Gemini Spacecraft Press Reference Book - Comprehensive Information on All Aspects of America's Two-Man Orbiting Spacecraft, Agena Docking Target, Systems
National Aeronautics and Space Administration (NASA), World Spaceflight News
Smashwords Edition
Copyright 2012 Progressive Management
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GEMINI SPACECRAFT STRUCTURAL DESCRIPTION
COMMUNICATION AND TRACKING SYSTEM
ORBIT ATTITUDE AND MANEUVER SYSTEM (OAMS)
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PRESS REFERENCE BOOK
GEMINI SPACECRAFT
NUMBER ELEVEN
Prepared by the External Relations Division McDonnell Aircraft Corporation
Project Gemini, the second phase of the U. S. manned space flight program, was created to provide experience in orbital maneuvers, rendezvous and docking, and long duration space flight, and for manned scientific investigations in space. Under the direction of the Office of Manned Space Flight, NASA Headquarters, Washington, and managed by the NASA Manned Spacecraft Center, Houston, the Gemini program is a national space effort supported by the Department of Defense in such areas as launch vehicle development, launch operations, tracking, and recovery.
The Gemini XI mission is planned as a rendezvous and docking mission with an unmanned Agena target. It will also include extravehicular exercises by the pilot. The Gemini X target is scheduled to be launched about 1.5 hours before the launch of the Gemini Spacecraft. Rendezvous is to be attempted in the first revolution. After docking with the Agena, it is planned to use the primary propulsion system of the Agena to push the combination into a high altitude orbit with an apogee of 865 miles. It is also planned to have the EVA astronaut attach a 100 foot line to the Agena. After his return to the spacecraft, maximum separation will be achieved, establishing a gravity gradient to determine the usefulness of such a technique as a fuel saving procedure when it is desirable to stay in close proximity with another spacecraft for a long period of time. An extensive experiment schedule includes retrieval of a film from an experiment in the Gemini adapter section, and operation of a minimum-reaction power tool. The primary crew consists of Charles Conrad, Jr., command pilot, and Richard F. Gordon, Jr. The back-up crew is Neil A. Armstrong, command pilot, and William A. Anders, Pilot.
GEMINI SPACECRAFT STRUCTURAL DESCRIPTION
The Gemini Spacecraft is a conical structure nearly 19 feet (5.80 meters) high, 10 feet (3.05 meters) in diameter at its base and weighing 8360 pounds (3792 kilograms) at launch.
The spacecraft is designed to endure the aerodynamic pressures, temperature loading, vibration and acoustical noise of launch; the temperature and vacuum of orbital flight; and the extreme heat of reentry, and the impact forces of water landing while providing life support for two astronauts and the necessary equipment for planned missions and experiments.
Gemini's design reflects the knowledge obtained from the development, manufacture and flight operation of the Mercury Spacecraft which, like Gemini, was produced for NASA by McDonnell Aircraft Corporation, St. Louis, Missouri.
Gemini is launched by an Air Force Titan II launch vehicle built by the Martin Company.
The spacecraft consists of two major parts, a reentry module and an adapter module. The reentry module is designed to withstand the extreme heat of reentry. The dark color of the reentry module is characteristic of paints and coatings used to provide heat protection. The white exterior of the adapter module provides for maximum release of the heat brought to the metal surface by the spacecraft coolant lines. Its side walls are protected by heat resistant shingles and the large bulkhead by an ablative heat shield.
The spacecraft is primarily "skin-stringer" construction. Ring stabilized stringers carry nearly all axial loads. Structural materials and construction methods exhibit the influence of Gemini engineers' search for optimum strength-to-weight ratios. Titanium and magnesium are the principal metals used.
REENTRY MODULE
The reentry module (the dark portion of the spacecraft) has three primary sections: rendezvous and recovery (R&R), reentry control system (RCS), and a cabin section. Integral to the reentry module is a heat shield attached to the large end of the module. An aerodynamic fairing covering the horizon sensors at the midpoint of the reentry module is jettisoned midway through the launch phase of the mission.
SPACECRAFT GENERAL NOMENCLATURE
Materials used in the conical section of the reentry module vary greatly because of the effects of reentry heating. Super alloys such as Rene 41 and L-605 are used for the outer skin and skin attachments, which are thermally isolated from the inner structure by Johns-Manville MIN-K, Fiberglas and Thermoflex RF insulation. The basic load-carrying shell is titanium. Aluminum is used inside the cabin where heat is not a structural problem.
RENDEZVOUS AND RECOVERY (R&R) SECTION
The R&R section provides sufficient volume for a rendezvous radar system and a parachute landing system. Structural rings, stringers, and bulkheads are made of titanium. The external surface is covered with beryllium shingles. The nose fairing is reinforced, plastic and Fiberglas-laminate. The R&R section is attached to the RCS section with 24 frangible bolts which are fractured to jettison the R&R section upon deployment of the pilot chute following reentry.
Under the beryllium shingles are Thermoflex RF blankets held in place by a titanium mesh attached to the stringers. The outer surfaces of the rings and stringers are insulated with 0.0015 inch (.038 millimeter) Inconel-foil-encased Min-K in Fiberglas channels.
