An important test for NASA’s Space Launch System (SLS) is slated to get underway (again). Earlier this year, NASA assembled the Artemis 1 SLS rocket and transported it to the launch pad at Kennedy Space Center. However, issues with fans on the tower and a valve in the rocket itself delayed the “wet dress” rehearsal. Now, that test is getting back underway, with the all-important countdown slated for Thursday, reports Ars Technica.
NASA has been working on the SLS for more than a decade. The goal of the project was to create a launch vehicle that could lift heavy payloads and transport them farther out in the solar system. It’s also at the heart of NASA’s plans to return to the moon. Development was originally supposed to cost $18 billion with an initial launch in 2016. It has been delayed at least 16 times, and the cost has crept over $21 billion between 2011 and 2021.
A wet dress involves fully fueling the vehicle and running the countdown as if you were going to launch the rocket. However, NASA will abort the countdown at T-10 seconds. There are around 25 “critical events” that take place before that, giving NASA insights into how well the SLS is operating. However, this isn’t the same wet dress NASA was hoping to put on.
In early April, the agency paused the test because of issues with the launch tower. Last week, NASA filled the core stage about halfway with liquid oxygen before discovering a manual vent valve was left in the wrong position. And then it spotted a stuck check valve in the upper stage. Due to the valve issue in the upper stage, known as the Cryogenic Propulsion Stage, NASA will skip fueling this part of the vehicle. Luckily, only two of those critical events are connected to the upper stage. The upper stage was completed by United Launch Alliance four years ago, far ahead of most of the vehicle. However, NASA does not believe the delays are to blame as the valve is rated to last for 20 years or more.
Thus, NASA feels confident it can proceed with the wet dress after just fueling the core stage. It plans to begin that process on Tuesday evening (April 12), marking the third time it has pumped fuel into the SLS. It’s unclear if NASA will conduct a second wet dress rehearsal with both stages fueled, but any additional delays will most likely push back the latest June 2022 launch window. When it does launch, Artemis 1 will send an uncrewed Orion capsule around the moon and back to Earth. The Artemis missions won’t be cheap. NASA estimated about $2 billion per launch, but a government report said the true cost is probably closer to $4 billion. Both of which are much more than SpaceX expects to spend on Starship launches in the next few years. That’s thanks in large part to the SLS being an expendable vehicle—you get one launch, and then you have to build another.
NASA has an ambitious timeline set up for Artemis 1 through Artemis 5, with more missions possible beyond that. In just a few days, we’ll have a better idea of whether or not NASA will have to delay it all again.