UGM-133 Trident II Altitude

[Pawelk198604]

I wonder what is apogee of submarine launched both American and Russian

What altitude is maximum

[falofonos]

Approximately 1200 km.

[Pawelk198604]

Approximately 1200 km.

Thanks vary much.

[magnemoe]

That is high, would it not be more economical do do something like an gravity turn towards target. Do this then doing suborbital jumps with landers.

[daxter]

That is high, would it not be more economical do do something like an gravity turn towards target. Do this then doing suborbital jumps with landers.

It's an ICBM, economics don't really apply. I guess the purpose is to have as much re-entry speed as feasible to make interception difficult.

[falofonos]

It does seem high, on reflection that may be the maximum achievable altitude, details on the performance of in service weapons seems to be tricky to acquire.

The trident D-5 SLBM apparently reaches around 900 miles altitude during an attack.

One test firing of a trident went off course and traversed the van allen belts, although there's no specifics on how high it went. Could have been anything from 200km to 60,000km.

http://en.wikipedia.org/wiki/Intercontinental_ballistic_missile#Flight_phases

suggests I got my units wrong.

Edited June 5, 2013 by falofonos

[magnemoe]

It's an ICBM, economics don't really apply. I guess the purpose is to have as much re-entry speed as feasible to make interception difficult.

Was thinking fuel economy, saving fuel so you can make an smaller missile. I know they don't expect to shoot many of them.

Going low would also make you harder to intercept as you would has less time from lock on target to impact.

Thinking of it they high angle is probably to increase accuracy, you burn upward in an angle instead of messing with gravity turn. You can not depend on GPS or ground stations during an nuclear war. it also make it easier to use multiple warheads.

Before KSP I would never think of it

[dagothar]

Soviets did have something like this - it was called Fractional Orbit Bombardment System: http://en.wikipedia.org/wiki/Fractional_Orbital_Bombardment_System

Basically, missile would achieve LEO, coast along, then deorbit over the target.

[rdfox]

Ballistic missiles DO use a gravity turn; they're just using it on a suborbital trajectory. The high arc is for two purposes, both mentioned here--it makes for a higher entry speed that results in greater difficulty for the interceptor, and it makes for greater accuracy in targeting. (Accuracy *is* important, even with nuclear weapons, when you're trying to make it a serious counterforce threat; you have to be able to land the warheads close enough to the superhardened missile silos and launch/command bunkers to get enough overpressure to collapse them, and many of them are hardened to withstand a 6000 psi/408.2 atm overpressure.)

These are not, however, requirements--one of the recurring nightmares of American strategic planners is something called a "depressed-trajectory shot," where a submarine a short distance (500 miles or so) from Washington, DC, launches a missile on a low, fast trajectory that sees it in powered flight for a much greater percentage of the flight time than normal. While such a trajectory does cost quite a bit in accuracy, that can be made up for by firing a salvo of several missiles to saturate the area. Flight time from launch to detonation on that shot would be in the range of four minutes, not even enough to detect, confirm, and warn the President to get into the White House bunker, much less evacuate him. It could, thus, easily be used to "decapitate" the US command structure and prevent any form of retaliatory action. (This is why, during the Cold War, we had the "Looking Glass" mission airborne 24/7, and still have Looking Glass aircraft fully crewed and ready for launch from Omaha, Nebraska, 24/7, on a hair trigger to take off and take command of US nuclear forces in less than five minutes. Omaha is far enough from the sea to make a depressed-trajectory shot against it impossible, and once the aircraft is in the air, it's essentially untargetable.)

As a side note, the Minuteman ICBM has a Thrust Termination System on its third stage; all three stages are solid rockets, and the TTS is blowout panels at the top of the third stage which, when blown, will let pressure from the rocket vent out the front as well, both canceling the forward thrust and quickly reducing chamber pressure to the point that the propellant ceases burning. This was intended to increase accuracy on the Minuteman I and Minuteman II (by making sure that the trajectory was perfect); while the Minuteman III uses a liquid-fuel rocket on the warhead bus to fine-tune the trajectory to allow for the use of multiple INDEPENDENTLY-targeted warheads (i.e., warhead 1 goes to Leningrad while Warhead 2 goes to Moscow, by performing a burn after the release of Warhead 1), it still retains the TTS to get on as perfect a trajectory for the first warhead's release as possible, to maximize the delta-V available for use on the other warhead aboard. (It will still use the LFE to fine-tune Warhead 1's trajectory, too, for a further accuracy boost, but the TTS greatly reduces the length of the burn required.)

In short, ballistic missile trajectories are one hell of a difficult set of compromises between accuracy, time of flight, speed on entry, range, and how high you want to take it (a higher apogee means it can be tracked on early-warning radars much sooner, allowing more chance to respond *before* it hits). And, of course, the apogee of all active missiles is going to be classified pretty heavily, despite varying from missile to missile due to the fact that no two would have the same trajectory. However, the 800 miles figure mentioned here sounds pretty reasonable for a modern ICBM or SLBM, at least as a nominal average...