The RLV-TD test flight that took place on 2016. (Image credit: ISRO)

The Indian space agency is literally growing new wings as it gets ready to test a scaled down version of what can easily be described as the `swadeshi Space Shuttle'. The Indian Space Research Organisation (ISRO) calls it the `Reusable Launch Vehicle' or RLV. If all goes to plan very soon it will be seen flying over the Science City in Challakere, Karnataka, where the first landing experiment is being planned. S Somanath, Chairman, ISRO says "We are working silently on reusable rocket technology, with a very low budget, low cost and low investment."

An artist's impression generated by ISRO of India's `swadeshi Space Shuttle' flying in space. (Image credit: ISRO)

In the past USA and Russia have flown full-fledged winged space vehicles. Russia/USSR flew its vehicle called `Buran' only once in 1988 and the program was then shelved. USA made 135 flights of the Space Shuttle and in 2011 it was retired. Since then in a new burst of energy, USA, China and India are the only countries having an active program of re-useable rocket development. If all goes as per plan India's full-fledged test of reusable launch vehicle may happen only in the 2030's. ISRO's reusability is far more ambitious than the rocket stage recovery experiments carried out by Space X and hence it will take time to fully master.

The Reusable Launch Vehicle – Technology Demonstrator as seen in 2016 being carried to the launch site. (Image credit: ISRO)

The new bird will weigh nearly four tonnes and it will be hoisted into the sky on a helicopter and then it will be released from about an altitude of about three kilometres and from a distance of three kilometres from the runway. "The vehicle then has to navigate, glide and successfully land unpiloted and autonomously at the defence runway in Challakare" says Somanath. This experiment using the scaled down version is called Reusable Launch Vehicle – Landing Experiment or the RLV – LEX. This is essentially an air drop test to understand the aerodynamics of the air frame which has been developed in-house by ISRO.

The Reusable Launch Vehicle – Technology Demonstrator as seen in 2016 being assembled by technicians of ISRO. (Image credit: ISRO)

As part of the development program for reusable rockets way back on May 23, 2016, ISRO had successfully tested the Reusable Launch Vehicle – Technology Demonstrator (RLV-TD) when a 1.75 tonne orbiter was hoisted into a sub-orbital flight on a special rocket some 65 kilometres above the Bay of Bengal from Sriharikota. The flight lasted for 773 seconds and attained the maximum velocity of Mach 5 or five times the speed of sound. The physical landing was conducted on a simulated runway some 450 kilometres away from Sriharikota on water. On this hypersonic landing experiment in 2016, the RLV-TD HEX, was not designed to float and it sank into the sea. ISRO called it 'successful' and the era of reusability was born of the Indian space agency. Since then engineers at the Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram have been steadily working to master this complex technology.

The configuration of the reusable Launch Vehicle – Technology Demonstrator for its 2016 flight. (Image credit: ISRO)

Most recently, three attempts have been made already to test the glide capability and the last attempt in April, 2022 got aborted because a cyclone and heavy winds played havoc at the landing site. Somanath says there is one small window available to do this unique experiment before the monsoon hits the Chitradurga district and all efforts are being made to make sure it happens successfully.

Indian space scientists are trying to master a far more complex reusable rocket says Somanath, since ISRO wants to learn how to recover, bring back to Earth the upper stage of the rocket, which is usually lost in space. "The upper stage of the rocket has the most complex and most expensive electronics and if one can recover the upper stage it would certainly bring down the cost of rocket launching dramatically, also reduce space debris", explains Somanath. In contrast the much touted reusable rocket demonstrations done by Space X are only of the lower stages of the rocket which are essentially metal blanks and comparatively much cheaper as they do not house expensive electronics.

A schematic of the rocket booster and The Reusable Launch Vehicle – Technology Demonstrator. (Image credit: ISRO)

The 'Swadeshi Space Shuttle' is really a two stage to orbit vehicle. The reusable winged vehicle sits vertically atop a rocket which boosts it into space and parks it into an orbit. Once that is done the winged vehicle separates and orbits the Earth. As its cooking in Kerala the plan is that once the mission is completed, the mission control centre sends commands to the still in orbit `swadeshi space shuttle' for it to de-orbit and then successfully land at runway that may be built at Sriharikota.

The view of the lift off of The Reusable Launch Vehicle – Technology Demonstrator as seen on May 23, 2016 from Sriharikota. (Image credit: ISRO)

Sounds very easy but to make rocket leave its orbit and survive the dense atmosphere where the heat generated due to friction can push temperatures on the surface to about 3000-4000°C needs mastering of complex materials and the software has to be robust to handle autonomous landing. Light weight heat resistant silica tiles and carbon-carbon reinforced tiles have already been developed by ISRO. If the landing experiment succeeds, the next big milestone will be to conduct a re-entry experiment where the scaled down model of RLV will orbit the earth and then be brought back to India.

If robotic re-usable vehicles is mastered by India then expensive satellites whose fuel has been exhausted could be plucked back and brought back to send again, costly observation platforms can be used again and again, the uses are many and bringing down cost of access to space is just one factor. In future pharmaceutical compounds could be made in near zero gravity environments, biological experiments could be done and recovered from space and who knows even human organs could be grown in space and brought back to Earth asserts Somanath.

A schematic of the flight path the Reusable Launch Vehicle – Technology Demonstrator took in 2016 on its maiden successful launch. (Image credit: ISRO)

"The upper stage of the rocket is very precious there are also huge strategic advantages of mastering reusability of the ultra-expensive upper stage", says Somanath. India is steadily working to master this important technology so that the country is not left behind in the space race of developing economical and frugal space technology.

Pallava Bagla is a science writer and co-author of the books 'Destination Moon', and 'Reaching for the Stars: India's Journey to Mars and Beyond'.

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