Although the International Space Station is scheduled to be replaced in the 2030s, it will take a long time for the orbiting laboratory to officially reach the end of its life, NASA warns.
SpaceX’s new reentry vehicle won’t propel the International Space Station (ISS) into Earth’s atmosphere until 12 to 18 months after the complex “drifts” out of its normal orbit. “We’ll keep the crew on board for as long as possible, so they’re available to help maintain the station and keep it healthy,” NASA ISS program manager Dana Weigel told reporters today (July 17) during a live briefing on the reentry plan.
“Our plan is for the astronauts to leave about six months before final reentry, when the ISS will be about 220 kilometers (137 miles) above Earth,” Weigel said, explaining that this is the lowest altitude at which manned vehicles are typically allowed to fly. For comparison, the ISS’s typical orbit is 400 kilometers (250 miles) above Earth.
NASA selected the deorbit vehicle last month, saying it would provide SpaceX with up to $843 million for development (that amount does not include launch costs). The choice comes after NASA asked the aerospace community for proposals in March 2023, and again in September 2023, for a concept for a “space tug,” or “US Deorbit Vehicle (USDV),” that could lower the U.S. sections of the ISS.
Related: NASA Selects SpaceX to Build Deorbit Vehicle for International Space Station
SpaceX’s deorbit vehicle will be based on the design of the company’s Dragon spacecraft, which has sent cargo variants to the ISS since 2012 and launched crews to the lab since 2020. Of note is an “enhanced trunk section” that will feature additional propellant tanks, as well as engines, avionics, power generation and other elements customized for the complex mission, Sarah Walker, SpaceX’s director of Dragon mission management, said during the same briefing.
“One of the benefits of leveraging Dragon’s rich flight history is that we can continue to use NASA-certified hardware for a number of key systems, such as the docking system,” she said. “While the assembly level design is specifically developed for this mission,” she added, “we are intentionally using component building blocks that NASA is familiar with and that SpaceX has extensive experience building and operating.”
SpaceX is the dominant player in ISS operations. The company, founded by billionaire Elon Musk, benefits from vertical integration (owning much of the supply chain needed for space launches) in a way that its competitors do not. Not only does SpaceX launch both crew and cargo to the ISS, it is also funded by NASA for a Starship contract to land astronauts on the moon. (The Starship contract is behind schedule, and is one reason the first human lunar landing in more than 50 years has been delayed by a year, to at least 2025, because NASA wants a “significant number” of successful Starship launches before taking astronauts on board.)
SpaceX also launches lucrative satellite missions into space funded by the military and the U.S. government, and launches its own Starlink broadband satellites several times a month aboard SpaceX’s Falcon 9 rocket, one of the world’s most reliable launchers. (Falcon 9 is currently grounded following a rare launch failure, though SpaceX hopes the Federal Aviation Administration (FAA) will clear it for takeoff again while the mandatory investigation into the accident continues.)
Related: SpaceX Falcon 9 rocket failure forces NASA to revise schedule for launching astronauts to ISS
SpaceX’s approach to the ISS deorbit vehicle was praised in the official source selection document posted on the government procurement website SAM.gov on Tuesday (July 16). “SpaceX’s approach significantly increases the likelihood of producing a highly reliable USDV, minimizes development and testing, reduces the risk to the government of late USDV delivery, and significantly improves the potential for contract success,” the document states.
Northrop Grumman (NG), a major SpaceX competitor that currently launches cargo missions to the ISS, estimated the total cost of the project to be higher. The paper adds that it is “particularly concerning” that NG’s space tug idea may not work at certain “solar beta” angles. (These angles are between the ISS’s orbit in space and an imaginary line connecting the sun and Earth, according to NASA.)
“With this weakness, NASA faces a choice between a potentially lengthy and costly redesign of the NG system that would allow NASA more flexibility when planning ISS deorbit operations, or launching a USDV that limits NASA’s planned deorbit schedule,” the source selection document notes.
Currently, most members of the ISS consortium have committed to operations through 2030, while Russia says it will remain there until at least 2028. Russia is leaving the consortium following the internationally condemned war in Ukraine, an exit initiated without provocation in 2022. As most of the world withdrew from Russia’s launch contracts, it turned to China and North Korea, often cited in congressional testimony as countries posing security risks to the United States.
NASA officials have stressed that the end of the ISS mission will depend on when the new commercial replacement stations, funded by the agency, are ready. “We want the commercial stations to support it, and when they’re ready to go, that’s when the ISS gets out of the way,” Steve Stich, the commercial crew program manager at NASA’s Johnson Space Center (JSC) in Houston, said during a briefing earlier this year.
There are financial and political reasons for the Americans to keep the experiments going as long as possible, at least as far as lawmakers are concerned. Tiangong, a Chinese space station, could take over a large chunk of the lucrative low-Earth orbit market if the United States lets the ISS go early, Congress warned earlier this year. NASA is barred from entering into bilateral or coordination agreements with China under a 2011 congressional directive known as the Wolf Amendment.
Several companies are currently building commercial outposts. Axiom Space plans to place modules on the ISS before detaching them to form a free-flying assembly known as Axiom Station.
Other independent stations are also in the works. Orbital Reef includes Amazon, Boeing, Blue Origin and Sierra Space; the Voyager Space-led Starlab complex includes Lockheed Martin and Northrop Grumman; and Vast Space plans to launch the first Haven-1 module into space in 2025.