The barge, or "autonomous spaceport drone ship" as SpaceX calls it, is scheduled to land its returned rocket on Saturday, about 17 minutes after the planned 4:47 a.m. (EST) launch of a Dragon cargo spacecraft heading to the International Space Station from the Cape Canaveral Air Force Station in Florida.
The point of the barge landing is to recover the rocket's expensive engines and reuse them. Until now, rocket engines have typically been allowed to burn up on reentry or plummet into the ocean, either for disposal or recovery later by boat. If SpaceX pulls off the barge landing, it will be a first for ocean landings.
The barge's landing site, just 300 feet by 170 feet in size (about 90 by 50 meters), will act as the outfielder's glove to catch the massive first stage of the Falcon 9 launch rocket, maneuvered into place by remote control.
"Our main mission is to get cargo to the space station," said SpaceX's Hans Koenigsmann, speaking last week at a NASA briefing. "I'm pretty sure it will be pretty exciting," he said of the attempted controlled landing of the 14-story-tall first stage of the rocket on a flat floating platform.
Failure an Option
SpaceX has successfully landed rocket stages on land, and made a controlled landing on water after a past cargo launch, which still led to the loss of the rocket stage in the drink. Musk has previously suggested that barge landings of stages would expedite their reuse, leading to cheaper rocketry.
Musk gave 50 percent odds of the barge landing working out. ("I pretty much made that up. I have no idea," he added in a recent web chat on Reddit.)
Koenigsmann, the "mission assurance" chief at SpaceX, called the barge landing attempt "extremely challenging," and did not express undue optimism about it working on a first try. The Dragon launch is the fifth of 12 cargo resupply missions that NASA has contracted for with SpaceX at a cost of $1.6 billion.
Even if the barge landing is successful, don't look for rocket launch costs to drop much, says space economist Henry Hertzfeld of George Washington University in Washington, D.C. Rocket engines are responsible for only about a third of launch costs, he says, and refurbishment might eat up any price savings from reusable ones.
For now, weather reports give an 80 percent chance that the Saturday cargo launch and rocket landing attempt will go forward, although the cargo spacecraft's launch window will be open only for a moment for the trajectory needed to reach the space station. That means a delay might push the SpaceX attempt back to next Tuesday.
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