I know a lot of military vehicles and equipment has significant amounts of shielding against EMP. The Russians even used vacuum tubes on their planes well into the 70 and 80s IIRC because they wouldn’t be damaged by EMP.
How much shielding does a modern military aircraft have against EMP? Would a high altitude blast take out most of the vehicles under the area where unshielded electronics were knocked out, or are they hardened enough that only a close blast would disable them? What about other types of equipment?
Correction: the Soviets used vacuum tubes on guidance and avionics equipment because they were cheap, robust, and readily serviced in the field by the poorly trained conscripts that formed a large part of the Soviet military. (Poland, Russia, and some of the East Bloc nations are still the largest producers of vacuum tubes for audio and avionics.) The slowness and bulk of tube circuitry, the high power requirement and heat waste, and relatively short lifetime were tradeoffs that were accepted versus the poor quality control of Soviet IC manufacture. (Note that in computational theory the Soviets were on par with the West; it was their ability to manufacture reliable electronics in production quantities in which they fell woefully short.
To answer the specific question of the OP, it depends upon the application. Military electronic hardware, save for acceptable commercial-off-the-shelf (COTS) components, area built to specific interface standards like MIL-STD-464 (Electromagnetic Effects Requirements for Systems), MIL-STD-461 (Requirements for the Control of Electromagnetic Interference Characteristics of Subsystems and Equipment), and MIL-STD-2169 (Classified) (High Altitude Electromagnetic Pulse Environment). The latter is probably most pertinent to the question, and for obvious reasons unavailable to the public at large. However, the ugly truth about high altitude EMP is that no amount of shielding, save being buried deep under hundreds of feet of rock or dirt, is really adequate to protect sensitive microelectronics. By their nature, the electronics are delicate and sensitive to small levels of excess voltage, and it is nearly impossible to make a practicable sensor, communication system, or avionics control that has to interface with the outside world and yet is adequately isolated against large pulses.
High altitude EMP (HEMP) devices produce three distinct regimes of pulse, referred to as E1, E2, and E3. Microelectronics are most sensitive to E1, which is due to interaction of x-ray and gamma ray radiation with the rarified upper atmosphere and the geomagnetic field resulting an a nearly coherent, widely distributed pulse, sort of like a very large free electron maser. In more dense atmosphere where the the rays are rapidly absorbed and don’t have much length to deflect, this pulse is serious attenuated, and the amount of damage done but the physical effects of the blast (shock and thermal wave) would likely make E1 effects moot. E2 is more like static electricity, and can typically be shielded by using a protected ground or faraday cage type shielding. E3 is energy that is stored in the Earth’s magnetic field (similar to that which comes from coronal discharges and solar flares) and will cause longer term disruption and very high voltage spikes in large arrays like power grids; again, not much of a threat to microelectronics.
Some work has been done on non-nuclear electromagnetic pulse (NNEMP) generation, mostly by use of explosively pumped flux compression generators (EPFCG), like that portrayed in the remake of Ocean’s 11. Much of this work is classified, but the basic physics of it is pretty simple; you use an explosion to compress a large capacitor, vastly amplifying the discharge and obtain a very large flux through its electromagnetic field. The range of these devices are necessarily limited to the local area, unlike HEMP devices that provide coverage for hundreds of thousands of square miles.
I would guess that no portable EMP shielding would make anything totally immune from EMP blast, but that it could affect the range from the explosion at which it would become inoperable. I guess my basic question is - in the event of a nuclear blast, would military aircraft from hundreds of miles around suddenly fall out of the sky?
As far as vacuum tubes go, was their EMP resistance a consideration at all? That is… both the combined benefits of easy manufacture and service and EMP-resistance were factors… or is there another weak link in tube based electronics that would render them vulnerable to EMP and hence make it an irrelevant consideration?
Sure, and most military computer systems that aren’t COTS are “hardened”, albeit more against direct impingement of radiation rather than EMP. The thing is, any shielding against EMP, especially on systems that utilize some kind of antenna and amplifier, it is nearly impossible to eliminate the vulnerability, whereas an attacker can overcome defenses merely by amplifying the electromagnetic yield of a weapon. The saving grace–at least, against less developed opponents–is that in order to get a large field of effect you have to get the weapon to the very edge of the atmosphere; a typical airburst at 10k or 20k feet isn’t high enough to amplify or distribute the pulse. This means that you need an ICBM-class vehicle, not just a Scud-type weapon or an aircraft. Of course, both Iran and North Korea are working on such vehicles, but they’re a long way from being able to threaten the US in this fashion.
No doubt their relative invulnerability was a consideration in some applications–this is certainly true with the AN/FSQ-7 computer that was the heart of the SAGE defense tracking system–but the resistance of tactical aircraft to nuclear weapon effects is a tertiary consideration at best; Soviet aircraft designers were more concerned about the ability to maintain their aircraft on poorly supplied and roughly constructed airfields across the vast expanse of the Soviet Empire. To this end, using vacuum tube computers, with a handful of easily serviced components that could be reliably produced in quantity despite highly variable quality control, made far more sense than specialized and ESD-delicate integrated circuits which may or may not get produced in this Five Year Plan, and may or may not contain the correct elements if they do. To this end, if you look through Cold War vintage Soviet equipment you’ll find a lot of weird anachronisms, like intricate printed circuit boards (PCBs) with giant vacuum tubes mounted on massive waffled isolation plates (necessary to isolate the physically delicate tubes from shock and vibration) with enormous radiators to bleed off the waste heat, which is sort of like tearing down a laser ring gyro only to find a miniature East German sextant in the middle operated by a tiny Leprechaun.
suppose we conclude that yes, there is no way to protect the sensors or something similar, during operation. Now, can we protect them in shut off state by keeping them completely shielded in faraday cage (like a metal box or similar)? Sort of like, right now fighter plane is flying using sensor1, then after it gets fried, we will automatically remove the cage and start using sensor2? Well, even if we cannot do such things automatically, can total caging at least be used for strategic stockpiling purposes?
What about non-military electronic and electrical equipment? If a high-altitude blast was detonated over, say, Washington DC to generate an EMP, what would happen generally? Would cars be disabled? Residential and commercial power? For how wide a radius?