Sierra Space says it has demonstrated in a ground test that a full-scale inflatable habitat for a future space station can meet NASA’s recommended safety standards, clearing a technical gate on the road toward building a commercial outpost in low-Earth orbit.
During a December test at NASA’s Marshall Space Flight Center in Alabama, Sierra Space’s 300 cubic meter inflatable structure withstood five times the pressure it would need to handle in space. The so-called ultimate burst pressure test was designed to measure the limits of the soft goods technology Sierra Space is developing alongside ILC Dover, which also built spacesuits for NASA.
The 27-foot-diameter (8.2-meter) inflatable structure burst at 77 psi, exceeding NASA’s recommended safety standard of 60.8 psi, which is four times the module’s real-life operating pressure at 15.2 psi.
Perhaps best known for developing the Dream Chaser spaceplane, Colorado-based Sierra Space also manufactures satellites and is one of several companies in the mix for helping build a new commercial space station to replace the International Space Station.
“We’re ecstatic over the results,” said Shawn Buckley, senior director of engineering and chief technologist for Sierra Space’s EarthSpace Systems division. “Transitioning from our from our sub-scale articles, we’ve done a series of tests to validate our architecture. And being able to go into our first full-scale LIFE (Large Integrated Flexible Environment) burst test, to meet the safety factor by 27 percent, was just an amazing accomplishment by the team.”
Sierra Space is partnering with Blue Origin on a commercial space station concept called Orbital Reef. If the companies see it to fruition, Orbital Reef could become a hub for research, manufacturing, tourism, and other applications in low-Earth orbit.
The inflatable technology from Sierra Space is similar to the work performed by Bigelow Aerospace, which pioneered inflatable habitat tech for more than 20 years before laying off its entire workforce in 2020. Buckley worked on Bigelow’s inflatable habitat technology for more than 10 years, then joined Lockheed Martin for two years. In 2022, he took a leadership position overseeing Sierra Space’s space station work.
Bigelow’s design centered on a 330 cubic meter inflatable habitat, while Sierra Space’s design is slightly smaller in volume. Buckley said he couldn’t state definitively whether the LIFE burst test in December was the largest such test of an inflatable habitat design, due to restrictions about what he could say about his previous work at other companies.
“I will say that this is the largest full-scale habitat that has been publicly announced in this architecture being tested,” he told Ars in an interview.
Certifying for spaceflight
The full-scale burst test of Sierra Space’s LIFE habitat follows a series of sub-scale tests last year.
“What we’re doing is we’re moving through a soft goods certification of our pressure shell,” Buckley said. “This was the first test in that road to being certified. We have a very, very busy 2024. At the end of ’24 or beginning of ’25, Sierra Space’s goal is to certify our pressure shell, and that will happen through a series of sub-scale and full-scale tests. This was just the first test, and moving forward, we’ll have two more full-scale burst tests.”
According to Buckley, Sierra Space has roughly 300 employees working on the LIFE habitat development, including the inflatable structure itself, life support systems, power, communications, and propulsion. But before Sierra Space can tack on those other critical elements needed to fly the habitat in space, the company has to show the structure itself can withstand the rigors of spaceflight.
“When we say certify, it means show that we have a consistent build, a consistent process, and a consistent architecture which can be repeatable,” Buckley said. Sierra Space also must prove it can repeatedly meet NASA’s recommended safety factor of four times the pressure the habitat will see in orbit.
The LIFE habitat’s inflatable shell is primarily made of a material called Vectran. “This is a material which gives you high strength and low elasticity,” Buckley said.
According to Kuraray, a Japanese manufacturer of specialty chemicals, fibers, and resins, Vectran is a “high-performance multifilament yarn spun from liquid crystal polymer.” Pound for pound, Vectran is five times stronger than steel and 10 times stronger than aluminum, Kuraray says on its website.
Technicians mold the Vectran into straps, which are weaved together to give the pressure shell the strength it needs to hold pressure in space, Buckley said. A series of threads, stitches, and tapes also make up the structure.
The recent full-scale burst test will provide data for a milestone on the Orbital Reef program with NASA, which has a $172 million funding agreement with the Blue Origin-led Orbital Reef team to develop technologies for a future space station.
“We are well on our way to having our habitats ready for launch in 2026,” Buckley said. Last year, Sierra Space disclosed plans to launch a LIFE habitat into orbit as a pathfinder before Orbital Reef. This could fly by the end of 2026, said Tom Vice, Sierra Space’s CEO, in a presentation last year.
Sierra Space’s pathfinder could be used for commercial pharmaceutical and biotech research, Vice said. It would also demonstrate technologies for Orbital Reef, and provide Sierra Space with a “revenue-generating space station that is focused around next-generation breakthroughs,” he said.
