Vikas

The Vikas is the hard-working liquid-fuel rocket engine at the heart of nearly every Indian space mission. If India’s rockets have a reliable engine they reach for again and again, this is it.

Quick facts

• Made by: India’s space agency, ISRO, through its Liquid Propulsion Systems Centre (LPSC).
• Type: A liquid-propellant engine (it burns liquids, not solid powder) that uses a gas-generator cycle and can swivel to steer the rocket.
• Fuel and oxidizer: A hydrazine-family fuel called UDMH or UH25, burned with nitrogen tetroxide (N2O4) as the oxidizer.
• Thrust (push): About 725 kilonewtons in early versions, rising to roughly 800-821 kilonewtons in the High Thrust Vikas Engine (HTVE).
• Specific impulse (fuel efficiency): About 293 seconds in the vacuum of space, about 262 seconds at sea level.
• Burn time (in the LVM3 core stage): Roughly 200-203 seconds.
• Named after: Vikram Ambalal Sarabhai, the founder of India’s space program.

What it is and how it works

The Vikas burns two liquids that ignite the instant they touch each other. This property is called hypergolic, and it means the engine needs no spark plug or igniter to light. One liquid is the fuel (UDMH or UH25); the other is the oxidizer (nitrogen tetroxide), which supplies the oxygen the fuel needs to burn in space, where there is no air.

To force these liquids into the engine fast enough, the Vikas uses a gas-generator cycle. A small amount of propellant is burned in a side chamber called a gas generator. The hot gas it makes spins a turbopump (a turbine-driven pump), and that pump shoves the main fuel and oxidizer into the combustion chamber at very high pressure, around 52 to 62 bar (dozens of times normal air pressure). The burning gases then rush out through a nozzle, and that backward blast pushes the rocket forward.

Both propellants are storable, meaning they stay liquid at ordinary room temperature. Think of the difference between bottled water you can keep on a shelf and ice you must keep frozen: storable fuels can be loaded into the rocket and held there, ready, until launch. The whole engine is gimbaled, meaning it can tilt slightly to point the thrust and steer the vehicle.

Why it matters

The Vikas gave India self-reliance in liquid rocket propulsion. Its story began in 1974, when France’s SEP agreed to share its Viking engine design in exchange for about 100 person-years of Indian engineering work. A team led by Nambi Narayanan hot-tested the first fully Indian unit in 1985, and over time imported French parts were replaced with home-built ones.

The design involves trade-offs. The propellants are highly toxic and corrosive, so they must be handled with great care. In return, they are storable and ignite reliably on their own, which keeps the engine simple and ready to fly. The gas-generator cycle is likewise sturdier and simpler than fancier designs, though slightly less fuel-efficient.

A human-rated version, the L110-G, was qualified for India’s first crewed program, Gaganyaan: nine engines passed 14 hot tests totaling 1,215 seconds, finishing on April 6, 2023. In 2025, ISRO even demonstrated an in-flight-style restart (fire, pause two minutes, then reignite), a step toward future reusable rockets.

Where it is used

• PSLV (Polar Satellite Launch Vehicle): one Vikas powers the second stage.
• GSLV Mk I and Mk II: Vikas powers the second stage plus four liquid strap-on boosters.
• LVM3 (GSLV Mk III): the core stage runs two clustered High Thrust Vikas engines.
• Gaganyaan (human-rated LVM3-G): two human-rated L110-G Vikas engines power the liquid core.
• Mission heritage: Mangalyaan (Mars Orbiter Mission) and the Chandrayaan lunar missions all flew on Vikas-powered rockets.