The most powerful space rocket ever to leave Earth will take a 50-year leap across the heavens when it rises from its Florida launchpad on Monday, one of the final crucial test steps before humanity’s return to the moon for the first time since 1972. Artemis 1, comprising Orion, a six-person deep-space exploration capsule, atop a 98m (322ft), 2,600-tonne (2,875-ton) Space Launch System (SLS) megarocket, is scheduled for its maiden liftoff at 8.33am ET (1.33pm UK time) from the same Cape Canaveral launch complex that staged the Apollo lunar missions half a century ago. As well as the spectacular show of fire expected to draw hundreds of thousands of spectators to Florida’s space coast, Nasa is keen to showcase the progress it has made in its efforts to place astronauts back on the moon. “This day has been a long time coming,” Nasa’s associate administrator Robert Cabana said after mission managers concluded a flight readiness review this week. “We are a go for launch, which is outstanding.” Monday’s scheduled test flight, which has a two-hour launch window and will last 42 days on a 1.3m-mile odyssey to 40,000 miles beyond the far side of the moon and back, includes two close fly-bys 62 miles above the lunar surface. Orion is uncrewed, other than mannequins that will allow Nasa to evaluate its next-generation spacesuits and radiation levels, and a Snoopy soft toy that will float around the capsule as a zero gravity indicator. But a successful mission would propel the agency closer to its goal of sending two astronauts, including the first woman, for landing at the moon’s south pole by the end of 2025, while up to two others remain in lunar orbit in a command module. An interim second test flight, Artemis II, is scheduled for May 2024, carrying a crew of four to the moon and back, although not landing, and sending humans beyond low Earth orbit for the first time since Apollo 17 in December 1972. That mission almost 50 years ago also carried the final two of only 12 people, all men, ever to have set foot on the moon, Harrison Schmitt and Eugene Cernan. “This is now the Artemis generation. We were in the Apollo generation. This is a new generation. This is a new type of astronaut,” Bill Nelson, the Nasa administrator and a former space shuttle astronaut, told a press briefing earlier this month. Noting the symbolism in the programme’s name – in Greek mythology Artemis is the twin sister of Apollo – he added: “To all of us who gaze up at the moon, dreaming of the day humankind returns to the lunar surface … folks, we’re here.” Despite being a new rocket, SLS draws heavily from existing technology. Its 8.8m pounds of core stage thrust, 15% more power than the Apollo-era Saturn V rockets, come from four RS-25 engines recycled from the space shuttle programme that ended in 2011. Likewise, the two five-stage solid rocket boosters are “based on three decades of knowledge and experience gained with the space shuttle booster, and improved with the latest technology,” Nasa said. After reaching lower Earth orbit about eight minutes into flight, a trans-lunar injection burn will increase Orion’s speed from 17,500mph to 22,600mph to escape the pull of Earth’s gravity and guide the craft to a precise point close enough to be captured by the moon’s gravity. Nelson said the flight would allow mission managers to thoroughly test the capabilities of the rocket and capsule to ensure its safety for human spaceflight. “We’re going to stress it and test it. We’re going to make it do things that we would never do with a crew on it in order to try to make it as safe as possible,” he said. Orion will stay in space longer than any human spacecraft in history without docking to a space station, and its return home, to a Pacific Ocean splashdown in mid-October, will be faster and hotter than any vehicle before it. Travelling at up to 25,000mph, the capsule will defy temperatures of about 2,800C (5,000F) as it re-enters Earth’s atmosphere and decelerates to around 300mph. Three parachutes will then deploy to further slow Orion to less than 20mph for splashdown off San Diego, California. The development of Nasa’s first moon craft in two generations has followed a rocky path. The heavy-lift SLS rocket ran into problems during testing last year while already three years behind schedule and almost $3bn (£2.5bn) over budget. The $4.1bn cost of each launch has also drawn scrutiny, with Paul Martin, Nasa’s inspector general, reporting to Congress in March that the figure was “unsustainable”. By latest estimates, Nasa will have spent $93bn on the program by 2025, with large amounts going to private contractors in the US, including Lockheed Martin, which developed Orion, and Boeing, which built the SLS core stage. “Nasa has already taken steps, at least tentatively, to buy a production series of SLS, which will help in reducing the cost if you buy several at a time instead of one each,” said John Logsdon, founder of the Space Policy Institute at George Washington University. Logsdon also notes the concern of analysts such as the American Institute of Aeronautics and Astronautics (AIAA) that the Artemis programme, partly because of Nasa’s reliance on outside partners, lacks the defined leadership structure and control of the almost entirely in-house Apollo and space shuttle projects. “A piecemeal, uncoordinated approach is doomed to failure,” the group told the congressional science, space and technology committee in March. The criticism is valid, Logsdon said. “There’s general agreement that the management structure Nasa has evolved for Artemis needs fixing, and there needs to be some central structure to manage all the elements of what’s a very complex undertaking. “[But] a schedule is just a schedule. And two years between this mission and the next does not seem to me to be very aggressive. “This is, after all, a test mission. Lots of things can go wrong, some things are likely to go wrong. The question is are they catastrophic failures, or failures that can be addressed and fixed, and we won’t know that until we fly the mission. Nasa recognizes that the world is watching.”