Delta-v, page 28
After several minutes the pressure vessel cooled, then spun like a washing machine, flattening the material into a blur against the circular wall.
“The volatiles will be condensed into a liquid and piped to storage for later purification.”
The pressure vessel stopped spinning, and soon the powder began to float again.
“At this point we begin a process called ‘beneficiation’—which simply means concentrating the mineral content in the ore. This will also extract the more stubborn volatiles. I begin by pressurizing the vessel with pure hydrogen . . .”
The particles in the vessel swirled around violently.
“. . . and cranking up the heat to 800 degrees Celsius.”
The powder in the vessel began to swirl once more.
“The final volatiles extracted here include hydrogen, carbon dioxide, sulfur, nitrogen, hydrocarbons, chlorine, sulfuric acid, hydrochloric acid—but also amino acids; organic compounds that will prove useful. I’m removing all of these for later filtration as well.”
By now the pressure vessel on-screen was an orange, swirling cloud of gas and particles. Tsukada left it that way for several minutes, and then the heat dropped as the vessel again spun rapidly—extracting the gas mixture through centrifugal force. When the walls stopped spinning, much less material remained and some of the particles now had a metallic sheen.
“The regolith mass is now 42.13 kilos—about half what we started with. We performed the heating in an atmosphere of hydrogen to allow the organic molecules to react with magnetite in the ore. This released two very useful gases—carbon monoxide and carbon dioxide—but notice that it also produced what’s called ‘free metal,’ the concentrated iron you see glittering in the powder.”
Tighe studied the screen. The material in the vessel was far different from the gray asteroid dust with which they began.
“What we have now is an involatile residue—about one-third iron-nickel-cobalt alloy, which we need to purify still further through an acid leach. . . .”
On-screen, globules of liquid were injected into the vessel; they immediately reacted with the powder, bubbling violently. The heat rose again to several hundred degrees Celsius as the vessel began to spin, flattening the powder against the walls while the reaction accelerated.
“We can use acids obtained from earlier steps in the refining process to make this process sustainable long term. The reactions you’re seeing are extracting phosphorous, sodium, potassium, calcium, and magnesium, all of which we can use.”
The reaction continued on-screen until the vessel began to fill with smoke.
“White fumes indicate the process is nearing completion, and we again filter and store these compounds for later purification.”
After a while the vessel stopped rotating.
“All that remains now of the original regolith is powdered ferrous metals and silicates. We could melt this down, but an iron-smelting furnace is a bad idea on a spaceship. Plus, smelting requires a large amount of energy. Fortunately, there’s another way. . . .”
The temperature in the vessel now plunged to 100 degrees Celsius.
“Gaseous carbonyl extraction involves transforming metal into a gas.”
On-screen, the powder began to swirl again, and pressure in the vessel increased to 2 atmospheres.
“Our ore sample contains three key metals—iron, nickel, and cobalt—all bound to each other. However, when we introduce carbon monoxide into our chamber under precise pressure and temperature, the metals within the ore begin to transform. Nickel reacts first, combining with four carbon monoxide molecules to form nickel tetracarbonyl, a highly toxic gas.”
The pressure in the vessel slowly increased.
“As the temperature and pressure increase, the iron in the ore reacts next, combining with five carbon monoxide molecules to become iron pentacarbonyl, another impressively toxic gas.”
The temperature in the vessel increased still further to 200 degrees and the pressure to 10 atmospheres.
“And now the cobalt combines with eight carbon monoxide molecules to become gaseous dicobalt octacarbonyl, yet another toxic gas.”
The vessel then spun fast, extracting the carbonyl gases from the chamber, and after a minute or so the spin cycle slowed and stopped. Now all that was left floating in the chamber was sandy powder, less than a quarter of the original regolith sample.
“Leaving us with a harmless silicate residue. We can pack this into containers as radiation shielding. However, in coming years, we may be able to economically extract small quantities of platinum-group metals or synthesize silicon, glass, or other useful compounds from it.”
