Meanwhile, the firm's Dragon capsule will head to the International Space Station (ISS) to deliver just over 2 tonnes of supplies and experiments, including a set of robotic legs, romaine lettuce seedlings and microbes brushed off a T. rex fossil.
SpaceX of Hawthorne, California, was supposed to launch this cargo mission – its third official delivery to the ISS – on 14 April. The launch was delayed due to a helium leak in the rocket, but SpaceX officials say the glitch should be fixed in time to try again on 18 April, depending on the weather.
Despite the delay, the news wasn't all bad for SpaceX today: At a press event, NASA announced that SpaceX has signed a 20-year lease on a historic launch pad at Kennedy Space Center in Florida that was previously used for the space shuttles. The deal paves the way for SpaceX to test its next-generation rocket, the Falcon Heavy, early next year.
Currently, the rockets that send cargo and crew to the ISS are discarded. SpaceX hopes to change that. A rocket that can return to Earth and safely touch down for reuse could lower the cost of spacecraft by a factor of 100, according to SpaceX founder Elon Musk. A version of the system could also bring astronauts back from Mars.
It is baby steps for now. On this flight, SpaceX will launch its Dragon capsule on a Falcon 9 rocket fitted with a set of extendable landing legs. The rocket will blast off from Cape Canaveral Air Force Station in Florida, and the capsule should separate from the legged part of the rocket about three minutes later.
If all goes to plan, the rocket should reignite three of its engines as it descends, slowing it enough to survive re-entering Earth's atmosphere. About 10 seconds into the landing burn, the legs should deploy. If the test is successful, the rocket will still land in the ocean and sink to the sea floor.
"The probability of recovering the first stage during this particular test is low," says SpaceX spokeswoman Hannah Post. "SpaceX is getting closer, but it is not likely that we will recover the stage with this attempt." Still, SpaceX should be able to collect data as the rocket comes down to see how well the legs perform.
Even if the rocket landing goes badly, a robot on the ISS will still get its own boost. Among the supplies and experiments aboard Dragon is a pair of legs for the humanoid robot Robonaut 2, which has been lending a hand to astronauts since the final space shuttle mission in 2011. Until those legs arrive, it will just be a torso.
In addition, Dragon will deliver the Vegetable Production System, or Veggie, a plant growth chamber that will test how well red romaine lettuce seedlings sprout in space. The chamber collapses for easy storage during flight and extends to create a "garden" that is about 29 centimetres wide by 37 centimetres deep – the largest plant chamber in space to date. The hope is that such chambers could be used to grow food on longer deep-space missions, or to provide astronauts with some recreational gardening.
Dragon's science haul also includes microbe samples from Project MERCCURI, which asked people to collect and identify microbes in public places such as sports stadiums and museums. Cultures will be grown on Earth and on the ISS to compare how low gravity influences the organisms.
Samples selected to head to the ISS include microbes found on "Sue" the Tyrannosaurus rex at the Field Museum in Chicago and ones collected from John Glenn's Mercury space capsule, Friendship 7, at the Smithsonian's National Air and Space Museum in Washington, DC.
Lisa Grossman, New Scientist