Can Hawking's Lightsail Spacecraft and its "Star Shooting Plan" be realized?

In 20 16, physicist Stephen hawking put forward the idea of exploring the universe with sub-light speed micro spacecraft. Theoretically, using the radiation pressure of light to push the sail can accelerate the spacecraft and realize interstellar space flight.

This principle was developed by American physicist Robert? The forwarding suggestion is in 1962. He thought, since sailboats sail on the sea by the wind, why not use powerful lasers to propel the spacecraft to soar in space? When the photon of the laser hits the spacecraft, the impulse brought by the photon pushes the spacecraft forward and accelerates its operation until it rushes out of the solar system. This was later considered by some scientists as the best way to reach other galaxies.

In this method, the spacecraft does not need to carry fuel by itself, but carries sails. The laser array located on the earth or the moon base is responsible for emitting high-energy laser and focusing it on the sail. It is said that with this technology, the spacecraft can reach proxima centauri within 80 years, and the highest speed can reach 1/5 the speed of light.

Based on many technical and economic factors, scientists believe that micro-optical sail detector may be the first choice for future exploration outside the solar system.

20 16 April, Russian billionaire Yuri? Yuri milner initiated a project with the famous Professor Hawking and other scientists? Star shooting plan? (breaking through the star photo). Facebook founder Mark? Mark elliot zuckerberg also joined the board of directors of the plan.

They hope this launch can explore the nearest star to the sun? Proxima centauri? Light sail ship. This is Hawking's? Star shooting plan? .

1. How does the micro-sail spacecraft work?

Modern physics proves that light is composed of photons with momentum and has no static mass. When photons hit a smooth plane, they can change direction like a ping-pong ball bouncing off a wall and give the hit object a corresponding force.

The working principle of the optical sail used in the star shooting program is different from that of the solar sail, because the laser beam does not diverge and weaken with the increase of distance like sunlight. The lidar array erected on the earth can ensure that the spacecraft can reach the cruising speed of sub-light speed.

According to the data, the light sail spacecraft launched by Hawking's shooting star plan is very small, weighing only a few grams, which is about the size of ordinary stamps and very thin. With the help of nanotechnology, although the spacecraft is small, it contains all the most important components of an interstellar probe, such as cameras, processors, batteries and other components. The spacecraft will carry a sail with a side length of about 4 meters. The laser array on the earth focuses the beam directly on the sail and accelerates the spacecraft to 20% of the speed of light in just a few minutes.

The designed sail weighs only a few grams and may be only a few hundred atoms in diameter. In the project of shooting stars, the area of laser array on the ground is about 1 km2, and it is estimated that millions of degrees of electric energy will be stored in each launch. This huge figure is equivalent to the power generation of Daya Bay Nuclear Power Station 1 hour. The difficulty of this scheme lies in how to focus the laser on the small sail correctly.

The Star Shooting Project envisages that thousands of such explorers will be launched into Earth orbit by conventional rockets at one time. Besides light sails, they also have core equipment? Starchip: A heavy chip, which carries a camera, a processor, a photon propulsion device, a power system, navigation and communication equipment, etc.

When the detector sails in orbit, a group of high-energy lasers will accelerate the detector in turn, lasting several minutes at a time, every 1 ~ 2 days. Each detector is equipped with a planet or asteroid sensor, and the data will be sent back to Earth by the laser carried by the detector.

Second, the exploration objectives and planning

The goal of Hawking's shooting stars program is to develop thousands of miniature starships, fly to proxima centauri and send back pictures.

If successful, scientists will be able to judge whether there are Earth-like planets and life in Alpha Centauri.

Alpha Centauri galaxy is about 4.3 light years away from the Earth. Scientists are confident that the speed of the micro spacecraft carrying photography and communication equipment in the star shooting plan will reach 1/5 of the speed of light. This speed will be much higher than the most advanced spacecraft at present.

These thousands of miniature interstellar spacecraft were first carried into Earth orbit by rockets, and then sent to proxima centauri through laser arrays on the ground. These ships are very fast, but due to the limited batteries, they can't enter proxima centauri orbit, so they can only fly nearby. The high-speed camera carried on the spacecraft will take pictures of proxima centauri and its planets in time as it flies by.

After that, the spacecraft will enter the transmission mode and send the photos back to Earth. The spacecraft will rely on its own energy to transmit photos, which requires it to integrate a small radioactive element battery. When the spacecraft sends back photos, the optical sail of the spacecraft will be used as the transmitting antenna, and the laser transmitting array on the earth will be used as the receiving antenna to collect the images sent back 4 light years away.

Three. Prospects and challenges

In Hawking's star shooting program, if we master the laser sail technology, then we humans may no longer have to worry about the fuel problem of long-distance flight.

If all goes well, this overflight mission will reach Alpha Centauri about 20 years after launch and send back photos of the planets found in this galaxy. This means that as long as we master this technology, we are not far from alien life.

So far, the design of the shooting star program is far from being formed, and many schemes are only conceptual, facing challenges from laser, materials, communication and other fields. The cost of a square kilometer laser array is so amazing that it is impossible for a star-shooting spacecraft to plan to launch in the near future.

The initiator of the Star Shooting Project predicts that in the next 50 years, nanotechnology, battery technology, laser technology and communication technology will all develop according to Moore's Law, that is, the product performance will double at regular intervals, while the price will remain unchanged. If Moore's Law remains valid, the sponsors of the Shooting Star project estimate that when the project really starts, the project cost will be greatly reduced, similar to the most expensive large-scale scientific research facilities (such as the Large Hadron Accelerator).

However, many scientists have also strongly questioned this ambitious plan to shoot stars.

For example, Yang Yuguang, a researcher at the Second Academy of China Aerospace Science and Technology, thinks that Hawking's idea is almost impossible in engineering. Even if an object with a mass of 1g is accelerated to the speed of light of 1/5 with an efficiency of 100%, a huge amount of energy equivalent to more than 400 tons of TNT is needed. In addition, it may be impossible to accelerate an object by optical means in engineering. In addition, even if a photo is taken, on the basis of such a weak signal transmitter, it is difficult for this photo to be uploaded to the earth and received by us.

Physicist Robert? Foward, on the other hand, believes that it will take many years for this technology to be truly applied to engineering, and it may not be realized until the 22 nd century.

Four. Concluding remarks

In any case, Hawking's star shooting plan is undoubtedly very optimistic about the future technological development, but it needs to be known that even an incomplete version of the star shooting plan will greatly change the status quo of planetary exploration. Does the speed of light of 1/5 mean that the micro spacecraft can fly to Mars in only 1 hour, or can it be completed within one year? New vision? Nine-year trip to Pluto. People can even make the spacecraft bigger, so that other celestial bodies in the solar system can still be detected in an acceptable short time.

At the same time, the laser array used in the star shooting program will also be the best optical telescope for mankind. Once completed, its resolution will exceed that of the next generation of large-scale optical infrared telescopes, and it will play a great role in searching for extraterrestrial planets.