Born in the late 1950s, the MiG-21 still exists and becomes the iconic fighter of the supersonic age.
One of the features of this design was a tubular fuselage with the shock cone and front air intake did not see widespread use outside the USSR and ultimately proved to have limited development potential, mainly due to the small available space for the radar.
Early fighters had nose air intakes as a simple design choice to get straight-line airflow into the jet engine. They didn’t have to consider super important technology changes like radar, which killed nose-air intake designs pretty quickly. The best place for a plane radar is up front in the nose cone with more room for better radar field view.
The MiG-21 was equipped with a rather small radar. The RP-21 Sapfir mounted in the nose of the MIG-21 was very limited in it’s radar field only 20° vertically and 60° horizontally. In theory RP-21 Sapfir was able to detect fighter-sized targets from a range of 20 km, and lock on to them at a range of 10 km though in practice this got reduced to 13 km and 7 km respectively. The associated weapon was the Vympel K-13 infrared guided air-to-air missile, also known as R-3S.
Despite not a long-range radar, its RP-21 Sapfir radar helped make Mig-21 a challenging adversary in the hands of experienced pilots, especially when used in high-speed hit-and-run attacks under GCI control. MiG-21 intercepts of Republic F-105 Thunderchief strike groups were effective in downing US aircraft or forcing them to jettison their bomb loads.
Over the years, the West became more acquainted the RP-21 Sapfir during the Vietnam war in Indochina, during the Six-Day and the Yom Kippur Wars in the Middle East. Its combat record is not impressive, mostly due to the primitive and overestimated early generation R-3R radar guided missiles.
Over time, modern jet fighters have radar and other sensors. Radars were getting bigger and more powerful to spot targets from a distance and that was filling up space in the nose fast. Soon the nose intake was just impractical and the nose was solely occupied by the radar and other avionics. The air intakes were relocated to other places like the wing roots or beside or under the fuselage.
