On to reusable launch vehicles

IN about four years, the technology demonstrator of ISRO's reusable launch vehicle (RLV) will blast off from Sriharikota and return to land in an Indian Air Force base. The operational RLV will become a reality in about 20 years. Its booster (rocket) will splash down in the sea and can be recovered, while the orbiter will put the satellite in orbit and return to a regular landing.

Next year ISRO will launch a satellite that will be a platform for doing experiments such as growing crystals and developing pharmaceutical products in a microgravity environment. This 450-kg satellite, called capsule or module, will remain in space for three months before splashing down in the sea. The payloads of what is called the Space Recovery Experiment (SRE) will be retrieved and studied. "This space recovery capsule is the first preliminary step towards building our futuristic space recoverable system," Dr. K. Kasturirangan, Chairman, ISRO, told Frontline.

"Low cost in access to space", the hot theme in the space industry today, is driving ISRO to build RLVs. A cost-effective space transportation system entails building new technologies required to recover the booster for re-use. "The central issue is how to recover it from orbit," said Dr. Kasturirangan. "We plan to fly the space recovery capsule in a year or so. It will be put in orbit by the PSLV." After the experiments are done, the capsule will be de-orbited by retro-propulsion. Mastering the re-entry technology is the challenge.

Said Dr. Kasturirangan: "You have to do thermal management, materials management, propulsion management, orbital management and recovery management. It is a very interesting set of technologies that have to be developed as part of the space recovery capsule."

The project will take 20 years, according to G. Madhavan Nair, Director of the Vikram Sarabhai Space Centre in Thiruvananthapuram. "We are just starting the paper-designs now. We hope to have the technology demonstrator in three to four years. But the technology demonstrator will not go into orbit," he said.

According to Madhvan Nair, there is a lot of difference between the space shuttle and the RLV. In the RLV, both the booster and the upper stage will be recovered. The booster will go up to an altitude of about 100 km and fly back to one of the Air Force bases. The upper stage will be like a spacecraft recovery experiment. It will break the orbit, re-enter the atmosphere, and come down on a parachute.

R.V. Perumal, Associate Director, VSSC, called the experiment to recover space modules an important "intermediate project" towards building the RLV. "For the first time, we are trying to recover a module which is put into orbit as part of our regular launches. This module will be programmed to re-enter and splash down at a particular point in the sea, from where we can recover it. In building this module, we have to devise a thermal protection system to enable the module to withstand the re-entry heat. We will also learn about other mission requirements such as control and guidance schemes for the re-entry," he added.

Perumal called the SRE and the RLV a "whole new ball game" because they demanded mastering many new technologies. "In a sense, we are back to our SLV-3 days... ab initio," he said. "We are in the process of completing the preliminary feasibility studies so that we can arrive at a proper definition of the technology demonstrator and what its technology requirements are," he added.

In a launch, 60 to 70 per cent of the cost is on hardware. So an RLV is economical because money is not spent on hardware every time it is sent up. Space technologists saw the RLV as something that would lead to cheaper space transportation system. "Space tourism has a big market, and if we reduce the cost of space transportation, space tourism can become an economic industry," said Perumal.