NASA testing giant rocket for next Moon mission

NASA was preparing for a key test of its troubled Space Launch System (SLS) rocket on Thursday as the agency prepares to return to the Moon.

The second "hot fire" test will see all four of the rocket's RS-25 engines fire simultaneously and achieve a maximum of 1.6 million pounds of thrust (7.1 million newtons).

A two-hour window for the test begins at 3:00 pm Eastern time (1900 GMT).

It will be the second such test involving the 212-foot (65 meters) high core stage at the Stennis Space Center near Bay St. Louis, Mississippi, after the first was cut short in January.

NASA released a statement following that test that said "no major repairs" were required after the engines were cut just one minute into the eight-minute run, but did not detail what went wrong.

Thursday's test should also last eight minutes, and is intended to provide data that will help minimize risk on the lunar missions.

If all goes well, it will take about a month to refurbish the core stage, then it will be transported by barrage to the Kennedy Space Center in Florida.

There, it will be assembled with the other parts of the SLS rocket and the Orion crew capsule, which are being prepared for the Artemis I launch later this year -- an uncrewed mission.

The SLS program has been beset by delays and cost overruns, and was initially due to launch in 2016.

Ars Technica reported this week NASA was conducting an internal review of its affordability.

NASA said last August the baseline development cost was $9.1 billion and the initial ground systems capability required $2.4 billion.

It has also been criticized as a "jobs program" for NASA's Marshall Space Flight Center as well as its key contractors Boeing, Aerojet Rocketdyne, and Northrop Grumman.

While SLS is far more powerful than SpaceX's Falcon Heavy rocket used to put satellites in orbit and take crews to the ISS, Musk's company is also working on a prototype rocket called Starship that will be capable of deep space exploration.

Starship's last three test flights have ended in stunning explosions, but analysts believe the mishaps could paradoxically be accelerating the spaceship's development, eventually making it a viable alternative to SLS.