S-70 Okhotnik combat drone: Sukhoi rolls out second near-production stealth prototype in Siberia

Sukhoi presented a flying-wing combat drone on 14 December: at the Novosibirsk Aircraft Production Association (NAPO) in south-western Siberia, the second prototype of a future series of the S-70 Okhotnik (= Hunter) rolled out of the hangar – an unmanned combat aerial vehicle (UCAV) from the Sukhoi design bureau, part of the state aircraft-building conglomerate UAC.

Russian Deputy Defence Minister Alexei Krivoruchko stated: “The presentation of the UCAV marks the completion of the assembly of the system as a whole, its fitting with all necessary on-board equipment in line with the requirements for the vehicle, and the transition to complex ground tests and preparation for the first flight”. His superior, Defence Minister Sergei Shoigu, said in Moscow that he expects the Russian Aerospace Forces (VKS) to place an order next year – after initial flights and completed tests.

All in all, the latest S-70 derivative is likely to mark a leap forward for Russia in turning low-observable technologies into production-ready manufacturing. It still lags behind some competitors such as Taranis (UK) or Neuron (Dassault + Saab). Over the past decade, the impression had generally arisen that Russian industry was lagging in this high-tech sector – or that the military had for a time attached little weight to the field and therefore hardly initiated such developments. But after Kronshtadt recently showed the Orion-E, a vehicle similar to the MQ-1 Predator, in Dubai, the presentation of the 20-tonne aircraft with a 20-metre wingspan – quite substantially sized – was another ambitious step towards closing this gap.

Combat drone in testing since 2019

The very first prototype made its maiden flight on 3 August 2019. On 27 September 2019 it flew in formation with a Sukhoi Su-57 – Airbus-Helicopters and Schiebel also pursue a comparable “manned-unmanned teaming” approach. For the Russian version of the “loyal wingman” concept, the S-70 was given air-to-air missiles without motor or warhead but with functioning electronics. This was used to test a concept of operations in which the S-70 detects distant enemy air targets and (also) engages them after decision and release by the Su-57 pilot. In early 2021, weapon integration tests followed at a test range near Astrakhan: Okhotnik carried unguided bombs in the two internal weapon bays, each holding 1,000 kilograms, and dropped them on ground targets.

The first design, however, still had some external “conspicuous features” that hindered low detectability on enemy radar from all illumination directions (all-aspect low observability). Above all, this concerned the uncovered exhaust nozzle of the turbofan engine, which visibly came from Sukhoi jets. With its heat signature, this first design would “glow” like the GUM department store. It was apparently powered by an AL-41F; whether this engine also sits in the second example behind the exhaust outlet, now flattened much more in line with stealth principles, is not yet known.

On the first design, extensive, coarse dielectric antenna surfaces, air intake scoops and various measuring probes and instrument sensors severely affected the radar return – most have now disappeared from the outer skin. Apart from a few rows of countersunk rivets, the surface looks relatively flawless all round. A pair of air data probes remains; a future production version will probably do without these too. This is comparable to the difference between the T-50 prototypes of the PAK-FA and the refined, production-representative Su-57.

Striking features of the aircraft now presented are blue and grey panels on the wing leading edges and the nose. The leading edge in particular plays a decisive role in low detectability. These areas are expected to be treated and coated with radar-absorbent material (RAM); beneath the outer skin, which remains transparent to certain bandwidths, structures for damping radar waves are also likely to be used. In addition, the drone has yet to receive its full paint scheme – possibly in the “pixelated” pattern seen on a model at MAKS this year. That model was also the first to show the flat exhaust slot that has now been implemented.

Timetable possibly too ambitious

The Okhotnik combat drone is clearly still far from frontline use. At the roll-out, ambitious timetables were mentioned, according to which NAPO – where the Su-34 is currently built – is to start series production from 2024; from today’s perspective, this may not be achievable. Considerable hurdles remain. They include ensuring that the UCAV meets its low-observability ambitions and works as an effective weapon system within a network – enabled by command-and-control software and a data link architecture. Since its engagement in Syria from 2015, however, Russia has been rapidly gaining useful operational experience, albeit with more modest drone designs.

For the Russian aerospace industry as a whole, developing more refined stealth technologies and industrial series production capabilities for the – now revised – S-70 will certainly bring considerable benefits. As Sukhoi/UAC chief Yury Slyusar assured the author in Dubai, work continues on designs for combat aircraft of newer and the newest generation. Then, of course, there is the Su-57E export version, which Slyusar is keen to export. Part of the potential for these projects certainly also lies in the work on Okhotnik and other unmanned systems whose external configuration is the same or similar by design. This applies, for instance, to the eagerly awaited new PAK-DA strategic bomber, intended to replace the Tu-22 and Tu-95 and – like the new US B21 bomber – also expected to be a flying wing. Provided it ever actually takes shape.