With great excitement I follow the experiments in the United States on laser ignition of a thermonuclear reaction in a relatively small volume. There are first successes, this gives hope ... Give me a couple of trillions - and in ten years we will warm up the engines of the interstellar spacecraft, and in 100 years we will be on Proxima Centauri, and this with modern technologies. I imagine this ship as follows: In Africa, on Mount Kenya (on a plain with an ascent uphill), a 300-kilometer electron gun is being built to launch cargo into space. We launch 250 thousand tons of graphite (coal) into space, by centrifugal casting and vacuum spraying, we form a graphene disk - 1 mm thick and 10 kilometers in diameter. The disk rotates at an angular speed of 1 revolution per minute, a ball (1 cm in diameter) of deuterium with tritium flies out of its hub every second, at a distance of 1 km it falls into the focus of laser beams and produces a thermonuclear explosion. The disk receives the impulse of the explosion products (neutrons, helium nuclei, etc.), and thrust arises. The second purpose of the disk is to catch, like crazy, atoms of hydrogen and other elements (in much smaller quantities) in space, and, due to rotation, like a centrifugal pump, drive them to the periphery, where an annular trough will collect them and pump them into the central engine. The disk will collect 200 kilograms of hydrogen per day (including 2 kilograms of deuterium) at a speed of 30,000 km per second. During the flight, the crew will improve the ship according to instructions from Earth, rebuilding it from the captured substances, so that the speed will increase. The third function of the disk is a radio antenna for communication with the Earth: it will be shaped like a Fresnel lens and will have the properties of a parabolic radio mirror. Acceleration, flight and deceleration will take 100 years, you will need to take fertilized eggs, or human embryos with you, create conditions for the harmonious development of space children ... I repeat that this is possible now with modern technologies, you just need to stop doing nonsense and channel funds and thoughts skyward.
Perhaps if the next generations find a way to use the energy ( E ) hidden in the mass ( m ), E = mc² . Now only one mechanism for extracting this energy is known. This is annihilation i.e. substance + antimatter → light. All other energy sources are less efficient and therefore require resources that are not enough on Earth. The engine itself will be in the form of a mirror reflecting the annihilation light. We can use the Moon as matter for the engine. Its mass is more than enough to reach Alpha Centauri in several generations. When traveling to another star, instead of the Sun, you can use a small artificial Earth annihilation satellite, which will warm and illuminate the Earth. The flight mode of the Earth to the star will be quite simple. One third of the way is acceleration (say 0.01 m / s²), one third is constant speed, and the last third is deceleration. Where to get antimatter? This is a problem now. Making it out of matter is pointless. There is not so much energy. But maybe there is a chance to find her in the nearest space? It's hard to imagine this now. I hope that the next generations will solve this problem, because they have several billion years to think about it before the Sun begins to turn into a Red Giant.