The ISRO’s Space Capsule Recovery Experiment and Crew Module Atmospheric Re-entry Experiment were key for the success of the TTV-D1 flight

There were two important forerunners to the success of the Test Vehicle Abort Mission (TV-D1) flight that the Indian Space Research Organisation (ISRO) conducted on October 21. During the test, an uncrewed crew module was brought back safely to the earth after launching it on a small rocket and simulating an emergency abort command. The test and its forerunners are ISRO’s first major steps towards launching humans to orbit as part of its ‘Gaganyaan’ mission.

The TV-D1 test was carried out smoothly, especially given that ISRO had to overcome a glitch five seconds before lift-off at 8.45 am, when the ground computer, called the Automatic Launch Sequence, halted the lift-off. ISRO Chairman S. Somanath said it issued a “hold” when it detected a non-conformity “for allowing the engine to continue thrusting to further go. This happened due to a monitoring anomaly in the system.” He added: “We could identify [the anomaly] very, very fast and correct it … It took us some time to refill the gases…”, after which the launch was rescheduled for 10 am.

First Forerunner

The first forerunner to the TV-D1 mission was ISRO’s Space Capsule Recovery Experiment (SRE-1). An orbiting satellite called SRE was brought back to the earth on January 22, 2007, after a Polar Satellite Launch Vehicle (PSLV) had placed it in orbit on January 10. In a series of manoeuvres, the shuttlecock-shaped SRE came down from an altitude of 635 km to splash down into the Bay of Bengal, 140 km from Sriharikota, where the Coast Guard recovered it. India thus successfully brought back an orbiting satellite in its first attempt.

The descent manoeuvres included sophisticated braking systems, deceleration techniques, and the deployment of parachutes. Overall, the SRE-1 mission showcased ISRO’s mastery of re-entry technology. B.N. Suresh, former Director of the Vikram Sarabhai Space Centre, Thumba, said, “The satellite looked as fresh as it was when we gave it for integration with the PSLV for the launch”, after it survived its fiery reentry.

SRE-1 was India’s first big step towards sending an Indian astronaut into space and bringing them back safely. Former ISRO Chairman G. Madhavan Nair had said, “This is a humble step towards sending an Indian into space.” B.R. Guruprasad, a former ISRO official and a science writer, had said then, “Nothing symbolises the ascent of India in science and technology as the return of SRE-1.”

Second Forerunner

The second forerunner to the TV-D1 mission happened on December 18, 2014, when the Launch Vehicle Mark 3 (LVM-3) placed the 3.75-ton uncrewed crew module in a sub-orbital altitude of 126 km, and left it to descend. The module knifed through the earth’s atmosphere and also survived re-entry. Its parachutes deployed and soon it was bobbing in the Bay of Bengal, about 700 km from Port Blair. This test, called Crew Module Atmospheric Re-entry Experiment (CARE), marked India’s second step towards sending its astronauts into space and getting them back.

Dr. Guruprasad pointed out that while the SRE weighed about 555 kg, the uncrewed crew module in CARE weighed nearly seven-times as much. In TV-D1, the module weighed 200 kg more, a full four tonnes.

TV-D1 also had three other highlights. According to Dr. Guruprasad, they were a standalone liquid booster rocket launching for the first time from Indian soil; the successful performance of the Crew Escape System that pulled the crew module away from the launch vehicle; and the crew module reorienting itself before landing in the Bay.