BACKGROUND

The fundamental purpose behind the MiG-31 program was to develop an aircraft capable of intercepting anything the West currently had, which at that time was the Lockheed SR-71 Blackbird, U-2B, TR-1, and the D-21 drone. The cold war was still at its peak and the need to keep the other guy honest had led the United States to begin overflights of Russia with spyplanes. Thus, the Mach 5 Lockheed D-21 drone launched from a "mothership" SR-71 was the only real concern Russia had in 1982, a very real one nonetheless. The Americans already had several successful launches and recoveries of the unmanned aircraft, and with its penetration speed of Mach 5 at an altitude of well over 100,000 feet, Mikoyan-Gurevich needed to make this their primary target. Much of what they had learned from the MiG-25 Foxbat programme was applied to create one of the most advanced aircraft to ever take to the skies. The Firefox was at the forefront of aviation technology and the United States recognized this. The budget kept getting larger and the hopes of building more than two prototypes began to diminish quickly. The titanium manufacturing process alone was already far beyond the initial budget for the program, but officials pushed regardless. They were not to be outdone by anyone, and they certainly would not allow the American's to overfly their airspace unchallenged any longer. The MiG-31 was to be the ultimate advanced interceptor aircraft.

POWERPLANT

The MiG-31 used two Tumansky RJ-15BD-600 high-bypass afterburning turbojets capable of producing 50,000 lbs. thrust each. These were heavily modified, uprated turbojets based upon the engines from the Mig-25 Foxbat programme. Russian engineers took what they learned from high-mach turbojet engine technology and applied acquired US engine manufacturing technology to the Tumansky 600 series engines, built specifically for the MiG-31. The inherent problems Russian designers faced with the R-15BD-300's used in the MiG-25 had been overcome. Overspeeding of the engines had been a major problem with the Foxbat because their methods of controlling the fuel/air ratio were less advanced at the time, resulting in uncontrollable engine RPM at high-mach speeds. The result was an aircraft that could achieve Mach 3.2 for a short burst of time, but the engines would have to be replaced entirely if they hadn't already torn themselves apart. There had to be a way to increase the efficiency and power of the engines while keeping them within thesame footprint of the current R-15BD-300 design.

The introduction of high-bypass air intake systems helped produce the most powerful conventional turbojet engine of it's day, surpassing even the US made 32,000lb P&W J58, used in the much revered SR-71 Blackbird. In addition to these massive engines, the Firefox had six Soyuz/Komarov solid rocket boosters, using a solid-propellant with a proprietary ignition/shutoff system. These rockets could be used to augment the main engines, providing an additional 15,900 pounds of thrust. These were normally used during take-off under full-load, or high-speed dash acceleration. In some rare cases, test pilots were known to engage these rockets at extreme altitudes where thin air produced flame-outs on the main engines. The first flying prototype was taken to 131,079 feet setting a new world record, breaking the previous record of 123,492 ft. held by a Ye-266M.

The compressor blade components were manufactured of pure titanium, a first for Russian aircraft manufacturing. Fuel was cooled via the centerline ventral air intake and then pumped through a complex series of conduits around the giant Tumansky engines to keep them cool, as well as throughout much of the airframe. Much of this technology and ideology was gleaned from information obtained by Russian agents on the production of the US Blackbird, which used similar cooling principles.

By alternating wastegate control between the dorsal and ventral air intakes using ramps, thereby more accurately controlling the engine-breathing, the RJ-15BD-600 could achieve incredible thrust to weight ratio and excellent high-altitude air-breathing qualities. Achieving Mach 6 was a reality, although this was considered maximum speed which was inefficient to maintain for any period of time due to the MiG's massive fuel consumption. Cruise speeds were more in the range of Mach 3.8 to 5.2, and operational altitudes under normal conditions were considered to be in the range of 85,000 to 95,000 feet.

AIRFRAME

The airframe was composed mostly of titanium and SS-118, a stainless steel / nickel alloy that was used extensively in the later model Foxbats. The MiG-31 was the first Soviet aircraft to extensively use titanium in the structure, it wasn't until the mid 1970's that Russia’s’ manufacturing technology reached a point where working extensively with titanium was realistic. However, with the addition of a radar absorbent material coating the aircraft, surface heating became a major problem. To partially combat this issue the plane was designed with a very thin aspect-ratio to the leading/trailing edges of the wings, much like the American F-104 Starfighter. The nose and engine nacelles were designed based upon seamless flat-angles to minimize air friction and reduce overall drag. All rivets were countersunk, unlike most Russian aircraft preceding it, and there were virtually no exposed protuberances, sensors or seams anywhere on the craft. Expansion joints were built into the wings of the craft to allow for expansion/contraction of the skin due to this surface heating. The weapons bays were internal and missiles were carried on retractable launching racks behind flush-mounted doors on the port and starboard sides of the plane. Many different methods of heat-reduction were tested, but in the end it was still a big heatsink, not unlike its MiG-25 forefather.

The airframe had "stealth" characteristics, however there was much debate over the need for this considering the speed and altitude capabilities of the aircraft. It used a three-fold combination of countermeasures to make itself virtually undetectable to enemy radar systems. The design of the aircraft was angular enough to deflect much of the incoming radar away from its' point of origin, the most basic form of "stealth" technology. In addition to this, the skin of the craft was coated with a radar absorbent material (RAM) very similar to the American Stealth technology at the time. Finally, the MiG had electronic countermeasures (ECM) that could jam enemy early-warning systems. However, there was no way to effectively cool the exhaust of the giant Tumansky engines which gave the MiG-31 a massive heat signature for heat-seeking missiles, one of the aircraft's only major downfalls.

AVIONICS / SYSTEMS

The Firefox was the first aircraft to effectively use an operational thought-controlled weapons management system. Not only was it a fully operational and working system, it was also rather simple and unobtrusive from a mechanical standpoint. The receptors were mounted inside the specially designed helmet and linked to the aircraft's central computer system via a datalink. The pilot simply had to think (in Russian) about what weapon he wanted selected, and could execute the command to launch the missile mentally. This is what is known as an EEG Feedback system. The pilot did not fly the aircraft via thought, only controlled the weapons system by thought. Most of the fly-by-wire systems in the aircraft were considered new technology at the time, but the Thought Controlled Weapons Management System was truly revolutionary. Mikoyan-Gurevich also managed to develop a synthetic aperture radar system for the plane which gave it even more mission flexibility, including being well suited for recon missions.

CONCLUSION

The Mikoyan-Gurevich Design Bureau succeeded in creating an aircraft with capabilities far beyond anything the west currently had by using the proven "brute force" design tactic so typical of Russian military aircraft. The creative minds at the Mikoyan-Gurevich design bureau learned as much about what was being done at the time as they could, then improved upon the concepts in many ways. The west recognized this as an opportunity to even the table and consequently made the radical decision to steal the aircraft from Russia. They succeeded in doing so, succeeding also in destroying the only other prototype example of the MiG-31.

With both aircraft gone, all of the program funding used to build the first two prototypes gone, and several of their lead engineers dead, Mikoyan-Gurevich decided not to reinstate the Firefox program. This effectively ended the legacy of one of the greatest, most powerful and technologically advanced aircraft of our time. There have been many stories about how the Firefox was never spoken of again among the corridors at Mikoyan-Gurevich. All records of it, along with the tooling, were destroyed shortly after it was stolen, and there exists no mention of the programme in any Russian aviation literature. It was viewed by many of the top Russian commandants as an "embarrassing" end to such an incredible machine.