SpaceX has announced that the first major test of its Crew Dragon (aka Dragon V2) is expected to take place tomorrow, May 6, from Space Launch Complex 40 (SLC-40) in Cape Canaveral.

For the first launch of the Crew Dragon capsule, SpaceX will be performing what's known as a pad abort test, which will test the capsule's launch abort capabilities. While the next test after this one (the in-flight abort test) will launch a Crew Dragon using a full-size Falcon 9 rocket, this first test will see the Crew Dragon take off from the launchpad using its own integrated SuperDraco thrusters. The capsule will ascend to around 1500 meters (4,900 feet) before separating from the trunk section; it will then deploy its parachutes and land about 2,200 meters (7,200 feet) down range in the Atlantic Ocean.

The Crew Dragon's launch abort system is very different from how it's usually done. In the case of Mercury, Apollo, and Soyuz, the launch escape is provided by way of a rocket on top of the capsule, which ignites and pulls the crew away from the main launch vehicle. This system works, but unless the rocket is actually used (and you pray it won't be), it is simply extra weight that has to be jettisoned a few minutes after launch. Crew Dragon's launch abort system consists of eight SuperDraco thrusters that are built into the capsule itself, which is much tidier way of doing things.

The pad abort test is the the first step towards making sure that Crew Dragon is actually safe enough for human spaceflight; think of it as the first test of the capsule's ejector seat... except it's the whole spacecraft being ejected, rather than just a seat. Every crewed spacecraft must have a launch-abort capability, in case of a technical failure or abnormality during a real launch.

If the pad abort test is successful, there will then be an in-flight abort test at a later date, with the Crew Dragon separating from a Falcon 9 rocket at an altitude of a few miles. In both tests, the main purpose is to gather lots and lots of data through hundreds of real-time sensors, both on the spacecraft and within a crash dummy that's seated in the cockpit. It would certainly be nice if the pad abort test goes off without a hitch tomorrow, but as SpaceX says, "the odds of encountering delays or issues are high."

The current target for SpaceX's first human missions, incidentally, if no major road blocks are hit, is 2017.