NASA astronaut Megan McArthur's warning to space tourists: Spaceflight is uncomfortable and risky. It takes grit.

• NASA astronaut Megan McArthur has a message for future space tourists: Spaceflight is uncomfortable, risky, and requires grit.
• A civilian crew is set to fly on SpaceX's Crew Dragon next month.

NASA astronaut Megan McArthur has a word of warning for future space tourists: orbiting Earth isn't all fun and games.

Well, some of it is. But the awe-inspiring experience of spaceflight comes with plenty of discomfort, risk, and difficulty executing everyday tasks.

Living in microgravity is "sort of like having superpowers," McArthur told Insider in a recent call from the International Space Station (ISS). "I can lift things that, on Earth, I would need two or three people to help me lift."

But she added: "Things that are very, very simple on Earth suddenly become really hard - even something simple like sleeping or brushing your teeth. You have to really think about: How am I going to do this successfully and without making a mess?"

Astronauts have to swallow their toothpaste because spitting it out would leave liquid floating around. They sleep in little compartments about the size of a telephone booth, inside a sleeping bag secured to the wall so they don't float around. The sleeping booths have air vents so that bubbles of carbon dioxide don't form around the astronauts' heads.

Several companies are now selling spaceflights to the wealthy. At least two crews of tourists are set to launch aboard SpaceX's Crew Dragon spaceship in the next six months, and they are training to prepare for the discomforts of spaceflight. But only professional astronauts like McArthur really know what that's like.

Astronauts can't do laundry. And they can't shower. Instead they have to sponge-bathe using a soapy water solution in a bag, and use no-rinse shampoo to clean their hair. To go to the bathroom, they pee into a funnel and poop into a small hole, both of which suction waste away so it doesn't float around the station.

That's why some astronauts compare spaceflight to a rugged camping trip. But of course, it's far more extreme and risky than that.

"I think it's a little bit like other exploring that people have done over the generations," McArthur said. "You have to be willing to put up with a little discomfort and some risk, obviously. So you have to have grit, I think, in your personality to help you get through those things and enjoy those situations."

About 1% of US human spaceflights has resulted in a fatal accident, according to an analysis published earlier this year. That's about 10,000 times more dangerous than flying on a commercial airplane. It's unclear, though, how that failure rate will change as new, commercially developed spacecraft begin flying people regularly.

One crew of future space tourists is getting 'comfortable being uncomfortable'

Since 2001, several millionaires and billionaires have paid for seats to the ISS aboard Russia's Soyuz spacecraft. But now, private companies with their own rockets and spaceships are opening up a new industry of space tourism.

Last month, Richard Branson and Jeff Bezos each skimmed the edge of space aboard vehicles developed by the companies they founded - Virgin Galactic and Blue Origin, respectively. Both companies are selling tickets for such suborbital flights.

The next tourists to go to space are due to launch next month aboard SpaceX's Crew Dragon spaceship - the same model that flew McArthur to the ISS in April. They plan to orbit Earth for three days.

Billionaire Jared Isaacman chartered the flight, called Inspiration4, from SpaceX. He's taking one seat and giving the other three to physician-assistant Hayley Arceneaux, Air Force vet and engineer Chris Sembroski, and scientist and analogue astronaut Dr. Sian Proctor.

To help prepare, part of their training involved an icy climb to the top of Mount Rainier in Washington.

"They built some mental toughness. They got comfortable being uncomfortable, which is pretty important," Isaacman told Insider. "Food sucks on the mountain. Temperatures can suck on the mountain. Well, that's no different than Dragon. We don't get to dial up and down the thermostat ... And I can tell you the food isn't great in space, from what we've tasted so far."

In January, another group of tourists is set to fly on a Crew Dragon - the exact ship that McArthur rode to space, which will be reused for the mission. The flight, called AX-1, is the first tourist flight by the company Axiom Space, which aims to eventually build a private space station.

The AX-1 crew includes real-estate investor Larry Connor, Canadian investor Mark Pathy, and former Israeli fighter pilot Eytan Stibbe. Axiom Space's vice president, former NASA astronaut Michael López-Alegría, will command the mission. The team is set to dock to the ISS and stay there for eight days.

Elon Musk, who founded SpaceX in 2002, wants to eventually create a self-sustaining human colony on Mars. Bezos also wants to see off-planet colonies, which is why he founded Blue Origin in 2000. NASA, meanwhile, has long-term plans to establish a permanent human presence on the moon, then on Mars.

McArthur said even living in space relatively close to home is very difficult and risky, even with years of NASA training and previous spaceflight experience.

"I kind of knew what to expect. But then actually getting to live it was still really fun and really exciting and really challenging as well," she said. "As much as you prepare, the day-to-day life can still be very challenging."