A boomer patrol is 70 days. All submerged. Longer sub voyages, especially by SSNs have happened. The longest I could find via Google is 111 days. A sub is limited by it’s food supply. Unlike Capt. Nemo and the Nautilus, they can’t send out hunting parties. 
Though there are stories of crab dinners, from boats like USS Parche…
I didn’t know if there was some unintentionally long patrol that was kept quiet. Something like it’s the end of the cruise but, e.g., the Soviets are playing games for the next two weeks, and you’re the only boat in the area.
I thought Triton’s voyage was longer than 60 days, but I guess not. 111 days sounds really unpleasant.
Any amount of time on a submarine would be unpleasant. Only the very worst people are cast down into the depths of the ocean, banished from receiving the sun’s rays until such time as better men and women deem it proper for them to come to the surface again. That’s why they’re called sub-mariners. Proper mariners would be up top, basking in the warm light. 
Exactly. A nuclear submarine is limited only by its food supply (assuming nothing breaks onboard that the crew can’t fix). They can distill water from seawater, and produce oxygen by electrolysis as long as they can keep the reactor going, and modern nuclear submarines carry enough fuel to last decades.
I’ve personally been continuously submerged for something like 4 months when I served on a fast-attack submarine. After some R&R and loading up of food supplies, we then went right back to sea for another 2 months. FWIW, at the end of the 4 months when food stores were getting low, meals were getting a little weird, like chili mac and beets.
If you removed the missiles on a ballistic missile submarine, I’d bet you could load enough food onboard to last for years.
It’s not always sunny on the surface. I’ve been through hurricane-force storms in the North Atlantic. They’re a lot easier to ride out a few hundred feet below the surface. Any ship on the surface in a storm like that would have likely become a submarine, too…at least once, anyway.
So let me understand: “into fire”: everything on the Earth’s surface is immolated. So you have to survive underground for centuries, and then re-establish a breathable atmosphere above ground while also attempting to start plants growing again? Sounds like a massive undertaking. Not to mention, what effect is this impact going to have on day length, axial tilt (seasons) and (subtly) orbital eccentricity? These are all important parameters that can fuck up livability if they go too far out of spec.
How far out would need to spot something of that size to deflect it? I’m pretty sure that the ‘split it in half’ plan isn’t going to work for something that size.
As large as it is, you are going to have to apply a lot of force to have any affect at all, right?
Or a fairly small amount of force - relatively - applied VERY long before potential impact.
Honestly, one of the easiest solutions is to just shove it to the side a bit and let the laws of motion take care of things. But you have to be way ahead of the game for such to work.
I think the one that killed the dinosaurs was 6 miles across and it heated up the earths atmosphere for a while. However it seems to have only been for a few minutes.
IT doesn’t have to be a 500 km meteor.
We have never made a self sustaining biosphere that contains more then 3 species. Our spacestations are a moldy unhealthy mess. Biosphere 1 and 2 turned into a sour rat and cockroach infested hell and still needed oxygen pumped in so the people can survive. We would need inputs besides energy to our closed environment. A lot is going to depend on what else we can get from our damaged environment.
Another thing you didn’t include in your list of things is the will to live. Without that depression and worse will tear at the health and mental well being of the vault dwellers.
Perhaps, I do recall they do have plans as to fighting a war with a intersteller species which is vastly superior and devastates any command and control of the government, which was to detach and head into the wilderness areas, or where-ever they can, and act as guerrilla groups to act to discourage they staying, hoping they will leave, then reform the military. So if they came up with that, I’d say they would easily have plans for something that we could cause (using nukes instead of the astroid strike.
You know, I really wanted to like Seveneves because it was a great concept but yeah, the book as written is pretty terrible.
As a person who see the repairs on nuclear ships including aircraft carriers, I can tell you that there are many things the crew is not able to fix. Now if they were all that was left, their make-shift repairs would have to do.
A nuclear sub can stay underwater for several months. The food and a few other (classified) supplies are the limiting factors.
I think the only viable power supply for living underground if the surface is too hot for humans is nuclear power. If an impact is going to affect the surface that much, then it think it is reasonable to believe that the air will be too contaminated with dust and ash for diesel generators to work.
Given enough advance warning, an underground refuge could be made, but there is still the problem of a heat sink for the nuclear reactor if a steam plant is used to generate electricity. I suppose a cooling tower could be used, but if it fills with ash or dust, then is stops working. Any suggestions?
According to this article, while the dinosaur-killing asteroid caused a brief period of intense heating, the longer-term effects were cooling as dust and soot blocked the sky for a long time.
So if we’re worried about that sort of impact, there’s a good chance that humanity would survive. You don’t have to stay in a submarine or underground bunker for years, just long enough to ride out the heat wave. After that, sure, it’s harder to farm, but not impossible. And you have a nuclear reactor to power lighting and plenty of ocean life to draw from. Head to the tropics and repopulate.
But look here, Dr…
Let’s see. First we burn all the topsoil to cinders, along with all the soil life in at least the top few inches, and all of the pollinators.
Then most of the light is blocked off by dust and soot in the air; which also settles on and blocks the essential breathing pores of anything you’re trying to grow.
All the rainfall patterns, and most of the wind patterns, are also going to be knocked entirely out of whack.
I sure wouldn’t expect a crop of much of anything under those circumstances.
Life did return to the planet’s surface after the previous episodes. But the recovery time’s now thought to have been millions of years. I really don’t think we’d be able to just pop up to the surface and set up successful farms as soon as the heat level died down.
What about the tsunami? Of course estimates vary but some talk about a mile+ in height.
Is your bunker far enough away and high enough altitude to avoid the tsunami and it’s affects? Sure, you might be in a tight sealed bunker. But once the tsunami gets done maybe there’s a bunch of debris covering all your exit doors.
(Of course if the meteor hits your bunker, it’s all over.)
Any viable underground habitat capable of providing a home for even a few hundred people for the time it would take until the return to the surface is possible, even if only a few years, would cost billions and billions or trillions of dollars and would be improbable to be kept secret, for the time it would take to build the thing. If we had enough time and money to do such a thing it would be better spent diverting, or trying to, the asteroid. Which also is highly improbable, we are unlikely to be allowed the advance notice. And in spite of all the fantasies, we are nowhere close to having the technology to divert an asteroid. Not even close. Not even a small one.
The issue is time. We are unlikely to get much, certainly not enough to devote the entire resources of this planet to the problem.
And for all those who think that* surely* the government has thought of this and is planning accordingly. Like the movie Deep Impact. Have your worked within the government? Dealt with the entrenched bureaucracy? Believe that the best and smartest people are working for the government and protecting you?
All I can say is don’t call me Shirley.
The bunkers already exist. They are called “decommissioned nuclear missile silos.”
Some people have remodeled them into comfy homes. A group of investors was trying to develop luxury condos with stores, a swimming pool, and ultra mongo security.
Sort of Doomsday Preppers on steroids with lots of money.
~VOW
Pfft, anything short of mega ultra mongo security is a waste of money.
Those are all really good points, but I think it’s still easier to stay alive on the surface than in a bunker. Rainfall patterns will change, but it will still rain. Most of the light being blocked by dust and soot is better than all of the light being blocked by a submarine hull or earth above your bunker, etc. I have no idea if the problems would be surmountable (and of course there’s a whole range of different scenarios to consider).
Can you provide a cite for the millions of years to repopulate the planet’s surface claim? I’m not disputing it, I’ve just had trouble finding much in the way of hard numbers on anything.