The first privately backed cargo run to the International Space Station is just hours away from becoming reality, but SpaceX and NASA officials aren't taking anything for granted as the clock ticks down to Saturday's scheduled liftoff of a SpaceX Falcon 9 rocket carrying the company's Dragon capsule from Cape Canaveral in Florida.
"We have not hit a T-Zero yet," SpaceX president Gwynne Shotwell told reporters Friday, according to Space.com. "However, our team learns more everyday about this vehicle. I'm going to give myself a better than 50-50 shot of lifting off tomorrow, and if we lift off I believe we'll make orbit."
For now, everything seems to be falling into place for the scheduled 4:55 a.m. ET liftoff from Launch Complex 40 at the Cape Canaveral Air Force Station.
The Dragon's computer systems have checked out following a longer-than-expected software validation process that delayed the mission's earlier May 7 launch date. Other technical issues that have caused months of delays to the first commercial flight to the ISS have also been resolved.
And the weather appears to be cooperating as the countdown to T-Zero approaches. Weather forecasters are predicting a 70 percent chance of good conditions at the launch site in the wee hours of Saturday when the Falcon 9 booster will begin fuelling and then blast off into orbit carrying a cargo-laden Dragon spacecraft, according to Space.com.
But Shotwell noted that SpaceX has never managed a liftoff of a Falcon 9 on the very first try. In fact, SpaceX has only launched its current booster rocket once before, on a December 2010 test flight that carried a Dragon capsule into orbit and back again as part of NASA's Commercial Orbital Transportation Services (COTS) program.
SpaceX and NASA are calling Saturday's launch a test flight as well. The goal of the mission is to ferry 1,150 pounds of cargo aboard the SpaceX Dragon for delivery to the ISS and then the take on a 1,455-pound payload to bring back to Earth.
If SpaceX can pull that off, the mission will be a roaring success, but Shotwell and others cautioned that each phase of what could be a 75-hour trip to the ISS must be successfully navigated to move on to the next.
Just lifting off is the first goal. If Space X misses its window on Saturday, the next launch opportunity won't come until May 22, Space.com reported.
Successfully inserting the Dragon capsule into orbit is the next step, at which point SpaceX technicians will attempt to synchronize the Dragon's orbit with the space station's by Monday and then seek a green light from NASA to dock with the ISS on Tuesday if the Dragon passes a systems check.
Next Up, Manned Missions
Saturday's launch is an unmanned test flight, but SpaceX, run by PayPal and Tesla Motors co-founder Elon Musk, also plans to conduct manned flights to the ISS by 2015 as part of NASA's Commercial Crew Development (CCDev) program.
Since ending its storied space shuttle program last year, NASA and other international space programs have relied on the Russian space agency to ferry crew to the orbiting space lab. Seeking alternatives, NASA has been working with private companies like Hawthorne, Calif.-based SpaceX to develop commercial spaceflight for manned missions and space exploration ventures conducted by robotic probes.
SpaceX has both COTS and CCDev contracts with NASA to develop an astronaut ferry service to the ISS. The company conducted its first COTS Demo Flight 1 mission a little more than a year ago, launching a Dragon C1 capsule atop a Falcon 9 rocket on Dec. 8, 2010, inserting the Dragon C1 into orbit, and recovering the capsule to become the first privately funded company to successfully complete the orbital insertion and recovery of a spacecraft.
Last week, SpaceX announced plans to offer trips to private space stations someday (see the results of a related Space.com survey below). The proposed foray into space tourism, a joint venture with Bigelow Aerospace (BA), is a good deal more ambitious than the simple fly-by sub-orbital flights being planned by the likes of Richard Branson's Virgin Galactic enterprise.
The two companies plan to kick off an international initiative to explore interest in the space experience that will allow consumers to travel into space in SpaceX's Dragon spacecraft and then spend time in Bigelow Aerospace's BA 330 habitat.
"SpaceX and BA have a lot in common. Both companies were founded to help create a new era in space enterprise," Shotwell said last week. "Together we will provide unique opportunities to entities—whether nations or corporations—wishing to have crewed access to the space environment for extended periods."
For more on recent privately funded space-faring news, see: Colony on Mars? SpaceX Preps for Red Planet Living, SpaceX Breaks Ground on Vandenberg Rocket Launch Site, and: Planetary Resources Aims to Mine Asteroids for Water, Platinum.
For more from Damon, follow him on Twitter @dpoeter.
