This is a 2007 article about HSTDV from one of the blog....and that time itself it was projected that HSTDV may fructify by 2013-2015 ....
Hypersonic Technology Demonstrator Vehicle (HSTDV)/ Avatar (Rebirth)
An eight-meter technology demonstrator is being built by the Defense Research & Development Laboratory (DRDL) in Hyderabad and is due to be tested sometime in the coming months. The demonstrator vehicle, being developed in cooperation with Israeli Aerospace Industries (IAI), will be powered by a "Scramjet" engine that takes in oxygen from the atmosphere and burns liquid hydrogen.
The hypersonic prototype will apparently be a precursor to DRDO's Aerobic Vehicle for Hypersonic Aerospace Transportation (AVATAR).
According to senior DRDO officials, the primary function of the vehicle is to act as a "reusable missile launcher, one which can launch missiles, land ... and be loaded again for more missions."
The proposed AVATAR will be able to take off and land like an aircraft and will also be capable of placing a payload of 1,000kg in low-earth orbit.
AVATAR would take off horizontally like conventional airplanes from conventional airstrips using turbo-ramjet engines that burn air and hydrogen. Once at a cruising altitude, the vehicle would use scramjet propulsion to accelerate from Mach 4 to Mach 8.
In this hypersonic cruise phase, an on-board system will collect air from which liquid oxygen will be separated. The liquid oxygen collected then would be used in the final flight phase, when the rocket engine burns the collected liquid oxygen and the carried hydrogen to attain orbit.
The vehicle will be designed to permit at least a hundred re-entries into the atmosphere.
The non-military version, a Re-usable Launch Vehicle (RLV), is similar in concept and has the Indian Space Research Organisation as the lead development agency.
Binoy's Tech Blog: Scramjet
Jun 21, 2007
What's a Scramjet?
One thing has always been true about rockets: The farther and faster you want to go, the bigger your rocket needs to be! Why? Rockets combine a liquid fuel with liquid oxygen to create thrust. Take away the need for liquid oxygen and your spacecraft can be smaller or carry more payload.That's the idea behind a different propulsion system called "scramjet," or Supersonic Combustion Ramjet: The oxygen needed by the engine to combust is taken from the atmosphere passing through the vehicle, instead of from a tank onboard. The craft becomes smaller, lighter and faster.
How fast? Researchers predict scramjet speeds could reach 15 times the speed of sound. An 18-hour trip to Tokyo from New York City becomes a 2-hour flight.
Speeds greater than Mach 5 are called hypersonic, equivalent to about one mile per second or approximately 3,600 miles per hour at sea level. A regular passenger plane flies at 0.8 Mach while fast military jets fly at Mach 2.
SR-71 Blackbird, the fastest jet flies at Mach 3.2. The fastest rocketplane, X-15 flied once at Mach 6.6 way back in 1960. Russian jets(unmanned) have flown at Mach 6.4. Pretty evident as it is, flying at hypersonic speeds is difficult. According to NASA it is "one of the greatest aeronautical research challenges".
Challenges involved
There are 2 basic technical challenges that must be overcome to fly at such speeds:
Number one, is the development of a new type of non-rocket engine.
and the development of advanced materials including Titanium and its alloys and other composite materials that can handle the heat associated with hypervelocity flight.
Apart from the above, the lack of infrastrcture and knowledge required to handle cryogenic fuels in current defence and commercial facilities is a headache.
Advantages
Air-breathing engines have several advantages over rockets. Because the former use oxygen from the atmosphere, they require less propellant--fuel, but no oxidizer--resulting in lighter, smaller and cheaper launch vehicles. To produce the same thrust, air-breathing engines require less than one seventh the propellant that rockets do. Furthermore, because air-breathing vehicles rely on aerodynamic forces rather than on rocket thrust, they have greater maneuverability, leading to higher safety: flights can be aborted, with the vehicle gliding back to Earth. Missions can also be more flexible.
The Scramjet
The scramjet engine is the key enabling technology for sustained hypersonic flight. Propelled by this special type of air-breathing jet engine, a high- performance hypersonic craft might even be able to fly into orbit - a possibility first considered more than four decades ago. Recently, as the technology has matured and as the demand for more efficient Earth-to-orbit propulsion grows, scientists have begun seriously considering such systems for access to space.
