Zero-X (spelling variants include "Zero X" or "ZeroX") is a fictional Earth spacecraft that first appeared in two of Gerry and Sylvia Anderson's Supermarionation productions, the 1966 film Thunderbirds Are Go and the 1967 television series Captain Scarlet and the Mysterons. Although publicity material for the various Supermarionation series, and the TV Century 21 comic, made references to connections between the Thunderbirds and Captain Scarlet canons, Zero-X is the only official link between the two series. Fictional history The first crewed craft to land on Mars, the metallic-blue Zero-X comprises a number of detachable sections. The main body houses the chemical engines which provide the craft with the thrust required for lift-off and the subsequent journey to Mars. The Martian Excursion Vehicle (MEV; later renamed Martian Exploration Vehicle) is attached to the front of the main body where it serves as the spaceship's main control centre during spaceflight. During atmospheric ingress or egress, two remotely controlled "lifting bodies" (self-propelled "flying wing" aerofoils) are attached to the main body at the front and rear of the craft. Finally, a heatproof nose cone with an aluminium exoskeleton protects the MEV during take-off and provides further aerodynamic flow to the vehicle in atmospheric ascent; it is jettisoned just before leaving the Earth's atmosphere, and is the only non-reusable part of the spacecraft. The lifting bodies act as wings to allow the craft to operate from a runway like a conventional aeroplane, and carry multiple jet engines to reduce the amount of fuel needed for the main body's chemical engines. They separate from the main body when the craft is at a sufficiently high altitude and fly back to base; on re-entry, they rendezvous with the spacecraft and dock with it to again act as wings and provide propulsion in the atmosphere. On reaching Mars, the MEV detaches from the main body, which is left in orbit piloted by a single astronaut, and descends towards the planet's surface. At the surface the MEV extends caterpillar tracks to negotiate the rocky terrain. The concept of a reusable first-stage lifting body (or in this case, bodies) boosting a smaller spacecraft to high altitude for more efficient use of its propulsion was in direct competition with the vertical-ascent rocket doctrine of the 1960s as a means of achieving spaceflight, and for some time lost out to it, as even the Space Shuttlewhich landed as a conventional aircraftmakes