# Minimum range to which an ICBM can be launched **URL:** \ **Category:** Factual Questions\ **Created:** [July 5, 2016, 3:14am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107 "2016-07-05T03:14:35Z")\ **Posts on this page:** 7\ **Page:** 2
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [July 6, 2016, 2:59am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/21 "2016-07-06T02:59:59Z")
> [@pieceoftheuniverse](#): > > Wait, wait, wait. Are you telling me that the heart-wrenching climax of [Iron Giant](http://www.imdb.com/title/tt0129167/?ref_=nv_sr_1) couldn’t actually happen? > > Or am I remembering wrong, and that wasn’t an ICBM they launched? 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](https://en.wikipedia.org/wiki/USS_George_Washington_(SSBN-598)) 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. ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [July 6, 2016, 3:28am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/22 "2016-07-06T03:28:52Z")
> [@joema](#): > > Solid rockets can be both throttled (statically) and shut down early, and this is commonly done. > > The throttle schedule of space shuttle SRBs can be seen in this thrust/time graph. The SRBs throttle back in a predetermined sequence to reduce dynamic pressure in the thicker lower atmosphere, then later throttle up. This schedule is fixed at manufacturing time: > > [Space Shuttle Solid Rocket Booster - Wikipedia](https://en.wikipedia.org/wiki/Space_Shuttle_Solid_Rocket_Booster#/media/File:Srbthrust2.svg) > > Solid rockets can also be shut down via thrust termination ports, which are used on the Minuteman III 3rd stage and was used on some Titan III SRBs. Forward-facing exhaust ports are opened in the motor case which depressurizes and quenches the combustion process. This was evaluated for the space shuttle SRBs and found feasible but it would have required structural reinforcement that adversely impacted payload capacity, so was not implemented. > > Solid rockets can have extreme steering ability, as demonstrated by this Sprint missile turning sharply while accelerating at 100 g: [http://williamson-labs.com/images/000102m0.jpg](http://williamson-labs.com/images/000102m0.jpg) 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. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [July 6, 2016, 11:37am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/23 "2016-07-06T11:37:55Z")
> [@bump](#): > > …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… 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. ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [July 7, 2016, 3:32am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/24 "2016-07-07T03:32:30Z")
> [@joema](#): > > 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](https://en.wikipedia.org/wiki/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. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [July 7, 2016, 4:08am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/25 "2016-07-07T04:08:39Z")
I happened to visit the White Sands Missile Range museum today, where an [Athena rocket](http://www.wsmr-history.org/AthenaAction1.htm) ([more info here](http://www.astronautix.com/fam/athnartv.htm)) 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](https://en.wikipedia.org/wiki/Green_River_Launch_Complex) in Utah, and the warhead reentered the atmosphere 500 miles away, above White Sands. ---
**Author:** ![joema](https://avatars.discourse-cdn.com/v4/letter/j/a9adbd/32.png) [@joema](https://boards.straightdope.com/u/joema)\ **Post date:** [July 7, 2016, 3:39pm UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/26 "2016-07-07T15:39:27Z")
> [@Hail\_Ants](#): > > The Saturn V’s third stage (actually called S-IVB) was also restartable, though not throttle-able 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. > [@Hail\_Ants](#): > > …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. 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 RD-170: 40%-100% RD-180: 47%-100% SpaceX Merlin 1D: 70%-100% ---
**Author:** ![Hail\_Ants](https://avatars.discourse-cdn.com/v4/letter/h/dc4da7/32.png) [@Hail\_Ants](https://boards.straightdope.com/u/Hail_Ants)\ **Post date:** [July 8, 2016, 2:19am UTC](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107/27 "2016-07-08T02:19:15Z")
> [@joema](#): > > 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. Ok, I though it was only three and the third was with just the RCS thrusters. I read _Lost Moon_, though ages ago (before the movie came out\*!\*) [Previous page](https://boards.straightdope.com/t/minimum-range-to-which-an-icbm-can-be-launched/759107.md?page=1)