European Service Module Steers Orion Home with Proven Engines and Steady Support Systems

Way down in the belly of the Orion spacecraft is a large cylindrical module built in Europe that provides almost everything the crew requires to safely return to Earth after a voyage to the Moon. The European Service Module houses all of the propulsion systems that maintain the crew safe and comfortable until splashdown, including power, water, air, and temperature control for all four astronauts. It was manufactured by Airbus for the European Space Agency, weighs a whopping thirteen tons and measures roughly four meters across and tall.

The engineers assembled the entire thing in Bremen, Germany, following extensive testing to ensure its reliability throughout the ten-day trip. Once Orion enters Earth orbit after launch, the module immediately begins attitude adjustments before launching the spacecraft to the Moon. On the way back, the same capability allows mission controllers and crew to adjust the path so that Orion lands in the restricted entry channel through the atmosphere at the optimal angle and speed. Without that level of control at all stages, the heat shield and parachutes would be unable to perform their functions.

The main propulsion system is supported by a large main engine that conducts all of the heavy lifting, providing the punch required to make significant adjustments in the spacecraft’s trajectory. NASA acquired that unit from the Space Shuttle program, where it flew on six missions between 2000 and 2002 before receiving a thorough overhaul and integrating it into Orion. On day two of the mission, the main engine performs most of the work on the trans-lunar injection, as well as any substantial corrections that may be required. Eight auxiliary engines are available as a backup and for minor orbital adjustments, allowing the team additional flexibility if the main engine need assistance. The primary and auxiliary engines work together to provide Orion with the necessary thrust to depart Earth orbit and then slow down for the final approach.

Twenty-four smaller reaction control thrusters, grouped in six tiny pods around the module, provide the necessary precision. These can be fired one at a time or in groups to rotate the spacecraft, keep it stable, or make minor adjustments to its orientation. During a planned demonstration in Earth orbit, the commander and pilot took physical control of the thrusters with hand controllers, and the system performed flawlessly. On the long journey back from the Moon, those thrusters keep Orion oriented in the right direction for the star trackers and communication antennas, as well as making minor adjustments to ensure the re-entry angle remains precise. Even the slightest deviation and the crew module would either skip off the atmosphere or fall in too steeply.

Solar arrays extend out of the module in four large blades, generating 11.2 kilowatts, enough to power the entire ship as well as the new high-speed laser link, which allows them to send data back to Earth at an incredible 260 megabits per second during those long quiet days when the spacecraft is simply drifting along. Even still, thanks to the continuous power provided by the solar arrays, the computers, sensors, and life support equipment continue to function normally. Back on Earth, engineers from the European Space Agency’s center in the Netherlands and NASA’s team in Houston are glued to their displays 24 hours a day, seven days a week, keeping a constant eye on power levels and engine performance in case anything unexpected occurs so they can catch it early.

Inside this same module, tanks hold 90 kilograms of oxygen and 240 kilograms of drinking water, which flow directly into the crew cabin. They also have an active thermal control system that circulates fluid to keep the temperature in check, whether it’s chilly outside or scorching when the sun shines down without wasting any electricity. All of these supplies make this service module the crew’s lifeline, keeping them healthy and safe while the navigators concentrate on getting them to their destination.