RP-21 Sapfir

The RP-21 Sapfir (NATO codename: Spin Scan) was a radar system developed by the Soviet Union for use in the updated MiG-21PF fighter, and used in later versions of the MiG-21.

The radar was simple to use and repair, and, because of vacuum tube technology, was able to withstand a powerful electro-magnetic pulse (EMP), a side-effect from nuclear explosion, radiation harmless to humans but very damaging to modern solid state (silicon transistor) electronics.

Its capabilities, as limited as they may seem, were offset by the standard PVO doctrine: pilots were tied to a ground-controlled interception (GCI) system, which, through ground-based radars and data links, provided interceptors more extensive and more precise information.

Also, the radar was rather quickly compromised because of defections, and its weaknesses were well known to the West, giving way for the creation of effective electronic countermeasures (ECM).

Still, the RP-21 and its developments, like the RP-22 radar (NATO codename "Jay Bird") of the later MiG-21bis series, had a long career and the latter was even used for export purposes in downgraded MiG-23S and MiG-23MS interceptors.