a Ministry of Aircraft Production order issued three days later with developing a fast maritime reconnaissance version of the Yak-25, designated the Yak-25MR. The aircraft was to fill a requirement for a maritime reconnaissance aircraft from Soviet Naval Aviation, and was required to match or exceed Yak-25 performance, commencing State acceptance trials in February 1955. Yak-125B Yakovlev was tasked with developing a high-speed nuclear bomber using the basic Yak-125 design, the Yak-125B, by a special joint directive of the Central Committee of the Communist Party and the Council of Ministers. The Yak-125B was intended to break through enemy air defenses and conduct a nuclear strike against strategic targets in the enemy rear. It had a crew of two; the navigator, who doubled as the bombardier, was seated in a compartment in the extreme nose. The nuclear bomb was housed in a bomb bay near the aircraft's center of gravity, which resulted in the nose unit of the undercarriage receiving twin wheels of similar size to the main unit, which was moved just aft of the bomb bay. This arrangement was later used on Yakovlev tactical bombers, including the Yak-28. Yak-125B was the first Yakovlev aircraft to include a 360-degree ground mapping and bomb-aiming radar, the RMM-2 Rubidiy, located in a radome directly below the cockpit. The aircraft entered flight testing in 1955, and the production version was planned to be designated the Yak-25B. However, it never entered production due to obsolescence and Yakovlev's testing of a superior supersonic nuclear bomber, the Yak-26. Yak-25RV A reconnaissance derivative of the Yak-25, the Yak-25RV (Razvedchick Vysotnyj, "high-altitude reconnaissance"), was developed in 1959 (NATO codename 'Mandrake'). It had a completely new, long-span straight wing of 23.4 meters (more than twice that of the Yak-25M interceptor) with a total area of 55 square meters. Camera and sensor packs were added in the fuselage. Some versions may have retained one cannon. Despite its low wing loading, the 'Mandrake's' altitude performance was marginal at best, with considerable engine problems at high altitudes, excessive vibration, and primitive equipment that imposed high workloads for the crews. The Soviet Air Force nevertheless kept the Yak-25RV in service until 1974. A few were used in the late 1970s for monitoring of radioactive contamination, with specialized sensors; these were designated Yak-25RRV. Efforts in 1971 to develop the 'Mandrake' as a high-altitude interceptor (Yak-25PA) proved unsuccessful. In 1961 a series of lightened 'Mandrakes'