ST-35 Silent Thunder

The ST-35 Silent Thunder is a Ukrainian loitering munition built by Athlon Avia , the Kyiv-based firm better known for the Furia family of artillery-spotting drones. Athlon Avia first revealed the design at IDEX 2018, but serial production and combat fielding came with the full-scale Russian invasion in 2022, when Ukraine pulled almost every domestically built precision system it had into the line. The ST-35 sits in the tactical-strike slot between the soldier-portable kamikaze quadcopters that infantry now improvise daily and the heavier, longer-ranged systems Ukraine sources abroad — a purpose-built loitering munition for company- and battalion-level commanders who need to reach behind the contact line and hit a specific armoured vehicle or firing point.

Mechanically, the ST-35 is unusual. Rather than a fixed-wing airframe launched from a catapult, it ships in a sealed tubular container and is fired vertically, transitioning to horizontal flight on small electric rotors that give it roughly an hour of endurance and a working radius of around 30 kilometres at altitudes up to about 1,500 metres. Navigation is inertial with satellite correction, and the airframe carries an electro-optical and infrared sensor that streams video to the operator’s ruggedised console. The terminal phase is operator-in-the-loop: the munition can fly an autonomous route to a designated grid, but a human picks the aimpoint on the live feed before commit. Its payload is a tandem-shaped-charge warhead in the three- to four-kilogram class, sized to defeat reactive armour on main battle tanks as well as bunkers and lightly fortified positions.

Ukraine is the only confirmed operator. Open-source footage from 2023 onward has shown Silent Thunders striking Russian artillery, air-defence vehicles and dug-in infantry along the southern and eastern fronts, and the system has been folded into the broader Ukrainian portfolio of indigenous strike drones alongside the Warmate variants license-produced locally and the heavier RAM II family. Athlon Avia has not published production numbers, and the unit cost has not been disclosed publicly; what is documented is steady serial output funded in part through the United24 platform and direct ministry-of-defence contracting.

The ST-35’s distinctive niche is its vertical launch and tube packaging. Most loitering munitions in its weight class need a catapult or a runway; the Silent Thunder can be set up by a two-person team in a treeline and fired without any infrastructure that would betray the launch site to Russian counter-battery radar. That portability, paired with a warhead heavy enough to threaten armour, is what keeps it in active rotation more than three years into a war that has driven Ukrainian drone design harder and faster than any conflict before it.