With a $10 million research grant from NASA and the U.S. Air force, a future hypersonic aircraft may one day take flight and Buffalo has something to do with that.
UB is one of ten universities, national labs, and industry team members that include Cornell, Michigan State, George Washington, University of Virginia , University of Pittsburgh, Los Alamos, NC State, Stanford University, and The Boeing Company, led by the National Center for Hypersonic Combined Cycle Propulsion at the University of Virginia, to embark on a new transportation initiative. The Center’s mission is to design analytical, numerical and experimental tools necessary to successfully develop a new propulsion system for hypersonic aircrafts that would change space flight and aviation as we know it today.
The journey to the stars has been a dream of mankind for ages and people have wanted to fly since the first thinking humans appeared on the planet. The desires for space flight and aviation have been met, yes – however, have not been completely and optimally realized. The goal now is to fly faster, safer and more efficient. Ultimately, orbital flights will be attainable to everyone and not only to a selected group of people.
All that may be accomplished in approximately twenty years from now with a two stage to orbit vehicle, capable of flying at hypersonic speeds, greater than five times the speed of sound, as depicted in Figure 1. At an altitude of about 80 km (about 50 miles) the second stage would separate from the first and continue to accelerate by using conventional rocket propulsion until it reaches orbital speed. The first stage would then return to an airport. Such a re-usable aircraft would be able to take off and land controlled, on any runway on the earth, unlike the presently used space shuttle, which is only able to glide back to specific landing sites. Not only would this new two-stage vehicle be used for space travel, its first stage could also be used as a civil aircraft.
The hypersonic aircraft uses a Supersonic Combustion Ramjet, a so-called scramjet engine. This propulsion system uses the surrounding air as oxidizer, which characterizes it as air breathing engine. The primary benefit relative to traditional rockets is that the air breather does not have to carry its oxidizer on board. “This provides a potential payload fraction advantage, which means that the take-off mass is reduced quite drastically. Relative to a rocket, however, the hypersonic air breather will be a much more complex system, considering the external physics of high-speed aerothermodynamics and the complex propulsion flow path physics,” says Professor Madnia.
How does a scramjet engine work? The ambient air is compressed by shocks produced by the lower vehicle body and by the engine intake. If the air inside the engine is at the right pressure and temperature, fuel (e.g. hydrogen) is injected, mixes and combusts with the air within milliseconds and the products (water vapor) expands through the nozzle. This aerodynamic mechanism then produces hypersonic thrust. The big challenge is to keep the thrust stable, to keep the engine working. “It’s like holding a torch in the middle of a storm and keeping it from going out.” adds Andreas Hoffie.
Professor Cyrus Madnia, with a PhD in aerospace engineering and his group of three at UB including Andreas Hoffie and Navid Samadi Vaghefi both Ph.D. students, heads up an aspect of hypersonic research. For the next five years, UB will be the premier place for Direct Numerical Simulation (DNS) of High Speed Turbulent Reacting Flows.
The hypersonic aircraft may not take flight for another twenty years; however, if we take into account the hundreds of years it took our predecessors before the Wright brothers flew the first propelled airplane in 1903, it’s not such a long wait after all.
Figure 1: US Vision of a future, fully reusable space transportation
system. The first stage is a hypersonic aircraft that uses air
breathing scramjet propulsion. The second stage uses conventional
rocket propulsion in order to achieve orbital velocities.
Figure 2 shows a NASA/USAF design for the next generation of hypersonic aircrafts.
A series of hypersonic flight tests are necessary to test the scramjet
engine and structural performance of such aircrafts under real flight
conditions (see Figure 2).