In a jaw-dropping spectacle, the 322-foot-tall, the most powerful ever built for NASA, finally blasted off Wednesday with an eruption of white-hot fire and an earth-shaking roar, boosting an uncrewed Orion capsule on a long-awaited flight to the moon.
After multiple delays due to repeated hydrogen fuel leaks, ground system glitches, two hurricanes and back-to-back launch slips, the Space Launch System rocket's four main engines finally roared to life at 1:47 a.m. EST, followed a few seconds later by ignition of two strap-on solid-fuel boosters.
At that instant, four explosive bolts at the base of each booster detonated to free the SLS from its launch stand and the 5.7-million pound rocket leaped away from pad 39B, propelled skyward by 8.8 million pounds of thrust.
"Seven, six, five, core stage engine start, three, two one, booster ignition and liftoff of Artemis 1!" exclaimed NASA commentator Derrol Nail from the launch control center. "We rise together back to the moon and beyond!"
The launching came 43 minutes later than planned because of work to fix an intermittent leak in a hydrogen valve on the rocket's mobile launch platform and because of a glitch that briefly interrupted radar tracking data. But once the problems were resolved, the final 10 minutes of the countdown ticked off without a hitch and the SLS rocket finally blasted off on its oft-delayed maiden voyage.
The Boeing-managed rocket hit 70 miles an hour — straight up — in just seven seconds, a stirring spectacle not seen since the last shuttle launch in 2011. And as with the shuttle, the initial moments of liftoff occurred in eerie silence.
But moments later, a roaring wall of sound reached the nearest observers 4.2 miles from the launch pad, accompanied by ground-shaking earthquake-like tremors.
Briefly turning night into day as it consumed its propellants, lost weight and accelerated, the SLS put on a dazzling sky show, thrilling thousands of spaceport workers, area residents and tourists who stayed up late to take in the historic launching.
"Well, for once, I might be speechless," said Launch Director Charlie Blackwell-Thompson, addressing her team in the control room. "I have talked a lot about appreciating the moment you're in. This is your moment... You have earned your place in history.
"We are all part of something incredibly special, the first launch of Artemis. The first step in returning our country to the moon and on to Mars. What you have done today will inspire generations to come. So thank you, thank you for your resilience... The harder the climb, the better the view. We showed the Space Coast tonight what a beautiful view it is!"
While no one was on board for the rocket's maiden test flight, instrumented mannequins were strapped into the Orion capsule at the top of the SLS to record the vibrations, accelerations, sounds and other environmental factors real astronauts will experience during piloted flights to the moon.
Eclipsing even NASA's legendary Apollo Saturn 5 in raw power, the SLS's Northrop Grumman-built strap-on boosters burned through 5.5 tons of propellant per second propelling the rocket out of the dense lower atmosphere.
Two minutes and 10 seconds after launch, they burned out and fell away at an altitude of 27 miles, leaving the four Aerojet Rocketdyne RS-25 core stage engines to continue the ascent on their own, generating a combined 2 million pounds of thrust.
Firing for another six minutes, the RS-25 engines boosted the SLS to an altitude of about 87 miles before shutting down at a velocity of about 18,300 mph, putting the vehicle into an elliptical orbit with a high point, or apogee, of about 1,100 miles and a low point, or perigee, of just 20 miles or so.
At that point, the rocket's upper stage, carrying the Lockheed Martin-built Orion capsule and its European Space Agency-supplied service module, separated from the empty core stage and continued coasting up toward apogee.
Once there, about 53 minutes after liftoff, the engine powering the Interim Cryogenic Propulsion Stage, or ICPS, fired for about 23 seconds to raise the low point of the orbit from 20 miles to about 115.
Reaching that low point about 45 minutes later — one hour and 26 minutes after launch — the ICPS was programmed to fire its RL10B engine for a nail-biting 18 minutes, boosting the vehicle's velocity to about 22,600 mph, more than 10 times faster than a rifle bullet.
That's how fast a spacecraft has to go to break free of Earth's gravity, raising the apogee to a point in space where the moon will be in five days.
After separating from the ICPS, the Orion capsule will head for an 81-mile-high flyby of the moon Monday and then into a "distant retrograde orbit" carrying the spacecraft farther from Earth — 268,000 miles — than any previous human-rated spacecraft.
The flight is the first in a series of missions intended to establish a sustained presence on and around the moon with a lunar space station called Gateway and periodic landings near the south pole where ice deposits may be reachable in cold, permanently shadowed craters.
