The planned launch of a SpaceX rocket ship with two NASA astronauts on board, the first return of U.S. astronaut launches since the end of the space shuttle program nearly a decade ago, was called off yesterday (May 27th) with less than 17 minutes left in the countdown because of thunderclouds and the risk of lightning at the Kennedy Space Center in Florida. They will try for launch again on Saturday. The astronauts will be brought to the International Space Station in the Dragon capsule after lifting off with a Falcon 9 rocket, the first time astronauts are being sent up with a spacecraft and rocket built by a private company, Elon Musk's SpaceX,.President Trump and Vice President Mike Pence had both been on hand to watch the planned launch, and Trump tweeted later than he'll be back on Saturday.