A Review on Hypersonic Propulsion Technology: from History to Present Scenario with a Brief Overview of Hypersonic Propulsion Programs in India

International Journal of Creative Research and Studies Volume-4 Issue-10, October 2020

INTERNATIONAL JOURNAL OF CREATIVE RESEARCH AND STUDIES www.ijcrs.org ISSN-0249-4655

A Review on Hypersonic Propulsion Technology: From History to Present Scenario with a Brief Overview of Hypersonic Propulsion Programs in India

Ayushi Mehrotra Aerospace Engineer (MS) Department of Aerospace Engineering Auburn University, Auburn, Alabama, USA

ABSTRACT Hypersonics is the regime of flight at which the velocity of flying object exceeds Mach 5. Dealing with the hypersonic flow requires a strong knowledge of high speed aerodynamics, as the regime is characterized by high amount of aerodynamic heating, shock waves and its interaction with the airframe components of a flying vehicle. Hypersonic wind tunnels and experimental rocket boosted NASA’s X-43A have been instrumental in predicting the physics involved in hypersonics. Air-breathing engines like Ramjet, have excellently demonstrated flight at supersonic velocities up to Mach 4, but it fails to operate when the requirement is to fly higher than Mach 5. This drawback was best overcome by Scramjet engines. In 2004, the experimental aircraft X-43A, that has a scramjet engine, was able to reach a velocity of Mach 9.65, with the help of an assisted rocket launch. Hypersonics is a promising propulsion technology especially for high speed applications like trans-atmospheric vehicles and space exploration. They can easily replace rockets as they are more fuel efficient, have much higher specific impulse and provide a faster means of travel. This can effectively benefit fields like space exploration, where distances between bodies are huge; it can also benefit military research and future means of aviation. In this paper, the author has attempted to present the evolution of Hypersonic Technology with time, since 1950s till up till now. The scope and future challenges involved to harness this technology with reference to India, to its maximum have also been discussed.

Keywords: hypersonic, supersonic, scramjet, space exploration, Mach, Aerodynamics, Propulsion

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1. INTRODUCTION This paper studies in detail the various advancements in the field of Scramjet design and propulsion technology; from its inception in the early 1950s to the advancements up till date. It makes a brief foray into Hypersonics and its physics and then explores the realm where Scramjets dominate the field of study. Hypersonic can be described as the regime of flight where aerodynamic heating takes place. Mach 5 and higher is considered to be the regime of hypersonic flight. Important results in hypersonics have mostly been experimental. Supersonic wind tunnels and other related devices have produced flows with speeds up to orbital velocities. Hypersonics is important because it has provided us with optimal solutions relating to thermal protection during atmospheric entry. Due to this, ballistic missile nose cones have been developed which have been vital during missions to the Moon and planets like Jupiter. The second most important application of hypersonics has been in propulsion science. It has led to the development of high speed propulsion and has pursued to develop the scramjet as an advanced ramjet. Scramjets are built to achieve near orbital velocities. A good example of advanced Scramjet engine includes the flight of NASA’s X-43A in November, 2004 at Mach 9.65 by using a rocket. Supersonic flight is achieved when an aircraft touches Mach 1, which continues up to a range of Mach 4. Air-breathing engines like Pratt and Whitney’s J-58, a hybrid turbo- ramjet, have demonstrated excellent flight at supersonic regimes. Hypersonic velocities are achieved with a flight regime ranging from Mach 5 and above. Ramjets become highly inefficient at this range, mostly because of aerodynamic heating. A new engine, the Scramjet is ideally used for hypersonic regimes. Scramjet stands for Supersonic Combustion Ramjet. Unlike the ramjet, the combustion inside a scramjet is supersonic throughout. Scramjet engine technology is a promising technology of the future especially for very high-speed applications like space exploration, trans-atmospheric vehicles etc. which require high fuel efficiency along with speed and design accuracy. Scramjet engines also have a flourishing military applications as ballistic missiles, rockets etc. usually belong to the hypersonic regime. Scramjet technology promises high-speed, efficient propulsion system design which may replace rocket propulsion for better advances in space exploration.

2. SIGNIFICANT HYPERSONIC PROPULSION PROGRAMS THROUGHOUT HISTORY 2.1 The X-15 The X-15 belonged to the X-plane series operated by the United States Air Force (USAF) and the National Aeronautics and Space Administration (NASA). It was a hypersonic, rocket-powered aircraft. It has been regarded as the most important research plane in history. It was the highest and fastest flying manned aircraft. This aircraft was operational for a period of over ten years and had set the world record for speed and altitude at 4,520 mph (6.7 Mach) and 354,200 feet respectively. It was conceptualized in order to examine all aspects of piloted hypersonic flight. [1]

Fig.1: The design of the X-15 [38]

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International Journal of Creative Research and Studies Volume-4 Issue-10, October 2020

The X-15 had set an altitude record in the 1960s. It was able to reach the edge of outer space and was able to collect valuable data which later resulted in the development of the manned and space shuttle programs. William J. Knight was the US Air Force pilot that set the X-15’s official world record for the highest speed ever recorded for a manned, powered aircraft in October 1967 at Mach 6.7 at 102,100 feet (32,120 m) at a speed of 4520 miles per hour(7274 km/hour, 2021 m/sec). This record is still unbeaten as of February, 2018. [2]

The X-15 was designed to be carried aloft and drop-launched from under the wing of a NASA B-52. The aircraft was released at an altitude of about 8.5 miles (13.7 km) at a speed of about 500 miles/hour. (805 km/hour) The rocket engine of the X-15 provided thrust for the first 80 to 120 seconds of flight. [3] The X-15 was primarily developed to provide information and data on aerodynamics, flight controls, structures etc. with reference to in flight conditions. Also, the physiological effects of high speed and high altitude flights were observed.

