LVM3

ISRO gives the overall length as 43.5 metres, a four metre core diameter and a five metre fairing, with 640 tonnes on the pad. The payload figure used here is ISRO's own conservative one, 8,000 kilograms to a 600 kilometre low orbit, because it is the only LEO number the agency publishes with a reference orbit attached to it.

That qualification matters more than usual here, because ISRO does not agree with itself. Its own properties carry a ten tonne class low orbit claim with no orbit stated, and four separate transfer orbit figures ranging from 4,000 kilograms up to about 5,000. When the operator publishes four numbers, quoting one of them without saying which page it came from is not precision, it is a coin toss.

The staging is worth looking at. Two S200 solid boosters, roughly 5,150 kilonewtons each for about 10,300 kilonewtons at liftoff, do all the work off the pad, and the L110 liquid core does not light until around 108 seconds into the flight. The rocket leaves the ground on solids alone, which is cheap and simple and gives up any chance to check the liquid engines before committing to the ascent.

Nine launches and nine successes, over eleven years and nine months. That works out at about three quarters of a flight per year, with gaps of thirty and thirty-nine months in the record, and it is the real constraint on the programme rather than any engineering limit. Vehicles are built one at a time, there is one shared pad at Sriharikota, and cryogenic stage throughput is the bottleneck behind both.

The human-rated HLVM3 is where the engineering changes. Extra O-rings in the booster joints, chamber pressures deliberately reduced on both the solids and the Vikas engines, a stretched C32 cryogenic stage, quad-redundant navigation, dual-chain telemetry, an ascent capped at four g and a crew escape system. Every one of those is performance traded for margin. As of August 2026 the government was targeting the first uncrewed Gaganyaan flight for the fourth quarter of that year, with crew in 2027, and the vehicle for it had been stacked at Sriharikota since December 2024.