High Speed Air Breathing Propulsion 2010

Olá leitor!

Segue abaixo um artigo em inglês postado no site do “American Institute of Aeronautics e Astronautics (AIAA)” na página do “High Speed Air Breathing Propulsion (HSABP) Technical Committee” destacando a tecnologia de vôo hipersônico que vêm sendo desenvolvida atualmente nos EUA, Austrália, Brasil, França, Japão e Rússia.

Duda Falcão

HIGH SPEED AIR

BREATHING PROPULSION 2010

Moving Faster Towards the Future

2010 was the year of the scramjet‐powered X‐51

Waverider, soaring at Mach 5 for over 3 minutes

and setting a new hypersonic flight world Record

DORA MUSIELAK

AIAA HSABP TC Communications

Airbreathing hypersonic propulsion entered a new era in 2010. The 7.9‐m‐long X‐51A WaveRider, powered by a Pratt & Whitney Rocketdyne scramjet engine, made aviation history on May 26 with the longest ever scramjet‐powered flight. “This first flight test brings aviation closer than ever to the reality of regular, sustained hypersonic flight,” said Curtis Berger, director of hypersonic programs at Pratt & Whitney Rocketdyne. “We are very proud to be part of the team that made this possible.”

The X‐51A program is a collaborative effort of AFRL, DARPA, Boeing, and Pratt & Whitney Rocketdyne. During its flight, the WaveRider was carried beneath an Air Force B‐52 and dropped from an altitude of 50,000 ft. A rocket booster propelled the cruiser to a speed greater than Mach 4.5, creating the supersonic environment necessary for starting its flight. Separating from the booster, the SJY61 scramjet ignited, initially on gaseous ethylene; it then transitioned to JP‐7 fuel.

The achievement is significant, because this is the first hypersonic flight by a hydrocarbon‐ fueled scramjet. “We are ecstatic to have accomplished many of the X‐51A test points during its first hypersonic mission,” declared Charlie Brink, X‐51A program manager with AFRL. Brink called the leap in engine technology “equivalent to the post‐WW II jump from propeller‐driven aircraft to jet engines.”

On that historic day, the X‐51 launched about 10 a.m. from Edwards Air Force Base, carried aloft under the left wing of an Air Force Flight Test Center B‐52 Stratofortress. Then, flying at 50,000 ft. over the Pacific Ocean Point Mugu Naval Air Warfare Center Sea Range, it was released. Four seconds later, an Army Tactical Missile solid rocket booster accelerated the X‐51 to about Mach 4.8 before it and a connecting interstage were jettisoned.

The launch and separation were normal. Then the SJY61 scramjet engine ignited, initially on a mix of ethylene and JP‐7 jet fuel, then exclusively on JP‐7 jet fuel, the same fuel once carried by the SR‐71 Blackbird. The hypersonic demonstrator vehicle reached an altitude of about 70,000 feet and a peak speed of Mach 5.

The vehicle's fuel‐cooled engine, circulating 270 pounds of fuel serves both to heat the JP‐7 to an optimum combustion temperature and to help the engine itself endure extremely high operating temperatures during the long burn. Without such active cooling, the temperatures in the scramjet could reach 5,000°F, high enough to melt virtually any metal on Earth. Solving the cooling challenge is a major AFRL/Pratt & Whitney achievement.

The much anticipated hypersonic flight did not reach its maximum hypersonic speed and it flew autonomously for only 200 seconds before losing acceleration—its scramjet is designed for Mach 6 and burn for 300 seconds. But as stated by Joe Vogel, Boeing Director of Hypersonics and X‐51A Program Manager, "This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation."

The unmanned X‐51A WaveRider, powered by

the P&W Rocketdyne SJY61 scramjet engine,

is designed to ride on its own shockwave

The X‐51A WaveRider was launched

from beneath the wing of a B‐52

We must add that this achievement is also quite significant, as it is the first hypersonic flight by a hydrocarbon‐fueled scramjet.

Hydrogen‐fueled scramjets have achieved much higher speed. In fact, the previous record was set by NASA's X‐43A, when its hydrogen‐fueled scramjet engine burned for about 12 seconds in 2004; that experimental hyper‐vehicle zoomed to Mach 9.8. And as much as we like the clean burning of hydrogen, for some applications, such as fighter aircraft and missiles, hydrocarbon fuels are desired.

