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.Mike nodded.He drained his coffee cup and slipped down from his chair. Come on, Chief! C mon, Haney!He led them out of the room.Joe fiddled with his spoon a moment, and then said:  The crewman I was to have subbed for if he didn tget well he did, didn t he?Sally answered reluctantly:  Y-yes.Joe said measuredly:  Well, then that s that! I guess it will be all right for me to stick around and watchthe take-off?Sally s eyes were misty. Of course it will, Joe! I m so sorry!Joe grinned, but even to himself his face seemed like a mask. Into each life some rain must fall.Let s go out and see what s been accomplished since I went to sleep.All right?They went out of the Platform together.And as soon as they reached the floor of the Shed it was plainthat the stage had been set for stirring events.The top five or six levels of scaffolding had already been removed, and more of the girders and pipeswere coming down in bundles on lines from giraffelike cranes.There were some new-type trucks in view,too, giants of the kind that carry ready-mixed concrete through city streets.They were pouring a doughywhite paste into huge buckets that carried it aloft, where it vanished into the mouths of tubes that seemedto replace the scaffolding along the Platform s sides. Lining the rockets, said Sally in a subdued voice.[Pg 128]Joe watched.He knew about this, too.It had been controversial for a time.After the pushpots and theirjatos had served as the first two stages of a multiple-rocket aggregation, the Platform carried rocket fuelas the third stage.But the Platform was a highly special ballistic problem.It would take off almosthorizontally a great advantage in fueling matters.This was practical simply because the Platform couldbe lifted far beyond effective air resistance, and already have considerable speed before its own rocketsflared.Moreover, it was not a space ship in the sense of needing rockets for landing purposes.It wouldn t land.Not ever.And again there was the fact that men would be riding in it.That ruled out the use of eight- andten- and fifteen-gravity acceleration.It had to make use of a long period of relatively slow accelerationrather than a brief terrific surge of power.So its very special rockets had been designed as the answer.They were solid-fuel rockets, though solid fuels had been long abandoned for long-range missiles.Butthey were entirely unlike other solid-fuel drives.The pasty white compound being hauled aloft was aself-setting refractory compound with which the rocket tubes would be lined, with the solid fuel filling thecenter.The tubes themselves were thin steel absurdly thin but wound with wire under tension toprovide strength against bursting, like old-fashioned rifle cannon.When the fuel was fired, it would be at the muzzle end of the rocket tube, and the fuel would burnforward at so many inches per second.The refractory lining would resist the rocket blast for a certaintime and then crumble away.Crumbling, the refractory particles would be hurled astern and so serve asreaction mass.When the steel outer tubes were exposed, they would melt and be additional reactionmass.In effect, as the rocket fuel was exhausted, the tubes that contained it dissolved into their own blast andadded to the accelerating thrust, even as they diminished the amount of mass to be accelerated.Then thequantity of fuel burned could diminish the tubes could grow smaller so the rate of speed gain[Pg 129]would remain constant.Under the highly special conditions of this particular occasion, there was anotable gain in efficiency over a liquid-fuel rocket design.For one item, the Platform would certainly haveno use for fuel pumps and fuel tanks once it was in its orbit.In this way, it wouldn t have them.Theirequivalent in mass would have been used to gain velocity.And when the Platform finally rode in space, itwould have expended every ounce of the driving apparatus used to get it there.Now the rocket tubes were being lined and loaded.The time to take-off was growing short indeed.Joe watched a while and turned away [ Pobierz całość w formacie PDF ]