The Indian Space Research Organisation (ISRO) is gearing for five launches a year from its Sriharikota spaceport, ISRO chairman G Madhavan Nair announced immediately after the successful GSLV-F04 launch on 2 September. There will be another GSLV launch next year, he said.

There would also be two more launches of the Polar Satellite Launch Vehicle (PSLV) this year, he said, but the details of what satellite they would put in orbit were yet to be worked out.

Asked about ISRO''s plans to enter the international satellite-launch market, Nair told reporters that ISRO was looking at capturing a modest five to 10 per cent of the mid-range satellite segment of 2,000 kg plus in the next five years.

KR Sridhara Murthi, executive director of the Antrix Corporation, said he had received a number of inquiries for launching satellites, particularly by the under-development GSLV-Mark III, which is being designed to put into orbit satellites weighing more than 3.5 tonnes. Antrix Corporation is the marketing agency of the Department of Space.

A lighter, greener GSLV
To gain a competitive edge in the global satellite launch market, the Indian Space Research Organisation (ISRO) is taking steps to cut rocket costs, by cutting the vehicle weight and increasing its fuel economy.

The Indian space agency flies two rockets, the PSLV and the three-stage GSLV. The former places satellites in the polar orbit and the latter in the geo-synchronous transfer orbit. While a fully loaded PSLV costs around Rs 80 crore ($19.7 million), it costs nearly double the amount to build a GSLV.

ISRO''s objective is to reduce the vehicle''s structural weight, bring in modular assembly of components, use new engines and increase the fuel economy. Like automobile manufacturers, ISRO has started to source complete sub-assemblies from suppliers instead of individual components, so that the cost and time required to build its rockets is reduced. It will take ISRO a number of years to come up with a reusable launch vehicle, so cutting costs is importance right now.

Built on the same platform, PSLV and GSLV have several common components as well as the fuel, except the cryogenic stage in GSLV. The increase in the number of launches has helped ISRO to keep the rocket costs down.

To reduce the rocket''s structural weight and cost, ISRO is switching over to non-metallic components and indigenous materials like aluminium and titanium alloys. Indigenously designed avionics that will be put into operation next year weigh 185 kg, lighter than the present navigation systems.

The space agency is also trying to reduce the fuel stages to reduce the rocket weight. The GSLV Mark III model to carry a four tonne payload will have a reduced fuel stage.

ISRO is developing a strap-on motor called PSOM-XL measuring 13.5 metres with a capacity to carry 12.4 tonnes of solid propellant. Presently the six strap-on motors hugging the PSLV''s core rocket each carry 9 tonnes of fuel.

ISRO''s future plans include a three stage PSLV to ferry 500 kg satellites for low earth orbit, a new 229-tonne ''core alone'' configuration that can carry 1,100 kg satellites into sun synchronous orbit (SSO), and a vehicle to carry 1,900 kg satellites into SSO by increasing the fuel in the stage two and improving the thrust power.

ISRO''s ''core alone'' PSLV, without strap-on motors, has already started flying. In April it carried Agile, a 352 kg Italian satellite. Shortly an Israeli satellite, Polaris, will be sent up in a core alone PSLV.

ISRO is also developing air-breathing ramjet engines that would use atmospheric oxygen and burn it with on-board fuel. At present, all rockets worldwide carry liquid oxygen to burn their fuels in the relative vacuum of the upper atmosphere and space.

As much as 45 to 50 per cent of the cost of the rocket is fuel, which is why ISRO is testing cheaper alternatives. The present fuel costs around Rs2,500 ($61.50) per tonne. The space agency is also considering semi-cryogenic fuel — using highly purified kerosene and liquid oxygen as oxidiser — costing Rs20 per kg.

The effort to build an indigenous cryogenic stage is also progressing well. In August, the cryogenic stage was test fired on the ground for eight minutes at ISRO''s liquid propulsion test facility at Mahendragiri, Tamil Nadu.