How refreshing, Carrera thought. He loathed briefings, meetings, and all the rest of the modern world's bureaucratic time-sinks. Refreshments tended to make it worse, not better, since they invited people to stay too long and talk too much. On occasion, Carrera thought of enacting a regulation requiring all meetings and briefings in the Legion to be conducted standing and in the rain.
Pislowski smiled, pointing a finger. "It was that bloody Volgan's idea."
The Volgan—his given name was Pyotr –smiled back. He then picked up one of the models, a strangely proportioned aircraft. "As my friend has said, it was my idea. Technically. Better to say I was the one who pulled together some things I'd seen and read over the years. Some of that came from Jagielonia. This is a glider we've nicknamed the Condor."
"They build many gliders in Jagielonia,' Pyotr continued. "Their interest goes back many decades. Even when I was doing design work for the Volgan Empire, it occurred to me that a glider has many advantages over an aircraft, even for combat purposes. It is fuel efficient. It is easy and cheap to maintain, even if it has an engine, as some do. It is quite easy and cheap to train people to fly a glider. Because a glider is so cheap and easy to fly, there is no great reason to require that the highest caliber men be chosen as pilots. Ground support requirements are only a tiny fraction of what is needed for a high performance aircraft. A glider is also relatively difficult to pick up on radar."
"Still there are disadvantages," Pyotr admitted. "A glider cannot carry much of a load. It is slow and not very maneuverable. It must be raised to a considerable height by some means, most commonly another aircraft. It depends upon natural updrafts in the air to keep going. With an auxiliary engine many of these disadvantages can be at least partially overcome. But with an engine, the glider becomes much easier to acquire, either on radar or by infrared from the heat of the engine and exhaust. Georgi and I have an answer to that."
Georgi, the senior of the two Volgan designers, spoke up. "Sir, do you know anything about radar?"
Carrera answered, "Assume not."
"Yes, sir. Radar is microwave energy, traveling through the air. It can also travel through other things, ground and water, for example, but with less range and accuracy. When the energy reaches something with a density different from air, it reacts. In effect, it radiates back from whatever it hit that was different from air, if the material it hits is capable of radiating back. Some materials radiate back poorly or not at all. These change the microwave energy into heat. Is the Duque familiar with the Federated States Air Force's P-71?"
"I know of it as a name. I've seen pictures."
"Here's a picture you didn't see," Georgi said, handing over an eight-by-ten black and white of a remarkably odd-looking aircraft.
Carrera took it and looked at it carefully. He asked, "What's that dark ring around it?"
"Bats," Georgi answered. "Hundreds and thousands of stunned, crippled or dead bats. They couldn't see the plane and flew into it, usually killing themselves. You see, bats use sonar which is, in some ways, similar to radar. The P-71 presented no surfaces to bounce back the sonar signals to the bats. So they couldn't 'see' it and flew into the plane. The P-71 presents a very small radar, or sonar, cross section. Too small for bats to see."
Pyotr took up the briefing, once again. "There are three primary factors that affect an aircraft's radar cross section. These are size, materials, and shape. Although it is the least important factor, if two aircraft have exactly the same materials and shape, but are of different size, the larger will have a greater radar cross section. These gliders will be quite small. For shape, the important things are to have no sharp edges, no flat surfaces pointed toward the radar. For materials, there are two . . . oh, tricks, that we can use. The first is, construction wise, the tougher. Radar notices the change in density of an object in the air. To the extent that that difference is tiny, radar is apt not to notice. We plan to build gliders based on a spun carbon monofilament and resin shell. The shell itself can be made 'lossy'—"
"Glossy?" Carrera interrupted.
"No, sir. Lossy. It's a chemical property that refers to the conductivity of a material. Simply put, we can make the shell to absorb much radar energy and convert it to heat."
Carrera sat up. "Won't that give the glider away?"
"No, sir. The radar energy is small so the amount of heat produced in the shell is quite small and the polyurethane outside of it is almost the best insulator known. A plane might pick up the heat; a missile will not lock on very well."
"But we were discussing radar. By itself, the lossiness of the carbon monofilament is not enough. So outside of that, we shall build up polyurethane foam of decreasing density. The 'dielectric constant' of the outermost polyurethane will be—"
Interrupting, Carrera asked "Dielectric constant?"
Pyotr reminded himself that he was dealing with a soldier, not a scientist. "Air has a dielectric constant of 1. The outermost polyurethane will have a DC of 1.01, near enough. At that difference, only an immeasurable amount of radar energy will radiate back. Not enough for a receiver to notice. As the radar penetrates the polyurethane, each increasingly dense layer will also radiate back a small amount; again, not enough to notice."
"The polyurethane itself will be reinforced by carbon fibers in the mix, which tend also to absorb radar energy. Inside it will be suspended a great many tiny metalicized chips. The chips will be curved to disperse radar energy outward on one side, or focus, and then disperse it, on the other."
Seeing Carrera's lack of comprehension, Pyotr explained. "The mix being sprayed on, the chips will be in random positions within the polyurethane. In almost all cases radar which hits them will be bounced away from the radar source. For those chips—and remember; they'll be tiny—that point directly toward the source, the radar will hit the convex or concave curves and be scattered so only a small portion of the energy is returned. These chips will also decrease in size as they near the outer surface. Where the P-71 has precisely calculated facets to insure the smallest possible surface pointed toward a radar, we will let random nature do much the same thing for us. Being random, it is possible that more than a desirable number of chips may reflect in the same direction. But the mathematical odds are plainly on our side. We can ground test each glider for particularly vulnerable areas, and use those with unsatisfactory chip alignment as something like a throw-away cruise missile, or as drones on recon missions. I believe you mentioned an interest in throwaways?"
"Yes." Carrera gestured for the Volgan to continue.
Pyotr nodded vigorously. "However, we cannot count on the plastics - the polyurethane and the carbon monofilament - to completely defeat the radar. Even the chips will only do so much. Inside the glider will be several objects that could give back quite a large radar cross section. The engine and the control package are problems. Even the pilot's skull will give back some radar energy. We plan on encasing the engine and control package in small, faceted, flattened domes of highly lossy material. These are much cheaper and easier to design and build than a full airframe like the P-71. They will reflect radar either down or straight up, and away from the radar source. The pilot, too, will be similarly covered although only on five sides, plus a partial—he has to see, after all."
"We have still to determine the best materials and composition for the propeller and wings. We might even go to a small jet engine. Likewise, we are arguing about the pilot's canopy. Neither of these problems appears insurmountable. For a guidance package for use as a drone we think it is possible to use a fairly simple computer and cheap, civilian model, global locating system. We would have to subcontract that out, however."