Rocket Booster Rate Gyro Assemblies
The solid rocket
booster RGAs are used exclusively during first-stage ascent as feedback
to find rate errors from lift-off to two to three seconds before
SRB separation. There are three RGAs on each SRB, each containing
two identical single-degree-of-freedom rate gyros for sensing rates
in the vehicle pitch and yaw axes similar in function to the orbiter
RGAs. The maximum outputs for the SRB RGAs are 10 degrees per second.
The SRB RGAs
sense pitch and yaw rates, but not roll rates, during the first
stage of ascent. Because the SRBs are more rigid than the orbiter
body, these rates are less vulnerable to errors created by structural
bending. They are thus particularly useful in thrust vector control.
The three RGAs
in each SRB are mounted on the forward ring within the forward skirt
near the SRB-external tank attach point.
The SRB RGA
SOP converts the 12 voltages representing a rate into units of degrees
per second. These rates are used by the flight control system during
first-stage ascent as feedback to identify rate errors, which are
used for stability augmentation. The pitch and yaw axes and a combination
of rate, attitude and acceleration signals are blended to provide
a common signal to the space shuttle main engines and SRB thrust
vector control during first stage. In the roll axis, rate and attitude
are summed to provide a common signal to the SSMEs and SRB thrust
Each of the
SRB RGAs is hard-wired to a flight aft MDM to the GPCs through flight-critical
buses 5, 6 and 7. In the GPCs, the SOP applies the rate compensation
equation to each of the left or right pitch and yaw rates. The compensated
rate signals are sent to redundancy management, where the mid value
software scheme selects the best data for use and failure detection.
The SRB RGAs
are commanded to null and switched out of the flight control system
two to three seconds before SRB separation; SRB yaw and pitch rate
data are then replaced with orbiter pitch and yaw RGA data.
red caution and warning light on panel F7 will be illuminated to
inform the flight crew of an RGA failure.
The RGA contractor
is Northrop Corp., Electronics Division, Norwood, Mass.