Detail of an ambient helium sphere the S-IVB's thrust structure.
This photo dates to late 2005. Note the LH2 chilldown pump line
coming from inside the aft skirt at the upper left the photo and the
cylindrical hydraulic system accumulator-reservoir at the lower right. Prior
to Barack Obama
cancelling the Constellation Program, MSFC engineers removed
some components from this S-IVB stage for study. These appear to have
been among the components removed, as my photos from 2006 show that these
components had been removed.