NASA astronauts Doug Hurley, left, and Bob Behnken work with teams from NASA and SpaceX to rehearse crew extraction.

NASA astronauts Doug Hurley and Bob Behnken will be the first spacefarers to launch to orbit on a privately built rocket.Credit: Bill Ingalls/AP/Shutterstock

Update 31 May: SpaceX’s Crew Dragon lifted off successfully at 3.22 p.m. US Eastern time on 30 May. It docked with the International Space Station on 31 May.

On Wednesday, if the weather in Florida cooperates, two NASA astronauts plan to strap themselves into a capsule atop a SpaceX rocket and travel to space. If the launch succeeds, it will mark a number of firsts in human spaceflight. It will be the first time a private company has flown humans to orbit, and the first time astronauts have launched from US soil since NASA retired the Space Shuttle in 2011.

Perhaps most significantly, it is the first time in 17 years that anyone has launched a new type of spaceship to carry humans to Earth orbit (see ‘How humans have reached orbit’). “This is a whole new way of sending people to space,” says Robert Cabana, a former NASA astronaut who is now director of the Kennedy Space Center in Florida.

If all goes well, astronauts Robert Behnken and Douglas Hurley will fly the spaceship, called Crew Dragon, to the International Space Station (ISS). Roughly 19 hours after launch, they will dock with the space station, then float inside to join three spacefarers who have been living and working there since April.

Mission controllers are watching the weather carefully to see if conditions are good enough to launch on Wednesday. If not, the next two available launch opportunities are 30 and 31 May.

Commercial flight

The flight is the culmination of NASA’s long-running push to transition from using its own vehicles to ferry astronauts to the space station to using spaceships provided by private companies. Since 2011, NASA — like all other space agencies — has had to rely on Russian Soyuz craft, originally designed in the 1960s, to take people to orbit. But if the SpaceX test flight goes as planned, the agency will begin using Crew Dragon to transport astronauts to and from the ISS.

Timelines showing number of spaceships used to carry humans into orbit

Data source: Jonathan McDowell

SpaceX, of Hawthorne, California, has been in the vanguard of private spaceflight, and has been taking cargo to and from the ISS since 2012. It is the first of two companies chosen by NASA to conduct a crewed test flight, and jumped ahead in the race to carry humans by using the same basic spacecraft design it has been using to make the cargo runs. This week’s flight just adds astronauts. Its competitor — Boeing, based in Chicago, Illinois — is further behind. Boeing’s spaceship, called Starliner, spent two days in Earth orbit without a crew in December and encountered several problems, including a crucial timing error in its software. Starliner will do another uncrewed test flight in the coming months and is not likely to fly astronauts until next year.

Bullet capsule

Crew Dragon is an 8.1-metre-long, 4-metre-wide bullet-shaped capsule, roughly similar to the Apollo capsules that carried NASA astronauts to the Moon between 1969 and 1972. Crew Dragon can carry up to four people for NASA missions. It will launch on one of SpaceX’s Falcon 9 rockets, which have slashed the cost of getting satellites to space, in part because they reuse expensive components such as rocket boosters. NASA is thought to be paying around US$60 million for each seat on the Crew Dragon, compared with the $90 million it has been paying the Russian space agency for seats aboard the Soyuz.

The first crewed flight of any new spacecraft is always nail-biting, given that astronauts have died during missions. Behnken and Hurley are former US military test pilots and veteran astronauts who each flew twice on the Space Shuttle. (They are also both married to other astronauts.) In a 1 May briefing with reporters, both said they felt that flying aboard Crew Dragon was less risky than flying on the shuttle, which resembled a large space aeroplane. “The capsule design is generally safer than a winged vehicle,” said Hurley. For instance, if something goes wrong aboard Crew Dragon, the astronauts have more chances to abort the mission than they would on the shuttle — if something goes wrong soon after launch, they can fire eight special engines to manoeuvre the capsule away from the Falcon 9 rocket, deploy parachutes and splash down in the ocean.

The SpaceX Crew Dragon spacecraft undergoes final processing at Cape Canaveral Air Force Station, Florida.

The SpaceX Crew Dragon spacecraft will be launched to the International Space Station on a Falcon 9 rocket.Credit: SpaceX

If they reach the space station safely, the astronauts will live and work there for one to four months. Among other tasks, they will help with the various research projects being conducted on the station, including experiments on how flames burn and plants drink water in space. In January, astronauts Christina Koch and Jessica Meir installed a major upgrade to a cold-atom laboratory on the station, which chills clouds of atoms to just above absolute zero to see how they behave in near-zero gravity. Koch and Meir were “indispensable” in pulling off the eight-day upgrade of the experiment, says Kamal Oudrhiri, the project’s manager at the Jet Propulsion Laboratory in Pasadena, California — showing that astronauts can make critical contributions to science in orbit.

Extraordinary circumstances

Because of the COVID-19 pandemic, Wednesday’s historic launch will be unlike any that has ever departed from Florida’s storied space centre. NASA is warning members of the public to stay away and watch the launch online, rather than crowd onto nearby beaches as they typically do. When Behnken and Hurley arrived at the Cape on 20 May, they were greeted on the runway by NASA’s administrator, Jim Bridenstine — who stood well over 2 metres away from them, practising social distancing. As usual, the astronauts are in an extended quarantine before launch, so as to not carry any pathogens up to the space station.

After this launch, NASA’s attention will turn back to its aim of returning astronauts to the Moon by the end of 2024.

That goal is looking less feasible as time goes on. NASA has begun buying some of the services needed; for example, it has contracted companies to develop landers that could carry astronauts from lunar orbit to the lunar surface. But the person in charge of the landing strategy resigned on 19 May. Doug Loverro, who had served as head of NASA’s human-spaceflight programme for just seven months, cited an unspecified “mistake” he had made in trying to drive the agency towards its lunar-landing dream.

Former astronaut Ken Bowersox is taking over for now — putting him in the hot seat during NASA’s most important crewed launch in years.