Artemis II

The Space Launch System (SLS) is a heavy-lift launch vehicle developed by NASA for its Artemis program, which aims to return humans to the moon and eventually enable crewed missions to Mars. Although SLS shares some hardware with the Space Shuttle, such as the RS-25 engines, Solid Rocket Boosters (SRBs), and Core Stage tank, it has a new, more ambitious mission that requires a different design approach.

Core Stage

 
SLS being lifted ahead of Green Run // Credit: NASA

The Core Stage is the largest component of the SLS rocket and serves as the fundamental structural support for the entire vehicle. It weighs over 2.3 million pounds and stands over 200 feet tall. The RS-25 engines, which were previously used in the Space Shuttle program, are powered by two massive propellant tanks located in the core stage. These tanks hold the liquid hydrogen and liquid oxygen fuels needed to produce the necessary thrust. The liquid hydrogen tank is situated at the top of the core stage, while the liquid oxygen tank is located at the bottom.

The core stage also includes a number of critical systems, such as avionics and flight computers, guidance and navigation systems, termination systems, and environmental control systems. These systems work together to ensure that the core stage can function safely and reliably during flight. The avionics and flight computers are responsible for monitoring the performance of the rocket and making adjustments as necessary. The guidance and navigation systems help keep the rocket on course, while the termination systems ensure that the rocket can be safely destroyed in the event of a catastrophic failure.

Solid Rocket Boosters

 
SLS SRB test fire // Credit: NASA

The Solid Rocket Boosters (SRBs) used in the SLS are an enhanced version of the SRBs used in the Space Shuttle program. While the Shuttle's SRBs were four segments tall, those on the SLS have five segments, providing around 25% more thrust, at 16 million Newtons each. The SRBs are responsible for providing additional thrust during the early stages of flight, helping to propel the rocket beyond Earth's atmosphere. However, unlike the Shuttle program, NASA will not be recovering SRBs from SLS launches. This is due to the lack of necessity for fast turnaround times, unlike that of the Shuttle.

Interim Cryogenic Propulsion Stage (ICPS)

 
ICPS in orbit during Artemis I mission // Credit: NASA

The Interim Cryogenic Propulsion Stage (ICPS) is a vital component of the SLS, designed to provide the propulsion necessary to send the spacecraft on its intended trajectory. It is situated on top of the core stage and comprises a single RL10B-2 engine manufactured by Aerojet Rocketdyne, along with a propellant tank that holds a mixture of liquid oxygen and liquid hydrogen.

The ICPS has the ability to provide up to 75,000 pounds of thrust for a period of approximately 1200 seconds, which is sufficient to get the spacecraft into its desired orbit. Once the spacecraft has reached the required altitude, the ICPS will perform a separation manoeuvre and release the payload for its journey to the moon or beyond.

The ICPS also includes an avionics and guidance system, which is responsible for controlling the engine and ensuring that the spacecraft is on the correct trajectory. This system is linked to the core stage and is designed to provide real-time data to the flight controllers at NASA's Mission Control Center in Houston, allowing them to monitor the spacecraft's progress and make any necessary adjustments.