The difficulty curve in this game is non-exsistent. Some levels are ridiculously easy in the later parts of the game while others you have to be lucky just to get silver medals.
To get into space really early in the game, buy the rock jet pack and 10K cannon. Fire level with the ground at full power activate the jet pack as close to the ground as possible and then hit a goomba. I got above the screen and I haven't even played for more than a half an hour :P