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Home , Attitude control, Control moment gyroscope, Destiny (ISS module), Energia (corporation), Extravehicular activity, Flight

The International Station (ISS) systems make up the core functional infrastructure of the on- ISS. The ISS flight systems consist of Habitation; the Crew Health Care System (CHeCS); systems (EVA); the Environmental Control and Life Support System (ECLSS); Computers and Data Management; ; Guidance, , and Control; ; the Thermal Control System (TCS); and the Electrical Power System (EPS). These flight systems provide a safe, livable, and comfortable environment in which crewmembers perform scientific research. Payloads, hardware, software, and crew support items on the ISS operate within the capabilities of these flight systems.

International Guide Systems 49 Integrated Truss Assembly 5 31

10 5 15 31 9 Integrated Truss Assembly 25 6 15 10 32 12 37 37 The truss assemblies provide attachment points for the arrays, thermal control radiators, and 37 external payloads. Truss assemblies also contain electrical and cooling utility lines, as well as the mobile 5 15 transporter rails. The Integrated Truss Structure (ITS) is made up of 11 segments plus a separate com- 24 10 37 ponent called Z1. These segments, which are shown in the figure, will be installed on the Station so that 11 4 5 4 they extend symmetrically from the center of the ISS. 6 32 41 At full assembly, the truss reaches 108.5 meters (356 feet) in length across the extended solar arrays. 22 31 42 30 12 ITS segments are labeled in accordance with their location. P stands for “port,” S stands for “- 22 26 37 37 board,” and Z stands for “Zenith.” 37 38 15 Initially, through Stage 8A, the first truss segment, Zenith 1 (Z1), was attached to the Unity Node 37 37 17 20 zenith berthing mechanism. Then truss segment P6 was mounted on of Z1 and its solar arrays and 29 4 16 4 radiator panels deployed to support the early ISS. Subsequently, S0 was mounted on top of the U.S. 37 36 1 22 27 7 9 Lab Destiny, and the horizontal truss members P1 and S1 were then attached to S0. As the remaining 37 27 30 P6 members of the truss are added, P6 will be removed from its location on Z1 and moved to the outer 2 16 10 31 end of the port side. 8 10 39 P5 11 36 29 27 7 35 39 37 10 P4 39 34 37 7 28 19 3 18 39 23 41 14 13 2003–06 configuration, 10 21 16 looking from nadir. 17 10 P3 5 15 14 1 37 9 37 40 17 39 U.S. Lab 20 5 P1 39 19 Outboard Lower Camera 23 40 18 20 Photovoltaic Radiator 37 3 28 21 Pump Flow Control Assembly 17 33 35 S0 31 10 22 Pump Flow Control Subassembly 10 37 39 21 27 39 7 8 Charged Particle Directional Spectrometer 23 Pump Module 30 9 Direct Current Switching Unit (DCSU) 24 PVR Controller Unit 9 17 19 5 10 DC-to-DC Converter Unit (DDCU) 25 PVR Grapple Fixture Bar 15 5 6 4 S1

1 Solar Array Alpha Rotary Joint 11 Deployed Thermal System Radiator 26 Radiator Beam Valve Module S3 2 Tank Assembly 12 Grapple Fixture 27 Remote Power Control Modules 3 Assembly Contingency 13 Inboard Lower Camera 28 Rotary Joint Motor Controller Baseband Signal Processor 14 Main Bus Switching Units 29 S-Band Antenna 4 Batteries S4 15 Storage Canister 30 Solar Array Alpha Rotary Joint Drive 31 5 Battery Charge Discharge Unit Assembly 12 16 Mobile Transporter Rails 6 Beta Assemblies 31 Solar Array 4 17 Multiplexer/De-Multiplexers 7 Cable Trays 32 Stowed Photovoltaic Radiator 20 18 Nitrogen Tank Assembly (interior to truss) S5 33 6 34 Thermal Control System Radiator Beam 35 Thermal Radiator Rotary Joint with Flex Manual Hose Rotary Coupler S6 Berthing Space to Ground Mechanism Antenna (SGANT) Z1 S0 36 Transponder Z1-to-U.S. Lab 37 Trunnion Umbilical U.S. 38 UHF Antenna Z1-to-U.S. Lab Umbilical 39 Umbilical Mechanism Assemblies 31 20 40 Umbilicals 41 Unpressurized Cargo Carrier Attachment Z1-to-S0 Node 1 U.S. Lab Node 2 42 Wireless Video System Antenna 2003–06 configuration, looking from . S-Band Antenna Umbilical Structural Assembly (SASA) Mounting locations of truss elements view of top/forward/starboard on Node 1 and U.S. Lab, starboard side view International Space Station Guide Systems Habitation 50

Habitation Haircut in SM.

