Su-57 fifth-generation fighter may get flat nozzle for stealth purposes.

The unique flat nozzle demonstrated during the roll-out of the latest S-70 ‘Okhotnik’ (‘Hunter’) heavy strike drone will most likely be installed on the next modifications of the Su-57 fifth-generation fighter for stealth purposes, Russian Air Force merited pilot Major-General Vladimir Popov told TASS.

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Sukhoi Su-57 stealth fighter aircraft showcased during MAKS-2019 (Picture source: Air Recognition)

Russia’s Defense Ministry uploaded a video clip earlier  showing the roll-out of the latest version of the S-70 ‘Okhotnik’ stealth heavy strike drone furnished with a unique flat nozzle thruster to cut its signature for enemy radars.

"Similar measures will most likely be taken for the Su-57 but this will be, perhaps, the second stage of its development. A new engine will be mounted on it," the military pilot said, commenting on the roll-out of the first flight prototype of the latest Okhotnik heavy strike drone at the Novosibirsk Aviation Enterprise on December 14.

A modified engine will most likely feature a flat nozzle, he said. "However, considering that the fighter employs afterburner acceleration modes, this nozzle must have the option of altering its configuration," Popov said.

"Mounted on the fighter, it must both expand and narrow its throughput capacity," the pilot said, adding that the flat nozzle technology was undoubtedly a breakthrough in modern aircraft-building.

Reducing vulnerabilities

The new nozzle for the Okhotnik heavy strike drone will considerably cut its vulnerabilities to enemy heat-seeking missile warheads, the military pilot explained.

"A flat nozzle is designed to cut infrared radiation of the engine’s exhaust gas flow. The flow’s infrared radiation enables air defense capabilities with thermal radiation homing warheads to take aim at the drone," Popov said.

"The incoming airflow kind of compresses and blurs the gases coming out of the nozzle. There is no big [nozzle] torch and thus the flow of gases escaping from the engine is invisible. It is the torch that basically ‘attracts’ thermal homing missiles, be it air-to-air or surface-to-air weapons," the military pilot explained.

The flat nozzle also cuts the aircraft’s optical signature, he added.

Invisible to radars
The new nozzle has altered the drone’s fuselage shape, which has cut its radar signature, the merited military pilot said.

"The aircraft’s radar signature is also reduced after the flat nozzle is installed. The cross section that reflects radio beams is also narrowed because the airplane now has no rough features in its design and it almost becomes flat," he pointed out.

The drone’s fuselage now actually looks like one wing, he said. "If we recall the first version of the Okhotnik, the engine clearly protruded there and now this is not the case. Now all the features are smooth and as a result the cross section has been cut and the radar beam deflection has magnified," the military pilot said.

Latest Okhotnik drone and Su-57 fifth-generation fighter
The S-70 ‘Okhotnik’ drone developed by the Sukhoi Design Bureau features stealth technology and the flying wing design (it lacks a tail), which diminishes its radar signature. According to the data of open sources, the drone has a take-off weight of 20 tonnes and can accelerate to roughly 1,000 km/h. Serial delivery of the drone to the troops is expected to begin in 2024.

The Okhotnik heavy attack drone performed its debut flight on August 3, 2019. The flight lasted over 20 minutes under operator control. On September 27, 2019, the Okhotnik performed a flight together with a Su-57 fifth-generation fighter jet. The drone maneuvered in the air in automated mode at an altitude of around 1,600 meters and its flight lasted over 30 minutes.

Speaking to journalists during the roll-out of the S-70 ‘Okhotnik’ flight prototype with a flat nozzle, Russian Deputy Defense Minister Alexey Krivoruchko said that a serial contract for its delivery to the troops would be signed in the next six months. As the defense official said, the Okhotnik is a highly intelligent system capable of coping with a broad range of tasks on its own, in a group and jointly with manned aircraft. Rostec said that work was underway to set up a new ground-based control post for the Okhotnik drone.

The Sukhoi Su-57 is a Russian-made fifth-generation multi-role fighter designated to destroy all types of air, ground and naval targets. The Su-57 fighter jet is capable of developing supersonic cruising speed, has its armament placed inside its fuselage and radar absorbing coatings and the most advanced onboard radio-electronic equipment. Russia’s Aerospace Force will receive 22 Su-57 fighters by late 2024 and their number will increase to 76 by 2028. The first Su-57 fighter was delivered to the Russian troops in 2020.

As the United Aircraft Corporation (part of Rostec) earlier told TASS, the latest Okhotnik drone would be capable of operating in conjunction with Su-57 fifth-generation fighters. The Okhotnik drone will be able to strike aerial and ground targets as part of network-centric interaction with the fighter, it specified.

TASS also reported that a pilot of the Sukhoi Su-57 fifth-generation fighter jet would simultaneously coordinate the operations of four latest Okhotnik heavy strike drones. Moreover, a group of drones will most likely be controlled from a new Su-57 special two-seat version, it specified.

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