# Just how much can tall skinny rockets bend? (roughly, safely)

Below is a GIF I prepared and used in an earlier question, and the answer seems quite reasonable. With a height to diameter ratio of about 70 m to 3.7 m (nearly 20:1) a weight-conscious design, focused primarily on withstanding axial stresses (e.g. thrust + drag), and allow for some flexing.

But if it bends this much in a breeze, what about in flight?

This answer references the detailed, knowledgable Flightclub simulation of a recent Falcon 9 launch. At one point when the speed of the rocket (wrt Earth's rotating frame presumably) is about 1000 m/s and the pressure must be roughly 0.06 or 0.07 bar at 22km altitude, the angle of attack is estimated to be 4.6 degrees. That would present a crushing-type force, but would it tend to bend the rocket since the fairing is so much wider than the body?

Just how much can tall skinny rockets bend? (roughly, safely)

• Are you asking specifically about how much the rockets can safely bend without breaking (if, say, a giant flying gorilla were to grab and bend them in mid-flight), or about how far they would be expected to bend under typical flight stresses (i.e. assuming no giant flying gorillas)? Apr 5 '17 at 15:46
• @IlmariKaronen I want to remain a little flexible (pun intended) so as not to prevent an informative answer from being posted. This particular question is asking for fairly specialized knowledge, and if I over-specify, someone may just choose not to post. I have a strong feeling that since rockets are such highly optimized designs that strive to minimize structural weight, the expected limit and the safe limit are not so far apart from each other.
– uhoh
Apr 5 '17 at 16:02
• Hmmm - is it definitely bending, or is that movement inline with tolerances of the clamp mechanism? Apr 5 '17 at 18:00
• Related: shuttle stack twang: youtube.com/watch?v=ExfjSuJxOP8 Apr 5 '17 at 20:33
• Related: bendy Saturn V: m.youtube.com/watch?v=PnsFFhKqXXo Apr 11 '17 at 15:11