From an Economist article about newly released archives which detail futuristic tech projects in Britain that never reached fruition, a brief bit from 1968 about the MUSTARD (the Multi-Unit Space Transport And Recovery Device) space shuttle:

“READERS of a certain age may remember Gerry and Sylvia Anderson’s sci-fi puppet shows—Supercar, Fireball XL5, Stingray, Thunderbirds and Captain Scarlet—filmed, as the Andersons put it, in “Supermarionation”. Those who remember Captain Scarlet in particular may find one of the pictures here eerily familiar. English Electric’s Fighter Jet Take-Off Platform, a flying airfield, is not quite the Cloudbase from which the immortal captain operated. But it was intended, like its fictional counterpart, to launch and receive planes while itself airborne. It would have taken off and landed vertically in, say, a jungle clearing otherwise inaccessible to the aircraft piggybacking on it.

English Electric was one of the firms merged into what eventually became BAE Systems, and BAE has recently been through its archives and publicised some of the projects dreamed up in the glory days of the 1960s, when designers’ imaginations were allowed to run riot with little consideration of practicality or budget. MUSTARD (the Multi-Unit Space Transport And Recovery Device), for example, was designed by the British Aircraft Corporation (BAC). It could pass for something out of Fireball XL5 or Supercar—though it also resembles Virgin Galactic’s SpaceShipTwo which will, Virgin hopes, soon be taking paying passengers to the edge of space. It would have been a three-stage space-plane, though only one stage would have made it into orbit. The other two were reusable boosters.”

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“This man will be our hero, for fate will make him indestructible. His name: Captain Scarlet.”