Chapter 385 - 377 Houston, we..._1

How long does it take to fly to the Moon?

Light needs only 1.2 seconds, while Apollo 11 took 80 hours. The subsequent missions raised the fastest record for manned spacecraft to 69 hours.

Although this includes the time from launch to entry into low-Earth orbit, which is a matter of about ten minutes and can be neglected.

The straight-line distance between Earth and the Moon is 380,000 kilometers. Theoretically, at a velocity of 11.2 kilometers per second, one could arrive in just over ten hours. However, this is not the case in reality.

Spaceflight is not like racing on the ground. The Moon rotates around the Earth, so the trajectory of the spacecraft is an arc rather than a straight line, and the velocity of the transfer orbit is constantly changing.

According to traditional astronautics, as long as the velocity is higher than the first cosmic speed, a spacecraft can leave near-Earth orbit and fly to the Moon. The maximum velocity, however, is just below the second cosmic speed’s upper limit at 11.2 kilometers per second.

The reason for this number is that the Earth-Moon system is still within the range covered by the second cosmic speed — that is, within the Earth’s gravitational pull.

The Moon itself is captured by Earth’s gravity to orbit around it. If a spacecraft’s velocity does not exceed the second cosmic speed, it cannot escape the Earth’s gravitational field. By the time it reaches the Moon, much of its momentum has already been depleted, and it only needs to decelerate slightly to be captured by the Moon’s gravity.

Exceeding the second cosmic speed means it can’t rely on the Moon’s gravity for capture, requiring a lot of extra fuel to reduce the velocity.

Therefore, for traditional spacecraft and satellites, it is more appropriate to control the velocity between 10 and 11 kilometers per second. This way, gravity will gradually decimate the maximum 10 km/s of momentum while flying from Earth to the Moon. A little deceleration thereafter would allow for entry into lunar orbit.

Storm’s velocity in near-Earth orbit has reached 7.9 kilometers per second. If it were to adopt such an orbital transfer to the Moon, it would only take three and a half hours to complete the required velocity increment acceleration. Then it could drift leisurely, waiting to be captured by the Moon’s gravity. The time taken would also be over three days, consuming just over a ton of fuel, which is negligible compared to its mass of over a hundred tons.

However, this test was not about saving fuel. Such a fuel-efficient flight path was too wasteful for Storm; what she sought now was speed.

Storm’s journey to the Moon had four stages:

The first stage involved orbiting Earth while accelerating from 7.9 kilometers per second to 11.2 kilometers per second to enter the transfer orbit, taking 208 minutes.

The second stage found Storm already on the Earth-Moon transfer orbit heading towards its destination. Subject to an average deceleration of about 3.47 centimeters per second due to Earth’s gravity every second, it would continue to accelerate for roughly 90 minutes, increasing its velocity to around 12.8 km/s.

In the third stage, the engines would be shut down for approximately 25 minutes. During the glide, the RCS system would be used for turning around to prepare for deceleration.

The fourth stage would involve reigniting the engine and continuing to decelerate to the lunar orbit’s velocity of 1.68 km/s, a process of about 757 minutes, or roughly 12.6 hours.

The entire acceleration stage would cover about 72,000 kilometers, the glide and turnaround stage 18,000 kilometers, and the deceleration stage, being the longest, about 310,000 kilometers. The total distance would be nearly 400,000 kilometers, reaching the Moon in 18 hours.

Even though the velocity in the flying process only slightly exceeded the second cosmic speed, Storm was almost always firing its engines, burning about five tons of fuel. It maximized compression of the flight time using the engine technology’s limit, with 75% of the journey spent in deceleration.

In contrast, the Apollo spacecraft, which departed at a high velocity of 10.8 km/s, had already reduced to 800 m/s by the time it reached the 324,000-kilometer Lagrange L1 point, hence necessitating several tens of hours.

This "wasteful" method of burning fuel is completely unfeasible for rockets using chemical propulsion, having far exceeded the capabilities of traditional engines.

During the acceleration and deceleration process, Storm endured very small accelerations of only 0.265 to 0.34 meters per second squared, which is less than 0.03G. Thus, even in an acceleration state, astronauts could leave their seats and move around for a while. However, they needed to constantly remind themselves of the acceleration their bodies were subject to, to avoid any accidents.

Similarly, the three nuclear engines that have been working continuously for eighteen hours would also represent the longest-duration power source ever operated by humanity in space, requiring extra attention to the operating conditions.

Of course, there were some minor disadvantages as well. For the 310,000 kilometers where deceleration was taking place, the tail of the spaceship was facing the Moon, so the forward portholes could not see the Moon. The astronauts could only view it through the extended cameras, and with their own eyes, they could only watch Earth grow smaller and smaller in the portholes.

...

"Houston, we have a problem."

The voice of Musk suddenly echoed in the hall of the Houston Space Center.

Deputy Director Jim, who had been slacking off, was startled for a moment, then approached the microphone and responded:

"This is Houston, Elon, what happened?"

"We’ve spotted an unidentified flying object! It took off from the Chinese people’s space station!"

"..."

The billionaire gave Jim an absurd answer before Musk could, putting question marks in the minds of all the staff at the space center.

Musk: "We were just observing the March using an optical telescope and noticed something... white. Yes, I think it must have been nearly a hundred meters long, a white object that left the space station with a plume that might’ve been several kilometers long, pink in color. That’s not possible for a rocket engine.

Billy recorded all of it, and I’ll send it to you immediately!"

Musk’s description was fairly clear, and Jim quickly understood what that so-called unidentified flying object was, but that shouldn’t be, should it?

"This is Jim, C209 crew, you should be aware that the Chinese have entered space with their nuclear-powered vehicles. They’re currently operating at the Forward Space Station, and the engine’s exhaust velocities are very high, that’s not a UFO."

Musk: "I originally thought the same, but their direction is off; they are accelerating rather than decelerating, and it’s not entering the atmosphere."

Not entering the atmosphere?

Jim: "Then please transmit the video back first, and also, please do not panic, there might have been some misunderstanding."

On the Dragon Spaceship, the full-powered Storm, having just flown out of sight from the porthole, Shen Bili was looking to remove the SD card to transmit, but Musk took off the electronic eyepiece and aimed the screen at the cabin’s camera, replaying the just-recorded video.

The staff at the Houston Space Center immediately focused their attention on the video, then saw a bright point suddenly appear in the center of the March, and the process of the bright point accelerating away.

Jim asked Musk to play the video again, then confidently said:

"That’s the Storm, it came out from the central module of the space station, and although the image you’re showing us is a bit fuzzy, you can still make out the tailfin of the spaceship. Yes, that’s it.

But I don’t know why it would be accelerating, the video is too short, and it might be that they are preparing to alter their orbit to rendezvous with the Tiangong Space Station, which is perfectly normal."