Quiet Spike was a collaborative program between Gulfstream Aerospace and NASA's Dryden Flight Research Center to investigate the suppression of sonic booms. The patent was published with the United States Patent and Trademark Office in 2004 and is owned by Gulfstream Aerospace.
The program was intended to develop technology that may allow next generation supersonic transports to overfly populated areas at above Mach 1 (the speed of sound) without the high intensity of sonic boom that proved problematic for first generation supersonic transports such as Concorde (c.f. Operation Bongo).
The boom caused by Concorde generated substantial public opposition in the United States and eventually in other countries around the world. This opposition made it impossible for Concorde to be a commercial success.[ citation needed ] The sonic boom issue was also a significant factor in the eventual cancellation of the Boeing 2707. [1]
Shock waves develop around aircraft as they near Mach 1 (1225.0 km/h). 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 created at ground level is enough to rattle windows.
For example, the sonic boom from the Concorde traveling at a speed of Mach 2 (2450 km/h) was about 2.2 psf (0.11 kPa) (pound per square foot). [2]
Because of sonic boom intensity, many countries now prohibit supersonic overflight over land or population centres. The FAA prohibits supersonic flight over land, except in special military flight corridors. The Quiet Spike is able to suppress sonic booms somewhat, but a Quiet Spike alone is not effective enough to circumvent the current ban 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, 7.3 m (24 ft) long lance-like spike was mounted on the nose of NASA Dryden's F-15B research testbed aircraft. When in the 'fully retracted' position for take-offs and landings, the spike was 14.15 feet (4.31 m) long. When fully extended, the boom added two stages or states, to reach a total length of 24.31 feet (7.41 m). The Forward boom state was 5.9 feet (1.8 m) long and had the smallest diameter of the three, while the Mid-Boom State was 4.3 feet (1.3 m) long and the second largest in diameter. [3] The spike, made of composite materials, 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.
After the project's first flight on 10 August 2006, several more flights 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 project two years earlier.
Project milestones
On March 4, 2008, the NASA-Gulfstream Quiet Spike team was awarded the Aviation Week Laureate Award in the Aeronautics/Propulsion category. [4]
The Whitcomb area rule, named after NACA engineer Richard Whitcomb and also called the transonic area rule, is a design procedure used to reduce an aircraft's drag at transonic speeds which occur between about Mach 0.75 and 1.2. For supersonic speeds a different procedure called the supersonic area rule, developed by NACA aerodynamicist Robert Jones, is used.
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s. Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.
The Boeing 2707 was an American supersonic passenger airliner project during the 1960s. After winning a competition for a government-funded contract to build an American supersonic airliner, Boeing began development at its facilities in Seattle, Washington. The design emerged as a large aircraft with seating for 250 to 300 passengers and cruise speeds of approximately Mach 3. It was intended to be much larger and faster than competing supersonic transport (SST) designs such as Concorde.
A sonic boom is a sound associated with shock waves created when an object travels through the air faster than the speed of sound. Sonic booms generate enormous amounts of sound energy, sounding similar to an explosion or a thunderclap to the human ear.
A supersonic transport (SST) or a supersonic airliner is a civilian supersonic aircraft designed to transport passengers at speeds greater than the speed of sound. To date, the only SSTs to see regular service have been Concorde and the Tupolev Tu-144. The last passenger flight of the Tu-144 was in June 1978 and it was last flown in 1999 by NASA. Concorde's last commercial flight was in October 2003, with a November 26, 2003 ferry flight being its last airborne operation. Following the permanent cessation of flying by Concorde, there are no remaining SSTs in commercial service. Several companies have each proposed a supersonic business jet, which may bring supersonic transport back again.
Gulfstream Aerospace Corporation is an American aircraft company and a wholly owned subsidiary of General Dynamics. Gulfstream designs, develops, manufactures, markets, and services business jet aircraft. Gulfstream has produced more than 2,000 aircraft since 1958. Gulfstream's current range consists of the G280, G550, G500/G600, and G650/G650ER/G700/G800.
The NASA X-43 was an experimental unmanned hypersonic aircraft with multiple planned scale variations meant to test various aspects of hypersonic flight. It was part of the X-plane series and specifically of NASA's Hyper-X program developed in the late 1990s. It set several airspeed records for jet aircraft. The X-43 is the fastest jet-powered aircraft on record at approximately Mach 9.6.
