Ten days after Mike's first proposal of concreted steel as a material
for space ship construction, the parts of the first casting of the
mockup were assembled. They were a mold for the hull of a space ship.
There were more plaster sections for a second mold ready to be dried out
now, but meanwhile vehicles like concrete mixers mixed turnings and
filings and powder in vast quantities and poured the dry mass here and
there in the first completed mold. Then men began to wrap the gigantic
object with iron wire. Presently that iron wire glowed slightly, and the
whole huge mold grew hotter and hotter and hotter. And after a time it
was allowed to cool.

But that did not mean a ceasing of activity. The plaster casts had been
made while the concreting process was worked out. The concreting
process--including the heating--was in action while fittings were being
flown to the Shed. But other hulls were being formed by metal-concrete
formation even before the first mold was taken down.

When the plaster sections came off, there was a long, gleaming,
frosty-sheened metal hull waiting for the fittings. It was a replacement
of one of the two shot-down space craft, ready for fitting out some six
weeks ahead of schedule. Next day there was a second metal hull, still
too hot to touch. The day after that there was another.

Then they began to be turned out at the rate of two a day, and all the
vast expanse of the Shed resounded with the work on them. Drills drilled
and torches burned and hammers hammered. Small diesels rumbled. Disk
saws cut metal like butter by the seemingly impractical method of
spinning at 20,000 revolutions per minute. Convoys of motor busses
rolled out from Bootstrap at change-shift time, and there were again