ATO # 96 - February 11, 2000
QuestChats require pre-registration. Unless otherwise noted, registration is at: http://quest.arc.nasa.gov/aero/chats/#chatting Wednesday, February 16, 2000, 1:00 PM Regimes of Flight Chat with Steve Smith Steve Smith is an aerospace research engineer who studies how airplanes will perform at different speeds. Right now he's researching supersonic flight and he uses computers, wind tunnels and is build his own plane. Read his bio at http://quest.nasa.gov/aero/team/smith.html Tuesday, February 22, 2000, 8 AM Pacific Women of NASA - Aerospace Team Online/National Engineers' Week QuestChat Forum with Fanny Zuniga Fanny Zuniga spends most of her time conducting experiments, evaluating the performance of wind tunnel test model aircraft, and studying data to help build better airplanes and space vehicles. Read her bio at http://quest.nasa.gov/aero/team/zuniga.html Thursday, March 2, 2000 10 AM - 11 AM Pacific Aerospace Team Online QuestChat with Earl Duque Earl Duque studies how air flows around, through, and under objects such as wings, propellers and aircraft vehicles. Read his biography at http://quest.nasa.gov/aero/team/duque.html Tuesday, March 7, 2000, 10-11AM Pacific Aesospace Team Online QuestChat with Brent Nowlin Brent Nowlin is responsible for making sure medium and large-scale gas turbine engines function Properly Read his biography at http://quest.nasa.gov/aero/team/nowlin.html
BLACK HISTORY MONTH CHAT SERIES
February is Black History Month. To celebrate, NASA Quest will host a series of QuestChats and forums with African American scientists and engineers who contribute their work in support of NASA's mission and goals. The schedule which may be added to over time can be found at http://quest.nasa.gov/qchats/special/mlk00/ Some of these are of special interest to Aerospace Team Online participants! Thursday, February 24, 2000, 9 AM Pacific Chat with Aprille Ericsson-Jackson, Ph.D., Aerospace Engineer Aprille works on guidance, navigation and control, and design analysis at Goddard Space Flight Center Read her bio at http://quest.nasa.gov/space/frontiers/ericsson.html
NEW CONTENT Sneak preview the "Regimes of Flight" a new resource for teachers and students about flight at different speeds. This will be targeted for grades 4-8. You will find background material, lesson plans, chats and contests!! For more information see http://quest.nasa.gov/aero/events/regimes - - - - - - CONTESTS Regimes of Flight Class Mural Contest, Grades 4-8 January 25 - March 2,2000 Choose one regime of flight: low, medium, high, supersonic, or hypersonic. Classes submit a mural that visually depicts not only the definition and description of the category, but also visually depicts aircraft from that category (Note: Key word "visually" means no words). For more information: go to http://quest.nasa.gov/aero/events/regimes/contest.html
[Editor's Note: Steve Smith is a research engineer. His bio is at http://quest.nasa.gov/aero/team/smith.html ]
Supersonic Wind Tunnel Testing For Performance of Next Generation Supersonic Transport
by Steve Smith
February 7, 2000
Over the past five years or so, NASA has been involved with Boeing Commercial Airplane Co. and McDonnell Douglas, Inc. (now part of Boeing), to develop the technologies to design a new supersonic transport. The Concorde jet is currently the world's only supersonic transport, and its operating costs are so high that it is not commercially viable. It is profitable only as a "luxury liner" with ticket prices too high for most people to be able to fly on it. If better aerodynamics could be combined with more efficient engines and lighter-weight structures, it may be possible to build a supersonic transport that would be profitable with ticket prices only slightly higher (maybe 10%) than current prices. In that case, many business travelers would be willing to pay the extra cost to reduce the time they spend traveling from the US to Europe and from the US to Asia.
One of the biggest challenges to building an economical supersonic transport is achieving low supersonic cruise drag. To study how well computer simulations can predict the supersonic cruise drag, a series of very careful wind tunnel tests were done on models that were also analyzed with computational fluid dynamics (CFD) simulations. These models were based on designs for a 300-passenger supersonic transport capable of flying from San Francisco to Hong Kong. To give you an idea of how important drag is for a supersonic transport, it was found that the added fuel needed to make up for a 0.5% (one-half percent!) error in drag prediction required the removal of 18 passengers to meet the same take-off weight limit.
The actual wind tunnel testing for drag is fairly simple. We try to hold test conditions very steady, including temperature. The electronic force balance can be very temperature sensitive. Ultimately, we even calibrated the balance at different temperatures so we could adjust the measurements for temperature variations. We take many measurements from each balance gage to average together to get the forces. We do several repeat runs to demonstrate the statistical repeatability of the data.
In addition to testing the basic design of the wing and body, different engine installations can have a big effect on the drag. Locating the engines carefully can cause favorable interference effects, where some of the drag on the engine is cancelled out by a reduction of drag on the wing in the presence of the engine. So many engine nacelle designs and positions can be studied. Another design feature that was tested are the leading and trailing edge flaps. Previous "test journals" by Mina Cappuccio and Fanny Zuniga describe some of those tests.
To give some idea of the kind of performance improvements that were achieved during the NASA-industry study, the Concorde jet has a lift-drag ratio of about 7.3 at Mach 2. The best designs from the recent NASA-industry study would have lift-drag ratios of about 9.0 at Mach 2.4.