Acid Sky (3 page)
The pitch thrusters fired at the command of the autopilot, and the spaceplane turned slowly end-over-end so that it was facing forward, nose-high to present the broadest surface to the oncoming atmosphere. Clare checked their attitude and re-entry angle once the manoeuvre was complete; any error could cause them to plunge too deeply into the atmosphere and burn up, or skip out again and miss their target completely.
She rested her right hand on the sidestick, ready to take control if needed, but the autopilot was doing its job, following the descent profile perfectly.
‘Re-entry interface,’ she announced, and the ship shuddered as it encountered the first wisps of atmosphere on the edge of space. The spaceplane’s forward velocity had been reduced to four kilometres per second by the de-orbit burn, but they were still travelling at hypersonic speeds.
A faint hiss grew at the edges of hearing, and increased until it surrounded the entire cabin. Through the narrow vision slit in the window visor, a bright glow flickered and wavered, growing in intensity until it filled the cabin with a pearlescent, white light. Clare felt herself falling forwards into her seat straps now as the spaceplane braked its forward velocity with the air resistance of the atmosphere.
A sudden bump, and the ship lurched, then another, and then they were crashing and thumping through the searing-hot air. Clare kept her eyes on the instruments and the primary flight display, watching the autopilot make the necessary corrections. The nosecone and wing leading edge temperatures were increasing rapidly, climbing through 700 degrees, 800 degrees, and still rising. Cold fuel flowed through cooling channels in the nose and leading edges of the wing and fins, helping to carry away the intense heat, but the metal surfaces were glowing red-hot.
The re-entry chop became more severe, bouncing them around in their seats. Something broke loose behind in the passenger cabin and banged to the floor. Clare could hardly read the instrument panel; her vision was a violent, dancing blur. The seat straps tugged painfully at her body as the negative gees mounted.
The spaceplane lurched violently to one side, and for a few terrifying moments Clare thought the ship was going to spin and break up, disintegrating like a comet in the roasting heat of the sky. The turbulence decreased for a moment, and the ship steadied out, then it hammered against the ship with increased violence. She knew that spaceplanes had broken apart during re-entry when control had been lost; they must be very close now. She could feel the sudden shoves caused by the thrusters firing almost continuously to try to keep them stable …
The wild ride lessened as the ship’s descent smoothed out, and the painful deceleration started to ease off. Outside, the freezing air at 140 kilometres high flowed over the glowing metal, cooling it down to a sullen red, then a dull grey. The spaceplane pitched forward, lowering its nose, and without any sense of transition, they were falling, arrowing down into the thin, cold air.
It was eerily quiet after the noise and buffeting of re-entry, just the whisper of air rushing past the exterior, no sound of any engines. Clare exhaled slowly.
‘One of the more exciting rides I’ve had,’ Hartigan commented dryly, and thumbed the intercom: ‘Are you guys all okay back there? What’s come loose?’
‘A locker door came open – it’s a spare helmet. It’s stuck under my seat now,’ a voice responded.
‘Oh, okay. Try to hang onto it if it looks like getting loose again. We’re through re-entry now, and in the descent. Not long to go before we land.’ He cut the intercom and turned his attention to the descent display. They were passing 85 kilometres altitude, with most of their forward speed gone, in a steep descent towards the surface.
‘Carrier Two Eight Approach, Skydive One Four Seven. Re-entry complete and through eight five zero,’ Hartigan said, watching the altitude.
‘Skydive One Four Seven, Langley Approach. Reduce your descent speed to seven zero and left turn onto heading two eight zero.’
‘Reduce descent to seven zero, left turn to two eight zero, Skydive One Four Seven,’ Hartigan acknowledged. Clare pulled back gently on the sidestick to ease the spaceplane out of its steep dive, and banked to the left. The craft responded sluggishly to the flight controls; the air at this height was still too thin to provide much lift.
‘Visor down,’ Clare said, keeping her concentration on controlling the spaceplane as she turned out on their new heading. Hartigan reached out and operated the control, and the protective visor, which had covered the windows during the descent, lowered slowly.
