If no matter the cost, can a spacecraft be built to fly to Proxima Centauri? What technologies need to be broken through?

This is an imaginative topic. I feel that the earth is building a solar system fleet. You guessed it right. In "The Three-Body Problem", we learned that the Trisolaran spacecraft is traveling at 1% of the speed of light. The mentality when going to the earth is the same, otherwise why would you do it at any cost? After all, life must go on! But since we have assumed it, let’s discuss what technologies need to be broken through!

How to enter low-Earth orbit on a large scale?

Many friends will think that this is not a spacecraft. Why does it need to enter low-Earth orbit on a large scale? In fact, if you want to build an interstellar spacecraft, where will a large amount of materials come from? You can't just grab an asteroid and smelt metal in orbit to build it on site! Therefore, a large amount of materials must be manufactured on earth and then assembled in space! Another way is to manufacture laser rapid prototyping equipment in space, and then transport various raw material powders to space for direct manufacturing. This way can reduce the volume of materials, but the volume of various support facilities will still not be small! There are two ways at present and in the near future:

Rocket engine

Aerospace engine

The former is our common rocket engine, which is the current way to enter space. The only means is that the technology is mature and many countries have this condition! But the efficiency is low and the cost is high. Even the payload is only a little more than 1%-2% of the mass ratio of the whole rocket. If we want to build a 100,000-ton spacecraft, the total consumption will be about 10 million tons. of fuel, which is unacceptable.

The latter is a combination of turbojet + ramjet + scramjet + rocket engine, or a pulse detonation engine that can be statically ignited to extremely high supersonic speeds and freely converted to rocket engines. If used The cost of this type of engine will be significantly reduced. It takes off horizontally, enters the orbit and then returns to the ground for a horizontal landing. The engine can use oxygen in the atmosphere and use aerodynamics to improve load and fuel utilization, so the cost will be greatly reduced. If you want to cross the stars, you must have an aerospace engine to enter low-Earth orbit as a stepping stone!

Some friends will think that it is possible to build a space elevator. In fact, this kind of project seems very slow, but the manufacturing cost and difficulty are extremely high. It is basically impossible to operate because the materials have not been manufactured yet. Not to mention the illusory creation of a space elevator!

Which space engine to choose?

Chemical energy rockets can be used from the ground to low-Earth orbit, but chemical rockets for interstellar flight after reaching space are not effective because the specific impulse is extremely low, and interstellar flight requires a very long period of acceleration. To accelerate a spacecraft to a speed that can span light years, you must need an engine that can continue to accelerate for years or even decades. Obviously chemical rockets are impossible. There are several promising engine types currently:

Solar sail

Ion engine

Fission engine

Fusion engine

The solar sail can be ignored at first. This legendary method of interstellar navigation can only be played within the solar system. When crossing interstellar space, the solar sail is a burden!

The ion electric propulsion engine is the most mature technology currently and has a very high specific impulse. It is more suitable for interplanetary flight and is theoretically suitable for interstellar flight. As long as we carry enough working fluid, we can go there The place you want! But the electric propulsion engine has a fatal flaw, that is, it requires electric energy. Huge solar cells can be used to barely maintain it in the orbit of Saturn, and there must be a stable power supply outside!

In the past, Orion just threw nuclear bombs behind its butt, but don’t underestimate this violent and low power method. The super spaceship used to save the people on earth in "Evacuation from the Earth" used nuclear bombs behind the spacecraft. Because mankind has become proficient in nuclear bomb miniaturization technology, the main cost is of course the extraction of nuclear materials. Of course, we can't really drop a complete nuclear bomb in the rear, we must use some kind of neutron flow to detonate it!

Nuclear fusion is of course the most ideal. For interstellar navigation, magnetic constraints are obviously inferior to inertial constraints. From a structural point of view, inertial constraints have a natural advantage as a propulsion engine! Use a laser beam to fuse small balls of nuclear fusion material to release energy and propel the spacecraft forward!

What does the ecosystem need to include?

A manned spacecraft must require crew members and a life support system, but the following technologies will significantly reduce the life support system requirements of the spacecraft.

Hibernation

Biosphere Cycle

If hibernation can be achieved, the material demand for spacecraft will be greatly reduced. If technology cannot achieve hibernation, then the ecological cycle The scale will increase significantly, and more than 1/3 of a spacecraft may be used as a greenhouse for ecological recycling.

......

The above are the choices of several key technology nodes. The technical routes we must implement are:

1. Sky and Sky Aircraft

2. Space assembly

3. Ion engine + nuclear fission reactor power supply

4. Small biosphere cycle

These Technology is a hurdle that cannot be overcome. There will be some difficulties in building an aerospace aircraft in the next 100 years, but the implementation problem is not big, the space assembly problem is not big, and the ion engine and space nuclear fission reactor are also no problem (but this top speed cannot reach 1%, nor Not fast, but slow), the only thing left is the small biosphere cycle. The failure of the United States on Biosphere 1 and 2 gave everyone a huge blow. It is difficult to say that the ecological cycle on future spacecraft will be sustainable. Compared with the earth, the space environment will be harsher. The more humans need to intervene in this cycle, the greater the uncontrollable factors will be. In the end, we will find that there are still a lot of unresolved problems when we step on the spacecraft.

Trisolarans will reach Earth in 600 years. If we use ion propulsion, it may take 1,000 years to reach Proxima Centauri, and we must reserve fuel for deceleration.