Do you really want to fire missiles with nuclear warheads “at point blank range”? I guess they could find a crew for a suicide mission for the Motherland.
It’s not the 1960s any more. Why bother sneaking in a sub as a prelude to Armageddon, if that ever even made sense, when you can send in the nuclear-powered underwater drones, nuclear-powered cruise missiles, accurate FOBS, various hypersonic missiles, etc.?
ETA it is expensive hardware, but it’s not like the following year’s budget will be an issue.
Because those technologies aren’t actually operational today.
Missiles can be lobbed from ~20m underwater and well enough away from the blast zone while still giving only a 5 minute warning to the target. And y’know, at that point the immediate priority will probably not be “track and destroy that submarine !”
So, let’s say you have a missile that can handle loads and has some lift and the flight control surfaces for it. Normally, it would go at ballistic missile speed in a high arc trajectory but now you have it fly in a shallow trajectory. How fast can it go? If you take an SLBM and have it burn pointing up at 5 degrees or so, what will be its maximum speed and average speed over, say, 100km? You could presumably do this with truck-mounted ballistic missiles aiming at targets 10km away. That’s the sort of thing the Soviets would have planned for.
Oh where is Stranger on A Train when you need him…
One thing about the SLBM flying in atmosphere vs flying in space is that the aerodynamic loads on the SLBM should be much greater in the former. It’s going faster, for one, and unlike its normal flight path, it should still be in atmosphere when it’s accelerating much more heavily towards the end of first, and especially second, stage burnout.
For the wiki on the Trident D5, it says that first stage burnout occurs 65 seconds after launch. I don’t know, but I’m guessing that the missile is well out of the atmosphere, and aerodynamic pressure consequently much lower, near the end of that burn.
I’d think maxQ for a sideways flight path would be much greater than its design limits, and there’d probably be a loss of vehicle. There’s probably an altitude below the Karman Line though where atmospheric pressure could be low enough that maxQ would be within airframe design limits. Though stagnation heating might be an issue?
Ravenman hit it with the idea that an enemy’d use much stealthier cruise missiles for this sort of decapitation strike, even if those were slower than this sideways SLBM. Much lower launch signature too, at least thermally, and probably acoustically too.
Although if you want truly stealthy decapitation, besides pre-positioning the warhead on the target, gravity bomb delivery from a stealthy aircraft should yield next to no warning. Which is one reason I think why the Soviets deployed things like Perimeter/Dead Hand.
Like any such question you are not going to get a reliable exact answer based on classified information and I believe classification would enter in to an exact answer. However no reference suggests the standard US SLBM has any special depressed trajectory capability. There are public references quoting 2000km as minimum range of Trident D5, and that probably involves an especially high trajectory, like the very high trajectories of some North Korean long range BM tests where they wanted to limit the provocation of having the stages and delivery vehicle come down out in the Pacific, so launched them on a very high short trajectory into the Sea of Japan. Despite Trident being a more advanced weapon, I see no reason to assume it has a special low trajectory capability: nothing indicates any design intention to use it for surprise short range strikes.
During the Cold War there was actually speculation that the Soviets had nuclear mines they’d deploy in Western waters before a war broke out, though no post-Soviet info confirms this AFAIK. But the Russian development of a long range nuclear Unmanned Underwater Vehicle recently suggests the general idea could have occurred in Russia before.
Soviet nuclear armed cruise missile subs were also viewed as a risk factor for US installations near the coasts, as were shorter (than Trident) ranged early Soviet SLBM’s. SAC largely abandoned bomber bases on the coasts in favor of those in the middle of the country for that reason, more warning time against offshore cruise/BM launches.
That’s right—and US SLBMs have gimbaled nozzles, so they meet this requirement.
I’m going to step back here for a moment and explain my objection to your claims about horizontal rocket flight, lest this devolve into more of a sneerfest[sup]1[/sup] than it already has.
