The most powerful solar-electric spacecraft is coming.

"An artist’s rendering of Gateway with the Power and Propulsion Element’s advanced thrusters propelling the lunar space station to the Moon. Credit: NASA/Alberto Bertolin" (ScitechDaily, NASA Builds the Most Powerful Solar Electric Spacecraft Ever)

Solar electric spacecraft are systems that can offer a clean and probably safe way to travel inside the asteroid belt. In the simplest possible systems, the solar power rockets use parabolic mirrors or lenses to vaporize and expand the propellant. Those rockets cannot operate in the atmosphere. In the more advanced system, solar power rockets use electricity from solar panels to give electricity to electrochemical- or ion engines. 

In electrochemical rockets, the system can use electricity or radiation like lasers or microwaves to give thrust. In electric jet engines, the electricity expands the air or some other gas. The electrochemical rockets are similar systems to the electric jet engines. 

But the front side of those systems is closed. The flap that closes the electric jet engine nose denies the exhaust gas flow forward. The problem with electrochemical rockets is their electric source. 

Nuclear power or solar power can be the tool that makes this kind of system real. The rocket itself can expand any gas like nitrogen or liquid nitrogen. The problem is that this kind of system requires very long wings. That it can make enough thrust.

The ion sail 

The ion sail aims ions into the solar sail. 

The ion system can aim ions at the solar sail. When an ion cannon sends ions to the solar sail, it can pull the craft with higher thrust than in cases, where the system aims ions backward. 

The ion engines use ions or anions to accelerate the spacecraft. Unlike those electric chemical engines, their thrust is very low. But there is the possibility to make the ion engine with higher thrust. That kind of ion system can blow ions to the solar sail. And that makes it possible to travel through the solar system. 

The solar electric spacecraft uses solar power to give electricity to its engines. The engine itself can use things like hydrogen or any other gas as a propellant. The system can expand and vaporize that propellant using electric arcs, lasers, or microwave systems.  

Solar electric spacecraft don't necessarily use ion engines. But solar power can also give electricity to particle accelerators. They can act as ion engines. Or those systems can create antimatter, like positrons that the system injects into propellant. 

That thing can give a very big punch to the propellant. That kind of solar electric system opens a path to the inner solar system. They can also act as the accelerator stages for nuclear rockets that travel to the outer solar system. 

The system can use solar power to accelerate the craft to the asteroid belt. And behind that it can separate the nuclear-powered stage and start to use nuclear power. The solar-power spacecraft can operate in space between Earth and Mars and the inner solar system. 

https://scitechdaily.com/nasa-builds-the-most-powerful-solar-electric-spacecraft-ever/