Chapter 4

In a broad sense, the fuel for a spacecraft is divided into two parts: one part is the fuel, and Xiao Yu uses liquid hydrogen; the other part is the oxidizer, and Xiao Yu uses liquid oxygen.

Fuel must be combined with an oxidizer to burn and produce power. Now, the fuel on the spacecraft is almost depleted, but there is still a lot of oxidizer left.

In this situation, if Xiao Yu can control the spacecraft to reach Titan, the almost infinite methane on Titan can replace liquid hydrogen as Xiao Yu's current energy source. After developing a controllable nuclear fusion device, Saturn will become an inexhaustible source of nuclear fusion fuel.

At that time, Xiao Yu will have the energy to repair the spacecraft, to fully power up and restore powerful computing capabilities, and even to mine minerals and manufacture new equipment and spacecraft!

Reality makes Xiao Yu sigh endlessly. Titan is right there, but Xiao Yu cannot reach it. Infinite energy is right there, but Xiao Yu cannot get there due to a lack of energy.

"Liquid hydrogen, liquid hydrogen, I need liquid hydrogen!" Xiao Yu almost wants to roar in frustration.

In fact, if he scavenges a bit more, the remaining fuel can barely support reaching Mars' escape velocity and leaving Mars' orbit. However, in that case, the remaining energy would only be enough to power the central computer for nine months.

Nine months seems long, but compared to the long journey through space, it is really just a fleeting moment.

Even if Xiao Yu disregards the consequences and relies on the remaining energy to barely escape Mars' gravitational field, his maximum speed would only be six kilometers per second. At such a speed, it would take about seven years to reach Titan. In other words, Xiao Yu would die halfway.

Such an outcome is something Xiao Yu cannot accept.

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

"If I don't fly directly to Titan but first head towards the Sun, using the gravitational acceleration from Venus, the Sun, my speed could reach about eight kilometers per second, and the closer I get to the Sun, the faster I will go. This way, I would only need about two months to reach Earth's orbit. Hmm? Right, there are many comets in the asteroid belt near Earth, and a large amount of water is evaporated. If I can collect some water, after getting close to the Sun, I can use the Sun's ionization effect to split the water into oxygen and hydrogen! I will have energy again!"

Xiao Yu's spirits lifted, and in the vast emptiness, he finally saw a glimmer of hope.

"When I get close to the Sun, my maximum speed will reach twenty-six kilometers per second... then orbit the Sun once and continue to use Mercury's gravity to accelerate. Venus will be on the other side of the Sun, so it won't count. Next is Mars' gravity... I'll have to stay far from Jupiter, but even passing a few million kilometers away from Jupiter, Jupiter can still increase my speed by three to four kilometers per second... In this way..."

Xiao Yu calculated carefully, becoming increasingly excited.

"If I head towards the Sun, orbit the Sun once, and then go to Saturn, although the distance increases from about 1.3 billion kilometers to about 1.9 billion kilometers, my speed will increase! I can save at least five years! And at Earth, I can obtain liquid oxygen and liquid hydrogen. Being close to the Sun, the amount of solar energy I can obtain is also considerable, which will replenish the fuel!"

"There is one thing to be very concerned about," Xiao Yu calculated silently. "Earth's orbit is now extremely chaotic, and I need to be wary of being hit by meteorites. Also, the Sun has definitely been affected by Jupiter, and the intensity of the solar wind is likely several times stronger, which is a potential danger."

"Never mind, when I reach Earth's orbit, I'll temporarily leave the ecliptic plane. Collecting less water is better than risking safety. As for the Sun, I won't cross Mercury's orbit. Although the acceleration will be less, the safety factor will be much higher, and the thermal insulation layer will be less tested."

"Alright, that's it!" Xiao Yu made up his mind, checked himself one last time to ensure there were no major flaws in the plan, gritted his teeth, and started the spacecraft's engine.

This is like a gamble. Who knows what dangers lie ahead? But if he gambles, there is about a thirty percent chance of survival. If he doesn't, it's certain death. Xiao Yu is unwilling to die just as he is about to achieve a breakthrough in controllable nuclear fusion technology and a bright future awaits him. He has to take a chance.