REENTRY CONTROL SYSTEM (RCS) SECTION
The RCS section houses reentry control system fuel and oxidizer tanks, and thrust chamber assemblies. This section is located between the rendezvous and recovery section and the cabin section. The cylindrical RCS section is an inner skin ring-stringer titanium structure with an outer skin of beryllium shingles. External heat protection is essentially the same as for the rendezvous and recovery section.
CABIN SECTION
The cabin of the Gemini Spacecraft is a truncated cone (a conical enclosure with approximately the top one-third cut away) which houses the Gemini crew, electrical and life support equipment, and various experimental devices. The pressure vessel (crew compartment) provides adequate space for the two-man crew plus instrumentation and life support equipment. Accessible volume with crew aboard is approximately 55 cu. ft. (1.558 cubic meters).
This mechanical latching mechanism on the Gemini hatch permits opening and closing the hatch manually by the astronauts inside the cabin.
The pressure vessel has a fusion-welded titanium frame attached to side panels and fore and aft bulkheads. The side panels and pressure bulkheads are double thickness, thin-sheet titanium (0.010 inch) (.25 millimeter) with the outer sheet beaded for stiffness. A hatch is provided over each astronaut for entering and leaving the spacecraft.
Equipment bays, which contain a variety of electrical and electronic equipment, are located outside the pressure vessel. Unlike the Mercury Spacecraft which had nearly all systems inside the pressure shell, the Gemini Spacecraft has most system components located in unpressurized equipment bays. These components either require no pressurization or are internally pressurized. Since equipment is normally only one layer deep within the compartments, launch crews can remove a hatch, quickly pull out a malfunctioning unit and insert a new one, reinstall the hatch and proceed with the launch.
Experiments for NASA and the U. S. Air Force are installed in bays on the "bottom" of the reentry module, in the adapter section, and in the pressurized crew compartment.
PERSONNEL HATCHES
Two hatches, contoured to the shape of the conical cabin, are located in what is the top of the spacecraft during orbital flight. A hatch is located over each astronaut and is manually operated by handles inside and outside the spacecraft. The latching mechanism is mechanical. The hinge is on the outboard side of the door.
Each hatch incorporates an observation window with three panes of glass with an air space between each pane. The command astronaut's window has two outer panes of 96% silica glass with the innermost pane of temper-toughened aluminosilicate glass. The glass in the co-pilot's window has been especially selected for optical clarity and a 96% silica panel has been substituted for the aluminosilicate panel. Thickness of this panel has been increased from 0.22 to 0.38 inch (5.59 to 9.65 millimeters) to provide strength equal to the aluminosilicate glass.
Manufactured by Corning Glass Company and utilizing a special coating developed by Optical Coating Laboratory, Inc., the panes of the co-pilot's window have optical transmission capability of more than 99%, thus providing the best possible interface between the eye, a camera or other instrument, and space.
To avoid the clouding of the windows which occurred in early Gemini flights, an additional pane of glass is attached over the standard window. After insertion, the astronauts remove the accumulated debris from the exhaust cloud passed through at staging by turning a thumbscrew device alongside each window in the cabin to jettison the spring loaded protective pane.
Hatch closing and final spacecraft launch preparations in the clean room atop the Service Tower shortly before the launch of GT-3.
The protective panes on Gemini XI flew previously as the outer panes of the Gemini VI windows. The protective panes on Gemini XII are reused from the Gemini VII spacecraft.
The surface of each pane, with the exception of the outer one, is coated to reduce reflection and glare and to aid in attenuating ultraviolet radiation.
Skin and beam construction make up the structural design of the personnel access hatches. A silicon rubber seal around each hatch sill and around the two inner panes of glass in the window prevents loss of cabin pressure when the hatches are closed.
A hatch curtain is stowed alongside the hinge of each hatch which, after a water landing, prevents water from entering the cabin when the hatches are opened. In emergency situations the hatches open by a 3-sequence operation actuated by a pyrotechnic (explosive) device. When initiated, these actuators unlock the mechanical latches, open the hatches, and finally supply a hot gas that ignites a seat-ejection catapult/rocket.
HEAT SHIELD
The heat shield is a dish-shaped structure that forms the large end of the reentry module.
The ablative substance of the Gemini heat shield is a paste-like material which hardens in standard atmosphere after being poured into a honeycomb form.
Starting with a load-carrying Fiberglas sandwich structure consisting of two 5-pIy faceplates of resin-impregnated glass cloth separated by a 0.65-inch (16.51 millimeters) thick Fiberglas honeycomb core, an additional Fiberglas honeycomb is bonded to the convex side of the sandwich and filled with Dow-Corning DC-325 organic compound ablative material. The entire shield is encircled with Fiberite ring. The basic ablative substance of the heat shield was developed by McDonnell and is now being marketed by Dow-Corning.
SHINGLES
The surface of the reentry module is covered with overlapping shingles which provide aerodynamic and heat protection and hold in place shaped pads of flexible insulation. The composition of the beaded (corrugated) Rene 41 shingle (0.016 inch, .405 millimeter, thickness) on the sides of the cabin is 53% nickel, 19% chromium, 11% cobalt, 9.75% molybdenum, 3.15% titanium, 1.6% aluminum, .09% carbon, .005% boron, and "less than 2.75%" iron. The shingles are identical in composition and manufacturing technique to those used on Mercury. Extra-large holes in the shingles at the attachment bolts allow each to expand during aerodynamic and solar heating. Oversize washers cover these holes to minimize heat and air flow penetration.