The Soyuz was shaped like a pepper-pot. Its main body was a squat cylinder called the instrument-assembly module, which housed fuel tanks, oxygen, water supplies, ancillary equipment, and the big retro-rocket that would, in a normal flight, be used to return them from low orbit to the Earth. On top of this sat the descent module, a dome-shaped tent of metal, where Henry would sit to ride to orbit. And over this was fixed a bulbous misshapen sphere called the orbital module, with equipment for operations on orbit.

The Soyuz had been designed, all those years ago, as the core of a system that should have taken Soviets to the Moon. It had never gotten that far. Instead the Soyuz had become an orbital ferry, carrying cosmonauts to three generations of space stations: the old half-military Salyuts, the Mir, and now the International Space Station. When it was time to return to Earth, the orbital compartment and the service module would be cast off to burn up, and only the descent module would reenter and parachute to the land, somewhere in the echoing heart of Asia.

The descent module was unbelievably cramped, even compared to the Apollos he’d seen in museums. It was just a crude stretched hemisphere of thick metal, so small your legs would be jammed up against the next guy’s, and it was impossible to straighten them out.

The ship’s main controls were here. But there was a disturbingly small number of instruments fixed to the walls. Some of them had even been hand-lettered with Cyrillic characters, or fixed on top of other components. The windows were small, circular and featured big heavy panes of glass and rings of bolts, like portholes from Captain Nemo’s Nautilus. But he could see no daylight through the windows right now; that big white faring saw to that.

Geena struggled out of her seat, and pulled closed the hatch in the roof. Soon after, Henry heard a muffled thud, as the techs shut the outer hatch.

And so he was sealed up in the ultimate enclosure: a cell within which he couldn’t even stand up, and yet which would carry him away from the Earth.

He searched for some reflection of this in Geena’s eyes. But there was none; Geena’s expression was cloudy, distracted. After a couple of seconds she turned back to her checklist, and worked through instrument settings, exchanging messages with the crisp Russian voices of the ground control in their bunker.

Jane understood the problem. In the last couple of weeks she’d heard about other planes which had run into this difficulty. But knowing didn’t help; she knew, in fact, that the outlook for their survival wasn’t good.

The volcanic debris, silicate ash suspended in the air, fused when it came into contact with the hot metal of an aeroplane’s combustion chambers and turbines. It was like damping a fire with sand. Engines just flamed out.