On Monday, the Indian Space Research Organisation (ISRO) embarked on a first-of-its-kind test — hoisting into space what is essentially a scale model of what would be India’s indigenously designed space shuttle. The 6.5m-long Re-usable Launch Vehicle–Technology Demonstrator (RLV-TD) weighs about 1.75 tonnes and is the result of more than a decade of development costing around Rs 95 crore.
According to ISRO, the RLV-TD lifted off from Sriharikota and touched a peak altitude of over 65 km before its splashdown about 450 km away, in a mission that lasted about 770 seconds.
In a pre-launch interview to Pallava Bagla, Dr K Sivan, director of the Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram, and a key force behind the RLV-TD, reveals why ISRO is forging ahead where other powers have failed. Excerpts:
How many countries have tested vehicles that are similar or resemble the space shuttle?
Already, four countries have done this, the US, Japan, France and Russia. They have tested this type of vehicle. The US retired its space shuttles in 2011 and Russia flew once long ago.
In further tests, you will have to put an undercarriage to make it land, maybe in Sriharikota or a new spaceport. Is that the plan?
We have already identified the area where we are going to land this space shuttle, at Sriharikota where a 5-km-long runway will be made.
What benefit does India get by using a winged vehicle?
Mainly, the first and foremost benefit we get is reduced cost of launching satellites. Because right now, the most precious is hardware for which we spend about 80 per cent of the cost, which is then thrown into the sea. However, suppose we are able to recover and reuse it, that way we can reduce the cost of launching. That is what we are going to achieve from this mission.
We have spent about Rs 95 crore on this vehicle for its test. Are those prices likely to come down now? Is the ultimate aim low-cost access to space? If so, is this a baby step, or a leap?
Yes, that is the ultimate aim, reducing cost of access to space… I would say, it’s both. It’s a baby step in the reusable launch vehicle technology demonstrations. At the same time, it’s a big leap in the new technological development for ISRO. So it is a baby step for the reusable launch vehicle area, and at the same time, a big leap in technology development.
How much time did it take to reach this stage of having a winged spacecraft, the RLV–TD, ready for a test?
We took about 10 years to develop the model. We needed to do a lot of technological development, like materials development, thermal protection system development, propulsion system development. Most importantly, the configuration of a reusable launch vehicle is crucial. Because this particular vehicle is going to operate in a very wide Mach range from 25 to zero, so having a single configuration meeting all the requirements is very difficult. Therefore, defining a configuration for a hypersonic wave flight, and its validation and how it is to be manoeuvred to bring to a defined point is a challenge and the key objective of this mission.
What were the new materials needed to develop this flight model?
One particular material is called carbon-carbon composite, a special heat resistant material. This is used because during re-entry, the vehicle faces the friction of atmosphere — the first portion that is going to face a severe thermal environment of around 750 degree Kelvin will be the nose cone. Internally, it will become hot because this material faces the atmosphere. Therefore, the high temperature from outside will not be passed on inside. The other is heat-resistant silica tiles, a very light material that is rainproof.
Is the underbelly coated with special tiles?
Basically, when the vehicle enters the atmosphere, it will have a high angle-of-attack. It is the belly area that faces the atmosphere; hence, this area should be protected. That is why thermal protection tiles have been put on the entire belly region. The outside temperature would be 750 degrees Kelvin but the inside will still be cool.
How much payload can it carry to space?
The ultimate reusable launch vehicle should be able to carry something like 10-15 tonnes into the low earth orbit.
Why are we doing a winged body test?
When the vehicle re-enters from orbit, we have to dissipate energy and reach a particular specific point. Now, to dissipate energy we need drag. Along with that, to make the vehicle land, we want a controlled system and in this mission, this is controlled by lift. For a higher lift, the option is to have wings, the same way an airplane gets its lift. The same Bernoulli’s principle will apply here. This RLV-TD has a hypersonic-winged body with full aero control; it is the first time India is attempting it.
