Elon Musk has revealed the reason why the Starship 2nd stage blew up just before reaching orbit during the last test.
Elon says they wanted to simulate a live payload and the way they did it was by filling the 2nd stage with additional liquid oxygen to increase the ship's weight. And then they wanted to dump the liquid oxygen as they're getting into orbit as they needed to lose the payload before re-entering the atmosphere but as they started venting the liquid oxygen, this started a fire which led to the explosion.
To prevent this, on the next Starship test instead of filling it with a liquid oxygen payload, they are going to put an actual payload on it, whatever that means and Elon says he's very confident they will be in orbit this time