Ion Engines

Ad Astra's Variable Specifc Impulse Magnetoplasma Rocket (VASIMR)

 

It seems that in the long run, space exploration or travel will never work with the speeds we have now. Rocket engines using chemical fuels just don't cut it when it comes to traveling far, going to other planets that would take years to get to. Ion engines are not that new of a concept, the idea's been around since the beginning of the 20th century.