One of the two modules Orion will deliver in 2024 mission is ESPRIT, which stands for European System Providing Refueling Infrastructure and Telecommunications. As the name implies, ESA is the likely provider, though a formal agreement with NASA has not been announced.

ESPRIT, according to Hambleton, includes a science airlock, fuel storage, refueling capabilities for the power and propulsion module, additional communications equipment, and external payload stowage. The science airlock seems to be separate from an airlock that would be used to receive Moon and Mars samples set to be shipped back to Earth aboard Orion.

The second Gateway piece Orion will deliver is a U.S.-built utilization module that will provide extra space and consumables for visiting astronauts, as well as "external robotic interfaces" — presumably, a modified version of the beloved Canadarm.

Blasting Orion and both modules into space all at once will require SLS with its new Exploration Upper Stage. (Up to three initial SLS flights will use an interim upper stage.) Since the new upper stage is taller and has different interfaces, it will require use of a second, yet-to-be-built mobile launcher authorized by Congress earlier this year.

Getting all this ready in six years will be very, very difficult. Somewhere amid these lunar activities, NASA plans to launch the Europa Clipper as early as 2023 — meaning there could be two SLS flights in one year.

The budget is tight, too: The White House proposed $504 million for the Gateway in 2019, and $2.7 billion over the next 5 years. That seems like a sizable amount of money until you consider it has to cover two or three new human spaceflight modules. (ESPRIT could be provided as some sort of bartering arrangement with ESA.)

As currently envisioned, the 2024 Orion mission would last 30 days from launch to splashdown, with half of that time spent at the Gateway.

Tight timelines