Elon Musk’s SpaceX to launch fourth mission to ISS on Wednesday - The Washington...

It’s not. Gravity remains a tremendous force to overcome. Rockets are still powered by thousands of gallons of highly combustible propellants. And the vacuum of space is as harsh and dangerous as ever.

As NASA and SpaceX prepare to send their fourth crew of astronauts to the International Space Station, the teams are driving home that message, saying they are prepared but daunted by what they know is a tremendously risky endeavor. And along the way they have faced a series of challenges, including a leaky toilet.

If all goes to plan, three NASA astronauts and a European astronaut will blast off on a SpaceX Falcon 9 rocket from the Kennedy Space Center in Florida at 1:10 a.m. Wednesday. (The mission was originally scheduled to launch at 2:21 a.m. Sunday, but NASA announced Saturday it was postponing the flight because of high winds and heavy seas in the abort areas.)

The mission would be the third time Elon Musk’s SpaceX has launched a full contingent of astronauts to the station, in addition to some two dozen cargo missions and a test flight with a pair of NASA astronauts in May 2020. It also flew a crew of private citizens for three days in orbit last month in what was known as the Inspiration4 mission.

Despite the regular cadence of flights, officials at NASA and SpaceX say they are still very much in the learning stages and know that small problems on a rocket fueled with thousands of gallons of combustible propellants can lead to big problems.

“We just have to continue to really be responsible and really be thoughtful,” Holly Ridings, NASA chief flight director, said during a preflight news conference this week. “We have this great partnership with SpaceX, and we’ve done this a couple of times now — not enough to really say we’re good at it.” The fact is, she said, “we’re still learning a lot.”

After every flight, engineers scour the rocket and the spacecraft, looking for weaknesses that could be made stronger, studying ways to make the spacecraft safer and better.

Over the course of the program that has led to a number of changes, from new parachutes that slow down the capsule for a water landing, to reinforcements to the heat shield. Now, SpaceX has been giving its attention to another part of the Dragon capsule: the toilet.

On SpaceX’s Inspiration4 mission there was a problem with the toilet. After the spacecraft landed, engineers studied it and discovered that a tube that funnels urine into a storage tank had become unglued, Bill Gerstenmaier, SpaceX’s vice president of build and flight reliability, said during the news conference.

“It had no impact on Inspiration4 at all,” he said. “We didn’t really even notice it, the crew didn’t notice it, until we got the vehicle back and we looked under the floor and we saw the fact that there was contamination underneath the floor.”

SpaceX engineers fixed the problem by welding the tube in place. But there was some concern the problem could plague the Dragon capsule used in an earlier flight that is currently attached to the space station and set to fly a quartet of astronauts home next month.

Gerstenmaier said there was a concern that a compound known as oxone, used to remove ammonia from urine, could cause corrosion in the vehicle. As a result, he said, crews on the ground “did extensive tests where we took aluminum samples, and we placed an oxone-urine mixture on them. And then we put them in a chamber that mimics the humidity and temperature conditions onboard [the] space station.”

The corrosion, he said, was limited because of the low-humidity environment, and the aluminum alloy used in the spacecraft is resistant to corrosion. Still, he said, engineers “will double-check things, we’ll triple-check some things … and we’ll be ready to go and make sure the crew is safe to return.”

The toilet issue is an example, officials from NASA and SpaceX said, of the benefits of being able to reuse the hardware, inspect it and improve it for future missions.

“What we’re looking for is tiny clues or tiny imperfections,” said Steve Stich, NASA’s commercial crew program manager. “You really just try to dig into all those sorts of things and try to understand those and then improve things and fly safely.”

The astronauts set to blast off Wednesday and spend 22 hours in the capsule before docking with the station said they were glad the toilet was fixed and that NASA and SpaceX continue to study the rocket and spacecraft after each flight.

“We have complete confidence,” said NASA astronaut Raja Chari, who is the commander of this weekend’s mission. “SpaceX, as they have in the past, has been amazingly quick and reactive. When they find something, they immediately come up with a fix and move out on implementation.”

The crew is vastly different in experience than many of the people who have recently been flying to space. Richard Branson’s Virgin Galactic and Jeff Bezos’ Blue Origin have been flying private citizens on suborbital trips to the edge of space and back. (Bezos owns The Washington Post.) A Russian actress and movie producer recently returned after shooting scenes for a movie on the station. SpaceX flew the crew of Inspiration4, a mission funded by billionaire entrepreneur Jared Isaacman, and the company has more private astronaut missions planned as well.

The astronauts on the upcoming mission, known as Crew-3, by contrast, are highly trained professionals.

Chari, an Air Force colonel and a test pilot, will be joined on the Crew-3 flight by Kayla Barron, a Navy lieutenant commander who served on a nuclear submarine, Tom Marshburn, a physician who has flown to space twice before, once on the space shuttle and once on the Russia Soyuz, and European astronaut Matthias Maurer, an engineer from Germany.