The X-15 was flowed for a period lasting 10 years, June 1959 to October 1968. It took a total of 199 flights. It was instrumental in the development of Apollo, Gemini and Mercury manned space programs.

2.2 The SCRAM Program SCRAM stands for Supersonic Combustion RAmjet Missile. This project was a classified project taken up by the Johns Hopkins Applied Physics Laboratory (APL) from 1962 to 1978. It was declassified in 1993. The objective was to design a family of missiles that could fit in the Talos MK-12 launcher system or the Terrier MK-10 Launcher. A variety of Mach numbers, pressures and altitudes were tested for the testing of the engine modules at a direct connect, free-jet facility. The Mach numbers tested included Mach 4 (24,000 feet), Mach 5.3 (46,000 feet), Mach 7.8 (67,000 feet) and Mach 10 (88,000 feet). The experimental results showed that external burning could be feasible means of generating lift and minimizing drag, the efficiency was unsatisfactorily low if there was a net thrust required.{4} Stable combustion in supersonic flow resulted in the feasibility of an internally burning supersonic combustion ramjet (scramjet). The analytical and other experimental studies concluded that a scramjet would produce net thrust and would be more efficient than a supersonic combustion ramjet at Mach numbers above 6 up to 8. [5] As a result of these tests, preliminary conceptual designs of scramjets- powered missiles were started in 1961. A conventional, asymmetric external-internal contraction inlet was designed. But because of the weight and complexity of the variable geometry, it was necessary to assure inlet starting which suggested that alternative fixed- geometry inlet would be desirable for expendable lighter weight missiles.[6] These missile designs that included such streamlined inlets were called the SCRAM. These inlets were self –starting, and hence they did not require variable geometry.

Fig.2: The SCRAM Missile [39]

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2.3 The National Aerospace Plane The NSAP, National Aerospace Plane program was announced in 1986 in the United States by the then president Ronald Reagan. Its objective was to develop two X-30 aircraft which would be capable of Single Stage to Orbit (SSTO) as well as horizontal takeoff and landing from conventional runways. The fuel to be used was hydrogen based and the aircraft was supposed to be hydrogen-fueled air-breathing space plane, which would have a low speed accelerator system to propel the aircraft up to Mach 3, from where the main dual-mode scramjet engine (Ramjet/Scramjet) would take over. A rocket would then take over the propulsion system at the edge of the atmosphere and provide the final energy for the orbit insertion. It was based on a classified DARPA (Defense Advanced Research Projects Agency) research program called Copper Canyon.

The speed limit set for this program was Mach 25. However, it became clear that Mach 17 would be the limit due to weight penalty and complexity of the skin heat exchanger and other propulsion systems. The program was cancelled due to lack of funds and supporting technology. [7]

Fig. 3: NSAP Aerospace Plane ‘Rockwell-30’Titled ‘Orient Express by NY Times [40]

2.4 The HySHOT Program The HySHOT flight program was an experiment designed to develop a link between pressure measurements made of supersonic combustion in the T4 shock tunnel of the University of Queensland, Australia and the ones observed in flight. This relation was developed for a scramjet configuration and it retained the necessary components for supersonic combustion. A total of five flights were made, which included: • HySHOT I, launched October 30th, 2001 • HySHOT II, launched July 30th, 2002 • HySHOT III, launched March 25th, 2006 • HySHOT IV, launched March 30th, 2006 • HyCAUSE, launched June 15th, 2007[8]

Supersonic combustion was successfully achieved in HySHOT II and III. The first flight of October 30th, 2001 was unsuccessful as it couldn’t take the experimental rocket to the planned trajectory, but it was still considered successful as it provided valuable data and information which improved the second flight.

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Fig. 4: HySHOT I, II and III [41]

The experiment provided benchmark data for computational fluid dynamics and tunnel calibrations for supersonic regime. It helped set up new regulations for launching of sounding rockets for the Australian Government. The HySHOT program experiment was developed completely on the basis of wind tunnel experiments, in order to analyze supersonic combustion. Thus, the HySHOT program successfully applied the supersonic measurements made in the shock tunnels into developing a supersonic combustion flight experiment. Thus, the HySHOT program demonstrated that shock tunnels could be effectively employed to undertake hypersonic propulsion development. [9]

Fig.5: The HySHOT IV and HyCAUSE.[42]

HySHOT program enabled the scientists to create efficient methods for both hypersonic ground and flight testing.

