SOHEIL
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PSLV
The second stage is powered by a Vikas engine, burning N2O4 and UDMH. The Vikas engine is built by ISRO, is closely based on the Viking 4A engine built by SEP of France. The primary difference is that it rated for a longer burn time. The stage has been streched to increase the propellant load from 37.5 to 40.6 t.
The third stage is a solid motor. It has as polyamid fiber case and a submerged nozzle equipped with a flex-bearing-seal thrust-vector control system.
The fourth stage is used as the terminal stage of the PSLV to provide precision injection. This stage is powered by two identical pressure-fed engines using monomethyl hydrazine (MMH) and MON-3 (3% nitric acid / 97% nitrogen tetroxide) as propellant.
The PSLV payload fairing is made of aluminium. The fairing is manufactured by Hindustan Aeronautics, Ltd.
Polar Satellite Launch Vehicle (PSLV)
PSLV was initially designed to place 1,000 kg class Indian Remote Sensing (IRS) satellites into 900 km polar SSO. Since the first successful flight in October 1994, the capability of PSLV has been enhanced from 850 kg to the present 1,600 kg into 618 km polar SSO. The improvement in the capability over successive flights has been achieved by increased propellant loading in the stage motors, employing composite material for the satellite mounting structure and changing the sequence of firing of the strap-on motors.
In its present configuration, the 44.4 metre tall, 295 tonne PSLV has four stages using solid and liquid propulsion systems alternately. The first stage carrying 138 tonne of propellant. Six solid propellant strap-on motors, each carrying nine tonne of solid propellant, are strapped on to the core stage. The second stage carries 41.5 tonne of liquid propellant. The third stage uses 7.6 tonne of solid propellant and the fourth has a twin engine configuration with 2.5 tonne of liquid propellant.
The 3.2 metre diameter metallic bulbous heat shield protects the satellites and it is discarded after the vehicle has cleared the dense atmosphere. PSLV employs a large number of auxiliary systems for stage separation, heat-shield separation and so on. It has sophisticated systems to control the vehicle and guide it through the predetermined trajectory. The vehicle performance is monitored through telemetry and tracking.
PSLV-C6 validated several on board systems like PS-2 remote fill and range systems, PS-2 EGC hydraulic pump, monolithic igniters in strap on motors, etc.
The next PSLV-C7 will carry 3 satellites on board – 660 kg Indian Remote Sensing Satellite, CARTOSAT-2, 610 kg Space capsule Recovery Experiment (SRE) and the 56 kg Indonesian LAPAN TUBSAT. PSLV-C7 will use a Dual Launch Adapter (DLA), which will allow mounting the main payload CARTOSAT-2 over the adopter while SRE will be housed inside DLA. LAPAN TUBSAT will be mounted over the equipment bay. PSLV-C7 will have several improvements over PSLV-C6, besides use of DLA, like altitude based day-of-launch wind steering programme, deletion of airlift strap-on and Secondary Injection Thrust Vector Control (SITVC) system, reduced propellant loading for SITVC and modified PS-4 control electronics. During the year qualification of DLA has been completed including structural and dynamic characterisation tests. Satellite separation test has also been conducted.
Other developments related to PSLV which made progress during the year include a new 229 tonne core alone configuration of PSLV with capability to launch 1100 kg satellite into 622 km SSO, a high performance PSLV-HP to carry 1900 kg in SSO by increasing PS-2 propellant and improvement in its specific impulse and a three stage PSLV-3S for carrying 550 kg in low earth orbit.
A new motor, PSOM-XL, was static tested at SDSC SHAR, Sriharikota during the year. While the six solid propellant strap-on motors in the present PSLV carry 9 tonne of propellant, the new version, PSOM-XL, with a length of 13.5 m, has the capacity to carry ~13 tonne. PSOM-XL will further improve the capability of PSLV from 1,450 kg to 1,600 kg for a SSO.
The first Indian moon mission Chandrayaan-1 is proposed to be a lunar polar orbiter at an altitude of about 100 km from the lunar surface.
PSLV is chosen for the first lunar mission. The upgraded version of PSLV viz., PSLV-XL which has a liftoff weight of 316 tonnes, will be used to inject 1,304 kg mass spacecraft at 240 x 24,000 km orbit and the corresponding spacecraft mass is 590kg when the target lunar orbit of 100 km is achieved.
January 10, 2007. Some of the modifications in PSLV-C7 compared to the previous flight, PSLV-C6, are:
- Use of Dual Launch Adapter (DLA).
- Reduction of propellant from 2.5 tonne in the fourth liquid propellant stage.
- Deletion of Secondary Injection Thrust Vector Control (SITVC) system for one of the strap-ons ignited in the air.
- Reduction of PSLV first stage SITVC inject by 500 kg.
PSLV-C8 is the eleventh flight of ISRO's Polar Satellite Launch Vehicle (PSLV) and its first commercial launch as well. In this flight, PSLV launches the 352 kg Italian astronomical satellite, AGILE, into a 550 km circular orbit, inclined at an angle of 2.5 deg to the equator. An Advanced Avionics Module (AAM), weighing 185 kg, to test advanced launch vehicle avionics systems like mission computers, navigation and telemetry systems, is also flown on PSLV-C8.
A Dual Launch Adapter (DLA) is employed in PSLV-C8 and AGILE is mounted on top of DLA while AAM is mounted inside DLA. With a much lighter payload and the low inclination of the orbit in which AGILE is to be placed, PSLV-C8 is configured without the six solid propellant strap-on motors of the first stage. The "core alone" (CA) vehicle will have two roll-control motors in the first stage for achieving symmetry. Also, the propellant in the fourth stage is reduced by about 400 kg compared to previous PSLV flight. The core-alone PSLV-C8 will have a lift-off mass of 230 tonne.