I think you might be conflating inherent stability and other definitions of stability. To wit:
The missile is inherently unstable from the moment it clears the sub. Lacking inherent aerodynamic stability, a finless SLBM’s attitude is uncontrollable without thrust vectoring. The direction of travel itself has nothing to do with whether the missile’s attitude is controllable.
Missiles with enough fin area aft of the center of mass become inherently stable due to aerodynamic forces once they exceed a certain airspeed, yes, but SLBMS typically don’t have fins.
Contrary to your assertion above, an SLBM is not significantly less stable when flying horizontally than it is when flying vertically. In both cases, it relies on thrust vectoring to maintain a relatively constant attitude. A constant, relatively small acceleration like gravity is not a challenge for a thrust-vectoring attitude control system.
I pointed out that ballistic missiles are “flying” parallel to the earth’s surface at apogee and manage not to tumble out of control or tear themselves apart. In response, you said:
Again, you seem to think there’s something about “going up” that provides inherent stability—otherwise, why mention “center of gravity?”
The location of the center of mass is one factor in determining how much thrust-vectoring authority is required to keep the missile pointed in the desired direction. But the missile was controlled with thrust vectoring from launch to apogee, even as the solid propellant burned away and as the stages dropped away, both of which alter the rocket’s center of mass. If your three-stage rocket is controllable with a full fuel load and all three stages (at launch) it’s going to be controllable for the rest of the flight.
It almost sounds like you’re trying to distinguish between axial strength and bending strength. It’s true that a Sidewinder turning at, say, 10 g is going to experience very different loads from an SLBM, and naturally each missile is designed for the loads it will encounter. But at apogee, the gravity vector is perpendicular to the axis of travel, just as it would be any other time the missile is flying parallel to the earth’s surface. And the acceleration of Earth’s gravity isn’t much weaker at 1000 km than it is at 0 km: it’s about 76% as strong as at the Earth’s surface. So no, flying horizontally is not going to automatically tear a Trident II apart.
You must mean “parallel,” not “perpendicular” here. Right?
No, it wouldn’t struggle to maintain control just after launch. The demands on the gimbaled nozzle’s attitude authority under horizontal flight aren’t very different from those demands when flying vertically. The missile is inherently unstable in either case.
I’m not sure what you’re trying to convey here or how you think your example applies to the question at hand. Gimbaled nozzles alone are adequate to maintain attitude control on rockets without inherent aerodynamic stability—who cares if human beings struggle to balance a pencil on end?
The gravity vector is small compared to the other loads applied to the missile. The rocket motor might produce a peak acceleration of 7 g; aero loads can also be very large, and there are bending moments induced by thrust vectoring.
In terms of structural response, gravity is less than 1/7th the “problem” that aero thrust-acceleration loads are. It’s true that a huge amount of energy is required to accelerate to orbit or to escape Earth’s gravity well; are you maybe thinking of that?
No, stability is achieved by thrust vectoring and very fast-acting closed-loop control systems. Again, you seem to think that keeping the center of mass “above” the rocket nozzle somehow makes a rocket inherently stable. That’s just not true.
For some reason, you seem to be ignoring acceleration loads from the rocket motor. Statements like this make me wonder whether you’re using the word “gravity” to mean “all axial acceleration loads.” Is that what you’re doing here?
It’s true that any given SLBM is designed for a particular peak dynamic pressure (max Q). That max Q assumes that, as acceleration/velocity increase, air density decreases. Since an SLBM flying horizontally encounters a near-constant air density, such a missile could easily encounter peak dynamic pressures well in excess of those for which it was designed. (Gray Ghost stated this upthread, and succinctly. Cheers!)
Furthermore, gimbal movements that would be fine below the designed max Q could well end badly if the dynamic pressure is higher than the designers anticipated. I would never argue otherwise.
But that’s not what you said. You said that an SLBM would be “unstable” if “canted over” to fly horizontally. Then you said that it wouldn’t be unstable, but only at apogee, because the rocket’s center of mass had shifted enough in an unspecified direction. Those were the points I took issue with.
