SOURCE: IDRW.ORG
In a significant step toward India’s first private orbital rocket launch, Hyderabad-based Skyroot Aerospace announced on April 28, 2025, that the Composite Nozzle and Flex Nozzle Control (FNC) System for the Vikram-1 rocket’s Stage-1, named Kalam-1200, have successfully passed their pre-flight tests. This critical “steering system” for thrust vector control is now ready for integration with the motor, paving the way for an upcoming static fire test and the much-anticipated Vikram-1 launch.
The achievement, celebrated in posts on X by Skyroot’s CEO Pawan Chandana and the company’s official handle, underscores India’s growing prowess in private space exploration and positions Skyroot as a trailblazer in the global small-satellite launch market. Here’s a deep dive into this milestone, its technical significance, and what it means for Vikram-1’s journey to orbit.
The Vikram-1, named after ISRO founder Vikram Sarabhai, is a three-stage solid-fuel rocket designed to deliver up to 480 kg to a 500 km Low Inclination Orbit. Its first stage, Kalam-1200, is a 10-meter-long, 1.7-meter-wide carbon composite structure delivering a peak thrust of 1,200 kN (120 tons), making it the largest propulsion system ever built by India’s private sector. The stage’s Composite Nozzle and Flex Nozzle Control System are critical for steering the rocket through Earth’s atmosphere, countering aerodynamic disturbances to ensure a stable trajectory into space.
The FNC system features:
Composite Nozzle: A carbon ablative flex nozzle, standing as tall as a human and weighing over a ton, designed to withstand extreme combustion temperatures of ~3,000°C while directing exhaust gases at supersonic speeds. Its lightweight, high-strength carbon composite construction enhances performance by reducing mass compared to traditional steel nozzles.
Power Electronics: Capable of managing large currents and voltages, these ensure rapid and precise operation of the system under intense flight conditions.
Electromechanical Actuators: High-capacity actuators drive the flex nozzle’s movements, enabling dynamic adjustments to thrust direction. These actuators respond to commands from the mission computer, tilting the nozzle to maintain the rocket’s desired path.
Flex-Seal Mechanism: A ball-joint-like system that allows the nozzle to pivot within the combustion chamber, providing precise thrust vector control to counter winds, turbulence, and other forces during ascent.
Skyroot’s announcement on X highlighted the system’s successful qualification: “Great power demands precise control! The Composite Nozzle and Flex Nozzle Control System of Vikram-1’s Stage 1 (Kalam-1200) just aced their pre-flight tests. This ‘steering system’ to thrust vector the rocket is now ready for integration with the motor for the upcoming static fire test.” CEO Pawan Chandana added, “We successfully qualified the robust Flex Nozzle Control (FNC) system for Stage-1… driving high-capacity electromechanical actuators with rapid response to enable precise control of a massive flex-nozzle.”
The successful pre-flight tests of the Kalam-1200’s FNC system mark a critical validation of one of the rocket’s most complex components. Thrust vector control is essential for maintaining stability during the initial ascent, where the rocket faces maximum aerodynamic stress. The flex nozzle’s ability to pivot ensures the Vikram-1 can correct its trajectory in real time, countering disturbances like crosswinds or uneven thrust. The system’s power electronics and actuators, tested for rapid response under high-voltage conditions, demonstrate reliability in managing the massive forces generated by the 1,200 kN thrust.
The carbon composite nozzle, a technological marvel, is five times lighter than steel equivalents yet withstands extreme pressures (82.5 atmospheres, tested in December 2023) and temperatures. Its integration with the flex-seal, validated in these tests, ensures precise maneuvering, a capability Skyroot likened to “a ball-joint connection in a car’s suspension” in a February 2024 post. The tests, conducted with cutting-edge sensors capturing extensive data, confirm the system’s readiness for the static fire test, where the entire Kalam-1200 stage will be fired to simulate launch conditions.
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