Recently ISRO was on the news for conducting the first test of the Reusable Launch Vehicle Technology Demonstrator (RLV-TD), which was crowned by media as India’s own space shuttle, a premature epithet, at best.
The main objective behind developing this spacecraft was to test low cost access to space.
Currently, space launches are very expensive. The cost of transporting just 1 kilogram of payload to orbit using a heavy-lift rocket, like Falcon 9, is about $12500 or 8.4 Lakh rupees. For smaller payloads, ISRO uses relatively less powerful rockets like PSLV, but that too costs about $4500 or 3 Lakh rupees per kilogram. This is primarily because of two reasons:
1. The rockets which are currently in service are not reusable – Most of these rockets have 3 or 4 stages which fall back to earth when the rocket reaches certain altitude. After the payload is delivered to the desired orbit, the remaining part of the rocket is discarded which eventually falls back to earth mostly, or sometimes gets lost in space forever.
2. The rockets of today need a humongous amount of fuel to create enough thrust to leave earth’s gravity. Storing more onboard fuel increases the overall weight of the rocket, which is understandably inefficient.
Following NASA’s Footsteps, then..
To overcome the above two problems, in January 2006, ISRO started developing a reusable spacecraft, that is designed to launch vertically like a conventional rocket and return flying horizontally like a regular aircraft, just like NASA’s current space shuttle. This is to take care of the reusability issue of the current systems.
However NASA’s space shuttles are powered by cryogenic engines which use liquid hydrogen (fuel) and liquid oxygen (oxidizer). A cryogenic engine mixes the fuel and the oxidizer in a combustion chamber and ignites the mixture, generating thrust.
A cryogenic engine is very expensive, because producing liquid hydrogen and oxygen are resource intensive processes. Also, the fuel can only be stored in temperature nearing absolute zero, which requires a lot of electricity.
The operating costs of these space shuttles are so high ($450 million, or 3000 crore rupees per launch) that even NASA could not afford it any more. High operating costs was one of the key reasons why NASA shut down the space shuttle program in 2011.
ISRO’s current Technology Demonstrator Vehicle does not have any engines. It was launched using a conventional rocket and was designed to glide back to the Bay of Bengal. The objective of the launch was to test whether the on-board computers could actually enable the shuttle to glide to the pre-designated landing coordinates. The experiment also tested the performance of the heat resistant tiles, that had been used to construct the body of the vehicle. The future RLV experiments will have brand new internal engines.
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