On July 5, the Indian Space Research Organisation (ISRO) conducted “the first in a series of tests” to qualify a module of its human spaceflight programme from its launchpad at the Satish Dhawan Space Centre, Sriharikota. The test was of a crew escape system (CES). According to ISRO, it is “an emergency escape measure designed to quickly pull the crew module along with the astronauts to a safe distance from the launch vehicle in the event of a launch abort” while the rocket was on the launchpad itself.
In all manned missions to space, the crew module – essentially a container housing the astronauts – is installed on the rocket’s uppermost stage. ISRO’s latest test, called a pad-abort, checks whether an escape system installed on the crew module can take it away to safety should the rocket malfunction on the launchpad itself. While the crew module, rather the spacecraft that it’s a part of, has its own engines, these aren’t powerful enough to propel it away within Earth’s atmosphere, necessitating the use of a separate escape unit.
The exercise was designed such that, at the end of a countdown, an unmanned crew module together with a crew escape system would lift off into the atmosphere without any turbulence while also protecting the module’s occupants from harm in the process.
Following a five-hour countdown that ended at 7 am on July 5, such a system (shaped like a tower in the image above) lifted off from the Satish Dhawan Space Centre. It had a launch mass of 12.6 tonnes and stood 14 metres tall. It was powered by seven “quick acting solid motors”, according to ISRO, that had been specifically designed for the occasion. They sent the crew module flying in a giant arc 2.7 km high and 2.9 km wide, at the end of which the module floated down with a pair of drogue parachutes into the Bay of Bengal – all in four minutes and 19 seconds.
“Three recovery boats are being exercised to retrieve the module as part of the recovery protocol,” an ISRO statement released on the occasion concluded.
According to reports published in the New Indian Express and The Hindu in 2016, the pad abort test was originally slated to happen later that year. ISRO has not been forthcoming about the reasons for delay.
This is the second test ISRO has performed as part of its human spaceflight programme. The first was in December 2014, when the organisation launched a GSLV Mk III rocket atop which an unmanned crew module had been installed. It separated from the rocket at an altitude of 126 km, blazed through the atmosphere and dropped into the Bay of Bengal.
Tests conducted by other space agencies suggest that the third one – following atmospheric reentry and pad abort – will be the ascent abort: when the escape system is called upon while the rocket, together with the crew module, is ascending through Earth’s atmosphere and before it has entered space. However, ISRO hasn’t made any announcements about whether it’s preparing for such a test or when it will be.
It’s crucial that space agencies ace all these tests before they can qualify a rocket and the crew module as being safe for use in an operational flight. For example, the pad abort hasn’t been a frequent occurrence in spaceflight history but when it is indeed required, it is crucial that it be pulled off to perfection.
The last time a pad abort was used was on September 26, 1983, when the lives of two Russian cosmonauts onboard a Soyuz rocket were endangered after one of the rocket’s boosters leaked propellant onto the launchpad, leading to a fire that spread to the rocket as well. Engineers on the ground quickly sent a radio transmission to activate the escape system, which fired and flew the 7K-ST module housing the cosmonauts to safety 4km away. Two seconds later, the rocket exploded.