Gerald Smith believes that antimatter can bring solutions to problems. Antimatter, such as antiprotons and positrons, exists around physicists. Among all kinds of particles, there is an antiparticle with the same properties except electricity. Once all kinds of paired particles and antiparticles meet, they will release gamma rays, π mesons and huge energy at the same time. Gerald Smith noticed the enormous energy released when paired particles and antiparticles disappeared. Theoretically, the energy generated when particles and antiparticles disappear is 100 times that of nuclear fission and nuclear fusion. To accelerate a spacecraft with a general mass of 1000 kg to 0. 1 times the speed of light, only 9 kg of antimatter fuel is needed for calculation. But the situation is not so optimistic.

One of the problems is how to concentrate antimatter. Gerald Smith is engaged in research at CERN in Geneva, Switzerland. In the giant accelerator there, 10 produces 10 billion antiprotons every minute. However, antiprotons fly at 0./kloc-0 times the speed of light (incredibly high speed), so it is difficult to catch them. Smith put all-metal foil and gas in front of the antiproton to reduce its speed, and tried to seal the antiproton in a container made of magnetic field. If successful, he can enrich about 1 10,000 antiprotons in 10 minute. Unfortunately, 6,543,800 antiprotons are used as rocket fuel, which is really a drop in the bucket, and this work has to be repeated. Even so, there are two problems.

First of all, antimatter is charged particles, which will produce repulsive force. The higher the density of antimatter, the greater the magnetic field intensity used to restrain antimatter, which requires superconducting materials that can make the magnetic field intensity beyond imagination. So Gerald Smith thinks that antiprotons and protons should be combined to "make" antihydrogen atoms. Because antihydrogen atoms have no charge, there is no need to form superconducting materials with super-strong magnetic fields.

1996 1 10 In October, an international research team composed of scientists from Germany, Italy, Switzerland and other countries announced that they had successfully produced antihydrogen atoms by using the accelerator of CERN. They make antiprotons move at high speed and collide with xenon to produce electrons and positrons. When positrons and antiprotons have the same speed, they can form antihydrogen atoms. In their experiments, antihydrogen atoms exist for about 40 nanoseconds (1 nanosecond is one billionth of a second).

Secondly, the issue of quantity. Even if an antimatter factory with high efficiency and huge scale is built, it will take an unusually long time to produce 1 g antimatter. The international research team mentioned above made antihydrogen atoms in CERN, and only nine were produced in three weeks' experiment. Even with the facilities proposed by Gerald Smith that may be available within 10 years, only 1 microgram of antimatter can be produced every year. It will take 9 billion years to get 9 kilograms of antimatter rocket fuel.

After 9 billion years, it is hard to say whether the destination stars that humans intend to go to still exist. It seems that the idea that rockets can only fly with antimatter will be abandoned. Gerald Smith also asked, can antimatter be used in nuclear fission and fusion reactions? If antimatter is used, the device can be miniaturized and the rocket is easy to carry. Using antimatter to trigger a small explosion equivalent to 150 tons of TNT per second for several days, a manned spacecraft can be sent to Pluto in three years.

It is impossible to fly outside the solar system with solar sails.

In the final analysis, Gerald Smith's ideas all rely on rockets that use fuel to realize interstellar space flight. One of the people who questioned his idea was Pope Forward. Pope Forward was commissioned by NASA to study the feasibility of using antimatter. The antimatter rocket must react with the antimatter it carries and inject ultra-high temperature energy to the rear of the rocket. Pope Forward concluded that for antimatter rockets, the quality of the rocket and the heat resistance of the engine are fundamental issues.

1960, Forward first put forward the idea of spreading a huge sail made of aluminum foil and using the solar wind to promote flight-"riding" the charged particle stream continuously ejected by the sun, that is, "riding on a car". However, using solar sails to fly between stars has major defects. After leaving the solar system, the charged particles will become thinner, and the spacecraft will stop in a "windless" state. Obviously, it is impossible to use solar sails to go to other planets.

Have high hopes for the laser beam.

Later, Forward learned that the laser generated by ruby was brighter than sunlight, so he came up with a new idea: to swell the sails of a spaceship with a laser beam to gain propulsion. Since the laser beam hardly diverges and can be emitted from the solar system, necessary operations and management can be performed, and equipment can also be updated. More importantly, the spacecraft does not need to carry fuel, and the spacecraft can be made lighter. In the case of accelerating to sub-light speed, the small mass of the spacecraft is a very big advantage.

