The airlock is sized to accommodate two fully suited flight crew
members simultaneously. Support functions include airlock depressurization
and repressurization, extravehicular activity equipment recharge,
liquid-cooled garment water cooling, EVA equipment checkout, donning
and communications. The EVA gear, checkout panel and recharge stations
are located on the internal walls of the airlock.
The airlock hatches are mounted on the airlock. The inner hatch
is mounted on the exterior of the airlock (orbiter crew cabin middeck
side) and opens into the middeck. The inner hatch isolates the airlock
from the orbiter crew cabin. The outer hatch is mounted inside the
airlock and opens into the airlock. The outer hatch isolates the
airlock from the unpressurized payload bay when closed and permits
the EVA crew members to exit from the airlock to the payload bay
Airlock repressurization is controllable from the orbiter crew
cabin middeck and from inside the airlock. It is performed by equalizing
the airlock's and cabin's pressure with equalization valves mounted
on the inner hatch. The airlock is depressurized from inside the
airlock by venting the airlock's pressure overboard. The two D-shaped
airlock hatches open toward the primary pressure source, the orbiter
crew cabin, to achieve pressure-assist sealing when closed.
Each hatch has six interconnected latches and a gearbox/actuator,
a window, a hinge mechanism and hold-open device, a differential
pressure gauge on each side and two equalization valves.
The 4-inch diameter window in each airlock hatch is used for crew
observation from the cabin/airlock and the airlock/payload bay.
The dual window panes are made of polycarbonate plastic and mounted
directly to the hatch by means of bolts fastened through the panes.
Each hatch window has dual pressure seals, with seal grooves located
in the hatch.
Each airlock hatch has dual pressure seals to maintain pressure
integrity. One seal is mounted on the airlock hatch and the other
on the airlock structure. A leak check quick disconnect is installed
between the hatch and the airlock pressure seals to verify hatch
pressure integrity before flight.
The gearbox with latch mechanisms on each hatch allows the flight
crew to open and close the hatch during transfers and EVA operations.
The gearbox and the latches are mounted on the low-pressure side
of each hatch; with a gearbox handle installed on both sides to
permit operation from either side of the hatch.
Three of the six latches on each hatch are double-acting and have
cam surfaces that force the sealing surfaces apart when the latches
are opened, thereby acting as crew assist devices. The latches are
interconnected with push-pull rods and an idler bell crank that
is installed between the rods for pivoting the rods. Self-aligning
dual rotating bearings are used on the rods for attachment to the
bellcranks and the latches. The gearbox and hatch open support struts
are also connected to the latching system by the same rod/bellcrank
and bearing system. To latch or unlatch the hatch, the gearbox handle
must be rotated 440 degrees.
The hatch actuator/gearbox is used to provide the mechanical advantage
to open and close the latches. The hatch actuator lock lever requires
a force of 8 to 10 pounds through an angle of 180 deg rees to unlatch
the actuator. A minimum rotation of 440 deg rees with a maximum
force of 30 pounds applied to the actuator handle is required to
operate the latches to their fully unlatched positions.
The hinge mechanism for each hatch permits a minimum opening sweep
into the airlock or the crew cabin middeck. The inner hatch (airlock
to crew cabin) is pulled or pushed forward to the crew cabin approximately
6 inches. The hatch pivots up and to the right side. Positive locks
are provided to hold the hatch in both an intermediate and a full-open
position. A spring-loaded handle on the latch hold-open bracket
releases the lock. Friction is also provided in the linkage to prevent
the hatch from moving if released during any part of the swing.
The outer hatch (airlock to payload bay) opens and closes to the
contour of the airlock wall. The hatch is hinged to be pulled first
into the airlock and then forward at the bottom and rotated down
until it rests with the low-pressure (outer) side facing the airlock
ceiling (middeck floor). The linkage mechanism guides the hatch
from the closed/open, open/closed position with friction restraint
throughout the stroke. The hatch has a hold-open hook that snaps
into place over a flange when the hatch is fully open. The hook
is released by depressing the spring-loaded hook handle and pushing
the hatch toward the closed position. To support and protect the
hatch against the airlock ceiling, the hatch incorporates two deployable
struts. The struts are connected to the hatch linkage mechanism
and are deployed when the hatch linkage is rotated open. When the
hatch latches are rotated closed, the struts are retracted against
The airlock hatches can be removed in flight from the hinge mechanism
using pip pins, if required.
The airlock air circulation system provides conditioned air to
the airlock during non-EVA periods. The airlock revitalization system
duct is attached to the outside airlock wall at launch. Upon airlock
hatch opening in flight, the duct is rotated by the flight crew
through the cabin/airlock hatch, installed in the airlock and held
in place by a strap holder. The duct has a removable air diffuser
cap, installed on the end of the flexible duct, which can adjust
the air flow from 216 pounds per hour. The duct must be rotated
out of the airlock before the cabin/airlock hatch is closed for
airlock depressurization. During the EVA preparation period, the
duct is rotated out of the airlock and can be used for supplemental
air circulation in the middeck.
