Harry Morgan
General Stilton
Roddy McDowall
Mr. Stallwood
Ronnie Schell
Jake (Voice) / Sgt. Duffy
James Hampton
Capt. Anderson
Howard Platt
Col. Woodruff
William Prince
Mr. Olympus
Arnold Soboloff
NASA Executive
Alice Backes
Farmer's Wife
Roger Price
1st E.R.L. Expert
Jerry Fujikawa
2nd E.R.L. Expert
Rickie Sorensen
Technician
Fred L. Whalen
Sarasota Slim
Gil Stratton
1st NASA Scientist
Jana Milo
2nd NASA Scientist
Sorrell Booke
Presiding Judge (uncredited)
Jackson Bostwick
Additional Voices (voice) (uncredited)