What is IADT-1, the Gaganyaan test ISRO conducted on August 24? | Explained

The story so far: On August 24, the Indian Space Research Organisation (ISRO) successfully carried out its first Integrated Air Drop Test (IADT-1), a crucial milestone in the preparation for the country’s maiden human spaceflight mission, Gaganyaan. A dummy crew capsule weighing nearly five tonnes was dropped from a helicopter to test whether its parachute system could slow it safely for splashdown.

What is IADT-1?

The IADT is designed to evaluate the parachute-based deceleration system that will bring the Gaganyaan crew module down safely after reentry. In IADT-1, the parachutes were expected to deploy in a precise sequence after the module was released from a height of about 3 km.

Although the capsule was uncrewed and the drop was conducted from a helicopter, the test simulated the last stages of an actual space mission. In the real scenario, the capsule will first be slowed by atmospheric drag and its heat shields, followed by smaller drogue parachutes and finally the three 25-m main parachutes. The aim was to ensure the capsule slowed to around 8 m/s before splashdown.

How and why was the test carried out?

For IADT-1, an Indian Air Force Chinook helicopter lifted a 4.8-tonne dummy crew module into the air. At the designated altitude, the helicopter released the capsule. From then on, automated systems triggered the sequential deployment of parachutes.

ISRO reported that the touchdown conditions matched expectations, demonstrating that the design worked in real-world conditions. The exercise involved extensive modelling, instrumentation, and coordination among multiple agencies. Aside from the Air Force, the Defence Research and Development Organisation (DRDO) contributed to materials and safety systems. The Indian Navy and Coast Guard prepared for post-splashdown recovery. Vikram Sarabhai Space Centre Director A. Rajarajan has said that his centre was responsible for nearly “90%” of the IADT-1 activities.

In a crewed space mission, ascent, descent, and recovery are the riskiest phases. Even after a successful launch and orbital stay, astronauts’ survival hinges on whether the capsule can decelerate safely for re-entry and landing. A failure in parachute deployment could lead to catastrophe. Testing on the ground is thus indispensable.

Where does IADT-1 lie on the roadmap?

Gaganyaan’s ultimate objective is to send Indian astronauts to low-earth orbit on a human-rated LVM3 rocket. But before that happens, ISRO must conduct a series of tests to validate safety systems. Unlike previous satellite or planetary missions, human spaceflight requires human-rating of every system. This involves engineering redundancies, fault detection, and life support.

The Crew Escape System tests are to demonstrate whether astronauts can be pulled away from the rocket in case of launch failure. The first such test vehicle flight, TV-D1, took place in October 2023. TV-D2, scheduled next, will attempt a more complex abort scenario.

The uncrewed Gaganyaan-1 (G1) mission will launch a crew module aboard the LVM3 to orbit. The module will house ‘Vyommitra’, a humanoid robot designed to mimic astronaut operations. The recent IADT-1 success will pave the way for TV-D2 and G1.

Further drop tests and subsystem trials, including more IADTs and subsystem checks, will continue in parallel, refining the systems before astronauts are cleared to fly. In all, by the time the first human flight (H1) has happened, ISRO will have conducted several thousand tests.

Some of the critical systems under development include the environmental control and life support system (ECLSS) for oxygen, temperature, waste management, and fire safety; the integrated vehicle health management system (IVHMS), capable of autonomously detecting faults and triggering abort actions; and the strengthened LVM3 rocket, modified to meet the reliability standards necessary to carry humans.

India has also had to indigenise many technologies that were unavailable from abroad, from escape motors to specialised composites. Each subsystem has to pass hundreds of tests before being certified.

What are India’s long-term goals?

Gaganyaan is not an end in itself but the foundation of a broader human spaceflight roadmap. The Indian government has announced plans to establish the Bharatiya Antariksh Station (BAS) by 2035 and to achieve an Indian crewed lunar landing by 2040. These goals will demand repeated flights, extended orbital missions, and deep-space technology.

In this regard, while schedules may slip — IADT-1 was originally planned for April 2024, e.g. — each milestone will build capability for more ambitious tests. For example, according to ISRO, the TV-D2 mission “will demonstrate Gaganyaan Crew Escape System by simulating an abort scenario. The crew module will separate and descend using thrusters and parachutes before sea splashdown, followed by recovery operations.”

In tandem, ISRO is currently operating its SpaDeX mission in its extended phase, after the mission’s twin satellites successfully demonstrated in-orbit docking in May 2025. This technology will be an important part of the Gaganyaan, Chandrayaan-4, and BAS missions.

H1 is currently scheduled for 2027 but is likely to be delayed further.