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TLDR: ~ mach 3, practically unlimited range but presumably substandard stealth characteristics. Would it be a game breaking weapon on modern air battlefield or merely would require tactics adjustment for SAM batteries?

Yes, derivative of Project Pluto. Such speed allowed Blackbird to regularly outrun SAM rockets, however that trick worked a half century ago. However, I see that nowadays the most desired feature of fighters is low radar cross-section, and I'm not optimistic what would ex. (sic) happen with sensitive radar absorbing paint, while heated at mach 3. Moreover, I'm not so sure whether when dumping such amount of heat would not make it quite nicely glowing in IR, even before considering its radar cross-section.

While at least in theory it should still outrun big chunk of missiles, for example those intended to serve as anti-rocket systems like PAC-2 / PAC-3 get over mach 4, so I see an issue here. Moreover, with better communication systems I could imagine trying to hunt it using a few coordinated SAM batteries. But I simply don't know whether those features would matter.

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  • $\begingroup$ I'm wondering exactly where you're going to find operators for your equipment who are willing to shoot down a nuclear drone in their general area. Is all your equipment manually operated? $\endgroup$ – Gryphon - Reinstate Monica Oct 22 at 8:57
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Low flying aircraft are best engaged by "look down/shoot down" systems from opposing aircraft, since the elevated sensor and shooter platform(s) will have a much greater area that they can cover with sensors and weapons than ground based systems. An integrated GBAD system tied into the larger battlespace management system would be a useful addition, since they could thicken the air defense layers in the most vulnerable areas, and also have more "persistence" since they are anchored on the ground or in a vehicle rather than an aircraft. This also means the nuclear powered UAV needs to deal with multiple enemy weapons systems, from automatic cannon to radar and infra red guided missiles.

The greatest difficulty after acquiring a high speed target is ensuring there is a weapon in it's flight path. Even a slow moving system would be capable of downing a supersonic missile if it were in front of the target, only high aspect weapons that can fire at large angles off boresight and "tail chase" weapons really need to be faster than the adversary. In more futuristic settings, the defender might have laser weapons, hypersonic artillery shells for GBAD cannon or even railguns mounted on surface and air platforms.

The biggest problem for the defender is actually shooting down a nuclear powered aircraft over enemy territory, so they have to deal with the fallout and radioactive debris from the weapon (much like the Russians did when the salvaged reactor from the "Skyfall" nuclear UAV had a criticality accident when brought to the surface).

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Surface-to-Air systems would still have a really hard time with a missile like this just because of the altitude it flies at. The Project Pluto was originally designed to fly very low, and a modern one could fly even lower, less than 100 feet using the same kind of terrain-following technologies that modern cruise missiles use. This gives surface-based launchers only seconds to acquire, launch, and intercept which generally isn't going to be enough time. This is a non-trivial problem for the United States military currently, and the Navy in particular is extremely concerned about how to keep aircraft carriers safe from the new generation of Mach 6+ cruise missiles that China is developing.

Air-launched missiles would do just fine though, because your Neo-Pluto would be an incredibly easy target for heat-seekers. The Chinese already have a Mach 6 Air-to-Air missile which would do just fine. The USAF would have to do a bit of quick kit-bashing, since Sidewinders aren't fast enough and AMRAAMS aren't primarily designed for heat-seeking, but it'd be pretty easy for Rayethon or whoever to come up with an upgraded Phoenix with a Mach 5 top speed and a heat-seeking guidance.

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The ease with which such a drone can be shot down depends entirely upon its ability to evade a missile launch.

If the SLAM drone was a dumb weapon system, flying a pre-determined course, then shooting it down would simply be a matter of getting an anti-air missile in front of it, whether ground-launched or air-launched. However, given that this was the mission-profile for the conventionally powered Lightning Bug drones (in particular the Ryan Model 147S), a sufficiently low altitude would make it fairly difficult to shoot down.

However, if the OP's proposed SLAM drone had threat detection equipment that allowed it to observe hostile missile launches against it, then shooting it down would be an entirely more difficult matter. The fact that it is unmanned means that the limiting factor in its manoeuvrability is not the combination of the necessity to carry a human pilot, who also has a g-limitation of around 9g for a properly trained and equipped combat pilot, but the span-loading of its lifting surfaces and the strength of its airframe. A flying-wing or blended-wing-body shaped SLAM drone with low spanloading and even mass distribution could be very manoeuvrable indeed, and could conceivably out-turn a missile.

Modern doctrine for fighter aircraft evading an anti-aircraft missile is to attempt to turn behind the missile, effectively turning toward it. Why, when the missile is faster and more manoeuvrable? Why not turn away and open the range? The reason for this lies in how anti-aircraft missiles work. Observe a real (not Hollywood) A-A or S-A missile launch. You'll see that its typically solid-fuel rocket motor fires for a time and then burns out, usually well before reaching its target. Most missiles effectively coast most of the way to their target, relying upon their low static drag in order to retain kinetic energy. Most missiles cannot 'choose' to conserve fuel in order to prolong their manoeuvring time, their engines are like a firework that simply burns and produces thrust until all fuel is consumed.

