Chapter 13: Peril!

Sergeant major Koa asked thoughtfully, “Sir, would it do the Connie much good to launch boats this close to the sun? They’d have to use too much fuel just keeping position.”

“You could be right,” Rip said slowly. Koa had a point! To counter gravitational attraction took velocity, which meant consumption of fuel. Maneuvering boats meant rapid velocity changes. Against the sun’s terrific gravity at this distance, it also meant maximum thrust and maximum fuel flow most of the time. The asteroid, in a planned orbit with the correct velocity, was safe enough, and the Connie cruiser would simply match the asteroid’s orbit. But boats, which had to maneuver, were another matter.

Rip figured quickly. In accordance with Newton’s Law, gravitational attraction increased rapidly on approaching a body. If he could put the asteroid even closer to the sun, the boat problem would become worse, until even a small velocity change in the wrong direction could leave a boat in the terrible position of not having enough thrust for a long enough time to keep from being drawn into the sun.

But to change the asteroid’s orbit was dangerous! It meant losing just enough velocity to be drawn closer to the sun, and then picking up a much higher velocity to get free again!

Rip got his instruments and pulled out a special slide rule designed for use in space. He had Koa stand by with stylus and computation board and take down his figures.

He recalculated the safety factor he had used when deciding how close to the sun to put the asteroid, then took quick star sights to determine their exact position. They were within a few miles of perihelion, the point at which they would be closest to Sol.

Rip tapped gloved fingers on his helmet absently. If they could blast out of the orbit and drive into the sun ... He estimated the result. A few miles per second of less speed would let them be pulled so far within the sun’s field of gravity that, within an hour or so, small boats would venture into space only at their peril.

He reviewed the equipment. They had tubes of rocket fuel, but the tubes wouldn’t give the powerful thrust needed for this job. They had one atomic bomb. One wasn’t enough. Not only must they drive toward the sun, but also they must keep reserve power to blast free again. If only they had a pair of nuclear charges!

He called his Planeteers together and outlined the problem. Perhaps one of them would have an idea. But no useful suggestions were forth-coming--until Dominico spoke up. “Sir, why don’t we make two bombs from one?”

“I wish we could,” Rip said. “Do you know how?”

“No, Lieutenant. If we had parts, I could put bombs together. I can take them apart, but I don’t know how to make two out of one.” The Italian Planeteer looked accusingly at Rip. “I thought maybe you knew, sir.”

Rip grunted. If they had parts, he could assemble nuclear bombs, too. Part of his physics training had been concerned with fission and its various applications. But no one had taught him how to make two bombs out of one.

The theory behind this particular bomb design was simple. Two or more correctly sized pieces of plutonium or uranium isotope, when brought together, formed what was known as a critical mass, which would fission. The fissioning released energy and produced the explosion.

But there was a wide gap between theory and practice. A nuclear bomb was actually pretty complicated. It had to be complicated to keep the pieces of the fissionable material apart until a chemical explosion drove them together fast and hard enough to create a fission explosion. If the pieces weren’t brought together rapidly enough, the mass would fission in a slow chain reaction with no explosion.

Rip was trained in scientific analysis. He tackled the problem logically, considering the design of a nuclear bomb and the reasons for it.

Atomic bombs had to be carried. That meant an outer casing was necessary. The casing had a lot to do with the design. Suppose no casing were required? What would be needed?

He took the stylus and computation board from Koa and jotted down the parts required. First, two or more pieces of plutonium large enough to form a critical mass. Second, a neutron source--the type of radioactivity that produced neutrons--to accelerate the reaction. Third, some kind of neutron reflector. And fourth, explosive to drive the pieces together.

Did they have all those items? He checked them off. Their single five KT bomb contained at least enough plutonium for two critical masses, if brought together inside a good neutron reflector. Each mass should give about a two kiloton explosion. And they did have a good neutron reflector--nuclite. There wasn’t anything better.

“What have we got for a neutron source?” he asked aloud. He was really asking himself, but he got a quick answer from Koa.

“Sir, some of the stuff left in the craters from the other explosions gives off neutrons.”

“You’re right,” Rip agreed instantly. A small piece from one of the craters, when combined with half of the neutron source in the bomb, should be enough. As for the explosive, they had exploding heads on their attack rockets.

In other words, he had what he needed--except for a method of putting all the pieces together to create a bomb.

If only they had a tube of some sort that would withstand the chemical explosion--the one that brought the critical mass together!

He told the Planeteers what he had been thinking, then asked, “Any ideas for a tube?”

“How about a tube from the snapper-boat?” Santos suggested.

Rip shook his head. “Not strong enough. They’re designed to withstand the slow push of rocket fuel, not the fast rap of an explosion. When I say slow, I mean slow-burning when compared with explosive. Any more ideas?”

Kemp, the expert torchman, said, “Sir, I can burn you a tube into the asteroid.”

Rip grabbed the Planeteer so hard they both floated upward. “Kemp, that’s wonderful! That’s it!” The details took form in his mind even as he called orders. “Dominico, tear down that bomb. Santos, remove two heads from your rockets and wire them to explode on electrical impulse. Kemp, we’ll want the tube just a fraction of an inch wider than a rocket head. Get your torch ready.”

He took the stylus and began calculating. He talked as he worked, telling the Planeteers exactly what they were up against. “I’m figuring out where to put the charge so it will do the most good, but my data isn’t complete. If our homemade bomb goes off, I don’t know exactly how much power it will give. If it gives too much, we’ll be driven so close to the sun we’ll never get free of its gravity.”

Bradshaw, the English Planeteer, said mildly, “Don’t worry, Lieutenant. If it isn’t the solar frying pan, it’s Connie fire.”

A chorus of agreement came from the other Planeteers. “What a crew!” Rip thought. “What a great gang of space pirates!”

He finished his calculations and found the exact place where Kemp would cut. A few feet away from the spot was a thick pyramid of thorium. That would do, and they could cut into it horizontally instead of drilling straight down. He pointed to it. “Let’s have a hole straight in for six feet. And keep it straight, Kemp. Allow enough room for a lining of nuclite. Koa, cut a sheet of nuclite to size.”