The successful flight of the first X‐51A demonstrated the viability of hypersonic vehicles. The advanced technologies in this program is bound to stimulate the development of hypersonic missiles and other military aircraft in the near future, platforms able to travel long distances quickly and close in on their targets so fast they would be almost impossible to defend against.

The X‐51A might also revive interest in hybrid turbo‐scramjet engines, propulsion concepts integrated into a new hypersonic vehicle that would not depend on a booster rocket to operate at the lower flight speeds. For example, it might be possible to get the scramjet to light up initially at speeds low enough to be integrated with a regular afterburning turbojet or with a detonation engine‐turbine hybrid rather than booster rockets.

Such approaches would widen the prospects for a number of applications including military jets and reusable spaceplanes. For example, a hypersonic jet fighter could take off from a runway and accelerate to scramjet ignition speed using an advanced jet engine, then switch into scramjet mode and rush forward into the hypersonic regime. This would essentially be a modern, hypersonic update of the incomparable SR‐71 turbo/ramjet spyplane, the famous Mach‐3.5 Blackbird.

The performance of a turbo‐scramjet could be further enhanced by the addition of a detonation combustion augmenter for the supersonic flight regime. This is because the efficiency of the jet engines that powers today’s military vehicles has approached its limit. But detonation combustion offers the needed performance improvement, resulting in a more efficient propulsion system that could extend vehicle range, cut fuel costs and reduce emissions. Engineers at GE Global Research, for example, have designed and built an eight‐combustor version of a pulse detonation engine (PDE) and integrated it with a conventional turbine. This development effort is needed to understand how to integrate a PDE in a real gas turbine engine.

Having an efficient detonation engine‐turbine‐scramjet, by integrating a rocket would allow a spaceplane to take off from a runway, gain the necessary speed and altitude still in the air‐breathing mode, and then make the final climb and acceleration to Mach‐25 orbital velocity in the rocket mode. This would result in a single‐stage to orbit spaceplane, one that would carry significantly less oxidizer than conventional two‐stage rockets.

Aerojet also made progress on advancing scramjet technology in 2010. Under contract with the U.S. Air Force Research Laboratory (AFRL), the company completed ground testing of a scramjet combustor, demonstrating a new thermal management technique. Called core burning, it forces the combustion flames away from engine surfaces, thereby reducing overall heat load. According to Aerojet’s patent by Melvin Bulman, with core burning “a pilot for a scramjet provides a flame front whose arrival at the wall of the scramjet combustor is delayed thereby reducing combustor heat load. By combining in‐stream injection of fuel with an interior pilot and a lean (fuel‐poor) outer annulus, the bulk of combustion is confined to the scramjet combustor center. One such pilot is for a two dimensional scramjet effective to propel a vehicle. This pilot includes a plurality of spaced apart struts separated by ducts and a strut pilot contained within each strut. A second such pilot is for an axisymmetric scramjet engine has, in sequence and in fluid communication, an air intake, an open bore scramjet isolator and a scramjet combustor.”

Aerojet’s engineers expect that core burning will require less fuel to cool the engine, enabling scramjets to have more thermal margin and to fly faster than with conventional thermal management. During the tests, the engine operated robustly at simulated Mach 3 to 5 flight conditions and at various simulated altitudes and fuel injection settings. An Air Force‐provided video camera recorded views of the combustion process clearly showing the flame holding and flame propagation processes occurring from the combustor center, thereby proving the core burning concept.

Aerojet’s core burning technology overcomes the long‐standing challenge of flight speed limiting thermal loads in the combustor. This thermal management technique will be crucial as the Air Force looks to progress from “laboratory” engine scales to those of operational sizes for long‐range, time‐critical missiles and high‐speed military aircraft.

In 2010 Pratt & Whitney Rocketdyne and Lockheed Martin also completed preliminary design of an actively cooled Dual Mode Ramjet combustor in support of the DARPA funded Mode Transition (MoTr) Demonstrator Program. This program seeks to ground test a turbine‐based combined‐cycle (TBCC) engine using hydrocarbon fuel. The MoTr program will demonstrate transition from turbojet to ramjet/scramjet cycle, the critical experiment required to enable reusable, air‐breathing, hypersonic flight. MoTr leverages previous and on‐going advances in air‐breathing propulsion technology, including the Falcon Combined‐cycle Engine Technology (FaCET) and the Air Force/DARPA High Speed Turbine Engine Technology Demonstration (HiSTED) program. The MoTr program will provide valuable risk reduction for future flight test program opportunities.

