Astrotwins — Project Blastoff (7 page)

“What kind of critters, I wonder?” Barry said as they made their way carefully across the wood floor, expecting at any moment to trip or bruise their shins.

“Mice, I guess, or bugs,” Scott said.

“Or rats or spiders or
werewolves
!” said Mark, and at that very moment there was a rattling sort of flutter high above, near the far-off ceiling, and an instant later a disturbance in the air announced something was swooping in the shadows above them.

Make that some
things
—lots of them—that were squeaking as they flew.

“Bats!” shouted Barry.

“
Vampire
bats!” said Mark.

Both boys ducked and covered their heads. Scott, meanwhile, waved his arms to drive them away. “I don't even think vampire bats are for real,” he said.

“Real or not, are they gone?” Barry peeked out from behind his hands.

“I don't hear them anymore, at least,” said Scott. “Come on. The chain for the light's
around here someplace.”

A moment later, Scott's hand brushed the chain; then there was a click and a stuttering flash as the fluorescent tubing lit, casting a greenish glow over a large expanse in the middle of the room while leaving the edges and corners in shadow. With the bats and the darkness, the barn had seemed haunted. Now the harsh light and electric hum made it seem more like a mad scientist's laboratory.

But at least the boys could see. And what they saw
was
inspirational. In the well-lit center of the space were three workbenches stocked with tools, and several rows of shelving units, some stacked with paint and solvents but most with bins full of parts from every kind of machine.

In the shadows lay old and broken machines themselves—stuff anybody else would have called junk but that Grandpa called unexploited treasure. These included appliances, lawn mowers, and air conditioners.

“Is there a kitchen sink?” Barry asked after he'd had a chance to look around.

“Of course!” Mark pointed to a white porcelain fixture lying upside down, its silver pipes exposed.

“If we can't build a spaceship out of all this stuff, then we can't build one at all,” Scott said.

“All this stuff . . . and Howard's computer,” said Barry. “We will need a lot of computing power to plot the route
and do the flying.”

“The astronaut does the flying,” said Mark. “Doesn't he?”

Scott said, “Or
she
,” but only to annoy his brother.

Mark ignored this, and Barry said, “Not really. The astronaut has to override the computer if something goes wrong, but the computer autopilot is programmed to handle the navigation and, responding to sensors in the gyroscope, to keep the capsule stable.”

The boys were all set to do some more exploring when Grandpa showed up in the doorway. By now the sky outside was dark silver, and stars twinkled behind his black silhouette. It was getting late.

“Dinner is served,” he announced.

“I can't wait to call Egg,” said Mark.

“And Howard,” said Barry.

Scott sighed. “I guess there's no getting around Howard,” he said. “We have to have that computer, not to mention what he knows about it.”

“Tomorrow we meet right here,” said Mark. “And we start building!”

Only it turned out they weren't as well prepared as they first thought.

Even with all the resources in Grandpa's workshop, there was still material they needed, most important the very first thing the twins had put on their list: metal. What they were hoping for was lightweight titanium for the interior and heat-resistant nickel alloy for the outer shell. Those were the materials NASA had used for the Mercury capsules.

“Maybe we should start with the interior instead,” Egg suggested. It was the following morning, and she was on the telephone with Mark. “Like, we need an instrument panel and a seat and seat belts, too. With no seat belt, the astronauts will float away.”

Mark noticed she'd said “astronauts,” plural. Unlike the twins, she seemed to think everyone who wanted to could still get a ride on the spaceship. Mark didn't want to argue. It was better if all of them were eager to work, and maybe they wouldn't be so eager if they realized
he
was the only one who would get to go up in space.

“Grandpa probably has an old tractor seat, but no seat belts and nothing like an instrument panel,” he said.

“What about if we use a dashboard from a car?” Egg said. “Oh—and we can use a speedometer, too. In a car it measures speed by how fast the axle is rotating. Spacecraft don't have axles, but maybe there's a way to hook the speedometer to the guidance system to get the data, then recalibrate the numbers.”

Mark mouthed the word “recalibrate,” then tilted his head so Barry would know it was a question. Barry answered in a whisper, “It means to adjust to a different kind of measurement.”

Mark nodded, then said into the phone, “Sounds good, Egg. But where do we get those things?”

“Don't you worry,” Egg said. “I have an idea. Howard and I will see you this afternoon.”

*  *  *

Grandpa had been right about the state of the workshop, and the boys spent the morning cleaning. “This is not exactly what I pictured when we thought up the idea
of building a spaceship,” said Mark, who was high on a ladder, knocking down cobwebs with a broom.

Scott, kneeling to corral dust and other crud in a dustpan, protested. “
Hey!
Watch where you knock down those spiders, wouldja? I think I've got a creepy-crawly in my hair!”

“Maybe he'll comb it for you, for once,” Mark said.

“Look out below!” Barry cried, jumping from the top of the stepladder he'd been using to dust shelves. A moment later the hinges on the human-size barn door squealed and a girl's voice called, “Hello-o-o-o?” Then, “Yikes, it's like
magical
in here!”

“Do you think so?” Scott looked around. It was definitely a lot cleaner than it had been the previous evening, and the sunbeams that filtered through the walls seemed more jolly than eerie. Also, the bats were gone, or possibly asleep and out of sight.

“Come and help us unload,” Egg said.

Parked outside was a blue commercial truck labeled
NANDO'S AUTO REPAIR
. A man was handing a car's old bench seat to Howard, who didn't look so sure about receiving it. Mark hurried to help him.

