There’s no country better at solving hard problems than the United States, and there’s no better example of that than NASA. We put people on the moon in the 1960s with computers less powerful than the smartphone in your pocket. We built and launched a reusable rocket ship in the 1980s and used that to build a space station where astronauts can live and work in orbit. Just last week, we watched four astronauts launch an American-made rocket to the space station from American soil. NASA makes us proud to be Americans. And even more so, the agency is an engine of discovery and innovation that benefits all of us.

I’m worried that President Trump is about to slow that engine down — and with it decades of American progress. That includes progress made during his own first term. Mr. Trump’s ongoing attempts to slash NASA’s work force and gut its budget send a message that America’s leadership in space is optional. It isn’t.

For more than 50 years NASA primarily designed, owned and operated all of its spacecraft, from the first Mercury rocket launch in 1960 to the space shuttle I first piloted in 2001. When NASA announced it was changing all of that by contracting with commercial companies to bring crew and cargo to low Earth orbit, I thought the idea was pretty crazy. It was 2010, and I was training to be the commander of the final mission of the space shuttle Endeavour. I spent hundreds of hours in the simulator with my crew, preparing us to be ready for anything that came our way. I didn’t trust that private companies could pull this off because they lacked the experience NASA engineers had. There’s no margin for error when you’re 250 miles above the Earth’s surface.

But I was wrong. Today, thanks to NASA’s investments and guidance, commercial spaceflight isn’t just working; it’s cheaper, faster and more flexible than what the agency could provide on its own. The first Trump administration and the Obama and Biden administrations backed a model of awarding small, fixed-price contracts to multiple space companies to develop new spaceflight technologies. Using calculated risks and competition, that model is delivering big results.

SpaceX, the rocket company run by Elon Musk, now takes astronauts and cargo to the International Space Station, and Northrop Grumman delivers cargo with its Cygnus spacecraft. NASA is working with private companies to build moon landers and deliver science experiments to the lunar surface. We’re on the brink of returning American astronauts to the moon through the successor to the Apollo program, Artemis, which came together during Mr. Trump’s first term and brings international partners into the fold.

The growth of these private space partnerships is making America safer — while China and Russia mainly stick with government-owned launch systems, the U.S. Defense Department uses commercial launch services. That means the satellites our military and intelligence community use to communicate, detect missile launches and track threats get to orbit potentially cheaper and faster than our adversaries.

Here’s the crazy thing: All of this progress is now at risk, including the very things that made NASA successful under Mr. Trump’s first administration.

NASA is reportedly losing up to 4,000 employees, including some of its most experienced and specialized workers, because Mr. Trump is trying to take a sledgehammer to the civilian work force. It has a stand-in administrator in Sean Duffy, who has a second job running the Department of Transportation. And in May the Trump administration proposed a 24 percent cut to NASA’s budget — the largest single-year cut in history.

Ensuring a continued American presence in space is crucial to keeping our country’s engine of science and innovation moving. But Mr. Trump has proposed reducing crew and cargo transportation to the International Space Station. His team is slashing yearslong NASA science missions that could unlock mysteries about Mars and reveal which planets outside our solar system could support life, among so many other discoveries that would keep the United States on the leading edge of space research. And his proposed budget calls for cutting short the Artemis program, which would mean abandoning his original plan of establishing a long-term American presence on the moon.

Artemis was started to boost American innovation and inspire the next generation of American scientists and engineers, just like the Apollo program did for children like my brother and me when we watched the moon landings from our living room floor. NASA and its private partners need a consistent goal that outlasts presidents. But now Mr. Trump is scrambling our space strategy.

While the United States is debating the mission, China is on the move — it’s built its own space station, landed rovers on the moon and is planning crewed lunar missions to launch by decade’s end. Just as in other sectors, if America abandons space to China, China will get to write the rules of the road and other countries will partner with China instead of us.

NASA’s success has always depended on bold goals, clear leadership and trust in American ingenuity. A well resourced agency stocked with the best minds in the world, taking on the most ambitious missions in human history, is the key to that success. If the White House remembers that — and backs it with action — America’s space program will continue to lead the world and drive innovation forward for another generation.

Mark Kelly is a U.S. senator from Arizona and a former NASA astronaut.

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