India, New Delhi: Today morning, the Reusable Launch Vehicle — Technology Demonstrator (RLV-TD) launched by the Indian space agency has led to lot of euphoria. Much of it has to do with the fact that the Indian Space Research Organisation (Isro) has for the first time launched a winged body into space.
The excitement is greater because this winged body resembles American space shuttle which is ingrained in popular imagination for three decades.
While any comparisons with space shuttle which carried humans into space are preposterous, RLV-TD nevertheless represents a significant experiment in space transportation for Isro. For a space agency which has earned global recognition as a frugal player with its cost-effective missions to the moon and the Mars, it is logical to strive for further reduction in cost of launching satellites. That’s what RLV is – an experiment to explore reducing cost of launching satellites by recovering some of the space assets.
At present, Isro uses Polar Satellite Launch Vehicle (PSLV) and Geosynchronous Satellite Launch Vehicle (GSLV) to place satellites in different orbits. These are Expendable Launch Vehicles (ELVs), meaning they get burnt up after propelling satellites into space. Every time you want to launch a satellite, you need a new rocket. Therefore, it is a costly affair. RLVs, as the name suggests, can be reused. An RLV, like the one tested on Monday, would still need a propeller or rocket to boost it into space but it can return after placing a satellite into orbit and can be used for next launch, at least theoretically. The rocket to be used to launch RLV depends on which orbit one wants to place the satellite into. If a satellite has to be placed into a low earth orbit (LEO), RLV will need just one propeller — single-stage-to-orbit (SSTO). For reaching higher orbits, two-stage-to-orbit (TSTO) type RLV will have to be used.
Reusability of space assets is the holy grail of space business. Developing an RLV is not an easy task and Isro has been at it for more almost a decade now. It requires several cutting edge technologies to develop an object that can go to space and safely return to the earth. One of the biggest challenges is re-entry – the point where RLV enters the earth’s atmosphere on its return journey. At the reentry point, RLV is subjected to temperatures going up to 2000 degrees and it should be able to survive this heat. For this Isro has developed special reusable thermal protection systems consisting of tiles that can protect RLV at reentry.
The objective of Monday’s flight was to test one of the building blocks of a functional RLV in future – test hypersonic aero-thermodynamic characterisation of the winged body’s re-entry, its control and guidance systems, autonomous management systems that enabled it to land a specific location and testing, besides testing “hot structures” that make up the structure of the RLV. That’s why it was named Hypersonic Experiment 1 (HEX-1). A series of such experiments will have to be carried out to test different systems before an Indian RLV capable of placing satellites into orbits can be realised.
The RLV on Monday landed in Bay of Bengal and disintegrated, so it is not reusable. To make it reusable, it has to make safe landing on a runway which India does not have currently. Isro plans to build one, perhaps at Sriharikota itself. In the next testing of RLV, Isro will test its landing capability, especially its turbofan engine. In this experiment, RLV will be launched, it will re-enter the atmosphere at hypersonic speed and use aerodynamic breaking to decelerate. It will then turn towards a landing site, start its turbofan engine and cruise at lower speeds to land horizontally on a runway. The third experiment would involve launching into an orbit and then de-orbiting for a landing on a runway. ISRO also plans to work on Scramjet Propulsion Experiment – an experiment to test an RLV-TD fitted with an air breathing scram jet engine.