From Secret Projects, regarding Scaled Composites SOFTA (Special Ops Forces Transport Aircraft)
https://www.secretprojects.co.uk/forum/index.php/topic,20555.15.htmlMODEL 215 SKIRT TANDEM SUPERSTOL
Tandem wing, skirt for Super-STOL, rocket assist
Model 215 is a conventional tandem wing configuration for cruise that is optimized for a high cruise L/D using high aspect ratio sailplane-like wings. The aft wing outer panels can be hinged similar to Model 208 for pitch and roll control during cruise. As shown in the section view, the entire fuselage between the canard and main wing contains a drum in which a sail-like “skirt” is rolled up and stowed for cruise. Where runway length allows, the aircraft makes conventional takeoffs and landings without the skirt high lift device. For SuperSTOL operations, the aircraft is slowed to near the stall speed, then is continuously slowed as the skirt is unfurled laterally between the canard and wing. The skirt edges are retained in tracks similar to that used on high performance racing sail boats using a continuous root-to-tip cable loop at the canard and the wing. This geometry transition results in a three-fold increase in aircraft wing area and a significant reduction in aspect ratio, allowing a steep, slow descent into the landing zone using conventional fixed wing aerodynamics. In this configuration, the aircraft is actually a cross between a rigid conventional transport and a rag-wing type ultralight aircraft. When the aircraft is in the flare several feet in the air before touchdown, rocket engines are fired facing forward at the nose. A rocket burn of approximately 2.5 seconds provides a 1.0 G deceleration and reduces the speed to 35 knots within a 75-foot ground roll. Wheel brakes are used for the remaining 50 foot ground roll, providing a total ground distance of 125 feet. Thus, the several minute noise signature of the conventional vertical landing craft is replaced by a very loud 2.5 second “What was that?” type of signature. For takeoff, aft-facing rockets provide acceleration in addition to the turbofan engines and the landing transition is reversed. Total rocket fuel, using a specific impulse of 200 seconds results in a fuel weight of approximately 850 pounds, an excellent tradeoff compared to most vertical landing systems. The rockets are used, of course, only when SuperSTOL performance is mandatory.
