A state-of-the art complex

FROM a distance it looks like an upscale multi-storey apartment complex on the beachfront; elegant windows on different floors, tastefully painted "doors", and spectacular buttress for the walls complete the design. It is the state-of-the-art second launch pad at the Satish Dhawan Space Centre at Sriharikota, India's spaceport, in Andhra Pradesh. ISRO plans to launch its PSLV from this padin early 2004.

The centrepiece of the launch pad is its "universal" vehicle assembly building (VAB). "We configured the VAB as a universal launch pad. It has the flexibility to accommodate any type of vehicle after minor modifications and without entailing major investment," said K. Narayana, Director, Satish Dhawan Space Centre. A rocket weighing 1,000 tonnes can be assembled in it. The 76-metre-tall launch tower, made of steel and painted grey, is situated about a kilometre away from the VAB.

The vehicle is integrated inside the VAB on a launch pedestal, which is then rolled out to the tower on special tracks that can take a load of 2,000 tonnes. A 16-wheeled "bogie" with four jacks would lift the launch pedestal and tow it to the tower. In the first launch pad, the reverse happens. The vehicle is built inside a Mobile Service Tower, which moves away before lift-off.

The concept of a universal launch pad is in contrast to that in advanced countries, where pads exist for each type of vehicle. Said P. Venkateswara Rao, Associate Director of the Centre and Project Director of the second launch pad: "The concept of a universal launch pad posed a great challenge... We addressed future vehicles and built infrastructure suitable for them. When we planned the VAB, we took into account Mark III's huge strap-on boosters, each of which will use 200 tonnes of solid propellants, and its upper cryogenic stage, which will be powered by 25 tonnes of liquid hydrogen and liquid oxygen."

The VAB is 82 metres, or 27 storeys, tall; 40 metres long; and 32 metres broad. It has two overhead cranes that move on rails. One crane lifts weights (rocket stages) up to 200 tonnes and sits at a height of 72 metres. The other can handle ten tonnes.

A second launch pad became necessary because of the increase in the frequency of flights from SHAR. ISRO had even put in the orbit four foreign satellites from SHAR, on the PSLV. If SHAR had only one launch pad and there was any incident, the foreign customers would not wait for many months for the launch pad to be refurbished.

The VAB has six sets of foldable platforms to assemble the launch vehicle. After assembly, the platforms open out for the vehicle to roll to the launch tower. The platforms can move from a height of 10 metres to 76 metres. Two huge hydraulic doors, in the front and at the rear, enable two vehicles to be assembled simultaneously.

Once a fully assembled vehicle is rolled out, work on another vehicle can begin on its launch pedestal inside the VAB. A turning mechanism similar to that of a railway turntable and a simple hydraulic system allow the second launch pedestal to be parked at a distance and moved into the VAB on the bogie.

The bogie positions the pedestal and drives it with the vehicle standing on it. Said Venkateswara Rao: "We will be using the same control system and bogie for different pedestals for various vehicles. The bogie can move up and down, and can take any vehicle. Nobody has built like this in the world. It is a state-of-the-art control system. It has been commissioned."

The launch tower has flame deflectors, which are open tunnels scooped out at an angle. During lift-off, the blasts of flame are deflected into these tunnels.

ISRO gave the concept of this pad to MECON, a public sector undertaking, which translated it into design and engineering, and executed the job as a turn-key one. About 130 industries and 140 sub-contractors took part in the project. They included the Heavy Enginering Corporation, Ranchi; the Bhilai Engineering Corporation; Simplex Concrete Piles; KCP, Chennai; L&T; SPIC JEL Engineering Construction; and Gannon Dunkerley and Company.

"It took four years to build this second launch pad on a coastal zone in an isolated place," said Venkateswara Rao. "The industries and contractors did a fantastic job."