An Apollo-era heavy-lift truck carrying the 3.5 million-pound, 322-foot-tall SLS rocket and the 10.5 million-pound mobile launch platform was expected to depart from Kennedy Space Center’s iconic Vehicle Assembly Building around 9 pm EDT to begin the 4.2-mile trip to pad 39B. Once the mobile launcher is lowered onto pedestals above the pad early Wednesday, engineers will connect power, data, propulsion lines, water lines and other systems to prepare the rocket for grueling pre-launch testing and checkout. The Space Launch System moon rocket atop pad 39B at the Kennedy Space Center for a countdown rehearsal and power-up test earlier this year. NASA plans to roll the rocket back onto the pad Tuesday night to prepare the massive booster for its maiden launch on Aug. 29. NASA file photo If all goes well, the team will begin a 46 hour 10 minute countdown at 10:23am. EDT, Aug. 27, setting the stage for an 8:33 a.m. explosion. on Monday, August 29, starting a 42-day flight to send an unmanned Orion crew capsule around the moon and back. Backup launch opportunities, based on the ever-changing positions of the Earth and the Moon, along with the need to replenish launch spaceport supplies, are available on September 2 and 5. After that, NASA will have to move the SLS back to the VAB to service batteries and other systems, delaying the launch until later this fall. The goal of the Artemis 1 mission is to verify SLS performance, test the Orion solar crew capsule in deep space, and confirm that the 16.5-foot-wide heat shield will protect the ship during a hellish high-speed dive back to Earth. Earth’s atmosphere. at the end of the flight. Assuming an on-time launch, the Orion capsule will aim to land in the Pacific Ocean west of San Diego at 11:53 a.m. EDT on October 10. If the test flight goes well, NASA plans to launch four astronauts on the SLS rocket’s second flight in 2024 — Artemis 2 — followed by a third mission that would send the first woman and next man to the surface of the Moon in the 2025- 26. The SLS is the world’s most powerful operational rocket, using two solid-fuel boosters and four upgraded shuttle-era RS-25 engines to produce a combined 8.8 million pounds of thrust at launch, 15 percent more than NASA’s legendary Rocket Saturn 5 Moon. In its original “block 1” configuration, the SLS is capable of lifting nearly 30 tons to the moon. Planned variants, using a more powerful upper stage and advanced boosters, would be able to send nearly 50 tons to the moon in a single flight. SpaceX is building a bigger, more powerful Super Heavy-Starship rocket with twice the capacity, but it can’t do it in a single flight. The reusable Starship is designed to refuel in Earth orbit before departing for deep space. NASA conducted a full-duration test launch of the Boeing-built SLS core and four Aerojet Rocketdyne RS-25 engines at the Stennis Space Center in Mississippi last year. The booster was then sent to Florida, where the rocket’s second stage, supplied by United Launch Alliance, and the Orion capsule, built by Lockheed Martin, were attached. Engineers performed four dress rehearsal countdowns to pave the way for the launch, but the tests were marred by problems with the grounding system, a stuck helium valve and two troublesome hydrogen leaks, one where the main fuel line connects to the base of the main stage and another in a smaller component used to help cool the main engines. Hydrogen leaks are notoriously difficult to isolate and fix because they only appear when super-cold propellant is flowing through the lines and fittings. Repairs should be done at room temperature. Engineers successfully repaired the umbilical assembly, which functioned normally during a subsequent refueling test. But the engine’s main “bleed” line, repaired at the VAB after the most recent countdown rehearsal, has yet to be tested again under cryogenic conditions. That won’t happen until the SLS is fueled for launch on August 29. More William Harwood Bill Harwood has covered the US space program full-time since 1984, first as Cape Canaveral bureau chief for United Press International and now as a consultant for CBS News. It covered 129 space shuttle missions, every interplanetary flight since Voyager 2’s flyby to Neptune, and dozens of commercial and military launches. Based at the Kennedy Space Center in Florida, Harwood is a dedicated amateur astronomer and co-author of “Comm Check: The Final Flight of Shuttle Columbia.”
