Main-group element Main-group element In chemistry and atomic physics, the main group is the group of elements whose lightest members are represented by helium, lithium, beryllium, boron, carbon, nitrogen, oxygen, and fluorine as arranged in the periodic table of the elements. The main group includes the elements (except hydrogen, which is sometimes not included) in groups 1 and 2 (s-block), and groups 13 to 18 (p-block). The s-block elements are primarily characterised by one main oxidation state, and the p-block elements, when they have multiple oxidation states, often have common oxidation states separated by two units. Main-group elements (with some of the
Space Shuttle Solid Rocket Booster Rocket Motor" (RSRM). The prime contractor for the SRB motor segments was ATK Launch Systems' Wasatch Division based in Magna, Utah. United Space Boosters Inc. (USBI), a division of Pratt and Whitney, under United Technologies, was the original SRB prime contractor for SRB assembly, checkout and refurbishment for all non-solid-rocket-motor components and for SRB integration. They were the longest running prime contractor for the Space Shuttle that was part of the original launch team. USBI was absorbed by United Space Alliance as the Solid Rocket Booster Element division in 1998 and the USBI division was disbanded at Pratt & Whitney