Termination Shock

Once they’d all found places to stand, T.R. said, “This here upper part will be filled with hydrogen gas, which is the working fluid that actually pushes the shell up the barrel. The physics of it is beyond me, but they say that the maximum velocity of the projectile can’t be any faster than the speed of sound in the gas that is doing the pushing. The speed of sound in light gases like hydrogen and helium is higher than that in air. Enough to make a difference for our purposes. We looked at helium. The world’s helium supply actually comes from up Amarillo way. It’s safer, but it’s expensive and hard to work with. If you build one of these at the doorstep of Germany, Your Majesty, you’ll want to take a hard look at helium. I can help you get some.”

“Very considerate of you as always, T.R.!”

“Anyways, we settled on hydrogen. Some of it’s gonna leak out and burn, but it’s a desert, so who cares? It’s easy to make more, on-site, from natural gas. So, at the same time the methane-air mix is filling the chamber below, we fill this volume with a certain amount of H₂. When the combustion chamber”—he pointed straight down—“goes boom, this piston we’re standing on gets forced upward, compressing the hydrogen. Which only has one way out.” He drew their attention to the top of the cylinder, ten meters above their heads, where it tapered inward like an upside-down funnel to an orifice in the middle about the size of a manhole. If the entire cylinder was a bottle, that was its mouth. “Let’s see where it goes!” he suggested, touching off another round of extension cord wrangling, hatch closing, and ladder climbing that took them up above the top of the massive steel cylinder to Minus One.

If the lower levels had been straight twentieth-century tech with their spark plugs and pistons, Minus One was all modern robotics. Slightly below them was a massive construct that could only be the “mouth” of the “bottle”—the upside-down funnel that accepted and channeled the pulse of hydrogen gas being driven upward by the rising piston. A short distance above that were the bottoms of the six barrels, which were simply cut off at their bases, open to the room. In between those obvious and easy-to-understand elements was an elaborate, massive, rotating contraption that, if Saskia was any judge of these things, had consumed the lion’s share of the engineering resources. She couldn’t really puzzle it out until T.R. issued a command that caused a vertical conveyor system to go into motion. This thing—“Shell hoist” on the cross-sectional diagram—had run parallel to the elevator all the way down from ground level. It served a similar purpose to the lift, but it was smaller and it ran much faster. After it had been whirring along for a minute or so, it slowed.

A giant bullet descended into the room. The bullet was a bit longer than Saskia was tall, and somewhat fatter than a beer keg. It was machined aluminum in some places, carbon fiber in others. It had a Flying S logo and was stenciled “RETURN TO FLYING S RANCH - REWARD” in English and Spanish. It glided down past them on the hoist and was seized by a massive robot arm, which pulled it away, indexed around, and fed it point-first into the base of one of the gun barrels. Another mechanism, pushing up from below, then rammed the shell upward until it had completely disappeared into the barrel. Something went kerchunk. The robot arm retracted, but the shell did not fall out.

“Now, let’s say we want to send it on its way,” T.R. said. He nodded to a technician, who pressed some buttons.

The whole massive robotic platform went into motion, pirouetting around the central axis of the main shaft. Saskia couldn’t help thinking of the big cylinder in a cowboy’s revolver. It had a single large orifice in its top, offset to one side, matching the diameter of the gun barrels. When this was positioned below the breech of the barrel that had just been loaded, the whole thing rose upward in a swift, smooth movement until the connection was made.

“That’s how the hydrogen flows to the barrel,” Bob guessed.

“There’s now a direct unimpeded channel between the two,” T.R. confirmed. “If you were Spiderman you could go back down to Minus Four, into the same port we just used. You could climb up the cylinder wall, through that funnel we looked at, and up a short, oblique, snergly tube to where you could reach up into that barrel and touch the base of that shell we just now loaded.”

“And it’s all hot?” Saskia asked.

T.R. nodded. “Good point, Your Majesty. The shell was preheated above, and it’s still hot now—hot enough to keep the sulfur in its molten state. For as long as it sits in that barrel waiting to be fired, it will be kept hot by electrical heaters built into the barrel walls. The space on the other side of this window is quite warm—and it’s about to get warmer.”

“How many of those barrels are loaded?” Bob asked.