Gaganyaan mission : The Crew Escape System

Credits : ISRO TV-D1 test brochure^[3]

In our previous post, “Propelling Dreams: Enhancing the LVM3 Rocket for India’s Gaganyaan Mission,” we delved into the launch vehicle that will propel Indian astronauts into space. In this article, we will focus on one of the critical components ensuring their safety and mission success: the Crew Escape System (CES). This system has undergone rigorous testing to guarantee the utmost reliability and functionality.

The Crew Escape System is a vital safety mechanism designed to protect astronauts in the event of an emergency either on the launch pad or during the ascent phase. This system is powered by a set of quick-acting, high burn rate solid motors that swiftly carry the crew module to a safe distance.

Key Tests Conducted on the CES

1. Successful Pad Abort Test (PAT)^[1]

On 5^th July 2018, the Indian Space Research Organization (ISRO) conducted a successful Pad Abort Test, a crucial trial run for the Gaganyaan mission’s launch abort system. This system, akin to an ejection seat for a fighter pilot, is designed to rapidly propel the entire crew module away from the launch vehicle in the event of a potential failure. During the test, the crew module was accelerated to 10 g and reached a peak altitude of 2.75 km (1.71 mi) before safely parachuting down into the Bay of Bengal, 2.9 km (1.80 mi) from its launch site.

The module was propelled skyward by seven solid-fueled rocket motors, ensuring the g-force limits were within safe boundaries. The total duration of the test was 259 seconds, with the ascent phase lasting 20 seconds and the descent phase, not including splashdown, extending for 200 seconds. The module’s chute detachment occurred precisely at 259.4 seconds post-launch, as planned. The entire launch process was meticulously recorded by approximately 300 sensors, providing valuable data for future missions. Recovery boats were promptly dispatched to retrieve the crew module, marking the successful completion of this critical safety test.

2. In-flight Abort Demonstration of CES ^[2]

On 21^st October 2023, ISRO successfully completed the first development flight Test Vehicle (TV-D1). The Test Vehicle, a single-stage liquid rocket, had been developed specifically for this abort mission. The payloads included the Crew Module (CM) and Crew Escape Systems (CES) equipped with fast-acting solid motors, along with the CM fairing (CMF) and Interface Adapters. This flight simulated an abort condition during the ascent trajectory at a Mach number of 1.2, as encountered in the Gaganyaan mission.

During the mission, the CES with the CM separated from the Test Vehicle at an altitude of approximately 17 km. The abort sequence was then executed autonomously, beginning with the separation of the CES and the deployment of the drogue parachute at 16.7km. This sequence concluded with the safe touchdown of the CM in the sea, about 10 km from the coast of Sriharikota.

3. Major vehicle sub-system tests^[3]

• AR 6 VIKAS Engine hot tests
• Actuator-in-Loop Simulation test
• Integrated structural test of Interface Adapters
• Aero-elastic test
• Cold Gimbal test
• Integrated Base Shroud Acoustic test
• CES Ground Resonance test
• Equipment Bay vibration test

Credits : ISRO TV-D1 test brochure^[3]

4.Qualification of solid motors^[3]

The Crew Escape System (CES) consists of five types of quick-acting solid motors that had under gone qualification prior to the TV-D1 test demonstration:

• Crew Escape System Jettisoning Motor (CJM)
• High-altitude Escape Motor (HEM)
• Low-altitude Escape Motor (LEM)
• Low-altitude Pitch Motor (LPM)
• High-altitude Pitch Motor (HPM)

These motors, utilizing PEDCEM formulation, are designed to generate the necessary acceleration to meet varying mission requirements.

5. Parachute Deployment Tests^[4]

The Vikram Sarabhai Space Centre (VSSC)/ISRO successfully conducted a series of Drogue Parachute Deployment Tests at the Rail Track Rocket Sled (RTRS) facility of the Terminal Ballistics Research Laboratory, Chandigarh, from August 8 to 10, 2023, in collaboration with the Aerial Delivery Research and Development Establishment (ADRDE)/DRDO.

Central to the Gaganyaan mission’s objective of safely transporting astronauts to and from space is the reliable deployment of drogue parachutes. These parachutes are critical for stabilizing the crew module and decelerating its velocity during re-entry. Each drogue parachute, equipped with pyro-based mortars, is designed to swiftly eject and deploy conical ribbon-type parachutes measuring 5.8 meters in diameter. A single-stage reefing mechanism within these parachutes minimizes canopy area initially, reducing opening shock and ensuring a controlled descent for the crew module.

The tests conducted at the RTRS facility simulated real-world scenarios to assess the performance and reliability of the drogue parachutes comprehensively. The first test introduced reefing in a mortar-deployed parachute in India, evaluating maximum reefed loads. The second test scrutinized maximum disreefed loads, while the third replicated conditions akin to the maximum angle of attack experienced by the Crew Module during its mission.

These successful tests at the RTRS facility represent a crucial milestone in qualifying the drogue parachutes for integration into the upcoming Test Vehicle-D1 mission. Earlier in 2023, similar tests were conducted for the Pilot and Apex cover separation parachutes, further advancing the development of the Gaganyaan mission’s parachute system.

The parachute sequence for the Gaganyaan crew module’s deceleration system involves a total of 10 parachutes. This sequence initiates with two Apex cover separation parachutes followed by the deployment of two drogue parachutes for stabilization. Subsequently, three Pilot chutes individually extract the three main parachutes, essential for reducing the Crew Module’s speed to ensure a safe landing.

Credits : ISRO TV-D1 test brochure^[3]

Conclusion

In conclusion, the rigorous testing regime conducted on the intricate Crew Escape system and its subsystems under ISRO’s Gaganyaan project represents pivotal milestones in India’s space exploration journey. These tests ensure the safety and reliability crucial for manned space missions, reflecting ISRO’s commitment to precision engineering and astronaut safety. Looking ahead, our next blog post will explore the Orbital Module systems, delving into the comprehensive series of tests they have undergone thus far. Stay tuned as we continue unraveling the complexities of India’s ambitious foray into human spaceflight.