Solid Rocket Motors and its clasification

 

Classification of Solid Motors

Solid rocket motors are classified into four categories. They are

1.   Boosters

        Used as the first stage of a launch vehicle (Rocket). It provides the required upward thrust to enable the lift of the rocket. It also provides the sufficient thrust to overcome the fiction from the lower atmosphere during it flight.  

2.   Upper stages

Upper stage solid motors are used in any other stage other than first stage. It can be second, third or fourth stage based on the vehicle configuration. It operates above the lower atmospheric region.  So the thrust produced by upper stage motors are less compared to booster solid motors. Since it is an upper stage motor, its inert weight should be maintained as small as possible.

3.   Strapons

 It provides the required upward thrust to enable the lift of the rocket along with the booster.

4.   Special motors -The special Motors are further classified as

•   Igniters
•   Separation rockets
•   Ullage motors
•   Sounding rockets
•   Missiles
•   Spin / de-spin motors

  

Early Indian Satellites

Early Indian Satellites 

Aryabhata is the first Indian made satellite launched into LEO on April 19, 1975 by a USSR rocket. It was used for conducting experiment in space in the area of X-ray astronomy, solar physics etc. The main objective of the satellite was to give experience in the design, development and fabrication and operation of the satellite system. 

 Aryabhata 

This was followed by Bhaskara I & II satellite which were also launched from Russian rockets. This carried 2 TV cameras, one in visible and other in near infrared band to carry out scientific experiments. 

This was followed by the development of a geo-synchronous satellite, APPLE (Ariane Passenger Payload Experiment) which was launched on June 19, 1981 by Ariane launch vehicle. APPLE was a geo-synchronous communication satellite. 

With the development of the Indian launch vehicles SLV-3, ASLV, Rohini series satellite were also developed for carrying out scientific experiments in LEO. 

SROSS Satellite 

Polar Satellite Launch Vehicle (PSLV)

Polar Satellite Launch Vehicle (PSLV)

Polar Satellite Launch Vehicle (PSLV) can carry 1 ton class spacecraft in 900 Km sun synchronous orbit.   The PSLV is a four stage vehicle adopting solid and liquid propulsion systems.

First stage

The first stage motor has 2.8 m diameter. The first stage propellant casing is made of maraging steel.  139 tons of HTPB solid propellant is used in first stage of PSLV vehicle. This stage also has six numbers of strapon motors derived from SLV programme. The control of first stage is done by adopting multi-port SITVC system.

Second stage

The second stage is a liquid stage. It uses N2O4 as the oxidiser and UDMH as the propellant. The fuel and propellant are stored in 2.8 m dia tankages. It has a Vikas engine generating a thrust of 75 tons.

 Third stage

The third stage of PSLV is also a solid motor. It is carrying 7 tons of propellant. The third stage motor case is made out of Kevlar composite materials and it uses a flex nozzle control system. 

Fourth  stage

The fourth stage is a liquid stage using N₂O₄ as oxidizer and MMH as propellant . It have two engines of 7 kN thrust. The tankages are made of titanium alloy. 

The vehicle equipment Bay is housed around the 4^th stage which consists of vehicle onboard navigation, guidance and control system, Power system etc. 

The spacecraft is interfaced with the payload adaptor with merman band separation system. 

The first successful launch of PSLV took place on October 15, 1994 carrying Indian Remote Sensing Satellite of 900 kg mass. This was followed by number of successful launches of PSLV for IRS missions including that of carrying multiple spacecraft in the same launch. PSLV is an operational system which can carry LEO/ SSPO/ GTO missions in a cost effective manner.

The overall lift-off mass of the vehicle - 297 tons

Payload capacity of PSLV : 

Low Earth Orbit (LEO)                         - 3.5 tons

Sun Synchronous Polar Orbit (SSPO) - 1.6 tons

Geo Transfer orbit (GTO)                    - 1 ton.