If you are refering to the MiG-25, yes the majority of the on-board avionics were based on vacuum-tube technology, not solid-state electronics. Although they represented aging technology, vacuum tubes were actually more tolerant of temperature extremes, thereby removing the need for providing complex environmental controls inside the avionics bays. In addition, the vacuum tubes were easy to replace in remote northern airfields where sophisticated transistor parts might not have been readily available. As with most Soviet aircraft, the MiG-25 was designed to be as rugged as possible. Moreover, the use of vacuum tubes makes the aircraft's systems more resistant to an electromagnetic pulse, for example after a nuclear blast. Keep in mind that the MiG-25 was designed during the cold war when there was fear of thermo-nuclear war. Of course, this in no way affected performance. Thanks to the use of vacuum tubes, the MiG-25P's original Smerch-A (Tornado, NATO reporting name 'Foxfire') radar had enormous power about 600 kilowatts.
The Soviets always proved with their ingenuity that things can be done much more easily without compromising performance. Another example is the MiG-21. The rivets on the aircraft weren't perfect where it didn't matter. But no one cares as "it doesn't matter". It was still Mach 2 capable. The aircraft was refined where it mattered the most and this is what accounted for it's low unit and maintainance costs compared to other European and American fighters of the time. Now can we please keep the discussion to the topic?
Excuse me, but one of the things the U.S. discovered when defecting Soviet pilot Victor Belenko landed his MiG-25 in Japan in 1976 was that the Russians had surpassed the West in vacuum-tube development. Russian tubes were tougher than Western ones and could handle high-power currents that U.S. tubes and transistorized circuits could not. I believe the U.S. copied this technology for use in its own electronic warfare systems - a rare example of the West reverse-engineering Soviet-bloc technology.
I also recall that the vacuum tubes available in the local hobby shop in the 1980s were made in Russia, not the U.S. or Japan.
Just as the demise of electronic vacuum technology and its applications have been greatly exaggerated, so is its efficacy and performance claims in terms of avionics.
People must keep in mind that in aviation, weight is a penalty, meaning
ANY item, from the belt buckle to the knobs to the cargo, humans or else, is a weight penalty, and I have yet to see any credible technical source comparing a vacuum tube avionics system against a solid state competitor and the tube system at least held its own, if not surpass its rival. Do most people know that the common cathode ray tube (CRT) is basically a vacuum tube device? A vacuum technology device such as a traveling wave tube (TWT) is best applicable for transmission in a radar system because of its bandwidth.
However...With the nature of radar detection, any target resolutions perform by vacuum based devices are grossly overkill because those target echoes are magnitudes lower on the power scale that smaller and more power efficient solid state devices are better for signal processing. Does that mean we cannot engineer a vacuum technology based device that will perform the same functions as its solid state rival? Yes...Certainly we can but the final product will be so large that its aviation weight penalty will override any deployment considerations.
Not only that, in some aviation situations, vacuum technology based devices simply cannot perform as well as its solid state rival...
Quo Vadis - AMRAAM?
n spite of all expectations Sparrow performed poorly in combat. The poor reliability of the vacuum tube guidance system, the limited aerodynamic manoeuvrability, the large minimum lock-on range, the inability of the conically scanning seeker to handle ground clutter and evasive manoeuvring by targets, all contributed to a kill probability (P[k]) of less than 10% per launch.
The highlighted is significant. Target resolutions here are not only altitude, speed and aspect angle to the seeking radar in the missile, but also involve changes and
RATE of changes of those resolutions. The 'guidance' package contains the radar seeker section and the flight controls system (FLCS). As aircraft performance levels increases, so will those resolutions, their changes and
RATE of changes. Solid state based electronics with their superior power efficiency level are inherently better at processing these rapid changes.
That is why citing the MIG-25's radar power output is highly misleading as we have no indicators of its performance at the second part of radar detection -- target signal processing. We finally know this after Belenko's defection. The MIG-25's radar will 'burn-through' many ECM transmissions but it is far inferior to Western systems in terms of target resolutions. Its vacuum technology based avionics are EMP resistant but that is a side benefit, not a primary consideration when they designed the aircraft. Soviet designers have no choice but to use vacuum technology based avionics because of the technological inferiority of the Soviet society. Coupling a solid state controller/driver to a TWT reduces by half the final device's size and power consumption without sacrificing bandwidth and add the benefit of superior signal processing. Soviet engineers were not stupid but they were also smart enough to realize that just because they can gain access to that solid state technology, by hook or by crook thanks to their clandestine services, that does not mean the Soviet technology foundation is capable of replicating the same solid state device with %100 fidelity.
The klystron tube is another vacuum technology device that is still very applicable and best when there is a need for high energy
AND large bandwidth...
Forty years of research on the structure of matter - CERN Courier
SLAC is also the world's leader in developing high-power klystrons, which generate the microwaves used to accelerate electrons. Invented in 1937 at Stanford University, klystrons are also used to power radar arrays and for medical accelerators employed in cancer therapy.
But after the tubes are solid state devices for signal processing, be it from a radar echo or from a proton or from human body. A single frequency klystron tube, not solid state devices, is best for an EMP weapon.
So just because the US had to import vacuum tubes for our high end audio devices that does not mean we are 'behind' in vacuum technology based electronics. Please stop this exaggeration of the MIG-25's vacuum tube based avionics. It was good but only up to a point and Western avionics have been agile enough to bypass that point.
surly I do hope you know Russian specialists collaborated with Lockheed Martin in the F-35's development. Moreover, NPO Energomash sold General Dynamics, now Lockheed Martin, rocket engines. And in fact even Boing has an office in Russia that does design work for them. Clearly this demonstrates that they do come close.
