You've probably heard about SpaceX's plans to use its giant new Starship vehicle to land people on the Moon and Mars, send numerous Starlink satellites or large telescopes into space, or perhaps even serve as a high-speed point-to-point terrestrial transport for equipment or people.
There's another application for SpaceX's Starship architecture that the company is studying, and NASA is on board to lend expertise. Though still in a nascent phase of tech development, the effort could result in repurposing Starship into a commercial space station, something NASA has a keen interest in because there are no plans for a government-owned research lab in low-Earth orbit after the International Space Station is decommissioned after 2030.
The space agency announced last month a new round of agreements with seven commercial companies, including SpaceX. The Collaborations for Commercial Space Capabilities (CCSC) program is an effort established to advance private sector development of emerging products and services that could be available to customers—including NASA—in approximately five to seven years.
This is separate from funded agreements NASA signed in 2021 with three industry teams led by Nanoracks, Blue Origin, and Northrop Grumman, each working on their own concepts for a commercial space station. Another company, Axiom Space, has a contract with NASA to develop a commercial module to be added to the International Space Station, with an aim to eventually use it as a centerpiece for a private-owned complex in low-Earth orbit.
NASA passed over SpaceX's bid for a funded space station development agreement in 2021, identifying concerns about SpaceX's plans for scaling its life-support system to enable long-duration missions and SpaceX's plan for a single docking port, among other issues. The space agency isn't providing any funding for the new CCSC effort, which includes the Starship space station concept, but the government will support the industry with technical expertise, including expert assessments, lessons learned, technologies, and data.
Apart from the SpaceX agreement, NASA said it will provide non-financial support to Blue Origin's initiative to develop a crew spacecraft for orbital missions that would launch on the company's New Glenn rocket. The agency also supports Northrop Grumman's development of a human-tended research platform in low-Earth orbit to work alongside the company's planned space station.
The other companies NASA picked for unfunded agreements were: Sierra Space's proposal for a crewed version of its Dream Chaser spacecraft, Vast's concept for a privately owned space station, ThinkOrbital's plan to develop welding, cutting, inspection, and additive manufacturing technology for construction work in space, and Special Aerospace Services for collaboration on an autonomous maneuvering unit to assist, or potentially replace, spacewalkers working outside a space station.
Despite the lack of NASA funding, the new collaboration announcement with SpaceX laid out—in broad strokes, at least—one of the directions SpaceX may want to take Starship. NASA said it will work with SpaceX on an "integrated low-Earth orbit architecture" that includes the Starship vehicle and other SpaceX programs, including the Dragon crew capsule and Starlink broadband network.
"This architecture includes Starship as a transportation and in-space low-Earth orbit destination element supported by Super Heavy, Dragon, and Starlink, and constituent capabilities including crew and cargo transportation, communications, and operational and ground support," NASA said.
Early days still
SpaceX's Starship program is moving forward primarily with billions of dollars in private funding. The rocket is designed to eventually be fully and rapidly reusable, with a 33-engine booster stage called Super Heavy and an upper stage—itself known simply as Starship—to accelerate into orbit. Once in space, the Starship could deploy a payload of up to 150 metric tons or be refueled by a tanker vehicle—also based on the Starship design—for expeditions to more distant destinations like the Moon or Mars.
Starship is made of stainless steel and measures about 164 feet (50 meters) tall with a diameter of 29.5 feet (9 meters), wider than the fuselage of a Boeing 747 jumbo jet. Before SpaceX can move on to demonstrate in-orbit refueling, the Starship lunar lander, or an eventual Starship-based space station, the company needs to get the rocket into orbit. The first full-scale test flight in April did not reach space, but SpaceX officials were pleased with the lessons they learned and are preparing for another test flight that will attempt to reach near-orbital velocity later this year.
NASA released more details about SpaceX's space station concept in a source selection document published several weeks after the original announcement of the collaboration agreements on June 15. What's still unclear is whether SpaceX is looking at ideas to turn the entire internal volume of Starship into a pressurized habitat for people, which would require major advancements in manufacturing and assembly in orbit to convert empty propellant tanks into a home for astronauts, researchers, or space tourists.
On the other end of the spectrum, Starship's crew cabin—already voluminous—may be able to eventually support long-duration stays in low-Earth orbit with a suitable life support system. The vehicle could also be fitted with external mounting plates for unpressurized experiments.
