The
Rockets

SLV-3 was a decade-long indigenous effort led by A.P.J. Abdul Kalam as Project Director. With no foreign technology transfers permitted, ISRO built every component from scratch. The 1979 launch failed due to fourth-stage destabilisation, but the July 1980 launch was a complete success — Rohini RS-1 into a 305×919 km orbit. India became the sixth nation to develop its own satellite launch capability.

SLV-3's real legacy was the engineers it forged. Every team that built PSLV, GSLV, and LVM3 cut their teeth on SLV-3.

* UH25 = a blend of UDMH and Hydrazine Hydrate used in the Vikas engine — derived from the French Viking engine, indigenised by ISRO, with a perfect flight record across PSLV, GSLV, and LVM3.

PSLV's four-stage alternating solid-liquid design is its signature strength — solids for high thrust in the lower atmosphere, liquids for precise throttling at orbital insertion. The XL configuration adds six strap-on boosters for extra payload.

PSLV has launched Chandrayaan-1, Mangalyaan, Astrosat, Aditya-L1, and 104 satellites in a single flight. Its PS4 fourth stage, retained in orbit as POEM platforms, has hosted dozens of experiments — zero-waste space engineering.

GSLV Mk II introduced India's indigenous cryogenic stage — the CE-7.5 engine burning liquid hydrogen (−253°C) and liquid oxygen (−183°C). The United States pressured Russia in 1992 to block cryogenic technology transfer to India. ISRO's response was to develop the engine independently — a process spanning nearly two decades. GSLV Mk II now routinely launches GSAT communication satellites, NVS navigation satellites, and GISAT Earth observation missions.

LVM3's most significant achievement is its cryogenic upper stage — the C25, using liquid hydrogen (−253°C) and liquid oxygen (−183°C). Mastering this placed India in an elite group: only USA, Russia, France, Japan, China, and India operate indigenous cryogenic stages. The CE-20 engine was developed entirely by ISRO after technology transfer was denied in the 1990s.

LVM3 will be upgraded to HLVM3 for Gaganyaan — with additional abort systems, crew escape tower, and human-certification modifications. The same rocket that launched Chandrayaan-3 will carry India's first astronauts.

SSLV's solid stages cannot be throttled once ignited — so the Velocity Trimming Module (VTM), a small liquid stage using MMH/MON-3, provides precise orbital fine-tuning after the solids finish. It's the difference between "approximately right" and "exactly right."

SSLV can be assembled in 72 hours with minimal ground infrastructure — designed specifically for the commercial small satellite market. After a sensor failure on SSLV-D1 (2022), SSLV-D2 (2023) succeeded perfectly and the vehicle is now available commercially via NewSpace India Limited (NSIL).