The original way to get the deep impact achievement was you fly really far out and fly into the planet at very high speeds. I tried to do it that way and it didn't work so I found this other way that worked well for me.

If the original way didn't work for you. You should try this alternate way. This ones a little bit harder but it works a lot better, at least for me anyways. What you have to do is you land on a certain island with all of the arches. Once you land on the island on the landing pad you just wait until a tornado pics up the island and throws it into space. Once in space you have to cram your ship bellow the lowest point on the island. Once the island falls back to the ground it will push you through the current and it will give you the achievement. That concludes this guide. If you liked it consider giving it an award and a thumbs up.