Cosmic Cleaner

The spaceship's fuel is mainly divided into two parts: the main fuel, which Xiao Wu chose to be liquid hydrogen, and the oxidizer, which in this case is liquid oxygen.

Fuel needs an oxidizer to burn and generate thrust. Currently, the spaceship has very little fuel left, while there is still a lot of oxidizer.

In this situation, if Xiao Wu could steer the spaceship to Titan (Saturn VI), where there are countless methane lakes, it could temporarily replace liquid hydrogen as an energy source. After successfully researching and manufacturing a controllable thermonuclear fusion device, the Saturnian region would become an inexhaustible source of fusion fuel.

At that time, Xiao Wu would be able to restore the spaceship's power, utilize its full capacity, restore its powerful computing ability, and even mine minerals, manufacture equipment, and build new spaceships!

Reality, however, left Xiao Wu deeply regretful. Titan was right there, but Xiao Wu couldn't reach it. An inexhaustible energy source was right there, but Xiao Wu couldn't access it due to a lack of fuel.

"Liquid hydrogen, liquid hydrogen, I need liquid hydrogen!" Xiao Wu almost screamed in madness.

In fact, if he drained the remaining fuel, Xiao Wu could still barely achieve the escape velocity from Mars and leave its orbit. However, doing so would only provide enough energy for the Central Computer to operate for nine months.

Nine months seems long, but compared to the endless space journey, it's just a blink of an eye.

Even if Xiao Wu defied the consequences and relied on the remaining energy to escape Mars' gravity, the spaceship's maximum speed would only reach 6 km/s. At this speed, it would take him about seven years to reach Titan. In other words, he would die on the way.

This outcome was something Xiao Wu absolutely could not accept.

Xiao Wu began to calculate carefully, trying to find another method.

"If I don't fly directly to Titan, but fly towards the Sun, borrowing the gravitational acceleration of Venus and the Sun, my speed could reach about 8 km/s, and the closer I get to the Sun, the faster I'll go. That way, I only need about two months to reach Earth's orbit. That's right, in the asteroid belt near Earth, there are many comets containing a large amount of evaporated water. If I can collect some water, after getting close to the Sun, I can use the Sun's electrolysis effect to separate water into oxygen and hydrogen! I'll have fuel again!"

Xiao Wu's spirit lifted; in despair, he finally saw a glimmer of hope.

When approaching the Sun, the maximum speed could reach 26 km/s. Then, the ship would circle the Sun, continuing to utilize Mercury's gravity to accelerate. Since Venus is on the opposite side of the Sun, it's not considered; next, it will use Mars' gravity. As for Jupiter, it's best to stay away from it. However, even if flying past Jupiter at a distance of tens of millions of kilometers, it could still help increase the speed by 3-4 km/s.

Xiao Wu carefully calculated, and the more he thought about it, the more excited he became.

If flying towards the Sun, circling it, and then going to Saturn, the distance would increase from 1.3 billion km to approximately 1.9 billion km. However, the speed would increase significantly, saving at least five years! Furthermore, liquid oxygen and liquid hydrogen could be obtained in the Earth's orbital region. Getting closer to the Sun would also yield a considerable amount of solar energy, thus supplementing fuel!

"But there's a very worrying point," Xiao Wu silently calculated. "The current Earth's orbital region is very chaotic; we must be wary of meteoroid attacks. The Sun is certainly also affected by Jupiter; the intensity of the electromagnetic field on the Sun's surface is probably much stronger. This is also a potential risk."

"Alright, when we reach Earth's orbit, we'll temporarily deviate from the path towards the Sun and collect some water. Safety is paramount. As for the Sun, we won't pass through Mercury's orbit. Although the acceleration will be slower, the safety factor is much higher, and the pressure on the heat shield will also be reduced."

"Good, that's decided!" Xiao Wu concluded, carefully checking one last time to confirm that the plan had no major flaws, gritted his teeth, and started the spaceship's engine.

This was nothing short of a gamble. Who knows what dangers lie ahead? But if we gamble, there's still about a 30% chance of survival; otherwise, there's only death. Xiao Wu couldn't bear to die when the controlled nuclear fusion technology had achieved a breakthrough, and a bright future awaited him. He had to try, no matter what.

There were indeed too many unfavorable factors. Not to mention the possibility of equipment malfunctions on the long journey, or the risk of meteoroid attacks, or not collecting enough water; just the spaceship's heat shield alone was a major problem. Originally, the heat shield was designed to cope with atmospheric friction when landing on a planet, not to withstand the high temperature of the Sun.

