Yeah, for those keeping score the sub they contacted at the end of Iron Giant was the USS Nautilus, which was the first nuclear powered sub, but it had no capacity to launch missiles, nuclear or otherwise. The first such vessel was the USS George Washington in 1960. Still a great film though.
This whole thread is kind of moot. There would never be a need to ‘short target’ an ICBM. The US (and Russia) have no lack of short and intermediate range nuclear-tipped missiles. In fact, since these are tactical, not strategic, weapons we probably have more of them than ICBMs and more widely deployed (i.e. accompanying every major battle group) throughout the world.
That’s definitely cool stuff (wasn’t aware of the thrust termination ports), but you’d still have to have those capabilities designed into the ICBM from the start; it’s not like you can just burn at half-throttle like you could with a liquid-fueled ICBM- to a large extent, it’s still going to fly a pretty fixed profile flight.
Most liquid-fueled rocket engines are not throttleable – they are fixed thrust. They are also generally not restartable. It takes a lot of design effort and added complexity to make a throttleable liquid-fueled engine, and more effort to make it restartable. I don’t think there has even been a throttleable liquid-fueled ICBM.
The first ever throttleable liquid-fueled engine was the XLR-99 on the X-15, the Apollo Lunar Module descent engine was throttleable, and the space shuttle main engines were. Most other rocket engines are fixed thrust.
The Saturn V’s third stage (actually called S-IVB) was also restartable, though not throttle-able. And the Lunar Module’s descent engine must also have been restartable as they fired it twice during Apollo 13 (once to put them back on a free-return trajectory, then again to do a mid-course correction & to speed their return to Earth). They only showed the second burn in the movie.
I happened to visit the White Sands Missile Range museum today, where an Athena rocket (more info here) is on display. This rocket was designed for testing ICBM warheads, by achieving a similar reentry speed without having to fly thousands of kilometers. They were launched from Green River Launch Complex in Utah, and the warhead reentered the atmosphere 500 miles away, above White Sands.
The S-IVB could be restarted one time. Since it used cryogenic propellants (which do not ignite on contact) this required a single-use hypergolic restart cartridge, used for the trans-lunar injection burn.
The Apollo 13 LM descent engine was fired three times, but had no real limit on number of restarts since it used hypergolic propellants. The three burns were at the following Mission Elapsed Times:
61:29:43: Midcourse correction to place spacecraft on a free return trajectory
79:27:39: Trans-earth injection “speedup” burn
105:18:19: Midcourse correction to adjust reentry angle
In addition at 137:59:52 there was a fourth LM-provided midcourse correction to fine-tune the reentry angle, but using the RCS thrusters.
So just being liquid fueled doesn’t mean an engine can be restarted or throttled. It has to be specifically designed for restarts, which is especially difficult for cryogenic engines. Re throttleability, this is even more difficult and imposes significant technical complexity and some flight risk. On the space shuttle one of the most likely failure modes (which fortunately never happened) was a stuck throttle, where the engine throttles down and won’t throttle back up. Hence there must be an outstanding mission requirement for a throttleable engine, and to my knowledge no liquid-propellant ICBM has ever had this.
Among throttleable liquid propellent engines, the throttle range also varies widely. The wider the range the more difficult to implement and the more likely a throttle malfunction or combustion instability.
Throttle range as a % of full rated thrust:
Space Shuttle SSME: 67%-109%
Lunar Module descent engine: 10%-65% and 95% fixed thrust
X-15 XLR-99: 30-100%, but %30-%50 was unreliable and rarely used