ECS radiators, which were white. The EPS and ECS radiators were redesigned for Block II. Block I had three larger EPS radiators located on Sectors 1 and 4. The ECS radiators were located on the aft section of Sectors 2 and 5. The Block I fuel cells were located at the aft bulkhead in Sector 4, and their hydrogen and oxygen tanks were located in Sector 1. Block I had slightly longer SPS fuel and oxidizer tanks which carried more propellant than Block II. The Block II aft heat shield was a rectangular shape with slightly rounded corners at the propellant tank sectors. The Block I shield was the same basic shape, but bulged out slightly near the ends more like an hourglass or figure eight, to cover more of the tanks. CSMs produced See also Orbital module Reentry capsule Space capsule Space suit Space exploration U.S. Space Exploration History on U.S. Stamps Apollo Lunar Module Footnotes Notes Citations Crewed spacecraft Missions to the Moon Apollo program hardware Spacecraft launched by Saturn rockets Apollo–Soyuz Test Project Spacecraft that orbited the Moon