It was another hot day, and the man wiped sweat from his brow, then stood up straight and grinned. Egg opened her mouth to make introductions, but he spoke first. “I am Nando Perez, owner of Nando's Auto
Repair. And you are?”

Mark, Scott, and Barry introduced themselves. “This is really nice of you,” Mark said.

“
De nada
—don't mention it,” said Nando. “My company is one of the sponsors of the science fair. This looks like a very ambitious project! I can't wait to find out what it is you're building.”

Now the truck's passenger door opened, and Lisa, the girl they had seen yesterday, jumped out.

“Meet Lisa, everybody,” Egg said. “She's going to help us, too.”

Scott and Mark looked at one another, both thinking the same thing: Who said it was okay for Egg to invite another kid? But they didn't want to be rude to Lisa, who looked like she was kind of shy anyway, so they smiled and said “Hi.”

One benefit of having a lot of helpers was that it didn't take long to unload the truck.

“Thanks, Mr. Perez,” Egg said when they were done.

“What else do you need?” he asked.

“Sheet metal,” she said, “if it's not too much trouble.”

“I'll see what the junkyard has available,” said Nando.

“We really appreciate it,” Egg said. “But how do we pay you back?”

“With a blue ribbon from the science fair,” Mr. Perez said.

Egg grinned. “That is a deal.”

*  *  *

Mark and Scott were showing the other kids around the workshop when Grandpa came out to see if anybody wanted lunch.

“Me!”
Barry, Scott, and Mark chorused.

“Whoa, Nellie!” Grandpa looked around. “You boys have sure done some good work on the cleanup.”

“You're telling us,” said Mark.

“Thank you,” said Barry.

“And now we're going to organize our workspace,” said Egg.

“Oh, goody,” said Mark.

Howard looked at Mark. “That was sarcasm, right?”

“Howard, my boy.” Mark clapped him on the back. “You are catching on.”

“She means we organize our workspace
after
we eat lunch,” said Scott. “Grandpa Joe? It's not more peanut butter and peppers, is it? I would never whine, you know that, but . . .”

Grandpa laughed. “I've got cold cuts today. And lemonade. And there might be some cookies in the cupboard.”

The kids ate outside. Scott counted, and Lisa said exactly eleven words: “It's nice to meet you, Mr. McAvoy” and “Thank you, Mr. McAvoy.” If she was going to be part of this group, he thought, she was going to have to learn to speak up a little. In comparison, Howard was
downright chatty when you got him on the subject of computers and math.

“I've been working on the control program, but I still have a lot of math to learn about orbital mechanics,” Howard said. “One thing I realized is that we'll save fuel if we launch directly to the east. Earth rotates eastward at roughly 1,000 mph, which means that effectively, the spaceship on the launchpad is traveling that fast, too.”

“And so are we, for that matter,” said Barry.

Howard thought for a moment and nodded. “Yes, I suppose that's true.”

“Weird,” said Mark.

“Anyway, that is effectively 1,000 mph worth of fuel we don't have to use. Saving fuel saves weight, which in turn saves fuel . . . .”

“The rocket equation,” said Jenny. And then she said something both Mark and Scott found incomprehensible: “Change in velocity equals exhaust velocity times the natural logarithm of the initial mass divided by the final mass.”

Scott looked at his brother, and his brother said,
“What?”

“Maybe it would help if I wrote it down,” Jenny said. She pulled a pencil from her pocket and wrote on the
back of a napkin:

“Oh yeah.” Mark nodded sagely. “Sure. Now I get it. Perfectly clear.”

“Why didn't you just say that before?” Scott asked.

“Sarcasm again?” Howard said. “Because she did say that before. The change in velocity equals the—”

Mark held up his hand. “Really, Howard. Repeating it won't help. What are you math nerds talking about?”

Jenny's and Howard's expressions said:
It's so totally obvious, there is no other way to explain it.
But Barry raised his hand. “I can give it a try. A Russian math teacher developed this equation. It describes the rocket's velocity as the fuel burns up and shrinks its mass. His name was Tsiolkovsky—Zy-ol-
koff
-skee.”

“Oh!” said Scott. “So it's in Russian? No wonder we don't understand.”

Mark rolled his eyes. “Math is a universal language, dummy. Uh . . . , isn't that right, Barry?”

“More or less,” said Barry. “Now shut up—excuse me,
be quiet
—and I will explain. So you guys get velocity, right? It's the speed of something in a particular direction. And that little triangle is a delta sign, which means change. So the left half of the equation is change in velocity. Are you with me so far?”

Scott and Mark nodded.

“So the other half of the equation is the exhaust velocity—in other words, how fast the exhaust is spewing out of the rocket's nozzle. You multiply that times the
initial mass of the rocket, which includes the fuel in the rocket, and then divide it by the final mass of the rocket, which is what's left after the fuel has burned off. Then that number gets multiplied by the natural log function, and it equals the change in velocity—the left part of the equation.”

A lightbulb flashed in Mark's brain. The bulb was only about as big as a firefly, but it was definitely switched on. “So the rocket flies, and as it flies, its mass shrinks because part of its mass was fuel that has burned off in the exhaust?” Mark said. “And as the mass gets smaller, there is less fuel available but, at the same time, it takes less fuel to propel it. Is that right?”

“Yes!”
said Barry.

“But what's this natural log business? It sounds like it has something to do with a fireplace,” Scott asked.

“In this case it's a constant to describe something that changes continuously over time,” Barry said. “So the mass of the fuel is changing and affecting the velocity not just moment by moment, but also all the moments in between. The natural log is a mathematical way to describe that.”