Quiet Spike
Encyclopedia
Gulfstream Aerospace
Gulfstream Aerospace Corporation is a producer of several models of jet aircraft. Gulfstream has been a unit of General Dynamics since 1999.The company has produced more than 1,500 aircraft for corporate, government, private, and military customers around the world...
and NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Dryden Flight Research Center
Dryden Flight Research Center
The Dryden Flight Research Center , located inside Edwards Air Force Base, is an aeronautical research center operated by NASA. On March 26, 1976 it was named in honor of the late Hugh L. Dryden, a prominent aeronautical engineer who at the time of his death in 1965 was NASA's deputy administrator...
to investigate the suppression of sonic boom
Sonic boom
A sonic boom is the sound associated with the shock waves created by an object traveling through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding much like an explosion...
s.
An eventual outcome of the project is to develop technology that may allow next generation supersonic transport
Supersonic transport
A supersonic transport is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. The only SSTs to see regular service to date have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 with its last ever...
s to overfly populated areas at above Mach 1
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...
without the high intensity of sonic boom that proved problematic for first generation supersonic transports such as Concorde
Concorde
Aérospatiale-BAC Concorde was a turbojet-powered supersonic passenger airliner, a supersonic transport . It was a product of an Anglo-French government treaty, combining the manufacturing efforts of Aérospatiale and the British Aircraft Corporation...
(c.f. Operation Bongo). Gulfstream has a particular interest in resolving this problem because of its desire to build a supersonic business jet
Supersonic business jet
A supersonic business jet would be a small business jet, intended to travel at speeds above Mach 1.0. Typically intended to transport about ten passengers, SSBJs are about the same size as traditional subsonic business jets...
.
The boom caused by Concorde generated substantial public opposition in the United States and eventually in other countries around the world under routes the aircraft was supposed to fly, and made it impossible for Concorde to be a commercial success. The issue of sonic boom was also a significant factor in the eventual cancellation of the Boeing 2707
Boeing 2707
The Boeing 2707 was developed as the first American supersonic transport . After winning a competition for a government-funded contract to build an American SST, Boeing began development at its facilities in Seattle, Washington...
.
Shock waves develop around aircraft as they near Mach 1. At ground level, these are perceived as a loud double boom or bang. Their intensity varies due to factors such as weather, refraction from different layers of atmospheric density, and size of the aircraft, but in general, from a supersonic aircraft of the size of a civilian airliner, the overpressure
Overpressure
The term Overpressure is applied to a pressure difference, relative to a "normal" or "ambient" pressure, in various circumstances:* In engineering: the pressure difference over the wall thickness of a pressure vessel...
created at ground level is enough to rattle windows.
For example, the sonic boom from the Concorde travelling at a speed of Mach 2 was about 2 pounds per square foot.
Because of sonic boom intensity, many countries now prohibit supersonic overflight over land or population centres. The FAA
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
prohibits supersonic flight over land, except in special military flight corridors. The Quiet Spike is a key enabling technology, but alone is not enough to reduce sonic booms sufficiently to lift the current prohibition on supersonic overflight.
Various structural approaches have been proposed to mitigate sonic booms, mainly focusing around changes to aircraft noses, the use of chines, changes in aircraft planform and even creating pathways through the aircraft structure to mitigate parasitic drag that leads to shock waves.
As part of the Quiet Spike project, a retractable, 24 feet (7.3 m) long lance-like spike has been mounted on the nose of NASA Dryden's F-15B
F-15 Eagle
The McDonnell Douglas F-15 Eagle is a twin-engine, all-weather tactical fighter designed by McDonnell Douglas to gain and maintain air superiority in aerial combat. It is considered among the most successful modern fighters with over 100 aerial combat victories with no losses in dogfights...
research testbed aircraft. The spike, made of composite material
Composite material
Composite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
s, creates three small shock waves that travel parallel to each other all the way to the ground, producing less noise than typical shock waves that build up at the front of supersonic jets.
Since the project's first flight, conducted on 10 August 2006, several more flights have put the system's structural integrity to the test before moving on to sonic boom suppression measurements.
The program concluded in February 2007, having completed over 50 flights, more than double those completed on the SSBD
Shaped Sonic Boom Demonstration
The NASA Shaped Sonic Boom Demonstration, also known as the Shaped Sonic Boom Experiment, was a two-year program that used a Northrop F-5E with a modified fuselage to demonstrate that the aircraft's shock wave, and accompanying sonic boom, can be shaped, and thereby reduced...
project only two years earlier.
Project Milestones
- First Flight - 10 August 2006
- First In-Flight Extension of the Quiet Spike - 25 September 2006
- First Supersonic Test Point - 20 October 2006
- Near Field Probing by 2nd F-15–13 December 2006
- Mach 1.8 Test Point - 19 January 2007
- Landing with Quiet Spike Extended - 19 January 2007
- Return to Savannah, GA for demod - 14 February 2007
On March 4, 2008, the NASA-Gulfstream Quiet Spike team was awarded the Aviation Week Laureate Award in the Aeronautics/Propulsion category.