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Interim Cryogenic Propulsion Stage
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Interim Cryogenic Propulsion Stage

SLS upper stage used as Artemis II proximity-ops docking target.

Last refreshed: 2 April 2026 · Appears in 1 active topic

Key Question

Why did the crew practise flying towards a discarded rocket stage?

Timeline for Interim Cryogenic Propulsion Stage

#1 1 Apr

Mentioned in: Four Astronauts Leave Earth for the Moon

Artemis II Moon Mission
#1 1 Apr

Mentioned in: Crew Flies Orion to Within Ten Metres of Upper Stage

Artemis II Moon Mission
#1 26 Feb

Redesignated after NASA cancelled Block 1B and Block 2 SLS upgrades

Artemis II Moon Mission: NASA Cancels SLS Upgrades and Delays First Landing
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Follow Artemis II Moon Mission →

Background

The Artemis II crew flew Orion to within 10 metres of the detached ICPS during a 70-minute manual proximity-operations demonstration, validating close-approach handling ahead of future lander rendezvous.

The ICPS is derived from the Boeing Delta IV upper stage. After the SLS core stage separates, it provides the trans-lunar injection burn that sends Orion toward the Moon, then detaches and is disposed of in deep space. It stands approximately 13.7 m tall and burns liquid hydrogen and liquid oxygen.

Using the discarded ICPS as a proximity target was an engineering workaround: Artemis II has no dedicated rendezvous target. The exercise validates manual docking skills needed to dock with the Human Landing System on Artemis III, making the test a rehearsal for the Moon landing itself.

Common Questions
What is the Interim Cryogenic Propulsion Stage?
The ICPS is the upper stage that fires after SLS core separation to send Orion toward the Moon, then detaches and is discarded.Source: NASA Artemis II mission overview
Why did Artemis II fly close to the ICPS?
The crew used the detached ICPS as a proximity target to practise manual close-approach manoeuvres needed for future lander docking.Source: NASA Artemis II mission report
How close did Orion get to the ICPS?
The crew flew Orion to within 10 metres during a 70-minute demonstration.Source: NASA Artemis II mission report
What is the ICPS used for on future Artemis missions?
On Artemis III and beyond, a similar stage concept supports the trans-lunar injection burn before crew docks with the Human Landing System.Source: NASA Artemis programme documentation
ICPS vs SLS core stage — what is the difference?
The SLS core stage provides main ascent thrust; the ICPS fires after separation to achieve the Velocity needed for lunar trajectory.Source: NASA SLS fact sheet