2.5 The HIFiRE Program HIFiRE stands for The Hypersonic International Flight Research Experimentation. It was set up to examine the fundamental science of hypersonics technology and its potential for implementation in future aeronautical systems. It involves a total of ten flights. It has been established jointly under DSTO (Defense Science and Technology Organization of Australia) and the US Air Force Research Laboratory (AFRL). University of Queensland, Australia has been involved in three flights of the HIFiRE program. They are HySHOT V, VI and VII respectively. This international collaboration has enabled the University of Queensland to build advanced scramjet prototypes and perform flight tests at speeds of more than Mach 8. [10]

• HySHOT V (HIFiRE 4) Free flying hypersonic glider It is a hypersonic waverider designed to fly at Mach 8 (8000 km/hour). It separates from its rocket boosters in space and performs controlled maneuvers while entering the atmosphere. It doesn’t have a scramjet attached. It is designed to examine and learn how to fly a hypersonic vehicle at a high altitude. It was successfully tested in July, 2017.

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• HySHOT VI (HIFiRE 7) A Free Flying Scramjet (Mach 8) It flew on March 30th, 2015. It had an up and down trajectory, just like HySHOT flights I to IV, but the scramjet separated and entered the atmosphere on its own at Mach 8. It belonged to a new generation of 3-D engines designed by the University of Queensland, Australia.

• HySHOT VII (HIFiRE 8) Sustained Scramjet Powered Flight (Mach 8) It is a scramjet powered waverider vehicle and it is designed by using the data of HySHOT V and VI. It is decided that a depressing trajectory will be used to fly this vehicle and the team plans to fly this scramjet- powered vehicle horizontally for a minute at Mach 8. This is huge compared to the small experimental window of about 5 seconds for HySHOT I-IV and VI. The launch is planned for 2019.

Fig. 6: the payload of HiFIRE 7 and HIFiRE 8 [43]

2.5 The HYPER-X Program The Hyper-X program was started by NASA. It was approximately a $230 million ground and flight testing program that lasted a total of 7 years. It was started to explore alternatives o rocket vehicles. The X-43 was an experimental hypersonic aircraft (unmanned) which was a part of the Hyper-X program. It had set several airspeed records for air-breathing jet aircraft. Currently, the X-43 is the fastest air-breathing jet aircraft on record at approximately Mach 9.6 (7310 mph or 11,850 km/hour) [12]

The X-43 was ‘drop-launched’ from a Boeing B-52 ‘Stratofortress’. The booster rocket (modified Pegasus rocket) brought the ‘stack’ (winged booster rocket) to the desired speed and altitude, the rocket was discarded and the X- 43 flew free using its own scramjet engine. There were three airplanes designed in this series. The first X-43 was destroyed after some malfunction, while the other two flew successfully with the scramjet operational for about ten seconds, proceeded by a 10-minute glide and a crash in the ocean; which was intentional.

Fig. 7: The NASA X-43 [44]

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The Hyper-X program involved the American Space Agency, NASA, and aircraft companies like Boeing, Micro Craft Inc., Orbital Sciences Corporation and General Applied Science Laboratory (GASL). The airplane X-43 was built by Micro Craft Inc. while the GASL designed the scramjet engine. The primary purpose of this program was to develop technologies for hypersonic air-breathing propulsion. As the National Aerospace Plane (NSAP) was canceled in November, 2004, a better, faster and cheaper approach was applied in the Hyper-X program. The Hyper-X program was jointly conducted by Langley Research Centre, Hampton, Virginia and Dryden Flight Research Centre, Edwards, California in phase 1. While the Langley center developed the hypersonic technology, the Dryden center focused on the flight research. The X-43 series was later replaced by the more advanced X-51. [13]

Fig. 8: The X-43 boosted by a modified Pegasus rocket shortly before it discards the rockets. [45]

After the failure of the first test, a second test was carried out in March, 2004. The Pegasus rocket successfully fired and released the vehicle at an altitude of about 29,000 meters (95,000 feet) the engine ignited successfully and he craft accelerated reaching Mach 6.83 (7,401 km/hour or 4,600 mph).

Fuel flowed for approximately 11 seconds and the craft travelled 24 kilometers. This flight made the X-43A the fastest free flying air-breathing jet engine aircraft in the world. A third version of the X-43A was flown by NASA on November 16th, 2004. Here, a new speed record was set by the X-43A at about 33,528 meters (110,000 feet) altitude of approximately Mach 9.6, 10,617 km/hour (6598 mph). The abilities of heat loads were also tested. [14]

2.6 The X-51 The Boeing X-51A ‘WaveRider’ is an unmanned, research, scramjet, and experimental aircraft designed for hypersonic flight at Mach 5 (3,300 mph; 5,300 km/hour) at an altitude of about 70,000 feet (21,000 m). It was named ‘X-51’ in the year 2005. The first powered hypersonic flight by X-51 was completed on May 26th, 2010. The X-51 completed a flight of over 6 minutes and reached a velocity of over Mach 5 for a total of 210 seconds on May 1st, 2013. This was achieved after two unsuccessful flights. It is also the longest duration powered hypersonic flight. The aircraft is referred as a ‘WaveRider’ as it effectively uses its own compression lift produced by its own shock waves. It was a joint effort of United States Air Force, DARPA, NASA, Boeing and Pratt & Whitney Rocketdyne. This program was headed by the Aerospace Systems Directorate in the US Air Force Research Laboratory (AFRL). [15]

The X-51 technology has been posited to be used in the High Speed Strike Weapon (HSSW) which is a Mach 5+ missile that is expected to enter service by mid-2020s.

