Solar sails and their technical problems.

In some ideas: solar sails. They can travel inside the solar system. The idea is that those sails can be very large radio telescopes. Or they could carry large interferometer antennas out from the asteroid belt. 

There are visions of solar sails using laser acceleration. It can travel to other solar systems. When a solar sail travels very fast. Photons that impact the solar sail start to transfer less energy into it. When the sail reaches a speed. About 75% of the speed of light. The laser beam that accelerates it starts to lose its energy. 

The Doppler effect changes the wavelength of the impacting laser beams. The effect is similar. As we were throwing balls to an escaping car. When an object escapes, the particle pushes energy to that object more slowly. And that decreases acceleration. Photons act like all other particles, like balls. When the solar sail moves faster. The laser beam that hits it starts to lose its power. 

The calculations show that low-energy photons can slow the solar sail. This means that when solar sails travel outside the solar system. The same light that accelerated it turns to slow the solar sail. So does light accelerate or slow it down? That depends on the energy level of the photons. 

If the photon's energy level behind the solar sail is higher than its front side. The photon accelerates the solar sail. If that energy level behind the solar sail is lower. Those photons transfer energy into themselves. And that slows the solar sail. But another thing that can slow the solar sail is the gravitation of the entire solar system. 

When the solar sail starts its journey, there is less mass behind it. Than when the solar sail travels out from the solar system, the entire mass of that system turns behind it. This means that the mass of the Kuiper Belt. Oort clouds. And planets, the Sun, and all asteroids start to pull the solar sail behind it. Another thing that can slow the solar sail is the starwind. The starwind is the particle flow from other stars. 

That particle flow impacts. The heliopause from outside it. That can also push the solar sail back. So if that particle flow is stronger than the particle flow from the solar system. That thing pushes the solar sail back. This means that solar sails may need something. That pushes them forward. Those things can be hydrogen bombs that are left in the solar sail’s trajectory. But the problem is always the same. The acceleration means that those systems can push less energy to the solar sail. For the same reason as why the laser beam cannot transfer energy into it. 

When we think about the systems that carry laser systems. The only problem is that. Those systems would form a closed system. The laser system. That shoots a laser beam into the mirror at the front of the craft. It must be released when it is shot. When that laser is released. That system is not closed anymore. And those single-use lasers. They can push the craft forward. The idea is that. The laser is in the frame of the solar sail. Then that system. It will be separated. When the system. It needs the power. 

Those single-use lasers. They can be like in a magazine in the solar sail. Then those systems. They can be released. The laser. It can get its energy from a rocket engine. That pumps energy into it. When the laser is separated, the rocket starts. And it also gives energy to the laser. The rocket pushes that laser system backward. 

The fact is that. Solar sails can be interesting tools. To travel inside the solar system. But stars are always a little bit too far. Inside the solar system. Those solar sails can use solar energy and particle flows. This means that interstellar flight will not be possible until the entire solar system is explored. 

https://scitechdaily.com/the-strange-force-that-could-slow-interstellar-solar-sails/