indelible second-by-second record of his reactions.

The data transmitter was attached to the right-hand side of the cockpit

by his elbow. Brickman reached across with his left hand and switched

it on.

Flight Control radioed back immediately. 'Easy X-Ray One, your data

link reads A-Okay."

Brickman acknowledged the Ramp Marshal's windup signal and hit the

button. The electric motor behind his seat whined into life. Brickman

checked the movement of the control surfaces, then moved forward under

the direction of the Ramp Marshal's batons until the nose of the

Skyhawk was a couple of feet from the innermost ramp door.

With a swishing noise that Brickman barely heard above the thrumming

engine, the fifty foot high wall in front of him slid downwards into

the floor. Following the orange batons, Brickman taxied over it

towards the double outer doors, stopping on the parallel yellow line.

At this point, the ramp access tunnel was one hundred feet wide, its

sides sloping gently inwards towards the ceiling. Brickman remembered

from the briefing that the inner pair of doors opened sideways; the

outer pair overlapped horizontally; the larger top section going into

the roof, the lower section into the floor. This arrangement allowed

the ramp crew to adjust the aperture to the size of the object passing

through it.

Glancing in his rearview mirror, Brickman saw to his surprise that the

huge door behind him had risen noiselessly, cutting him off from the

Federation.

The voice of the controller came over his headset. 'Easy X-Ray One,

this is Ground Control. Light balance will commence in five seconds.

The doors will open in ten. Do not attempt to taxi through until you

see the green. Once you cross the double yellow line, you are clear

for takeoff.

Transmit your callsign when you pass over the red, white and blue

beacon on your return leg. Over."

'Easy X-Ray One, Roger." Brickman's voice contained a tremor of

excitement.

'Good luck,' said the voice in his ear.

In the same instant, banks of neon tubes stretching along the walls

from floor to ceiling and across the ceiling itself rippled into life,

creating a glowing tunnel of light that grew progressively brighter

towards the ramp door to match the intensity of the daylight that lay

beyond.

Brickman lowered his visor. Five seconds later, the twelve foot-thick

inner doors slid apart and the lower section of the outer door sank

level with the ramp presenting Brickman with a fifteen foot high slot

just wide enough for the Skyhawk to pass through.

Nosewheel on the centre line, Brickman taxied out on the green, passing

under the equally massive concrete curtain that formed the top section

of' the outer door. Rolling clear of its threatening bulk, he paused

on the double yellow line that stretched from wall to wall and took

stock of his surroundings.

He saw that he was in a concrete canyon with sheer, unseamed, fifty

foot high walls. Ahead of him, the ramp sloped gently upwards.

Brickman knew from his study of the model that the walls which now

enclosed him angled out sharply, tapering down, as the ramp rose in the

shape of a giant fan, to meet the overground.

The canyon was roofed with a flat expanse of brilliant blue.

With a sudden shock of recognition, Brickman realised that he was not

looking at another illuminated ceiling - like those in the Federation's

central plazas - but at the sky.

The ceiling of the world. 'The wild blue yonder' - that heartsurging

phrase from the battle hymn of the Flight Academy that had fired

Brickman's imagination at the age of ten. Not wrought by concealed

tubes of neon, but filled with a light of dazzling, almost

overpowering, intensity that bounced off the bleached concrete and cast

sharp, rich, dark shadows on the r