At 8 km/sec? It would make a pretty flash and you might get some shrapnel into orbit.... ;-) (And the glass would have to be thick....)
It would depend on how large the opening was. A dome shaped glass can be thinner than a flat pane that withstands the same vacuum, just like relatively strong light bulbs can be made of very thin glass because of their globular/tubular shape.
The ship could have a pointy tip at the end of a rod to break the glass, and the rod itself made so it would break off once the ship hit air. The glass could be inscribed with break lines on the inside like a hand grenade, so that it would come apart neatly without bits getting sucked back down the tube before the ship could get all the way out.
Also, the glass break could be helped with carefully timed explosives if necessary...