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Reusable Launch Vehicle - Technology Demonstrator (RLV-TD) is a first step towards realizing a Two Stage To Orbit (TSTO) fully re-usable launch vehicle, a series of technology demonstration missions have been conceived. For this purpose a Winged Reusable Launch Vehicle technology Demonstrator (RLV-TD) has been configured. The RLV-TD will act as a flying test bed to evaluate various technologies viz., hypersonic flight, autonomous landing, powered cruise flight and hypersonic flight using air breathing propulsion. First in the series of demonstration trials is the hypersonic flight experiment (HEX).

The RLV has been conceived by ISRO as a space launch system that will significantly cut down launch cost from the present level of around $12,000 / kg. ISRO displayed a scale model of the RLV-TD at Aero India 2009. The RLV will possess wings and tail fins, and will be launched atop a 9 ton solid booster called S-9, similar to the ones on the PSLV.

ISRO plans to achieve RLV capability in several phases:

  • HEX (Hypersonic Flight Experiment)
  • LEX (Landing Experiment)
  • REX (Return Flight Experiment)
  • SPEX (Scramjet Propulsion Experiment)

  1. Re-entry Technology Development

    In the first phase, which is currently underway, ISRO will develop re-entry technology, which will cover issues like precise control of the angle of entry into the atmosphere, materials technology to minimize the chance of burn-up at the high temperatures generated during re-entry, and control of the spacecraft to ensure its landing at the desired spot on the ground. In the first trial-flight in 2010, the RLV will not be recovered from sea because it will not be cost-effective to do so. ISRO will instead use telemetry data data on the re-entry, deceleration and return.

    A follow-up mission, SRE 2, is planned in the 2010-11 time frame. During the mission, the booster rocket will take the RLV to a specific altitude, release the RLV and fall into the sea. On re-entry into the earth’s atmosphere, the RLV will land in the sea, to be recovered.

  2. RLV Runway Recovery

    In the second phase, RLV will then re-enter the atmosphere at hypersonic speed and use aerodynamic breaking to decelerate. It will be brought to a gliding, unpowered cruise speed of about 0.8 mach, and slowed down further to make a horizontal landing.

    In January 2007 ISRO launched Space Recover Experiment (SRE), a 1,212-pound (550-kg) space capsule into orbit, along with Cartosat-2, using a PSLV. It then deorbited the SRE and successfully guided it to a splash down in the Bay of Bengal, validating manned flight re-entry technology.

  3. Scramjet Power

    Eventually, the RLV will be powered by an air breathing scram jet. It is hoped that RLV technology will mature by 2015 by which time the solid rocket booster used as the first state will also be recovered and reused. The RLV and the rocket booster will be separately recovered, with the former making a conventional landing on a runway and booster making a parachute landing.

    Unlike NASA's Space Shuttle, which powers itself into orbit around the earth and subsequently de-orbits and re-enters the atmosphere to glide back to a landing, ISRO's RLV is not designed to enter orbit. It is a pure launcher. Not a spacecraft cum launcher. It will loft a satellite into orbit and immediately re-enter the atmosphere and glide back for a conventional landing.

Advanced Technology Vehicle - Scramjet Development Flight

In an attempt to make its rockets lighter and carry heavier satellites, the Indian space agency is planning to flight test by the end of this year its own air-breathing engine that will use atmospheric oxygen as fuel. Air-breathing engines use atmospheric oxygen and burn it with the stored on-board fuel to generate the onward thrust. Conventional rockets carry both oxygen and chemical fuel on board.

On March 3rd 2010, ISRO conducted the first unpowered flight test of the Scramjet engine that it is developing under the RLV technology demonstrator program. The test was conducted at Sriharikota space-port using a sounding rocket and described by ISRO as a complete success.

The Advanced Technology Vehicle (ATV) - D01 booster combination weighed 3 tons. The rocket reached an altitude of 46km in 120 seconds (two minutes) and the entire flight duration was 240 seconds (four minutes). The booster accelerated the passive scramjet to Mach 6 and sustained Mach 6 +.05 and dynamic pressure (80 + 35 kPa) for seven seconds. These conditions are required for a stable ignition of active scramjet engine combustor module planned in the next flight of ATV.

ISRO plans to do a series of ground tests of the air breathing engine before the planned year end launch of the ATV-D02. A second developmental test flight is planned by the end of 2010.

A scramjet consists of a tube through which inlet air is compressed by the high speed of the vehicle, a chamber where fuel is combusted, and a nozzle through which the exhaust jet leaves at higher speed than the inlet air. Jet engines use a compressor to squeeze air into the engine, then spray fuel into the compressed air and ignite it to produce thrust by funnelling it through the back.

The advantage of air breathing engine is that it makes the rocket lighter - as oxygen is not carried - enabling it to carry heavier satellites. Further, it reduces the cost of launch and will help make ISRO a very cost competitive player in the global satellite launch industry. However, as air breathing engine systems can operate only during the atmospheric phase of flight, they will have to be adapted along with the conventional chemical rockets.

Target Completion Date

It is hoped that RLV technology will mature by 2015 by which time the solid rocket booster used as the first state will also be recovered and reused.

Article Contributers: Vijainder K Thakur
 
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