A crewed version of Sierra Space’s Dream Chaser spaceplane could ferry people to and from the LIFE pathfinder and Orbital Reef. The Dream Chaser is slated to launch on its first flight in a cargo-only configuration later this year. Sierra Space spun off from Sierra Nevada Corp. in 2021 as an independent company.
In September, CNBC reported the Orbital Reef project was in limbo and that it was not a top priority for Blue Origin or Sierra Space. Ars and Reuters also reported on the anticipated divorce between Blue Origin and Sierra Space. A few days later, Blue Origin posted on the social media platform X that it was still working on Orbital Reef.
“We want to be market positioned, whether it’s our own internal module, whether it’s on Orbital Reef or another platform, we want to make sure that we mature our technology so that in 2026 we’ve got a ready state for this tech,” Buckley said. He added that Sierra Space will “probably increase our team members” working on the LIFE habitat program.
Sierra Space laid off 165 employees and let go of additional contractors in November upon the completion of the first Dream Chaser spaceplane. This had “no impact” on the LIFE habitat program, according to Buckley.
Replacing ISS
There have been longstanding questions about the private sector’s commitment to developing a commercial space station. Private investment in commercial stations lags far behind investment into core space industry markets like launch and satellite manufacturing. NASA is providing funding to companies working on space station projects, with the understanding that the companies themselves also contribute private money.
NASA’s funding alone isn’t enough to pay for a commercial space station—NASA calls these Commercial LEO Destinations (CLDs)—and the agency is bracing for government-wide budget cuts in the next few years.
The International Space Station is scheduled for retirement in 2030. A top NASA official said in November that it might be time to accept a gap in space station access in low-Earth orbit after the decommissioning of the ISS. NASA wants to continue to send astronauts into low-Earth orbit to perform research after the ISS is gone, and while the agency’s own human spaceflight missions focus on the Moon and Mars. Maybe NASA astronauts could temporarily use a commercial crew capsule from SpaceX or Boeing as a stopgap until someone deploys a commercial station.
“That would be bad, and I don’t want a gap,” said Phil McAlister, NASA’s director of commercial spaceflight. “But if the CLDs are not ready, we might have one. Personally, I don’t think that would be the end of the world. It would not be unrecoverable, especially if it’s relatively short-term. It might impact some research somewhat, but we could leverage Crew Dragon and Starliner to lessen the impact of a gap.”
Apart from the Blue Origin-Sierra Space partnership on Orbital Reef, Voyager Space, and Airbus have a joint plan to build an outpost called Starlab in low-Earth orbit, and Axiom Space is building modules it will attach to the International Space Station, with a longer-term goal of detaching its modules to form an independent laboratory in space. Axiom also has NASA funding support.
These companies all have funding agreements with NASA to work on space station tech. Northrop Grumman was working on its own concept for a commercial space station, but last year, it abandoned its leadership role and joined Voyager and Airbus as a junior partner on the Starlab project.
Earlier this month, NASA announced it will reallocate the funding originally committed for Northrop Grumman to the Orbital Reef and Starlab teams. Orbital Reef will get an additional $42 million, bringing the total NASA award to $172 million. Starlab’s team will receive another $57.5 million for a total NASA funding commitment of $217.5 million.
A private startup named Vast also plans to launch its own space station without any existing NASA contracts. So, some serious government and private money is flowing into commercial space station projects. But so far, there’s not enough to make a privately owned outpost a reality. Although it is significantly larger than any of the commercial stations, the ISS cost more than $100 billion to build, and NASA spends more than $3 billion per year to operate it and pay for cargo and crew transportation.
A commercial space station will undoubtedly be less complex and costly than the ISS, but will certainly be a multibillion-dollar investment over the program’s life.
The Starlab station would have originally been built using inflatable modules supplied by Lockheed Martin. But Lockheed Martin pulled out of its leading role on Starlab, and Airbus took on the role of building pressurized modules for the station. These modules will be rigid metallic structures, not inflatable ones.
Matthew Kuta, Voyager’s president, told Ars last year that moving away from inflatable modules to metallic structures, similar to those on the ISS, will result in a quicker development schedule and lower costs.
“One of the things that’s really important is speed,” Kuta said. “Metal modules are just much more proven out; they’re much more cost-effective… An inflatable as a primary habitat has never flown in space.”
The benefits of inflatable modules are clear. They can launch in a deflated configuration to fit inside the payload fairing of a rocket, then expand once in orbit. Sierra Space says the LIFE habitat is one-third the volume of the ISS, and could be launched on a single rocket.
Bigelow Aerospace launched two 11.5-cubic meter inflatable modules on standalone test flights in low-Earth orbit in 2006 and 2007. Bigelow’s next pressurized space module was a 16-cubic meter inflatable structure that launched to the International Space Station in 2016. It’s been there for nearly eight years, with excellent performance.