LGM-118A Peacekeeper
The Peacekeeper missile is
America's newest intercontinental ballistic missile. With the end of
the Cold War, the US has begun to revise its strategic policy, and has
agreed to eliminate the multiple re-entry vehicle Peacekeeper ICBMs by
the year 2003 as part of the Strategic Arms Reduction Treaty II. The
Peacekeeper (designated LGM-118A) is a four-stage intercontinental
ballistic missile capable of carrying up to ten independently-targetable
reentry vehicles with greater accuracy than any other ballistic
missile. Its design combines advanced technology in fuels, guidance,
nozzle design, and motor construction with protection against the
hostile nuclear environment associated with land-based systems. The
Peacekeeper is much larger than Minuteman, over 70 feet long and
weighing 198,000 pounds. It is a four stage missile like the Minuteman
III, with the first three stages being solid propellant and the fourth
stage bu hypergolicly fueled with hydrazine and nitrogen tetroxide.
Although capable of carrying eleven Mark 21 RVs, treaty limits
mandated deploying the Peacekeeper with only ten RVs. The entire
missile is encased in a canister in the silo to protect it against
damage and to permit "cold launch". The Minuteman II and III ignite
their first stage engines while in the LF, but the Peacekeeper is
ejected by pressurized gas some fifty feet into the air before first
stage ignition.
The Peacekeeper is a three-stage rocket
ICBM system consisting of three major sections: the boost system, the
post-boost vehicle system and the re-entry system.
The boost system consists of three
rocket stages that launch the missile into space. These rocket stages
are mounted atop one another and fire successively. Three of the four
stages exhausted their solid propellants through a single adjustable
nozzle which guided the missile along its flight path. Motorcases made
of kevlar epoxy material held the solid propellants. The fourth stage
post-boost vehicle employed a liquid bi- propellant rocket propulsion
system to provide velocity and attitude correction for missile
guidance. The post-boost vehicle also employed a self-contained
inertial navigation system that allowed the missile to operate
independent of ground reference or commands during flight.
The 28-foot first-stage solid-fuel
rocket motor weighed approximately 108,000 pounds and is capable of
boosting the missile to about 75,000 feet. The 18-foot long
second-stage motor propelled the missile to an altitude of about
190,000 feet and weighed 60,000 pounds. The rocket motor in the
eight-foot third stage weighed 17,000 pounds and supplied the thrust
to boost the missile to about 700,000 feet. The 2,300 pound post-boost
fourth stage vehicle was designed to maneuver the missile into
position for the multiple reentry vehicles to deploy in their
respective ballistic trajectories.
Following the burnout and separation of
the boost system's third rocket stage, the post-boost vehicle system,
in space, maneuvers the missile as its re-entry vehicles are deployed
in sequence.
The post-boost vehicle system is made
up of a maneuvering rocket, and a guidance and control system. The
vehicle rides atop the boost system, weighs about 3,000 pounds (1,363
kilograms) and is 4 feet (1.21 meters) long.
The top section of the Peacekeeper is
the re-entry system. It consists of the deployment module, up to 10
cone-shaped re-entry vehicles and a protective shroud. The shroud
protects the re-entry vehicles during ascent. It is topped with a nose
cap, containing a rocket motor to separate it from the deployment
module.
The deployment module provides
structural support for the re-entry vehicles and carries the
electronics needed to activate and deploy them. The vehicles are
covered with material to protect them during re-entry through the
atmosphere to their targets and are mechanically attached to the
deployment module. The attachments are unlatched by gas pressure from
an explosive cartridge broken by small, exploding bolts, which free
the re-entry vehicles, allowing them to separate from the deployment
module with minimum disturbance. Each deployed re-entry vehicle
follows a ballistic path to its target.
The Peacekeeper was the first U.S. ICBM
to use cold launch technology. The missile was placed inside a
canister and loaded into the launch facility. When launched,
high-pressure steam ejected the canister from the launch silo to an
altitude of 150 to 300 feet, and once the missile has cleared the
silo, the first stage ignited and sent the missile on its course. This
technique allowed SAC to launch the Peacekeeper from Minuteman silos
despite the fact that the Peacekeeper was three times larger than the
Minuteman III.
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