A Backjack is a Class 3 Space Tug used by Gizmonic Institute to transport large payloads through space, not unlike a truck. Jonah Heston flies a yellow Backjack, transporting a cache of precious meteors before he is trapped by Kinga Forrester. The vehicle remains in Moon 13, its systems locked and its pre-set radio stations changed. As Kingachrome cannot be used to record footage for an opening sequence, Jonah is thrown into the Backjack and made to re-enact the events of his capture at the start of every episode under threat of cattle-prodding.
The Backjack model appears to be constructed from cardboard built onto a vintage cab-over-engine toy semi truck (possibly an Optimus Prime toy).