donald trump has appointed his transportation secretary, Sean Duffy, as interim administrator of Nasa, six weeks after withdrawing the nomination of the Elon Musk ally and billionaire Jared Isaacman for the permanent role.

The president announced the appointment on Truth Social on Wednesday evening, praising Duffy’s work on transportation infrastructure and describing him as someone who would be “a fantastic leader of the ever more important space agency, even if only for a short period of time”.

Duffy, who will maintain his cabinet position while taking on Nasa duties, wrote on X: “Honored to accept this mission. Time to take over space. Let’s launch.”

Isaacman, who has flown multiple missions with Musk’s SpaceX, was widely viewed as Musk’s pick to lead Nasa. But trump withdrew that nomination in May, posting earlier this week that he was “surprised to learn” Isaacman was a “blue blooded Democrat, who had never contributed to a Republican before”.

The reversal follows an escalating beef between Trump and Musk and their respective camps, including a reportedly heated dust-up between Musk and Duffy at a White House meeting over cuts to FAA programs that support commercial spaceflight.

The appointment comes as Nasa faces an existential crisis. The agency is hemorrhaging scientific talent amid Trump’s proposed budget cuts that would slash the space science program from $7.33bn to $3.9bn annually. Under that proposal, Nasa’s total budget would fall from $24.8bn to $18.8bn.

About 900 Nasa employees departed in February, with another 1,500 signing up for voluntary separation programs through July, according to documents obtained by Politico. The exodus has prompted protests outside Nasa headquarters, with contractors and staff holding signs reading “Save Nasa” last week.

The Arizona senator and former astronaut Mark Kelly rhetorically asked what would have happened if this sort of mass departure happened during the cold war in the mid-20th century. “We would’ve lost the space race to the Soviets,” he answered himself. “And now we risk losing the next space race to China.”

Seven former Nasa science chiefs have also written to Congress, agreeing that the cuts would hand China an advantage in space exploration.

“If the administration is committed to countering the growing Chinese capability in space, the US needs to continue its investment in US space science, not cede it unilaterally,” they wrote.

Duffy, a former Republican congressman from Wisconsin who starred on MTV’s The Real World in 1997, brings no space background to the role. His appointment is seen as a signal that Trump intends to push through his controversial budget cuts, which would terminate dozens of science missions including the Mars Odyssey spacecraft that has been studying the red planet since 2001.

“While Nasa’s science missions have greatly expanded humanity’s understanding of the Earth, solar system, and universe, the current expenditure of over $7bn per year on over 100 missions is unsustainable,” the administration’s May budget request reads.

Since taking office as transportation secretary in January, Duffy has focused on rolling back what he calls “woke DEI policies” and Biden-era environmental regulations. His dual role overseeing both transportation and Nasa – agencies with combined budgets exceeding $30bn – tracks with Trump’s thinking on mixing assignments, notably Marco Rubio as secretary of state and acting national security adviser.

Janet Petro, director of Kennedy Space Center, had been serving as acting administrator since Trump’s inauguration in January.