Critical Mass, page 42
DAYS TO RYUGU DEPARTURE: 554
RESOURCES LAUNCHED TO L2: 83,400 TONS
The board of Catalyst Corporation convened around a new table with a surface of sintered and polished lunar regolith. James Tighe, Priya Chindarkar, Jin Han, and Sevastian Yakovlev were physically present, while an augmented-reality projection of Lukas Rochat in Luxembourg City was beamed in from Earth on a few-second delay.
They all stared at a virtual spacecraft floating above the table, while Yak addressed them. “I took to heart issues raised regarding previous design, and this new concept requires greatly reduced mass, while still satisfying all mission requirements.”
Chindarkar said, “It certainly looks more reasonably sized.”
“Da. It uses one-third the fuel of first design.”
“Outstanding. I’m impressed you were able to reduce it that much.”
Jin asked, “Lunargistics worked with you on this design?”
“No. Julian and I worked with new company out of Czech Republic. A firm called Star Power. They have designed spacecraft for both ESA and private European aerospace firms.” He rotated the model. “No such spacecraft has combined these features before. However, we will obtain experts necessary to—”
“Do you have a cost estimate?” Rochat interrupted, possibly due to transmission delay.
Tighe cast an annoyed look in his direction. “Relax. He’ll get to the cost.”
Yak turned back to the model. “Spacecraft has overall length of 128 meters, and carries 712 tons of fuel.” He highlighted each section of the model in turn. “Propulsion, two in-line fuel tanks, star-truss module, which contains avionics and life support module. Mounted around this star-truss are four 100-ton drop tanks. Solar and communications array, docking ports, and finally, tensegrity structure containing spin-gravity crew habitats.” He animated the model so that the habitat ring expanded origami-like from a solid ring not much wider than the four external drop tanks into four trapezoidal wedges linked to the ship’s axis by unfolding trusses, which locked into place to complete the ring. Connecting each of the four habs were narrow telescoping tunnels. Yak retracted the habs and repeated the expansion and contraction several times.
Chindarkar smiled. “That’s elegant. Much better than the Konstantin.”
Jin pointed. “Those connecting tunnels between the habs, they’re pressurized?”
“Da. You can move from hab to hab while spun-up.” He looked up from the model. “However, radius of rotation is only 80 meters. Nonetheless, we expect a crew well-conditioned to life aboard Clarke Station will be able to cope with Coriolis effects sufficiently for two-month mission.”
Jin asked, “And propulsion?”
Yak paused a moment before expanding the model and zooming into four rocket engines arrayed as nodules around the stern of the craft. A label appeared near the edge of the model. “Craft is designated NTR-01, meaning nuclear thermal propulsion.”
Jin frowned. “Nuclear?”
Yak held up his hand. “USSF has Conestoga-class spacecraft. Russia and China have—”
Rochat said, “We’ve already received expressions of concern regarding our stockpile of uranium from the board of governors of the International Atomic Energy Agency. That’s thirty-five nations.”
Tighe said, “Can we please hear what the design is first?”
Rochat relented.
Yak continued, zooming into a cutaway view of a single engine. “NTR-01 is powered by four 3-ton, 500-megawatt, trash-can-sized nuclear propulsion engines, each containing roughly 50 kilograms of uranium—”
“Fifty kilos each!”
Tighe said, “This is going to be a long goddamned meeting if you keep interrupting.”
Jin turned to Tighe. “How many kilos of uranium do we currently have?”
Yak answered. “Eighty-two. However, we will have more than sufficient supply a year and a half from now.”
“You do not seriously intend to enrich that uranium.”
Yak breathed in. “We will use standard HALEU fuel—high-assay low-enriched uranium.”
Chindarkar frowned. “And what is that?”
“Enriched to between 5 percent and 19.75 percent. Which is below weapons grade.”
Rochat asked, “And what percent does your engine require?”
Yak winced. “Nineteen point seven five percent.”
