NASA’s Orion spacecraft, powered by the European Space Module, is an exploratory vehicle designed for longer-duration flights beyond the Moon.  

Following Orion’s Exploration Mission-1 (EM-1), during which the spacecraft will travel beyond the Moon, enter a distant retrograde orbit around the Moon and return to Earth unmanned, EM-2 will see a crewed spacecraft complete a slightly different flight path. 

Orion with ESA service module

The goal of EM-1 is more technical, testing the capabilities of the Orion spacecraft with NASA’s Space Launch Systems (SLS) rocket as well as manoeuvres and trajectories for flights beyond the Moon. Building on this, EM-2 will continue to test the functionality during a crewed mission. As such, Orion will be equipped with oxygen tanks for its second mission, which are not needed for the ground-controlled EM-1. 

In addition to a crew, Orion’s second mission will feature a change in upper stage propulsion. For EM-1, SLS includes an interim cryogenic propulsion stage (ICPS), powered by liquid oxygen and liquid hydrogen, that will give the spacecraft the thrust it needs to enter translunar trajectory. For the second mission, ICPS will be replaced by an exploration upper stage (EUS) that will provide even more powerful thrust. 

Orion European Service Module flight model-2 logo

Like EM-1, Orion’s second mission will be launched from the Kennedy Space Center in Florida, USA, currently scheduled for 2021. Once in low-Earth orbit, EUS will fire to insert the spacecraft into a highly elliptical demonstration orbit around Earth. The European Service Module will then give the spacecraft its final push to inject it into translunar orbit.

The crew will fly Orion to 70 000 km beyond the Moon before completing a lunar flyby and returning to Earth. The mission can take a minimum of 8 days and will collect valuable flight test data. 

Technical details of the European Service Module

The total launch mass of ESA’s contribution to the Orion mission is 13 500 kg for the lunar missions (Orion will weigh over 20 tonnes in total):

• 8600 kg of usable propellant
• 240 kg of potable water
• 30 kg of nitrogen
• 90 kg of oxygen
• Payload volume up to 0.57 m3
• Payload mass up to 380 kg

EM-2 step by step:

• Launch by SLS from pad 39B, Kennedy Space Center
• Mission control perform final checks in low-Earth parking orbit
• Injection into elliptical high Earth demonstration orbit by EUS
• EUS disposal
• Translunar injection by Orion
• Trip to the Moon
• Flyby of the Moon
• Free-return trip to Earth (no engine firing required)
• Separation of the Crew Module from the expendable elements of Orion (the European Service Module and the Crew Module Adapter)
• Reentry of the Crew Module and splashdown in the Pacific Ocean