In any case, the situation had come to this; he could only close his eyes and go for it, even if he couldn't, he had to try. Try his best, at least there's still hope. Xiao Wu couldn't bear the thought that he, through a stroke of luck, had overcome countless difficulties to merge his soul with the Central Computer, painstakingly obtaining infinite life, incredibly powerful computational abilities, and infinite energy, only to die before he could even launch his space voyage.

Watching Mars gradually fade into the distance, Xiao Wu whispered in his heart: "Mars, thank you for helping your little brother withstand such a great storm. Wait until my science and technology develops,I will definitely return to help you transform, uhm, transform into a green planet, and then release some animals there, turning you into a fairyland."

After silently praying, Xiao Wu decisively closed the telescope. In this situation, he could save a little energy wherever possible.

Immediately afterward, Xiao Wu shut down most of the unnecessary functions of the server, leaving only the navigation system, the collision avoidance radar system, and began the long and arduous journey.

Currently, Mars is about 80 million kilometers away from Earth's orbit, and it will take Xiao Wu two months to approach Earth's orbit. Traveling such a long distance only to return to the starting point makes Xiao Wu extremely frustrated.

This is also related to the issue of relative speed. For example, when Xiao Wu orbits Mars, he also follows Mars as it revolves around the Sun at a speed of about 25 km/s. When Xiao Wu leaves Mars and flies towards the Sun, from Mars' perspective, Xiao Wu flies straight out along the tangent of the orbit, but from the Sun's position, Xiao Wu flies along a curved arc. The specific explanation is complicated; in short, Xiao Wu's speed approaching the Sun is about 8 km/s, then it will gradually accelerate under the Sun's gravity, and it will finally take about two months to reach Earth's orbit.

Besides having the robot in the spacecraft prepare for the collection of necessary water, the remaining energy consumption has been reduced to the lowest level; Xiao Wu couldn't even calculate the data obtained from Jupiter. Because of his frustration, besides sharing some CPU with the robot, Xiao Wu spent the whole day staring blankly at the dark universe.

Without the atmosphere to obstruct, the starry sky became extremely clear. Xiao Wu found the silhouette of Epsilon Eridani among countless stars.

Epsilon Eridani is the closest star with planets to the Sun, at a distance of about 10.5 light-years. Epsilon Eridani is also Xiao Wu's space travel destination in a plan with a specific goal. Because Epsilon Eridani has been identified as having a giant gas planet with a mass about 1.5 times that of Jupiter, it can provide Xiao Wu with abundant thermonuclear fuel. In addition, there are two small asteroid belts around Epsilon Eridani, which can provide Xiao Wu with abundant building materials.

"Epsilon Eridani... Mankind's first interstellar journey!" Xiao Wu stared intently at the image of Epsilon Eridani, muttering to himself, and couldn't help but start imagining the scene of setting foot on the Epsilon Eridani star system.

After looking for a long time, Xiao Wu withdrew his mind and sighed sadly: "If this trip to the Sun is not successful... don't mention aiming for the Epsilon Eridani quaternary star system, even whether I can survive is a big problem."

During the long journey, more than a month has passed. The number of asteroids in space has begun to increase significantly.

Currently, the spacecraft's orbit has left the Sun's orbit. The orbits of the planets are basically located within the Sun's orbit; even if the Earth explodes, most of its fragments will still remain on the ecliptic plane.

Leaving the Sun's orbit will minimize the risk of danger.

Over the past month, Xiao Wu has controlled the robot to use the remaining materials to create a simple filter net to collect substances such as ice particles and cosmic dust.

Due to the law of conservation of angular momentum, even if the Earth exploded, most of its fragments would still move around the Sun along its original orbit, and their speed would not change significantly. These days, Xiao Wu has intentionally adjusted his orbit to approach the Earth's orbit, so the relative speed between Xiao Wu and these ice and dust particles is not too great, only about 200 m/s. With the durability of this filter net, it can completely capture them little by little.

However, the result made Xiao Wu sigh inwardly.

24 hours have passed since the filter net was opened. But the total amount of material collected is still less than 1 kg. Of that, the amount of water is less than 30%.

"Better than nothing, take it slowly," Xiao Wu said as he controlled his orbit to approach the Earth's orbit, doing the work of sweeping up space debris.