ISRO: Indigenously designed and developed supersonic decelerator test successful

The Indian Space Research Organization (ISRO) recently announced the successful test of a supersonic 'Inflatable Aerodynamic Decelerator' (IAD). The IAD was indigenously designed by ISRO's lead facility, the Vikram Sarabhai Space Centre(VSSC), and was realised by the Indian industry. WION spoke to Dr S. Unnikrishnan Nair, Director, VSSC, regarding the significance of this test; what went into the making, and the potential this technology holds.

Traditionally, rocket scientists think of ways and means to have their rockets travel faster and do so more efficiently. However, when it comes to performing interplanetary missions and recovering spent rocket stages(re-usability), it is crucial to slow down a rocket/spacecraft. The rocket stages that are re-entering earth's atmosphere travel at supersonic speeds and spacecraft entering other planets travel at hypersonic speeds.

The commonly used technology to slow down a descending spacecraft/rocket is the firing of a retro-rocket. Simply put, when a rocket is on the ground its engines are fired to lift it off and it functions like a typical rocket. In the case of re-entry, the rocket is travelling at high speeds owing to the energy added by its propulsion system and gravitational pull on its mass.

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So, the same engines used for lift-off are fired again to slow it down to a suitable speed for landing. The IAD aims to do something similar without firing rocket engines. It just uses friction or aerodynamic drag.

"IAD is an inflatable structure made of kevlar fabric, coated with Polychloroprene. As the IAD is made of fabric, it can be packed into a small volume of 15litres and can be packed into the nosecone of RH300 rocket (which was used for the test). Once the test rocket reaches an altitude of about 84kilometre, the IAD is deployed and begins to slow down the rocket body(the component known as the payload part) as it undergoes atmospheric re-entry and finally splashes down in the sea" explained Dr Nair.

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He added that the inflation of the IAD was carried out by compressed nitrogen gas stored in a gas bottle. Once the IAD falls into the sea, it is deflated by firing a pyro valve to prevent it from floating and thereby causing any harm to sea vehicles.

Notably, this is the first time that an IAD is designed specifically for spent stage recovery. The IAD has huge potential in a variety of space applications like recovery of spent stages of the rocket, landing payloads on Mars or Venus, and making space habitats for human space flight missions.

"This demonstration opens a gateway for cost effective spent stage recovery using the IAD technology. This technology can also be used in ISRO's future missions to Venus and Mars" said Dr S Somanath, Chairman ISRO, and Secretary DOS, who witnessed the successful launch.

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Queried about the scalability of the IAD and the possibility of guided landings, Dr Nair said that it can be scaled up to recover even a spent rocket stage.

"It can be used to systematically decelerate a re-entering vehicle by gradually inflating the decelerator. As such, the IAD is not guided. For sea landing precise guidance is not a must. By suitably sizing the IAD, the need for a retro rocket can be avoided for spent stages of vehicle first stage, where energy of spent stage is comparatively less." said Dr Nair before adding that we are yet to do a scaled-up design.

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