The Small Satellite Launch Vehicle (SSLV) is a small-lift launch vehicle developed by ISRO to deliver 500 kg (1,100 lb) payload to low Earth orbit (500 km (310 mi)) or 300 kg (660 lb) payload to Sun-synchronous orbit (500 km (310 mi)). The rocket supports multi-orbital drop-offs capability for small satellites. The maiden flight SSLV-D1 was conducted from First Launch Pad on 7 August 2022, however, the payload failed to reach the intended orbit. The second flight SSLV-D2 was successful in delivering payload into orbit on 10 February 2023. SSLV is made keeping low cost, low turnaround time in mind with launch-on-demand flexibility under minimal infrastructure requirements. It is capable of carrying multiple satellites. Once SSLV is operational, NewSpace India Limited (NSIL) and a group of Indian companies will manage the mass production and launch activities.
History
Development In 2015, a National Institute of Advanced Studies report by Rajaram Nagappa proposed development path of a 'Small Satellite launch Vehicle-1' to launch strategic payloads. In National Space Science Symposium 2016, then Director of Liquid Propulsion Systems Centre, S. Somanath also acknowledged a need for identifying a cost effective launch vehicle configuration with 500 kg payload capacity to LEO and by November 2017, development of such launch vehicle was underway. By December 2018, the Vikram Sarabhai Space Centre (VSSC) completed the design for the vehicle. The aerodynamic characterization research was conducted at the National Aerospace Laboratories' 1.2m Trisonic Wind Tunnel Facility. In December 2020, all booster segments for SSLV first stage (SS1) static test (ST01) were received and assembly was done in Second Vehicle Assembly Building (SVAB). The first static fire test (ST01) of the SS1 first-stage booster conducted on 18 March 2021 was unsuccessful. About 60 seconds into the test, oscillations were observed and after 95 seconds, the nozzle of SS1 stage disintegrated. The nominal duration of test was 110 seconds. To qualify for flight, SSLV's solid first stage SS1 has to perform two consecutive nominal static fire tests. The SSLV Payload Fairing (SPLF) functional qualification test was completed in August 2021. The second static fire test of SSLV first stage SS1 was conducted on 14 March 2022 at SDSC-SHAR and met the required test objectives.
Further Development ISRO carried out a successful static test of an improved version of the third stage of the SSLV on 30 December 2025, at the Solid Motor Static Test Facility of SDSC. It validated an improved version of the SS3 stage with a Carbon-epoxy Motor case built by VSSC, which has significantly reduced the mass of the stage, thereby improving the payload performance of SSLV by 90 kg. The stage also features an improved design for the igniter and nozzle system. It will be deployed on the next flight mission of the SSLV onwards. ISRO carried out a similar static test for improvements in the vehicles first stage on 11 August 2026 at the Solid Motor Static Test Facility of SDSC.The design improvements that were tested include more optimized thermal protection system and process improvements in the nozzle sub-system to make it more production friendly along with a reduction in the mass. This led to an enhanced propellant burn rate in two motor segments, boosting payload capacity further by another 100kg.
Operational history
SSLV-D1
The first developmental flight of the SSLV occurred on 7 August 2022. The flight mission was named SSLV-D1. The SSLV-D1 flight failed to achieve its mission objectives. The rocket had a three-stage configuration with a fourth Velocity Trimming Module (VTM). In its D1 configuration, the rocket was 34m tall with a diameter of 2m and a lift-off mass of 120t. The rocket carried EOS 02, an Earth observation satellite that weighed 135 kg and AzaadiSAT, a CubeSat payload that weighed 8 kg, developed by Indian students to promote inclusivity in STEM education. The SSLV-D1 was supposed to place the two satellite payloads in a circular orbit of altitude 356.2 km with 37.2° inclination. The official explanation by the ISRO for the mission failure was software malfunction. According to the ISRO, the mission software detected an accelerometer anomaly during the second stage separation. This caused the rocket navigation to switch from a closed loop guidance to an open loop guidance. Even though, this switch in guidance mode was part of the redundancy built into the rocket's navigation, it could not salvage the mission. During the open loop guidance mode, the final VTM stage only managed to fire for 0.1s instead of the intended 20s. This led to the two satellites as well as the VTM stage of the rocket being injected into an unstable elliptical transatmospheric orbit of 360.56×75.66 km with an inclination of 36.56°. The SSLV-D1's final VTM stage had 16 hydrazine (MMH+MON3) fueled thrusters. Eight of those were to provide altitude control and the remaining eight for controlling the orbital velocity. The VTM stage also provided pitch, yaw and roll control during the orbital insertion maneuvers. The three main stages of the SSLV-D1 functioned normally. But, that was not enough to impart adequate impulse for the two satellite payloads to achieve stable orbits. For the injection of the two satellite payloads into their intended stable orbits, the VTM stage had to fire for at least 20 seconds, to impart enough additional orbital velocity and altitude corrections. Instead the VTM kicked-in at 653.5s and shut itself down at 653.6s, post lift-off. Following the partial firing of the VTM stage, the EOS 02 was released at 738.5s and AazadiSAT at 788.4s, post-liftoff. These failures transpired, resulting in the satellites entering an unstable orbit and subsequently destroyed upon reentry.
SSLV-D2
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