Just been watching the excellent Alien movie and wondered: why would the Nostromo, an innocuous civilian cargo vessel, have a multi-million-dollar built-in self-destruct mechanism?

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    Because otherwise Ripley could not blow the ship up at the end of the movie to kill the Alien. Not that it worked, she later had to fry it with the shuttle's engine. Oct 2, 2022 at 16:15
  • The destruct mechanism might be extremely cheap. All I see is a plastic sign and a programmatical countdown timer
    – Valorum
    Oct 2, 2022 at 16:25
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    It occurs that a self-destruct mechanism might be useful if the crew is unable to think of any other way to prevent the ship from catastrophically impacting an object such as a planet
    – Valorum
    Oct 2, 2022 at 16:26
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    Any ship is basicallly equivalent to a dinosaur killer asteroid See for example scifi.stackexchange.com/questions/144239/… Oct 2, 2022 at 17:53
  • Plausible deniability? The company were up to some sneaky stuff. Oct 2, 2022 at 17:54

1 Answer 1


Traditionally, during war, cargo transported for war effort is loaded onto civilian ships, mostly. What any navy has in it's inventory, in terms of cargo shipping, is basically for peacetime internal needs or specialized units that are part of naval formations (i.e. ro-ro ships, tankers attached to carrier battle groups etc.)

Those civilian ships would be privately owned and operated for the simple reason that no navy has the resources to take them over and run them; also it usually is counterproductive. For example, merchant cargo vessel has only as many crew members on board as is necessary. Navy usually operates with larger complements compared to civilian crews for redundancy.

[See: Everything You’ve Always Wanted to Know about the Merchant Marine But Were Afraid to Ask]

That being said, merchant vessels are legitimate targets in war if they are operated by the warring state or are required to operate within that state's military structure.

[See: Naval Targeting: Lawful Objects of Attack]

So, to avoid capturing ships and cargo by the enemy, they can be (though this is captain's decision, of course - civilians are not military) equipped with self-destruct to facilitate that desire to avoid capture. (the Wartime Instructions for United States Merchant Vessels does not mention scuttling, just rules for engagement to avoid capture; practical outcome of capturing of a cargo vessel by belligerent was scuttling anyway)

Self-destruct as an installation (because it's not a single device) is rarely encountered as it's quite expensive piece of equipment to acquire and then maintain. This is because such installation is expected to work when needed and only when needed - accidental activation is rather irreversible, and that includes all kinds of damage, up to and including combat-related. And, of course, it is designed to be initiated from single source.

For the most part such devices are not found on commercial vessels for the simple reason that they are not needed - practically every ship can (and historically could have been; we know this happened from many records) be scuttled, that is: intentionally sunk. This always was - and is - achieved by either blowing holes in the bottom of the vessel by brute force (i.e. men with axes and hammers), opening specially installed for this reason scuttling plugs or by placing explosive devices in vulnerable places. In first and second cases this was very dangerous operation, so would be done by volunteers, in the last scenario explosives would be produced and placed just before the actual scuttling.

[As mentioned in "The Grand Scuttle", the scuttling crews would prefer to have explosives to open flood valves - due to overgrowth of barnacles on the outer hull and had to remove any controls of those valves on the open decks on the ships. The opening of the valves on the day of scuttling was done by designated crews and hammers, axes and other tools were laid out next to the valves to do the work as expeditiously as possible. Even with all precautions and days of preparation, 8 sailors were killed during scuttling.]

In terms of Nostromo the self destruct caused a meltdown and subsequently explosion of the power source.[See Emergency destruction system Aboard the_Nostromo]

However, in stark contrast to what I wrote earlier, such self-destruct is neither expensive nor necessarily built-in. The multiple positive-action locks in the ESD installed in the ship make it look complicated and/or expensive, but while it is a very nice solution - very hardware-oriented - it just overloads fusion reactor... CM-88B Bison is a nuclear-powered vessel, and as such the self-destruct, as could be in general in spaceships, doesn't have to be something complicated. Doesn't even have to be a part of the ship's operating procedures - in a pinch it can be "jury-rigged", obviously, because any engineer knows how to intentionally destroy any nuclear device he or she is responsible for, given some time and tools...

In general case of the spaceships there is yet another dimension to all of the above - any space-going vessel can be turned into a kinetic projectile. Or - in words of lucasbachmann in one of the comments to the OP- "Any ship is basically equivalent to a dinosaur killer asteroid".

Though this last one is the only viable reason a cargo vessel would have one, in my opinion, best explanation would be that W-Y Corp. put it in ALL it's vessels in the case of the situation like the one Nostromo encountered. After all, they kind of knew something...

  • This all feels like complete guesswork. Can you offer any evidence to back it up?
    – Valorum
    Oct 6, 2022 at 14:00
  • @Valorum - you want me to source the contracts with US Navy for a ship during WWII, for example? Or some construction plans for a ship that has scuttling plugs and an example of use? What next, proving water is wet? I understand what your request is, but when there is a talk about building a house, no one asks for description how to lay bricks and what is formula for cement...
    – AcePL
    Oct 6, 2022 at 14:27
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    If I asked what the walls of Ripley's house are made of and you said "They're clearly brick because houses in 1942 are made of bricks", I'd have the same issue
    – Valorum
    Oct 6, 2022 at 14:47
  • @Valorum - That's not an argument. What you asked me was rather equivalent of the exchange: Me - here are some buildings; You: how do we know they were built and how? Nevertheless - here, have some sources. Hopefully you'll bother to at least click the links...
    – AcePL
    Oct 7, 2022 at 9:02
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    I think what @Valorum is trying to say is that while this is very logical and well reasoned, "logical & well reasoned" aren't generally acceptable as answers here at SF&F without some sort of in-universe supporting evidence or some sort of statement out-of-universe from a director, writer, etc saying "this is so".
    – FreeMan
    Oct 7, 2022 at 16:08

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