“And you propose to start building centrifuges and enriching uranium—on Clarke Station?”
Yak looked to Rochat. “You make it sound nefarious.”
“Even if we got approval, there would need to be UN inspectors monitoring the enrichment—and that’s if we got approval, which I doubt we will.”
Tighe turned to Rochat’s spectral image. “No one said we’re asking approval for anything.”
Chindarkar said, “J.T.—”
Yak held up his hands. “May I please complete presentation? At least then we will know what we are arguing about.”
The room grew quiet.
“Spasibo.” He turned back to the model, highlighting the reactor core. “Engine has ‘cercer,’ or zirconium-carbide-fueled, beryllium-moderated reactor core. Of this, only beryllium would need to be sourced from Earth. We can obtain or synthesize all other materials from lunar regolith.” He looked up. “Each engine would have specific impulse greater than 950 seconds—over double efficiency of any chemical rocket. Delta-v of roughly 15 kilometers per second.”
Jin nodded. “Wow.”
Chindarkar whistled.
“Body of this engine would be made of tantalum-hafnium carbide ceramic, with melting point of 7,208 degrees Fahrenheit and working temperature of 6,020 degrees Fahrenheit. It can be manufactured in situ, since we have refined sufficient hafnium and tantalum from lunar regolith.”
The model animated as the nuclear reactor lighted.
“Propellant would leave rocket nozzle at 10 kilometers per second at this temperature.” He gestured and additional piping appeared outside the engine. He looked up again. “But with addition of O2 afterburners, we can increase thrust by 62 percent—although this would lower fuel efficiency, reducing specific impulse to 700.”
Jin stared at the model, clearly impressed.
“Is drag racer, yes?” Yak pointed at a fuel tank. “Hydrogen is ideal propellant, but ammonia is ideal fuel—of which we still have 600 tons, plus 720 more tons if Amy Tsukada tug arrives on schedule.”
Jin said, “How many times do I have to say—?”
Tighe said, “Fine. Then we pay to have the ammonia we need launched up to us from Earth.”
“Which would cost a fortune and require cooperation from Earth authorities.”
Chindarkar asked Yak, “If hydrogen is the best propellant, why do you want ammonia for the fuel?”
“Saves us difficulty and mass of maintaining liquid hydrogen—ammonia consists of three atoms hydrogen, one of nitrogen. We extract hydrogen on demand via electrochemical cell with proton-conducting membrane integrated with nickel calcium amide catalyst. Ammonia splits into nitrogen and hydrogen efficiently at a temp of just hundreds of degrees—easily done near reactor.” Yak then turned to his audience. “Other questions?”
Rochat said, “Yes. Are you insane?”
“Any sensible questions?”
Rochat continued. “You’re planning on enriching uranium—the very thing the Russians, Americans, and Chinese have already expressed grave concern over.”
Tighe said, “Because they want the uranium for themselves. We’re not doing anything wrong. We’re trying to rescue our friends, not build weapons. We should just do this.”
“Concealing uranium enrichment is a really bad idea.” Chindarkar hesitated for a moment, then said, “J.T., we’ve only just recently commenced stable relations with the international observers. As hard as it may be to accept, enriching uranium is potentially going to bring a strong international call for us to be put under external control. And if that succeeds, how would we even launch a rescue mission?”
Jin clenched his jaw, then turned to Tighe. “Priya is right that the world is not going to just sit by while we become a nuclear power. This will require delicate negotiations. And inspections.”
Rochat added, “Things are going very well up there lately. Don’t forget how important the CCE is to the future of civilization. People down here on Earth are pulling CO2 from the air in order to earn lūna to invest in the off-world economy. That will make a huge difference against climate change. But we’ve all seen what happens here on Earth to nations that start enriching uranium in pursuit of nuclear weapons. They—”
Tighe shouted, “We’re not pursuing nuclear weapons!”
