NASA, SpaceX Share Updates on ISS Deorbit Vehicle

In a teleconference on July 17th, NASA and SpaceX provided additional information about the United States Deorbit Vehicle (USDV), the spacecraft which will be tasked with pushing the International Space Station out of orbit at the end of its lifetime. Details about the design and operation of the USDV shed more light on this vehicle, the cornerstone of NASA’s efforts to retire and replace the ISS.

NASA and its international partner agencies have chosen to dispose of the ISS in the Earth’s atmosphere once it reaches the end of its operational lifespan in 2031. This is a delicate matter: the station is not designed to handle large forces, and must be deorbited quickly and precisely to ensure any remaining debris lands safely in the ocean. The USDV therefore needs to carry a lot of fuel and provide as much force as the station can manage. The USDV will also work in concert with the station’s own attitude control thrusters on the Russian segment, keeping the vast structure pointed in the right direction for as long as possible.

The contract to build the USDV was awarded to SpaceX on June 26th. During the teleconference last week, Dana Weigel, manager of NASA’s ISS program, and Sarah Walker, director of Dragon mission management at SpaceX, provided further insight into the nature of SpaceX’s spacecraft design. The SpaceX USDV is based on the company’s Dragon spacecraft, consisting of a Dragon capsule and a service module “trunk.” Overall, the USDV leverages existing hardware and designs from SpaceX’s other spacecraft, helping to buy down risk for this important mission.

The capsule portion of the USDV will be modified from an existing spacecraft in SpaceX’s fleet, and provides a docking port to attach to the forward port of the space station’s Harmony module. It is not clear if the capsule will be accessible to crew members, as with a typical Dragon spacecraft; the USDV is not required to house astronauts for any reason. The capsule also contains no recovery hardware, as the USDV will remain attached to the ISS throughout its disposal.

Meanwhile, the service module will be an entirely new design compared to a standard Dragon trunk. This section contains most of the critical systems for the spacecraft, including additional propellant, large solar arrays, power and thermal control systems, and, most crucially, thrusters. The USDV features an array of 46 thrusters to provide both attitude control and the high thrust needed to perform the station’s final deorbit burns.

The procurement of the USDV was somewhat unusual in offering bidders the option of either a Firm, Fixed-Price award or a more traditional Cost-Plus contracting scheme. In keeping with its typical experience working with NASA, such as Commercial Crew and the Artemis Human Landing System, SpaceX has opted for the former. However, the award still represents a novelty for the company, as the USDV will be owned and operated by the government, rather than SpaceX itself.

Furthermore, a launch vehicle for the USDV will be procured through NASA’s typical Launch Services Program process, in which SpaceX competes with other providers. Indeed, the high mass of the USDV may be a challenge for SpaceX’s Falcon family; Walker put it at about 30 metric tons, though she noted SpaceX believes it can support the mission and intends to compete for the award.

The USDV contract is an unusual one for SpaceX, which has recently placed a majority of its focus as a company on its key future projects: Starship and Starlink. While a wide variety of launch contracts contribute to funding these efforts, the development of a new, apparently one-off spacecraft stands out from SpaceX’s typical repertoire. The USDV, however, may represent for SpaceX what it represents for spaceflight at large: the bridge to a future ecosystem in low Earth orbit.

As NASA hopes to usher in a new generation of commercial platforms in space, a thriving orbital economy will require new kinds of spacecraft services. SpaceX’s Dragon spacecraft has proven its worth shuttling crew and cargo to and from the ISS, but the vehicle in its current configuration is not well-suited to reboosts or other orbital maneuvers that might be required for future stations. Much as Dragon XL will extend SpaceX’s commercial services to NASA’s Gateway lunar space station, work done for the USDV may help SpaceX extend their commercial services to future destinations.

For now, the USDV fills a single, clearly-defined role: to deorbit the International Space Station. In so doing, this spacecraft—among the last to visit the ISS—will mark a permanent transition in the future of human spaceflight.

Edited by Nik Alexander and Emily B.