SpaceX didn't invent the idea of the reusable rocket, but the private space firm is doing as much as anyone these days to advance the cause of waste-not-want-not when it comes to launching spacecraft into Earth orbit.

Last Friday, SpaceX successfully launched a Dragon capsule loaded with supplies for the International Space Station (ISS), the third official cargo run to the ISS for the company and the first test of reusable landing legs and a steering system on its Falcon 9 rocket during an official mission.

The test run was a milestone in SpaceX's long-term plan to employ reusable, Vertical Takeoff Vertical Landing (VTVL) vehicles for future missions, though it's not clear if the experiment worked.

The idea was to steer the first stage of the Falcon 9 v1.1 launch vehicle down to a gentle splash landing in the sea after separation from the Dragon spacecraft. After Friday's launch, rescheduled several times from a March liftoff date due to glitches and other technical issues, SpaceX founder Elon Musk said the "odds aren't good" that the guided landing test worked, according to Space.com.

At any rate, retrieval of the rocket was made too difficult by rough seas, he said.

"I heard reports of 13- to 20-foot wave heights. It's really pretty crazy out there. In fact, the [retrieval] boats weren't able to get close because of the heavy seas. It's unlikely that the rocket was able to splash down successfully," Musk was quoted as saying by Space.com.

The main purpose of the NASA-backed CR-3 mission to the ISS was a success. The Dragon, loaded with 5,000 pounds of supplies, successfully docked with the space station on Sunday, NASA reported.

Meanwhile, SpaceX this week revealed video footage (below) of a reusable Falcon 9's very first test flight at the company's rocket development facility. The rocket, dubbed the Falcon 9 Reusable or F9R, can be seen rising to a height of about 250 meters, hovering for a few moments, and then descending to a safe, controlled landing on the launch pad.

The current F9R launches with its landing legs already extended, but SpaceX said future versions will have legs that will be "stowed against the side of the rocket and then extending them just before landing."

Testing an actual F9 conducting VTVL activity and the first VTVL experiment on a rocket stage during the CR-3 mission are important steps forward in SpaceX's roadmap for this technology. Over the past couple of years, the company has been testing a reusable rocket design, dubbed Grasshopper, sending the experimental rocket to higher altitudes over time before gently guiding it back down to its launch pad and even performing sideways maneuvers in the skies above the company's South Texas testing site.

"The F9R testing program is the next step towards reusability following completion of the Grasshopper program last year," SpaceX said. "Future testing, including that in New Mexico, will be conducted using the first stage of a F9R as shown here, which is essentially a Falcon 9 v1.1 first stage with legs. F9R test flights in New Mexico will allow us to test at higher altitudes than we are permitted for at our test site in Texas, to do more with unpowered guidance and to prove out landing cases that are more-flight like."

The CRS-3 mission is the third official supply run to the ISS for SpaceX, which completed its first run to the space station in October 2012. The private firm is under a Commercial Resupply Services contract with NASA to fly a dozen such missions over the next several years and has also won major contracts with the space agency for science missions and the development of next-generation manned spaceflight vehicles.

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