ISS Deorbit Vehicle’s Launch Tied To Station Replacement

MILAN—NASA does not plan to launch SpaceX’s International Space Station (ISS) deorbit vehicle until it is sure the follow-on to accommodate astronauts and microgravity experiments is ready, Deputy Administrator Pam Melroy said.

The deorbit vehicle effectively needs to complete its mission within about 18 months of launch, she told reporters at the International Astronautical Congress here. That time pressure means NASA wants to make sure the follow on to the ISS is ready before it launches the deorbit vehicle.

“There is no way we should launch something that has a ticking clock until you have something else you are sure of,” she said.

NASA in June awarded SpaceX the $843 million U.S. Deorbit Vehicle contract to facilitate the ISS’s planned disposal starting in 2031.

It still needs to award the contract for the ISS follow-on effort. The space agency is combing through thousands of comments as it works to craft the final draft request for proposals for the Commercial Low Earth Orbit Development Program, an ISS replacement effort via commercial services. NASA hopes to award more than one contract and has funding to support multiple providers, according to Robyn Gatens, ISS director for the agency’s Space Operations directorate. The draft solicitation is due out in 2025, with NASA targeting contract award in 2026, Gatens said.

NASA wants to send astronauts into space to use the new service before it starts deorbiting the ISS. “We are on a bit of a tight schedule,” Gatens added.

Melroy said NASA has no plans to extend the life of the ISS but indicated that this remains an option if the replacement effort is too slow to materialize.

The agency has been working on the Low Earth Orbit Microgravity Strategy since the spring and released a draft plan in August. It is processing feedback to assess if it needs to make any changes to its plans.

One of the unresolved issues about NASA’s path is whether it will seek continuous stationing of astronauts in low Earth orbit once the ISS is gone—what it calls “continuous heartbeat.” Melroy said there is logic to having a permanent human presence to help oversee the scientific projects, but also from a national posture perspective.

However, she acknowledged the commercial service providers will need to evolve their offering, not unlike the period more than a quarter of a century ago when ISS components were first being launched to build the outpost. NASA may therefore spell out an initial usage requirement, along with requirements to evolve it, Gatens said.

NASA also is still assessing what it may do with some of the experiments and equipment now on the ISS. Some may transition to the new outposts, while other equipment may be returned to Earth or disposed of through the deorbiting.