NASA teams across the country are preparing for the Artemis I launch to the Moon. When NASA’s mighty Space Launch System rocket launches to the Moon from the agency’s Kennedy Space Center in Florida, its four RS-25 engines and two solid rocket boosters will produce more than 8.8 million pounds of thrust. The rocket’s flight software and avionics systems act as the brains behind that muscle to guide and steer the rocket beyond Earth’s orbit.
The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA’s Space Shuttle. NASA is planning to continue using the RS-25 on the Space Shuttle’s successor, the Space Launch System (SLS).
Designed and manufactured in the United States by Rocketdyne (later known as Pratt & Whitney Rocketdyne and Aerojet Rocketdyne), the RS-25 burns cryogenic liquid hydrogen and liquid oxygen propellants, with each engine producing 1,859 kN (418,000 lbf) of thrust at liftoff. Although the RS-25 can trace its heritage back to the 1960s, the concerted development of the engine began in the 1970s, with the first flight, STS-1, occurring on April 12, 1981. The RS-25 has undergone several upgrades over its operational history to improve the engine’s reliability, safety, and maintenance load.
The engine produces a specific impulse (Isp) of 452 seconds (4.43 km/s) in a vacuum, or 366 seconds (3.59 km/s) at sea level, has a mass of approximately 3.5 tonnes (7,700 pounds), and is capable of throttling between 67% and 109% of its rated power level in one-percent increments. Components of the RS-25 operate at temperatures ranging from −253 to 3,300 °C (−400 to 6,000 °F).
The Space Shuttle used a cluster of three RS-25 engines mounted in the stern structure of the orbiter, with fuel being drawn from the external tank. The engines were used for propulsion during the entirety of the spacecraft’s ascent, with additional thrust being provided by two solid rocket boosters and the orbiter’s two AJ10 orbital maneuvering system engines. Following each flight, the RS-25 engines were removed from the orbiter, inspected, and refurbished before being reused on another mission. On Space Launch System flights, the engines will be expendable. For the first four flights, engines left over from the Space Shuttle program will be refurbished and used before NASA switches to the simplified RS-25E variant.
NASA’s Space Launch System (SLS) rocket will power NASA’s next-generation Moon missions through the agency’s Artemis program. NASA’s iconic “Worm†logo is depicted on the side of each of the SLS rocket’s solid rocket boosters. The letters are 8.3 feet tall with the entire worm logo stretching 28.7 feet from end to end on the boosters, which are taller than the Statue of Liberty. The simple, red logo was first introduced to the public in 1975. The original NASA insignia — nicknamed “the meatball†— rides to space on the top of the SLS rocket. The worm marking also appears on the Orion spacecraft riding atop the SLS rocket.
The Space Launch System (SLS) is a US super heavy-lift expendable launch vehicle, which is under development as of 2019. It is the primary launch vehicle of NASA’s deep space exploration plans, including the planned crewed lunar flights of the Artemis program and a possible follow-on human mission to Mars. SLS replaces the previous Ares V launch vehicle of 2005, although it shares a number of technologies and systems.
The initial SLS Block 1 is required by the US Congress to lift a payload of 95 metric tons (209,000 lb) to low Earth orbit (LEO), and will launch Artemis 1 and Artemis 2. The later Block 1B is intended to debut the Exploration Upper Stage and launch the Artemis 3 and the notional Artemis 4-8. Block 2 is planned to replace the initial Shuttle-derived boosters with advanced boosters and would have a LEO capability of more than 150 metric tons (330,000 lb), again as required by Congress. Block 2 is intended to enable crewed launches to Mars. The SLS will launch the Orion spacecraft and use the ground operations and launch facilities at NASA’s Kennedy Space Center in Florida.
The Orion Multi-Purpose Crew Vehicle (Orion MPCV) is a US-European spacecraft intended to carry a crew of four astronauts to destinations at or beyond low Earth orbit (LEO). As of August 2019, it is under development by NASA and the ESA for launch on the Space Launch System (SLS), Orion is intended to be the main crew vehicle of the Artemis lunar exploration program and other missions not far beyond lunar space. Artemis 1 is planned to be the first flight of Orion on SLS, Artemis 2 the first crewed flight, and Artemis 3 the first lunar landing via the Lunar Gateway.
The Orion MPCV uses the same basic configuration as the Apollo command and service module (CSM) that first took astronauts to the Moon, but with an increased diameter, updated thermal protection system, and a host of other modern technologies. Orion will support long-duration deep space missions with up to 21 days active crew time plus 6 months quiescent spacecraft life. During the quiescent period crew life support would be provided by another module, such as the proposed Deep Space Habitat. The spacecraft’s life support, propulsion, thermal protection, and avionics systems can be upgraded as new technologies become available. The Orion spacecraft includes both crew and service modules, and a spacecraft adapter. The Orion’s crew module is larger than Apollo’s and can support more crew members for short or long-duration missions. The European service module propels and powers the spacecraft as well as storing oxygen and water for astronauts.
NASA’s Orion, Space Launch System (SLS), and Exploration Ground Systems (EGS) programs are continuing work on one of the most complex and sophisticated space systems ever built. Across America and in Europe, teams are developing and building the spacecraft, rocket, and infrastructure necessary to send humans to deep space destinations including the surface of the Moon and beyond.
Some major recent milestones include: Orion – Crew Module Uprighting System Test at Atlantic Beach, North Carolina; European Service Module Solar Array Expanded; Fit Check in the Super Guppy Aircraft; Ascent Abort-2 Launch Abort System Stacking and Integration at Kennedy Space Center in Cape Canaveral, Florida; Launch Abort System Attitude Control Motor Test in Elkton, Maryland. SLS – Liquid Oxygen Tank and Forward Skirt join at Michoud Assembly Facility in New Orleans, Liquid Hydrogen Tank Structural Test Article Unload from Pegasus Barge at Marshall Space Flight Center in Huntsville, Alabama; RS-25 Engine Testing at Stennis Space Center in Bay St. Louis, Mississippi; Core Stage-1 Engine Section and Boat Tail Completed and Mated at Michoud. EGS – at NASA’s Kennedy Space Center: Core Stage Intertank Umbilical Swing Testing; Launch Pad 39B Upgrades; Crawler Engine Maintenance.