Chindarkar held up her hands. “The world won’t know that. We need to engage with the international community first to be sure they do know what we’re up to.”
Rochat said, “Even if they allow it, there will need to be IAEA inspections.”
Tighe said, “And how long will it take to organize that? Are the necessary people even launch certified?” He gestured toward the model. “We should start planning to construct this ship. We’ve only got a year and a half until Ryugu arrives.”
Jin said, “There is still time. I think we should table this until we determine how it will be received by the international community.”
Tighe shook his head. “We can’t wait.”
“J.T.—”
“At the very least we should commence building the body of the ship. If not the reactors, then the superstructure, plumbing, and crew quarters.”
“Which will be an enormous waste if we don’t obtain international approval.”
Tighe stared. “Then I suggest we make certain to get that approval.” He pointed at the model. “Because this is the ship we need to reach Ryugu.”
Yak piped in. “I agree with J.T. We should commence construction of spacecraft superstructure—otherwise, we may run out of time.”
“But we hold off on building the engines and enriching the uranium?” Chindarkar ventured.
Tighe sighed.
Jin said, “If we obtain the necessary approvals, only then do we proceed with uranium enrichment.”
Tighe looked around the table. “But in the meantime we commence construction of the spacecraft superstructure. Correct?”
The rest of the board nodded.
Rochat said, “Very well, I move that we commence construction of the non-nuclear portions of the NTR-01, but hold off on the reactors and the fuel until I can sound out Earth authorities on the issue of uranium enrichment in deep space.”
Tighe objected, “Don’t put it like that. Context is important. Tell them we just want reactor fuel. We’re not making weapons.”
“Votes in favor?”
Everyone present raised their hands.
“Then the motion passes unanimously.”
* * *
—
As Tighe and Yak walked to the elevator, Tighe said, “I have renewed appreciation for what Joyce—scumbag though he was—managed to accomplish back on Earth.”
Yak nodded. “I often think this.”
Tighe looked behind them to determine they were alone before leaning close and saying, sotto voce, “Out of curiosity, Yak—what’s involved in enriching uranium?”
Yak glanced around as well, and seeing no one, nonetheless leaned closer still. He spoke softly. “First: avoiding detection. Much easier out here.”
“And the enrichment—could that be done in situ?”
“Da.” He paused. “Process involves leaching uranium in sulfuric acid—which we have—to create uranium oxide liquid. Uranium is then pulled out of solution using ammonia—which we also have. This creates a ‘yellowcake’ powder—almost entirely U-238 isotope. But we must isolate the 0.7 percent that is U-235—which is what we need for reactor.”
Tighe tried to read Yak’s expression. “And we can do all that?”
Yak nodded. “By transforming yellowcake into gas with fluorine, of which we have small supply on board for refrigeration. Resulting uranium hexafluoride gas is put into specialized centrifuge, where differing mass of isotopes separates them after repeated cycles.”
“Could we build this centrifuge?”
“Centrifuges—and yes, we could. When finished, enriched U-238 is then transformed from gas back into solid by adding calcium—which we have in abundance. Calcium reacts with fluoride to create a salt and leaves behind only U-235 oxide, which is then heated and extruded into U-235 fuel pellets. Our end product.”
“How long would all this take?”
“Once equipment is set up . . . some months.”
They regarded each other.
Tighe finally whispered, “Like Joyce always said, Yak: better to ask forgiveness than permission.”
CHAPTER 39
Monster
CLARKE STATION POPULATION: 137
DAYS TO RYUGU DEPARTURE: 493
RESOURCES LAUNCHED TO L2: 102,300 TONS
James Tighe and Sevastian Yakovlev sat in an open workspace in the sparsely furnished Catalyst Corporation offices in West Hab, listening to a Czech nuclear propulsion engineer named Oleg Gusev speak over a virtual videoconference line back to Earth—the screen projected into their crystal headsets.
Tighe spotted Jin Han approaching at a fast walk, Kerner with him.
