Quick question: Why do we call it the "European Service Module" instead of just the "Orion Service Module"? We don't say "American Orion Capsule" and "American SLS Upper Stage" or whatever.
The Orion Service Module design is based on ESA's Automated Transfer Vehicle (ATV) spacecraft, and is not a NASA design.
So since it's based on a European design, it's called the European Service Module. No doubt if it was NASA designed and U.S. built, it would just be called the "Service Module".
Yes, obviously, but why? Why does Europe and NASA have to specify it. If NASA isn't slapping "American" on the title of everything they build, why does Europe have to.
Wrong assumption. Europe is not slapping the European title on to it. NASA did in fact.
Orion has a Service Module. That Service Module consist of four major components:
1. Crew Module Adaptor (CMA).
This is the 'cradle' that the CM is nesting in and forms the wide top part of the Service Module. This component is the structural 'bridge' between the CM and the ESM. It remains attached to the CM until just shortly before re-entry. The CMA is constructed in the USA.
2. European Service Module (ESM).
This is the Service Module component that attaches to the other end of the CMA. It provides the CM with electrical power, the gases and fluids for ECLSS, via an umbilical running thru and outside the CMA. It also provides (amongst others) attitude control, active thermal control, passive thermal control and propulsion for the entire Orion spacecraft. However, it is important to note that the ESM is only one (but rather important) component of the Service Module. It does NOT constitute the entire Service Module. The ESM is constructed in Europe. The main propulsion system is US-made however given that it consists of a re-purposed space shuttle OMS engine.
3. Spacecraft Adaptor (SA)
The backside of the ESM interfaces with the top-ring of the SA. The bottom-ring of the SA interfaces with the launch vehicle adaptor. The SA is one of two parts of the Service Module that is discarded during launch into orbit. Orion separates from the launch vehicle at the SA-ESM separation-plane, leaving the SA attached to the launcher. The SA is constructed in the USA.
4. Spacecraft Adaptor Jettisoned Panels (SAJP)
The SA, bottomside of the CMA and outside of the ESM are protected, during launch, from the effects of high-speed flight thru the lower part of Earth atmosphere. This is done by encapsulting the SA and ESM in a barrel-like construction. This barrel consists of three jettisonable panels. The panels interface at the top with the bottom-outer-ring of the CMA and they interface at the bottom with the bottom-ring of the SA. The SAJP are constructed in the USA.
So, as you can see, the ESM is only part of the entire Service Module for Orion. The component needed a name. NASA chose to name it the ESM because it is the only one of the four major components that is not produced in the USA, but in Europe in stead.