Inlet cones are a component of some supersonic aircraft and missiles. They are primarily used on ramjets, such as the D-21 Tagboard and Lockheed X-7. Some turbojet aircraft including the Su-7, MiG-21, English Electric Lightning, and SR-71 also use an inlet cone.
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. The program was a joint effort between NASA's Langley Research Center, Dryden Flight Research Center at Edwards Air Force Base, California and Northrop Grumman.
A supersonic aircraft is an aircraft capable of supersonic flight, that is, flying faster than the speed of sound. Supersonic aircraft were developed in the second half of the twentieth century. Supersonic aircraft have been used for research and military purposes, but only two supersonic aircraft, the Tupolev Tu-144 and the Concorde, ever entered service for civil use as airliners. Fighter jets are the most common example of supersonic aircraft.
The Aerion SBJ was a supersonic business jet project designed by American firm Aerion Corporation. Unveiled in 2004, the designer sought a joint venture with a business aircraft manufacturer for a $1.2–1.4 billion development in 7–8 years. Aerion received 50 letters-of-intent before enlarging the design as the Aerion AS2 in 2014. Powered by two Pratt & Whitney JT8D-219 engines, the $80 million aircraft was to transport 8–12 passengers up to Mach 1.6 and up to 4,000 nmi (7,400 km).
A supersonic business jet (SSBJ) is a business jet travelling above the speed of sound: a supersonic aircraft. Some manufacturers are designing or have been designing SSBJs, but none are currently available. Usually intended to transport about ten passengers, proposed SSBJs would be about the same size as subsonic business jets.
The SAI Quiet Supersonic Transport (QSST) was a project by Supersonic Aerospace International (SAI) to develop a "virtually boomless" commercial supersonic business jet. The project was announced around the year 2000 and provided update announcements until 2010. After three years without any updates, the last update was in 2013. As of 2023, there have been no more updates, and the project appears to have been abandoned.
The Gulfstream X-54 is a proposed research and demonstration aircraft, under development in the United States by Gulfstream Aerospace for NASA, that is planned for use in sonic boom and supersonic transport research.
The Spike S-512 is a projected supersonic business jet, designed by Spike Aerospace, an American aerospace manufacturer firm based in Boston, Massachusetts.
The Aerion AS2 was a proposed supersonic business jet that was being developed by Aerion Corporation. In May 2014, it was announced that the Aerion AS2 would be part of a larger Aerion SBJ redesign, which aimed for release after a seven-year developmental period. Aerion partnered with Airbus in September the same year. In December 2017, Airbus was replaced by Lockheed Martin. Its General Electric Affinity engine was unveiled in October 2018. In February 2019, Boeing replaced Lockheed Martin. Development stopped when Aerion ceased operations in May 2021.
The Lockheed Martin X-59 Quesst, sometimes styled QueSST, is an American experimental supersonic aircraft being developed at Skunk Works for NASA's Low-Boom Flight Demonstrator project. Preliminary design started in February 2016, with the X-59 planned to begin flight testing in 2021. After delays, as of January 2024, it is planned to be delivered to NASA for flight testing in 2024. It is expected to cruise at Mach 1.42 at an altitude of 55,000 ft (16,800 m), creating a low 75 perceived Level decibel (PLdB) thump to evaluate supersonic transport acceptability.
Boom Technology, Inc. is an American company designing a supersonic airliner named the Boom Overture. The company is also developing a one-third-scale demonstrator: the Boom XB-1 Baby Boom.
The Boom Overture is a proposed Mach 1.7, 64–80 passenger supersonic airliner with 4,250 nmi of range, which is planned to be introduced in 2029 by Boom Technology. The company claims that with 500 viable routes, there could be a market for 1,000 supersonic airliners with business class fares. It had gathered 76 commitments by December 2017. The aircraft is planned to have a delta wing configuration, but will be built with composite materials. Following a redesign revealed in 2022 it is intended to be powered by four dry (non-afterburning) 35,000 lbf (160 kN) turbofans. Regulations for takeoff noise or overland boom can be met or changed.
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