Photos: Delta 4-Heavy with Orion on eve of launch

A model of NASA’s Orion spacecraft, in development to loft astronaut crews into deep space, was dropped from a U.S. Air Force cargo plane over Arizona on Wednesday in the latest in a series of tests to verify the capsule’s parachutes are up to the job of safely landing with humans on-board.

Fueled segments of the solid rocket boosters that will lift off on the first flight of NASA’s Space Launch System have arrived at the Kennedy Space Center in Florida, but officials will hold off on stacking the boosters until the SLS core stage completes a crucial test-firing later this year.

NASA officials released a nearly five-year, $28 billion plan Monday to return astronauts to the surface of the moon before the end of 2024, but the agency’s administrator said the “aggressive” timeline set by the Trump administration last year hinges on Congress approving $3.2 billion in the next few months to kick-start development of new human-rated lunar landers.