Space Launch System SLS; NASA’s Artemis Mega Rocket for Deep Space Exploration

NASA’s Space Launch System or SLS, is a super heavy-lift launch vehicle developed by NASA and awaiting launch that would provide the foundation for human exploration beyond Earth’s orbit into deep space. NASA’s first exploration-class rocket built for human space travel since the Saturn V. Engineers and industry partners are making progress toward delivering rockets for the next several Artemis missions. It is being developed in three major phases with increasing capabilities: Block 1, Block 1B, and Block 2. As of August 2019, SLS Block 1 launch vehicles are to launch the first three Artemis missions and five subsequent SLS flights are planned to use Block 1B, after which all flights will use Block 2

The first launch, designated Artemis 1, is scheduled for a period between 23 September and 4 October 2022 from Kennedy Space Center. The SLS is intended to become the successor to the retired Space Shuttle, and the primary launch vehicle of NASA’s deep space exploration plans through the 2020s. The SLS rocket is designed to be evolvable, which makes it possible to fly more types of missions, including human missions to the Moon and Mars and robotic scientific missions to places like the Moon, Mars, Saturn, and Jupiter.

Offering more payload mass, volume capability, and energy, SLS, the world’s most powerful rocket, can carry more payload to deep space than any other vehicle. SLS is designed for deep space missions and will send Orion or other cargo to the Moon, which is nearly 1,000 times farther than where NASA’s International Space Station resides in low-Earth orbit. The high-performance rocket will provide the power to help Orion reach a speed of 24,500 miles per hour—the speed needed to send it to the Moon.

The Space Launch System SLS Vehicles Configuration

The SLS is a Space Shuttle-derived launch vehicle. The first stage of the rocket is powered by one central core stage with four RS-25 engines and two outboard solid rocket boosters. All SLS Blocks (1, 1B and 2) share a common core stage design, while they differ in their upper stages and boosters.

SLS Block 1

The first SLS vehicle, called Block 1, can send more than 27 metric tons (t) or 59,500 pounds (lbs.) to orbits beyond the Moon. It will be powered by twin five-segment solid rocket boosters and four RS-25 liquid propellant engines. After reaching space, the Interim Cryogenic Propulsion Stage (ICPS ) sends Orion on to the Moon. The first three Artemis missions will use a Block 1 rocket with an ICPS.

SLS Block 1. 70t Crew Expanded View

SLS Block 1B

SLS Block 1B crew vehicle will use a new, more powerful Exploration Upper Stage (EUS) to enable more ambitious missions. The Block 1B vehicle can, in a single launch, carry the Orion crew vehicle along with large cargos for exploration systems needed to support a sustained presence on the Moon.

SLS Block 1B crew vehicle Expanded View

The SLS Block 1B crew vehicle can send 38 t (83,700 lbs.) to deep space including Orion and its crew. Launching with cargo only, the Space Launch System has a large volume payload fairing to send larger exploration systems to the Moon and Mars or for science spacecraft on solar system exploration missions.

SLS Block 2

The next SLS configuration, Block 2, will provide 9.5 million lbs. of thrust and will be the workhorse vehicle for sending cargo to the Moon, Mars, and other deep space destinations.
SLS Block 2 will be designed to lift more than 46 t (101,400 lbs.) to deep space. An evolvable design provides the nation with a rocket able to pioneer new human and robotic spaceflight missions.

Block 2 130t Cargo Expanded View

The Space Launch System SLS Design

To reduce cost and development time, NASA is upgrading proven hardware from the space shuttle and other exploration programs while making use of cutting-edge tooling and manufacturing technology. Some parts of the rocket are new and other parts have been upgraded with modern features that meet the needs of deep space missions, which require higher launch vehicle performance levels.

Core stage

Together with the solid rocket boosters, the core stage is responsible for propelling the upper stage and payload out of the atmosphere and accelerating up to almost orbital velocity. The Boeing Company, in Huntsville, Alabama, builds the SLS core stages, including the avionics that controls the vehicle during flight. Towering more than 212 feet with a diameter of 27.6 feet, the core stage stores 730,000 gallons of super cooled liquid propellant. and is both structurally and visually similar to the Space Shuttle external tank.

It contains the liquid hydrogen fuel and liquid oxygen oxidizer tanks for the ascent phase, the forward and aft solid rocket booster attach points, avionics, and the Main Propulsion System (MPS). The MPS is responsible for supplying the four RS-25 engines.