Scramjets (supersonic-combustion ramjets) are those in which the airflow through the whole engine remains supersonic. It is mechanically simple, but vastly more complex aerodynamically than a jet engine. In a scramjet powered aircraft, there must be tight integration between the airframe and the engine. Scramjet technology is challenging because only limited testing can be performed in ground facilities. Long duration, full-scale testing requires flight test speeds above Mach 8. X-43 Hyper-X, NASA's testbed for the scramjet, serves this purpose. To get the engine to that speed, some other power has to be used. In the Hyper-X, this will be provided by OSC's pegasus booster. It must be noted here that scramjets are good only for sustaining hypersonic speeds, not for achieving them from zero.
Because neither scramjets nor ramjets can operate efficiently when they are traveling below Mach 2 or 3, a third type of propulsion (perhaps turbojet or rocket) is required for takeoff. So-called rocket-based combined-cycle engines, which could be used in a space vehicle, rely on a rocket that is integrated within the scramjet combustor to provide thrust from takeoff through subsonic, low-supersonic and then ramjet speeds. Ramjet operation is then followed by scramjet propulsion to at least Mach 10 or 12, after which the rocket is utilized again to supplement the scramjet thrust. Above Mach 18, the rocket by itself propels the vehicle into orbit and enables it to maneuver in space. NASA is currently testing several variations of such a systm.
Progress on Ground
On August 16, 2002, the University of Queensland in Australia completed the first successful flight of a scramjet vehicle, reaching speeds of Mach 7, or seven times the speed of sound.
NASA's Hyper-X program is working to develop scramjets into a practical technology. The X-43A, a 12-foot long scramjet-powered research vehicle, was constructed by MicroCraft, Inc., now known as Alliant Techsystems, Inc. The company fabricated three X-43A aircraft for NASA, flown aboard modified Pegasus rockets developed by the Orbital Sciences Corporation. The Pegasus is dropped by a B-52 aircraft and launched to an altitude of over 90,000 feet, where the X-43A is released and flown under its own power.
AVATAR
A surprising entrant in this race to develop a commercially viable scramjet based hyperplane is our own country, India. The 'Aerobic Vehicle for hypersonic Aerospace TrAnpoRtation' (AVATAR) is a hyperplane concept from India. It is planned to be the size of a MiG-25 fighter and would be capable of delivering a 500 kg to 1000 kg payload to low earth orbit at a rather petty rate of Rs 3500/- per kg assuming an airframe life of 100 launches.
Weighing only 25 tonnes - 60 per cent of which is liquid hydrogen fuel - Avatar is said to be capable of entering into a 100-km orbit in a single stage and launching satellites weighing up to one tonne.
AVATAR would take off horizontally like conventional airplanes from conventional airstrips using turbo-ramjet engines that burn air and hydrogen. Once at a cruising altitude, the vehicle would use scramjet propulsion to accelerate from Mach 4 to Mach 8. AVATAR or Avtar was first announced in May 1998 at the 'Aero India 98' ehxibition held at Bangalore.
The AVATAR is being developed by India's Defence Research and Development Organisation or DRDO. Air Commodore Raghavan Gopalaswami(Retd.), former chief of Bharat Dynamics Ltd, Hyderabad (which produces India's military missiles) is heading the project. The initial development budget is only $5 million, but project supporters claim that the vehicle can be built in ten years with total funding of under $2 billion. Designers admit, however, that international assistance would be required for the project to reach its goal.
In addition to the DRDO team working on the conceptual design, development of technology components is being undertaken by as many as 23 academic institutions (IITs, IISc etc) in India as well. A Hyderabad-based private company CIM Technologies is also participating in the project.
Both the scramjet engine concept and the liquid oxygen collection process have already undergone successful tests at DRDO and at the Indian Institute of Science, Bangalore. DRDO has approved further testing of the liquid oxygen process and assigned a team to conduct a detailed review of the vehicle’s design.
Currently DRDO plans to build and fly a scaled down version called Light-Avatar (LAVATAR?), weighing just 3 tonnes at take off. To be built by CIM technologies by 2006, mini-Avatar will not go into space but will demonstrate all technologies used in Avatar including oxygen collection. It will use the India's Kabini jet engine.
It is claimed that the real AVATAR would be viable by as early as 2013-2015(!) - provided international co-operation is available.