The continuous improvement of the space propulsion system has solved some of the problems of space flight. In the foreseeable future, human space flight will still be based on the principles of Newtonian mechanics . In order to achieve the purpose of forward flight of the spacecraft, the role of Newtonian mechanics must be used. and the principle of reaction. The spacecraft injects gas backward, just like the rocket engine injects burning material backward. In order to achieve the purpose of forward flight of the spacecraft, the principle of the relationship between force and object motion must be used. An object moving forward pushes another object in front. Assuming that the best propeller enables travelers to reach half the speed of light, people cannot guarantee enough flight fuel. Assume that the spacecraft can fly at 0.01% of the speed of light, but people cannot afford the high fuel price.
Humanity’s dream of space flight is to fly high and far. Under the condition that flight technology is limited, people’s current flight journeys are mainly in the near space of the earth. As the speed of space flight improved slightly, flight engineers envisioned advanced or advanced thruster concepts, such as thermonuclear thrusters. In the near future, according to the most optimistic estimates, thrusters can only reach a few percent of the speed of light, and the highest flight speed that humans can achieve is far lower than the speed of light. Human beings consider many factors when looking for a suitable "second home". One of the factors is the huge distance between celestial bodies. The very limited flight speed limits human space travel plans. Space travel in any sense will It takes a lot of time.
Astrobiologists believe that the Milky Way has no shortage of habitable objects. Astronomers estimate that for every 10 to 10,000 stars, there is at least one accompanying habitable planet, and the entire Milky Way has tens of billions of habitable planets. planet. The number of habitable celestial bodies is not a problem, but the insurmountable distance between celestial bodies is a problem. The current spacecraft has achieved a relatively low flight speed, and space travelers can only "look at the sky and sigh." It is difficult for humans to reach a certain planet, but we can expect "aliens" from other planets to visit the earth. It is too early to envision space travel to different habitable worlds, but after centuries to millennia of exploration, humans may change the face of space travel, and the shortest current trip to an exoplanet will also exhaust travel the person’s life time.
Astrobiologists define the concept of habitable planets, which are " ocean planets " with water resources. The outer side of the orbit of a habitable planet is accompanied by one or more host stars. The planet receives radiation from a sun-like star. Radiant energy. A habitable planet contains a variety of elements. Habitable worlds suitable for human reproduction may be very rare, and people will not choose to live in exotic worlds with high survival risks. The Earth's atmosphere and ecosystem are not necessarily ubiquitous in the universe. The Earth is the product of a unique evolution of cosmic history. It is difficult to imagine that Earth's unique ecosystem would appear randomly or coincidentally on any other planet.
The earth in the 21st century has experienced ecological crises of varying degrees. There may be a large number of habitable worlds in the Milky Way, but the vibrant earth is very suitable for human survival and development. The green earth is an ideal home for human habitation. Meteorologists have frequently issued warnings of meteorological disasters, and carbon dioxide emissions cannot exceed one thousandth of the proportion of the earth's atmosphere. Planetary scientists have examined the unique ecosystems of habitable planets. Most habitable planets may have some environmental factors that are not suitable for human survival, such as an atmosphere that is not suitable for human breathing. The best case is barren land, and the worst case is barren land. The situation contained deadly poisonous gas.
"Terraformation" or land and atmosphere improvement is the transformation of habitable planets into human-inhabited worlds. The space version of "Project of the Century" is to modify the atmospheric composition and biosphere of exoplanets and eliminate any form of planetary localized ecosystems. Space The "super project" exceeds the endurance of human resources and is incomparable to the efforts made by humans to restore the existing earth environment to its original ecosystem. Some astrobiologists have envisioned a plan to transform the Martian ecosystem. The first Martian immigrants would plant grass, trees, and crops on the surface of Mars.A basic question is why do humans look forward to "colonizing" other planets?
Interstellar flight between different stars will take centuries. The traveler's life is spent on the long journey, and there will not be much life left to stay on the target planet. The space flight capsule has become the traveler's habitat. , travelers implement a self-sufficient " small farmer economy " in the flight cabin. As an alternative to finding a new home, humans could consider building a “home in the sky” in space in the future. According to the calculations of "space economics", the transformation of a living planet also has cost factors. We must use local materials or exploit abundant resources from space to set the goal of building a "beautiful home" in space.
Past research has shown that by building other planets into habitable homes and realizing tens of thousands or hundreds of thousands of Earth immigrants, it is possible to dig out building materials on asteroids hundreds of meters long and avoid huge long-distance transportation costs from the Earth to the target planet. , it is difficult for people to imagine the situation of transporting tens of thousands of tons of construction materials and construction tools from the earth. The cost of interstellar transportation is extremely high. The cost of building a "colony" settlement outweighs the gain in terms of economic cost. Planetary developers and builders I won’t engage in the business of “spending money to make money”.
There are countless asteroids in the solar system. The number of people "living" on asteroids will be N times that of the earth. Some asteroids have formed a pleasant living environment, and it can cost less to build human settlements on habitable asteroids. There are many twists and turns, and the technological transformation of the Martian ecological environment is time-consuming and laborious. The asteroid immigration plan may be a better choice. Human beings do not necessarily really need to visit distant stars and "colonize" habitable planets in other stars. This is not necessarily due to basic human survival needs, but more driven by human knowledge and desires. Human knowledge and wisdom have promoted dreams and actions to explore extraterrestrial worlds, and some groups of people have special curiosity about survival in outer space.
Commercial space flight is coming to people. Many space flight companies have stated that they will reduce the cost of flight to a level that many people can afford in the future. The "fare" of space flight ranges from tens of thousands of dollars per kilometer to tens of thousands of dollars per kilometer. Ranging from a hundred dollars, the reuse technology of rockets reduces transportation costs and generates large-scale economic benefits. Reasonable ticket prices make it possible for more and more people to realize the dream of space flight. Flying into the blue space, asteroid resources have ignited the craze of commercial competition. A metallic asteroid is one kilometer in size and contains hundreds of times the amount of metal resources that the earth reserves, such as: nickel, gold and other economically valuable metal elements.
Develop solar energy based on space, which will bring inexhaustible and inexhaustible clean energy to the earth. By the way, it will solve the harm of large areas of haze on the earth. It will make reasonable use of space energy and build in space. The prerequisite for a solar power station is reasonable cost control. People have witnessed exponential growth in certain products in the era of globalization, such as cars and computers, and certain products may also experience similar growth in the era of space technology. The research results of physics show a clear picture. In the near future, human beings may design homes in outer space. Living in orbiting habitats is no longer a fantasy. Human beings will obtain a large amount of resources from the earth, the sun, and asteroids. .
Meteorologists are "unfounded" in issuing warnings of global climate disaster. The earth may one day no longer be habitable. People are faced with the choice of "not knowing where to call home" in the vast starry sky, but they do not necessarily have to travel to other galaxies. , looking for human homes on infinitely distant planets, orbital habitats may be good places to settle down. The rapidly improving space technology will eventually bring strong power to build an "artificial home" in the solar system where the earth is located. This will not be a long and hopeless human fantasy. There may be a day when human beings are forced to leave the earth, unless the emissions of greenhouse gases on the earth are reduced, the mistakes that humans have made in the past are corrected, and the vibrant earth's ecosystem is restored.The way a "time machine" travels or the flight technology that "bends time and space" is still a theoretical assumption of scientists, and future space travel technology may have unexpected aspects.
(Compiled: 2015-1-27)
