Number 283 (Story #2), August 27, 1996 by Phillip F. Schewe and Ben Stein A TRANS-SOLAR SPACE CRAFT , one sallying forth beyond the outer planets, would probably need the help of some novel propulsion system, such as the use of sails which would enable the craft to reach high speeds by patiently but effectively reflecting sunlight. Under study at NASA, the Thousand Astronomical Unit mission would have a number of goals. One would be the closeup study of the Kuiper Belt of asteroids (at a distance of about 40 AU). A second goal would be to locate the heliopause, the zone (at around 110-160 AU) where the outgoing solar wind is halted by the incoming interstellar wind. Third, at a distance of several hundred AU, a 1-m telescope on the craft could by triangulation accurately measure distances to stars across much of the Milky Way. (Currently parallax measurements of distances are limited by the baseline of the Earth's orbit to stars out to about 200 light years.) Another goal would be the use of the sun as a gravitational lens for imaging distant objects behind the sun. Moreover, tiny modulations in the return signal from the craft (3 days' transit for light over a path of 500 AU) might encode information about passing gravity waves. (Astronomy, August 1996.)