The hulking form of the B-52 sat on its runway in a puddle of light cast by a circle of big portable floods. Trailers and carts were clustered around the bomber. A fog of crisp liquid oxygen vapor shrouded the contours of the big plane, and people moved through the mist, speaking to each other calmly, working on the aircraft.

The X-15 itself hung from bomb shackles under the wing of the B-52, black and sleek, dark even in the glare of the floods, as if it actually absorbed the light.

There was a pungent stink of ammonia, which reached Gareth Deeke even across a hundred yards.

The smell, suffusing this grey January dawn, triggered his memories sharply, and he felt the years fall away from him; it was as if he was back at Edwards, preparing to burn off another vodka hangover in the exhilaration and terror of a high-altitude flight.

But as he walked towards the B-52, the ground crew parted before him and avoided his eyes; there was none of the good-natured bull which he recalled from his days at Edwards. As if we are all doing something different now, he thought. Something wrong.

Here at Canaveral Air Force Base, he was only ten miles or so to the south of Kennedy Space Center, where Endeavour was being prepared for the last Shuttle launch of all. He peered into the north. Maybe he’d be able to pick out the illuminated pad: on clear nights the visibility of the pad’s lights, looming on the horizon, was a symbol of the failure by Hartle and his contacts to impede or even slow the preparations for the final Titan launch, to stem the tide of public support which still seemed to be flowing, generally, in favor of the mission. Certainly, on launch day, this whole damn area would be flooded with rocket light. But today the mist was lingering in the cold January dawn, and to the north there was only darkness.

He reached the bomber.

X-15 looked more like a missile than a plane. Big frosted pipes lay on the surface of the runway, feeding liquids and gases into the rocket plane. But the black lines of the X-15 were spoiled by the attachment of a slim white cylinder, round-nosed and finned, under the center line of the forward fuselage.

It was an ASAT.

Gareth Deeke, heart pumping, walked around his bird. X-15, restored from the museum where it had waited out the decades, looked ready to fly, but today was not its day; this morning, under cover of darkness, the ground crew were rehearsing the procedures they would use to mount and fly the bird.

If it came to that.

The rocket plane was just a big propellant tank, made of a tough heat-resistant nickel-steel alloy, with a cockpit on the front and rocket engine on the back end. The tanks were nested cylinders, with a long, skinny pipe containing high pressure helium pressurization gas embedded within the big liquid oxygen tanks towards the front of the aircraft. The fuel tank, containing anhydrous ammonia, made up the rear section of the airplane.

Deeke walked past the frosted-up walls of the lox tank. He didn’t get too close; the tank seemed to suck the warmth out of the air around him, cold as it was already. You could always tell how much lox was left in the tank by the level of frost on that outer skin. He could make out the three main fittings holding the rocket plane in place, and the quick-disconnect lines snaking out of the B-52 which topped up X-15 with nitrogen and liquid oxygen. Reaction control jet nozzles gaped in the hull around the nose, two on top, two on the bottom, and two to either side. Beside the nozzles there was a stencilled notice saying BEWARE OF BLAST.

He reached the cockpit, an aluminum box which would be pressurized with nitrogen to thirty-five thousand feet equivalent, and suspended inside the hull of the aircraft itself, isolated to keep it cool. Behind the cockpit was a big pressurized bay containing over a thousand pounds of instrumentation, to measure airspeed, altitude, pitch, yaw and roll rates, control surface positions, bending loads, temperatures… He had been assured that the handling characteristics and controls of the plane would be just as they had been back in 1961, though he didn’t know how the hell they had got all that antique electronics to function again after forty years. Maybe they had cannibalized X-15A-2, the other surviving X-15, which was mothballed at the USAF museum at Wright-Patterson AFB.

He reached the engine compartment at the back of the plane. The XLR-99 rocket nozzle gaped at the back of the aircraft, two feet long. The rocket, which hadn’t been fired in anger for forty years, looked as fresh as if it had come out of the Thiokol factory yesterday.

He allowed himself a stab of anger. He’d long lost count of the number of press releases he’d read which said the Shuttle’s main engine was the world’s first truly throttleable engine. The XLR-99 engine was a throttleable, restartable, reusable rocket engine, with almost as much thrust as the throwaway Redstone booster which had thrown Shepard and Grissom up on their first Mercury suborbital lobs. The USAF had been happily flying the thing ten years before the Apollo Lunar Module’s much-vaunted throttleable rockets had carried men to the Moon, and twenty years before Shuttle had first launched, years before NASA had started pronouncing you couldn’t build such a thing.

We threw all this away, he thought, all the possibilities summed up in the sleek black hide of this thing, because of stupidity and greed, and fear of the Russians, and damn bureaucratic infighting, a millennial madness reaching its final flowering over on Pad 39-B even now.

In its flight days the X-15 had borne USAF decals on its wings and fuselage, and big NASA strip decals on its tail. But today, the hull was a bare black, unmarked save for information and warning stencils, and its serial number, AFS-6670.

And that, Deeke reflected sourly, was entirely appropriate.

The mist cleared a little. There were stars in the sky. One of them, bright and clear, passed smoothly through the constellations, directly above him. That was the Shuttle orbiter Discovery, its wings reshaped for Titan’s thick air, already in orbit with its cluster of fuel tanks and equipment, waiting for its crew.

It had to be stopped.

Determination surged in him. He put aside the doubts and qualms of the ground techs. He had no doubts.

On the day, if the call came, he would be ready to fly.

At last, the schedule for STS-147 was firmed up.

STS-147 would be the last Shuttle launch: the last flight of Endeavour, the mission that would take the crew — including Paula Benacerraf — up to Earth orbit.

When the launch date was finalized, Benacerraf found herself staring at it, on her softscreen, for minutes at a time. It was like the date of her own execution. She would not see the dawn of the following day — and, perhaps, no dawn on Earth ever after.

As that epochal day approached, the tempo of Benacerraf’s life accelerated. She was doing three jobs now. As head of the Shuttle program she had responsibilities to discharge beyond the Titan mission, such as the disposal of the program’s assets around the country after the final flights — including thousands of staff. Then, too, she retained a lot of responsibility for the Station hab module conversion, and she spent long hours at Marshall and Seattle working on that.

Finally she was an astronaut, trying to prepare for the mission itself.

And, in the midst of this crescendo of activity, Paula Benacerraf — human, grandmother — prepared to leave Earth.

After all, the Titan expedition was going to be an open-ended mission. So she figured she ought to shut down her life, here on Earth, as if she was indeed going to die.