Aerojet’s Supersonic Sea‐Skimming Target ramjet propulsion system successfully completed the first flight test of the Coyote High Diver supersonic target mission. The target vehicle, developed by Orbital Sciences Corporation with Aerojet’s solid‐fueled Variable Flow Ducted Rocket (VFDR) engine, was rail‐launched from the ground and boosted by a rocket motor to ramjet‐takeover speed. Under ramjet power, the system ascended to 35,000 ft and reached Mach 3.3 cruise speed. At the end of its 110 nautical‐mile‐long flight, the vehicle executed a planned 40‐degree unpowered dive to its objective.

The international community pushed forward air breathing hypersonics as well. Leading countries such as Australia, Brazil, France, Japan, and Russia made significant contributions to advance several technologies. The following paragraphs provide highlights of the progress made by other nations in 2010.

BRAZILIAN INTEREST ON HIGHSPEED

AIR-BREATHING PROPULSION

The Institute for Advanced Studies (IEAv), a research center of the Brazilian Command of Aeronautics, is developing two advanced high‐speed air‐breathing propulsion technologies.

The IEAv’s Hypersonic Aerospace Vehicle, named 14‐X (after the 14‐Bis developed by aviation pioneer Alberto Santos Dumont), initiated in 2005, is the first Brazilian project with the objective to design, develop, construct and demonstrate a Mach 10 waverider in free flight with its required scramjet technology.

The Mach 10 waverider Hypersonic Vehicle model was experimentally investigated in Brazil’s T3 Hypersonic Shock Tunnel of the Prof. Henry T. Nagamatsu Laboratory of Aerothermodynamics and Hypersonics.

Brazil’s IEAv is also developing the Hypersonic Aerospace Vehicle, named DVPL (Vehicle Demonstrator of Laser Propulsion)

Brazil’s Hypersonic Aerospace Vehicle 14-X

Brazil’s Waverider Hypersonic Vehicle model installed

in the test section of the T3 Hypersonic Shock Tunnel



IEAv Prof. Henry T. Nagamatsu Laboratory of

Aerothermodynamics and Hypersonics

Hypersonic Aerospace Vehicle DVPL (left). 2-D laser

propulsion model installed in the test section of the T3

Hypersonic Shock Tunnel. Montage of the schlieren

frames (left to right) for Mach 10 hypersonic flow and 1

GW laser power (time between frames 10 μs)

Initiated in 2008 and in collaboration with the U.S. Air Force Office of Scientific Research’s, the DVPL is the first Brazil‐USA Laser Propulsion Experiment with the objective to design, develop, construct and demonstrate in free flight laser propulsion technology.

A 2‐D Mach number 10 Laser Propulsion Vehicle model designed and built by Prof. Leik N. Myrabo from Rensselaer Polytechnic Institute (Troy, NY), was experimentally investigated in the T3 Hypersonic Shock Tunnel (HST). Additional testing is expected in 2011.

HYPERSONICS PROGRESS IN FRANCE

France has a legacy of hypersonic air breathing propulsion system assessments and technology development dating back to the 1980s. In 2010, MBDA and the French National Aerospace Research Establishment (ONERA) pursued their R&T effort related to hypersonic air breathing propulsion mainly thanks to French State support but also with limited support from European Union.

MBDA and ONERA are to receive by the end of 2010, from French Administration, the contract covering all the remaining part of their flight testing program LEA. The goal of the LEA program is to establish, apply and validate a methodology for development of hypersonic air breathing vehicles. The LEA experimental vehicle should be flight tested in timeframe 2013‐2015 in the Mach number range 4 to 8 by using existing Russian supersonic bomber, liquid rocket booster and test range.

ONERA‐MBDA LEA Vehicle

The first test series have been achieved in the new METHYLE test facility providing capability to simulate up to Mach 7.5 flight conditions for large scale direct connected pipe test with test duration up to 1000s. In parallel, the upgrade of the ONERA S4Ma wind tunnel has been pursued to provide a large scale Mach 6 free jet test capability which will be used for LEA program in spring 2011.

