The Scout X-2B was an American expendable launch system which was flown during 1963. It was a four-stage rocket, based on the earlier Scout X-2, but with an Altair 2A fourth stage in place of the Altair 1A used on the X-2. It was a member of the Scout family of rockets.The Scout X-2 was an all-solid rocket, with an Algol 1D first stagea Castor 1A second stage, an Antares 2A third stage, and an Altair 2A fourth stage.