Mr Spaceship

"Mr. Spaceship" is a science fiction short story by American writer Philip K. Dick, first published in Imagination in January 1953, and later in The Collected Stories of Philip K. Dick.
The story is set in the distant future, where humanity is at war with "Yuks", an alien life form which does not use mechanical spaceships nor constructions but instead relies on life forms to power their technology. The war has been going on for a long time and humanity has not been able to come up with a solution against the life-form based ships and mines that the Yuks use. One day a team of researchers led by Philip Kramer decide to build a spaceship which is powered by a human brain and they find the ideal candidate in Kramer's old professor, a dying man who volunteers to donate his brain to the project.