Though unmanned spacecraft have already landed on the moon, photographed Mars and crashed onto Venus, the more distant planets of the solar system are still beyond the practical grasp of man. None of the rockets now used in either the U.S. or Russian space programs are powerful enough to reach them. Even the huge and yet-unproven Saturn 5, which will carry men to the moon, would require an additional stage to send only a tiny payload on one-way trips, and would require six years to reach Saturn, 16 years to Uranus and 30.7 years to Neptune. But the planetary timetable may...
To continue reading:
or
Log-In