NASA officials admitted today the Space Launch System — the agency’s next big rocket — is a vehicle without a mission plan, NASA Spaceflight reports. The agency acknowledged what is essentially an empty flight manifest for the SLS at NASA's Kennedy Space Center (KSC) in Florida, during an all-hands meeting on Monday.

The meeting was held to discuss uncertainty about the SLS. Its first test flight with humans aboard has already been delayed once, and the schedule for the SLS’s tests are shaky — there is no definitive launch schedule for the rocket beyond its first uncrewed test flight, which is slated for September 30th, 2018. After that, the SLS's next flight dates are mostly tentative, and the rocket doesn't have any definitive mission plans — only the promise of going to an asteroid and then to Mars someday.

The SLS was born out of NASA's now-defunct Constellation program, an effort aimed at returning humans to the Moon. Though it was once considered the replacement for the Space Shuttle program, the group far exceeded its budget. President Obama cancelled the initiative in 2010, and out of its ashes, the SLS concept was created — both as a way to salvage parts of Constellation and to provide NASA with a primary vehicle for sending astronauts deep into space. It was also a way to save the jobs of thousands of NASA employees who had been working on Constellation.

But the SLS is expensive, and NASA's budget is at the lowest it has been in decades, even with the new budget allotment of $19.3 billion for the 2016 fiscal year. The cost of developing the SLS through 2017 is expected to total $18 billion. And once the rocket is built, each launch is going to cost somewhere between $500 and $700 million, which makes it unlikely that the rocket will carry astronauts more than once a year.

It's uncertain when the SLS will actually fly with people in it, though. A test flight of the rocket, which will send people into orbit around the Moon, was originally planned for no later than August 2021; that was pushed back to April 2023. Follow-up test flights are set for the mid to late 2020s, but no dates have been locked down yet. During the KSC meeting, two NASA administrators blamed NASA’s funding for the lack of SLS bookings, NASA Spaceflight reports.

There are actually two versions of the rocket, which has added to the scheduling and funding complexity. The first version of the SLS will debut with a smaller upper stage, or top portion of the vehicle; that's going to be used for the first uncrewed test flight in 2018. This version was also meant to be used for the first crewed flight in 2023. But NASA has been given more money to accelerate the production of a bigger upper stage for the SLS; now the agency wants to fly that bigger version before people can ride. That means the first crewed test flight will likely be pushed back yet again — becoming the third flight of the SLS rather than the second. The second flight will likely include a mission to Jupiter's moon Europa, as mandated in the new Omnibus bill.

After that, the SLS's future is unclear. The current objectives of NASA are to use SLS to conduct the Asteroid Redirect Mission — an initiative to bring a piece of an asteroid into lunar orbit where it can be explored by astronauts. Then there's the ultimate goal of a Mars mission in the 2030s. But the near term is more mundane: scheduling hell.

Updated January 13th, 8:21 AM ET: Added information regarding NASA's planned Europa mission.