The countdown for the launch of NASA’s Space Launch System (SLS) moon rocket officially began just over 48 hours before the six massive engines on the 32-story rocket at last lit at 1:47 a.m. ET this morning, muscling the 2.6 million kg (5.75 million lb.) machine off of launch Pad 39B at the Kennedy Space Center in Florida, and hurling it moon-ward. With the successful liftoff, NASA’s Artemis program—which aims to have Americans back on the moon by as early as late 2025—at last got underway.
In some respects, however, the true countdown for this morning’s launch began on Jan. 15, 2004, when then President George W. Bush announced that the U.S. would be returning astronauts to the moon and called for the construction of a new heavy-lift rocket to make the journey possible.
“The desire to explore and understand is part of our character,” Bush said in a White House speech at the time. “We do not know where this journey will end, but we do know this: human beings are headed into the cosmos.” Exactly 18 years, 10 months, and one day later, that journey—for now without humans aboard—at last began.
The SLS will now make a 25-day journey during which an Orion spacecraft will complete two looping orbits around the moon before returning to Earth for a Dec. 11 splashdown. This morning’s liftoff was bedeviled by last-minute glitches involving a hydrogen leak at the base of the core stage of the rocket and a defective ethernet switch in the range safety mechanism, which would have been used to trigger a self-destruct system if the rocket had gone awry during launch. Repairs on both caused a 44-min. delay in the initially planned 1:04 a.m. ET launch. Once liftoff did occur, the flight went precisely according to the launch controllers plans.
The SLS is a six-engine rocket: its core stage is powered by four liquid fueled RS-25 engines—the same engines that powered the space shuttle. Flanking the core stage is a pair of solid rocket engines—also shuttle legacy hardware. Together, the half dozen engines put out 4 million kg (8.8 million lbs) of thrust, or 15% more than the 3.4 million kg (7.5 million lb.) produced by the Apollo era’s Saturn 5, once the most powerful rocket ever flown—until the liftoff of the SLS this morning.
The solid rocket boosters, which produce 75% of the rocket’s power, did not last long, burning for just two minutes and 12 seconds after ignition. Once the SLS reached an altitude of 48 km (29 mi.), the boosters shut down, separated, and fell away. After this point, the core stage engines burn for another six minutes and eight seconds before shutting down at a low-Earth orbital altitude of 161 km (100 mi.) and a speed of just under 28,300 km/h (17,500 mph). The Orion spacecraft and its own smaller second stage then separate from the core stage and, within 90 minutes, make one complete circuit around the Earth, before the second stage engine lights, accelerating the spacecraft to just under 40,200 km/hr (25,000 mph)—sufficient to peel away from Earth orbit and head out toward the moon. About 30 minutes after that—or two hours after liftoff—the second stage falls away too, leaving the Orion spacecraft to make the lunar journey on its own.
It will take Orion five days to reach the moon, where its own onboard engine will then fire, settling the spacecraft into a lunar orbit that will see it circle the moon at altitudes ranging from as low as 96 km (60 mi.) from the lunar surface to as high as 61,000 km (38,000 mi.). After two weeks circling the moon, Orion will relight its engine and head for home. If all goes well, the mission, known as Artemis 1, will be followed in 2024 by Artemis 2, which will see astronauts making a similar circumlunar journey—marking the first time humans have been in the vicinity of the moon since Apollo 17 in 1972. Artemis 3, a crewed lunar landing, will then follow.
“After 50 years, we’re going back to the moon, but this time to stay,” says NASA Administrator Bill Nelson. “We’re going to learn to work, to improve, to innovate, to create, in order that we can go to Mars later.”
Adds Chris Cianciola, deputy manager of the SLS program: “It’s a huge step for us both at the agency and for humanity. It’s the signal that we are going back to space, deep space, not low Earth orbit. This mission will kick off many of our objectives for a test flight before we put humans aboard.”
A Test Flight with Experiments on Board
While the Artemis 1 mission is largely an engineering exercise—designed to prove the flight worthiness of the SLS and Orion—there is also some solid science being done. Hitchhiking aboard the rocket were 10 CubeSats—or mini-satellites, each about the size of a shoebox—that were released into space when the second stage separated. They will conduct a range of experiments.
