Artemis Moon rocket for second launch attempt

SLS rocket

SLS rocket

The US space agency will try again in the coming hours to launch its most powerful rocket to date.

Nasa was thwarted by a mix of technical and weather problems as it attempted to get the Artemis I lunar mission off Earth on Monday.

But the mood at Kennedy Space Center in Florida remains upbeat.

“We have to show up, we have to be ready and we have to see what the day brings,” Mike Sarafin, NASA’s Artemis mission manager, told reporters.

The attempt to launch the Space Launch System (SLS) rocket on Saturday is scheduled for the start of a two-hour window beginning at 14:17 local time (19:17 BST; 18:17 GMT).

The goal of the 100-meter-tall vehicle will be to hurl a human-grade capsule toward the moon, something that hasn’t happened since Project Apollo ended in 1972.

Artemis I is a technology demonstration, so there will be no crew on board for the occasion, but should the mission go according to plan, Artemis II, which is expected to fly in 2024, will most certainly be carrying people.

Nasa astronaut Jessica Mier said everyone should therefore be patient as the SLS moves towards its maiden flight and not be surprised if there is another postponement.

“Yes, of course it’s frustrating for everyone, but it’s not unexpected,” she told BBC News.

“It’s part of the way we operate at NASA. At some point the SLS will have people, my friends, my colleagues. So we have to make sure this test flight goes well.”

Graphics by SLS

Graphics by SLS

Monday’s offer to fly SLS was eventually scrubbed because air traffic controllers couldn’t be sure the four large engines under the rocket’s core stage were properly primed for flight.

The Shuttle-era thrusters are chilled to -240°C during the countdown to prevent them from being shocked by the sudden injection of cryogenic propellants on takeoff. But a sensor indicated that engine #3 was possibly 15 to 30 degrees below the temperature that was required.

However, Aerojet Rocketdyne’s Bill Muddle is confident the sensor was faulty and if it shows up again on Saturday it’s likely to just be ignored.

“After checking the data and all other indicators, engine #3 could have been even a bit colder than the others on Monday,” he said.

“We now understand what we need to look at to get comfortable with the launch.”

If the SLS gets away this time, it’s sure to be a spectacular sight.

“It’s going to be a ‘shuttle on steroids,'” said Doug Hurley, pilot of the very last shuttle mission in 2011.

The former astronaut now works for Northrop Grumman who make the big white solid boosters on the sides of the SLS.

“One of the coolest things I’ve always found about shuttle launches is you saw it take off and it was a long way from the tower before you heard anything, and then it took even a little bit longer before you felt it,” he explained.

“In terms of weight, SLS is pretty close to what Shuttle was. Apollo’s Saturn V rocket was drastically different. I never saw her in person, but she rumbled out of the pad. For Shuttle, it seemed like it was instantly clear almost as soon as the boosters were lit. SLS should be the same,” he told BBC News.

lunar route

lunar route

The first motorized phase of the SLS’s ascent will take just over eight minutes.

This puts the rocket’s upper stage, with the Orion capsule still attached, into a highly elliptical orbit where the two would plummet back to Earth without further effort.

So the upper stage must raise orbit and circularize before propelling Orion towards the moon.

Confirmation should come two hours and five minutes after launch that the capsule is self-sufficient and on course, hurtling through space at 30,000 km/h (19,000 mph).

The planned deployment time is just under 38 days. This would result in Orion returning to Earth on October 11 for a splashdown in the ocean off San Diego, California.

38 days is much longer than the 21 days that capsule maker Lockheed Martin claims is the maximum time astronauts should spend in the spacecraft.

But Annette Hasbrook, senior adviser to the Orion program at Nasa, said engineers wanted to expand the spacecraft on this mission to understand its limitations.

Artwork: Orion sent to the moon

Artwork: The rocket’s upper stage will carry the Orion capsule on its way to the moon

“You’re trying to test the edges of your boxes, not your nominal profile,” she explained.

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