I wonder how long rocket launched from the deck of a submarine needs time to reach the target

[Amram]

https://books.google.ca/books?id=-LGZETtVCiAC&pg=PA220#v=onepage&q&f=false

~20 minutes.

remember, you can orbit in 90 minutes, which means you can cover 180° in lat/lon in 45 minutes, yet targets will generally be closer than your antipode, often considerably so, and in the case of slbm's, they could be close enough that the missile never actually goes suborbital.

[DerekL1963]

https://books.google.ca/books?id=-LGZETtVCiAC&pg=PA220#v=onepage&q&f=false

~20 minutes.

Those are response times, the time from detection of the vehicle to impact. Actual flight time is going to be somewhat longer, moderately in the case of direct IR detection (such as the DSP satellites), potentially much longer in the case of early warning radars (where the satellite must rise over the radar horizon before it can be detected). Figure 65, on the next page of the book you link, clearly illustrates that difference.

remember, you can orbit in 90 minutes, which means you can cover 180° in lat/lon in 45 minutes

That's an orbital trajectory, suborbital (missile attack) flight times will be longer. (Because that flight time of a suborbital missile strike includes the launch phase, during much of which the missile's velocity is much lower than it's final velocity).

Anyhow, as I said above, actual flight time (tube-to-target) is going to vary with range and with the trajectory selected. You can't give an approximation of any value without knowing the range.

[Nibb31]

The upshot is... you could build a bomb using that idea, but getting the stuff to make it go 'boom' .... a bit harder.

It would be so much easier to smuggle a bomb on a cargo ship in a 20-foot container and blow it up before it's inspected by customs.

[Beowolf]

Must be a modern missile then, because under water launched missiles like Polaris only had a range of about 1500 miles.

They started phasing Polaris out in 1972. But I wouldn't consider Poseidon or Trident I modern, either. Actually, our current Trident II design is over 30 years old, and has been deployed for 25. I probably shouldn't even call it modern. It's nearly as old as the shuttle, and I'd certainly never refer to the shuttle as a "modern spacecraft".

Now that I've worked it through, I guess America doesn't have any modern nuclear missiles. A bit sad, but I think I'll focus on being glad we haven't needed any.

[DerekL1963]

They started phasing Polaris out in 1972. But I wouldn't consider Poseidon or Trident I modern, either. Actually, our current Trident II design is over 30 years old, and has been deployed for 25. I probably shouldn't even call it modern. It's nearly as old as the shuttle, and I'd certainly never refer to the shuttle as a "modern spacecraft".

Why wouldn't you consider Trident II "modern"? Why is "modern" even relevant in the first place?

Missiles (like pretty much all real world equipment) aren't the latest iShiny, nor are they like your computer which eventually won't run "modern" software. Shake yourself free of the cultural bias towards the newest and improvedest and shift to a dispassionate engineering point of view - where things are judged by absolute performance, not by relative age or whether or not they're fashionable.

That being said, you've even got the age of the design wrong. The guidance system has already been updated once, and they're fixing to roll out a new one this year. The fire control, navigation, and key elements of the ship system* have all been upgraded multiple times over the years. There's also a re-motoring program that should get rolling in the next few years. The Trident II system out punching holes in the ocean (as we say in the SSBN force) isn't the one that came off the assembly line back in the 90's, there's been a continuous program of upgrades and enhancements.

* Trident II is a weapons system, and you really should consider the functionality of the system as a whole rather than focusing myopically on one component.

[magnemoe]

It would be so much easier to smuggle a bomb on a cargo ship in a 20-foot container and blow it up before it's inspected by customs.

This does not give you an rapid response of an ICBM with the added downside that the ship is likely to be turned away during an war.

we are discussing an 5-20 minutes response time here.

The up front time is likely to be far longer as first you need orders to strike then program the missile. The short time is only relevant if you do an first strike or you have cleared orders and respond to an event like an enemy launch.

The time the enemy has from detecting the launch to impact is another factor, the US has satellites who can detect launches, I assume Russia has too. You need radars to get the trajectory.