One of the CubeSats will make seven orbits of the moon, scanning its surface for the presence of water ice in the lunar regolith, or soil, which future lunar astronauts could harvest and use. Another will hunt for hydrogen—which astronauts could also make use of for rocket fuel—in the moon’s permanently shadowed poles. Yet another, provided by JAXA, the Japanese space agency, will use a rocket engine and a cushioning airbag to make a landing on the moon, where it will measure lunar surface radiation.
On-board Orion will also be samples of plants, algae, fungus, and yeast, which will be recovered and studied when Orion makes its return to Earth, to measure the effect the ionizing radiation of deep space had on their genetic make-up—research that has implications for astronauts venturing into the same radiation field.
“We absolutely want to get as much out of this opportunity as we can,” says Cianciola. “There are some really unique payloads here and I’m excited about them.”
NASA’s Long Struggle to Launch
Those scientific findings are for later though. Today, NASA is celebrating the liftoff as a triumph not just of design and execution, but also institutional tenacity—the culmination of what was close to a generation of setbacks, course changes, and near-death experiences for the SLS.
Under the Bush Administration, the return-to-the-moon initiative was dubbed the Constellation program, and the new, heavy-lift rocket was known as the Ares V. NASA engineers and mission planners spent four years working on Constellation, designing and beginning construction on both the Ares V and Orion. By the time the Bush Administration left town and Barack Obama’s presidency began, however, Constellation was badly over budget and behind schedule. President Obama, who had never much mentioned space as a priority on the campaign trail, pulled the plug on the program in 2010, redirecting Orion money to other NASA projects, including the continued construction and maintenance of the International Space Station.
Congress, however, had a thing or two to say about that—especially the delegations from space-centric Texas, Alabama, and Florida—and pushed to restore funding for both Orion and the Ares V, not to mention the jobs they represented. Obama relented—but only partly. Constellation was still a no-go and the moon was no longer on the itinerary. Instead, the White House proposed the head-scratching idea of sending an unmanned spacecraft to find a small asteroid, tow it to the vicinity of the moon, and have astronauts land there and explore it instead. The new rocket that would send the crews on the so-called asteroid-redirect mission (ARM) would also no longer be known as the Ares V. As a signal of the new seriousness—and frugality—of the space program, NASA and the White House settled on the more prosaic-sounding Space Launch System.
More changes were still to come under President Donald Trump’s Administration, which in 2017 canceled ARM and restored the moon as the first destination of the SLS and Orion, with eventual crewed missions to Mars also on the agenda for some time in the 2030s. The new moon-Mars program would be known as Artemis—named after the sister of Apollo.
Read more: NASA’s Mega-Moon Rocket Survives a Hurricane
It took until June 2021 before the final SLS rocket was at last fully built, with its components stacked together in the Kennedy Space Center’s Vehicle Assembly Building (VAB). It then went through a series of preparations and tests. The SLS made multiple trips to and from the VAB to pad 39B for simulated countdowns—known as wet-dress rehearsals—during which the rocket was loaded with more than 2.6 million liters (700,000 gal.) of fuel and the countdown proceeded to just seconds before what would be ignition, before the clock stopped and the fuel was drained. A rehearsal attempt in April failed, due to a fuel leak and a flaw in a venting valve, and it wasn’t until June of this year that NASA successfully completed the wet-dress and declared the rocket ready for launch.
Multiple attempts to get Artemis 1 off the pad were made in August and September, with an initial liftoff, planned for Aug. 29 scrubbed due to a fuel leak and a faulty temperature sensor on one of the core stage engines. Another attempt on Sept. 3 was canceled as well due to a hydrogen fuel leak. A Sept. 27 launch attempt was then called off and the SLS had to hightail it back to the VAB as Hurricane Ian approached Florida.
This morning’s launch too was postponed by two days from its original Nov. 14 target date, due to weather, this time in the face of Hurricane Nicole, though the projected winds and rain were within parameters to allow the rocket to remain on the launch pad without seeking cover.
As of this morning, Nicole has passed and the SLS—18 years in the making—has flown. That journey into the cosmos Bush called for so long ago has at last begun.
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