But he noticed, too, that they burned chemical fuels in order to propel themselves.

All spaceplanes to date have used rocket engines with chemical fuels.

There are many other chemical fuels besides ethanol that bacteria could make as well, which could be used to generate electricity.

A more direct example is a bacterial fuel cell, which generates electricity directly, no recovery of chemical fuels needed.

It had to be, for it was using chemical fuels.

You remember that they started out with chemical fuels and that the first ship to the asteroids was built in orbit around Earth's moon?

Chemicals: hydrogen and oxygen, energetic and difficult to handle, but still chemical fuels.

There are a wide variety of both potential and current applications for solar chemical fuels.

At the same time engineers and chemists were working hard to develop new, high energy, chemical fuels to make engines push harder.

Hall thrusters use electricity rather than chemical fuels for generating thrust.