Nasa postpones maiden flight of Moon rocket over engine problem

KENNEDY SPACE CENTRE (Florida) • An engine problem forced Nasa yesterday to postpone for at least four days the launch of its colossal next-generation rocketship on a long-awaited debut test flight around the Moon and back, 50 years after Apollo's last lunar mission.

The countdown was halted about 40 minutes before launch time as the 32-storey-tall, two-stage Space Launch System (SLS) rocket and its Orion crew capsule awaited liftoff from the Kennedy Space Centre in Cape Canaveral, Florida.

The countdown, which started last Saturday, continued smoothly through early yesterday when the threat of nearby thunderstorms caused a 45-minute delay to the adding of 700,000 gallons of liquid hydrogen and liquid oxygen into the rocket's propellant tanks.

The filling of the liquid oxygen tank proceeded without problems, but for the liquid hydrogen, a leak was detected in a fuel line attached to the bottom of the rocket.

That was a recurrence of a problem that occurred during a practice countdown in April.

Engineers were able to fix that problem and the filling of the hydrogen tank resumed. The hydrogen issue that arose later in the countdown was a different one.

In the last seconds of the launch countdown, some of the liquid hydrogen and liquid oxygen is diverted to flow around the four engines to cool them in preparation for ignition.

When done earlier in the morning, the oxygen lines all worked, as did three of the hydrogen lines. But the fourth hydrogen line did not fully open.

This was the first test of the engine chill down, which usually occurs in the final seconds before launch.

Mission engineers struggled to properly condition that engine to the right temperature for launch, the agency said.

Nasa did not give a new launch date, but said its first available backup launch opportunity was set for Friday.

Whether the agency sticks with that date depends on how quickly engineers can resolve the engine issue. The subsequent launch opportunity is Sept 5.

The maiden journey of the SLS-Orion marks the kickoff of Nasa's highly vaunted Moon-to-Mars Artemis programme, the successor to the Apollo lunar missions of the 1960s and 1970s.

The voyage is intended to put the 2.6 million-kg vehicle through its paces in a rigorous demonstration flight, pushing its design limits, before Nasa deems it reliable enough to carry astronauts in a subsequent flight targeted for 2024.

Billed as the most powerful, complex rocket in the world, the SLS represents the biggest new vertical launch system the US space agency has built since the Saturn V rocket flown during Apollo, which grew out of the US-Soviet space race of the Cold War era.

If the first two Artemis missions succeed, Nasa is aiming to land astronauts back on the Moon, including the first woman, as early as 2025, though many experts believe that timeframe is likely to slip by a few years.

The last humans to walk on the Moon were the two-man descent team of Apollo 17 in 1972, following in the footsteps of 10 other astronauts during five earlier missions beginning with Apollo 11 in 1969.

The Artemis programme seeks to eventually establish a long-term lunar base as a stepping stone to even more ambitious astronaut voyages to Mars, a goal that Nasa said will probably take until at least the late 2030s to achieve.

SLS has been under development for more than a decade, with years of delays and cost overruns.

REUTERS, NYTIMES