A version of this article appears in the May 5 edition of Aviation Week & Space Technology.
A cockpit display allowing pilots to steer sonic booms away from noise-sensitive areas is expected to play a key role in securing regulatory approval for low-boom supersonic flight over land.has the software, now it wants someone to develop the display. The contract is one of several to be awarded as continues to prepare for a hoped-for flight demonstrator that would allow the agency to collect data on community response to low booms. This information is needed to persuade regulatory authorities to lift the ban on civil supersonic flight over land.
That NASA can predict sonic boom impact in real time shows how far it has come with its design tools, but its research plan to 2017 also suggests the agency is essentially marking time until it can build a demonstrator. Having cracked the code for low-boom supersonic flight, proving that the public can accept an aircraft designed with those tools is the crucial next step.
Although NASA has shown that carefully shaped aircraft can have significantly reduced shockwave signatures, crews will still have to keep track of where a boom reaches the ground—particularly the powerful, focused ones generated when accelerating or maneuvering. Planning, monitoring and adjusting the path of the sonic-boom carpet laid under the aircraft will be an important part of flying supersonically.
NASA has developed software, called CISBoomDA (for Cockpit Interactive Sonic Boom Display Avionics), that calculates current and projected boom impact areas (see graphic). The software is used for planning and monitoring supersonic flights in the control room at NASA Armstrong Flight Research Center (the former NASA Dryden). CISBoomDA could be used in the air to predict and monitor sonic-boom impact in flight, and on the ground to enable air traffic control to approve and monitor supersonic flights, says Ed Haering, technical lead for supersonic aerodynamic research at NASA Armstrong.
The program takes flight data, terrain-elevation information and atmospheric measurements and calculates shockwave location and intensity on the ground. NASA plans to flight-test the software this year in a.
The agency also has solicited proposals to develop and validate in flight a sonic-boom cockpit display using the software. This would take a candidate maneuver trajectory and display the ground impact area and intensity to the pilot. If the boom is acceptable, the display would guide the pilot through the maneuver. If not, the system would enable the pilot to plan a trajectory that would produce an acceptable boom.
NASA plans to award a 2-3-year contract, funded at up to $350,000 per year, to raise the technology readiness of the sonic boom cockpit display by investigating integration into current business jet-class avionics, demonstrating it in flight and incorporating feedback from commercial pilots.
The display is a key part of a research plan for 2013-17 under which work continues toward laying the groundwork for a flight demonstrator. The plan includes the funding for further development of tools to design a small supersonic transport aircraft with a sonic-boom noise level of less than 80 PLdB, compared with 105 PLdB for the Concorde.
In the absence of funding for a demonstrator, which was sought in fiscal 2015 but was not included in NASA’s budget request, the agency will also fund more work on low-noise technologies to enable low-boom aircraft to achieve airport noise levels 10 EPNdB below Chapter 14 limits. These take effect for new large civil airliners in 2017, and by the time any supersonic transport enters service, it will have to come in well under those lowered limits to be on a par with subsonic commercial aircraft.
The agency also plans to fund risk-reduction work to prepare for public testing of a low-boom flight demonstrator. This will cover the creation of a conceptual plan for a community response test, identifying risks and addressing high-priority areas through additional research.
As a guide, NASA’s solicitation describes the hoped-for demonstrator as a manned aircraft capable of day and night flight and designed to cruise at around Mach 1.6 and 50,000 ft., aiming for an optimal sonic boom level of around 75 PLdB under the aircraft’s track and 70-75 PLdB off-track.
For now, such an aircraft remains a dream. But NASA is not yet prepared to put its plans for low-boom supersonic transports on the shelf. Continued homework such as the sonic-boom display project will keep the concept moving forward as it works to build support for a demonstrator.