The White House on Monday released a budget plan that would halt funding for the International Space Station (ISS) after the year 2024 and ultimately turn it over to the private sector.
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Under President Donald Trump's 2019 proposed budget, the government would set aside $150 million to encourage commercial development and use future savings to aim for the moon.
Many space experts and legislators are expressing concern. Sen. Bill Nelson, a Florida Democrat who rocketed into orbit in 1986, said "turning off the lights and walking away from our sole outpost in space" makes no sense.
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"As a fiscal conservative, you know one of the dumbest things you can do is cancel programs after billions in investment when there is still serious usable life ahead," Sen. Ted Cruz (R-Tex.) added last week.
And Frank Slazer, the vice president of space systems for the Aerospace Industries Association, told the Washington Post, "It will be very hard to turn ISS into a truly commercial outpost because of the international agreements that the United States is involved in. It's inherently always going to be an international construct that requires U.S. government involvement and multinational cooperation."
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Here are five things to know about the orbiting laboratory at the center of the debate:
1. ISS is the largest structure humans have ever put into space
With its primary construction completed between 1998 and 2011, the ISS is the largest structure humans have ever put into outer space. The orbiting station also continues to grow, as new missions and experiments are introduced.
Although the U.S. has invested about $100 billion in the project, ISS is considered a multi-nation construction project, according to Space.com.
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2. Scientists from around the world work at ISS
The station has been continuously inhabited by scientists since Nov. 2, 2000. As of January, 230 people representing 18 countries have spent time on the orbiting lab. The majority of these hail from the U.S. (145 total). Russia has sent the second highest number of scientists to the station (46).
Research time spent by astronauts on the station is allocated to space agencies around the world according to the amount of resources and money they contribute.
Regular contributions are made by 15 agencies, which include NASA (United States), Roscosmos (Russia), the European Space Agency, Japanese Aerospace Exploration Agency, the Canadian Space Agency and more.
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3. How big is the station?
According to NASA, the inside of the station is the size of a house with five bedrooms. It contains two bathrooms, a gymnasium and a big bay window. At any given time, the station can accommodate six people. Weighing in at almost a million pounds, the station's total size is big enough to cover a football field, with the end zones included.
4. NASA envisioned building the station decades before it was complete
As early as 1959, before man even walked on the Moon, NASA envisioned constructing a space station to orbit Earth, according to Popular Science. A more concrete idea for a 100-person space base was put forth a decade later, but the immense cost of using expendable rockets brought an end to that dream.
In 1973, NASA created a temporary space station with repurposed rocket craft material. The "Skylab" hosted three astronauts, proving that humans could live and work in space, as well as carry out construction.
The U.S. eventually moved forward with forging international partnerships to help cover costs and move forward with the ISS.
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5. Why does the space station matter?
The research carried out on ISS cannot be conducted on Earth. Scientists use the spacecraft to study how living in outer space affects humans. NASA has also learned how to keep a spacecraft working for an extended period of time, providing incredible insight that may one day allow humans to travel further into space.
More about the Trump administration’s plans for the International Space Station.
The Associated Press contributed to this story.