In the source selection statement, Phil McAlister, who heads NASA's commercial spaceflight division, wrote that SpaceX's proposal would provide capabilities to support NASA's need for a commercial space station after the retirement of the ISS.
"The proposed Starship capability in terms of size and reduced cost could have a far-reaching impact on the sustainable development of the LEO (low-Earth orbit) economy," McAlister wrote.
SpaceX has often pitched Starship as a solution for deep space transportation. NASA awarded SpaceX a $2.9 billion contract in 2021 to develop a variant of the Starship rocket as a human-rated lander for the Artemis program to return humans to the lunar surface. Since then, NASA has awarded SpaceX a contract to build and fly a lander for a second Artemis crew landing mission. Starship also fits in with Elon Musk's vision to establish a human settlement on Mars.
Closer to home, SpaceX has sold Starship as a vehicle that could eventually provide global point-to-point flights for people and cargo between destinations on opposite sides of the world.
Now SpaceX has proposed a plan for NASA to turn Starship into a commercial space station. "Starship could significantly impact crew and cargo transportation, and could itself become a large commercial LEO destination," McAlister wrote in the source selection statement.
"Adding increased confidence is the company’s plan to self-fund Starship development from its launch and satellite enterprises," McAlister wrote in a section discussing SpaceX's business approach for the Starship space station effort. "The only weaknesses in the proposal were the lack of a schedule to field its new capabilities and involving NASA in its ... milestones. Overall, strengths outbalance weaknesses."
On technical grounds, NASA said SpaceX's plan has strengths in its use of existing systems, demonstrated technical competence, and low dependence on other companies or organizations. But McAlister wrote that SpaceX's proposal was short on details about the concept and lacked information on technical risks or the schedule for how Starship could be used for crew transportation to low-Earth orbit or as an orbiting space station within the next five to seven years, one of NASA's goals guiding the collaborative commercial space agreements.
Nevertheless, NASA isn't putting any skin in the game with this program, and the agency determined the technical strengths also outweigh the proposal's weaknesses.
Not the first time this has been proposed
Repurposing a rocket into a space station is not a new idea. If you look at it optimistically, it's a way to essentially get a "free" space station by recycling a large structure that would otherwise be thrown away into something useful. But the idea comes with tall hurdles.
In the 1960s, NASA engineers had an idea for what might have been the world's first space station, created by converting the S-IVB upper stage of a Saturn IB rocket into a pressurized shirt-sleeve workshop. The concept would have involved two Saturn IB launches a day apart, one crewed with an Apollo spacecraft and the other without astronauts.
The Apollo crew would have installed equipment and introduced a life-supporting atmosphere into the S-IVB's hydrogen tank so they would live and work inside. This concept was known as the "wet workshop" because it would have launched "wet" with liquid hydrogen fuel in the tank.
In 1969, just days after the Apollo 11 lunar landing, NASA decided to go in a different direction. The decision led to the Skylab space station, known as a "dry workshop" because it was built on an S-IVB upper stage that launched without fuel on top of a Saturn V rocket in 1973. Three NASA crews lived on Skylab.
NASA and its contractors also studied using the space shuttle's external tank as the cornerstone of an orbiting space station. Engineers at Martin Marietta, the original builder of the shuttle fuel tank, assessed ways to convert the tank into an orbital platform outfitted with solar arrays and attachable experiments or payload modules. The most ambitious concepts would have used the tank's interior as an orbital fuel depot or as a large 27.5-foot-wide (8.4-meter) crew habitat, ideas outlined in a 1985 report by the Space Studies Institute, a group founded by the visionary physicist Gerard O'Neill.
But the space shuttle never lived up to its promised low costs and high flight rate, and the external tank never saw use after it was discarded after each shuttle launch.
A Houston-based company named Nanoracks is also working on technology that could eventually be applied to converting spent rocket stages into an orbiting space station. Nanoracks has partnered with Maxar and United Launch Alliance on some early-stage technology development in this area. One of the recent milestones was a small-scale demonstration in space last year to prove a robot could cut metal in microgravity, using a sample of material several inches in size that was representative of the tanks of a Centaur upper stage that flies on ULA's Atlas V rocket.
