The Integrated Apogee Boost Stage (IABS - alternately, Integrated Apogee Boost Subsystem) was an American rocket stage used for the launch of Defense Satellite Communications System III satellites to geostationary orbit when using a launch vehicle without an upper stage capable of delivering them there directly. Earlier DSCS III satellites had launched on the Titan 34D (using the Transtage or Inertial Upper Stage) and Space Shuttle Atlantis (using the Inertial Upper Stage), which were capable of delivering them directly to geostationary orbit - as such, the satellites were not capable of moving from geostationary transfer orbit to geostationary orbit themselves. Because of this, launch of these satellites on the Atlas II and Delta IV families required an apogee kick stage - the IABS - to be added to the satellite. The IABS was developed by GE Astro Space, who also manufactured the DSCS III satellites it was designed for.
Design
IABS consisted of a flat, disc-shaped stage powered by two pressure-fed R-4D rocket engines, fed from a ring of spherical composite overwrapped pressure vessels containing nitrogen tetroxide and monomethylhydrazine propellants. The stage was spin-stabilized, rotating at 20 rpm. An onboard solar array around its ring-shaped exterior, separate from that of its payload satellite, allowed IABS to remain operational for up to 12 days, granting flexibility in mission planning. IABS was originally intended to make two burns while delivering DSCS III satellites - however, fuel feed problems after the first burn of its first mission rendered the second burn impossible, requiring the payload to maneuver to its final orbit on its own using its reaction control system. On later flights, these two burns were combined, avoiding this problem.
Flights +Flights of the Integrated Apogee Boost StageIABS DesignationDatePayloadLaunch VehicleLaunch siteOutcomeIABS-01Feb 11, 1992DSCS III B14Atlas IILC 36APartial FailureIABS-02Jul 2, 1992DSCS III B12Atlas IILC 36ASuccessIABS-03Jul 19, 1993DSCS III B9Atlas IILC 36ASuccessIABS-04Nov 28, 1993DSCS III B10Atlas IILC 36ASuccessIABS-05Jul 31, 1995DSCS III B7Atlas IIALC 36ASuccessIABS-06Oct 25, 1997DSCS III B13Atlas IIALC 36ASuccessIABS-09Jan 21, 2000DSCS III B8Atlas IIALC 36ASuccessIABS-08Oct 20, 2000DSCS III B11Atlas IIALC 36ASuccessIABS-10Mar 11, 2003DSCS III A3Delta IV MediumLC 37BSuccessIABS-07Aug 29, 2003DSCS III B6Delta IV MediumLC 37BSuccess
See also Transtage Inertial Upper Stage Transfer Orbit Stage
References