The habitable elements of the International Space Station are mainly a series of cylindrical modules. Many of the primary accommodations, including the waste management and toilet, the galley, individual crew sleep compartments, and some of the exercise facilities, are in the (SM). A third sleep compartment is located in the U.S. Lab, and additional exercise equipment is in the U.S. Lab and the Node. Additional habitation capabilities for a crew of six will be provided prior to completion of ISS assembly. Preparing meal in galley. Playing keyboard in U.S. Lab. Shaving in SM. service module fgb node/airlock u.s. lab

U.S./Joint Airlock

U.S. Lab Computer U.S. Lab Temporary Workstation Sleep Station (TSS) SM mid compartment and treadmill. SM forward compartment. Stowage container in FGB. Node Passageway

Stowed Food Trays in FGB SM Sleep Remote Docking SM Transfer Compartment Control Station Compartment Russian containers. Microgravity Science Glovebox in U.S. Lab

FGB Corridor and Stowage

Stowage in Node 1

Toilet in Waste Management Crewmembers Exercise on U.S. Lab Window SM Treadmill Compartment Crewmembers with Orlan Suits in Pirs International Space Station Guide Systems 51 Crew Health Care System

Crew Health Care System (CHeCS)/ Integrated Medical System

The Crew Health Care System (CHeCS)/Integrated Medical System is a suite of hardware on the ISS that provides the medical and environmental capabilities necessary to ensure the health and safety of crewmembers during long-duration missions. CHeCS is divided into three subsystems:

Leroy Chiao uses RED. Crew uses medical restraint and defibrillator. soyuz service module fgb node/airlock u.s. lab

Volatile Organics Analyzer (VOA) Blood Sample Reflotron

Bonner Ball Neutron Treadmill Vibration CHeCS Rack Particle Detector and Isolation System (TVIS) Water Sampling Phantom Torso for radiation Resistive Exercise and Analysis measurement experiments. Device (RED)

Water Samples (taken for ground Saliva Sample Kit analysis of contamination)

Countermeasures System (CMS)—The CMS provides the equipment and protocols for the perfor- mance of daily and alternative regimens (e.g., exercise) to mitigate the deconditioning effects of living in a microgravity environment. The CMS also monitors crew- CardioCog From left to right: members during exercise regimens, reduces vibrations Intravehicular Charged Particle Directional during the performance of these regimens, and makes Spectrometer (IV-CPDS) periodic fitness evaluations possible. Microbial Surface Sampling Cycle Ergometer with Vibration (gold box) and Tissue Isolation System (CEVIS) Equivalent Proportional Counter (TEPC) detector Environmental Health System (EHS)—The EHS (gold cylinder). monitors the for gaseous contaminants (i.e., from nonmetallic materials off-gassing, prod- ucts, and ), microbial contaminants (i.e., from crewmembers and Station activities), water quality, acoustics, and radiation levels.

Health Maintenance System (HMS)—The HMS provides in-flight life support and resuscitation, medical Potable water Crew Medical Defibrillator. care, and health monitoring capabilities. sampler. Acoustics measurement kit. Atmosphere Grab Restraint System Microbial air sampler. Velo-Ergometer Sampler Container. (CMRS). International Space Station Guide Temp. & Air ISS Systems Humidity U.S. Regenerative Environmental Control and Life Support System (ECLSS) CO2 Environmental ControlECLSS 52 Control Air Re turn Generation Water Recovery Water Recovery CO 2 1 Catalytic Reactor 12 Reactor Health Sensor System (OGS) Rack System Rack 1 (WRS-1) System Rack 2 (WRS-2) Removal 2 Deionizer Beds 13 Storage Tanks H Waste Cabin Air Cabin Return 2 Trace Mgmt. 3 Digital Controller 14 Urine Processor Contaminant Pumps 2 8 14 3 Control 4 Distillation Assembly 15 Waste Products Air Subassembly 15 Volume reserved for 5 Electrolysis Cell Stack later CO Reduction 2 14 12 C O System 17 Urine 2 6 Gas Separator 6 o 11 Environmental Control and n Urine d Recovery 16 Water Processor e 7 Multifiltration Beds 13 n Oxygen s O /N Delivery Pump a Control2 2 1 te Generation 8 Particulate Filter Life Support System (ECLSS) Processed Urine 17 Water Processor 18 N 2 9 Power Supply Pump & Separator 3 3 ater ter 10 Product Water Tank t W Potable Wa 18 Water Processor c uct du Water Prod ro Wastewater Tank P Processing 11 Pumps & Valves 4 9 7 ’s natural life-support system provides the air we breathe, the water we drink, and other 5 r 16 e =Process Water t a Regenerative environmental = Oxygen 10 conditions that support life. For people to live in space, however, these functions must be w te as =Urine W control life support in the U.S. =

