of an asteroid whose orbit threatened Earth. In two different episodes, the series even speculated about exo-fossil extraterrestrial life discovered while exploring a distant asteroid and about ancient Earth-orbiting spaceship debris belonging to a non-human, space-faring civilization. Although the series was modestly budgeted, it was cleverly mounted with what, for its era, were very good special effects helmed by Louis DeWitt. Even decades later, the series can still be watched and appreciated for its attention to detail and accurate physics. Scientific accuracy A narrator explained in nearly every episode why the astronauts needed magnetic boots to walk in or upon their free-falling spacecraft, how a jet thruster backpack could propel an astronaut through the vacuum of space, why a wrong angle of attack could doom a spacecraft upon atmospheric re-entry, and so forth. The spacecraft in the program were shown gliding to a powerless landing on a dry lake bed, just like the real Space Shuttle nearly 25 years later. Footage of these landings used documentary film of the SM-64 Navaho cruise missile landing at Edwards AFB. On the other hand, dramatic license held sway on soundtracks, which repeatedly depicted sound in the airless vacuum of space: airlocks hummed, rockets roared, explosions boomed, and footsteps on the Moon's surface could be heard. Spacesuits being worn by the actors did not expand when exposed to the vacuum of space, as they would later during actual space walks. Production notes The program was produced by Ziv Television Programs, Inc., whose other notable series included Sea Hunt. The theme and recurring background music were written and conducted by David Rose. The series was produced by Lewis J. Rachmil. Among the guest stars was Keith Larsen of the CBS series Brave Eagle and The Aquanauts. Joyce Taylor played the role of Mary McCauley in the series, but Angie Dickinson played the role in the original pilot episode. Other guest stars include James Best, Whit Bissell, Paul Burke, James Coburn, Paul Comi, James Drury, Joe Flynn, Arthur Franz, Nancy Gates, Allison Hayes, Murray Hamilton, Brett King, Werner Klemperer, Gavin MacLeod, Joe Maross, Donald May, Bek Nelson, Simon Oakland, Denver Pyle, Robert Reed, William Schallert, Warren Stevens, Marshall Thompson, Harry Townes, and Robert Vaughn. Spacesuit costumes and special-effects footage of space vehicles (shot with miniature models) were later re-used in The Outer Limits, the science fiction film The Phantom Planet, and the 1969 drama Midnight Cowboy