(CNN) -- The countdown has been aborted for Tuesday’s launch attempt of private spaceflight company SpaceX’s latest resupply mission to the International Space Station, NASA said on Twitter.
The focus in the buildup to the launch has been on SpaceX plans to try to land the Falcon 9 rocket’s first stage on a floating platform for the first time.
The next possible launch attempt is at 5:09 a.m. ET Friday, NASA said, “pending resolution of the issue.”
It did not specify what the issue was.
Traditionally, rockets have been designed to fall back to Earth after separating from the spacecraft they lifted, and then burn up on reentry or crash into the ocean. The millions of dollars that go into the production of the rockets burn, too.
SpaceX wants to pioneer a reusable rocket, a development that could change the economics of space travel.
“A fully and rapidly reusable rocket—which has never been done before—is the pivotal breakthrough needed to substantially reduce the cost of space access,” SpaceX said in a news release.
The company has twice attempted soft landings of the Falcon 9’s first stage on water. Those tests showed that the rocket is capable of reducing its speed from hypersonic to nearly zero, and deploy landing legs.
In those tests, the rocket tipped sideways and crashed into the ocean, causing damage that made the rocket unusable. That was according to plan, SpaceX said.
When the launch happens, the company will try the same soft landing for the Falcon 9’s first stage, but this time on a custom-built floating platform it calls the autonomous spaceport drone ship.
Landing on the platform “is significantly more challenging” than the water landings, the company said.
For one, the platform is not anchored, and while it looks large from the ground, it is a rather small target for the 14-story-tall rocket.
SpaceX described reentry and landing as “trying to balance a rubber broomstick on your hand in the middle of a wind storm.”
The company puts the odds of success at 50% at best. It adds, however, that this is just the first of a number of tests toward the goal of landing a rocket stage for reuse.
As for Tuesday’s target, “X” marks the spot: The company will try to land the rocket stage on the SpaceX logo painted on the center of the floating platform.
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