NASA is aiming to launch its new monster rocket, the Space Launch System, on its first trip to deep space as early as late August, the agency announced today. NASA says it has placeholder dates for August 29th, September 2nd, and September 5th for the rocket’s debut, though there is still plenty of work left to do on the vehicle between now and then.

The Space Launch System, or SLS, is a major component of NASA’s Artemis program, the agency’s initiative to send humans back to the Moon. Designed to carry NASA’s Orion crew capsule into deep space, the rocket is slated to perform a series of missions over the next few years that should eventually culminate with astronauts landing on the lunar surface again. But first, NASA wants to see it fly without a crew on board, sending an empty Orion capsule around the Moon.

NASA officials stressed that they are not committing to any of these dates at the moment, but the announcement puts the rocket closer than it’s ever been to its launch. The SLS has been in development for roughly a decade, and its inaugural launch date has been an ever-moving target. NASA originally planned to launch as early as 2017, but schedule delays, development mishaps, and poor management have caused the rocket’s debut to slip again and again.

But after conducting a mostly full dress rehearsal with the rocket back in June, NASA is in the development end game, and an actual launch looms on the horizon. A more solid launch date should come closer to actual liftoff. “We’ll make the agency commitment at the flight readiness review, just a little over a week before launch,” NASA’s Jim Free, associate administrator for exploration systems development, said during a press conference. “But these are the dates that the team is working to and have a plan to.”

After the dress rehearsal, which saw the SLS fully loaded with its propellants for the first time, NASA rolled the rocket back into the massive Vehicle Assembly Building (VAB) at NASA’s Kennedy Space Center. Since then, engineers have been fixing some of the issues that cropped up during the dress rehearsal, such as a hydrogen leak that ultimately prevented the mission team from completing the test like they wanted. There are other tasks on the to-do list ahead of launch, but for now, the tentative plan would be to roll the SLS back out of the VAB on August 18th ahead of the first launch attempt on August 29th.

Depending on which day the SLS launches, each date would have a different liftoff time and mission duration. Here’s what to expect for each date:

• August 29th: A two-hour launch window opens at 8:33AM ET. The mission would last 42 days, with Orion splashing down in the ocean on October 10th.
• September 2nd: A two-hour launch window opens at 12:48PM ET. The mission would last 39 days, with Orion splashing down in the ocean on October 11th.
• September 5th: A one-and-a-half-hour launch window opens at 5:12PM ET. The mission would last 42 days, with Orion splashing down in the ocean on October 17th.

If NASA doesn’t meet these dates, the next window to launch opens in late September. The windows are dictated by the position of the Moon in relation to the Earth so that SLS can successfully get into the proper path around the Moon, and they must allow for the Orion crew capsule to be illuminated by the Sun for most of the flight, so it can get enough rays on its solar panels. NASA has a list of all the windows, as well as the criteria for them, here.

If NASA rolls out SLS to the launchpad in mid-August but cannot launch by September 5th, then the rocket’s liftoff could see a significant delay. It all has to do with the SLS’s flight termination system, which is used to destroy the rocket if something goes catastrophically wrong during the launch and the vehicle starts to veer off course. Teams must fully test the flight termination system before launch, and that work can only be done inside the VAB. Once the SLS is rolled out from the VAB, there is a 20-day time limit for the flight termination system before it has to be tested again. That means the rocket has to launch within 20 days of its rollout, or it must be returned to the VAB so that the flight termination system can get checked out again.

That testing takes time, so if SLS is forced to come back to the VAB after rolling out in August, chances are it wouldn’t be ready to fly until late October. “There is the possibility with that, that we could potentially hit the [late September] launch period,” Cliff Lanham, senior vehicle operations manager for exploration ground systems at NASA’s Kennedy Space Center, said during the press conference. “But that would be a real challenge for us, I’ll be honest with you. But we would certainly give it our best shot at that point.”

The timeline could still certainly shift in the coming weeks. But for now, NASA has some semblance of a schedule for SLS’s launch, and this rocket may actually see space this year.