Nasa to practise Moon rocket countdown

Nasa has begun its second stab at loading its mega Moon rocket with cryogenic propellant, a crucial step before a test flight scheduled for later this summer

Nasa’s Space Launch System Moon rocket at dawn on 4 April 2022, prior to a “wet dress rehearsal” for launch (Nasa)

Nasa is practising fueling its big Moon rocket and plans to conduct a simulated launch countdown with T-minus zero in the count set for 3:57 p.m. Thursday.

Known as a “wet dress rehearsal” for launch, the multiple tests Nasa is conducting are crucial for the Space Launch System (SLS) rocket and the Orion spacecraft, which the space agency hopes will carry astronauts to the Moon in 2025 as part of its Artemis program.

Artemis I, the first uncrewed test flight of SLS and Orion, could happen as soon as June or July, depending on the results of the wet dress rehearsal.

Nasa began the “chill down,” or cooling of propellant lines into the core stage of the SLS rocket around 9 a.m. Eastern, according to a Nasa blog, preparing the lines and the rocket’s tank to receive 196,000 gallons of liquid oxygen at minus 297 degrees Fahrenheit, 147 degrees Celsius. Following the liquid oxygen loading, if all goes well, Nasa ground teams will then pump 537,000 gallons of liquid hydrogen into the rocket’s core stage before running the simulated launch countdown and performing other tests.

What Nasa won’t do is fill the SLS upper stage with cryogenic propellant, due to a malfunctioning pressure valve.

Nasa first rolled SLS from the massive Vehicle Assembly Building at Kennedy Space Center to launch complex 39B on 17 March, intending to begin the wet dress rehearsal on 1 April. But bad weather delayed the test until 3 April, when malfunctioning fans on the launch platform delayed the test again.

On 4 April, Nasa began loading liquid oxygen into SLS, but only got halfway through the process before a malfunctioning valve on the launch platform forced them to cut the test short. Another, different malfunctioning valve in the rocket’s upper stage, one managing the flow of inert helium, was discovered shortly after the aborted 4 April test.

In a Monday press conference, Nasa officials said they would have to return the SLS to the Vehicle Assembly building to replace the helium valve, but would first proceed with a modified wet dress rehearsal, loading only the rocket’s core stage with propellant. Officials said they will still glean most of the information they wanted from the modified test but will consider whether another wet dress rehearsal is required after completing Thursday’s tests.

The results of the test will also determine when Nasa finally launches the uncrewed Artemis I test flight, which will see the rocket power the Orion spacecraft to the Moon and back. A successful Artemis I flight will in turn pave the way for a crewed Artemis II mission in May 2024, where astronauts will orbit the Moon and return to Earth.

Artemis III, scheduled for 2025, will land two astronauts, including the first woman, on the Moon’s southern polar region. If Nasa reaches all of those milestones as scheduled, the Artemis program then plans to target one human mission to the Moon per year beginning in 2027.