Thursday December 12th - Friday December 13th on KSP-TV!
10mph is actually pretty fast for running into a solid object like a planet or moon. I mean, what happens to your car if you hit a brick wall at 10mph, right? Anything over 10m/s is likely to cause damage even to a fairly robust design, and remember that the more massive a ship is the more kinetic energy is involved in an impact, even at the same speed that a small ship might survive. Take it from someone who crashed continually for 4 straight days as he was trying to figure out the landing process; it just takes practice.