It's worth appreciating that 'live broadcast' also includes media off the main networks, so if you watch a SpaceX livestream on YouTube (etc), technically you should have a TV License to do so.
That's not my understanding, unless that spacex livestream is by one of the TV networks.
"A licence is not required to view user generated content, clips and videos on YouTube. This includes live streamed content that is not part of a television broadcast. Or being broadcast at the same time by other means."
"A licence is not required to view user generated content, clips and videos on YouTube. This includes live streamed content that is not part of a television broadcast. Or being broadcast at the same time by other means."
https://www.tvlicensing.co.uk/faqs/FAQ104