This guy [0] does it with regular solid fuel rocket motors. Since the engines cannot be throttled, I think he has to try and light them at just the right moment

This guy [0] does it with regular solid fuel rocket motors. Since the engines cannot be throttled, I think he has to try and light them at just the right moment, which does not seem particularly easy... [0] https://www.youtube.com/watch?v=8_hJ48LCXWs https://www.youtube.com/watch?v=8_hJ48LCXWs