Nasa has begun a second attempt at a crucial test of its new Moon rocket, powering up the launch vehicle ahead of a modified launchpad fueling test scheduled for later this week.
The space agency is aiming to conduct the test on Thursday after being forced to cut short an earlier attempt at the test, known as a “wet dress rehearsal,” on 4 April due to a technical issue that prevented them from fully fueling the Space Launch System, or SLS rocket.
A wet dress rehearsal involves loading a rocket with cryogenic fuel as well as simulating a launch countdown, testing communications links, and other assessments before an actual launch.
In the aftermath of the 4 April test, Nasa technicians found a faulty valve managing helium gas pressure in the rocket’s upper stage needing replacement. The SLS rocket and Orion spacecraft at its top are the cornerstones of Nasa’s Artemis program, which aims to return humans to the Moon in 2025.
“We are looking at doing a modified wet dress rehearsal, which involves loading and draining propellant on the core stage, getting into our terminal count operations, and then doing some chill down operations on the upper stage,” Nasa Artemis launch director Charlie Blackwell- Thompson said.
“We believe that we’ll be able to meet the majority of our test objectives and provide us with a really good set of data.”
In a media call on Monday, Nasa officials said that since they cannot replace the valve while the rocket remained on the launch pad, Thursday’s test will proceed without loading propellant into the rocket’s upper stage before rolling the rocket back into the Vehicle Assembly Building at Kennedy Space Center to address the valve issue.
Nasa first rolled the 322-foot-tall SLS rocket to the Kennedy Space Center launch complex 39B on 17 March, intending to begin the wet dress rehearsal on 1 April.
Severe weather bumped the start of the test until 3 April, but then problems with two fans on the mobile launcher used to prevent the leakage of volatile gases led Nasa to wait another day to begin testing.
Nasa proceeded with the wet dress rehearsal, or “wet dress,” as Nasa officials call it, on 4 April, but only loaded the SLS with about 50 per cent of the required liquid oxygen during the fueling test before a pressure control valve on the mobile launcher malfunctioned, leading them to end the test and empty the rocket of propellant.
In the aftermath of the halted 4 April wet dress rehearsal, Nasa’s ground team discovered the second faulty valve, a “check valve” intended to keep helium from flowing back out of pressurized containers in the SLS rocket’s upper stage. The upper stage, known as the Space Launch System Interim Cryogenic Propulsion Stage or ICPS, is a modified version of the proven United Launch Alliance’s Delta IV rocket upper stage that will only fire its single engine once in orbit.
Despite the run of issues, Nasa officials said the problems they’ve encountered so far are relatively minor and manageable.
“The mega Moon rocket is in a great shape,” said Nasa deputy associate administrator for common exploration systems development Tom Whitmeyer.
“We’re treating it very carefully, and therefore we’re going to limit a few of the objectives that are coming up on Thursday.”
Asked to clarify what objectives Nasa will not be a blessing to fulfill on Thursday, Ms Blackwell-Thompson noted only a handful of the more than 100 checklist items that cannot be accomplished, primarily the loading of propellant into the ICPS, certain portions of the simulated launch countdown and some communications between the ICPS and ground controls.
But given that even if Thursday’s test goes well, it will come two weeks after Nasa planned to complete the wet dress rehearsal, it’s not clear if the delay will affect the scheduling of the first SLS test flight.
Nasa plans to go to the Moon in 2025 using SLS and Orion in the Artemis III mission, following a crewed lunar orbiting mission in May 2024, Artemis II.
NASA had hoped to launch the first uncrewed test flight for SLS, Artemis I, as early as sometime in May. However, during Monday’s call with reporters, Artemis mission manager Mike Sarafin suggested the space agency is already looking out as far as late July or early August for potential launch dates for the test flight.