photo of the international space station
The International Space Station as seen from a Crew Dragon spacecraft in 2021. Credit: NASA

WASHINGTON — NASA is proposing a hybrid contract approach for procuring a vehicle to help deorbit the International Space Station at the end of the decade, combining elements of cost-plus and fixed-price contracts.

NASA released a draft request for proposals (RFP) May 4 for what the agency calls the United States Deorbit Vehicle (USDV), a spacecraft that would dock to the station and perform a controlled reentry of it. NASA is seeking feedback on the draft through the end of the month before releasing a final RFP this summer.

One notable aspect of the draft RFP is the use of what NASA calls a “hybrid” contract structure. NASA proposes to start with a cost-plus contract, where the contractor is compensated for its costs plus an incentive fee, for the design of the deorbit vehicle through critical design review. Production of the vehicle and other activities will be covered by a fixed-price contract.

The agency didn’t elaborate on its choice of this hybrid approach in the draft RFP or related documents. The agency said it is seeking feedback on aspects of that approach, including the “exit criteria” for going from the cost-plus to the fixed-price phases of the contract.

NASA requested $180 million in its fiscal year 2024 budget proposal in March to start work on the deorbit vehicle, which the agency says will offer redundancy to earlier plans to use Russian Progress cargo vehicles to deorbit the station at the end of its life.

Kathy Lueders, at the time NASA associate administrator for space operations, said during the rollout of the budget proposal that NASA anticipated spending “a little bit short of about $1 billion” on the deorbit vehicle. “We’re hoping to get a better price than that” when industry submits its proposals, she added.

The publicly available documents don’t go into details about the technical specifications for the deorbit vehicle. However, the agency said there were no major changes to its plans since the release of a request for information (RFI) last November.

NASA said then it anticipated launching the deorbit vehicle about one year before reentry, docking to the forward port of the station’s Harmony module. The vehicle would primarily operate during the final days before reentry, once the station’s orbit has decayed to an altitude of 220 kilometers. The vehicle would perform one or more “shaping” burns to lower the orbit’s perigee to 160 kilometers, followed by a final deorbit burn.

At the time of that RFI, NASA was considering options to procure the deorbit vehicle as a service. However, NASA now intends to take ownership of the deorbit vehicle and manage its operations. NASA will separately procure a medium-class launch of the deorbit vehicle, although the agency is asking companies in the draft RFP if their vehicles would be compatible with that class of launch.

Some in industry had seen the proposed deorbit vehicle as an opportunity to develop or demonstrate commercial systems for deorbiting or servicing spacecraft. However, the decision not to pursue a services approach, as well as specific technical requirements for deorbiting the ISS such as the ability to operate even after suffering two failures, made that less feasible.

NASA sees the deorbit vehicle as a one-off design intended exclusively for deorbiting the station. “NASA wants to emphasize that safety and reliability are paramount in the USDV requirements to ensure the safe decommissioning of the ISS,” it stated in the cover letter accompanying the draft RFP. “This emphasis should be approached with the recognition that it will be a single-use vehicle.”

NASA is currently planning to operate the ISS to 2030. The other partners have also agreed to that timeline with the exception of Russia, which recently announced it would remain on the station to 2028.

The draft RFP indicates some flexibility in the timing of the station’s deorbit. NASA is asking prospective bidders if it is feasible to deliver the completed deorbit vehicle by September 2027 to be launched as soon as January 2028, a “contingency” launch date. The draft RFP also includes options to extend the contract, set to run to March 2031, to as late as September 2035, suggesting NASA is reserving the ability to extend the ISS beyond 2030.

NASA says it expects to release the final RFP on or around July 12, with proposals due Aug. 28. It anticipates making a contract award in early January 2024.

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...