Design activities were performed in the frame of the European LAPCAT2 studies related to high speed transport system. MBDA and ONERA contributed to the design challenge of a Mach 8 system.

HYPERSONICS ADVANCES IN JAPAN

JAXA (Japan Aerospace Exploration Agency) conducted RBCC model combustion experiments at Mach 11 conditions in the High Enthalpy Shock Tunnel (HIEST), following sea‐level static, Mach 4 and Mach 6 tests. The rocket engine in the RBCC produces most of the thrust, while the supersonic combustion engine assists in production of thrust. A detonation tube was used in the test to supply large amount of combustion gas as rocket exhaust in a short period.



Inside JAXA’s M11 experimental RBCC model.

It has two rocket nozzles, connecting to

a detonation tube by a pipe below

JAXA’s horizontal firing test of pre‐cooled turbojet engine

JAXA’s vertical firing test of pre‐cooled turbojet engine

Researchers at JAXA also plan a Mach 2 flight experiment of the hypersonic pre‐cooled turbojet engine model using a stratospheric balloon. Ground firing tests were already conducted with both horizontal and vertical attitude to evaluate the effect of gravity force in a free‐fall flight. The starting characteristics of the air‐intake were also obtained in a supersonic engine test facility.

RUSSIA HYPERSONICS SUCCESS

Successful tests of a large‐scale scramjet model‐demonstrator integrated with an airframe simulator of an experimental hypersonic flying vehicle (HFV) were run for the first time at the Central Institute of Aviation Motors, Russia, in April, 2010. The tests were conducted within the framework of the Federal Research Program (FRP) “National Technological Base” (NTB).

The demonstrator tests followed successful complex thermo‐gasdynamic studies of small scale integrated models of HFV “propulsion + airframe” and their components, as well as launching tests of a powerful high‐altitude hypersonic rig of 1.2 m nozzle diameter at the end of March, 2010 during its technical upgrading within the framework of FRP “NTB”. The exhauster machines of altitude‐compressor station provide for vacuum in the rig working section. A generator of high‐enthalpy air flow made within a state contract with the Rosnauka produces the required total working gas parameters appropriate to flight hypersonic speeds. The rig allows studying the working process in integrated experimental “engine + HFV” objects with simulation of hypersonic flight conditions.



Russia’s HFV Model

Tested rig model was displayed in the

International Aerospace Salon MAKS‐2009

SCRAMJETS/ROCKETPOWERED SPACE LAUNCHERS

Engineers at NASA KSC proposed a scramjet‐powered vehicle that can be rail‐launched all the way to orbit.

In the proposed 10‐year plan, a wedge‐shaped vehicle powered by a scramjet engine is launched horizontally along an electrified track, or gas powered sled, carrying a pod or spacecraft destined for low Earth orbit (LEO). The scramjet would fly the vehicle to Mach 10 to reach the upper edge of the atmosphere where a small rocket would fire off and propel the vehicle into orbit. The hypersonic craft would come back and land on a runway by the launch site.

The so called Advanced Space Launch System, comprised of railgun, scramjet, and rocket, was recently unveiled by Stan Starr, branch chief of the Applied Physics Laboratory at Kennedy in Florida. He indicated that the system counts on the availability of a number of existing technologies. His team is already working on a rail launcher using gas propulsion, and they are applying for funding under several areas, including NASA’s technology innovation, to develop and further mature the needed technologies. If successful, this new launch approach can revolutionize access to space.

There are some technical challenges to overcome first. According to the NASA team, to launch on an electrified track, for instance, the track would have to withstand at least 10 times the speeds commonly seen on tracks used for roller coasters. Roller coasters typically run about 60 mph (100 km/h).



Electrified rail assist to Mach 1.5

(NASA image courtesy of S. Starr, KSC)

Proposed NASA Launcher Configuration

(Ref. S. Starr, NASA KSC)

NASA is also investigating other methods of powering a track‐launched vehicle. Engineers with NASA’s Marshall Space Flight Center in Huntsville, AL, have already tested a prototype track‐based system that uses magnetic levitation to accelerate vehicles to launch speeds.