Yak interrupted Gusev. “Oleg. Terribly sorry. We must go. We will call you soon.” He cut the conference line as Gusev tried to say something in response. Yak dismissed the screens just as Jin leaned into the room.
“Follow me to the ops center. This is an emergency.” He headed down the hall.
Tighe and Yak jumped up and followed him.
Tighe asked, “What’s up?”
Jin instantiated a shared virtual screen as they walked. It showed a shadowed image of the Sun. “Space Weather Prediction Center reports a monstrous coronal mass ejection, and it’s headed directly at the Moon. They estimate it will reach us in fifteen to eighteen hours.”
“How bad are we talking?”
“Big—an S5 solar storm. Much bigger than the flare we experienced out at Ryugu. An explosive outburst of solar wind plasma—a billion tons of charged particles going up to a few thousand kilometers per second. Powerful magnetic fields. We’ll know just how big when the bow shock of the storm passes the Deep Space Climate Observatory at SE-L1. Depending on how much energy is behind those particles, at that point we’ll have anywhere from fifteen minutes to an hour until it hits us.”
Just then they entered the ops center, a control room of desks arranged in a circle, facing out toward a swarm of virtual screens. Half a dozen CCE and Catalyst staff manned the workstations.
Yak said, “What do you need from us?”
“Yak, go help Priya. She is working with mission control and the telepresence teams to reposition supply yard mass. We can’t move a hundred thousand tons between us and the Sun, but whatever we can deploy as a shield before it hits will help.”
“That will degrade the thermal power plant.”
Jin nodded. “I know, but every system on this station needs to be powered down before that storm hits. We’ll be running on emergency power only—and even then, as little as possible.”
Tighe recalled the solar flare that hit the asteroid Ryugu after Amy Tsukada’s funeral. If it had caught them in the open, they would all have been dead. Fortunately Ryugu shielded them. However, Clarke Station had no such protection and was in almost constant view of the Sun—handy for creating energy with a thermal power plant, but not so great at moments like these.
Jin was checking virtual screens. “We’ll concentrate most of the supply yard mass directly in front of Clarke Station’s core—shielding the power plant and the refinery as well. That’ll leave the spin-gravity ring lightly shielded. So I’ll order everyone on station into the core.”
Tighe said, “But we’ve got well over a hundred people on board. How many do you think we can fit in the core compartment?”
Yak answered, “They will fit. It does not matter if it is tight.”
Just then Professor Lynne Holstad entered the ops center and spoke matter-of-factly. “Captain, you wished to see me?”
Jin looked glad to see her. “Yes, Lynne. What’s the status of your radiotrophic fungi project?”
“I can have one of my assistants get you—”
“I need best estimates. Now. How much protection does it give us?”
She paused. “We have . . . ten screens of approximately 1.7 millimeters within the double hull. It blocks probably 90 percent of incoming radiation—although, GCRs are—”
“Good! That is good.”
Yak said, “Your fungi are about to get all-they-can-eat buffet.”
She looked at him quizzically.
Jin said, “A major radiation storm is predicted to hit us by day’s end. I’ll be making an announcement, but get your people ready. We can expect a trail of energized protons in this storm’s wake; complete communications disruption—no telepresence with our mules and other spacecraft. No comms with Earth. With a storm of this magnitude, we’ll need to shut down just about every computer system—except the most critical and most shielded. Otherwise there will be bit flips, latchups, burnouts.”
“I need to move as many plants as possible to shelter.”
Yak said, “There is 10,000-liter ‘on-demand’ water tank near base of elevator columns—where piping runs into station ring. You could shelter plants behind this.”
“All right. We’ll get busy . . .” She left the ops center in a hurry.
Yak turned to Jin. “Solar panels facing the storm will take damage. We must make sure all solar panels on spacecraft and satellites are turned away from Sun before CME hits. Daisy most specially.”
Jin nodded. “Priya, did you hear that?”
