SpaceX Falcon 9 launch
SpaceX’s Falcon 9 rocket lifts off from its Florida launch pad. (SpaceX via YouTube)

SpaceX has launched the same robotic Dragon cargo capsule to the International Space Station for a third time, sending about 5,000 pounds of cargo that includes a bag of goopy green slime.

The slime, provided by Nickelodeon, will be used on the space station to demonstrate fluid flow in zero gravity — and undoubtedly delight youngsters who’ll watch the crew poke, squish, pull and prod the green stuff in future videos.

It’s just one of the dozens of science experiments included on the manifest for SpaceX’s latest resupply mission. Other experiments will build up layers of human tissue through 3-D printing, grow moss as a potential food source in zero-G, and investigate new twists in silica deposition that could improve the performance of automobile tires.

A new docking adapter for future commercial space taxis will be delivered as well, along with more mundane supplies such as food and clothing.

SpaceX’s Falcon 9 rocket sent up the Dragon from Cape Canaveral Air Force Station in Florida today at 6:01 p.m. ET (3:01 p.m. PT), a day after concerns about storm clouds and lightning forced a last-minute postponement of the launch.

Minutes after today’s liftoff, the first-stage booster dropped away and flew itself back to SpaceX’s Landing Zone 1, not far from the Florida launch pad. The second stage pressed onward to put the Dragon in orbit.

This was the second go-round for the booster, and the third trip for the Dragon. The capsule’s previous trips took place in April 2015 and December 2017. Although today’s launch marked the first Dragon three-peat, such reuse is expected to become common going forward — in line with SpaceX’s drive toward increasing hardware reusability and reducing the cost of access to space.

The Dragon is due to rendezvous with the space station on Saturday and will spend about a month in orbit before returning to Earth.

Update for 12:06 a.m. PT July 29: The Dragon was hooked up to the space station on Saturday as expected.

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