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Fig. 9: X-51 ‘WaveRider’ Mounted on a B-52H [46]

The X-51 was able to complete its first powered flight on May 26th, 2010. It reached a velocity of Mach 5 (3,300 mph; 5,300 km/hour) at an altitude of about 70,000 feet (21,000 m) and flew for over 200 seconds. The test had the longest hypersonic flight time, at 140 seconds using its scramjet power.

After two seemingly unsuccessful flight tests, a third flight test took place on May 1st, 2013. The X-51 and its booster attached from a B-52H was flown and hence powered to Mach 4.8 (3,200 mph; 5,100 km/hour) by its booster rocket. It separated and ignited its engine. The test aircraft accelerated to Mach 5.1 (3,400 mph; 5,400km/hour) and flew for 210 seconds until running out of fuel and falling in the Pacific Ocean, for a total flight time of over 6 minutes. [16] This test was the longest air-breathing hypersonic flight. The Air Force Research Laboratory believes that it will serve as a research for practical applications of hypersonic flight, such as: missile reconnaissance, transport, and as an air-breathing first stage for space vehicle system.

3. THE HYPERSONIC PROPULSION PROGRAM IN INDIA 3.1 The ATV- Advanced Technology Vehicle The ATV stands for Advanced Technology Vehicle. It is been developed in order to construct the RLV, India’s first Reuse Launch Vehicle. It is a modified sounding rocket. It is based on the rocket, Rohini-560. The ATV program was created to test the development of a native, dual-mode air-breathing scramjet engine.

On May 23rd, 2016, a scaled-down prototype of the ATV was tested by the Indian Space Research Organization (ISRO). It is known as the RLV-TD (TD-Technology Demonstrator). The test airplane was attached to a solid rocket booster and carried up to 70 kilometers. The booster detached and the RLV-TD was maneuvered by a computer on- board, it glided to the Indian Ocean and then disintegrated. The RLV is expected to be built by 2030. It will serve the purpose of launching the satellites in the Low Earth Orbit and later glide down and land on a custom runway, similar to a normal airplane. ISRO hopes to reduce the launch costs of the payload by 10 times, from the current $5,000/ kilogram to about $ 2,000/ kilogram. The global average being very higher. An indigenous scramjet engine is especially designed for the ATV. Besides the scramjet engine, the RLV is also estimated to be fitted with 5 semi- cryogenic engines. [17]

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Fig. 10: The Mission Profile of the ATV test [47]

• ATV-01 On March 3rd, 2010, ISRO conducted the first test flight of the Advanced Technology Vehicle, christened ATV- D01. Weighting 3,000 kilograms, (6,600 lbs.) at lift-off and measuring 9.10 meters (29.9 feet) with a diameter of 0.56 meters (1.8 feet) It carried a passive scramjet engine combustor module which successfully reached Mach 6 for a total of 7 seconds and maintained a dynamic pressure of 80 kilopascals (12 psi). [18]

• ATV-02 On August 28th, 2016, the second test flight of the ATV-d02 was launched from the Satish Dhawan Space Centre. Weighting 3,277 kilograms (7,255lbs.) the rocket carried an active scramjet and at 55 seconds in flight, the scramjet ignited at Mach 6 and was functional for 5 seconds. The flight lasted 300 seconds and splashed down the Bay of Bengal approximately 320 kilometers (200 miles) from the space center. The combustion was sustained in one engine for 18 seconds and in the other for 14 seconds. It produced a net positive thrust. [19]

3.2 Reusable Launch Vehicle Technology Demonstrator Program (RLV-TD) Reusable Launch Vehicle-Technology Demonstrator (RLV-TD) is India’s first uncrewed, flying testbed (a platform for conducting rigorous transparent and replicable testing for scientific theories, computational tools and new technologies) It is one of India’s most technologically challenging endeavors of ISRO (Indian Space Research Organization) toward developing essential technologies for a fully reusable launch vehicle in order to enable low cost access to space. [20] It is a scaled down prototype of an eventual two-stage-to-orbit (TSTO) reusable launch vehicle.

The RLV-TD successfully completed its first atmospheric test flight on May 23rd, 2016 at 01:30 UTC from Shashi Dhawan Space Centre for 770 seconds and reached a maximum altitude of 65 km. (40 miles) The final version of this vehicle is expected to be ready by the year 2030. The fully developed RLV is expected to take off vertically like a rocket, deploy a satellite into orbit and return to earth landing on a runway like an airplane. [21]

The dimensions of RLV include a height of approximately 16m (52 ft.) [22] Length 6.5 m which is approximately 21 ft. for orbiter. RLV-TD has mass of 1.75 tonnes, (orbiter: 1.75 tonnes) wingspan of 3.6 meters and overall length of 6.5 meters (excluding the rocket). The vehicle had 600 heat-resistant tiles on its undercarriage and it features delta wings and angled tail fins. [23]

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The RLV-TD is an ambitious program by ISRO that consists of the development of hypersonic rocket with air- breathing engines coupled with reusable launch vehicle. In January 2006, ISRO was able to complete the development and tests of the Scramjet at its Vikram Sarabhai Space Centre in Thiruvananthapuram. During the Ground tests, stable supersonic combustion with an inlet Mach 6 was demonstrated for 7 seconds.

