Atlas vehicles are fueled by a mixture of liquid oxygen and kerosene (RP-1). The latest
HAS configuration also incorporates Castor IVA solid-rocket motors. The early Atlas
core vehicle included a sustainer, verniers, and two booster engines, all ignited prior to
liftoff. In the Atlas II, IIA, and HAS vehicles, the vernier engines have been replaced by
a hydrazine roll-control system. Of the four Castor SRBs on the HAS, two are ground
lit and two are air lit some 60 seconds later. Atlas vehicles are now typically integrated
with the Centaur upper stage vehicle that is fueled with liquid oxygen and liquid
hydrogen. Earlier flights used an Agena upper stage.

The entire Atlas history through 1995 is depicted rather compactly in bar-graph form in
Figure 37. The solid-block portion of each bar indicates the number of launches during
the calendar year for which vehicle performance was entirely normal, in-so far as could
be determined. The clear white parts forming the tops of most bars show the number
of launches that were either failures or flights where the launch vehicle experienced
some sort of anomalous behavior. Every launch with an entry in the response mode
column in Table 41 falls in this category. Such behavior did not necessarily prevent the
attainment of some, or even all, mission objectives.

                     50
                                           !                                                                                                                                                                                                                                i
                                           !                                                                                                                                                                                                                                !
                     45     on••••••----;•••••          ••••.. ••;• •   •••.. ••••••;••••••••••••••••;••••••••••••••••;.. ••• ....••••••••;••••••••••••••••;•••••••••••••••••;•••




                     40 ...... / . · -1 · -l7.iFw1lre1Alomrui ............. )...
              CJ)
             C:      35
                                           !
                            •• ..••••• .... f'• o   '    o uoo t
                                                                :                          !                                  • Norrr,al P~rforrtjance !
                                                                        ••••• .. ••••-!--••••••••••--••• ••••••• ..•••h••'l••••.. •••••••••••t••..•••••• ..••••i•••••••••••n••••~•••

             0
             ·u;                           •                    i                          I                                  I                                  I                                  I                                   I                                  I
             CJ)

             ~
              CJ)
                     30     · · · · · · .. ··                                              i                                  i                                  i                                  l                                   i                                  i
              m                                                                             j                                 i                                   i                                  i                                  i                                  i
             ':.:;   25     ............       •                           • • • • • • • • ,:.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,!'. . . . . . . . . . . . . . . . . . . . .




             -
                                                                                           !                                  !                                   !                                  i                                  i                                  l
             <(
             0       20                H-1+---•··---••
                                                                                           i                                  !                                 ! i
                                                                                  ••••~•••• .. ••••••••••t•••••••••U••••• ,•••••••••••••••••t••••••••••• ..•••i:•••••••••••••••••, •••
                                                                                                                                                                                                    i                                                                      !
             "-                                                                            1                                  i                                   l                                  !                                 ·!                                  i


                                                                                  .... !
                                                                                       ·................!·................ !·.................!·................!                                                                                                         !·
             Q)
             .c                                                                                                                                                                                                                         ' ................. ...
             E       15
             ::::,
             z
                     10                                                                   I                                  I                                   I
                                                                                    ••'••······················· ··••'••··························· ..... ·.................
                                                                                                                                                                                                    !                                  I                                   1




                      5
                                                                                           1
                                                                                                                             I•
                                                                                                                                                                 1
                                                                                                                                                                                                    I I
                                                                                                                                                                                                 •• ···············1·····


                      0
                       55             60                    65                     70                                  75                                 80                                 85                                 90                                 95
                                                                        Launch Year
                                       Figure 37. Atlas Launch Summary




9/10/96                                                                                              102                                                                                                                                                                              RTI