ISRO plans to bring down rocket costs

ISRO is entering the satellite commercial launch market globally with major cost-lowering initiatives. Venkatachari Jagannathan reports.

With Indian Space Research Organisation (ISRO) entering the global commercial launch market in a major way and also lining up several space missions for the nation's use, the space agency is now taking steps to cut down the cost of launch vehicles.

PSLV in 2nd launch pad

The cost cutting measures include reducing the number of fuel stages in a vehicle; use of new engine-air breathing engine; using cheaper fuel and modular assembling. As ISRO is far away from making reusable launch vehicles, cutting costs in its existing programme has become imperative.

Currently ISRO has two launch vehicles, the four-stage Polar Satellite Launch Vehicle (PSLV) for placing satellites in polar orbit and the three-stage Geosynchronous Satellite Launch Vehicle (GSLV) to place satellites in the geosynchronous transfer orbit (GTO). The latter vehicle is heavier, powerful, has a higher payload capacity and costs around Rs160 crore, nearly double that of PSLV.

According to ISRO officials both the vehicles are built on the same platform. They have several common components and the fuel used to fire them is also the same-barring the cryogenic stage in GSLV. This has helped in containing the costs to some extent.

However, ISRO officials are not happy with the vendors as their prices have not come down significantly though the order volumes have gone up. This year ISRO is planning to launch 4 or 5 rockets. And for the first time in its history, ISRO is building a PSLV purely to carry a third-party satellite. In March ISRO will be launching the 350kg Italian satellite Agile. This will be followed by the launch of an Israeli satellite.

With the global launch industry being very competitive, ISRO has been forced to look at the cost reduction avenues to remain in the race. Already ISRO has started using indigenous materials like aluminum and titanium alloys to reign in the costs.

According to R V Perumal, director, Liquid Propulsion Systems, the space agency is looking at reducing the number of fuel stages to reduce the rocket cost. "GSLV's Mark III will have reduced fuel stage thereby cutting the sizeable cost." The launch vehicle is being designed to carry a four tonne payload and is expected to cost half of what GSLV costs now.

While the six solid propellant strap-on motors in the present PSLV carry 9 tonne of propellant, the new version, 13.5-metre PSOM-XL, has the capacity to carry 12.4 tonne. PSOM-XL will further improve the capability of PSLV and will be employed in future PSLV flights including the launch of Chandrayaan-1 and the microwave remote sensing satellite, RISAT.

A three-stage PSLV for carrying 500kg payload in low earth orbit is being looked by ISRO. The other developments related to PSLV are: a new 229-tonne core alone configuration with a capability to launch 1,100 kg satellite into 622km SSO and a vehicle that could carry 1,900kg in SSO by increasing the propellant in the stage two and improvement in specific impulse.

Incidentally the PSLV that will be launching the Italian satellite will not have any strap on motors-core alone configuration- as the payload is much lower.

Rockets to fly on kerosene
ISRO is testing cheaper fuel for its rockets to bring down the launch costs. According to Dr. B N Suresh, director, Vikram Sarabhai Space Centre, the different engine stages and propellant account for the major share of rocket costs. "Nearly 45 - 50 per cent of the vehicle cost is on fuel. Further avionics, software are the other cost factors."

Currently the fuel costs around Rs2,000 per kg. And the rockets burn several tonnes to place the satellites in orbit. The vehicles use solid and liquid propellants and in the case of GSLV, there is also a cryogenic stage.

According Perumal the space agency is looking at semi-cryogenic fuel whose cost will be around Rs20 per kg. The semi-cryogenic engine will use liquid oxygen as oxidiser and kerosene. "The latter will be highly purified one and not what is used to burn stoves," says Perumal.

Meanwhile ISRO's efforts to develop the cryogenic stage have entered the final stages. Though the full flight duration test (720 seconds)- burning the stage on ground- got postponed recently, the same will happen soon.

Unlike automobiles where fuel economy is measured in terms of km-per-litre, in rockets the fuel efficiency is measured by the specific impulse or the thrust power that the engine develops. "In the case of solid fuel the specific impulse is 295 and in the case of cryogenic fuel it will be more than 400."

ISRO is also in the process of developing air-breathing engines. Air breathing rocket systems are the ones which use the atmospheric oxygen from their surroundings and burn it with the stored on- board fuel for producing the forward thrust in contrast to the conventional chemical rocket systems, which carry both the oxygen and fuel on-board.

As a result, the air breathing systems become much lighter and more efficient leading to reduced overall costs. As the air breathing systems have the capability to operate only during the atmospheric phase of flight, they always have to be adopted along with the conventional chemical rockets, for meeting the final orbital velocity requirements.

The other cost reduction strategy is to go in for modular assembling of vehicles. Presently ISRO sources the components and assembles them. What is being planned is to source assembled components from the vendors so that ISRO makes the launch vehicles faster.

ISRO is also improving the avionics by upgrading the processor. It has built its own processor called Vikram. Presently ISRO uses Motorola's processor. "Again more than the cost savings, chip designing is of strategic interest," says Dr. Suresh.

Though there are two launch pads at Sriharikota, there is only one launch control centre. In order to reduce the cycle time further, ISRO is constructing another launch control centre.