On March 3rd, 2010, The flight test of ATV-D01 sounding rocket was successfully conducted by ISRO from Satish Dhawan Space Centre at Sriharikota. At 3 tonnes, during liftoff, ATV-D01 was the heaviest sounding rocket developed by ISRO. It was mounted with a passive Scramjet engine and flew for 7 seconds achieving Mach 6 (+0.5) and dynamic pressure of 80 (+35) kPa. [24]

In January of 2012, the design of the RLV was approved by the Government of India and clearance was granted to build the vehicle. ISRO aims to bring down the cost of payload delivery to Low Earth Orbit by 80% from existing $20,000/kg to $4,000/kg [25]

The RLV-TD is being developed to test the various aspects of hybrid hypersonic flight such as auto-landing, powered cruise flight, hypersonic flight using air-breathing engine, propulsion etc. Four RLV test flights are planned by the Indian Space Research Organization (ISRO) [26]. They are HEX, (Hypersonic flight Experiment) LEX, (Landing Experiment) REX (Return Flight Experiment) and SPEX. (Scramjet Propulsion Experiment) The total cost of the project is approximately 95 crore rupees. (equivalent to US $15.4 million in 2019) Future planned developments for this project include testing of an air-breathing propulsion system, which will aim to use the oxygen in the atmosphere instead of liquefied oxygen in flight. [27]

• Hypersonic Flight Experiment (HEX) This experiment was the first of four experiments conducted on May 23rd, 2016. The sub-orbital test flight was launched at 07:00 IST (01:30 GMT) from Satish Dhawan Space Centre at Sriharikota. (80 km (50 miles) north of Chennai) The test flight launched for 770 seconds and was able to reach a maximum altitude of 65 km (40 miles) and covered a distance of 450 km (280 miles) from Sriharikota. It steered itself to an on-target splashdown to land (ditch) at a designated spot in the Bay of Bengal. The vehicle disintegrated on impact with water as it was not designed to float. Hence it was not recovered. [28]

The RLV-TD was mounted on top of and launched aboard a single-stage solid fuel booster (HS9 booster) that was delivered from strap-on boosters flown on India’s Polar Satellite Launch Vehicle. (PSLV) The booster consumed its solid propellant in 91 seconds, meanwhile the RLV-TD separated from its booster stage and peaked to a suborbital altitude of 50 km. (40 miles) The heat shield, guidance, navigation and control algorithms were tested at hypersonic speed by accurately steering the vehicle during the descent stage.

For the descend back, the vehicle was programmed to pitch its nose up, exposing silica tiles on its underside and reinforced carbon-carbon nose cap to the airflow into the thick lower layers of the atmosphere. The RLV-TD endured high temperatures of descend through the atmosphere due to its thermal protection system.

All the stages of test flight were tracked by ground station at the launch side and a shipborne terminal. All mission objectives were met and the components like navigation and control, guidance, reusable thermal protection system and descend mission management were validated successfully. [29]

3.3 Hypersonic Technology Demonstrator Vehicle (HSTDV) HSTDV is unmanned scramjet demonstrator aircraft for hypersonic speed flight. The HSTDV` program is run by the Indian Defense Research and Development Organization. (DRDO)

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The long term objective of this program is to develop a successful hypersonic missile program as the HSTDV can be used as a launcher for hypersonic cruise missiles as well as a launcher for satellites at a low cost. It is being developed as a carrier vehicle for hypersonic as well as long range cruise missiles and will also have multiple civilian applications. [30]

The objectives of the DRDO is to develop a ground and flight test hardware as a part of a plan for hypersonic cruise missile development. The DRDO’s HSTDV was intended to attain an autonomous scramjet flight for 20 seconds, using a solid rocket booster. This research will also bolster India’s attempts in developing a Reusable Launch Vehicle (RLV) for future space missions. The target was to reach Mach 6 at an altitude 32.5 km. (20 miles) [31] The initial testing was meant to validate the aerodynamics of the vehicle, as well as the thermal properties and the performance of the scramjet engine. The design for airframe attachment with the engine was completed by 2004.

On June 12th, 2019 the first flight test was performed. The cruise vehicle was mounted on Agni-I solid rocket motor, ballistic carrier vehicle to take it to the required altitude. After achieving the required altitude and the Mach, the cruise vehicle was ejected out of the launch vehicle. Mid- air scramjet engine auto-ignited and was able to propel the cruise vehicle at Mach 6. The HSTDV was flight tested from Launch pad no. 4 of the Integrated Test Range (ITR) at Dr. APJ Abdul Kalam Island near Balasore district, Odisha, by the Defense Research and Development Organization (DRDO) at 11:27 IST [3]. According to the Ministry of Defense, Government of India, the mission was a success and was able to analyze and validate critical technology. [33]