The chamber flushed with air, blowing the sandy powder down a pipe. The entire chamber was now empty.
“At room temperature and pressure, nickel and iron carbonyls condense into liquids, allowing us to pipe them around the refinery or store them without the need to keep metal in a molten state. Cobalt carbonyl becomes a powder at room temperature but returns to gaseous form at 52 degrees Celsius, meaning it, too, can be easily piped around the refinery. Transforming them back into solid metal is also not difficult.”
The video window now showed a surveillance-camera view of Tsukada standing in her lab.
“In short: Ryugu’s regolith is everything we hoped it would be. Now you just need to prove you can get me thousands of tons of it—without killing yourselves or destroying the ship.”
CHAPTER 28
Inertia
Sitting around the galley table in Hab 1, Tighe, Morra, and Clarke stared at a holographic scan of a section of Ryugu’s surface. A large boulder was highlighted in red as the image rotated to reveal its dimensions.
Chindarkar’s voice came in over the comm link. “Muon tomography scanning shows Boulder 4 as the most promising pull candidate.”
Boulder 4, 6 meters in diameter, was egg-shaped, and only a quarter of it was sunken into the asteroid’s surface. The rock looked solid, and its chemical composition was straight out of the Konstantin mission plan.
Clarke stared at the image. “Estimated mass . . . 214 tons. Just about perfect.”
Tighe leaned in next to her. “In Ryugu’s gravity that’s about 30 kilos.”
Morra grimaced. “Too bad about inertia.”
There was a pause as Clarke opened the laser comm channel. “Mission control, we’ve selected Boulder 4 and are ready to move it to a terminator orbit. Please advise.”
What followed was a half-hour transmission-delayed discussion with mission control managers, engineers, and geologists. Eventually Clarke got a green light to pull Boulder 4 from Ryugu’s surface.
Chindarkar activated one of the ship’s two ARS robots after uploading the mission profile into its job queue. The 2-ton robot was shaped like a hexagonal cylinder with twin solar panels resembling mouse ears. It undocked from its perch near the upper airlock and activated thrusters that sent it toward Ryugu’s surface.
As the ARS descended, it unfolded long robotic legs at its front. The legs consisted of interlocking aluminum-frame triangles whose angles to one another were adjusted by linear actuators, enabling them to “curl” like the fingers of a claw in an arcade game—but also to push off a surface. At the moment these legs were bowed out for landing, their base plates extended for impact. On-screen it was hard to tell that this spindly robot was 15 meters tall.
A nearby mule remotely piloted by Chindarkar illuminated the target boulder with work lights as the ARS touched down like a three-legged spider standing around and over Boulder 4. A small amount of dust kicked up as the legs of the ARS flexed to absorb the 1-meter-per-second impact without rebounding back into space.
“ARS 1 has landed over Boulder 4.”
They watched monitors as ARS 1’s scanners made a 3D model of the boulder beneath it, and then a pair of smaller, tool-equipped arms descended from its belly. These began to drill into the rock in several places at opposing angles.
The robot’s onboard cameras offered a close-up of the process. After several minutes drilling a dozen holes, bolt-studded clamps descended into them and held Boulder 4 fast.
“Boulder 4 secured. ARS 1 preparing to push off the surface.”
ARS 1’s legs started bowing outward as the linear actuators tightened, lowering the craft in preparation for its vault away from Ryugu. This design used leverage instead of rocket fuel to move the boulder—which was important when that boulder was two-thirds the mass of the entire Konstantin.
“ARS 1 standing by.”
They had to wait another two and a half hours until Ryugu’s rotation brought the site into sunlight. Once dawn crested on Boulder 4, Clarke gave the order.
Adisa activated the robot. “ARS 1 pushing from surface.”
Suddenly the spacecraft’s tall legs flexed upward—but instead of pushing off Ryugu’s surface, one of the legs thrust through the regolith, sinking meters deep. This caused the ARS to topple as the other two legs pushed—causing the boulder to roll and partly trapping the robot. Regolith kicked up in a huge dust cloud.
