Dead on Mars

Chapter 70 - Sol Ninety-Nine, Polyethylene and Condenser
Tang Yue rummaged through the crates for a few polyethylene sheets. These sheets were originally used to wrap the food crates, but they were no longer of any use.

He then held the plexiglass water trough on the work desk in hand, donned the Radiant Armor, and waved to Mai Dong before leaving Kunlun Station.

Tomcat stood by the side of the pit, holding onto a long shovel. It was covered in dust as it looked into the distance with indelible marks on its face.

The pit had a diameter of about a meter and a depth of about half a meter. The sand and gravel dug up were piled to the side. Tomcat was a cat after all—a great digger of holes.

“Tell me.” Tomcat pointed to the pit at its feet. “How do you plan on using this hole to gather freshwater?”

It planned on deciding whether to bury the fellow in that very pit based on his answers.

“Condensation.” Tang Yue placed the plastic sheet and water trough on the ground and slowly crouched down to grab a handful of dirt from the pit. The soil was still very dry, and it was mixed with hard siliceous material and layered rock. Tang Yue grabbed the shovel and began fixing the pit. He widened the bottom of the pit, removed sharp gravel, and flattened the pit’s walls and bottom.

“What’s the temperature now?” Tang Yue asked.

Tomcat looked at the sun. “–30°C. It will be noon soon, so the temperature is a little high.”

Tang Yue nodded.

“Come, give me a hand. Spread that plastic sheet open.”

Tang Yue and Tomcat spread open the smooth plastic sheet. Then, they neatly covered the pit’s bottom and walls. Plastic sheets made of low-density polyethylene (LDPE) were very soft and had great plasticity. Following that, Tang Yue placed the water trough in the middle of the pit.

“This water trough is used to collect the water?” Tomcat asked.

“Yes.” Tang Yue pulled over the rubber tubing, that delivered the fuel, before stuffing the end of the Y-shaped tube into the pit.

Tang Yue and Tomcat spread open a second plastic sheet. They spread it tight and covered the pit’s mouth completely. After confirming that there weren’t any holes or any leaks, they secured the ends of the plastic sheet with soil.

Following that, Tang Yue picked up a rock and gently placed it in the middle of the plastic sheet at the top of the pit’s mouth.

Gravity made the plastic sheet sink slightly.

“It’s done.” Tang Yue patted his hands. “This is a condenser. It’s much faster than a condensate tube.”

Tomcat circled the pit and understood Tang Yue’s intentions.

This was indeed a condenser. As long as they lit the methane, the generated steam would rise and touch the cold plastic sheet. Mars’s environmental temperature was very low, allowing the plastic to maintain a low temperature. Once the steam dropped in temperature, it would condense to form water droplets, and under gravity, it would gather at the lowest point of the slanted plastic sheet.

All the water droplets would eventually drip into the water trough at the bottom of the pit.

The first sheet at the bottom of the pit was to prevent water droplets from entering the soil. This condenser was nearly a completely sealed setup, and steam wouldn’t escape. All the water would either fall into the water trough or be intercepted by the plastic sheet that lined the bottom of the pit.

The entire plastic sheet is a condenser. The bigger the hole, the more water we can gather,” Tang Yue said.

Tomcat pondered for a moment. “However, you can’t make it too huge either; otherwise, the water will freeze on the sheet. The heat generated by burning methane is limited.

Tang Yue was taken aback. After careful thought, it made sense.

Tomcat turned to climb on top of the Mars Wanderer and turned on the decompression valve.

Tang Yue went into a prone position as he carefully raised one end of the plastic sheet and reached in to adjust the glass tube’s height. He didn’t want the methane flame to be too close to the plastic sheet; after all, polyethylene wasn’t heat resistant and melted under heat. Following that, Tang Yue used the electric arc igniter to light up the methane.

Tomcat and Tang Yue gathered around the pit’s periphery as they stared intently at the plastic sheet.

LDPE sheets were transparent. Through it, Tang Yue could see the pale yellow flame in the pit.

He was a little worried. No one knew if this was a workable idea, but water was truly a precious resource. If this method failed, he had no choice but to think of other means to gather water.

Five seconds later.

A layer of blurry steam covered the plastic sheet. The water rapidly gathered as huge droplets of water appeared. They began to slowly slide down the plastic sheet.

Tang Yue and Tomcat slumped down onto the ground as they heaved a sigh of relief.

…

Tang Yue and Tomcat did some math. By using this method, they were able to get about three to five liters of water an hour. This was limited to the combustion rate of the propellant. If Tomcat raised the methane and oxygen release rate, it would generate more steam.

However, it couldn’t be raised indefinitely, greater amounts of methane created a flame that might burn through the plastic sheet.

Half an hour later, the water trough was full. Tomcat lifted the water trough from the pit, and immediately returned to Kunlun Station. However, the water in the water trough began freezing the moment it was exposed to the atmosphere. By the time Tomcat had closed the airlock’s hatch, there was already a thick layer of ice floating on the surface.

They began searching for a more suitable way of gathering water.

Tomcat chased Tang Yue away as usual to reduce the depletion of the Radiant Armor’s power. Alone, it sat in the pit and watched the condenser.

Tang Yue was inside Kunlun Station maintaining the OGS and water recovery system.

“A speed of 3 cm³/s is too slow. Furthermore, the flame’s temperature isn’t high enough.” Tomcat’s voice sounded over the earpiece. “The water on the sides of the sheet has already frozen. I think the temperature inside the pit should be maintained between 0 to 5 degrees Celsius… I should get a thermometer over.”

“Then increase the methane delivery.” Tang Yue opened the OGS cabinet’s cover and held a wrench. “Let’s see what happens when you raise it by 5 cm³/s.”

“Hmm… I’ve increased it by five. The gathering speed is twice as fast as before, but there’s still freezing on the boundaries of the sheet.” Tomcat’s voice sounded. “The temperature at the bottom of the pit is… 1°C. The temperature of the pit’s walls is still below zero.”

“The temperature in the pit isn’t uniform?”

“No, it isn’t,” Tomcat said. “After all, the heat source is from the methane flame. Heat will rise, so the air in the upper layer of the pit heats up faster than the surroundings and bottom. It’s best we speed up the temperature rise.”

“Go ahead.”

Tang Yue closed the OGS cabinet’s lid, patted it, and turned to look out.

He saw Tomcat crawling down from the Mars Wanderer in a rather dexterous manner. It had likely just opened the propellant’s decompression valve.

The cat went into a prone position with its ass up. It opened the plastic sheet and lit the methane.

A second later.

“Boom!” There was a loud boom as the pit burst into flames.