On September 7th, 2020 the Scramjet Powered Hypersonic Technology Demonstrator Vehicle (HSTDV) was successfully tested by DRDO. The cruise vehicle was launched at 11:03 IST from Dr. APJ Abdul Kalam Launch Complex at Wheeler Island atop a solid booster. At 30 km altitude, the payload fairing separated, the HSTDV cruise vehicle separated after that, followed by air intake opening, fuel injection and auto-ignition. After sustaining hypersonic combustion for 20 seconds, the cruise vehicle achieved a velocity of nearly 2km/sec. [34] This test flight was able to validate the aerodynamic configuration of the vehicle, ignition and sustained the combustion of scramjet engine at hypersonic flow. It also validated the separation mechanisms and characterized the thermo- structural materials. [35]

Fig. 11: Prototype of RLV-TD Vehicle [48] www.ijcrs.org Page | 11

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3.4 The BrahMos-II Missile The BrahMos-II or the BrahMos Mark II is a hypersonic cruise missile jointly under development by Russia’s NPO Mashinostraoeyenia and India’s DRDO (Defense Research and Development Organization) which together constitute the BrahMos Aerospace Private Limited.

It is the Second missile in the BrahMos series (Cruise Missiles). It is expected to have a range of 450 kilometers (280 miles; 240 nautical miles) and a maximum velocity of Mach 7. The cruise stage will be propelled by a scramjet air-breathing engine. It will be ready for testing and integration by 2020. [36]

The BrahMos-II has been described as the fastest cruise missile in the world. The testing of the missile started in the year 2012. Fourth-generation multi-purpose Russian Naval Destroyers are also expected to be fitted with the BrahMos-II.

Fig. 12: The Prototype of BrahMos-II [49]

The missile was renamed BrahMos-II (K) in honor of the former President of India Dr. APJ Abdul Kalam. [37]

The New BrahMos-II is capable of flight between a range of Mach 5 and Mach 7. The new missile will be made in three variants, Ground launched, airborne as well as sea launched.

4. CONCLUSION This review paper aims at listing a chronological development of the hypersonic propulsion technology around the world, along with the future avenues involved. The paper also lists special programs in the development of hypersonic propulsion technology in India as well as their future probabilities. The author especially focuses on India because India has shown huge potential in hypersonic technology development with various programs (RLV, BRAHMOS, ATV,etc.) That have been able to achieve substantial results in the field of hypersonic propulsion. In the field of space exploration, India has shown potential of becoming a future space hub and superpower by mighty missions like Chandrayaan I and II, Mangalyaan or the Mars Orbiter Mission (MOM) and the ASAT- Anti-Satellite Program. India with its economical and sustainable space technology has established itself as the future hub of hypersonics and space exploration and an equal amongst existing space giants like the US, Europe, Japan and China.

The author has tried to list and explain the most recent and the most relevant and advanced hypersonic propulsion programs from around the world in order to develop a better understanding of the advanced technology. Hypersonic propulsion technology has a huge potential which is being slowly realized by advanced projects like the aerospace planes, and missiles being developed around the world. Not just military applications, the hypersonic propulsion technology is proving to be advanced, efficient and economical in all applications, including space exploration and adventurous commercial applications.

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Recently, The Indian Space Research Organization (ISRO) has announced that it is likely to test the ground landing of its Reusable Launch Vehicle (RLV) by November or December of 2020. [50] This will enable India to develop its own reusable space shuttles. (Equivalent to the Atlantis and Columbia space shuttles of NASA) India’s ISRO has proven to provide the most economically efficient and successful space missions in the world and is credited to be the first country in the world to discover water on the Moon and reach the orbit of Mars in its first attempt, becoming the first country in Asia to do so.[51,52] A lot has been done in the development of hypersonic technology especially in India and the paper aims at highlighting all the relevant studies for budding explorers in this field.

5. ACKNOWLEDGEMENT The author wishes to acknowledge the contribution of Prof. John E. Cochran, Professor Emeritus, Auburn University for his guidance and constant endeavor in explaining the minute details of Hypersonic propulsion. The author also wishes to acknowledge, Prof. Vinod Saxena, Professor of Aerodynamics and Propulsion at Amity University, Lucknow, India for his constant guidance and support in explaining the basics of hypersonic propulsion and advanced aerodynamics and igniting the author’s curiosity towards hypersonic and rocket propulsion.

6. REFERENCES [1] Chant, Christopher and Taylor, Michael J.H. The World's Greatest Aircraft. Edison, NJ: Chartwell Books, 2006, p. 284, North American X-15.

[2] Gibbs Yvonne (February 28th, 2014) ‘NASA Armstrong Fact Sheet X-15 Hypersonic Research Program’ NASA https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html

[3] NASA Armstrong Fact Sheet: B-52B "Mothership" Launch Aircraft 6th Feb., 2002 https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-005-DFRC.html

[4] Frederick S. Billig ‘Supersonic Combustion ramjet Missile’ AIAA Journal of Propulsion and Power Vol. 11 No. 6 November-December, 1995

[5] Dugger G.L., Deklan B., Billig F.S., Matthews S.E., ‘Summary Report on External Ramjet Program’ Johns Hopkins University Applied Physics Lab TQ-419, Laurel, MD, October 1991.