Tighe and Morra winced.
Clarke rubbed her face. “Goddamnit!” A long pause. “Dave. J.T.” She looked up. “I need you guys to go down there and unfuck that equipment.”
Morra gave a thumbs-up to Tighe as he answered. “We’ll need a couple hours for the prebreathe. The dust should have settled by then. You want to send the other ARS out to try a different boulder in the meantime?”
“Negative. We’ll hold that in reserve.”
Morra nodded. “Ade, what’s the weather report?”
Adisa answered, “No solar flares predicted.”
Clarke frowned. “Belay that. Let’s play it safe and wait. By 1400 hours, Boulder 4 will be back at the terminator line, and you’ll have another three and a half hours of darkness to work the problem before it rolls into sunlight again.”
“All right. We’ll come up with a plan in the meantime.”
Clarke added, “Han, I want you prebreathed and in the upper airlock when they go out—ready to provide rescue if necessary.”
Jin replied, “I’ll be ready.”
* * *
—
An hour later Tighe, Morra, and Jin floated in the upper airlock, examining live imagery of the Boulder 4 site. The ARS was toppled onto the surface with both its free legs and its rocket motor pointed the wrong way.
Tighe looked to Morra. “Well, Royal Engineer, what’s the plan?”
Morra studied the scene.
Jin pointed. “It is only the one leg that is caught. We could dig it out. The regolith is not dense.”
“I want to stay clear of that regolith if at all possible. It can have up to a two-hundred-volt charge on the nightside.”
Tighe suggested, “How about winching ARS 1 to the side—from another rock?”
Morra pondered this. “It could do more damage.” He thought for a moment. “What if we detach the trapped leg? Then the ARS is just a couple tons to pull away from the boulder in microgravity. We could use a mule for that.”
Jin added, “Then we bring in the second ARS to pull Boulder 4.”
“We should bolt panels to the feet—like snowshoes. To keep it from sinking during the pull.”
With a half hour remaining until Boulder 4 rotated around to them again, Tighe and Morra slipped through the hatches of their clam suits, pressurized, and then undocked from the Konstantin.
Once outside the ship, they grabbed the handles of a mule utility craft remotely piloted by Chindarkar.
Tighe and Morra placed tools and spare gas canisters onto the equipment rack atop the mule, strapping them down with polymer cord. Then they clipped their tethers to eyebolts on the mule before climbing onto the running board.
Tighe rapped on the hull of the mule to indicate they were ready—and it made no noise whatsoever. Neither was Chindarkar actually inside. He rolled his eyes at the mistake and spoke over the radio. “We’re ready, Priya.”
“Next stop, Boulder 4. Mind the gap. . . .”
Thrusters sent the mule heading toward the dark surface of Ryugu.
Tighe noticed the return countdown timer in his crystal display. He looked across the top of the mule at Morra. “Thirty-six hours gone so far.”
Morra drummed his gloved fingers impatiently on the hull of the mule. “Plenty of time left before the return window closes.”
Clarke’s voice came in over the comm link. “Dave, J.T., I don’t need to say this, but be careful down there.”
Tighe answered, “Aye, aye, Captain.”
Suddenly a pressure alarm appeared in Tighe’s crystal display. It was for the Konstantin’s upper airlock.
Tighe glanced back at the Konstantin.
Adisa’s voice came through. “Han, can you confirm a fault in the upper airlock?”
Jin answered, “Stand by.”
Several more pressure alarms activated in the upper transit tunnel. It was starting to resemble an expanding ship depressurization.
Tighe looked to Morra. “That’s crossing two airlocks. Hull failure?”
Morra shook his head in disbelief.
Adisa’s voice: “Air quality still looks fine. This doesn’t make sense.”
“Great.” Tighe muted the alarms. “Tell us when you sort it out. We’re going to need that airlock to get back into the ship.”
