“So, Donny,” White said. “That damn thing going to light on schedule?”

White was expecting the usual confident good-guy bull back from Baylor, and he was surprised when Baylor didn’t respond in kind. Instead Baylor glanced at him, evidently troubled, despite that big mask of his sunglasses. “I’ll tell you the truth, Marcus,” he said. “We got ourselves one hell of a beast out there.”

“You don’t sound too confident.”

“I’m not. Christ, Marcus, it’s been like archaeology. We had to tear down one of the old flight spares for the component evaluation, and to get some experience of assembly and checkout. We had to buy fresh tooling and checkout equipment, and activate the old turbopump checkout facility. We had to adapt the thrust chamber assembly equipment we use for Shuttle main engine production. Only about half of the old suppliers are still in business, so we had to find new approved suppliers, for the heat exchanger duct assembly, the lox mating ring, the fuel pump housing, the pump housing machining… A dozen things. Some of the tools we needed we had to make. We had to redraw the tooling drawings, rework all the process and material specifications; they weren’t compatible with the manufacturing processes we use now…

“I’ll tell you what’s really screwing us, though. Instability in the combustion chamber. See, the pumps bring the lox and kerosene to the injector plate. That’s a metal slab, a disc a yard across and four inches duck. The point is to get a nice smooth flame front, where the propellants burn at a uniform temperature, right across the face of the injector plate, all three feet of it…” Baylor started going into a lot of detail about how the lox and kerosene were brought into the chamber as fans, which impinged on each other. Pre-burners ignited the propellants at those points of impingement. Baylor mimed the little fans of lox and kerosene with his engineer’s hands, his gnarly fingers splayed out, as brown and hard as wood carvings.

“And if you don’t get a smooth flame front,” Baylor said now, “you’re fucked. Suppose one side of the plate has a slightly higher oxygen content than the other. Then that area will get hotter, and produce higher pressures on that side. Then, in an engine the size of the F-1, you get a racetrack, where you have a high-pressure wave rushing around the perimeter of the combustion chamber. Then — it only takes milliseconds — the heat flows inside the chamber get disrupted and start bouncing back and forth. You get positive feedback, and before you know it your combustion process is out of control. That’s combustion instability, Marcus.”

“So why are you telling me about it?”

“Because it’s killing us. The slightest thing seems to trigger it: cavitation in the pumps, thermal shocks as the engines heat up, acoustical shocks at the moment of ignition.”

“But that kind of instability can’t have been a new problem, even in 1961,” White said.

“Hell, no. The Germans had instability problems all the way back to the goddamn V-2. Each generation of rocket required new fixes. But all of the fixes were pretty much ad-hoc, Marcus; nobody really had a handle on it. And with the F-1 you had this immense size of engine to compound the problem. Maybe,” he mused, “if we’d left well enough alone, and not fucked about with the configuration… but we didn’t. We’re trying to upgrade, to reach eighteen hundred K thrust, up from fifteen hundred. So we’ve made a whole stack of modifications: we increased the oxidizer inducer diameter, strengthened the gimbal seat and the cross block, strengthened the high pressure ducts and the thrust chambers, beefed up the turbine exhaust manifold, improved the heat exchanger, increased the power of the turbine… All of that screwed the stability of the flight configuration, basically. And we’ve had to try to fix it.”

“Come on, Don. Those old guys in the 1960s, from Rocketdyne and Marshall, got the instability problem licked in the end. I mean, with due respect, I’m looking at one of those old bastards right now.”

Baylor looked mournful. “That’s just it, Marcus. I arrived too late. I came into propulsion engineering at Marshall in 1965, just about in time for the Saturn flight testing. I missed all the fun, from the early days, when the core team — the Combustion Devices Team — was working to solve the instability problem.”

“Don’t we have any members of that team left?”

Baylor looked grim. “Marcus, they even sent me around the old people’s homes. Most of those guys are dead, and the rest are eating baby food and complaining about their catheters. Hell, you’re talking about a project that’s nearly fifty years gone. I was just a junior member of the team — and I joined late — and now I’m the most senior guy we have here.” He shook his head. “If only we’d thought to do this twenty years ago — even ten…”

The count reached its final seconds. Baylor turned to the test stand, and picked up his binoculars.

In the last moments, tons of water cascaded down, into the flame deflector pit at the base of the stand. White could hear the roar of that miniature Niagara even from here, even through the glass.

Baylor didn’t seem aware White was here any more; his eyes, behind their big shades, were focused on that test stand.

White could picture what was happening inside the F-1.

The combustion chamber, the tough heart of the engine, was a barrel a yard wide and a little less long. Right now, a few seconds before ignition, four small pre-burners inside that chamber — pilot lights — had lit up, providing a flame at the points where the sprays of lox and kerosene from the injector plate hit each other. The burning of exhaust gases from the turbines produced a thick orange smoke, which burst out of the nozzle and bounced off the flame deflector under the launcher, busting out to either side. The pumps were running up to speed, the valves were opening, and now the propellant poured in: a ton of kerosene, two tons of lox, in the first second alone, and in every second thereafter.

The gases produced by their ignition shouldered out through the nozzle throat at the bottom of the chamber. In these few seconds, as the engine built up to full power, the interior of the combustion chamber went from room temperature to as hot as the surface of the sun; pressure went from zero to a thousand pounds per square inch.

The flame directly under the engine turned to an incandescent white, and the orange smoke billowed outward and upward, enveloping the base of the nozzle. A pillar of pure white light exploded into life under the engine bell.

It was the brightest thing in White’s view, brighter than the sun. His binoculars dimmed themselves down, compensating for that surge of brilliance, obscuring the rest of the test stand structure and dimming the bright blue sky to a muddy grey. The water gushing into the flame pit flashed to steam, and great clouds of it billowed out around the stand, unable to dim the brilliance of that light.

The noise reached them now, a great crackling explosion of nonlinear wave fronts that burst across the desert. The picture window rattled, visibly bowing, and in the depths of his gut White could feel a bass rumble.

White felt his lips pull back into a feral grin, and he whooped. He just let all that pure rocket light wash over his face. This was the way a rocket was supposed to be, he thought: pure liquid fire, none of that dirty yellow-orange shit that came spewing out of the solid-propellant firecrackers they strapped to the side of the Shuttle.

But then the torrent of fire sputtered, as if the engine was being throttled back, or was stalling. White thought he could see the whole test stand shudder.

The nozzle softened and deformed.

It happened in an instant: thick, high-strength steel plate burning through in a quarter of a second, guttering like candle wax. The metal just gushed down into the flame pit, swept away by the energy of the torrent of fire. And then that torrent, without the shaping of the nozzle, turned from a controlled explosion into an uncontrolled one.