Nowadays, space flights will not surprise anyone. In the media regularly report new launches, and services provided by spacecraft - for example, satellite television or GPS navigation - are widely used "in everyday life". But, perhaps, to name all these successes of humanity "the development of space" would be too loud. So far, we master the mainly near-earth space. So, most of the satellites are located on a geostationary orbit - its height (35, 786 km) exceeds the diameter of the Earth less than three. And "Middle Space" is just a few hundred kilometers from the planet: for example, the height of the flight of the International Space Station is less than 400 km. Not too much much on the scale of the Universe ...
Of course, the devices created by man already visited the moon, and on other planets of the solar system, and the Pioneer and Voyager stations even went out of its limits. But if they are able to achieve the closest stars, we are hardly learning about it. After all, such a flight will take approximately 2 million years, and the connection with the devices will interrupt wherever before. Obviously, interstellar flights require new principles of movement in space - traditional rocket engines for this purpose are not very suitable. Meanwhile, in neighboring star systems, a person could find a lot of interesting things for himself. Now there are already more than 1000 exoplanets, and it is possible that some of them are suitable for life. In total, in the ranks of scientists heard the calls to protect humanity from space catastrophe. According to them, sooner or later the living conditions on Earth can be unsuitable for life, and only expansion into space will help save our appearance. The whole question is how to implement it.
According to the assessments of cosmologists, the size of the visible universe is about 93 billion light years, and it is known to continue to expand. Against this background, not only the solar system, but also the entire Milky Way (about 100 thousand light years in the diameter) looks like a tiny sand. The situation is complicated by the fact that the rate of movement of material objects according to the special theory of relativity (service station) cannot exceed the speed of light (about 300 thousand km / c). But even he leaves for many millennia to cross one single galaxy.
In principle, create a jet engine that can give the apparatus by the near-the-line speed, possibly even at the modern level of technology. It is such an engine that the authors of the Daedalus and Ikarus projects are offered - perhaps the most worked plans for the interstellar flight. But to use them for the colonization of other worlds is hardly possible: the fuel reserves are not enough even on braking at the end point, so the flight will be, which is called, "one way".
So far, you can travel through the universe only the characters of science fiction novels, which are at the disposal of superlilateral space ships, teleports and other achievements of the physics of the future. So is it not time for us to work in developing? In total, the Breakthrough Propulsion Physics (BPP) program was started in NASA (BPP), designed to develop fundamentally new engines for interstarial travel. Despite the fact that one of the engines is the name of the famous scientist and popularizer of Science Stephen Hawking, the world famous physicist did not participate in it: he bet on simpler annihilation engines.
The ideas of the BPP participants were much more daring. So daring that many of them are possible except mathematically: physical principles involved in them, science are not yet known. Others, although they do not violate the well-known laws of nature, would require the tremendous costs of energy or the development of materials with unusual properties. Most of the proposed engines are based on "Games" with gravity. According to modern ideas, gravity is nothing more than the curvature of space-time. It is not difficult to guess that anti-gravity should spark the space in the opposite direction. After placing an anti-gravity substance in the stern of the ship, it would be possible to give it a constant acceleration without any energy costs. The only difficulty is due to the fact that the particles with a negative mass have not yet been detected, and it is unknown if they exist at all.
However, perpetual movement can be obtained and with the help of normal gravity. To do this, it is necessary to somehow divide the mass on the source of the gravitational field and the part interacting with it, and then fasten them still relative to each other. It remains to come up with how to do this: with the same success it would be possible, for example, to propose to separate the electric field from the charge, which creates it. Another way to move in space is based on a local change in the laws of nature. Isaac Newton - the author of the first mathematical theory of gravity - found that the force of attraction depends on the mass of interacting bodies and distances between them. The equation also contains a constant - gravitational constant (G). If somehow increase this constant in the front of the spacecraft and reduce on its feed, the effect will arise, essentially similar antigravity. But the value of G is not in vain called constant: it is believed that its meaning is equally in the entire universe.
However, there are alternative cosmological concepts in which the gravitational constant is a variable value. One way or another, it is not clear how to change it with an artificial way. Engine Alcuberier is perhaps the most attractive of the proposed projects. It proposes to create a spatial bubble unchator, which would surround the ship by compressing space-time before its nose and extensions for feed. Such a "bubble" could even exceed the speed of light, without disturbing the service station - after all, limitations in speed concern only particles of matter, and not the very space itself. But, unfortunately, for this, again, the negative mass will be required, which is still only in theory. In other projects, it is proposed to master the star spaces with a sailing fleet. Once the sea ships abandoned the sails in favor of the engines: it is possible that their space "counterparts" someday do the way back. And this is not fiction. Solar sails accelerate devices by pressure generated by the flow of ionized particles or photons. The magnitude of this pressure is very small, so sails should have a very impressive area. Now they are actively developed in different countries, including in Russia. Researchers who worked as part of the BPP have much more original and effective solutions in their stock. So, they offered to create something like a sunny diode. Such a sail should pass the light in only one direction and reflect it in another. Alternatively, one side of the sail could reflect photons, and the other is to absorb them. The difference in the pressure of the light would create cravings even in the absence of a "cosmic calm" - in the absence of a passing flow of photons. "Casimir's sail" allows and not at all depend on the radiation of stars. The effect predicted by Hendrick Casimir in 1948 is associated with vacuum fluctuations, during which short-lived particles are formed. These particles are called "virtual", but they have quite real, although very weak pressure. If somehow increase it on one side of the sail, the ship would acquire a constant acceleration without any fuel costs. About how to do this, inventors are silent.
The BPP program worked for 6 years, after which it was discontinued. There is no dispute: the proposed ideas are very involved, but do they justify those 1, 2 million dollars invested in development? Due to the considerable costs, with the complete absence of practical results, some media even called the program of the "largest scientific scientific of the century". However, it is hardly true: because breakthrough results are impossible without a long theoretical training. In the end, the first flight plans to the moon also had little in common with reality ... Whether the development of NASA specialists will remain a curiosity of science or will be the first step towards interstellar journeys - will show time.