side which is used on orbit, and then the side for aborts,” Stich said.
The Draco and SuperDraco thrusters consume a hypergolic mixture of propellants. Hydrazine is the fuel and nitrogen tetroxide is the oxidizer, and the propellants ignite when they come in contact with one another. Stich said technicians replaced several types of valves in the oxidizer side of the propulsion system, including tank isolation valves, Draco manifold valves, and throttle valves for the SuperDraco abort engines.
“All these were related to corrosion,” Stich said. “I would say all of them were done out of an abundance of caution.”
Engineers monitor how the valves cycle during checkouts between flights. “If the timing starts to look a little unusual, we’ll go in and replace those valves,” Stich said.
SpaceX
Bill Gerstenmaier, SpaceX’s vice president of build and flight reliability, said the valve issues could have something to do with wear and tear over the course of Crew Dragon Endeavour’s four previous space missions. But it probably has more to do with environmental factors, he said.
“I think it’s more how do we keep the environment pristine around the valve and prevent that (corrosion),” Gerstenmaier said. “We may make some design changes on the valves in the future to work on that area.”
Valve problems are nothing new for SpaceX or pretty much any other space company.
Boeing had trouble with corroded valves in the Starliner spacecraft. Investigators traced the cause of that problem to the reaction of nitric acid with moisture that seeped into the propulsion system. SpaceX apparently detected evidence of valve corrosion early, before it manifested into a more serious problem like that which grounded a Starliner test flight for nearly a year. Gerstenmaier said SpaceX added purges to the propulsion system to prevent contamination from building up on the valves.
Epps finally in orbit
Jeanette Epps, a mission specialist on the Crew-8 mission, waited nearly 15 years to fly in space after NASA selected her as an astronaut in 2009.
She was set to become the first Black astronaut to fly a long-duration stint on the space station in 2018, when she was training for launch on a Russian Soyuz spacecraft. But NASA replaced her with a backup crew member, and the agency never publicly stated a reason for the crew change.
It’s rare but not unprecedented for NASA to remove an astronaut from a crew soon before launch, but it’s usually for medical reasons, like an illness an injury. In those cases, NASA typically withholds details from the public due to privacy concerns, but the agency has identified a medical issue as the reason for replacing a crew member.
That was not the case for Epps. Some people outside the agency theorized Epps might have been removed from her flight for political or racial reasons, but Ars has reported that did not appear to be the case.
Epps, a former CIA technology intelligence officer, returned from Russia to NASA’s astronaut training base in Houston to await another assignment. In her public remarks after NASA removed her from the Soyuz crew, She was clearly disappointed. “It is something that I live with every day,” Epps said in 2018.
But she declined to “speculate” publicly on the reason for NASA’s decision. She said she passed all of her NASA and Russian training for the mission. “I didn’t have any medical conditions or anything like that,” Epps said in 2018. “And I didn’t have any family issues at all, either.”
NASA did make Epps eligible for future flight assignments fairly soon after she lost her Soyuz seat. In 2020, NASA added Epps to the crew slated to fly Boeing’s Starliner crew capsule on its first operational mission to the space station, but NASA later reassigned her to train for a SpaceX launch after continued delays on Boeing’s Starliner program.
She would likely have flown on SpaceX’s Crew-5 mission in 2022. But NASA and Russia’s space agency signed a long-planned barter agreement to allow SpaceX’s Dragon spacecraft to begin ferrying Russian cosmonauts to and from the space station and give US astronauts seats on Russian Soyuz flights. That meant a Russian cosmonaut took the open seat on the Crew-5 mission.
Epps was last member of NASA’s 2009 astronaut class to fly in space. Some astronauts in the 2009 class have already flown twice. In January, she told reporters she kept her spirits up by continuing to train. Despite the long wait to get into space, Epps is among the few astronauts who have trained to fly on Soyuz, Starliner, and Dragon.
“I’ve been pretty busy over the last few years still training, still working toward the goal of going to the space station,” Epps said.
Matthew Dominick, the Crew-8 commander, is also a first-time space flier. He was a US Navy test pilot who flew F/A-18 fighter planes before NASA selected him for the astronaut corps in 2017. Michael Barratt, the Crew-8 pilot and a flight surgeon, is a veteran of two previous flights to the space station, one on a Soyuz and another on a space shuttle.
Russian cosmonaut Alexander Grebenkin, another spaceflight rookie, rounds out the crew. He was a radio communications engineer and served in the Russian military before joining Russia’s cosmonaut corps.
March 3, 2024: This story was updated after the launch of SpaceX’s Crew-8 mission.