Chapter 4: Cosmic Scavenger

In a broad sense, spacecraft fuel is divided into two components. One is the fuel itself, for which Xiao Yu uses liquid hydrogen; the other is the oxidizer, for which he uses liquid oxygen.

Fuel must be combined with an oxidizer to burn and generate thrust. However, the spacecraft’s fuel reserves are nearly depleted, while there is still a surplus of oxidizer remaining.

In this situation, if Xiao Yu could pilot the spacecraft to Titan, the virtually limitless methane on Titan could replace liquid hydrogen as a short-term energy source. Once a controllable nuclear fusion device is developed, Saturn itself would provide an inexhaustible supply of fusion fuel.

At that point, Xiao Yu would have the energy needed to repair the spacecraft, restore full computational power, and even mine minerals to manufacture new equipment or build a new spacecraft!

Reality, however, left Xiao Yu deeply frustrated. Titan was right there, yet he couldn’t reach it. An infinite energy source was within sight, but Xiao Yu couldn’t obtain it due to his lack of energy.

“Liquid hydrogen, liquid hydrogen, I need liquid hydrogen!” Xiao Yu was so vexed that he nearly shouted in exasperation.

In fact, with some additional scrapping and effort, the remaining fuel could barely support achieving Mars’ escape velocity and leaving its orbit. However, doing so would leave Xiao Yu with only enough energy to sustain the central computer for nine months.

Nine months might seem like a long time, but compared to the prolonged journey across the cosmos, it was fleeting.

Even if Xiao Yu disregarded the consequences and used the remaining energy to barely escape Mars’ gravitational pull, his maximum speed would still only reach six kilometers per second. At such a speed, it would take about seven years to reach Titan. In other words, Xiao Yu would perish halfway there.

Such an outcome was absolutely unacceptable to him.

Xiao Yu began calculating meticulously, trying to devise an alternative solution.

“If I don’t fly directly to Titan but instead head toward the Sun first, leveraging the gravitational pull of Venus and the Sun for acceleration, my speed could reach around eight kilometers per second. The closer I get to the Sun, the faster I’ll go. In this way, I could reach Earth’s orbit in about two months. Hmm? That’s it! Near the asteroid belt around Earth, there are plenty of comets with large amounts of water evaporating from them. If I can collect some water, I can use the Sun’s ionization to split it into oxygen and hydrogen. Then I’ll have energy again!”

Xiao Yu’s spirits lifted, and amidst the vast hopelessness, he finally saw a glimmer of hope.

“When I approach the Sun, my speed will reach a maximum of 26 kilometers per second… Then, I can orbit the Sun once, continue accelerating using Mercury’s gravity, and skip Venus since it’s on the other side of the Sun. Next comes Mars’ gravity… Jupiter’s out of the question. I must stay far away from it. However, even at tens of millions of kilometers, Jupiter’s gravitational pull could still accelerate me by at least three or four kilometers per second… In that case…”

Xiao Yu carefully worked through the calculations, his excitement growing with every step.

“If I head toward the Sun, orbit it once, and then go to Saturn, the journey would increase from the roughly 1.3 billion kilometers of a direct route to about 1.9 billion kilometers. But my speed would improve! I could save at least five years of travel time. Plus, at Earth, I could obtain liquid oxygen and liquid hydrogen. Being closer to the Sun would also mean a considerable gain in solar energy. This way, I’d replenish my fuel reserves!”

“There is one major concern, though,” Xiao Yu mused. “Earth’s orbit is in utter chaos now. I’ll need to guard against asteroid impacts. Then there’s the Sun. It’s definitely been affected by Jupiter, and the solar wind intensity has probably increased several levels, posing a potential danger.”

“Forget it. When I reach Earth’s orbit, I’ll temporarily leave the ecliptic plane. Collecting less water is a minor compromise for safety. As for the Sun, I’ll avoid crossing Mercury’s orbit. Though this will slightly reduce the acceleration, it’ll greatly improve safety and lessen the stress on the heat shield.”

“Alright, it’s settled then!” Xiao Yu made up his mind. After a thorough self-check to ensure there were no significant flaws in the plan, he gritted his teeth and fired up the spacecraft’s engines.

This was essentially a gamble. Who knew what dangers lay ahead? But if he took the gamble, he had about a 30% chance of survival. If he didn’t, he would be resigned to certain death. Xiao Yu simply couldn’t accept dying when a breakthrough in controllable nuclear fusion and a bright future awaited him.

No matter what, he had to fight for it.

