History of lifting body aerodynamics
 

Martin X-24A, Northrop M2-F3 and Northrop HL-10 lifting body aircraft The wingless, lifting body aircraft sitting on Rogers Dry Lake at what is now NASA's Dryden Flight Research Center, Edwards, California, from left to right are the X-24A, M2-F3 and the HL-10.The lifting body aircraft studied the feasibility of maneuvering and landing an aerodynamic craft designed for reentry from space. These lifting bodies were air launched by a B-52 mother ship, then flew powered by their own rocket engines before making an unpowered approach and landing. They helped validate the concept that a space shuttle could make accurate landings without power.  The HyperTryke lifting body landyacht references: 'Fundamentals of Vehicle Dynamics' by D.T. Gillespie 'Theory of Wing Sections' by I.H. Abbottt and A.E. Von Doenhoff A lifting body landyacht can be thought of as being driven by a small, low aspect ratio fixed sail or wing. According to Abbottt and Von Doenhoff, low aspect ratio wings will produce lift over a very broad range of attack angle before stalling. The HyperTryke sails by steering a heading at which the aerodynamic forces on the body of the yacht balance or exceed wheel drag. With a wing/body area of only 30 square feet in base configuration, a 25+ mph wind is required for maximum fun. The sailor sits inside the wing/body, an NACA 0033 symmetrical airfoil section. Motorcycle type handlebars control the rear wheel steering mechanism. The floor under the sailor's feet is open. This opening serves as the entrance to the yacht. It also lets the sailor push-off or carry the 70 lb yacht out of sand drifts, etc.

HyperTryke Trainer A java applet that simulates the forces acting on a lifting body landyacht Disclaimer: This program is for informational purposes only and is not terribly amusing. Run applet here View Java source code Left side of display:  velocity of the vehicle, true wind and apparent wind (color code in upper left corner of window) angle of attack side force acceleration (forward thrust or driving force) Right side of display:  top view of the yacht true wind, apparent wind, true course and slip angle angle in degrees (color code in upper left corner of window) 'dust trails' for a visual clue to yacht speed Drag an arrow pointer for true wind speed, true course, vehicle weight and vehicle slip angle ratio or click on a number value to set these parameter. To sail, the sailor moves the landyacht's true heading arrow pointer to the desired heading. Angle of attack must be kept below stall angle (about 33 degrees) and side force below 0.8 G's (80% of vehicle weight) while keeping the acceleration gage needle green, in the positive region. Then it's smooth sailing! Controling the variables: true wind speed, vehicle weight and slip angle ratio   Three variables enable the program user to investigate yacht performance with different wind conditions, sailor weight (or added ballast), sailing surface (hard packed beach sand, dry lake or pavment) and tire type. true wind speed default: 30 mph vehicle weight default: 270 lbs slip angle ratio default: 0.08 lbs/lbs/deg true wind speed As true wind speed increases, at certain headings vehicle performance decreases due to side slipping with a pronounced dip at 35 mph wind speed, 70 degrees up-wind heading. Maxumim vehicle speed, 80+ mph, occurs at 35 degrees down-wind heading. vehicle weight By increasing vehicle weight, across-wind vehicle performance increases due to reduction in side slipping. Maxumim vehicle speed, 80+ mph, occurs at 55 degrees down-wind heading. slip angle ratio An increase in slip angle ratio results in a reduced vehicle rolling resistance at any heading. The greatest gains are up-wind and down-wind performance. Maxumim vehicle speed, 100 mph, occurs at 35 degrees down-wind heading. More about slip angle ratio (also known as cornering coefficient) and tire rolling resistance A cruising landyacht creates a large side force, approaching 70% or more of the vehicle's weight. Quoting Gillespie from 'Fundamentals of Vehicle Dynamics' , "When a rolling pneumatic tire is subject to a lateral (side) force, the tire will drift to the side. An angle will be created between the direction of tire heading and the direction of travel. This angle is known as the slip angle... At a few degrees of slip, equivalent to moderate-high cornering accelerations (the slip angle of a cruising landyacht), the rolling resistance coefficient may more then double in magnitude." Vertical load on the tire, tire type and ground surface conditions will affect the slip angle. The slip angle ratio variable usage: slip angle degrees = side force lbs / vertical load lbs / slip angle ratio A typical bias-ply passanger car tire on asphalt has a slip angle ratio value of aproxametly 0.10, or: 0.10 lb side force per 1.0 lb load per degree. Radial-ply tires have a value of about 0.15, while high performance tires can be 0.30 and greater. The higher the value the better. Calculating slip angle and tire rolling resistance tire rolling resistance = sin(slip angle) * side force + rolling resistance coefficient x vehicle weight Basic tire drag, no side force .01 rolling resistance coefficient x 270 lbs vehicle weight = 2.7 lbs rolling resistance slip angle ratio = 0.10, side force = 0.7 G 189 lbs side force with 270 lbs vertical load will produce a 7degree slip angle 189 / 270 / 0.10 = 7 sin(7) x 189 + .01 x 270 = 25.73 lbs rolling resistance slip angle ratio = 0.20, side force = 0.7 G 189 lbs side force with 270 lbs vertical load will produce a 3.5 degree slip angle 189 / 270 / 0.20 = 3.5 sin(3.5) x 189 + .01 x 270 = 14.23 lbs rolling resistance The program has a adjustable slip angle ratio range from 0.03 to 0.30. The default slip angle ratio for HyperTryke Trainer is 0.08, a reasonable value for a good beach tire on hard-packed sand.  Construction Details Beyond HyperTryke lifting body - the flying wing Northrop XB-49 Flying Wing and Northrop B-2 Stealth Bomber The flying wing was a natural outgrowth of John K. "Jack" Northrop’s lifelong concern for an aerodynamically clean design in which all unnecessary drag caused by protruding engine nacelles, fuselage, and vertical and horizontal tail surfaces would be eliminated. The minimum parasite drag coefficient for a flying wing is approximately half that of conventional aircraft. Minimum drag coefficients for conventional aircraft average approximately .023. The minimum drag coefficients for flying wing aircraft have been measured both in model and full-scale configurations and vary from less than .010 to about .0113. HyperTryke flying wing configuration performance data   true wind speed range:14 to 22 mph vehicle weight: 290 lbs slip angle ratio: 0.20 wing area: 55 square feet effective wing aspect ratio: 5 high performance tires on dry lake In flying wing configuration, data indicates that speeds of up to 70 mph in a 14 mph wind may be possible in ideal conditions.