Light poured in as the visor sank out of sight, light from the Sun reflecting off the cloud deck far below them. They had entered the atmosphere over the night side of the planet, and were coming round into the dawn of the next day. The sky above the clouds was a deep blue, darkening to the black of space.
‘Sixty-nine kilometres altitude,’ Hartigan said, ‘deploying air data probes.’ On the side of the spaceplane’s hull, four small panels rotated to expose the delicate pitot tubes and angle-of-attack vanes to the slipstream. ‘Sixty-seven kilometres. Airspeed Mach one and falling.’
‘Roger. Relight sequence.’
Hartigan reached up to the overhead panel and operated a switch to open the engine intakes. Held tight closed against the searing heat of re-entry, the intakes opened slowly like twin sharks’ mouths, gulping in the cold air. Deep inside the engines, the compressors started to turn from the windmill effect of the high-speed air rushing through them. Hartigan watched the revolutions build and the pressure ratios start to rise.
‘Sixty-four kilometres, starting two and three.’ He pulled the start selectors for the innermost two engines, and moved the fuel control levers to
RUN
. Nothing appeared to happen at first, then the whine of the spinning compressors was slowly replaced by a rising, muffled roar.
‘EGT and oil pressure rising,’ Hartigan confirmed, ‘starting one and four.’ He repeated the procedure for the outer two engines, and watched the engine displays as temperatures and oil pressures rose in all four engines. Relighting the turbojets after their long soak in the cold of space could be a tricky moment; the atmosphere of Venus did not support combustion, and the burners had to be relit on a carefully controlled mix of liquid oxygen and fuel. This time, however, the engines had all come up without any issues, and were settling out nicely.
‘All engines running and stabilised at flight idle.’
‘Set thrust.’
Hartigan pushed the thrust levers forward to the middle detent and engaged the autothrottles. The roar of the engines increased as they came under the control of the autopilot.
‘One Four Seven, we have you descending through six three five. Descend and maintain six three zero, maintain current heading.’
Hartigan acknowledged the instructions and Clare lifted the nose. The big delta wing bit into the air and the spaceplane levelled off at sixty-three kilometres altitude. She pressed the
ALT HOLD
button on the autopilot.
‘Four minutes to landing,’ Hartigan said quietly. ‘On course, thirty-five kilometres to run.’
Clare nodded, concentrating on the controls and the scene ahead. The Sun was almost overhead now, and the sky had brightened to a pale blue, with a brilliant white deck of clouds beneath a faint haze.
Time to bring their airspeed down. She selected the speed brakes, and on the surface of the wings, spoiler panels popped up. A roar of disrupted air came through the cabin walls as their airspeed bled away.
‘One Four Seven, descend to six two zero and intercept localiser for landing heading two seven zero.’
Clare could see the localiser beam drifting across the navigation display, and she banked the spaceplane to the left so that the autopilot could capture it. She dialled in the lower altitude and the spaceplane tilted down towards the clouds. The controls were becoming more effective as the air grew denser, and the craft shook briefly as it flew through a swirl of turbulent air.
‘Gear down.’
Hartigan moved the gear selector out of its detent and selected it to
DOWN
. There was a whine of actuators, and a rumble of air as the doors opened and the landing gear extended into the slipstream.
‘Down and locked,’ Hartigan confirmed, as the gear position indicators turned green. ‘Landing lights on.’ The spaceplane’s lights, two on the nose gear leg and one in each of the main gear bays, came on, four tiny suns in the blue sky.
‘Hook down.’
Under the rear belly of the spaceplane, a long, thin arm of high-tensile steel ending in a flat hook lowered until it was trailing below the aircraft. This was the arresting hook, designed to catch and hold onto the arresting cable that was waiting for them.
‘One Four Seven, we have you on localiser. Descend to six one five and contact Tower on VHF.’
‘Two minutes to landing.’ Hartigan said as he selected the tower frequency, ‘you’re doing fine. Let me know when you want the landing checklist.’
Clare didn’t respond, but Hartigan’s calm voice reassured her. Her breathing steadied, and she took her hand off the sidestick and flexed her fingers before taking it back again. As the spaceplane settled at its final speed of 140 metres per second, she withdrew the speed brakes and armed the autopilot for landing.