“Wilco.”
Chindarkar brought the mule down to 15 meters above Ryugu’s surface, floating over the toppled ARS. In microgravity the asteroid seemed to be straight ahead of them—like a cliff face.
Tighe knew that mission control back on Earth would be watching their transmission-delayed video feed—that Joyce himself was probably watching. He tried not to sense their eyes on him and instead concentrated on the job.
Morra said, “Priya, turn on the work lights, please.”
The mule’s forward lights kicked on, illuminating the entire scene.
Tighe grabbed tools from the cargo rack and clicked them into his chest harness.
Morra activated the mule’s forward winch, paying out cable.
Tighe checked the distance to the surface with his helmet’s laser range finder. “Sixteen meters.”
“Thanks.” Morra clicked the winch line’s carabiner onto his utility belt. “Whenever you’re ready, mate.”
Tighe clipped in to Morra’s harness, linking the two of them. “Let’s do it.”
“Remember: the regolith has an electrical charge. Stay clear of it, or you might short out your suit.”
“Can that really happen?”
“Who knows? But let’s not find out.”
Morra gripped Tighe’s gloved hand as Morra fired his clam suit’s SAFER unit. Cold-gas thrusters brought both of them the short distance across the gap to the toppled ARS and the wall-like surface of Ryugu.
As Tighe bumped into the aluminum hull of the ARS, he reached for one of several maintenance handles built into its side—but missed. The EVA space suit was nowhere near as flexible as his flight suit, and he bounced off, slowly floating back into space.
“A little help . . .”
Morra grabbed a handle and reeled Tighe in by his tether. “I guess I’m the first human on Ryugu.”
Tighe laughed. “Shit, I guess you are.” He spoke into the comm link. “Ade, you writing that down?”
Clarke’s voice replied instead. “Please concentrate—the both of you.”
Morra unclipped the winch line from himself and clipped its carabiner onto an eyebolt on the toppled ARS. He gestured to the mule’s camera. “Priya, carefully take up the slack on this cable.”
They both moved aside and clipped their tethers to the ARS. Tighe then moved hand over hand along the hull of the ARS until he reached the base of the leg trapped under Boulder 4. This close, the boulder was the size of a small house and the robot not much smaller.
“Wait a sec.” Tighe held up his gloved hand. It was somehow coated with fine black iron filings. They stuck to him like magnets. “Christ, I barely brushed the surface of the boulder and got my whole glove coated.”
“Any electrical shock?”
“No. I guess the suit’s a poor conductor.” Tighe examined his glove closely under the helmet-mounted work lights. The regolith consisted of prickly splinters. It was almost impossible to believe these mineral hydrates contained water. They looked the opposite of life-giving—more like a magnified virus. His helmet-mounted camera, he knew, would be relaying the image back to the ship. “This is some evil-looking shit. I don’t want to get buried to my waist in this. The suit would probably get compromised pretty quickly.”
Morra said, “Ade, just for the record books: J.T.’s now the first human being to touch an asteroid.”
Tighe stopped and was surprised this hadn’t occurred to him. He turned and smiled at Morra. “Hey, Ade, we should write these on the hab wall.”
Clarke’s voice came through. “There are going to be a lot of firsts on this expedition. Let’s try to focus on the job, please.”
“Right . . .” Tighe pulled a can of compressed CO2 from his harness. The crew had taken to calling these “cans of delta-v.” He aimed it away from him and Morra and sprayed CO2 to clear the regolith off his glove. The black cloud whirled away into the distance. He grabbed the ARS again and stowed the can.
Tighe brought up an AR display of the ARS’s tech schematic in his crystal. The virtual animation glowed comfortingly in the darkness next to him, demonstrating the steps of his task superimposed over the real machine. He followed the procedures to power down the ARS’s system, then detached the electrical and data lines from the huge machine’s trapped limb. Several times he had to spray CO2 to clear away encroaching, electrically charged regolith. “Ryugu keeps trying to eat me.”