[6] Billig F.S. ‘A Review of External Burning Ramjets’ Johns Hopkins Univ. Applied Physics lab TQ-801 Laurel, MD, December 1961.

[7] T.A. Heppenheimer ‘Facing the Heat Barrier: A History of Hypersonics’ Chapter: 4 ‘First Thoughts of Hypersonic Propulsion’ Pg. 168, NASA, 2007.

[8] ‘About the HySHOT Program’ The University of Queensland, Australia, http://hypersonics.mechmining.uq.edu.au/hyshot-about

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[9] A. Paul, H. Alesi, S. Anderson, “The Development of the HySHOT Flight Program’ Centre for Hypersonics, Division of Mechanical Engineering, University of Queensland, Australia. Springer, August, 2010.

[10] ‘Hypersonic International Flight Research and Experimentation (HIFiRE) Fundamental Science and Technology Development Strategy’ AIAA, May, 2008.

[11] ‘An Overview of the HIFiRE Flight 2 Project’ AIAA, January 10th, 2013

[12] Thompson Elvia, Keith Henry and Leslie Williams ‘Faster than a Speeding Bullet: Gunnies Recognizes NASA Scramjet’ NASA official report, June 20th, 2005 https://www.nasa.gov/home/hqnews/2005/jun/HQ_05_156_X43A_Guinness.html.

[13] T.A. Heppenheimer ‘Facing the Heat Barrier: A History of Hypersonics’ Chapter 9: ‘Hypersonics after NSAP’ page 257, NASA, 2007.

[14] Gibbs Yvonne (February 28th, 2014) ‘NASA Armstrong Fact Sheet X-15 Hypersonic Research Program’ NASA. https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html

[15] ‘Successful Design Review and Engine Test Bring Boeing X-51A Closer to Flight’ Official Boeing report, Boeing, https://s2.q4cdn.com/661678649/files/doc_financials/annual/2012/2012_annual_report.pdf June 1st, 2007

[16] ‘Boeing X-51A WaveRider Sets Record with Successful 4th Flight’ Official Boeing Report, Boeing, May 3rd, 2013. https://apps.dtic.mil/dtic/tr/fulltext/u2/a593742.pdf

[17] Mukunth Vasudevan ‘ISRO Plans Scraamjet Engine Test atop Its Heaviest Sounding Rocket in July’, The Wire, https://science.thewire.in/space/isro-scramjet-sounding-rocket-rlv/July 13th, 2016

[18] ‘Successful Flight Testing of ISRO’s Scramjet Engine Technology Demonstrator’ Official ISRO report, ISRO, August 28th, 2016. https://www.isro.gov.in/launchers/isro%E2%80%99s-scramjet-engine-technology- demonstrator-successfully-flight-tested

[19] ‘Successful Flight Testing of Advanced Sounding Rocket’ ISRO official Report, ISRO, March 3rd, 2010. https://www.isro.gov.in/hi/node/509

[20] Official ISRO Report: RLV-TD isro.gov.in/launcher/rlv-td May 23rd, 2016

[21] ‘India Flies Winged Spaceplane on Experimental Sub-Orbital Launch’, spaceflightnow.com 24th May, 2016 https://spaceflightnow.com/2016/05/23/india-flies-winged-space-plane-on-experimental-suborbital-launch/

[22] ‘Modeling and Control of Launch Vehicles’, https://www.sc.iitb.ac.in/~pdsc2014/MVD_talk.pdf

[23] ‘ISRO’s Small Steps towards developing its own Reusable Rocket (Reusable Launch Vehicle RLV Program) https://www.livemint.com/Politics/T25O2kOeVcOL2vRfml0baK/Isros-small-steps-towards-developing-its-own- reusable-rocke.html Dec. 27th, 2015

[24]‘Flight Testing of Advanced Sounding Rocket’ISRO May 23rd, 2016 https://www.isro.gov.in/update/03-mar- 2010/successful-flight-testing-of-advanced-sounding-rocket www.ijcrs.org Page | 14

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[25] ‘Breakthrough in Supersonic Combustion Technology’ Vikram Sarabhai Space Centre May 23rd, 2016 https://www.isro.gov.in/update/10-jan-2006/isro-achieves-breakthrough-supersonic-combustion-technology

[26] ‘Demonstration Program’, ISRO, May 23rd, 2016 isro.gov.in/update/23-may-2016/india’s-reusable-launch- vehicle-technology-demonstrator-rlv-td-successfully

[27] ‘ISRO’s Reusable Launch Vehicle What Happened and what’s next?’ thewire.in, May 23rd, 2016 https://science.thewire.in/space/isros-reusable-launch-vehicle-what-happened-and-what-next/

[28] ‘ISRO to Test Rocket that Uses Oxygen Directly from the Atmosphere to Fuel Itself’, ISRO, 26th May, 2016 https://www.isro.gov.in/update/28-aug-2016/successful-flight-testing-of-isros-scramjet-engine-technology- demonstrator

[29] ‘India’s Reusable Launch Vehicle Successfully Flight Tested’ ISRO, May 23rd, 2016 https://www.isro.gov.in/update/23-may-2016/india%E2%80%99s-reusable-launch-vehicle-technology- demonstrator-rlv-td-successfully

