By Hannah Thomas-Peter, climate change correspondent
NASA chief Jim Bridenstine has told Sky News he believes the next person to walk on the moon will be a woman – as he warned that space is "getting more and more dangerous" with some nations intent on destroying it.
Mr Bridenstine said the planned US "space force" – which President Donald Trump wants to become the sixth branch of the American military – is meant to deter countries that "believe they are going to get an advantage by destroying space".
The US, Russia, China and, most recently, India have all successfully demonstrated the capability to shoot satellites out of space.
In an interview with Sky News to mark the 50th anniversary of the moon landings, Mr Bridenstine, who is NASA's administrator, said: "There are countries around the world that believe they are going to get an advantage by destroying space.
"But people need to know this – you will not get an advantage over the United States by destroying space.
"And to the extent that we have a space force, it is to make sure that if we can convince people rightly and properly that they will not gain an advantage by destroying space, then they won't make those investments.
"That's the goal, so that space can be preserved for humanity, for science, for exploration, for commerce."
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US politicians have expressed concern about the threat posed by Chinese hackers targeting satellites.
In 2018 report, the Washington-based think tank, the Centre For Strategic and International Studies, warned that China is "arguably the fastest rising power in space" and has "made rapid progress in developing both its space and counter-space capabilities".
"The country tested direct-ascent weapons, on-orbit robotics, and remote proximity operations," the think tank said.
"Reports indicate that China is also developing and testing directed energy and jamming technologies."
In his interview with Sky News, Mr Bridenstine spoke about his focus on the Artemis mission to put American astronauts on the moon by 2024, and then eventually go on to Mars.
He said: "When we think about how we get to the moon, we've tried to get to the moon over and over again since the Apollo era, and it always fails.
"The question is why? It fails not because of the technical risk, it fails because of the political risk.
"So when a programme goes 15 years, then you have administration change, congress change, budgets change, priorities change, you never get to the end state.
"And so what the president has said is that we are going to accelerate the path, so we are going to go within five years, go and get it done… we retire the political risk by accelerating."
NASA's ambition is to put the first woman on the moon in 2024.
Asked if a female astronaut would be the first of her crew to step on the surface, Mr Bridenstine replied: "I would imagine that the next person we have walking on the moon will be a woman."
NASA is partnering closely with private industry, and believes that in the future there will be a space economy built on mining, tourism and research.
Mr Bridenstine was asked if he had considered that NASA could be paving the way for humans to make the same mistakes when it comes to natural resource exploitation in space as they have done on Earth.