Kdjykuj

1 1 $begingroup$ I was reading about gravity assist and I read that both the voyagers used gravitational force of these planets to speed up. But I wanted to know why weren't they completely attracted by their gravitational field? One thing I thought about it was that the escape velocity of these planets were known to NASA and these space crafts used the propeller fuel to escape but how did NASA calculated escape velocity? $$v_{escape} = sqrt{frac{2GM}{R}}$$ But how could they predict mass? Radius I guess can be predicted by parallax method. jupiter gravity-assist flyby escape-velocity uranus share | improve this question edited 30 mins ago ...