why was ripley unable to stop the self destruct

You know honestly i never gave that much thought.I just assumed she ran out of time.

im sure the countdown shows she has at least 30 seconds or so and that's why she starts shouting at MUTHER. if shed missed her window then ok shed be pissed but shed have to accept her doom but accept that at least the xeno would be going with her

I watched the movie back in November and will probably watch it again soon.Will definitely pay more attention.I would suggest possible sabotage but i dont really know about that,the company wanted it alive

yea the company want it alive but id be of the same train of thought as ripley in this situation, f**k the company am gna kill this thing' lol the original starbeast has the alien hanging around the lifeboat so they decide to lure it into the life boat and launch it into space with explosives and blow it up, in alien the same kind of scenario comes up, ripley is headed for the life boat but is cut off and cant get into it so she turns and tries to turn off or at least suspend the self destruct as her plan may have changed. I just think she had more time on the countdown and so should been able to stop the countdown

Time in films is very often ticking in a different pace then in reality. 

Very tru

On a slight tangent, in another thread someone said "why does a towing vehicle even HAVE a self destruct?" In fairness, if a hostile, alien, FTL intelligence shows up and tries to board you, there's still important information on the black box that endangers others. Just a thought.

It's a Weyland operated ship, their mission was "retrieve the lifeform", the self destruct system was probably a safety and/or get rid of all evidence- mechanism if things got out of hand. The Nostromo crew were probably briefed about another function though, like decontamination if risk of extraterrestrial bacteria or something.

its not actually a built in self destruct device I don't think. it is a way to destroy the ship yes but I don't believe that was its main function. to me, if they had a self destruct device it would just be a load of explosives set out about the ship but its the action of turning off the coolant system that blows it up. I could be totally wrong tho. question...when ripley lifts the access panel to the coolant controls and is following the directions on the underside, does it say 'self destruct' at all?i know MUTHER comments on the need to get to a safe distance but that's maybe just due to the concequences of the coolant system being off sor so long.

Gents & Ladies,

To keep with the story.  The Nostromo was an aging tub look at all the issues they had keeping the ship flying when they made the landing.  Plus all the systems that half-assed worked like the lighting system down in the corridors when they were hunting for Jonesy.  

To get he to the self destruct.  The Nostromo has 4 cooling systems that she had to cut off for the self destruct to be engaged.  When she went to turn them back on she was only able to get one fully engaged before the 5 minute timer lapsed.  I would say with the age of the tug and only one cooling system back online (and probably not working at 100% anyways) the engines were at a critical tipping point probably before the 5 minute timer, so it was done at that point.

id go with the aging scenario as ripley clearly shouts that she has turned the coolant system back on which indicates she has turned on the required number of systems but an old bucket like that probably wasn't operating at 100%

it definitely was not caused by MUTHER or programmed by Weyland-Yutani because it would make no sense as to why they would have it so when special order 937 was activated it would prevent the self-destruct from being de-activated thus eliminating the creature.

The real reason had self destruct was because of Dan O'Bannon.He once expressed frustration with Michael Crichton's The Andromeda Strain for taking the easy way out and blowing everything thing up(I've actually never read it myself).But when it came to writing Alien he finally understood why he did that,it was a simple and effective way to end things.

As per the film, once you initiate the scuttle procedure you have 10 minutes to abandon ship.  If you change your mind you must do it in less than five minutes.  Ripley didn't do it in less than five minutes.  The option to over ride expired and the engines have effectively started to meltdown.

There's no big conspiracy or fault in the ship - it did precisely what it was designed to do.

I wasn't thinking conspirscy theory in any way, I was just sure ripley managed to turn the coolant system back on as I believe the time showed she still had a little over 5 mins left but I haven't seen it in a while so could be wrong

As she's trying to push the nuclear heads down, she glances at the timer which says 5:05.  As she goes to flip the levers up it shows the timer again ticking down from 5:00 to 4:59. 

She did not have time left over. Here is an image of Mother's Countdown reaching its end BEFORE Ripley even got to the panel with the levers, followed by a screen shot of her starting to push the levers in WHILE Mother tells her that the option to override has passed. She keeps trying anyway. 

The issue, I think, is that after the 5 minute period, a meltdown is occurring that the cooling system is no longer able to control even if it IS turned back on.

I assume the reason for the destruct being possible in the first place is in the event that the ship needs to be decommissioned/ scrapped. Its something like sinking a dead nautical vehicle.

I think it's probably more to stop it falling into 'enemy' hands.

how was this even a question? She passed the tipping point before finishing the reversal. anyone here familiar with these exploding ecigarettes or phone batteries? It's called thermal runaway

Here, this will explain
http://bfy.tw/9hgr