High-alpha space trucks

Vertically-landing Reusable Launch Vehicles (RLVs) are the best hope of building a true ''Space Truck'' with current technology. Because they do not require a low angle-of-attack (AOA, or alpha) horizontal landing, they can be designed to operate exclusively at very high angles-of-attack. This offers savings in vehicle dry weight and complexity, which can be traded for significantly heavier payload, more ascent velocity, or extra design margin. The price for abandoning low angle-of-attack flight is reduced crossrange. To quantify the potential weight reduction, a trade study was performed to determine the relationship between a vehicle's maximum crossrange (angle-of-attack) and it's dry weight (payload margin). At the study conclusion, three vertically-landing (VL) vehicles provided multiple points on a payload weight vs. maximum crossrange curve, showing significant payload increases as crossrange is sacrificed. This is primarily the result of being able to simplify the structure, fly a cooler entry trajectory, and be aerodynamically stable through the entire flight. This reduces subsystem requirements and complexity, enhancing reliability. Further benefits are realized in reduced landing propellant requirements and simplifying or eliminating the ''rotation'' maneuver. This paper also suggests unique operability solutions that adapt high-alpha vehicles to traditional high-crossrange missions such as the polar ''once-around'' flight, and proposes a small scale drop-test program to prove the subsonic and landing portion of the flight envelope.