[sup]1[/sup] I acknowledge that I contributed to the sneering. I regret it, which is why I’m trying to shift the tone.
When a Trident (or whatever missile you choose) is at apogee, the payload is conducting its maneuvers to take readings from its star tracker while continuing on its same ballistic flight path.
Talking about a payload traveling perpendicular to the earth while at apogee would seem to me to have literally nothing to do with the depressed trajectory being discussed here… unless you think a D5 could conduct the same maneuvers at <10,000 feet and continue along its flight path.
As a side note, this is a special, special case. I’m saying the missile fires from inside the Chesapeake - it’s targets are under 10 miles away. The only reason the submarine wouldn’t be destroyed by the blast is it’s firing from underwater and the water:air impedance interface would probably block most of the overpressure.
So the aerodynamic loads might not be very high because the missile doesn’t really accelerate very long. You might also throttle back and have it travel more slowly so it doesn’t break up in the atmosphere.
You can’t throttle back though. SLBMs are solid-fueled these days. So there’s no throttling back or stopping the booster burn.
The best you can do is put it into some kind of trajectory that is going to have a lot of atmospheric resistance- more flat and not at all optimal in terms of payload.
But even at that, we’re looking at something on the order of 1500-2000 kilometers minimum range, which is SHORT, considering the maximum range is more like 7500-8000 km on a more conventional trajectory.
They’d have to be out in the Atlantic or maybe in the Gulf to hit Washington like that. The real advantage would be that the flight time would reduce from about 15 minutes to about 9 minutes.
https://www.cia.gov/library/readingroom/docs/DOC_0000500575.pdf
I don’t think there’s enough info in the video to determine that.
Because the question is not whether a torpedo can arrive between the launch of the first missile and the last. The question is whether a torpedo can arrive between the first unambiguously detectable step on the missile-launch procedure and the first (or last) missile launch).
[sub]I realize that I’m not helping the downward glideslope either, and I apologize. I haven’t done rocketry since college (20 yrs ago), and have lost a lot of the memory on proper definitions (i.e. Max Q, centers of gravity, centers of lift, etc.). My concepts are clear in my mind, but I’ve been poorly articulating them through bad anecdotes and analogies. I’ve also been trying to do this while being rushed, and from a tablet/cellphone, which isn’t helping. Please accept my apologies for lending to a poor tone, and I’ll try to better describe what I’m proposing. I invite you, (and anyone else that wants to come), to a virtual barbecue restaurant, where we can discuss the OP, like proper Engineers: over a couple ‘o’ slabs of ribs and heapin’ baskets of fries, with beverages of your choice. That being said, please pass the spicy sauce, and I’ll re-group some of our quotes into a coherent couple of paragraphs.[/sub]
I hear you, EdelweissPirate, and you’re correct–I now realize where I hadn’t remembered a lot of the other forces at play. Let me take a moment to re-frame my thoughts a li’l better:
[ul]
[li]I’ve probably been confusing some terms, correct me where I’m wrong. I have been using “axially” where I might better off have been using “along the longitudinal axis.” From the tip of the nose, to the center of the exhaust, that’s what I’d been calling “axially.” I have also goofed, and in the one case did mean “parallel.” [/li]
[li]The SLBM, as a system, has a changing Center of Mass (CoM), and what I’d term a “Center of Lift” (CoL). “Unstack 'em” relative to gravity–yer hosed. Bear with me on this one: The payload has it’s own CoM, and it’s at a fixed point along the longitudinal axis, but it’s just one component of the overall system. As motor stages are exhausted and shed from the rest of the missile, the system CoM and CoL shifts closer to the payload, shortening turning moments[sup]1[/sup]. I believe that in a perfectly perpendicular attitude, the CoM (wherever it is during flight) stacked ‘above’ the CoL in relation to gravity, is the most stable configuration, again, in relation to gravity. [sub]I was trying to use that balanced pen/pencil as an example[/sub]. Any deviation from that perfect “stack” allows gravity to put a turning moment on the flight body. I picture gravity pulling down on a lever arm; gravity acts on the CoM and the fulcrum is where the CoL (the point of thrust) is lifting the body. With the OP’s “point blank” shot, I doubt the first stage would have been shed by the time the flight body goes horizontal, creating your biggest moment on that lever arm. If there were fins/wings/canards you could offset that lever with some lift, but the Trident doesn’t have them, and I suspect that given enough of a tilt, the whole thing would corkscrew or fall like a tree to the ground. [/li]
