Sparks and clouds of exhaust and vapor issue forth from SpaceX's Falcon 9 rocket during a static fire test at Cape Canaveral Air Force Station on Monday.
SpaceX has suggested May 19 as the new date for its potentially history-making Falcon 9 rocket launch to the International Space Station, with May 22 as a backup date.
The schedule shift provides more time for NASA to review changes in the California-based company's flight software, and also avoids a potential conflict with the planned May 14 launch of three new space station crew members from Russia's Baikonur Cosmodrome in Kazakhstan.
If SpaceX's demonstration mission is completely successful, it would represent the first commercial flight to the space station. The flight plan calls for the company's robotically controlled Dragon cargo capsule to conduct a series of maneuvers near the station, starting two days after the Falcon 9 lifts off from Cape Canaveral Air Force Station's Launch Complex 40 in Florida. If all those maneuvers go as planned, astronauts on the orbiting outpost would latch onto the Dragon and pull it in for a berthing.
About a half-ton of supplies would be unloaded over the course of a couple of weeks, and then the Dragon would be detached and sent back down to a Pacific Ocean splashdown. That success scenario would open the way for SpaceX to start resupplying the space station in earnest, under the terms of a $1.6 billion contract with NASA.
If the Dragon couldn't hook up with the station this time around, another demonstration flight would be scheduled as a makeup test.
SpaceX has received hundreds of millions of dollars from NASA to develop the Falcon 9 and the Dragon as a partial replacement for the space shuttle fleet, which was retired last year. The Falcon 9 had a successful maiden orbital flight in June 2010, and the Dragon made a similarly successful debut in December 2010. The upcoming flight would provide the first opportunity for an actual rendezvous with the space station.
The launch has been repeatedly delayed, primarily due to flight software reviews. SpaceX conducted a successful launch-pad engine firing test on Monday in preparation for a planned May 7 liftoff, but the company and NASA decided to hold off in order to provide more time for the current review.
"SpaceX and NASA are nearing completion of the software assurance process," company spokeswoman Kirstin Brost Grantham said today in an email, "and SpaceX is submitting a request to the Cape Canaveral Air Force Station for a May 19 launch target with a backup on May 22. Thus far, no issues have been uncovered during this process, but with a mission of this complexity we want to be extremely diligent."
Bill Gerstenmaier, NASA's associate administrator for human exploration and operations, also indicated in a space agency statement that the May 19 date was doable.
"After additional reviews and discussions between the SpaceX and NASA teams, we are in a position to proceed toward this important launch," he said. "The teamwork provided by these teams is phenomenal. There are a few remaining open items, but we are ready to support SpaceX for its new launch date of May 19."
Because of the orbital mechanics involved with a space station rendezvous, the Falcon 9 must be launched at a precise time of day, with opportunities coming up only every three days.
The current plan would result in a launch at 4:55 a.m. ET May 19. That would provide an ample time interval after the Russians' launch of a Soyuz craft carrying a NASA astronaut and two Russian cosmonauts up to the station. That mission, which is due for liftoff on May 14 Eastern time and docking on May 17, will boost the station's crew to its full complement of six spacefliers.
More about SpaceX:
- SpaceX chief plans to become spaceflier
- Next steps in the new space race
- SpaceX has a lofty goal: Help save humanity
- CNBC: Elon Musk on why SpaceX has the Right Stuff
- Cosmic Log archive on the new space race
Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.