Chennai/IBNS/UNI: The countdown for the launch of the first unmanned Flight Test Vehicle Abort Mission-1 (TV-D1) to demonstrate the crew escape system of the Gaganyaan programme, commenced at 7.30 pm at SHAR Range Sriharikota on Friday evening.

It will be a 12.5-hour countdown, the ISRO said.

In an update, the ISRO said: "Mission Gaganyaan: TV-D1 Test Flight. The countdown leading to the launch at 08:00 Hrs. IST on October 21, 2023, has commenced."

The launch of the short-duration mission will take place from the first launch pad at 8 AM Saturday morning and the entire mission will last 531 secs (about nine minutes).

This flight test will mark a major milestone in the overall Gaganyaan programme--which will be India's first manned mission to space--and will define the in-flight abort demonstration of Crew Escape System (CES) at Mach Number 1.2 with the newly developed Test Vehicle followed by Crew Module Separation and Recovery.

The objective of the mission is Flight demonstration and evaluation of test vehicle sub-systems, Crew Escape System including various separation systems and Crew Module characteristics & deceleration systems demonstration at higher altitudes and its recovery.

The 35 m tall Liquid Propelled Single Stage Test Vehicle, weighing about 44 ton, uses a modified Vikas engine with 4,520 kg Crew Module (CM)-- a single-walled unpressurized aluminum structure-- and CES mounted at its fore end.

"The entire flight sequence, right from lift off to the crew module touchdown at sea about 10 km from Sriharikota, with the deployment of parachutes, will last 531 seconds," ISRO said.

It said about 60 seconds after the lift-off, the test vehicle -- crew escape system will get separated at an altitude of 11.7 km and another 30 seconds later, the CM-CES will get separated at an altitude of 16.7 km at a velocity of 148.7 m/s.

Subsequently, the abort sequence will be executed autonomously commencing with the separation of CES and deployment of series of parachutes, finally culminating in the safe touchdown of the CM in the sea, about 10 km from the coast of Sriharikota, the space agency said.

"The CM will splash down In the sea at about 10 km from Sriharikota and float until it was recovered by the Indian Navy. The recovery ships will reach the CM and a team of divers will attach a buoy, hoist it using a ship crane, and bring it to the shore," it said.