Future astronauts may be able to "mine" that ice if it's present and accessible, converting it into air, water and even rocket fuel to vastly reduce the cost of deep space exploration.
More generally, Artemis astronauts will carry out extended exploration and research to learn more about the moon's origin and evolution and test the hardware and procedures that will be necessary to eventually send astronauts to Mars.
The goal of the Artemis 1 mission is to put the Orion spacecraft through its paces, testing its solar power, propulsion, navigation and life support systems before a return to Earth October 11 and a 25,000-mph plunge back into the atmosphere that will subject its protective heat shield to a hellish 5,000 degrees.
Testing the heat shield and confirming it can protect astronauts returning from deep space is the No. 1 priority of the Artemis 1 mission, an objective that requires the SLS rocket to first send the capsule to the moon.
If all goes well with the Artemis 1 mission, NASA plans to launch a second SLS rocket in late 2024 to boost four astronauts on a looping free return trajectory around the moon before landing the first woman and the next man on the moon's surface near the south pole in the Artemis 3 mission.
That flight, targeted for launch in the 2025-26 timeframe, depends on the readiness of new spacesuits for NASA's moonwalkers and a lander being built by SpaceX that's based on the design of the company's reusable Starship rocket.
SpaceX is working on the lander under a $2.9 billion contract with NASA, but the company has provided little in the way of details or updates and it's not yet known when NASA and the California rocket builder will actually be ready for the Artemis 3 lunar landing mission.
But if the Artemis 1 test flight is successful, NASA can check off its requirement for a super-heavy-lift rocket to get the initial missions off the ground and on to the moon.
And it hasn't been easy.
The huge rocket was first rolled to the launch pad for a "wet dress-rehearsal" fueling test in March, some 244 days ago. But four attempts to fuel the vehicle were derailed by elusive hydrogen leaks and a series of unrelated problems with ground equipment.
More leaks derailed two launch tries in August and September. After on-pad repairs, a successful tanking test was finally carried out in mid September, but an approaching hurricane — Ian — forced NASA to forgo a third launch attempt and to instead haul the rocket back to the shelter of the Vehicle Assembly Building.
It was hauled back out to the pad November 3 and after riding out Hurricane Nicole on its seaside firing stand, NASA clear the rocket for a third launch try Wednesday. And this time around, for the first time in the Artemis 1 launch campaign, the countdown finally made it all the way to zero for the first time.
Congress ordered NASA to build the Space Launch System rocket in the wake of the space shuttle's 2011 retirement, requiring the agency to use left-over shuttle components and existing technology where possible in a bid to keep costs down.
But management miscues and technical problems led to delays and billions in cost overruns. According to NASA's Inspector General, the U.S. space agency "is projected to spend $93 billion on the Artemis (moon program) up to FY 2025."
"We also project the current production and operations cost of a single SLS/Orion system at $4.1 billion per launch for Artemis 1 through 4, although the Agency's ongoing initiatives aimed at increasing affordability seek to reduce that cost."
Among the causes listed as contributing to the SLS's astronomical price tag: the use of sole-source, cost-plus contracts "and the fact that except for the Orion capsule, its subsystems and the supporting launch facilities, all components are expendable and 'single use' unlike emerging commercial space flight systems."
In stark contrast to SpaceX's commitment to fully reusable rockets, everything but the Orion crew capsule is discarded after a single use. As SpaceX founder Musk likes to point out, that's like flying a 747 jumbo jet from New York to Los Angeles and then throwing the airplane away.
"That is a concern," Paul Martin, the NASA inspector general, said in an interview with CBS News. "This is an expendable, single-use system unlike some of the launch systems that are out there in the commercial side of the house, where there are multiple uses. This is a single-use system. And so the $4.1 billion per flight ... concerns us enough that in our reports, we said we see that as unsustainable."
But the SLS has two near-term advantages: flight-tested "human-rated" components and the ability to launch 30 to 50 tons to the moon in a single flight.
SpaceX's Super Heavy-Starship rocket, which SLS critics say is a more affordable option, is twice as powerful and is fully reusable.
But it hasn't flown yet and even when it does, it will require multiple Starship tanker flights to refuel the moon-bound spacecraft before it leaves Earth orbit. Robotically refueling such massive rockets in space with cryogenic propellants has never been attempted.
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