PSLV
Configuration, Stages, and the Space Debris Problem
India's Polar Satellite Launch Vehicle (PSLV) is ISRO's most reliable workhorse rocket, having completed over 60 missions. It is a four-stage rocket that alternates between solid and liquid propulsion:
- PS1 (First Stage): Solid propulsion using 139 tonnes of HTPB fuel; augmented by 6 strap-on boosters in the PSLV-XL variant.
- PS2 (Second Stage): Liquid propulsion using Vikas engine (UDMH fuel + N₂O₄ oxidiser).
- PS3 (Third Stage): Solid propulsion (7.6 tonnes HTPB).
- PS4 (Fourth Stage): Two liquid engines; this stage remains in orbit as the satellite is deployed.
The first three spent stages fall back into the ocean after burnout, while the PS4 (fourth stage) typically remains in low Earth orbit (LEO) as debris. The heat shield — a protective fairing covering the payload during atmospheric ascent — is jettisoned during the flight and also falls back. Given that ISRO has launched over 60 PSLV missions, some spent stages have re-entered atmosphere unpredictably and reached land or coastlines instead of the ocean.
- PSLV first flew in 1993; has since become ISRO's most reliable launch vehicle.
- PS4 (fourth stage) is a known source of orbital debris — it enters LEO after payload deployment and can remain in orbit for years before reentry.
- In 2023, debris identified as a PSLV rocket body washed up on an Australian beach, raising the first formal international liability question for ISRO.
- The PSLV-C61 mission in 2024 was a notable failure involving the PS3 stage — further complicating debris tracking for that mission.
- ISRO's VSSC (Vikram Sarabhai Space Centre) in Thiruvananthapuram handles launch vehicle development and is the natural first responder for debris identification.
● Tracked since March 20, 2026 · last seen September 07, 2026 · updates as the daily brief publishes