I did it in that time. Act 3 ended up being super rushed because of it. I dropped the pirates totally and it just turned into a scramble with the survivors trying to destroy the ship and escape before it detonated. In my case I didn't have a choice. It was a test run of Alien between regular sessions of another campaign so I only had one session to do it. My players really enjoyed it though so it worked out. Basically Act 1 and 2 took about 2 hours each and then Act 3 was very much "RunRunRunIt'sRightBehindUsRun!!!!" And it worked well.