There are several studies underway to examine new launch architectures. The USAF, for example, is looking for architectures to eventually replace the existing EELV’s (Delta IV and Atlas V) which involve vertical rocket launch of a hypersonic stage. DARPA is studying scenarios that involve runway take off. All of these studies are based on the belief that practical scramjet propulsion is going to provide a design alternative in the 20‐year time frame so that reusable air breathing launch stages can be built and used routinely. The question seems to be, “what launch architecture optimizes the contribution by air breathing?” We know that the final stage into orbit has to be a rocket. We also know that the higher the initial velocity, the lower the mass of the air breathing propulsion system. For example an integrated vehicle taking off from a runway will require large low speed turbines in addition to high speed turbines, ram and scramjet engines (a lot of engines). According to Stars, if we can launch a vehicle from a rail with an initial velocity of Mach 0.5 we can decrease the size of the low speed turbines, but they are still required (although we do save propellant, wing mass, landing gear mass and other benefits). If we launch at Mach 1.5 we can launch with high speed turbines plus RAM/SCRAM. We also incur high dynamic pressures (increased structural mass) and environmental effects from sonic boom.

So Starr’s basic concept is to launch at a higher velocity than previous studies considered, thereby significantly simplifying the propulsion system and reducing weight. Of course those benefits must be weighed against a more complex total system (track) and the associated costs.

As for the scramjets, KSC engineers will draw from the experience gained through recent scramjet flight demonstration testing, including NASA’s X‐43A and the U.S. Air Force’s X‐51, both of which have shown that scramjets can achieve the required speeds for the proposed rail launcher.

Starr and his NASA KSC engineering team proposed a 10‐year plan that would begin with launching a drone similar to those used in the ongoing Air Force tests. More‐advanced models would then follow, with the goal of developing a vehicle that can launch a small satellite into orbit.

The proposed Advanced Space Launch System is not meant to replace NASA’s space shuttle fleet, which is schedule to retire next year, or any other manned spacecraft program, Starr said. But if this system is proven successful for unmanned launches, Starr believes that it could eventually be adapted to carry astronauts.

Finally we must add that not only do we need to advance hypersonic air breathing propulsion for hypersonic missiles, military superfast vehicles, and reusable Earth‐to‐space launchers, now we must work to develop vehicles that can move at hypersonic speeds in extraterrestrial planetary atmospheres.

In fact, NASA expects more research in this area and amended its announcement, “Research Opportunities in Aeronautics 2010,” to include new topics in support of the agency’s Hypersonics Project.

With the amendment, the Hypersonics Project of the Fundamental Aeronautics Program calls for proposals about enabling technologies and development of a new pool of expertise in two primary areas of interest. These include air‐breathing access to space and entry, descent and landing of high‐mass vehicles in planetary atmospheres.

LOOKING AHEAD

The complex requirements of faster vehicles will continue to demand advancements in hypersonic propulsion. The spectacular flight of the X‐51A waverider brought scramjet technology a major step closer to practical reality, getting farther into the future.

Acknowledgements

The author is grateful to the following people for providing information for this article:

Nancy Colaguori, Pratt & Whitney Rocketdyne

Tim O’Brien, Aerojet

Stan Starr, NASA KSC

Paulo Gilberto de Paula Toro, IEAv, Brazil

Takeshi Kanda, JAXA, Japan

Francois Falempin, MBDA, France

V. Vinogrodov, CIAM, Russia

More information about the activities of the AIAA High Speed Air Breathing Propulsion Technical Committee (HSABP TC) at https://info.aiaa.org/tac/PEG/HSABPTC/default.aspx

Source: Website of the American Institute of Aeronautics e Astronautics (AIAA) / (HSABP) Technical Committee

Comentário: Como o leitor pode notar o Brasil está na vanguarda do desenvolvimento da tecnologia de veículos hipersônicos. Entretanto, os nossos dois projetos precisam realizar seus vôos para que deixem de serem promessas e passem a ser algo real. Até então pelo que foi anunciado o 14-X tem seu vôo previsto para 2012 e o DVPL para 2014. Entretanto nossa experiência com o Programa Espacial Brasileiro nos faz duvidar desses prazos e o próprio 14-X é uma prova disto, já que inicialmente estava previsto para fazer seu vôo em 2010. Vamos aguardar. Gostaríamos de agradecer publicamente ao leitor do blog, Msc. Eng. Bruno Ferreira Porto, pesquisador do IEAv, por ter nos eviando este artigo.