Saskia and others followed as T.R. led the reporter out of the Beer Car and across a few meters of open ground to a flat area where another one of those ubiquitous pop-up sun canopies had been pitched. Beneath it, a giant bullet rested on a display stand. T.R. shooed a white hat out of the way in mid demo. "Most of the shell is hollow. Empty space. It’s a container for sulfur," he said. "That being the entire point." He patted its base, which was flat. "This here is just a sabot for the hydrogen to push against while it’s in the gun barrel. It falls off immediately and we retrieve it." He yanked the sabot off and chucked it on the ground. Revealed was a conical hole penetrating into the middle of the shell. "The nozzle bell where combusted sulfur dioxide shoots out of the combustion chamber." He walked around to the pointed nose of the bullet, and simply yanked it off. "Another disposable part. Falls off in the stratosphere, comes down like a badminton birdie. We find it and reuse it. Or not." Revealed under the nose cone was another tapering hole, like the intake of a jet engine. "Where the air comes in." He stepped back. By the removal of the sabot and the nose cone, the bullet had been transformed into a jet engine. "Now it can generate thrust by exhausting sulfur dioxide, which has the interesting side effect of saving millions of lives and trillions of dollars from the effects of global climate change. But from a strictly aerospace engineering point of view we have a problem, which is that it can’t generate nearly enough thrust to stay aloft for long." He opened a hatch on the top of the shell to reveal a shallow but broad compartment just underneath, wrapping partway around the upper part of the shell’s cylindrical body. It was full of orange fabric. "This is too unwieldy to display here, so here’s a picture of what it looks like when it’s deployed." He gestured toward a poster, mounted on a slab of foam core zip-tied to the canopy’s frame. It depicted one of those parasailing wings often seen towed behind speedboats in seaside resorts: a curved leading edge, a wing of taut fabric behind it, and a system of shroud lines converging on, and supporting, the payload. "This object deploys and gives it some appreciable L over D," T.R. said, "which means it can stay aloft for a little while through a combination of running the engine and shedding altitude. The more sulfur it burns, the lighter it becomes. The farther it descends, the thicker the air. Both work in our favor. By the time the tank is empty, this thing is pretty damned airworthy and it can glide for a long ways. Even if it’s out over Mexico somewhere it can glide back and try to hit one of those nets."