The first four flights will each use and expend four of the remaining sixteen RS-25D engines previously flown on Space Shuttle missions. Aerojet Rocketdyne modifies these engines with modernized engine controllers, higher throttle limits, as well as insulation for the high temperatures the engine section will experience due to their position adjacent to the solid rocket boosters. Later flights will switch to a RS-25 variant optimized for expended use, the RS-25E, which will lower per-engine costs by over 30%. The thrust of each RS-25D engine has been increased from 492,000 lbf (2,188 kN), as on the Space Shuttle, to 513,000 lbf (2,281 kN) on the sixteen modernized engines. The RS-25E will further increase per-engine thrust to 522,000 lbf (2,321 kN)

Core stages are built at NASA’s Michoud Assembly Facility in New Orleans using state-of-the-art manufacturing equipment, including a friction stir welding tool that is the largest of its kind in the world. With the Artemis I core stage complete, Boeing is building stages for the next few Artemis missions.

RS-25 Engines

Propulsion for the SLS core stage will be provided by four RS-25 engines. Aerojet Rocketdyne of Sacramento, California, is upgrading an inventory of 16 RS-25 shuttle engines to SLS performance requirements, including a new engine controller, nozzle insulation, and required operation at 512,000 lbs. of thrust. During the flight, the four engines provide about 2 million lbs. of thrust. The SLS Program and its industry partners tested the four RS-25 engines and the entire core stage in a “Green Run” test campaign that culminated in a successful, full-duration, 500-second hot-firing at Stennis. Aerojet Rocketdyne has tested new controllers for the engines and has processed engines for follow-on flights after Artemis I. In addition, Aerojet Rocketdyne has restarted production of new RS-25 engines and is developing and testing new, advanced components to make the engines more affordable.

SLS Rocket Boosters

Blocks 1 and 1B of the SLS are planned to use two five-segment solid rocket boosters. These solid rocket boosters use casing segments that were flown on Shuttle missions as parts of the four-segment Space Shuttle Solid Rocket Boosters. The prime contractor for the boosters, Northrop Grumman’s Northern Utah team, has modified the original shuttle’s configuration of four propellant segments to a five-segment version. They possess an additional center segment, new avionics, and lighter insulation, but lack a parachute recovery system.

Two shuttle-derived solid rocket boosters provide more than 75 percent of the vehicle’s thrust during the first two minutes of flight. The five-segment solid rocket boosters provide approximately 25% more total impulse than the Shuttle Solid Rocket Boosters, but will not be recovered after use.

The stock of SLS Block 1 to 1B boosters is limited by the number of casings left over from the Shuttle program, which allows for eight flights of the SLS. On 2 March 2019, the Booster Obsolescence and Life Extension program was announced. This program will develop new solid rocket boosters, to be built by Northrop Grumman Space Systems, for further SLS flights, marking the beginning of Block 2.

These boosters will be derived from the composite-casing solid rocket boosters then in development for the canceled OmegA launch vehicle, and are projected to increase Block 2’s payload to 290,000 lb (130 t) to LEO and at least 101,000 lb (46 t) to trans-lunar injection. As of July 2021, the BOLE program is under heavy development, with first firing expected in 2024.

In addition to the boosters for Artemis I, Northrop Grumman has completed motor segments for Artemis II and is working on boosters for missions beyond Artemis II. Trains transport booster segments from Utah to NASA’s Kennedy Space Center in Florida where they are stacked with forward and aft assemblies to create the largest, most powerful boosters ever built for spaceflight. The boosters’ avionics systems are tested at Kennedy and Marshall.

Space Launch System Upper Stages

The upper stage after the core stage comes as of the Integrated Spacecraft/Payload Element ( Interim Cryogenic Propulsion Stage (ICPS) and the The Exploration Upper Stage (EUS)

Integrated Spacecraft/Payload Element

The initial capability to propel Orion out of Earth’s orbit for Block 1 will come from the ICPS, The Interim Cryogenic Propulsion Stage (ICPS) is planned to fly on Artemis 1, 2, and 3 as the upper stage of SLS Block 1.  It is based on the Delta Cryogenic Second Stage 16 ft (5 m) used successfully on United Launch Alliance’s Delta IV family of rockets powered by a single RL10 engine made by Aerojet Rocketdyne. The engine is powered by liquid hydrogen and liquid oxygen and generates 24,750 lbs. of thrust. The first ICPS will use the RL10B-2 variant, while the second and third ICPS will use the RL10C-2 variant.

