Spaceplanes tend to have beefier, stiffer parts than normal aircraft, at least partly due to drag-reduction being less of a concern. But they also experience far higher airspeeds during reentry.
Yet I've never heard much, if anything, about flutter, or any other form of aeroelasticity being a problem on any of them. Maybe that's because I don't know much about existing or past spaceplane programs? But still, I'd be interested to know.
I can imagine some candidates for the reason why flutter might be less severe:
- the frequencies are so high and modes so many and so uncoordinated that too much energy is dissipated as heat and sound, leading to simply vibration with no damage.
- the sheer stiffness of the vehicle moves flutter frequency out of reach. (Which sounds rather far-fetched for me)
Hoping to find an answer, I Googled about aeroelasticity of the Shuttle, and got this document. It's rather long, so ATM I haven't drawn any conclusions from it. It would be nice if someone has any background info on what the designers of the Shuttle (which I would guess is the best known spaceplane) faced during development in relation to flutter.