[li]I honestly don’t think the thrust can be vectored to enough of an angle, or fast enough to accommodate truly horizontal flight for a “point blank” trajectory. Tridents (or Poseidons) weren’t really designed for this kind of flight profile. I can’t speak to the control systems, but having been up close and personal with some of these things[sup]2[/sup], I doubt the pneumatics and hydraulics could keep up with vectoring thrust fast enough for changing conditions. Once it tips over, it has to keep accelerating at least 1 g away from the earth to maintain an attitude towards its target. Granted, it’s got 6 g additional[sup]3[/sup] to accelerate with, but without flight control surfaces . . . I dunno brother, I’ve got a hard time seeing this making it that far with only thrust. . .[/li]
[li]Compressive strength through the longitudinal axis of the system is already proven. I doubt lateral shear strength is nearly as good. We’ve launched these things before, and we continue to do so periodically for flight tests, in their ballistic profiles. Loads are through the longitudinal axis–and you’re correct again: I forgot about the longitudinal axis loads from gravity (down) and acceleration (up). And I see and agree with gravity being 1/7th of the problem (on a 7 g acceleration). What I don’t think is going to hold together are the mechanical joints between stages in a horizontal attitude, or even the solid fuel itself. Something would buckle and either bend (to induce a turning moment between the CoM and the CoL), or the thing would start mechanically separating in flight.[/li][/ul]
I think we’re in agreement on the concepts, with only differences in opinions.
What hasn’t been addressed yet, and what’s more important, is how the OP plans to seperate the RVs from the equipment section in such a short span of time, and accurately hit their target. RVs were designed to fall to their target from high above. “Things” need to happen for the warhead to function properly.
[sup]1[/sup] I vaguely remember that the closer your CoL is to your CoM, the more stable your aircraft is, but because the distance is so short, it’s far more nimble (e.g. an F-16).
[sup]2[/sup] Let’s just say that through work, I get to see these things from time to time.
[sup]3[/sup] I’m just rolling with your “7 g” from earlier.
Tripler
Are you a mustard sauce or vinegar sauce kinda guy?
These would be Russian / Soviet warheads. I sorta imagine a crew of technicians with soldering irons bypassing most of the detonation interlocks before the subs depart. And drinking vodka.
But on a serious note, did the warheads ever really get the embedded “weak link” technology USA shared with them? Because if they didn’t, just bypassing components or replacing the detonator circuit board with one with modified firmware so that the only safety checks are for launch and perhaps an arming timer sounds feasible.
Obviously the USA could remanufacture their warheads the same way but I suspect it would take longer. Since I understand there are supposed to be electronis buried in the warhead designed to permanently brick themselves if any tampering is detected.
I assume if there were no interlocks the actual warhead needs mere seconds at most to go off.
Warheads are explicitly engineered to “brick” if tampering is detected.
If you want a warhead to “go off” at your target point and with expected yield, then this is an incorrect assumption.
Trip
That leaves one option - begin preparing the warhead to explode while it’s still in the submarine.
Warheads mounted to their boost missiles are inaccessible from the interior of/inside the submarine.
I think this is the answer right here. If you fire it at a low angle, it will be travelling through the troposphere at speeds that are meant for the stratosphere (and higher), which will rip it apart. And it can’t be throttled back since it’s a solid rocket.
Lots of other good replies in this thread but I think this one is the clincher.
If memory of Clancy’s novels (yes, I know…) is correct the Soviets did have this sort of capacity. It was called FOBS or something similar.