Update 05/30, 4:00 p.m. Eastern: The Demo-2 mission successfully launched Saturday afternoon.

Update 05/27, 4:20 p.m. Eastern: The launch has been scrubbed due to adverse weather conditions. The next window is set for Saturday, May 30 at 3:22 p.m.

At 4:33 p.m. US Eastern Time today, NASA astronauts Bob Behnken and Doug Hurley are scheduled to launch into orbit for a rendezvous with the International Space Station. This is standard stuff, except for three important facts: it will be the first time in almost nine years that American astronauts have flown to space from American soil; it will be the first time in history astronauts have reached low Earth orbit on a commercially built rocket and spacecraft; and it will the first time in its 18-year history that SpaceX has launched humans into space.

The mission, called Demo-2, is set to take off from Kennedy Space Center in Florida. Behnken and Hurley will fly to the ISS aboard the SpaceX Crew Dragon, launched using the company’s flagship Falcon 9 rocket. The mission could last anywhere between 30 and 119 days, depending on the status of Crew Dragon and whether NASA needs the pair to stay longer to help out with operations on the station. The agency won’t make that decision until they are already in orbit. Regardless, 119 days is the maximum because Crew Dragon’s solar arrays are currently not designed to withstand degradation for longer than 120 days. 

The launch date for the follow-up Crew Dragon mission to the ISS, Crew-1, won’t be set until Demo-1 returns safely to Earth. That mission, which plans to take one Japanese and three American astronauts into space, will use a version of the capsule that’s designed to last 210 days in orbit. 

NASA has not launched humans into space from American soil since the space shuttle flew for the last time on July 21, 2011. The plan has always been for NASA to turn over its low-Earth-orbit missions to the private sector—first for cargo resupply missions to the ISS and then for astronaut flights themselves through the Commercial Crew Program (CCP). NASA gave massive contracts to Boeing and SpaceX to build the crew vehicles required—and hoped to have them up and running by 2017. 

In the interim, NASA has paid Russia more than $4 billion to take its astronauts to the ISS aboard Soyuz missions. But the timeline slipped, forcing NASA to shell out additional money for Soyuz tickets and at one point raising the strange possibility the ISS would be unoccupied for the first time in two decades. The financial burden and the cratering of US-Russian relations through the last decade put more pressure on NASA to end its reliance on Soyuz. A successful Demo-2 mission gives NASA a preferable new option for its human spaceflight program. 

SpaceX and Boeing have almost never been on schedule. Although SpaceX aced all its major tests, it experienced its most significant setback in April 2019, when a launchpad fire destroyed one of its Crew Dragon capsules just a month after the vehicle finished a successful uncrewed test flight. That explosion eventually pushed Demo-2 into 2020. The December test flight for Starliner, meanwhile, never even made it to the ISS because of one of many software glitches. Boeing will redo this mission later in the fall. 

Wednesday’s mission, nevertheless, is a big leap forward for both SpaceX and the commercial space industry. SpaceX CEO Elon Musk wants to send humans to Mars one day through its Starship vehicle and establish a sustainable interplanetary transportation system. Crew Dragon is the first step toward making SpaceX a human spaceflight company, and the vehicle itself is expected to run private astronaut and tourist missions in the coming years. If successful, Crew Dragon’s and Starliner’s inaugural crewed missions will demonstrate that private spaceflight is technically viable, although the companies will still have to make the business case. 

The Commercial Crew Program wasn’t simply a selfless act by NASA to open up opportunities to private industry; it was also a way to save money. In the space shuttle’s heyday, each mission cost nearly $1.8 billion (in 2020 dollars). Now NASA is paying SpaceX $55 million per astronaut for every Crew Dragon mission. A recent analysis by the Planetary Society estimates that NASA has invested just $6.6 billion to bring Crew Dragon and Starliner to the launchpad—much cheaper than what the agency likely would have spent developing its own vehicle for low-Earth-orbit transportation. Instead, NASA has focused its own resources on developing deep-space architecture for a return to the moon and eventual travel to Mars (that program is also far behind schedule).

There’s been a fair share of criticism directed at NASA’s and SpaceX’s decision to continue with Demo-2during the covid-19 pandemic. One of the most prominent voices was former NASA deputy administrator Lori Garver, who told The Atlantic in April: “I’m not sure risking so many lives to launch two people to the same place we’ve been going for 20 years should be prioritized.” 

With many of NASA’s projects slowed or outright halted by the pandemic, CCP has been one of the few programs continuing as regular business. Though the agency has minimized Behnken’s and Hurley’s contact with the outside world, the hundreds of NASA and SpaceX personnel required to launch the mission must still risk coronavirus exposure. NASA and SpaceX both say they are taking precautions to increase social distancing between people on site and having employees work in shifts to minimize contact. Spectators are being asked to stay home and watch the launch remotely. “No virus is stronger than the human desire to explore,” NASA administrator Jim Bridenstine tweeted in April. And Musk has publicly stated his opposition to lockdown measures, even reopening a Tesla factory in Fremont, California, in defiance of stay-at-home orders. If Demo-2 is delayed, it won’t be because of coronavirus.