Rails and space go together like fish and chips. I never really got into them as a kid but there were lots to choose from like Spaceniks, Mighty Mike [over at Sam's Toybox] and Grippidee Gravidee. The Grippidee Gravidee Deluxe Set pictured above included a cool looking space jet, which had a sort of Probe force 2 look to it [bottom right in the box]. The whole set looks huge!
Even better was the Zero-X MEV-like space cab that featured in the Tomy version pictured below. From around 1969 the set came in both single and double cab sets. The cab, called the Space Express, is amazingly like the Century 21 toy and I can't help thinking that Derek Medding's design likely influenced it.
Below's a close-up of the plastic C21 MEV [right], the Imai die-cast MEV [left] [thanks Jim] and the Tomy Grippidee Space Express.
There's a a cool slide-show of the Double cab version on You Tube and an ever cooler image of it on a 1969 catalogue page stuffed with space toys over on the gigantic Alphadrome.