[30] T.S. Subramanian (9th May, 2008) ‘DRDO Developing Hypersonic Missile’, The Hindu, Chennai, India https://www.thehindu.com/sci-tech/science/india-successfully-testfires-shourya-missile/article2482010.ece

[31] ‘India Successfully Test fires Hypersonic cruise Missile’, Livemint.com, 22nd March, 2020 https://www.livemint.com/news/india/india-successfully-test-fires-hypersonic-technology-demonstrator-vehicle- 11599463789483.html

[32] ‘India Successfully Conducts Flight Test of Unmanned Scramjet Demonstrator Aircraft’, The Times of India, 12th June, 2019 https://timesofindia.indiatimes.com/india/india-successfully-conducts-flight-test-of-unmanned- scramjet-demonstration-aircraft/articleshow/69753799.cms

[33] ‘India Gets Success in Scramjet Demonstrator Aircraft Test’, India Today, https://www.indiatoday.in/india/story/india-gets-success-in-scramjet-demonstrator-aircraft-test-1547537-2019-06- 12

[34] ‘DRDO Successfully Tests Hypersonic Technology Demonstrator Vehicle’, pib.gov.in, 7th September, 2020 https://pib.gov.in/Pressreleaseshare.aspx?PRID=1651956

[35] ‘India Successfully Tests Hypersonic Technology Demonstrator Vehicle with Scramjet Engine’, Rajat Pandit, Times of India, September 7th, 2020 https://timesofindia.indiatimes.com/india/india-successfully-test-scramjet- technology-for-hypersonic-missiles/articleshow/77973889.cms

[36] ‘India and Russia to Develop a New Hypersonic Cruise Missile’ from BrahMos.com, official website of the BrahMos missile. December 12th, 2010. http://brahmos.com/press-rel.php

[37] ‘Hypersonic version of the BrahMos Missile on the way with Mach 7’ The Economic Times, October 9th, 2011. https://economictimes.indiatimes.com/news/defence/india-successfully-test-fires-over-400-km-strike-range- brahmos-supersonic-cruise-missile/articleshow/78402626.cms

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[38] NASA Armstrong Fact Sheet: X-15 Hypersonic Research Program https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html

[39] Billig, FS "SCRAM-A Supersonic Combustion Ramjet Missile", AIAA paper 93-2329, 1993

[40]https://www.nytimes.com/2014/10/21/science/25-years-ago-nasa-envisioned-its-own-orient-express.html

[41] Official Website of the University of Queensland, Australia, The HySHOT program

[42] Official Website of the University of Queensland, Australia, The HyCAUSE program http://hypersonics.mechmining.uq.edu.au/hyshot-about

[43] Official Website of University of Queensland, Australia, The HiFIRE Program http://hypersonics.mechmining.uq.edu.au/hifire

[44] NASA Armstrong Fact Sheet: HyperX Program https://www.nasa.gov/centers/armstrong/news/FactSheets/FS- 040-DFRC.html

[45] NASA Armstrong Fact Sheet: HyperX Program https://www.nasa.gov/centers/armstrong/news/FactSheets/FS- 040-DFRC.html

[46] U.S. Airforce official Website X-51A ‘Waverider’https://www.af.mil/About-Us/Fact- Sheets/Display/Article/104467/x-51a-waverider/

[47] ISRO official Website- The ATV Program https://www.isro.gov.in/launchers/isro%E2%80%99s-scramjet- engine-technology-demonstrator-successfully-flight-tested

[48] ISRO official Website- The RLV-TD Program https://www.isro.gov.in/launcher/rlv-td

[49] BRAHMOS official website http://brahmos.com/press-rel.php

[50] ‘India’s Own Space Shuttle: ISRO Likely to Test Ground Landing of Its Reusable Launch Vehicle by End of This Year’ Swarajya.com, October 7th, 2020 https://swarajyamag.com/insta/indias-own-space-shuttle-isro-likely- to-test-ground-landing-of-its-reusable-launch-vehicle-by-end-of-this-year

[51] ‘Dear Mangalyaan: What India's Mars mission means to me’, Geetha Iyer, https://www.nationalgeographic.com/science/2018/11/dear-mangalyaan-mars-orbiter-mission-india-space/ Nov 15th, 2018

[52] ‘Water on the Moon’, ISRO official website https://www.isro.gov.in/water- moon#:~:text=Chandrayaan%2D1%20data%20showed%20evidence,(tens%20of%20meters%20deep).&text=Initi ally%20it%20showed%20the%20presence,microns)%20in%20the%20reflected%20sunlight.

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7. AUTHOR’S BIOGRAPHY Ayushi Mehrotra is a Master of Science (MS) in Aerospace engineering from Auburn University and graduated in May, 2020 with specialization in Rocket and Hypersonic propulsion. She has an extensive background in Aerospace and completed her undergraduate also in Aerospace Engineering with minors in Hypersonic propulsion from Amity University, India. She is a budding researcher in the field of air-breathing hypersonic propulsion and rocket propulsion and aspires to pursue further specialization and research in the field of hypersonics and rockets. Her research interests include plasma rockets, spacecraft propulsion and air-breathing hypersonic engines, like Scramjet.