"Lunar Shield", Earth-Moon Live Broadcast... The Secrets of "Alone on the Moon"

On July 29, the sci-fi comedy "Alone on the Moon" was officially released. In addition to bringing laughter to everyone, there are many things behind this movie, such as the "moon shield" that helps the earth resist asteroid impacts, lunar infrastructure and life, smooth live broadcasts between the earth and the moon, and other details, all of which hide a lot of aerospace knowledge. Let's take a look.

Asteroid defense helps

The movie shows a scene: In order to resist the threat of asteroids hitting the earth, humans urgently deployed the "Moon Shield Project" on the moon. In fact, this plan is not completely unrealistic, and the moon has indeed helped a lot in protecting the earth.

According to incomplete statistics, there have been 22 mass extinctions of varying degrees in the history of the Earth, at least 11 of which were related to near-Earth asteroid impacts, with the impact that ended the fate of the dinosaurs 65 million years ago being a typical example. It can be said that in the foreseeable future, asteroid impacts may be one of the dangers that Earthlings need to be most vigilant about. The Earth has remained generally safe to this day, and the moon, as a "natural shield", has really helped a lot. The potholes on the moon caused by meteorites and other impacts are strong evidence of the moon's "hard work and great contributions".

To resist the threat of asteroid impact, humans have already taken action. All major space powers have discussed near-Earth asteroid defense plans, and the exposed plans include: destroying asteroids through nuclear explosions, laser ablation, kinetic direct impact, etc.; installing reverse engines on asteroids, or using space tugs, solar light pressure, gravitational traction and other technical means to deflect the orbit of asteroids to prevent them from hitting the earth. As the "near neighbor" of the earth, in addition to considering using its "weak body" to block asteroids for the earth, humans have more ways to help earthlings protect the blue mother planet.

As we all know, the gravity on the moon is only about 1/6 of that on the earth, and the air resistance is negligible. If we can build the moon into a launch base, then launching spacecraft with special modifications in structure and power from the moon will consume much less fuel, and the cost in terms of safety and environmental protection will also be much lower. As long as the warning time is guaranteed, I believe that the effectiveness of human asteroid defense operations will be significantly improved.

If you think it is too difficult to launch an interceptor from the moon, you can consider a simpler early warning purpose and build the moon into a "frontier outpost". The average distance between the earth and the moon is more than 380,000 kilometers. Early warning equipment deployed on the lunar surface or in lunar orbit will buy precious time for defending against asteroids, and people on Earth will have the opportunity to intervene in the trajectory of asteroids earlier.

In addition, we can also use the greater gravitational force of the moon on asteroids to try to cause the asteroids to change their orbits. Even if they deviate just a little, it is enough to make the asteroid and the earth "pass by each other".

In short, I believe that with the joint efforts of mankind, the means of defending against asteroids will become more and more mature, and the Earth will definitely be safer in the future.

Large-scale lunar infrastructure is not a dream

The moon is the closest natural celestial body to the earth. If humans want to fly out of the "cradle", the moon is the "first stop" that cannot be avoided. It can be said that building a lunar base will be the first step for humans to develop alien planets, and the lunar base will also be a "springboard" and "transit station" for humans to fly into deep space, and a "training camp" for familiarizing themselves with the environment of alien planets. Even the construction of the "lunar shield" envisioned in the movie cannot be separated from the support of the lunar base.

The moon contains valuable resources that humans crave, many of which are scarce on Earth. For example, helium-3 is a high-quality fuel for nuclear fusion. It is estimated that the Earth's reserves are only 500 kilograms, while the moon's reserves are likely to be as much as one million tons. Some studies have shown that 100 tons of helium-3 nuclear fusion power generation can meet the electricity needs of all mankind for one year. The moon's helium-3 reserves can theoretically eliminate the "Earth's power shortage."

