Tomorrow is a big deal for those of us who one day hope to open the first Pinkberry on Mars: it's the first test of humanity's first interplanetary-capable manned spacecraft, Orion. The four-hour test will prove the spaceworthiness of the capsule. So what, exactly, will it be doing up there?

Essentially, this first flight is an unmanned, two-orbit shakedown of all of Orion's basic and crucial systems, from launch to reentry, and ending with an ocean-based recovery. It marks America's return to capsule spacecraft design after decades of spaceplanes like the Space Shuttle, and it's the first splashdown of a spacecraft since the Apollo CSM-111 capsule returned to Earth after the mission in 1975.

The Orion flight, while only four and a half hours long and comprising just two orbits, will manage to pack an awful lot into those two orbits. And those orbits themselves are not exactly ordinary — the second orbit will reach a height of 3,600 miles — that's about 15x the altitude of the International Space Station.

The reason for the large, high orbit is to better simulate the re-entry stresses the capsule would encounter if returning from, say, a lunar or perhaps asteroid-encounter mission. Even though this altitude will only get about 80% as hot as a lunar re-entry, it's good enough to test with.

Here's a breakdown of some of the things that will be tested on this flight:

This flight will use a Delta IV heavy rocket, and, since this rocket is not man-rated, and is unlikely to become man-rated anytime soon, it's very likely the only time this rocket will be used to launch an Orion. Until the Orion-specific launch vehicles are completed, it's the only readily-available US rocket that's capable of lifting the full Orion test rig's weight of 46,000 lbs to the 3,600 mile orbital apogee.

Unlike the Shuttles and more like every other capsule design, Orion will have an escape system for the capsule if something goes wrong with the launch vehicle. Ideally, a full test of this won't prove necessary for this flight, but the ejection of the system once in orbit will be.

Look, if you're going to build a spacecraft, it's got to work in space, right? So, all protective launching shrouds will be ejected, and the Orion capsule will get its first taste of the Big Black.

This also means that it needs to go through the Van Allen radiation belts (twice, once going up, once down) and be certain that all of the radiation-hardened systems and shielding survive the bombardment just fine.

The reaction control system on the capsule itself will be tested, though I don't think a full RCS test is planned for this test flight, as the main RCS thrusters are on the service module, and the service module for this flight is just a structural mockup.

Roughly standing in for the service module will be the Delta's upper stage, which will provide the thrust to get the Orion to the high orbit.

Of course, all this stuff is wildly important. Based on pictures and animations, it looks like the engines to insert the Orion into atmospheric re-entry are on the capsule itself; I'm not certain if the service module will take over this role, with capsule thrusters acting as backup, in the future.

The heat shield is derived from all of NASA's experience with the Space Shuttle's system, and, of course, has to endure much greater heat than just the low-earth orbits of the shuttles. Think 5,000°F. For that reason, an additional ablative heat-shielding system is employed.

And, of course, parachutes are a pretty big deal when you're hurtling back down to the earth, so here's the parachute system's chance to prove itself. It looks to be a three-parachute system similar to what was used for Apollo, but scaled up.

Remember, we haven't been pulling capsules out of the ocean for decades, so we're going to have to get used to it again, and that's a big part of this test. There's three-main recovery methods available, in order of preference: inside a 'well deck' of a ship, craned onto the deck of a different ship, or towed back behind some other ship.

There's also self-righting and flotation systems to test here, too.

All of this is covered in much more detail in this NASA video that I suggest you watch. It's pretty fascinating:

Thursday will be an exciting day. We're finally getting ready to get out of Earth's backyard and start some real exploration again, and this little jaunt around the block is the first important step. I hope everything goes by the book so we can start getting some warm bodies in these capsules and get back out there.