Because the light from the sun provides endless energy, a spacecraft with a large solar sail can eventually laser pointer travel at a speed of 240,000 kilometers per hour. This speed is 4-6 times faster than the fastest spacecraft propelled by rockets today. That is, it is 6 times faster than the second universe and 4 times faster than the third universe. The solar sail receives the light pressure, it can not only change the orbit of the spacecraft when needed, but also accelerate the flight continuously.
However, due to technical limitations, the area of the solar sail cannot be made too large during the construction process, and it is very difficult for solar sails to be used in practical applications. Today, the progress of this research and development is not fast. In the past 20 years, the United States and Russia have conducted several solar sail power tests, with successes or failures, but they have only tried them in low-Earth orbit.
The farthest one is currently the “Icarus” solar sail launched by Japan on May 21, 2010, but it has only reached the vicinity of Venus. So Solar Sail is far from reaching the Centaur. The photon rocket uses the annihilation reaction of matter and antimatter to produce photons by itself and eject a stream of photons backwards through a huge concave mirror. However, research based on this assumption has not made substantial progress in decades. Due to the very large technical problems of green laser pointer, photon rockets will be difficult to achieve for a long time in the future.
In Pang Zhihao’s view, the spacecraft proposed by Hawking is not actually a spacecraft. It is just a flying object a few centimeters square, which will make it impractical to use the sun to drive it. Because the thrust generated by a single photon is extremely small, for example, at the distance from the earth to the sun, the thrust generated by light on a square meter of sail is less than the weight of an ant.
In order to solve the problem that sunlight as an energy drive cannot meet the requirements, the “Breakthrough Photo Star” plan puts forward the concept of laser propulsion. However, the envisaged laser propulsion technology is also very complicated in engineering, which makes it difficult to become a reality in actual engineering.