quem sabe o futuro irmão
is a prototype of Lockheed’s other spaceplane, the single-stage-to-orbit reuseable aerospace vehicle, the National SpacePlane . Lockheed-Martin does not say too much about its winged, delta-shape X-33 VentureStar, except to say that we are building it. To be at that stage of development for its public-program SpacePlane, clearly Lockheed-Martin has already long since built prototypes, as well as an unacknowledged military version, which I have dubbed the X-33A. The ’A’ suffix stands for antigravity.
http://en.wikipedia.org/wiki/Lockheed_Martin_X-33Ps. Eu sei que este projecto já foi cancelado, mas já li que talvez não, por isso é que pus aqui.