For future missions, ISRO will have to turn to the Geosynchronous Satellite Launch Vehicle (GSLV) and GSLV Mark III that can lift much heavier spacecraft than the PSLV.

After the stunning success of its very first shot at Mars, the Indian Space Research Organisation (ISRO) will need to take those capabilities forward, despatching bigger, and more advanced spacecraft in the years to come. That, in turn, requires rockets that can carry such probes on the first leg of their journey and place them in orbit around Earth.

For its first attempt with the Mars Orbiter, ISRO turned to the Polar Satellite Launch Vehicle (PSLV), a rocket with an impeccable track record. Initially, it seemed that this launcher would not be powerful enough for the task and every aspect of the mission had to be carefully optimised in order to make that possible, according to V. Adimurthy, the space agency's senior adviser for interplanetary missions. He led a study team whose 2011 report laid out how India could send probes to the Red Planet.

For future missions, ISRO will have to turn to the Geosynchronous Satellite Launch Vehicle (GSLV) and GSLV Mark III that can lift much heavier spacecraft than the PSLV. The former, equipped with an indigenous cryogenic stage, had its first successful flight only in January this year. An experimental launch of the Mark III, with a non-functional cryogenic upper stage, is to take place shortly. (The rocket’s operational cryogenic engine and stage are still under development.)

ISRO needed to carry out a system study of how the GSLV and GSLV Mark III launchers could be used to carry probes for Mars, observed its chairman, K. Radhakrishnan “Certainly for the next mission we have to go for [a spacecraft with] higher mass.”

The space agency would not be in a position to send a spacecraft to that planet during the 2016 launch opportunity, he told this correspondent. The launch window that opened in 2018 would be the earliest that the next mission to Mars could go. It was also necessary to be clear what science such a mission could carry out, he added.

In order to utilise the GSLV and GSLV Mark III, the cryogenic engines on those rockets will need ‘multi-start’ capability so that they can be shut down after one burn, undergo a period of coasting and restart, noted Dr. Adimurthy. This was crucial for placing a spacecraft in the proper orbital orientation around Earth, a prerequisite for its eventual injection on a trajectory to Mars. A new liquid propulsion stage for carrying out the trans-Mars injection too was needed.

“Such improved systems will eventually pave the way for larger spacecraft to go into orbits closer to Mars, and have lander and rover operations on the planet’s surface,” he said.

Starting, shutting down and restarting a cryogenic engine in space is complicated, noted S. Ramakrishnan, who retired recently as director of the Vikram Sarabhai Space Centre, ISRO’s lead centre for launch vehicle development, and earlier headed the Liquid Propulsion Systems Centre that develops liquid propellant engines needed for the space programme.

Restart capability has not yet been demonstrated with the GSLV’s cryogenic engine. As for the cryogenic engine being developed for the Mark III, “once we do the initial engine-level tests, we can look at introducing the restart capability,” he remarked.

ISRO has designed and ground-tested a ‘Payload Assist Module’ using a liquid-propellant engine that powers the PSLV’s fourth stage. This module had originally been developed so that the GSLV could launch Russia's Global Navigation Satellite System (GLONASS) satellites, a proposal that ultimately did not materialise.

The module could go atop the GSLV or GSLV Mark III and enhance their capabilities to send probes to Mars, said Mr. Ramakrishnan.