WASHINGTON — While NASA seeks to maintain an uninterrupted human presence in low Earth orbit, an agency official said a short-term gap between the International Space Station and commercial successors would not be “the end of the world.”

NASA’s current approach to its future in LEO counts on supporting development of commercial space stations with the goal of having at least one such station ready to support NASA astronauts and research by 2030, when the ISS is scheduled for retirement. A key question, though, will be whether any of the several companies working on such concepts will be ready by the end of the decade.

Speaking at a Nov. 20 meeting of the NASA Advisory Council’s human exploration and operations committee, Phil McAlister, director of NASA’s commercial space division, said the agency would not jeopardize safety to meet a schedule, following the lessons from the commercial crew program. “I do not feel like this is a safety risk at all,” he said. “It is a schedule risk and we are doing several things to mitigate that risk.”

One risk mitigation step is working with several companies, three of which — Axiom Space, Blue Origin and Voyager Space — have funded contracts or agreements with NASA to support initial work on their stations. Several others have unfunded Space Act Agreements to assist their own station plans, known by NASA as commercial LEO destinations or CLDs, or are working independently of NASA.

“Having more than one company in this stage of development, so you’re not relying on a single provider, really increases the probability that somebody’s going to be ready on time,” he said.

There is also some schedule flexibility in the transition between the ISS and commercial stations. McAlister noted there is a two-year overlap currently projected between the start of commercial space station operations around 2028 and the retirement of the ISS in 2030. “Less than that is certainly feasible,” he said of that overlap period. “This gives us a little bit of schedule margin.”

A third option is to extend the ISS beyond 2030, which would depend on the status of the ISS and willingness of ISS partners to continue station operations. Ken Bowersox, NASA associate administrator for space operations, said in a Nov. 2 speech that ISS retirement was “not mandatory” in 2030 and that there may some flexibility in that date should commercial stations not be ready.

In a later statement, Bowersox reiterated that NASA’s current policy is to retire the ISS in 2030 but that the agency “also prepares for a variety of scenarios” to ensure it can continue research in LEO. “The agency intends to maintain our continuous human presence in space for the benefit of humanity as we become one of many customers in a thriving commercial marketplace in low Earth orbit.”

But McAlister said even that goal of a “continuous human presence” could be reviewed. “If all of those mitigations fail, we would have a temporary gap in LEO presence,” he said. “That would be bad and I don’t want one, but if CLDs were not ready, we might have to accept a gap. And, personally, I don’t think that would be the end of the world.”

“A gap would not be great,” he said later in the meeting, “but I also don’t think it would be unrecoverable, either, especially if it was relatively short term.”

He added that flights by commercial crew vehicles, like SpaceX’s Crew Dragon and Boeing’s Starliner, “could lessen the impact of a gap.” Those vehicles, he said, could be equipped with research equipment and extra consumables to enable 10-day missions for “meaningful research.”

Other vehicles in development, including SpaceX’s Starship, a crewed version of Sierra Space’s Dream Chaser and a proposed Blue Origin crewed spacecraft known only as Space Vehicle, would also help fill any gap, he added.

Other agency officials at the meeting said it may be a few years before they know how likely it is a commercial station will be ready by the end of the decade. “It’s really hard to rate it” now, said Angela Hart, NASA manager of the CLD program.

She said NASA wouldn’t have better insight into commercial space station development schedules until after the agency awards what it calls Phase 2 contracts to certify those stations and purchase services. NASA currently expects Phase 2 contracts to begin in 2026.

“That first six months to a year, once that contract is awarded, is where I think we’ll have the best understanding of what our schedule is,” she said.

She added her program was working closely with the ISS program “to put some meat on that transition plan” from the ISS, including fallback options if commercial stations are not likely to be ready by the end of the decade. “Some of those key decision points are in ’26 and ’27.”

In another presentation at the meeting, Robyn Gatens, ISS director at NASA Headquarters, said there is some “timeline flexibility” for the transition, which will depend on both the readiness of commercial space stations and availability of a deorbit vehicle for the ISS. NASA is currently reviewing proposals for a U.S. Deorbit Vehicle, with a contract award expected in April 2024.

“In order to have no gap, it may require some flexibility in that timeline,” she said. That’s “tricky,” she added, because of the lead time of three years to procure additional cargo and crew transportation services for the ISS. “That introduces some challenges in that timeline flexibility.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...