Following public demonstrations of the S-5U air-launched rocket, Russia is set to resume manufacture of 57-mm unguided rockets after a gap of almost 30 years. A previous design of the same caliber, the S-5M, was produced in the country from 1959 through to 1990. IPF (local acronym for Novosibirsk Institute of Applied Physics), responsible for the development of the S-5U, issued a statement saying that “the re-birth of the low-caliber [rockets] is explained by the appearance of new explosives, solid-fuel motors and shooting platforms.”
Compared to its predecessor, the S-5U is longer, at 1,090 mm (3.28 feet) compared with 882 mm (2.89 feet), and heavier, at 6 kg (13.23 pounds) versus 3.86 kg (8.51 pounds). Instead of solid fuel (ballistite powder), its motor runs on composite propellant: a mixture of oxidizer, binding agent, energetic compounds, and plasticizers. The S-5U’s effective firing range is given at between 0.5 and 4 km (0.27 and 2.16 nm), which is comparable to the older generation.
Both the S-5M and S-5U are fin-stabilized projectiles, but they differ on how aerodynamic stabilization is achieved in flight. A set of eight wide-span folding blades on the rear fuselage of the S-5M that flip forwards on launch has been replaced on the S-5U by four curved fins wrapped around the nozzle of the rocket to match its diameter when stored. On launch, they flip sideways to open. They are set at a slight angle to the airflow so as to make the projectile rotate axially in flight for additional spin-stabilization.
The original S-5, itself modeled on the 55-mm R4/M and Schlange, both World War II German designs, entered service in 1955. Four years later, it was followed by the improved S-5M that provided the base for about 20 sub-variants, and became the most popular Soviet air-launched munition ever made. Such rockets were fired by the thousands during the Soviet invasion in Afghanistan 1979-1989, where their lethality was found to be low due to a relatively small high-explosive charge of less than 0.3 kg (0.66 pounds). Since the late 1980s, the smallest rocket in the Russian inventory has been the S-8 family, of 80mm caliber. For lethality greater than that of the S-5M, the S-5U carries a larger warhead, filled with 0.8 kg (1.76 pounds) of explosive, or 2.8 times more than its predecessor.
“The Su-5U appears comparable in combat efficiency to the in-service members of the S-8 family rockets, and even surpasses them in a number of points,” stated IPF. The developer explains that the new weapon comes with “a universal warhead” featuring three different effects. Its cumulative bloc penetrates 150 mm of armor, the high-explosive charge forms about 500 splinters (compared to 220 for the S-5KO) each weighing 2 grams (0.0044 pounds), and there are incendiary elements.
“Since [Soviet-era] warplanes and helicopters armed with (UB-9/16/32) pods went for export in large quantities, and some are still operational, this means that the S-5U may have a large export potential," said IPF. It further noted that a number of foreign countries, including Bulgaria, continue manufacturing S-5 series rockets to Soviet blueprints.