Trident I C4
When the TS rocket's burn and separation is completed,
the PBCS positions the ES, so the guidance system
can get it's bearings from the stars.
Guidance then determines trajectory and
calculates corrections for the ES flight path.
C4's ES then enters high-thrust mode, w/
PBCS driving it to the correct velocity for reentry.
During this mode, the ES flies "backwards"
(RVs face aft to the trajectory).
When the correct velocity is obtained,
C4's ES goes into a vernier mode.
(ES is adjusted so that the MIRV will be deployed
at the proper altitude, velocity, and attitude.)
After each reentry vehicle drop,
the ES backs off and moves to into
position for the next reentry drops.
To eliminate the PBCS plume from impacting the RV
the ES undergoes a Plume Avoidance Maneuver (PAM).
Trident II D5
W/ the D5, the ES uses its PBCS to maneuver
for stellar sighting to allow the guidance
system to update the original inertial guidance
as received from the SSBN.
The guidance computer tells the flight control system
to reorient the D5 ES and enters a high-thrust mode.
However, in the D5 case, the ES flies forward.
(RVs are basically down the line of the trajectory.)
As in C4, the D5 ES (when it reaches proper velocity)
enters the vernier mode to deploy RVs. |
