The AA-6 NATO Acrid was specifically designed for carriage on the MIG-25 Foxbat. The AA-6 is available in infrared and semi-active radar guided variants. Due to maneuverability limitations in the terminal phases of an intercept, the AA-6 did not present a formidable challenge to defensively maneuvering fighters
In early 1962 the Bisnovat design team began working on the R-40 (K-40), a new long-range missile intended for use with the the MiG-25-40 high- altitude interception system, consisting of the MiG-25 aircraft with Smerch-A radar set and the R-40 missile. Though only slightly larger than the predecessor R-4, the range of the R-40 is over three times greater. This missile was produced in two variants: R-40R (Object RD46 with PARG-12 head) and R-40T (Object TG-46).
After the defection of a MiG-25P to Japan on 06 September 1976, an extensive redesign of the aircraft was undertaken, resulting in the MiG-25PD interception system. Instead of the Smerch-A, a Sapfir-25 radar was installed. The new missile R-40D and its R-40D1 update ("dorabotanaya" [more elaborate]) were produced in two variants R-40RD and R-40TD, both featuring improved countermeasures resistance and a more sensitive homing head to improve performance against low-flying targets. The R-40D1 missile was developed by the Vympel team, the Molniya team having by that time withdraw from development of aircraft missiles. The R-40 is still included among the weapons of MiG-25 and MiG-31 aircraft, although production was discontinued in 1991.
In 1975 the Soviet Union began to deploy a new generation of air-to-air missiles on the MiG-23 and -25 fighters—the AA-6 Acrid, AA-7 Apex and AA-8 Aphid. These designations are US/Nato reporting names. As a result of Lt Belenko's defection to Japan in an unarmed MiG-25 Foxbat, accurate dimensions of that aircraft are now available, allowing the size of Acrid to be estimated with a fair degree of certainty.
Acrid exists in two versions—one has a constant diameter nose section leading to a white nose radome, while the other has a darkly colored, tapering nose. The constant-diameter nose houses a radar homing head, the tapering an infra-red seeker. Radar and infra-red versions exist of the earlier AA-5 Ash missile which arms the Tu-28P Fiddler, and the Soviet Air Force is known to favor the ripple-firing of pairs of this weapon. The infra-red round is fired about a second before the radar missile, a technique presumably adopted for the Acrid.
Belenko's Foxbat A was equipped to carry the AA-7 Apex and not the much larger Acrid, and had engines widely reported as being of 24,5001b thrust. The Acrid-armed Foxbat is probably a later version with the 31,0001b engine used by the record-breaking E-266M.
The radar version of Acrid is 6.29m long and 36cm in diameter, while the infra-red model is 6 percent shorter at 5.91 meters. Foxbat is red-lined at Mach 2-8 when carrying missiles, so that Acrid structure will have to cope with the aerodynamic heating present at such velocities. Design work on the missile must have begun in the mid-1960s, by which time Foxbat was already flying, so titanium rather than steel was probably chosen for the airframe to keep the weight as low as possible. The radar missile is thought to weigh between 700kg and 800kg, making it twice the weight of Phoenix—the heaviest Western air-to-air missile.
At first sight Acrid seems to be quite the wrong shape for a Mach 2-8 missile. The large wings have a total area of 4-56m2, with the canard surfaces adding a further 9-26m2 — much more than the wing and fin area of the nearest equivalent Western missiles (see table). But the most likely explanation for such large surfaces is that they give Acrid a good snap-up performance against targets above the ceiling of Foxbat.
A study of US rocket motors suggested that the Acrid motor needs to be about 3m long, and the missile in the accompanying photograph changes color 3-3m from the rear. Assuming that this represented the junction between motor and forebody, the powerplant must weigh about 450kg. The nose of the weapon houses the radar or infra-red guidance unit, and the canard actuators must be in the next section, followed by the power sources for the electronics and control surfaces, and then the warhead. On the original photograph a raised fairing can be seen running aft from the canards.
Electrical wiring within this will pass commands to a second set of actuators at the rear of the missile to control the wing-mounted elevons. This wiring cannot be routed within the airframe due to obstruction from the warhead and motor. No other airto-air missile uses dual control surfaces, with the attendant complication of extra actuators, so it must be assumed that the configuration offers advantages at high altitude, perhaps by reducing the energy lost while manuvering.
Little information was available on Russian warhead design, but continuous-rod or fragmentation types would seem the most likely. There was no evidence of nuclear warheads being used in Russian air-to-air missiles but there is enough room for one in Acrid. Warhead weight could be anywhere between 60kg and 100kg. The range of the radar missile is unlikely to be more than 50km, the maximum distance at which, according to US sources, the Fox Fire radar of the MiG-25 can track targets and illuminate them for missile attack. Some reports claim that the wingtip pods on Foxbat are used for target illumination, but this seems unlikely. Assuming the use of I-band radar frequencies (8-10GHz) Fox Fire's 0-85m antenna would have a beamwidth of 2-5°, making it a better energy source than a pod-mounted antenna with an estimated beam width of 18°. Infra-red guidance has a shorter range than radar, so the effective range of the second Acrid version is unlikely to exceed 20km.
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