Gaganyaan: ISRO Successfully Conducts Second And Third Hot Tests Of Service Module Propulsion System, Three More Remain

Gaganyaan Mission: Hot tests of the Gaganyaan Service Module Propulsion System are important because they will help determine the performance of the orbital module.

Gaganyaan: The second test lasted 723.6 seconds, and focused on demonstrating Orbital Module Injection, and the identification of non-operational engines. This means that the test was aimed at showing how the orbital module will be injected into orbit. ( Image Source :ISRO )

Gaganyaan: The Indian Space Research Organisation (ISRO) successfully conducted the second and third hot tests of the Gaganyaan Service Module Propulsion System (SMPS) on July 26, 2023, at the ISRO Propulsion Complex (IPRC) in Mahendragiri, Tamil Nadu. A week before, on July 19, the first hot test of the SMPS was performed. These tests are important because they will help determine the performance of the orbital module. All three tests are a part of the Service Module - System Demonstration Model (SM-SDM) Phase-2 test series, the Indian space agency said on its website. 

The service module consists of the main propulsion engine, while the orbital module contains the habitat in which the crew will stay while in orbit.

The Liquid Propulsion System Centre (LPSC), located at Bangalore and Valiamala, Thiruvananthapuram, has designed and developed the SMPS. 

Gaganyaan Mission:

Two more hot tests on the Gaganyaan Service Module Propulsion System were conducted successfully at IPRC/ISRO on July 26, 2023.

Tests were conducted in pulsed and continuous modes necessary for the mission.

Three more hot tests are scheduled to demonstrate… pic.twitter.com/Vn7BrzbpHE

— ISRO (@isro) July 27, 2023

All about the second and third tests of the Service Module Propulsion System

As part of the second and third tests, teams operated the thrusters in both continuous and pulse mode, similar to the ways in which the thrusters will run during the actual mission. The second test lasted 723.6 seconds, and focused on demonstrating Orbital Module Injection, and the identification of non-operational engines. This means that the test was aimed at showing how the orbital module will be injected into orbit. In order to identify and isolate non-operational engines, a calibration burn was performed, as part of which 100 Newton thrusters and Liquid Apogee Motor engines were tested. Liquid Apogee Motor engines are chemical rocket engines used as the main engine in a spacecraft. Such an engine is controlled by two electrically-driven valves which provide thrust. 

During the second test, the Liquid Apogee Motor engines and the reaction control system thrusters performed as expected. A reaction control system enables a spacecraft to maintain attitude control and steering with the help of thrusters. 

The third test of the SMPS lasted 350 seconds. The aim of the test was to demonstrate the "circularisation" of the Orbital Module to achieve the final orbit. Circularization is a term coined by NASA to describe the moment a spacecraft enters its circular orbit around Earth. The thrust from the orbital manoeuvring system controls circularization. As part of the third test, Liquid Apogee Motor engines were operated in continuous mode, and the reaction control system thrusters were operated in pulse mode.

As part of the first hot test, five Liquid Apogee Motor engines were powered with a thrust of 440 Newtons. As many as 16 reaction control thrusters, which had a thrust of 100 Newtons ,were tested. 

Ahead of the first leg of the Gaganyaan mission, three more hot tests must be performed to demonstrate de-boosting and other mission scenarios. ISRO can assess the readiness of the SMPS through these tests. 

Gaganyaan's service module will use two types of propellants. The service module will help the Gaganyaan spacecraft perform orbit injection and manoeuvres, and will allow the mission to be aborted in case of any mishap during the ascent phase. 

The service module will receive the main propulsion force during the ascending phase with the help of the liquid apogee motor engines.

Three flights will be sent to low-Earth orbit as part of the Gaganyaan Programme. These include two unmanned flights and one human spaceflight.