Jeff Bezos’s owned space firm Blue Origin is suing Nasa for awarding a $2.9 billion lunar lander contract to Elon Musk’s SpaceX.
The former Amazon boss’s firm said there were “fundamental issues” with the deal, calling it unfair.
The row stems from a decision in April to hand the deal to one company, not two as expected, because of a funding shortfall.
In a court filing on Friday, Blue Origin said it continued to believe that two providers were needed to build the landing system, which will carry astronauts down to the Moon’s surface as early as 2024.
It also accused Nasa of “unlawful and improper evaluation” of its proposals during the tender process.
“We firmly believe that the issues identified in this procurement and its outcomes must be addressed to restore fairness, create competition and ensure a safe return to the Moon for America,” Blue Origin said.
At the time of the award, Nasa’s human exploration chief, Kathy Lueders, admitted that the space agency’s current budget precluded it from selecting two companies. That was after Congress granted it only $850 million of the $3.3 billion it requested for the project.
Nasa also cited the proven record of orbital missions by Elon Musk’s SpaceX firm as a factor in the award. Cost is also thought to have played a role: SpaceX’s bid was the lowest-priced by some distance.
In July, Mr Bezos offered to cover up to $2 billion of Nasa’s costs in order to be reconsidered for the contract, but he was rebuffed.
US watchdog the Government Accountability Office (GAO), meanwhile, rejected a complaint from Blue Origin and defence contractor Dynetic, saying that Nasa had not “acted improperly” in handing the contract to just one firm.
Nasa must file a response to the legal action by 12 October. SpaceX is yet to comment on the lawsuit.
Under its Artemis programme, Nasa hopes to return humans to the moon for the first time since 1972.