“Proceed, Hupla, with the intelligence that prompted your rather rude entrance.”

“But—”

“Hupla…” Puffing masterful clouds of cigar smoke.

“It-it’s about the shape of the tunnels here, Master.”

“Don’t flinch like that. I based that design on the double lightning-stroke, Hupla—the SS emblem.”

“But it’s also a double integral sign! Did you know that?”

“Ah. Yes: Summe, Summe, as Leibniz said. Well, isn’t that—”

BLAM.

All right. But Etzel Ölsch’s genius was to be fatally receptive to imagery associated with the Rocket. In the static space of the architect, he might’ve used a double integral now and then, early in his career, to find volumes under surfaces whose equations were known—masses, moments, centers of gravity. But it’s been years since he’s had to do with anything that basic. Most of his calculating these days is with marks and pfennigs, not functions of idealistic r and θ, naïve x and y… . But in the dynamic space of the living Rocket, the double integral has a different meaning. To integrate here is to operate on a rate of change so that time falls away: change is stilled… . “Meters per second” will integrate to “meters.” The moving vehicle is frozen, in space, to become architecture, and timeless. It was never launched. It will never fall.

In the guidance, this is what happened: a little pendulum was kept centered by a magnetic field. During launch, pulling gs, the pendulum would swing aft, off center. It had a coil attached to it. When the coil moved through the magnetic field, electric current flowed in the coil. As the pendulum was pushed off center by the acceleration of launch, current would flow—the more acceleration, the more flow. So the Rocket, on its own side of the flight, sensed acceleration first. Men, tracking it, sensed position or distance first. To get to distance from acceleration, the Rocket had to integrate twice—needed a moving coil, transformers, electrolytic cell, bridge of diodes, one tetrode (an extra grid to screen away capacitive coupling inside the tube), an elaborate dance of design precautions to get to what human eyes saw first of all—the distance along the flight path.

There was that backward symmetry again, one that Pointsman missed, but Katje didn’t. “A life of its own,” she said. Slothrop remembers her reluctant smile, the Mediterranean afternoon, the peeling twist of a eucalyptus trunk, the same pink, in that weakening light, as the American officer’s trousers Slothrop wore once upon a time, and the acid, the pungent smell of the leaves… . The current, flowing in the coil, passed a Wheatstone bridge and charged up a capacitor. The charge was the time integral of the current flowing in the coil and bridge. Advanced versions of this so-called “IG” guidance integrated twice, so that the charge gathering on one side of the capacitor grew directly as the distance the Rocket had traveled. Before launch, the other side of the cell had been charged up to a level representing the distance to a particular point out in space. Brennschluss exactly here would make the Rocket go on to hit 1000 yards east of Waterloo Station. At the instant the charge (B_iL) accumulating in flight equaled the preset charge (A_iL) on the other side, the capacitor discharged. A switch closed, fuel cut off, burning ended. The Rocket was on its own.