There are too many unfavorable factors. Not to mention the possibility of new equipment failures during the long journey, or being hit by meteorites, or whether he can collect enough water, even the spacecraft's thermal insulation layer was designed to withstand atmospheric friction during planetary landings, not the Sun's high temperatures.

But in this situation, he has no choice but to push forward. Struggling on at least gives him a chance of survival. Xiao Yu is unwilling to die after his soul and the central computer fused by chance, after enduring so many difficulties to gain infinite life, immense computing power, and boundless energy, just as his interstellar journey is about to begin.

Watching Mars gradually recede, Xiao Yu silently said to himself, "Big brother Mars, thank you for shielding me from such a strong storm. When I become technologically advanced in the future, I will definitely come back to help you. I will turn you into a green planet, release some animals, and transform you into a paradise."

After making a silent wish, Xiao Yu resolutely closed the telescope. In this situation, every bit of energy saved is valuable.

Immediately after, Xiao Yu shut down most of the non-essential functions of the main control computer, leaving only the navigation system, radar collision avoidance system, and a few other essential systems, and began the long and bleak journey.

Currently, Mars is about 80 million kilometers from Earth's orbit. It will take Xiao Yu two months to reach Earth's orbit. After such a long journey, the result is to return to the starting point, which makes Xiao Yu very depressed.

There is also the issue of relative speed. For example, while Xiao Yu orbits Mars, he also follows Mars in its orbit around the Sun, at a speed of about 25 kilometers per second. When Xiao Yu leaves Mars and heads towards the Sun, from Mars' perspective, Xiao Yu flies out along the tangent of the orbit, but from the Sun's perspective, Xiao Yu follows a parabolic path. In short, Xiao Yu's speed towards the Sun is about eight kilometers per second, and he will gradually accelerate under the Sun's gravity, eventually taking about two months to reach Earth's orbit.

Apart from having the robot on board start the necessary preparations for collecting water, all other energy consumption has been reduced to the minimum. Xiao Yu cannot even process the data obtained from Jupiter. In his frustration, he only allocates a tiny fraction of CPU usage for the robot and spends his days staring at the dark universe.

Without the atmosphere's obstruction, the stars are incredibly clear. Among the countless stars, Xiao Yu found the location of Alpha Centauri B.

Alpha Centauri B is the nearest star to the Sun that is confirmed to have planets, about 10.5 light-years away. Alpha Centauri B is also the next destination in Xiao Yu's interstellar travel plan. Alpha Centauri B is confirmed to have a gas giant planet about 1.5 times the mass of Jupiter, which can provide Xiao Yu with ample nuclear fusion fuel. There are also two asteroid belts around Alpha Centauri B, which can provide Xiao Yu with ample building materials.

"Alpha Centauri B. The first interstellar journey of humanity." Xiao Yu stared intently at Alpha Centauri B, muttering to himself, unable to resist fantasizing about the scenario when he reaches the Alpha Centauri B system.

After watching for a long time, Xiao Yu finally pulled himself together and sighed sadly, "If this trip to the Sun is not successful, let alone reaching the Alpha Centauri B system, whether I can even survive is a question."

More than a month has passed during the long journey. The number of meteoroids in interstellar space has noticeably increased.

The current trajectory of the spacecraft has already left the ecliptic plane. The orbits of the planets are mostly within the ecliptic plane, and even if Earth exploded, most of its debris would still be in the ecliptic plane.

Leaving the ecliptic plane reduces the likelihood of encountering danger to the minimum.

During this more than a month, Xiao Yu controlled the robot to use the remaining materials to make a simple filter net to collect ice particles and dust in interstellar space.

Due to the conservation of angular momentum, even if Earth exploded, most of its debris would continue to orbit the Sun along the original path, and its speed would not change much. In recent days, Xiao Yu has intentionally adjusted his trajectory to approach Earth's original orbit, so the relative speed between Xiao Yu and these ice particles and dust is not very fast, about 100 to 200 meters per second. The strength of the filter net is sufficient to capture them gradually.

However, the result made Xiao Yu sigh inwardly.

It has been 24 hours since the filter net was deployed, but the total mass of captured material is less than one kilogram, with water accounting for less than thirty percent.

"Even a small amount is better than nothing. Let's take it slowly." While adjusting his trajectory to approach Earth's orbit, Xiao Yu began the work of a cosmic scavenger.