There were simply too many unfavorable factors. Not to mention the possibility of new equipment failures during the long journey, or the risk of meteorite impacts, or whether enough water could be collected—there was also the matter of the spacecraft’s heat shield. Originally designed to withstand atmospheric friction during planetary descents, the heat shield was never meant to handle the Sun’s intense heat.

But faced with these circumstances, Xiao Yu had no choice but to press forward. Whether feasible or not, he had to try. Pushing on gave him at least a glimmer of hope. Xiao Yu could not reconcile himself to the thought of dying just as he had fortuitously managed to fuse his soul with the central computer, gaining infinite life, extraordinary computational power, and limitless energy—only to perish before his interstellar journey even began.

As Mars slowly receded in the distance, Xiao Yu silently said in his heart, “Big brother Mars, thank you for shielding me from such terrible storms. Once I develop advanced technology in the future, I’ll come back and transform you. I’ll turn you into a green planet, introduce some animals, and make you into a paradise.”

After making this silent vow, Xiao Yu decisively turned off the telescope. In these conditions, even a slight saving of energy was critical.

He then shut down most of the non-essential functions of the main control computer, leaving only critical systems like navigation and radar collision avoidance online. Thus began the bleak and arduous journey.

Mars was approximately 80 million kilometers away from Earth’s orbit. It would take Xiao Yu two months to approach Earth’s orbit. After traveling such a vast distance, he found himself back at square one, which left him feeling incredibly frustrated.

This also involved a matter of relative velocity. For instance, while Xiao Yu orbited Mars, he was also following Mars’ orbit around the Sun at a speed of roughly 25 kilometers per second. When he left Mars and flew toward the Sun, from Mars’ perspective, he appeared to shoot straight along a tangential trajectory. However, from the Sun’s perspective, Xiao Yu followed a parabolic curve. The details were complicated, but ultimately, his velocity toward the Sun was approximately 8 kilometers per second. Under the Sun’s gravitational influence, his speed would gradually increase, allowing him to reach Earth’s orbit in about two months.

To conserve energy, Xiao Yu assigned the spacecraft’s onboard robot the task of preparing to collect water while reducing all other energy consumption to a bare minimum. He even refrained from processing the data collected from Jupiter. Frustrated, Xiao Yu spent his days staring into the pitch-black void of space, allocating only 0.03% of his CPU to assist the robot.

Without the obstruction of an atmosphere, the starlit cosmos appeared exceptionally clear. Among countless stars, Xiao Yu identified Proxima Centauri.

Proxima Centauri, the nearest star confirmed to have planets, was located about 10.5 light-years away. It was also the next target in Xiao Yu’s interstellar travel plan. Proxima Centauri was known to host a gas giant approximately 1.5 times the mass of Jupiter, which could provide ample fusion fuel. Additionally, two asteroid belts surrounding Proxima Centauri could offer sufficient construction materials.

“Proxima Centauri. Humanity’s first interstellar destination,” Xiao Yu murmured, his gaze fixed on its faint light. He couldn’t help but imagine what it would be like to reach the Proxima Centauri system.

After gazing for a long time, Xiao Yu withdrew his thoughts, sighing sorrowfully. “If this journey to the Sun doesn’t go well, forget Proxima Centauri—even surviving will be a problem.”

Over a month of the long voyage had already passed. The number of meteoroids in interstellar space had noticeably increased.

By now, the spacecraft’s trajectory had moved away from the ecliptic plane. Most planetary orbits lie within the ecliptic plane, and even if Earth had exploded, most of its fragments would remain within that plane.

By steering clear of the ecliptic plane, the likelihood of encountering danger was significantly reduced.

During this month, Xiao Yu used the remaining materials to instruct the robot to construct a simple mesh filter for collecting ice particles, dust, and other substances in interstellar space.

According to the principle of conservation of angular momentum, even if Earth exploded, most of its fragments would continue orbiting the Sun along their original path, with little change in speed. In recent days, Xiao Yu had deliberately adjusted his trajectory to approach Earth’s original orbit, minimizing his relative velocity to these fragments. The relative speed was only about 100 to 200 meters per second, making the mesh filter strong enough to gradually capture the particles.

Yet the results left Xiao Yu sighing in frustration.

Twenty-four hours had passed since deploying the filter, but the total mass of material collected was less than a kilogram. Of that, water accounted for less than 30%.

“Even a mosquito’s leg is meat,” Xiao Yu consoled himself as he continued adjusting his trajectory toward Earth’s orbit, diligently playing the role of a cosmic scavenger.