Block 1 is intended to be capable of lifting 209,000 lb (95 t) to low Earth orbit (LEO) in this configuration, including the weight of the ICPS as part of the payload. At the time of SLS core stage separation, Artemis 1 will be travelling on an initial 1,806 by 30 km (1,122 by 19 mi) suborbital trajectory. This trajectory will ensure safe disposal of the core stage. ICPS will then perform orbital insertion and a subsequent translunar injection burn to send Orion towards the Moon. The ICPS will be human-rated for the crewed Artemis 2 and 3 flights.

With two upper stages complete, United Launch Alliance is manufacturing the Artemis III ICPS. Teledyne Brown Engineering of Huntsville builds the launch vehicle stage adapter that partially encloses the ICPS and connects it to the core stage. The Orion stage adapter (OSA) will connect Orion to the ICPS on the SLS Block 1 vehicle. The OSA can accommodate several CubeSat payloads in 6 Unit or 12 Unit sizes, depending on mission parameters. For Artemis I, the OSA carries several 6U-sized CubeSats to deep space for various science and technology demonstration missions.

Exploration Upper Stage

The Exploration Upper Stage (EUS) is planned to fly on Artemis 4. The EUS will complete the SLS ascent phase and then re-ignite to send its payload to destinations beyond LEO. It is expected to be used by Block 1B and Block 2.

The EUS shares the core stage diameter of 8.4 meters and is powered by four RL10C-3 engines that produce almost four times more thrust than the one RL10B-2 engine that powers the ICPS. This 97,000 lbs. of thrust will allow more than 38 t (83,700 lbs.) for Block 1B crew and more than 42 t (92,500 lbs.) for Block 1B cargo to be sent to the Moon. NASA completed the critical design review for the EUS in 2019. Boeing is building the EUS at Michoud. Aerojet Rocketdyne has completed manufacturing and testing of several engines.

It will eventually be upgraded to use four improved RL10C-X engines, As of March 2022, Boeing is developing a new composite-based fuel tank for the EUS that would increase Block 1B’s overall payload mass capacity to Trans-Lunar-Injection by 30 percent. The improved upper stage was originally named the Dual Use Upper Stage (DUUS, pronounced “duce”) but was later renamed the Exploration Upper Stage (EUS).

With the EUS, NASA can use a Block 1B crew configuration to send Orion, astronauts, and payloads to deep space or use a Block 1B cargo configuration to send large cargoes to the Moon, Mars, or more distant destinations.

The SLS Team

SLS is America’s rocket with more than 1,100 companies from across the U.S. and at every NASA center supporting the development of the world’s most powerful rocket. The SLS Program, managed by Marshall, works closely with the Orion Program, managed by NASA’s Johnson Space Center, and the Exploration Ground Systems Program, managed at Kennedy. All three programs are managed by the Exploration Systems Development Division within the Exploration Systems Development Mission Directorate at NASA Headquarters in Washington, D.C.

Space Launch System SLS Planned launches and time

Originally planned for late 2016, the uncrewed first flight of SLS has slipped more than sixteen times and more than five years. As of earlier that month, the first launch was originally scheduled for 8:30 am EDT, 29 August 2022. It was postponed to 2:17 pm EDT (18:17 UTC), 3 September 2022, after the launch director called a scrub due to a temperature sensor falsely indicating that an RS-25 engine’s hydrogen bleed intake was too warm. The 3 September attempt was then scrubbed due to a hydrogen leak in the tail service mast quick disconnect arm; the next launch option is a period from 23 September to 4 October.

NASA limits the amount of time the solid rocket boosters can remain stacked to “about a year” from the time two segments are joined. The first and second segments of the Artemis 1 boosters were joined on 7 January 2021. NASA can choose to extend the time limit based on an engineering review. On 29 September 2021, Northrop Grumman indicated that the limit can be extended to eighteen months for Artemis 1, based on an analysis of the data collected when the boosters were being stacked. In late 2015, the Space Launch System program was stated to have a 70% confidence level for the first Orion flight that carries crew (Artemis 2), the second SLS flight overall, by 2023; as of November 2021, NASA delayed Artemis 2 from 2023 to May 2024.