X-37 Lands after 220 days in space

[Joe]

defense-update.com/wp/20101203_x-37b_landing.html

I'd forgotten about this.

[Tom Goodrick]

This brings back memories. The X-37 project was active when I was in NASA. I worked on vehicles like this but not directly on this project. NASA's role was to provide basic relevant technology to the Air Force but not to deal in the military aspects. My basic research involved external shapes for high lift and low drag with some stability in hypersonic flight which is the phase of entry into the atmosphere. From what I can see this has all the elements of the designs I produced. But that is not to say I had any direct input to this design. Most people working in the area would come up with similar designs. But it is a challenging technology because hypersonic aerodynamics is different from any other phase of flight.

The goal of hypersonic flight is to manage the trajectory for heat and for G loads until your vehicle ends up within 50 km of the target where it can go transonic at about 50,000 ft. For the returning Space Shuttle Orbiter, this phase begins over the western Pacific and ends over eastern Florida where a control problem during transonic flight would put the crash over the ocean. The problem is to dissipate the huge kinetic energy of orbital flight before transitioning to normal aerodynamic gliding flight.

I see one element of my design methodology that I passed on to the Air Force in the early 1990's. When I started on the design of hypersonic vehicles at NASA Marshall, I was supposed to use a manual graphic input tablet to devise 3D shapes for input to an aerodynamics program devised by the Air Force. Instead, I devised a set of math equations based on extended elliptical quadrants so I could control the shape by choosing just a few parameters. The process allowed making a curved corner on a rectangular section as a limit of the algebraic extension of the ellipse equation. When negotiating with the Air Force to get a new version of that old (1960's) aerodynamics program, I sent them some notes and an operating program that generated my shapes. I figured I owed them something for using their program. They turned around a few months later and gave us a new version of their program that had my equations embedded in the front end. They called it a "hyperelliptical design method."

The fun part of my job was making a 3D shape, taking that shape into the aero program and getting the aero coefficients and then putting those into my flight sim that took the shape from orbital flight to a landing on any selected runway in the US without breaking up or burning up. I "flew" the shape to a landing manually but with computed guidance cues.