So, what is the maximum exhaust speed? People naturally think of photons. Because Einstein's theory of relativity tells us that the speed of all substances in the universe is the fastest, reaching 300 thousand kilometers per second. If the rocket engine can be made to jet photons backward, it will naturally make the rocket and the spacecraft transported by the rocket fly at a speed close to the speed of light. ?
So, how do you make mega emit photons? That is, how to generate photons in the rocket engine and then inject them back? As early as 1950s, German scientist Sanger put forward the idea of photon rocket.
In antimatter rockets, positive and negative matter will be annihilated when they meet, and photons will be released in addition to heat energy. Antimatter rockets only use the heat energy released by annihilation reaction. Then, isn't it the power energy that photon rockets need to divide? Sanger thinks so, too. He imagined that hydrogen (proton) and antihydrogen (antiproton) would meet and annihilate to produce photons.
Sanger's idea of using photon rockets to propel spacecraft consists of three parts. In front is the sealed cockpit for the crew, where the astronauts work and live, in the middle is the normal hydrogen and anti-hydrogen cabin, and behind is the photon rocket engine. Due to the intense energy radiation when ortho-hydrogen and anti-hydrogen meet and annihilate, protective screens are set between living and working areas and ortho-hydrogen and anti-hydrogen storage tanks to avoid radiation damage to personnel, instruments and equipment, animals and plants. ?
The main component of photon rocket engine is a huge concave mirror with a diameter of tens of square kilometers. When the engine is working, positive hydrogen and anti-hydrogen are introduced into the focus of concave mirror, where they meet and annihilate, producing photons. Photons emitted in all directions are reflected by the mirror, forming a backward-ejected photon stream, and their reaction forces push the spacecraft to accelerate its flight. ?
Photon rockets are still just an idea. Although scientists have been able to produce antiprotons (antiprotons) in experiments at present, it is unbearable to produce a large number of antiprotons only by consuming all the energy. At the same time, there are many technical problems, such as a large amount of antihydrogen produced by storage and transportation. It is also very difficult to manufacture and assemble a qualified giant mirror.