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
Why did the crew practise flying towards a discarded rocket stage?
Latest on Interim Cryogenic Propulsion Stage
- 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
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.