SpaceX Nasa launch: When is postponed liftoff and how can you watch it?

Rescheduled windows also at risk of problems from weather

SpaceX Crew Dragon, with astronauts Bob Behnken and Doug Hurley on board is seen from the viewing area after the launch was cancelled due to the weather, at Launch Complex 39A in Kennedy Space Center in Florida (BRENDAN SMIALOWSKI/AFP via Getty Images)

Nasa and SpaceX are set to try to launch a historic rocket once again, after weather spoiled their first try.

The launch is now scheduled for Saturday. The window is set for a slightly earlier time, at 3.22pm local time, or 8.22pm in the UK.

Such launches must take place at specific moments in time to ensure that the physics are able to allow them to successfully get to the International Space Station.

Just as with the cancelled launch, SpaceX will have an "instantaneous window", meaning that they must launch at the scheduled time or not at all.

If the Saturday window cannot be met, then Nasa and SpaceX will try again the following day, on Sunday.

However, official forecasts from the US Air Force 45th Weather Squadron indicated there is a 40 per cent chance of weather getting in the way of the launch on each day.

Any attempted launch will be streamed live on Nasa's official YouTube channel, as well as the various other platforms on which Nasa TV can be viewed.