"What sort of skin temperatures do you get nowadays?" asked Holt.
"Oh, she'll take up to 1,100 degrees and more," answered Knight, "but the highest we're apt to get is around 730 °C when we're at 5,000 meters per second at 60 kilometers altitude."
"Not much, is it?" asked Holt. "With the old Jupiters, we used to heat up to almost 900 degrees."
"These new vessels have a much lighter wing-loading. That lets us do our gliding considerably higher, and there's less heat transfer because the air's less dense. On some of our troop transfer trips, the boys got very jittery when they looked out the ports and saw the wings a bright, incandescent red."
Despite Knight's reassurances, it was getting uncomfortably warm in the cockpit.
"I'll turn up the refrigeration a bit, so the boys back there won't get to cooking too much and be all nervous," he said.
He twisted the adjustment screw of the temperature regulator and the whine of the cooling turbine rose in pitch against the hissing and roaring of the onrushing air.
Above their heads, the star-strewn sky seemed motionless and below them was naught but pitch darkness. Their wings and nose had begun to glow with the color of old port wine, which penetrated the portholes with a ghostly glimmer and reflected from their faces. Their enormous velocity was betrayed only by the instruments and the incessant roaring as they split the air.
"There's the lighthouse on the Cape of Good Hope!" exclaimed Knight, "We'll be subsonic in another hour or so."
There was still very little sensible evidence of the slowing down of the Sirius. Not long before, they had been lifted into their shoulder belts by the centrifugal acceleration of the wings forcing the ship into a circular path, but this had slacked off and was no longer noticeable. It meant that the excess speed with which Sirius'' had entered the atmosphere had sunk to approximately that of the local orbital speed. But the longitudinal deceleration still read less than O.lg. Twenty minutes after they had passed the Cape of Good Hope, their speed was still above 7,000 meters per second and their altitude well over 70 kilometers.
All this time, the leading edge temperature gauge read but little under 700 °C and the entire nose of the ship was heated by the air friction to a luminous cherry red. Holt's view of the wings revealed that their dark red incandescence progressively diminished towards the trailing edges. It was striking evidence that the boundary layer was growing thicker in chord and reducing the amount of heat transferred by the onrushing air.
It seemed a long time before they became aware of a sickle-shaped glimmering ahead of them. It grew rapidly on both sides of their nose, revealing that they were flying into the dawn. Above the horizon soon glared the livid mantle of the solar corona, to be followed rapidly by the orb of day itself, painfully contracting the pupils of their nightaccustomed eyes.
Soon the advancing line of dawn on Earth had passed below them and Holt noticed that they were flying above an illimitable forest crossed by a silvery, serpentine line which could only be a river.
"That's the Ob," remarked Knight with a glance at the clock. "If our directional gear has been working properly, Novosibirsk ought to be out there to your right, then Tomsk, and the Yenissei River after a minute or so."
Sure enough, another mighty river, disguised from their height as a tiny, silvery thread, passed below them. Occasional patches of snow appeared in the forested Siberian wilderness, growing thicker as they advanced, until near Verhojansk, the "coldest city," the whole lonesome waste lay rigid under its icy frost. Here they had reached the limits of the Arctic, the Northernmost point of their great circle path.
Now headed towards the southeast, Sirius skimmed across the frozen Kolima River. Now, at last, the airspeed meter dropped to 6,000 meters per second, but the altitude was still above 65 kilometers. The wing temperature was on the upgrade and read slightly above 700 °C.
But Sirius was now over the ocean once more. Holt saw Kamchatka's huge peninsula through a hole in a fog bank, thrusting out like a great barrier between Siberia and the Bearing Sea.
They could distinctly feel the increased deceleration imposed by the air upon the racing ship; they were drawn forward against their belts, as though seated in a car whose brakes are applied. When they passed the western outposts of the Aleutians the speed had dropped to 5,000 meters per second, and five minutes later it was only 4,000. The wing temperature, which had been stuck for a long time at around 730 °C, had sunk to 670° and was now rapidly diminishing. From below the pilot's seats, the radioman's hand appeared with a slip of paper.
"Here's the first bearing from Kahului," said Knight, twisting the knob of the course gyro and resetting the ship onto the corrected course. Sirius was cutting deeper and deeper into the atmosphere, whizzing diagonally downward. Knight checked speed and altitude with the figures on a tablet attached to the steering column. These showed him at what altitudes various speeds should be passed as Sirius rapidly lost velocity. When they hit the 1,000 meter per second mark at 33.3 kilometers height, according to plan, the wing temperature was only 237 °C and Knight gave the order to tighten seat belts.
Five minutes elapsed without incident, then the deceleration suddenly increased noticeably for a few seconds. Knight's face grew tense as he manipulated the controls firmly. His eyes were glued to the Mach meter.
"Transonic speed," he said.
Sirius was still 24 kilometers high, but her deceleration again diminished. Gravity had been growing on them imperceptibly all along and was now wholly normal. It held them to their seats as Earth-dwellers have been held through the centuries. Soon the ship had also almost ceased to decelerate. At Knight's command the mechanic lowered the leading edge flaps a few degrees in order to adapt the supersonic airfoils to subsonic flight.
The wings were now at almost the same temperature as the air. The radio operator handed up course corrections in increasingly rapid succession and soon they could see the cloud caps above the Hawaiian Islands far below on their starboard bow.
Knight banked Sirius into a wide spiral glide which ended in a broad sweep across the airport. At his command the mechanic lowered the landing gear and flaps and he finally set the ship on the runway with no more fuss than some casual airliner coming in from Wake Island.
A tractor hooked onto them at the end of the runway and hauled them solemnly to the terminal building of Kahului Spaceport. It was almost 12 hours on the dot since they had been projected upwards towards Lunetta by the huge booster stages.
Catherine was waiting. She had spent the night with some old friends in Kahului, and as she and Gary got into a taxi, Knight gave them a friendly wave of the hand.
"Drop in on us, next time you're near Emerald Bay," shouted Holt.
Chapter 6 — Is it Technically Possible to Reach Mars?
When President Vandenbosch's recommendation that an expedition to Mars be set afoot reached the newspapers and radio commentators, the Red Planet came alive in the minds and consciousness of people the world over. Speculation was rife as to the nature and makeup of the space vessels that would compose the fleet. Technicians and laymen flooded the press with both fanciful and serious comments and suggestions. Rocketry became overnight a word as familiar as television had been forty years before and was far more controversial. The names of Braden, Spencer and Holt ran from mouth to mouth like wildfire.