If there are still many difficulties to overcome in applying helium-3, the abundant resources on the moon, such as uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, and aluminum, have more realistic value, and space mining and space launch are expected to usher in unprecedented development opportunities. Considering the limited carrying capacity of spacecraft between the earth and the moon, if humans want to develop and utilize lunar resources, they must establish production, processing, and transportation bases on the moon and set up material supply stations.

In addition, the near-vacuum and low gravity on the lunar surface are special environments that are difficult to replicate and maintain for a long time on Earth, and are of special value to scientific research. Projects such as tracing the origin of celestial bodies, biological genetic engineering, deep space life support, and artificial biospheres will all have better scientific research conditions on the moon than on Earth. In the near future, the lunar base will become an important frontier scientific research center for various countries, on par with the space station.

Precise, complex and practical scientific research activities cannot be carried out without human participation. Therefore, a series of scientific research, production and living facilities will be built on the moon. In particular, life support systems such as oxygen, water and electricity supply need to be built first.

To ensure the long-term operation of the lunar base, the necessary means of production and living materials must be self-sufficient as much as possible, and it is best to achieve "in-situ utilization" and even be able to "export" to the Earth when necessary. However, since the moon does not have a sufficiently dense atmosphere to protect it, the probability of being directly hit by celestial bodies is much greater than that of the Earth. Humanity's permanent lunar base may have to be built underground or inside a mountain to ensure safety.

Some scientists have calculated that it is necessary to cover the roof and walls of the lunar base with lunar soil up to 3 meters thick, and rely on the rock layer on the lunar surface as much as possible to build a solid defense system to resist meteorite impacts and the pervasive invasion of cosmic rays, solar winds, etc., to increase the probability of human survival and reproduction on alien planets.

Life on the Moon Is No Longer Lonely

As we all know, the moon is "tidally locked" to the earth, and people on earth can only see one side of the moon with their naked eyes. However, with the advancement of technology, humans have launched spacecraft to the back of the moon, unveiling the mysterious "veil" of the moon and creating the technical prerequisite for earth-moon communication.

Whether it is a "frontier outpost" or a commercial mine, humans working and living on the lunar base cannot be isolated from their "home", and communication with the Earth is essential. To this end, in addition to considering the establishment of permanent communication base stations and signal towers on the moon, it is also necessary to launch lunar synchronous satellites and Earth-Moon relay communication satellites.

Of course, there are many challenges to overcome in terms of communications at the lunar base, such as the barrier of the lunar sphere, which led to the far side of the moon being considered a "communication restricted area" for a time.

In 2018, my country's Queqiao relay satellite broke the "taboo" and successfully provided relay communication services for the Chang'e-4 lander and rover that were carrying out an exploration mission on the back of the moon. This built a communication "bridge" spanning more than 400,000 kilometers between the Earth and the Moon, and presumably verified the relevant technologies for solving the communication problems of the lunar base.

In addition, the solar wind can cause huge interference to communications. The solar wind is essentially a high-speed stream of charged particles. Due to the protection of the geomagnetic field, people on Earth do not feel it deeply. However, on the moon, which lacks a global stable magnetic field, the electromagnetic wave communication methods used in daily life are not so convenient. Smooth communication across hundreds of thousands of kilometers between the earth and the moon is even more difficult.

In order to ensure the quality of communication and make the spoof video live broadcast in the movie a reality, it is necessary for humans to apply "non-electrical" high-speed media optical communication, quantum communication and other technologies in the future to achieve smooth communication between the Earth and the Moon.

Recently, Chinese astronauts watched the live broadcast of the ground rocket launch smoothly in the Tiangong space station, indicating that the space communication technology has made further progress. In the future, space stations and artificial satellites are also expected to become important communication relay nodes, providing guarantee for smooth communication between the earth and the moon. It is believed that with the acceleration of manned lunar exploration and the construction of lunar bases, it will not be far away for people on earth to watch the live broadcast of the moon by Internet celebrities. By then, even if we really "walk alone on the moon", humans will no longer be alone.