Rare photos of the 2009-2010 development sea trials of (from top) India's two principal underwater weapon development programmes -- the Torpedo-Advanced Light (TAL) and the Varunastra heavyweight high speed torpedo, developed by the Naval Science & Tech Laboratory (NSTL) in Visakhapatnam. After several stops and starts, the Varunastra is to enter its user trial phase with the Indian Navy this year, while Bharat Dynamics Ltd (BDL), India's principal state-owned missile manufacturer, will begin delivering the first of 25 TALs to the Navy shortly.
Little is known about either programme, mostly because that's the way the government has wanted it. Scant bits of literature (sometimes inadvertent) suggests that technologies involves in both or either of the torpedo programmes include sea water actuated / silver zinc propulsion packages, contra-rotating motor and propellers, proximity sensors, HE warheads, composite material construction, stepless speed control, fibre optic guidance, floating recorder and transmitter (FRAT), noise cancellation techniques and low noise FRP propellers.
[UPDATE @ 2.29AM / MAY 24] Will the DRDO never learn? It appears that some of the photos used by the DRDO in its official brochure (PDF here) to represent its underwater weapons programmes, have actually been lifted from foreign vendors' brochures. Prasun K Sengupta has pointed in the comments section of this post, to links to the original images in the case of the Varunastra and Thermal Torpedo that appear in the DRDO brochure -- the Varunastra and Thermal Torpedo captioned in the brochure are actually torpedoes manufactured by Saab. No clarity on the TAL, though. Will ask DRDO for some clarity tomorrow. DRDO's goofed plenty before with this sort of thing, so will check.