To assist the crew member before and after EVA operations, the
airlock incorporates handrails and foot restraints. Handrails are
located alongside the avionics and ECLSS panels. Aluminum alloy
handholds mounted on each side of the hatches have oval configurations
0.75 by 1.32 inches and are painted yellow. They are bonded to the
airlock walls with an epoxyphenolic adhesive. Each handrail has
a clearance of 2.25 inches between the airlock wall and the handrail
to allow the astronauts to grip it while wearing a pressurized glove.
Foot restraints are installed on the airlock floor nearer the payload
bay side. The ceiling handhold is installed nearer the cabin side
of the airlock. The foot restraints can be rotated 360 degrees by
releasing a spring-loaded latch and lock in every 90 degrees. A
rotation release knob on the foot restraint is designed for shirt-sleeve
operation and, therefore, must be positioned before the suit is
donned. The foot restraint is bolted to the floor and cannot be
removed in flight. It is sized for the EMU boot. The crew member
first inserts his foot under the toe bar and then rotates his heel
from inboard to outboard until the heel of the boot is captured.
There are four floodlights in the airlock.
If the airlock is relocated to the payload bay from the middeck,
it will function in the same manner as in the middeck. Insulation
is installed on the airlock's exterior for protection from the extreme
temperatures of space.
For Spacelab pressurized module missions, the airlock remains in
the crew compartment middeck, and a tunnel adapter that mates with
the airlock and the Spacelab tunnel is installed in the payload
The airlock tunnel adapter, hatches, tunnel extension and tunnel
permit the flight crew members to transfer from the spacecraft's
pressurized middeck crew compartment to Spacelab's pressurized shirt-sleeve
In addition, the airlock, tunnel adapter and hatches permit the
EVA flight crew members to transfer from the airlock/tunnel adapter
in the space suit assembly into the payload bay without depressurizing
the crew cabin and Spacelab.
The Spacelab tunnel and Spacelab are accessed via the tunnel adapter,
which is located in the payload bay and is attached to the airlock
at orbiter station Xo 576 and the tunnel extension at Xo660.
The tunnel adapter has an inside diameter of 63 inches at its widest
section and tapers in the cone area at each end to two 40-inch-
diameter D-shaped openings 36 inches across. A 40-inch- diameter
D-shaped opening 36 inches across is located at the top of the tunnel
adapter. Two pressure-sealing hatches are located in the tunnel
adapter, one in the upper area of the tunnel adapter and one in
the aft end of the tunnel adapter. The tunnel adapter is a welded
structure constructed of 2219 aluminum with 2.4- by 2.4-inch exposed
structural ribs on the exterior surface and external waffle skin
The hatch located on the middeck side of the airlock is mounted
on the exterior of the airlock and opens into the middeck. The hatch
isolates the airlock from the crew cabin. The hatch located in the
tunnel adapter's aft end isolates the tunnel adapter/airlock from
the tunnel extension, tunnel and Spacelab. This hatch opens into
the tunnel adapter. The hatch located in the tunnel adapter at the
upper D-shaped opening isolates the airlock/tunnel adapter from
the unpressurized payload bay when closed and permits the EVA crew
members to exit from the airlock/tunnel adapter to the payload bay
when open. This hatch opens into the tunnel adapter.
The hinge mechanism for each hatch permits a minimum opening sweep
into the tunnel adapter or the spacecraft crew cabin middeck. The
airlock crew cabin hatch in the middeck is pulled/pushed forward
to the middeck approximately 6 inches. The hatch pivots up and right.
Positive locks are provided to hold the latch in both an intermediate
and a full-open position. A spring-loaded handle on the latch hold-open
bracket releases the lock. Friction is provided in the linkage to
prevent the hatch from moving if released during any part of the
The aft hatch is hinged to be pulled first into the tunnel adapter
and then forward at the bottom. The top of the hatch is rotated
towards the tunnel and downward until the hatch rests with the Spacelab
side facing the tunnel adapter floor. The linkage mechanism guides
the hatch from the closed/open, open/closed position with friction
restraint throughout the stroke. The hatch is held in the open position
by straps and Velcro.
The upper (EVA) hatch in the tunnel adapter opens and closes to
the left wall of the tunnel adapter. The hatch is hinged to be pulled
first into the tunnel adapter and then forward at the hinge area
and rotated down until it rests against the port wall of the tunnel
adapter. The linkage mechanism guides the hatch from the closed/open,
open/closed position with friction restraint throughout the stroke.
The hatch is held in the open position by straps and Velcro.
The hatches can be removed in flight from the hinge mechanisms
via pip pins, if required.
The crew compartment, bunk sleep stations (if installed), airlock
and modular stowage lockers are built by Rockwell's Space Transportation
Systems Division, Downey, Calif. The original crew seat contractor
was AMI of Colorado Springs, Colo., but later Rockwell's Space Transportation
Systems Division. The Spacelab pressurized module tunnel adapter
and tunnel contractor is McDonnell Douglas Astronautics, Huntington