PROMETHEUS spacecraft is really FAST

Not sure if anyone addressed this but according to Albert Einstein the problem with traveling at light speed is that time passes differently for the folk back home than it does for the crew. Someone had mentioned that it would have taken seventy earth years to get to one of the LV's. But I've read that the theory of a warp drive is that by warping the space around the ship you can somehow curtail the differences in passing time so that a three year voyage traveling with a warp drive would be closer to three years back on earth. It's crazy but scientist actually believe that one day we will be able to do this. All the people here may never see this but give us another hundred years(providing we don't destroy ourselves first) and our great-great-great- grandchildren may be vacationing at the a Disney Resort on one of the LV planets. I'm sorry if someone had already mentioned this, I didn't read all the comments and I'm sorry if my science isn't right because I got most of it from a Discovery show and a show about Star Trek tech. But not bad for a house painter I thought!

Yes, but in the Alien universe their FTL causes time expansion, not time dilation, right?

This explains why they have to be in hyper sleep.  If they were not, the subjective duration of their voyage would be decades, while to an outside observer, only about 2.5 years would pass.  It doesn't matter for David, because he does not age. But the rest of the crew would age tremendously. And the faster they push their FTL, the longer their subjective duration is. That is what keeps an upward boundary on how fast they can go.  Even asleep, their ship can't sustain them forever. As I understand it, that was also the reason that Ripley's daughter only aged at a normal rate while she was asleep on the Nostromo.  But when Ripley went into hypersleep aboard the sublight lifeboat, she did not age, while her daughter aged another 65 years or so and died of cancer before Ripley could ever see her again. 

FTL time expansion makes it a lot easier to explain the Alien universe and its passage of time. It keeps the problem of aging confined to the ship's crew, rather than applying to all of the outside observers, and pretty much lets everyone age almost in parallel, although I guess if you spent all of your career in hypersleep, you would age less than everybody else. 

You have that the wrong way round. On a very fast moving ship (let’s say 99.99% the speed of light), the occupants would age very little from our perspective. From their perspective, we would age much more quickly. It’s the classic Twins Paradox in relativity. A twin who travels very far very fast will come home to find his sibling long dead.

We don’t know how quickly the Narcissus was moving with respect to Earth, but it was described as “drifting” at the start of Aliens. So maybe time dilation didn’t play much of a part in Ripley’s ageing process. It’s quite possible that the hypersleep chamber, the “old freezerinos” just slowed down her metabolism to next to nothing. 57 years in chill might not be that long.

By the way, there’s no such thing as time expansion, but time dilation is very real.

Well i could NOT have PUT it any better than HOX has, as that was the same as my Reply would have been...

As FAR as the Prometheus goes it was Traveling at about 19X the Speed of Light, as we go on in the Franchise then Ships Get Faster..... the Nostromo could Travel at 47X the Speed of Light.  The Sulaco like 780X (give or take).

The Covenant  about 33X the Speed of Light.