Agnikul Cosmos has marked a significant milestone in India's private space sector by successfully test-firing three semi-cryogenic rocket engines simultaneously in a clustered configuration.

This historic achievement took place at the company's state-of-the-art Rocket Factory-1, showcasing the firm's prowess in indigenous design and manufacturing.

Each of the three engines represents a feat of advanced engineering, having been 3D-printed as single, monolithic pieces of hardware. This innovative approach eliminates the need for complex multi-part assemblies, reducing potential failure points and streamlining production processes. The engines were conceived, designed, and fabricated entirely in-house, underscoring Agnikul's commitment to self-reliance in propulsion technology.

Powering these engines are electric motor-driven pumps, a hallmark of Agnikul's propulsion systems. This electrically driven architecture offers precise control, higher efficiency, and reduced complexity compared to traditional pressure-fed or turbopump systems commonly used in semi-cryogenic engines. It aligns with the company's vision for scalable, reusable rocket technology tailored for small satellite launches.

The test demanded meticulous calibration of six pumps and six electric motors, alongside fine-tuning six independent speed control algorithms. Engineers synchronised these components to ensure uniform performance across startup, steady-state operation, and shutdown phases. Achieving such harmony in a clustered setup is no small task, as it requires real-time adjustments to maintain thrust balance and prevent oscillations that could destabilise the vehicle.

To the best of Agnikul's knowledge, this marks the first instance in India where semi-cryogenic engines have undergone such a clustered hot-fire test. Semi-cryogenic engines, which utilise liquid oxygen paired with a storable fuel like kerosene, bridge the gap between conventional and fully cryogenic systems, offering a balance of performance and operational simplicity. This test validates their viability for orbital launch vehicles.

The successful firing demonstrates Agnikul's mastery over multi-engine clustering, a critical capability for medium-lift rockets. Clustering allows for scalable thrust, enabling vehicles to handle heavier payloads or achieve greater velocities. In the Indian context, where ISRO has long dominated cryogenic and semi-cryogenic development, this private sector breakthrough signals accelerating innovation.

Conducted at Rocket Factory-1 in Chennai, the test leveraged Agnikul's integrated manufacturing ecosystem. The facility houses advanced 3D metal printers capable of producing engine components in days rather than months, a game-changer for rapid iteration in rocket development. This in-house vertical integration minimises supply chain dependencies and accelerates timelines.

The electric pump-fed design further distinguishes these engines. Unlike gas-generator cycles, electric pumps draw power from high-energy-density batteries or regenerative sources, enabling throttleability down to low percentages of nominal thrust. This is particularly advantageous for precise manoeuvres during launch and landing in reusable rocket architectures.

Calibration challenges were substantial, involving sensor fusion from pressure transducers, flow meters, and temperature probes across the cluster. Algorithms had to compensate for minor variances in pump efficiencies and motor responses, ensuring each engine contributed equally to the total thrust—estimated in the range of tens of kilonewtons per unit, though exact figures remain proprietary.

Uniform startup sequencing prevented hard starts or pressure spikes that could damage nozzles or combustion chambers. Steady-state operation maintained thermal equilibrium, averting hotspots in the regeneratively cooled throats.

Controlled shutdowns ensured propellant draining without residual combustion, preserving engine longevity for future flights.

This test paves the way for Agnikul's Agnibaan launch vehicle, a two-stage rocket capable of placing 100 kg payloads into 700 km sun-synchronous orbits. Integration of this clustered first-stage engine will provide the requisite impulse for suborbital and eventually orbital missions, positioning Agnikul as a contender in the smallsat launch market.

India's space ecosystem benefits immensely from such advancements. With ISRO focusing on heavy-lift platforms like PSLV and GSLV, private players like Agnikul fill the niche for responsive, low-cost launches. Government initiatives such as IN-SPACe and relaxed FDI norms have catalysed this growth, fostering a vibrant start-up landscape.

Globally, the feat draws parallels with clusters like SpaceX's Raptor engines or Rocket Lab's Rutherford motors, both of which employ electric pumps. However, Agnikul's single-piece 3D printing sets it apart, potentially lowering costs to under $1 million per engine at scale—a fraction of traditional machining expenses.

Challenges ahead include scaling to flight qualification, incorporating vehicle-level avionics for gimballing, and certifying for human-rated missions under emerging standards. Environmental considerations, such as minimising hypergolic residuals in semi-cryo fuels, will also shape future iterations.

Agnikul's team, comprising aerospace engineers and propulsion specialists, executed the test with zero anomalies over multiple runs. Telemetry data confirmed thrust vector alignment within 0.5 degrees and chamber pressures stable at design values, validating simulation models used in development.

This achievement reinforces India's strides towards Atmanirbhar Bharat in space technology. As private firms like Skyroot and Agnikul mature, they complement ISRO's efforts, promising a dozen annual launches from Indian soil by decade's end.

Looking forward, Agnikul plans static fires with the full Agnibaan first stage by mid-2026, followed by maiden orbital attempts. Such milestones not only de-risk technology but also attract international payloads, bolstering India's space economy projected to reach $13 billion by 2025.

This clustered semi-cryo test exemplifies ingenuity, positioning Agnikul Cosmos at the forefront of global propulsion innovation.

IDN (With Agency Inputs)