The base on Christmas Island shared with Kahului the advantage that there was direct sea transportation between it and the plant of United Spacecraft at Long Beach, for very nearly all the material to be shipped was either manufactured there, or passed through there for testing or adaptation. The problem of loading propellants was far easier in steamer ships than in tank cars. It would require more than 500 shiploads, so that this aspect alone was a determining factor in the selection of a new island base. The Dupont Corporation expanded for the Space Forces large propellant plants in both Oakland and San Diego, and nothing was easier than for the tankers to go alongside the loading piers in these harbors, load up, steam to Christmas, and discharge into its storage tanks.
Early in January, 1983, eighteen months work had put the Christmas Island base into temporary operating shape. It was a rude shock which awaited the crews detached from the Lunetta ferry service and their comfortable quarters in Hawaii. The grousing was like the grousing in every army since Caesar's, to the effect that when a base was picked by the Space Forces, it was at the most God-forsaken spot on the map. When they got there, Braden took their worries off their minds by delaying the ferry flights to the orbit of departure as little as possible. To keep soldiers busy was also an old Roman custom.
A number of salvage steamers were always within the Christmas Island atoll while the tankers were unloading propellants into the tank farm near the docks. These salvage ships sought out the exhausted booster stages as they dropped into the ocean. Like returning whalers, they carried the great bulk of the boosters on their low-lying after-decks when they entered the atoll's protected waters through the channel which had been blasted through the barrier reef. They always flew a victory pennant from the fore truck, somewhat like that flown by a successful sail fisherman.
Salvaging boosters had become a science since the first modest space ships were developed; it had become so important that a number of special devices for it had come into being.
The enormous first booster of a Sirius ship produced a thrust of not less than 12,800 tons and imparted to the upper two stages a velocity of 2,350 meters per second in 84 seconds. At the 84 th second, when the initially vertical flight path had curved to a little more than 20° from the horizontal, the ship would be 40 kilometers high and about 50 kilometers horizontally from the launching site. Then the second stage began to exert its thrust, separating from the empty first booster below it. With its tanks empty, the latter still weighed 700 tons.
There is still considerable drag at 2,350 m/sec, even at an altitude of 40 kilometers, and at the moment of separation, a large parachute of wire mesh emerged from the after end of the exhausted booster. The parachute slowly decelerated the great bulk on its still rising path, attaining several hundred degrees of heat in the process, by reason of the high velocity. The metal of which it was constructed, however, could easily withstand this.
The booster continued upward to about 64 kilometers altitude from which it descended to the sea, its velocity having dropped to 1,250 m/sec when it passed the 40 kilometer altitude. Now the booster's flight path began to grow steeper, until it finally reached sea level some 190 miles from the launching site, approaching the water at 50 meters per second. It had flown for seven minutes.
When the huge bulk was still 50 meters above the sea, a ground proximity fuse went into action, igniting the braking rockets. These were mounted in the nose section of the booster and now pointed downwards due to the pull of the parachute on the other end.
Their ten streams of fire, generated by powder, exerted an upward thrust of almost 2,500 tons for two seconds. Had the booster continued seawards at the same rate, it would have been destroyed by the impact, but the rockets, pouring their violence against the water, reduced the speed left by the parachute to almost zero. Thus the booster landed softly in the water, roiled by the rockets, and submerged.
Before long it emerged once more, rolling like a wounded whale as the flotation of the great, empty tanks turned the huge stabilizing fins downwards. Finally it floated supinely, its empty powder rocket tubes pointing at the sky and the heavy rocket plant acting as ballast.
A salvage steamer had been waiting in the vicinity, tracking the booster's descent with radar. Now she hastened to the spot where the great, buoy-like mass rolled amid the frothing seas. She approached it cautiously, with much backing and filling, for to hoist aboard such a clumsy object was no child's play. Specially trained teams had been developed for the purpose, for any slight contact between the hull of the steamer and the delicate structure of the booster might well result in damage which would mean long and costly repairs.
The ship moved stern first towards the booster with the jib of a crane mounted at the taffrail extending above it. From the outer end of the jib hung a bridle with a heavy spreader, upon each end of which sat a man. The bridle was lowered and the two men skillfully shackled the ends of the bridle onto two fittings located atop the booster especially for this purpose.
It was a majestic sight when the crane began to hoist the dripping black monster clear of the sea. The twenty meters of diameter and its 29-meter length, adorned by the huge stabilizing fins, finally hung above the water as the ship's stern sank several feet because of the added weight.
Before the jib of the crane was swung around, a second great stream of water poured out of the belly of the suspended monster. A fresh water hose had been part of the suspension bridle, so that all parts of the valuable booster might be sprayed down to prevent damage by the corrosive sea water to its complicated equipment and delicate structure. When this was completed, the crane swung around slowly and deposited its load upon an open section of the steamer's deck, forward of the crane. Here the stabilizing fins were promptly secured by screws to fittings prepared for them.
But the steel cable leading to the parachute still hung over the side of the ship. It was attached at its inboard end to a ring inside a large containing drum located in the center of the rocket combustion chamber and its nozzle system. The latter covered the whole cross section of the booster. The metallic parachute, of course, had sunk.
To salvage this 'chute with its 85 tons of weight and its diameter of 64.5 meters was almost as much of a problem as to salvage the booster itself.
In earlier days, this complicated job had been done with a large net lowered from the jib crane into the water astern of the steamer. Four steam winches had wound in cables with grapnels at their ends which had engaged in the bulky metallic 'chute and pulled it into the net, piece by piece. Finally the crane had hoisted the net, 'chute and all, inboard.
The salvage was too primitive to avoid frequent damage to the delicate parachutes, and such damage was always followed by extensive repair work.
But now the ferry trips of the Mars vessels were greatly facilitated by a new procedure which had been worked out by the Space Forces for this salvage activity. It had been proved superior to the older method by extensive testing.
A roll of reinforced sailcloth was suspended just aft of the stern of the ship between two outriggers. The roll was about 10 feet thick and as wide as the beam of the ship. The whole thing was somewhat like a roll of carpet. The roll began to turn under the power of an electric winch and the sailcloth dipped into the water with its ends delimited by two thick, round disks. Under the weight of the wire reinforcement, the sailcloth unrolled ever faster until stopped by a brake on the roller. Thus the full 180 meters of the sailcloth was submerged, the 'chute hanging almost collapsed, its depth nearly that of the sailcloth.