An analysis is presented of a little studied class of solar concentrators with high potentiality for space application, namely space fabricated gas-filled spherical plastic lenses, called ″bubbles″ . A bubble will behave like a lens, as long as the inside has a higher refractive index than the outside. In the vacuum of space, a gas or vapor will refract incoming light rays and, therefore, can be used as lens material. 7 refs.