This week in rocket history is the SRE-1 capsule launch by ISRO.

In the first decade of this century, India’s space agency, ISRO, began its own human spaceflight program. This would not be the first time an Indian citizen went into space, as Rakesh Sharma had gone up for seven days in 1984 on the Soyuz T-11 mission to Salyut 7. In addition, several NASA astronauts were either born in India and moved to the U.S. or were born in the U.S. to Indian parents. 

The first hardware demonstration of technology necessary for sending humans to space was the SRE, or Space capsule Recovery Experiment. The purpose of the SRE was to demonstrate the future capsule’s thermal protection system (TPS), guidance during reentry, and recovery operations. All of these operations are critical to recovering crewed capsules from space. The TPS was designed to be reusable with both silica tiles and phenolic ablators. While in space, the capsule would conduct experiments in microgravity.

By 2007, the SRE was ready. The 555-kilogram capsule was 1.6 meters tall and two meters wide, in the shape of a cone, like many reentry bodies. The flat end had solar panels and maneuvering rockets; it reentered pointy end first. It was launched into orbit on January 10, 2007, atop the PSLV C7 mission, the tenth overall flight of the PSLV rocket. It was launched in a dual launch configuration with Cartosat-2 and two other CubeSats riding above the SRE into a 625-kilometer sun-synchronous orbit. This was the first dual launch configuration of the PSLV, one it has used many times in the years since.

The two experiments on SRE-1 included a Biomimetic Material Processing Reactor. As the name sounds, biomimetics is the manufacture of materials similar to how they are made biologically. Specifically, the SRE-1 experiment synthesized self-assembling hydroxyapatite, a mineral very close to what makes up the human bone. This mineral is very useful for tissue engineering. 

The other experiment was the Isothermal Heating Furnace which grew a  gallium-magnesium-zinc quasicrystal in microgravity. Crystals grown in microgravity are often larger and more well-ordered than Earth-grown crystals. 

The capsule did all of this running on about the same power as a Playstation 4, provided by fixed solar panels on the bottom of the capsule.

For twelve days the SRE orbited the Earth before reorienting and performing a ten-minute deorbit burn.  It re-entered the Earth’s atmosphere successfully at 03:37 UTC on Jan 22, 2007, at a velocity of 8 km/s. Aerodynamic braking with the heat shield reduced that to just over 100 m/s, and deployment of the drogue chute reduced this further to 47 m/s. The main chutes brought it down to 12 m/s for a safe splashdown in the Bay of Bengal at 03:46 UTC. Another part of the SRE demonstration was a flotation system on the capsule, which was successfully deployed, righting the capsule. It was recovered by the Indian Navy and Coast Guard supported by aircraft.

With the SRE-1, India joined the exclusive group of nations that have both launched and recovered something from orbit. A follow-on mission was planned for 2009 to start a series of low-cost recoverable capsules for microgravity research; however, after a long series of delays, it was finally canceled in 2018 but not until after a lot of hardware had been constructed.

More Information

Space Capsule Successfully Recovered (ISRO)

PDF: Space Capsule Recovery Experiment slide presentation (APRSAF via Internet Archive)

PDF: Report no. 306 (Parliament of India)

Soyuz T-11 info page (Space Facts)