"Ho--I wish they'd let me go on active duty with the space fleet! A scientific reputation can be an awful handicap at times," he grinned. He had been rejected very emphatically when he had tried to enlist. The Interplanetary governments had stated flatly that he was too important as a scientist to be risked as a pilot of a space ship. On two worlds the great construction plants were humming with activity. Civilian production of all but the barest essentials had been put aside for the duration of the emergency. Space ships were being turned out at top speed, getting their fuel from the wrecks of the invaders' cruisers. Each ship needed only a small amount of the light-metal, for the energy content was tremendous. And those ships had been gigantic. Already there was a fleet of speedsters and mother ships out there in space, and with every passing hour others left the home planets, always adding to the fighting force that was to engage the attackers deep in space, where no stray ships might filter through to destroy the cities of Earth or Venus. Assembly lines were now turning out ships so rapidly that the training of their operators was the most serious problem. This difficulty had finally been overcome by a very abbreviated training course in the actual manipulation of the controls on the home planets, and subsequent training as the squadrons raced on their outward courses. It was soon decided that there must be another service beside that of the ordinary ships. One plant was devoted to making huge interstellar liners. These giants, made on Venus, were nearly a quarter of a mile long, and though diminutive in comparison with the giant Nigran ships, they were still decidedly large. Twelve of these could be completed within the next month, it was found; and one was immediately set aside as an officers' headquarters ship. It was recognized that the officers must be within a few hundred thousand miles of the actual engagements, for decisions would have to be made without too much loss of time in the transmission of reports. The ship must not be brought too near the front lest the officers be endangered and the entire engagement lost for want of the organizing central headquarters. The final solution had been the huge central control ship. The other large vessels were to be used to carry food and supplies. They were not to enter the engagement, for their huge size would make them as vulnerable to the tiny darting mites of space as the Nigran ships had been to the Interplanetary Patrol. The little ships could not conveniently stock for more than a week of engagement, then drop back to these warehouses of space, and go forward again for action.