October 4, 2034
Earth Departure Minus Six Months
16:05 Universal Time
Marshall Space Flight Center, Alabama
“. . . and that’s the NTR, behind the shadow shield,” Benson was saying.
He and Treadway were in a huge, hangarlike building where the full-scale mockup of the Arrow spacecraft was spread across the concrete floor: a big rocket nozzle at one end, bulbous tankage, square panels the size of baseball diamonds, all connected to a long, metallic ladderlike central boom.
Four different TV miniaturized cameras were floating across the floor beneath toy-sized ballons of helium, automatically following their progress along the length of the mockup, with a fifth camera unit hanging up near an overhead truss that ran the length of the cavernous building.
Around the world, viewers who had the new three-dimensional home theaters didn’t merely watch a screen, they could step into the scene along with Treadway and Benson, walk along the length of the spaceship beside them.
“NTR?” Treadway asked. He knew the initials stood for nuclear thermal engine, but the VR Net audience wasn’t familiar with NASA’s bewildering jungle of acronyms.
“Nuclear thermal rocket,” said Benson, his voice flat, no trace of annoyance in it. “The nuclear reactor heats hydrogen gas to three thousand degrees Fahrenheit and the hot gas is fired through the rocket nozzles. That’s what gives us the thrust we need for TMI.”
“Trans-Mars Injection,” Treadway translated the NASA acronym.
Looking halfway between embarrassed and irritated, Benson explained, “Right. That’s when we break Earth orbit and head for Mars.”
Making a slightly worried frown, Treadway said, “A nuclear rocket? Isn’t that dangerous?”
Benson shook his head. “The Russians have flown dozens of nuclear power systems over the years. With the NTR we only have to carry half the propellant that we’d need with chemical rockets. It’s got twice the specific impulse of the best hydrogen-oxygen rockets. It’s actually a lot safer with the nuke, saves us months of travel time.”
Suppressing a wince at the word “nuke,” Treadway forced a smile as Benson pointed out the ship’s propellant tanks, the payload section that held the smaller vehicle that would actually land on Mars, the square flat panels of the radiators that got rid of the ship’s excess heat and the bigger, darker oblongs of the solar panels that would generate electrical power for the spacecraft.
“Why the solar panels?” Treadway asked. “Doesn’t the nuclear reactor generate electrical power?
With a shake of his head, Benson replied, “The reactor is for propulsion only. It’s not bimodal. The engineers decided it would be too expensive and complicated to make it do both.”
They slowly walked along the length of the spacecraft, the floating cameras following them, while Benson explained each segment of the ship.
“How long is this bird, anyway?” Treadway asked.
“Two hundred meters, from the end of the main thruster nozzle to the tip of her nose,” said Benson.
“Two hundred meters . . .”
Benson’s lips twitched in what might have been a smile. “That’s right, you Americans aren’t accustomed to the metric system.” He frowned in silence for a moment, then said, “It’s roughly six hundred and fifty-six feet.”
“About an eighth of a mile.” Treadway grinned, a trifle smugly. I can do arithmetic in my head, too, he told Benson silently.
Smiling back at him, Benson said, “Yes. Almost two and a half football fields.”
As they neared the spacecraft’s front end, Benson pointed to the metal gridwork boom that held the various attached components.
“The truss is the ship’s spine,” he explained. “It’s got to be strong, yet light.”
Playing the straight man, Treadway asked, “What’s it made of?”
“MWNT,” answered Benson. Before Treadway could respond, he explained, “Multi-walled carbon nano tubes. Four times stronger than the best metal alloys, yet lighter than any of them.”
“Nano tubes?”
“Like Buckeyball fibers.”
“Oh.”
At last they reached the habitation module, a smallish cylinder near the front end of the spacecraft.
“Eight men and women are going to live in that little bubble for nearly two years?” Treadway prompted.
“It’s not that little,” said Benson. “There’s a privacy cubicle for each member of the crew, plus a wardroom, control center, workshop and labs, and an observation blister.”
“Can we go into the habitation module?”
On that cue, Benson replied, “Not the one in the mockup, up there. But we have another mockup of the module by itself, over there.” He pointed across the floor. “We can go inside that one.”
“Cut!” cried the director, from behind the monitor set up in the corner of the hangar. “Take ten and re-spot the cameras. We’ll pick it up inside the module.”
Treadway gave Benson a reassuring pat on the shoulder. “You’re doing fine. Great.”
Benson grimaced. “I’d rather have a root canal.”
The director pressed his hand against the communications bud in his ear, then said to Treadway, “New York’s happy. They think we’ll getthe biggest chunk of VR Netviewers when this airs tonight.”
Treadway broke into a genuinely pleased grin.
It was a tight squeeze inside the habitation module, with three of the cameras bobbing along with them. The director had squeezed into the module, too, telling them he wouldn’t miss this opportunity—at least not for anything less than an Emmy award.
The module was compact, but efficiently laid out. Benson showed them the control center, with its consoles and display screens, the workshop and minuscule laboratory for the two geologists and their one biologist. Then they went a few more steps back, to the wardroom.
Treadway looked at the circular table and eight chairs.
“Chairs? They don’t have chairs in the International Space Station. And the tables are chest height.”
Benson explained, “That’s because the ISS is in microgravity. Zero-gee, just about. You don’t need chairs. You just stand at the table and hook your feet into the floor loops to keep from floating away.”
“Won’t the Arrow be in zero-gee?”
“Only while we’re in Earth orbit. Once we start the TMI burn—” Before Treadway could interrupt, Benson explained, “Once we break orbit and start for Mars, the ship will rotate end-over-end to give us a feeling of one-third gee during the trip.”
“One-third gee?”
Nodding, Benson said, “That’s the level of gravity on the surface of Mars. Rotating at one-third gee all the way out means that the crew won’t suffer from muscle atrophy and calcium loss in their bones the way we would if we were in zero-gee all that time.”
“And when you land on Mars you’ll be accustomed to the gravity level there.?
Benson smiled slightly, like a teacher rewarding a student for a correct answer. “That’s entirely right. You’ve got it.”
Treadway beamed happily.
The individual privacy cubicles were about the size of telephone booths, big enough for an air-filled mattress fastened to one wall, a display screen on the wall opposite, and a modest closet on the third wall.
“There’s a laundry further down the passageway, right beside the lavatory,” said Benson.
Staring at the inflated mattress, Treadway asked, “You’ll sleep standing up?”
Benson broke into an amused chuckle. “When we’re in orbit and effectively weightless, the orientation of the bed doesn’t matter.”
“But when you’re rotating to give you one-third gravity . . . ?”
Pointing, Benson said, “That ‘wall’ will become the ‘floor.’”
“Oh,” said Treadway.
Raising one long arm, Benson pressed his fingers against the springy surface of the habitat’s curved ceiling.
“This module is made of fabric, coated with metal on the outer skin. It’s double-walled, and filled with water for protection against radiation.”
“Water?”
“Water can absorb radiation coming in from space. Even if the sun puts out a coronal mass ejection while we’re in transit—”
“You mean a solar flare?”
Slightly annoyed, Benson replied, “That’s the layman’s term for it. A coronal mass ejection belts out a cloud of very high-energy subatomic particles. Plus gamma rays and x-rays. Very dangerous.”
Poking at the slightly flexible wall, Treadway asked dubiously, “And this layer of water will protect you from that?”
With the ghost of a smile, Benson answered, “So the scientists tell us.”