SAS «Soyuz»: principles of emergency rescue

Soyuz Emergency Escape Systems: Evolution and How They Work

On October 11, 2018, at 121 seconds into the flight of the Soyuz-FG rocket carrying the Soyuz MS-10 spacecraft, a malfunction occurred during first-stage separation. An off-nominal detachment of a side booster caused it to collide with the core stage, rupturing a fuel tank and leading to loss of stability. The Launch Escape System (LES) activated automatically, pulling the crew module—with cosmonaut Alexei Ovchinin and astronaut Nick Hague—away from the failing rocket. The crew landed safely in the Kazakh steppes with no serious injuries.

The LES provides crew safety throughout the entire active ascent phase, from the launch pad to orbit insertion. It's a sophisticated array of solid-fuel engines, automation, and separation mechanisms, proven in real emergencies and ground tests.

Early Developments: From Vostok to Voskhod

The first crewed spacecraft demanded immediate solutions for crew safety. Vostok used ejection seats: up to 40 seconds by ground command, 40–150 seconds after engine cutoff at 7 km altitude, 150–700 seconds for module separation, and 700–730 seconds for the whole vehicle. The first 20 seconds offered no protection.

For the multi-seat Voskhod, ejection seats didn't fit the layout. The first 44 seconds relied solely on the launcher. Then came jettisoning the fairing with spring pushers and four solid-fuel boosters on the escape tower, followed by module separation.

Key differences in systems:

• Vostok: Individual ejection seats, limited trajectory coverage.
• Voskhod: Full module pull-away, reinforced fairing separation mechanisms.

Creating the LES for Soyuz: Design Choices

Starting in 1961, OKB-1 (later TsKBM, now RSC Energia) developed the 7K spacecraft. Options included a separable launch escape assembly (LEA) or full ejection. They chose the LEA with static stability and lattice fins to minimize g-forces. LES engines came from KB Khimavtomatiki 'Iskra' and the Soyuz Solid Fuel Research Center.

Testing used mockups and rigs. Plans covered three scenarios:

• Failure on the launch pad.
• Loss of stability early in flight.
• Max dynamic pressure zone.

The first unit, E1498, passed tests in December 1966. Fixes addressed resonance and isooctane fires—switched to spacecraft antifreeze from vehicle No. 8. A false LES activation on December 14, 1966, proved its worth: the module landed safely while the launcher exploded.

A successful 7K-L1 block save on Proton in 1967 eliminated the need for costly dynamic pressure tests.

Modern LES on Soyuz MS Spacecraft

Threat monitoring starts 30 minutes pre-launch. The LES triggers from launcher control signals, g-sensor data, or radio command. Ascent is divided into four phases with tailored LEA programs.

Core components:

• 855M propulsion for pulling LEA1 away from the launcher.
• 860M rocket engines on the fairing for LEA1A (post-LES jettison to fairing drop).
• LES automation (ASAS).
• Assemblies on the assembly-protection unit.

Operating programs:

• Program 1 (LEA1): Early failures, full pull-away with central engine.
• Program 1A (LEA1A): Mid-ascent, 860M engines.

ASAS handles the sequence: anomaly detection → separation → deceleration → stabilization → parachutes.

Ground Testing and Reliability

Tests included:

• E1498 simulations: engine plumes, cylindrical heat shield protection.
• Real launches: 1966 false trigger, Proton failure.

Crew g-loads peak at 15–20g briefly, then drop via stabilizers. The Soyuz MS LES saved crews in 1983 (Soyuz T-10-1), 1986 (Soyuz TM), and 2018 (MS-10) incidents.

Key Takeaways

• LES covers the full ascent except the first 20–44 seconds in early versions.
• Automation responds to g-loads, launcher signals, or commands.
• LEA uses lattice fins to cut side loads.
• Solid-fuel 855M/860M engines deliver 100–200 m/s impulse.
• Reliability backed by 5+ real activations with zero crew losses.

— Editorial Team