The effect of turning behind the missile is to force it to manoeuvre as hard as possible. It is an aerodynamic law that lift produces drag (induced drag), so while the missile's fins are turning it, the act of turning - and producing lift - produces drag which slows it down, and the harder it has to turn, the more induced drag is produced, and the faster it loses its kinetic energy. A fighter aircraft cannot win in a turning race against a powered missile, but against an unpowered, ballistic missile? It starts off faster and is more manoeuvrable, but the fighter can power through its turns, while the missile's speed bleeds off, and with just a bit of luck, the missile will run out of energy before it gets to within attack range of its target, its speed will drop below that of its target's, and it will fall behind and eventually fall to earth.

So, if the OP's proposed SLAM drone can manoeuvre against incoming anti-air missiles, it would most likely need to be forked between at least two incoming missiles in order to have any chance at all of being shot down by any of them. It would likely be able to out-manoeuvre any single AAM or SAM launches, and would require having to choose which missile to turn away from and which to turn toward in order to be put in a position where one of the incoming missiles could retain enough energy to reach it. That also discounts the possibility where it could simply fly straight upwards under power, where the missiles pursuing it are entirely at the mercy of gravity, until they are all behind it, then turn hard to pitch downwards over the top of them, once they are all approaching from similar vectors.

So, a purpose-built drone capable of manoeuvring against anti-aircraft missiles would be an incredibly difficult target. Far better to simply fill the air in front of it with steel from dumb rapid-fire AAA and pray for a hit.

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  • $\begingroup$ So the advantage for the drone in your scheme would be that it is actually much more nimble? I wonder to what extend modern fighters are constrained by the need to keep the pilot from experiencing too many G's, and to what extent they are constrained by the need to keep the airframe from experiencing too many G's. $\endgroup$ – Zwuwdz Oct 22 at 16:51
  • $\begingroup$ @Zwuwdz The F-16 is software-limited to 9g, but the airframe can tolerate (IIRC) something like 14g. $\endgroup$ – Monty Wild Oct 22 at 22:56
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Flak

You don't need to hit it but if you fill the air with enough shards of metal, you'll hit something

The Russian BUK missile was used to shoot down Malaysia Airlines Flight 17. It's explodes into a cloud of shrapnel which cuts apart anything in the area

enter image description here

Speed and maneuverability only do so much when faced with a wall of metal fragments

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    $\begingroup$ I mean, yes, but ALL anti-aircraft missiles are like this. $\endgroup$ – Morris The Cat Oct 22 at 12:59
  • $\begingroup$ The problem is getting the missile close enough that enough of the metal fragments can reach the target. Obviously, the shrapnel (or expanding rings in some other AAMs) does not have unlimited range. $\endgroup$ – Monty Wild Oct 22 at 23:00
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Not very hard to shoot down if modern AA system can lock on it.

Systems like S-400 can shoot down targets moving up to Mach 14, and even faster. The question is how easy it would be for the AA targeting system to track down and follow the aircraft.

P.S. There is a strong evidence that the most recent AA systems like Barak 8 were developed to specifically counter the threat of supersonic cruise missiles like Brahmos (Is BARAK-8 the Antidote to Brahmos?). Brahmos, with its Mach 3 speed and low flying altitude seems to be very similar to the ramjet in the original question.

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  • $\begingroup$ Modern missile defenses are designed for targets moving at sub orbital speeds. $\endgroup$ – MongoTheGeek Oct 21 at 19:58
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    $\begingroup$ You're not taking altitude into account. Mach 3 on a ballistic trajectory like a SCUD is nothing. This would be a Mach 3 cruise missile operating at ~100 feet above the ground, SAM launchers aren't going to have enough time to engage something like that unless it's coming straight at them, and even then it's a tough shot. $\endgroup$ – Morris The Cat Oct 21 at 20:20
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    $\begingroup$ @Morris The Cat sustained flight at Mach 3 & 100 feet altitude still looks like a science fiction today. If that's the case here, then yes, existing ground-based AA systems would have trouble locking on such target. $\endgroup$ – Alexander Oct 21 at 21:10
  • $\begingroup$ @Alexander no, it is not science fiction. en.wikipedia.org/wiki/BrahMos $\endgroup$ – Morris The Cat Oct 22 at 12:39
  • $\begingroup$ @Morris The Cat - I was thinking about 100 feet altitude over land, but yes, you are correct. Regarding the original question - there seems to be a consensus that advanced systems like S-400 and BARAK 8 can take down Brahmos (though obviously with less efficiency than regular targets). $\endgroup$ – Alexander Oct 22 at 16:27

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