Five thousand feet up, and he was still sixty miles from his goal.

The land seemed to flatten further, the close horizon receding.

And then he flew past the flank of a round-shouldered lunar mountain, grey, pock-marked. Its shadowed far side was limned by a graceful, powdery curve of sunlit regolith, and its summit was lost above him.

As soon as he perceived the mountain, it was gone, lost behind him, as unreachable as his childhood.

Twenty seconds. Less than two thousand feet. The craters ahead were foreshortened to ellipses, pools of shadow in the sunlight, flattening.

He flew into shadow, and he could see no more.

And so, in darkness, Arkady — still moving at a mile a second, sitting up in his couch — hit the surface of the Moon.

Arkady’s life, the success of his mission, was utterly dependent on Henry’s theories.

At the moment of touchdown — the instant at which the rounded belly of the Soyuz impacted the lunar dirt — two things happened.

First, the attitude thrusters beneath Arkady’s feet fired on full strength, lifting Soyuz away from the regolith. The thrust was sufficient to hold eighty per cent of the Soyuz’s weight up from the surface; the actual depth of contact ought to be no more than a few inches. Other thrusters fired intermittently, to keep the craft upright, stop it tumbling.

Second, the Star Wars laser fired from the craft’s nose.

If this South Pole crater was indeed a frozen lake of water, dusted over by regolith, then the laser should blast-melt a shallow furrow, a canal of glowing steam, utterly straight ahead of Arkady. The liquid water — persisting for a few seconds before boiling away — would lubricate the ferocious contact between the hull of the Soyuz and the ancient ice.

The Soyuz would shed its orbital speed in friction with the water, and — sliding home like a baseball player coming to a plate — would come to a gentle halt, with barely any fuel expended.

That, at any rate, was the theory.

A hundred seconds and it would be over, one way or another.

Arkady was thrust forward against his chest restraints. The impact was violent, spine-jarring, harder than he expected.

The Soyuz groaned like a tin can. The craft rattled and jumped, as if some giant were battering its hull, the vibration so violent he could no longer see the instruments. The deceleration should be less than one and a half G, but it was a long time since he had been on Earth, and it was in any case the vibration that was shaking him to pieces.

…But the craft held. The cabin lights flickered, but stayed bright.

The pressure, the noise and vibration, continued. He struggled to stay upright, to keep breathing. His ribs ached, and there was a greying around the rim of his vision.