Mature Space Shuttle technology demonstrates that what’s old is new again.
With the successful launch of Artemis 1, NASA is back in the crewed space exploration business, with the largest rocket successfully launched anywhere. The combined 8,000,000 pounds of thrust at launch exceeds the power of the Saturn V launch vehicle that carried a dozen astronauts to the moon. The new system uses developments of legacy Space Shuttle engines and solid rocket boosters, with a booster structure derived from the Space Shuttle external tank. Development of advanced hardware from proven components was controversial, with some NASA critics stating that the approach would prove as expensive and lengthy as clean sheet designs, but with a successful launch, the new Space Launch System appears set to be NASA’s heavy lift launch vehicle for the foreseeable future.
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With the successful launch of Artemis 1, NASA is back in the crewed space exploration business again, with the largest rocket yet launched by anyone, anywhere.
The combined 8,000,000 pounds of thrust at launch exceeds the power of the Saturn V launch vehicle that carried a dozen astronauts to the Moon. The vehicle for Artemis 1 is the Space Launch System, a large core stage with two jettisonable solid rocket boosters, the combination of which lifts an upper stage capable of propelling an Orion spacecraft, or other payload, out of Earth orbit.
The Space Launch System is all new, but uses technology derived from Space Shuttle components with development histories that go back to the 1970s.
Those engines are not only derived from the Space Shuttle main engine program, but for Artemis 1 are engines flown on previous Shuttle missions. Although designed to be reusable, the Space Launch System is expendable, and future new build engines will delete the reusability capability.
The core stage is the largest rocket stage ever built and weighs 2,300,000 pounds when full with its 733,000 gallons of propellant. 2,300,000 pounds is heavy, but the four engines produce 2,000,000 pounds of thrust. The solid rocket boosters provide the supplemental thrust needed to overcome the core stage, upper stage and payload mass.
Northrop Grumman built the solid rocket boosters, which are upgraded Space Shuttle SRBs with an additional fifth motor segment. Like the core stage, the SRBs are record-breaking, the most powerful solid rocket boosters ever built for spaceflight. Each booster generates 3,600,000 pounds of thrust and consumes six tons of solid propellant per second.
The twin boosters provide over 75 percent of total SLS thrust capability at launch. SLS is designed specifically to carry payloads out of Earth orbit, and the Artemis 1 mission represents the Block One configuration, carrying an interim cryogenic propulsion stage and Orion spacecraft, as well as a launch abort system.
The Block One configuration can propel 27 tons to the Moon. The system can accept different upper stage and payload configurations, and future production blocks will carry a higher performance exploration upper stage capable of lofting up to 46 tons of payload out of Earth orbit.
The Space Launch System is intended to be NASA’s primary booster for the next two decades at least, but there is a commercial competitor in the very heavy lift launch market: SpaceX. The SpaceX heavy lift system is called Starship, and when it flies later this year it will dwarf even the Space Launch System for booster mass and thrust, launching on a cluster of 33 Raptor engines generating 16,000,000 pounds of thrust. 100 tons to low Earth orbit is predicted, and a private, commercial, crewed flight around the moon is scheduled for 2023.
Full reusability means that the SpaceX system is expected to be lower in operating cost, although no one knows at this point whether the new but reusable versus expendable but mature technology race will create a clear winner. Both systems will coexist for years, and at this point, the Space Launch System has taken an early lead.
Which system will deliver the first humans to the moon after half a century will be determined in a year or two.