I loved this game! I'm an MSc aerospace engineer so any game related to the space topic is a hype to me. I really liked it, the game flow is great, I did no see programming bugs and the UI functionality was fine.
I do not believe you need to improve this "trial and error" thing, I think the game is just right in its difficulty and you have to play around to see how gravity and mass are affecting your ship movement. What you can do, is add a very short tutorial explaining to people how gravity works. Obviously, my opinion is biased becuase I know pretty well how gravity should work and to me it was no difficult to figure out the game.
Regarding gravity physics, I didn't get the right sensation. Why the asteroids that are so small pull so much of the ship? It really felt that the asteroids pull was very similar to the planets gravitational pull. This does not make sense to me, as obviously bigger volume usually mean bigger mass (unless they're very very gassy planets). I got a similar sensation with the black hole (too low pull compared to asteroids for such a big size), I think that right now the gravitational pull of other objects to the ship is not well balanced.
Also regarding the black hole, I could observe that the ship warped its shape when nearby it, that's a nice one, well done! Finally, I missed that you showed in which level you were during the gameplay. I was playing around and passing levels, but had no idea if I was on Sector A,B,C or D, or if I was within the sectors at level1, 2 and so on.
Overall an amazing game that needs to be polished at some points. Looking forward to seeing more of it and that you create a mobile game :)