# Bounce off the atmosphere at reentry?

I am just watching Space Race part 3 and the cosmonauts just got their first view of Wostok. The scientist who designed the retrorockets told the soon-to-be spacemen that the rockets would have to be fired precisely in order to not:

1. reenter too steep (hence to fast) and crash or
2. reenter too shallow and bounce off the atmosphere into a higher orbit

The first point is, of course, well taken (even though one has to wonder why the rockets should be designed with too much power in the first place), but the second point seems dubious to me: After playing KSP, I would suspect that the Wostok's orbit would decay nonetheless after even a minimal braking. How could you enter a higher orbit by touching the atmosphere? That would seem like a great way to get to the moon, after all.

• A capsule can actually skip off of the atmosphere the same way a stone skips off the surface of a pond. See this question for more explanation. – Miles Budnek Dec 7 '16 at 5:05
• It is not necessary for the rockets to be overpowered in order to effect a re-entry that is too steep. Just aim closer to the center of the cosmological object (presumably, Earth) than an ideal reentry point as you approach, and you'll succeed in destroying your spacecraft. In fact, the more overpowered the rockets are, the better your chances of surviving in a too-steep re-entry; you can use the rockets to shed speed before your heat shield burns away, and try to slow to a speed that won't rip out your craft's parachutes (or blow your impact cushions, or whatever) as you reach the surface. – jaxter Dec 7 '16 at 5:23
• So, it's another power-to-weight tradeoff problem, best solved by coming into the descent just steeply enough to ensure the atmospheric drag slows your craft to the point where it is not going fast enough to re-emerge from the atmosphere, and not much more than that. – jaxter Dec 7 '16 at 5:25
• @MilesBudnek I was thinking a lot about the lifting body effect, lift could obviously alter the trajectory in a way that drag alone couldn't, the question is if lift could in any sense of the word "raise" the orbit, I get the feeling that an encounter with the atmosphere strictly lowers apoapsis. Lift would have a significant effect on how hard the capsule "bites" into the atmosphere, as depending on angle of attack lift effects can exert an upward or downwards force on the capsule, pushing it deeper into or lifting it out of the atmosphere and thus altering areobraking efficacy. – Blake Walsh Dec 7 '16 at 9:20

• +1 For me at least, this is a better explanation of what the often-heard phrase "bounding off of the atmosphere" really means. – uhoh Feb 23 '18 at 1:03