‘Skydive One Four Seven, Tower. Maintain current height to intercept glideslope. You are number one for landing.’
‘Dump fuel to maximum weight.’ This was always a critical stage. The spaceplane was coming in with excess fuel in case it had to divert to another carrier, but the extra weight made it too heavy to land on the carrier’s deck. Once they dumped the spare fuel, they had to land, although they had enough fuel for several attempts.
A stream of vapour erupted into the sky behind them as Hartigan opened the valves to vent their excess liquid oxygen overboard, then after a short pause the liquid propane followed.
‘Fuel dump completed, we’re down to five tonnes.’
‘Landing checklist,’ Clare said, her eyes flicking across the instruments. They ran through the items carefully, making sure that the craft was configured correctly, and that they hadn’t missed anything. They were only a minute away now.
A symbol flashed on the flight display.
‘Glideslope captured. You’re established for landing,’ Hartigan added. The autopilot had locked on to the invisible radio beams radiating into the sky behind the carrier, and was adjusting their descent to bring them down onto the flight deck.
‘One Four Seven, we have you on glideslope. Maintain speed one four zero. Report visual and fuel state.’
‘Do you see them?’
‘No …’ Clare scanned just below the horizon. The haze above the clouds made it difficult to make out details. A sudden gust shook the cabin; the big spaceplane rolled slightly, and the autopilot compensated.
‘Five kilometres to run – we should be able to see the beacon.’
‘I see them. Twelve o’clock low.’ Clare’s sharp eyes had spotted it; a tiny dark shape moving against the clouds ahead and slightly below them. Suddenly it all seemed impossible. How could she land this huge spaceplane on that tiny speck? It was all happening too fast.
‘One Four Seven, carrier in sight. Fuel state is four decimal nine tonnes.’ Hartigan released the transmit and glanced down at the navigation display. ‘Four kilometres. You’re set up nicely. Just fly it in.’
‘One Four Seven, your fuel state four decimal nine. Landing system lock. Clear to land, release hook and hold for instructions when down.’
Hartigan scanned the instruments and glanced up at the scene outside. The carrier was clearly visible now, a dark arrowhead grazing the high clouds, with two bright strobe lights winking on each wingtip. He could just make out the lines of lights that marked the flight deck.
His left hand moved to rest on the sidestick, and Clare glanced across for a moment. If there had been any issues with the approach so far, he would take over and fly the final stages of the landing himself.
‘Proceed,’ he said, and sat back in his seat.
Clare tried to swallow, but her throat was dry. She had flown this so many times in the simulator, but doing it for real was scarily different, and she had half-expected him to take over. Now she was flying a real spaceplane down to a landing on a carrier, and there were just seconds to go. Everything had been checked, the craft was configured correctly; all she had to do was fly the guidance cues onto the deck. But it was
real
–the carrier that grew in size with every second was
real
, the people behind her were
real
, the carrier’s deck was
real
and could smash them from the sky if they didn’t land precisely right, the—
‘Call the ball.’ Hartigan’s calm voice brought her back to the task in hand, as he reminded her to make the traditional carrier pilot’s call that the optical landing system was in sight. With the autopilot riding the glideslope right down to the deck, it was rarely needed, but it was a last-ditch visual reference that could save their lives if the automatic systems failed.
Clare’s attention came off the instrument panel now and she concentrated entirely on the visual approach. She looked through a head-up display panel that projected a series of green lines and markers over the scene, showing her landing path. The carrier was clearly visible now, its gigantic shape holding steady in the sky ahead. To the left side of the flight deck, an orange light shone out steadily, lined up against a row of green reference lights. If they were too high or too low, the ‘ball’ would move up or down accordingly, but the autopilot was bringing them in precisely on the glideslope.
‘One Four Seven, we have the ball, fuel state four decimal seven, established for landing.’
‘One Four Seven, land.’
Clare squeezed the autopilot disconnect button on her sidestick, and a warning tone sounded in their headsets. She was flying the craft manually now; the autopilot had done its job and placed them on final approach. The spaceplane could of course land itself, but USAC required that its pilots stayed proficient at making landings unaided.