In order to send the spacecraft to γ Centauri, it is necessary to accelerate the spacecraft with a laser beam for about one year, so that the speed of the spacecraft can reach about one-third of the speed of light. After that, the laser beam was cut off and the spacecraft turned to inertial flight. When approaching γ Centauri, the outer ring of the sail is disconnected one after another, forming three concentric parts, moving the outermost part of the sail to the front of the spacecraft, and emitting a powerful laser beam again, so that the sail behind the spacecraft is covered with strong light, and the spacecraft obtains braking force. Of course, the laser beam behind the spacecraft still shines on the sail to form propulsion. However, the area of the outer sail of the spacecraft is 9 times that of the inner sail, and the braking force is greater than the propulsion force. After detecting γ Centauri, prepare to go home, and remove the round sail in the middle. At this time, the sail is still reflecting the laser beam, and the spacecraft can get the propulsion opposite to the route and fly back to Earth.

Is the idea of a huge sail realistic?

The fly in the ointment is that although there is no need to carry fuel, the propulsion obtained by the spacecraft relying on the laser beam is too small to help, so the advantage is offset by this defect. In order to realize interstellar flight by laser beam, a more powerful laser beam is needed, and the sail must be larger than expected.

According to Forward, about 65,438+0,000 laser emitters using solar energy have been installed in the orbit of Mercury. If these laser beams are combined with giant devices, it is possible not to develop giant laser emitters. However, in order to obtain the necessary propulsion, the ideal laser transmitter is 65.438+000 billion times more powerful than the current laser transmitter using solar energy! In addition, a huge lens must be set near Saturn to correct the divergence of the laser beam. The diameter of the sail must reach 1000 km, which is a whimsical plan. But Forward said that if you don't focus on the overall situation, you will accomplish nothing.

Regarding Forward's ambition, Ed Belbruno, a mathematician at the University of Minnesota in the United States, said: "Even if an unmanned probe with a mass of 1 1,000 kg flies, it needs a sail with a diameter of 1 1,000 km and a huge lens, which is just whimsical."

Is particle beam effective for one-way flight?

Bob Bruno emphasized that the idea of using laser beams is difficult to solve, and he is more concerned with particle beams. Heavy particles, such as protons, have mass without the speed of light For propulsion, protons with mass are more effective than photons without mass.

Hope Saplin and Dana Andler put forward the idea of "particle beam". They say that it is more effective to use giant rings made of superconductors for the light sails of spacecraft. The superconducting ring can form a doughnut-shaped magnetic field, and the particle beam will generate propulsion when it hits the magnetic field. A nuclear fusion reactor installed on an asteroid can be used to inject ultra-high temperature heated plasma gas in a certain direction to obtain a particle beam.

The disadvantage of particle beam is that it is easy to spread-because particles collide with each other to spread particle beam, the efficiency will decrease with the increase of distance, but it is still more propelling than laser beam. According to Andrew's calculation, his "particle beam idea" can accelerate manned spacecraft to one-third of the speed of light with only one-sixth of the energy required by Forward's idea. However, he also encountered a problem-the crew of the spacecraft must bear an acceleration as high as1000 g g.

There is still a major deficiency in the "particle beam thought". It is impossible to transfer energy to such a distant place as a star, that is, there is no return. Andrew said confidently that although it was a "suicide", it is estimated that there will still be volunteers. After all, there is a new discovery and it can be named after him. However, Andrew is suspected of having a tendency of "closed phobia", so I'm afraid he won't volunteer.

The remaining questions and ideas.

Berbruno insists that it is possible to send unmanned detectors with particle beams at present. Bell Bruno is conceiving a probe the size of a needle tip. If the detector only has a mass of 1 g and flies at sub-light speed, the increase in mass is not a big deal. But what if something as small as a needle tip is lost? Can I carry communication equipment or something on it? There are many problems.

In addition, it has been proposed to use the "wormhole" connecting black holes and white holes, and use anti-gravity to bend time and move at high speed. Recently, various schemes have emerged one after another. As far as the current level of human science and technology is concerned, interstellar space flight is essentially impossible, which also shows that we have not mastered the specific knowledge and technology to realize this dream, and human beings have to explore for a long time as before.