India's hypersonic jets catch attention
18 Aug 2008 06:12:00 PM IST
An Indian double has caught global attention in the hypersonic race for cheap and cost effective launch technology. Bidding for their rightful place among the world’s majors, two of the country’s premier agencies are in the advanced stages of proving scramjet (supersonic combustion ramjet) technology to meet their respective strategic needs.
While the Indian Space Research Organisation (ISRO) is working on the Reusable Launch Vehicle (RLV) for launching satellites, the Defence Research and Development Organisation (DRDO) is dreaming about a Hypersonic Technology Demonstrator (HSTD) to carry a range of weapons faster and farther.
Both have set a 2010 deadline. And both are in the pre-fabrication stage. But
ISRO has the edge as it has already carried out a seven-second experimental combustion of a test engine. To state that both the projects are progressing at somewhat the same pace won’t be far off the mark.
But there’s a remarkable design difference between the RLV and the HSTD. ISRO’s hypersonic plane, being built at the Vikram Sarabhai Space Centre (VSSC), Thiruvananthapuram, is a winged body while the HSTD is a sleeker structure. The only common architecture, perhaps, is the air intake scoop at the front through which atmospheric air will be sucked in before oxygen is separated from it to oxidise the onboard fuel.
This is how the scramjet bypasses the need to carry an oxidiser on board. In a conventional rocket, the fuel and oxidiser are stored separately and burnt in a regulated combustion of eight grams of oxygen to one gram of fuel. But in the scramjet, oxygen is isolated from the air, compressed and introduced to a stream of fuel.
To ensure that sufficient oxygen is ingested for a self-sustaining flight, the scramjet must get to supersonic speeds before going ahead with its designated mission of launching a satellite for ISRO or delivering a warhead for DRDO.
This speed is achieved by coupling the scramjet to a conventional rocket during the initial phase of the flight. "We will mount the RLV prototype on a sounding rocket (S9). The rocket will speed it up to Mach 5 before the body is allowed to surf and suck air for onboard combustion. This process fires the scramjet and propels the payload to the desired orbit at speeds between Mach 8 and 10," says VSSC director K Radhakrishnan.
The DRDO plans to use a core-alone Agni stage (S1). The capsule containing the HSTD will ride on Agni to stratospheric heights. After the first stage separates, the capsule shifts to a horizontal alignment and opens up to allow the HSTD to skim the atmosphere and breathe air.
“We’re in an advanced stage. The shock tunnel test will soon be conducted.
Our plan is to have a 400-second flight by 2009,’’ says M S Sundareshan, technical adviser at the Defence Research and Development Laboratory, Hyderabad. The DRDL is currently firing its test engine in a ground facility.
“The initial results are promising. We achieved significant thrust value,” says Sundareshan, adding that achieving hypersonic levels is a challenge that no nation except the US has met. The DRDO needs such speeds for weapon delivery at very great distances. The job is now done by Inter Continental Ballistic Missiles.
But like space rockets, ICBMs are a very costly chemical proposition. “The hyperplane can fly in at fast speeds, fire the missile or launch the warhead and return. The reusability will reduce our costs significantly,” says DRDL director Dr Venugopalan.
Cost figures in ISRO’s calculus as well. “The cost of launching a satellite using conventional rockets like the PSLV or GSLV is $25,000 to $28,000 per kg. The scramjet can reduce it to $500. This will make any nation with such a technology a launch destination,” says Radhakrishnan.
One great attraction is that the RLV can be brought back and reused. “The conventional rocket is expendable. Each stage burns out as the payload soars. But the RLV will come back after its mission,” he says.
ISRO will land the RLV on the sea using parachutes. But a project to facilitate its landing like an unmanned aircraft is on the anvil. DRDO also plans to land it like an aircraft. “We’ve a few UAV projects going where this technology is being experimented with. It can be integrated with the HSTD,” sources say.
Another frontier that scramjet research has opened up is advanced metallurgy. “We’re talking about a craft that moves at great speeds, breaks off from the atmosphere and re-enters, weathering high temperatures and atmospheric friction. There are several new alloys being developed. Apart from their use in scramjet vehicles, this research will impact the whole gamut of strategic metallurgy,” says Dr G Malakondaiah, director of the Defence Metallurgical Research Laboratory, Hyderabad.
India is experimenting with silica-carbon-silica and nickel-based alloys to cover the scramjet. Both alloys have high thermal resistance. A prototype using these alloys will be subjected to wind tunnel tests to gauge their strength against the vagaries of the atmosphere and beyond.
It is but natural for anyone to wonder why two Indian agencies are developing the same technology in parallel, with so much, except the sophisticated nature of the end-use, in common. ISRO insiders blame it on the absence of a pro-active culture within DRDO’s portals; the latter finds fault with ISRO’s big brother attitude.
“It’s the typical Indian defence story,” says one former top gun of ISRO. “In a way, it’s a blessing in disguise. Whoever proves it first will attract global attention. With the country inching closer to the concept of aerospace strategic forces, there will be a lot of give and take once the technology is proved indigenously,” he adds.
And the scramjet will place India in a league of nations that includes the US, Japan, China, Russia, Australia and Europe where this nascent technology is the latest scientific fad.
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