| Range Safety
shuttle vehicle has three RSSs. One is located in each SRB and one
in the external tank. Any one or all three are capable of receiving
two command messages (arm and fire) transmitted from the ground
station. The RSS is used only when the shuttle vehicle violates
a launch trajectory red line.
An RSS consists of two
antenna couplers, command receivers/ decoders, a dual distributor,
a safe and arm device with two NSDs, two confined detonating fuse
manifolds, seven CDF assemblies and one linear-shaped charge.
The antenna couplers
provide the proper impedance for radio frequency and ground support
equipment commands. The command receivers are tuned to RSS command
frequencies and provide the input signal to the distributors when
an RSS command is sent. The command decoders use a code plug to
prevent any command signal other than the proper command signal
from getting into the distributors. The distributors contain the
logic to supply valid destruct commands to the RSS pyrotechnics.
The NSDs provide the
spark to ignite the CDF, which in turn ignites the LSC for shuttle
vehicle destruction. The safe and arm device provides mechanical
isolation between the NSDs and the CDF before launch and during
the SRB separation sequence.
The first message, called
arm, allows the onboard logic to enable a destruct and illuminates
a light on the flight deck display and control panel at the commander
and pilot station. The second message transmitted is the fire
The SRB distributors
in the SRBs and the ET are cross- strapped together. Thus, if
one SRB received an arm or destruct signal, the signal would also
be sent to the other SRB and the ET.
Electrical power from
the RSS battery in each SRB is routed to RSS system A. The recovery
battery in each SRB is used to power RSS system B as well as the
recovery system in the SRB. The SRB RSS is powered down during
the separation sequence, and the SRB recovery system is powered
up. Electrical power for the ET RSS system A and system B is independently
supplied by two RSS batteries on the ET.