One week before its schedule launch of an International Space Station (ISS) supply demo mission, SpaceX (News - Alert) ran a simulated countdown and two second static fire of the Falcon 9 rocket's first stage. On the morning of May 7, assuming no technical hiccups or weather delays, the Falcon 9 will carry a Dragon capsule into low earth orbit for what the company hopes with be the start of regular paying cargo delivery missions to the space station.

The April 30 full launch rehearsal at the company's licensed Space Launch Complex 40 (SLC-40) at the Cape Canaveral Air Force Station originally scheduled the static firing of the nine engines of the Falcon 9 at 3:00 PM ET, but the company ran into a software glitch that delayed the event until 4:15 PM ET.   The Merlin 1-C engines fired for two seconds as scheduled before shutting down as planned.   

Engineers are now looking over the firing data, but SpaceX will have what is described as an "instantaneous" window for launch at 9:38 AM ET on May 7. A software glitch during the countdown introducing a delay would cause a launch scrub and force SpaceX into resetting to launch on May 10.

A delay to May 10 causes other complications, since a new three man crew is scheduled to be launched to the space station on May 13. Launching on May 10 gives SpaceX a single rendezvous and docking try before ISS operations shift to preparing for the arrival of the Russian Soyuz and its crew.

When the COTS (Commercial Orbital Transportation Services) 2/3 mission launches, the SpaceX Dragon capsule/service module be put into low earth orbit and make a steady, cautious approach to the space station as all of its systems are checked out. On day 3 of the flight, the Dragon will make a pass "under" ISS at a range of about 1.5 miles to validate all sensors and flight systems necessary for a closer rendezvous; a docking abort will also be tested.

If all goes well, flight day 4 will be a close rendezvous between the SpaceX Dragon vehicle and the space station as the two slowly close together. The Dragon will stop close enough to the station so a robotic arm can grab it and pull it in for berthing. Once connected, there will be a short ceremony and about 2500 pounds of non-critical supplies will be unloaded during Dragon's stay at the station. 

NASA and SpaceX have high hopes riding on the success of the mission. NASA could use a win to validate its competitive procurement approach and SpaceX would like to start delivering cargo under its NASA CRS (Commercial Resupply Services) contract. Until cargo is delivered, SpaceX doesn't get paid -- a far cry from most traditional government space contracts.