When the United States sends its first, initially unmanned Orion spacecraft into orbit around Earth's natural satellite in spring 2022 in preparation for future astronautical missions, it will be powered by German technology. Orion is currently being prepared for its first voyage with this propulsion and supply unit – the so-called European Service Module (ESM) – at Kennedy Space Center in Florida.
Under the leadership of the US space agency NASA, the Artemis programme aims to mark the next giant leap in spaceflight. Following the uncrewed Artemis I mission and a crewed test flight around the Moon, Artemis III is expected to land humans on the lunar surface in around 2025. The Lunar Gateway space station will be delivered into lunar orbit in a parallel project. In future, this will serve as an intermediate station for astronautical Moon landings and flights further into space, including to Mars.
The ESM plays a vital role and marks a significant advance for European spaceflight and German space technology in particular. The Artemis space transport system, known as Orion or the Orion Multi-Purpose Crew Vehicle, consists of two main parts: the US Crew Module and the cylindrical ESM containing the primary engine for the flight to the Moon. Four solar panels supply the spacecraft with power. The ESM climate systems ensure that the temperature is optimally regulated for the astronauts and the cargo. Fuel, oxygen and water supplies for the crew are also stored in the ESM. When fully loaded, it weighs approximately 13 tonnes at launch. The ESM delivers the Orion capsule into orbit around the Moon. It only separates from Orion at the end of the mission, before burning up in Earth's atmosphere.
When developing the service module, European aerospace engineers drew upon the experience that they had gained from the successful Automated Transfer Vehicle (ATV) programme. The ATV provided the International Space Station (ISS) with crew supplies fully automatically and at regular intervals over five missions between 2008 and 2015. The basic technology tried and tested in the ATV programme now lives on in the ESM. This is visible on the outside in the form of the x-shaped solar arrays used to generate electricity, which were an important feature of the ATV.
Germany's leading contribution to the ESM
With Artemis, NASA is collaborating with international partners on a critical component of an astronautical mission for the first time. This is a significant vote of confidence in the performance of spacefaring European nations. A European industry consortium, led by Airbus Defence and Space in Bremen and spread across 10 countries, has now implemented the first ESM-1 flight unit. ESM-1 bears the name of the Hanseatic city from which it originates – 'Bremen'. Another ESM for the second Artemis mission – the first crewed Moon mission of the 21st century – has already been transported from Bremen to the Kennedy Space Center. The ESM for Artemis III is currently in the final stages of assembly at Airbus in Bremen. To date, NASA has ordered six European service modules as part of its Artemis programme.
In joint international space projects led by NASA, including the ISS, the established practice is for NASA partners in Canada, Japan and Europe to contribute to supply and operational elements not as an exchange of funds, but in the form of technologies provided under 'barter agreements'. For ESA, these have thus far consisted of the development of the ATV space transport vehicle and its cargo deliveries to the ISS. As the largest contributor to ESA, Germany provided roughly 40 percent of the development, production and mission costs of the ATV programme. The ESM contribution covers Europe's current share of the ISS operating costs and the use of the Lunar Gateway.
Germany is the primary European partner of the other spacefaring nations involved in the ISS (USA, Russia, Japan and Canada) and was a major supporter of the decision to build the ESM at the ESA Council at Ministerial Level in Naples in 2012. Germany provides approximately 50 percent of the ESM programme budget, with the country's share managed by the German Space Agency at DLR.
ESM technical specifications
Weight and dimensions
The Orion ESM is cylindrical in shape, approximately four metres in diameter and approximately four metres tall. It weighs 13 tonnes at launch (including 8.6 tonnes of fuel), making up more than half the total mass of the Orion spacecraft.
Materials
The ESM exterior is covered with a Micrometeoroids and Debris Protection System (MDPS) made of Kevlar and Nextel. Important systems such as the electronic flight systems are duplicated and located on opposite sides of the module.
Engines
The ESM is the main propulsion system for the Orion spacecraft. It is also responsible for manoeuvring in orbit and position control. The fuel – a mixture of monomethylhydrazine (MMH) and mixed nitrogen oxides – is stored in titanium tanks and provides energy for the main engine, eight auxiliary engines and 24 smaller engines for position control.
Wingspan
The ESM has a four-wing solar array. Each wing consists of three separate panels that unfold to their seven-metre length after launch, hence giving the spacecraft a wingspan of 19 metres across.
Energy supply
With 15,000 solar cells, the four solar arrays generate enough energy to supply two households. Each sail rotates on two axes to align with the Sun for maximum power generation.
Interior equipment
Each ESM contains more than 20,000 parts and components, from the electrical equipment, engines, solar cells, fuel tanks and life support systems to around 12 kilometres of cables.
