They've done it again.

Space Exploration Technologies launched its Falcon 9 rocket into earth orbit on its inaugural flight today, a key milestone in the startup's plan to take cargo into space once the last of the space shuttles retires.

The two stage, 180-foot rocket left the pad at Cape Canaveral Air Force Station in Florida at about 2:45 p.m. Eastern. It achieved earth orbit nine minutes later. The lauch this afternoon followed several delays earlier in the day including a sailboat that had wandered into an off limits area near the launch site and an attempt that was aborted just seconds before ignition due to an engine related issue.

SpaceX founder (and Tesla CEO) Elon Musk hopes to use the Falcon 9 to compete against United Launch Alliance – a joint venture between Boeing and Lockheed-Martin. SpaceX hopes to use the rocket to power Dragon, a craft that could carry cargo – and perhaps people – to the International Space Station. The Obama Administration wants to rely more heavily on private firms to supply the station.

SpaceX was awarded $3.5 billion in contracts by NASA to deliver cargo to the ISS through 2016. SpaceX's first rocket launch, the Falcon 1, occurred in 2008 after several failed first attempts. The Falcon 1 delivered a Malaysian satellite into orbit last year.

There are several private companies competing for contracts to deliver cargo to both low earth, and geosynchronous orbits for a variety of private and government customers. Some of SpaceX's competitors read like a who's who of the wealthy getting into the space business. Sir Richard Branson's Virgin Galactic has already demonstrated sub-oribtal desires and he has talked about using the technology as an airborne launch platform for orbital delivery.

Amazon.com founder Jeff Bezos founded the very secretive Blue Origin in 2004. Very little is known about the company's efforts, but earlier this year it was awarded a contract from NASA to develop a astronaut escape system and a capsule that could be used for its commercial space program. The company plans its first launch into space in 2012.

Orbital Sciences has a $1.9 billion contract with NASA to provide cargo flights to the ISS. The veteran rocket company plans to launch its Taurus 2 some time next year.

More information and video as we get it.

Photo: SpaceX