NASA astronaut Scott Kelly lived on the International Space Station for a year-long mission to see how living in space changes the human body.

But the ISS might come to an early end, since President Trump wants to end NASA support for the station and shift the funding toward Mars missions and other goals.

Kelly hopes the US won't cut support to the ISS too early — and wants the world to continually have people living in space, a streak that we've kept alive for 18 years.

NASA astronaut Scott Kelly has spent 520 days in space, third-most among American astronauts.

Much of that time has been spent on the International Space Station (ISS). That includes 340 days as part of NASA's twin study, which is comparing Kelly to his twin brother, Mark, to find out how being in space changes the human body.

So the space station means something to Kelly — not necessarily the structure itself, but what it represents: humanity in space.

But the ISS' time orbiting Earth might come to an early end, since President Donald Trump wants to cut off funding for the ISS by 2025 to focus on planning future missions to Mars. (The plan called for the station to be de-orbited in 2028.)

That early timeline means we might break an important streak, Kelly recently told Business Insider while visiting our offices for an interview on our podcast, "Success! How I Did It."

"I personally think 2025 is a little premature," Kelly said. "My hope would be that we could make a commitment to never having all of the people of Earth on the planet at one time ever again. We're on this 18-year run. We would hate to mess up that kind of a streak. So I would hope that we could figure out a way to support the ISS into the future, because now it's kind of hitting its stride."

Construction began on the ISS in 1998 and it's still being added to. The ISS will of course eventually wear out and have to come down — the question is when that will happen, and whether a replacement will be ready.

"[U]nderstanding that hardware ages and gets old, at some point we'll have to make a decision to do something else," Kelly said. "Hopefully the 'something else' involves people staying, and living, and working in space for long periods. Maybe you could replace it with a space station on the moon, or a space station at other interesting points throughout our solar system."

Trump wants private industry to take over most of what happens in low-Earth orbit.

Several companies are preparing to step in: Robert Bigelow of Bigelow Space Operations said he wants to launch inflatable modules into space that could be rented by countries who want to conduct experiments in space or by tourists who want to pay a premium for the trip of a lifetime. But Bigelow's work and the operations of other companies like SpaceX depend on NASA too, since they've so far worked together.

China is also strategizing for a potential new orbital laboratory.

Future US space-exploration plans will require a station that can serve as a base of operations for missions to the moon, Mars, and other parts of the solar system, but we don't know when that will come together.

In the mean time, Kelly said we could continue the streak of keeping humans in space in a variety of locations.

"A gateway point, or LaGrange points [near the moon] — there are a lot of other possibilities," he said. "Potentially, you could take [newer] parts of the space station, too, and repurpose it. It is a pretty amazing facility we have."

Dave Mosher and Rich Feloni contributed to this post.