ISRO’s Next-Gen LV may assume PSLV’s role

ISRO’s Next-Gen LV may assume PSLV’s role

Subject: Science and technology

Context: ISRO is developing Next Generation Launch Vehicle (NGLV), which will replace its ‘trusted work horse’ PSLV in the future.

Concept:

About NGLV

• ISRO’s NGLV will be a three-stage reusable heavy-lift vehicle.
• Pay load capacity will be around 10 tonnes to Geostationary transfer orbit(GTO) and twice the capacity to Low earth orbit(LEO).
• NGLV will feature semi-cryogenic propulsion for the booster stages which is cheaper and efficient.
• Potential applications will be in the areas of deep space missions, launching communication satellites, future human missions and cargo missions.
• It allows bulk manufacturing and the turnaround time is minimal.
• Till now, PSLV and GSLV are the major launch vehicles employed by the ISRO for satellite launches.

PSLV vs GSLV

• Both PSLV (Polar Satellite Launch Vehicle) and GSLV (Geosynchronous Satellite Launch Vehicle) are the satellite-launch vehicles (rockets) developed by ISRO. PSLV is designed mainly to deliver the “earth-observation” or “remote-sensing” satellites with lift-off mass of up to about 1750 Kg to Sun-Synchronous circular polar orbits of 600-900 Km altitude.
• The remote sensing satellites orbit the earth from pole-to-pole (at about 98 deg orbital-plane inclination). An orbit is called sun-synchronous when the angle between the line joining the centre of the Earth and the satellite and the Sun is constant throughout the orbit.
• Due to their sun-synchronism nature, these orbits are also referred to as “Low Earth Orbit (LEO)” which enables the on-board camera to take images of the earth under the same sun-illumination conditions during each of the repeated visits, the satellite makes over the same area on ground thus making the satellite useful for earth resources monitoring.
• Apart from launching the remote sensing satellites to Sun-synchronous polar orbits, the PSLV is also used to launch the satellites of lower lift-off mass of up to about 1400 Kg to the elliptical Geosynchronous Transfer Orbit (GTO).
• PSLV is a four-staged launch vehicle with first and third stage using solid rocket motors and second and fourth stages using liquid rocket engines. It also uses strap-on motors to augment the thrust provided by the first stage, and depending on the number of these strap-on boosters, the PSLV is classified into its various versions like core-alone version (PSLV-CA), PSLV-G or PSLV-XL variants.
• The GSLV is designed mainly to deliver the communication-satellites to the highly elliptical (typically 250 x 36000 Km) Geosynchronous Transfer Orbit (GTO). The satellite in GTO is further raised to its final destination, viz., Geo-synchronous Earth orbit (GEO) of about 36000 Km altitude (and zero deg inclination on equatorial plane) by firing its in-built on-board engines.
• Due to their geo-synchronous nature, the satellites in these orbits appear to remain permanently fixed in the same position in the sky, as viewed from a particular location on Earth, thus avoiding the need of a tracking ground antenna and hence are useful for the communication applications.
• Two versions of the GSLV are being developed by ISRO. The first version, GSLV Mk-II, has the capability to launch satellites of lift-off mass of up to 2,500 kg to the GTO and satellites of up to 5,000 kg lift-off mass to the LEO. GSLV MK-II is a three-staged vehicle with first stage using solid rocket motor, second stage using Liquid fuel and the third stage, called Cryogenic Upper Stage, using cryogenic engine.

Semi-Cryogenic Engine:

• Unlike a Cryogenic engine, a Semi Cryogenic engine uses Refined kerosene instead of liquid hydroge The liquid oxygen is used as a Oxidiser. That’s the advantage of using a Semi Cryogenic engine as it requires Refined Kerosene which is lighter than liquid fuel and can be stored in a normal temperature.
• Kerosene combined with liquid oxygen provide a higher thrust to the rocket. Refined Kerosene occupies less space, making it possible to carry more propellant in a Semi Cryogenic engines fuel compartment.
• A semi cryogenic engine is more powerful, environment friendly and cost effective as compared to a cryogenic engine.

Re usable Rockets

• The future rockets are meant to be reusable. Only a small part of the rocket would be destroyed during the mission.
• The bulk of it would re-enter the earth’s atmosphere and land very much like an airplane, and can be used in future missions.
• Reusable rockets would cut down on costs and energy, and also reduce space debris, which is becoming a serious problem because of the large number of launches.
• Fully-reusable rockets are still to be developed, but partially-reusable launch vehicles are already in use.
• ISRO has also developed a reusable rocket, called RLV-TD (Reusable Launch Vehicle Technology Demonstrator) which has had a successful test flight in 2016.