ISRO terminates the test firing of its most-powerful rocket engine owing to an unforeseen technical issue

Due to an unforeseen technical problem, the Indian Space Agency ISRO had to prematurely end the test firing of its most powerful rocket engine. While this is a minor setback, ISRO has been working for several years on the development and operationalization of its maiden semi-cryogenic rocket engine. The initial test firing was intended to last 4.5 seconds and aimed to assess the subsystems of the newly developed semi-cryogenic engine. However, ISRO decided to terminate the test as a precautionary measure when there was an unexpected deviation in the test parameters at the two-second mark.

The test was conducted on an intermediate configuration of the Semi-cryogenic Engine, known as the Power Head Test Article (PHTA), which is powered by kerosene and liquid oxygen. It took place at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu. The PHTA represents the first hardware test of the engine development program and is designed to provide a thrust of 2000 kN. This engine is envisioned to be used in the booster stages of future launch vehicles, enhancing the lifting capability of India’s heaviest rocket, the LVM3.

ISRO explained that the objective of the test was to validate the integrated performance of critical subsystems such as the gas generator, turbo pumps, pre-burner, and control components by conducting a short-duration hot-firing for 4.5 seconds. The focus was on igniting and generating hot gas within the pre-burner chamber, which drives the main turbine to power the fuel and oxidizer pumps.

During the test, everything proceeded as predicted until 1.9 seconds, confirming the ignition and subsequent performance of the PHTA. However, at the 2.0-second mark, an unexpected increase in turbine pressure and subsequent loss of turbine speed occurred. As a precaution, the test was terminated. ISRO stated that further analysis is underway to gain a better understanding before proceeding with longer-duration hot tests.

ISRO had initiated fuel flow testing of this engine at the IPRC facility in May 2023, and a series of test firings were planned to demonstrate its performance. While an anomaly was observed in the latest test, it is important to recognize that engine development and testing is a complex and time-consuming process that requires significant effort.