By Ewan McCraken, Space and Military Editor

WASHINGTON (Reuters) - Pentagon officials are secretly considering a final, drastic modification to the Hubble Space Telescope, one involving the installation of several "black box" modules that would, in effect, transform the peaceful telescope's mission from observation to national defense.

Although technical details of the plan are top secret, one anonymous defense contractor described it as transforming the Hubble into a sort of "super BB gun" in earth orbit.

"One researcher compared it to a 'Polish cannon,' but that's not politically correct," said the source, citing the size of the proposed projectiles, which are far smaller than a tennis ball. In fact, the magnetically accelerated kinetic projectiles are "closer to the size of a pea or a BB." The planned ammunition module would carry thousands of tiny projectiles, making the Hubble a formidable space weapon.

One engineer was adamant. "I used to plink bottles when I was a kid, but those BB's weren't going seventeen thousand miles per hour," he said.

Plans for "Project Daisy" are reported to be in the early stages, but a one source commented, "When it comes to DARPA, you never know."

Reasons for the sudden and dramatic shift in Hubble's mission included complaints that the orbiting observatory was technically obsolete, that its optics were essentially worn out, that it was "taking up space" in a prime orbit location, and that firing little pellets from space would be "really cool."

As is customary, Pentagon officials refused comment.