India began developing the Prithvi-I in 1983. The missile is 8.5 m long, 1.1 m in diameter. Its body is made from aluminum alloy and its wings are made from magnesium. There are four clipped-tip delta wings at mid-body and four small aerodynamic control fins at the rear.

Prithvi is a single-stage missile with a liquid-propellant engine, made by the Soviet KB Isayev (derivative of S2.711V engine). It used two motors side-by-side that provide aerodynamic control as well as thrust vectoring. The thrust (app. 2x 35 kN) enabling a variable total impulse to be programmed for different payload and range requirements. The rocket-propellant is most likely TG-02/AK-20F, according to the origin of the engine. The missile has a maximum range of 150 km.
The Prithvi-I first test flight was in 1988 and it officially entered service in 1994.

Prithvi-II (SS-250)
The Prithvi-II is similar to the Prithvi-I in many ways, However, with extended tanks for more fuel.
India first tested the Prithvi-II in 1996. In its current configuration, the missile is 9.4 m long and 1.1 m in diameter, and weighs 4,500 kg. It uses the same two liquid-propellant engines as the Prithvi-I, however an improved liquid-propellant (TG-02/AK-27I ?) over its predecessor. The engine control allows the missile to stop climbing when it reaches an altitude of 30 km, travel horizontally at this altitude, and dive on its target at an 80° angle.
In 2002 management of the Prithvi-II was shifted from the Indian Air Force to the Indian Army and also to the Indian Navy. The naval variant is called "Dhanush". The missile has a maximum range of 250 km. Development tests on the Prithvi-II began in 1992. Regular production began around 2002.
  

Prithvi warheads

Single engine (Typ Isayev)

View into the engine bay

Engine bay


 

Core stage upper part

Currently, the “Defence Research and Development Organisation” (DRDO) developing for India an Air Defense System, based on two different interceptor missiles:

Prithvi Air Defense interceptor (PAD)
Advanced Air Defense interceptor (AAD

The Prithvi-II  SRBM is used as target-object for the tests (ground based vehicles called TGT). The naval target version is called "Dhanush"
 

     
Dhanush-04 & Dhanush -05

  
TGT-01 & TGT-04

   
TGT-05 & TGT-06

The Prithvi Air Defence (PAD) is an anti-ballistic missile developed to intercept incoming ballistic missiles outside of the atmosphere (exo-atmospheric). Based on the Prithvi missile, PAD is a two stage missile with a maximum interception altitude of 80 km. The missile is 10.0 m long, 1.1 m in diameter, and weighs 4,958 kg.
The first stage is a liquid fuelled motor while the second stage is solid fuelled. It has maneuver gas-thrusters which can generate a lateral acceleration. Guidance is provided by an intertial navigation system with mid-course updates from LRTR and active radar homing in the terminal phase. PAD has capability to engage the 300 to 2,000 km class of ballistic missiles at a speed of Mach 5.
The advanced interceptor PADM weighs 5,200 kg and is armed with a "kill vehicle" which is equipped with a innovative system to allow the missile to maneuver. The "kill vehicle" has additional a small solid fuelled motor.

PAD with radar seeker on head

PAD gimbal-controlled solid fuel motor

  
PAD-02 interceptor

http://www.youtube.com/watch?v=R1bMwdjp0HE
 

Advanced Air Defence (AAD) is an anti-ballistic missile designed to intercept incoming ballistic missiles in the endo-atmosphere at an altitude of 30 km. AAD is single stage, solid fuelled missile. Guidance is similar to that of PAD: It has an inertial navigation system, midcourse updates from ground based radar and active radar homing in the terminal phase. It is 7.5 m (25 ft) tall, weighs around 1.2 t and a diameter of less than 0.5 m (1 ft 8 in).

AAD interceptor