performed by artificial means. The ECLSS includes compact and powerful systems that provide segment of the ISS. (vented overboard) =Brine Crew System the crew with a comfortable environment in which to live and work. =Potable Water =Humidity Condensate Potable Water Hand Wash/ System Shaving service module fgb node/airlock u.s. lab shuttle

CWC Bags (used by to carry water from the Shuttle to the ISS)

Vozdukh (absorbs from crew) Elektron (produces oxygen Lithium Hydroxide (LiOH) Contingency Water Container (CWC) bag. from water through elec- cartridge used for eliminating trolysis; vents hydrogen out CO from air, backup system. Cells (make 2 Lithium Hydroxide of the Station) Cartridges (absorb electricity and carbon dioxide) water from oxygen Russian EDVs used to store and and hydrogen) CO2 water. O2

H2O

O2 CO2 Crew breathes in OXYGEN air and generates OXYGEN Crew breathes AIR carbon dioxide Fans and filters circulate air AIR AIR in air and generates and water vapor. and filter out contaminants. carbon dioxide and H2O H2O O2 water vapor. H2O/PERSPIRATION H2O H2O O2 Condensate Water N2 FUEL Delivery of High Processor (condenses N2 CELL Pressure Oxygen and water vapor from air) Air on Progress O2

Freshwater ECLSS on the ISS provides the following functions: O2 Water Delivery Storage Tanks Lab Condensate from Progress Oxygen and Storage Tank (for N2 Nitrogen (Shuttle • Recycle wastewater (including • Maintain total cabin pressure condensate water) urine) to produce drinking replenishes the • Detect and suppress fire gases stored in the N2 (potable) water airlock tanks)

• Maintain cabin temperature and N2 • Store and distribute potable water humidity levels Carbon Dioxide • Use recycled water to produce N2 • Distribute cabin air between ISS Removal Assembly Russian EDVs (used to oxygen for the crew (CDRA, adsorbs store reclaimed water) modules (ventilation) carbon dioxide • Remove carbon dioxide from the from crew) SM gas analyzer. cabin air In the future, a new U.S. Regenerative • Filter the cabin air for particulates Environmental Control and Life Support and microorganisms System will take additional steps toward • Remove volatile organic gases closing the water cycle; it will take from the cabin air humidity condensate from the cabin air and urine from the crew and convert these • Monitor and control cabin air Common Cabin Air Assembly partial pressures of nitrogen, into drinking water, oxygen for breathing, (CCAA, condenses water Solid Fuel Oxygen and hydrogen. vapor from air) Generator (SFOG, burns oxygen, carbon dioxide, , Airflow ventilation fan. candles to produce oxygen, backup system) hydrogen, and water vapor International Space Station Guide Systems 53 Computers and Data Management

Computers and Data Management

Data bus architecture consists of The system for storing and transferring information essential to operating the ISS has been functioning • 100+ MIL-STD-1553B • 190 payload remote at all stages of assembly. From a single module to a large complex of elements from many international data buses, terminals, • 60+ computers into • 600+ international partners, the system provides control of the ISS from either U.S., Russian, Canadian, and soon the which software can be partner and firmware European and Japanese segments of the ISS. loaded as necessary, controller devices, and • 1,200+ remote • 90+ unique types of terminals, remote devices.

SSRMS Control and Workstations soyuz service module fgb node/airlock u.s. lab

Maneuvering Truss Segments into Place at SSRMS Workstation Multiplexer/Demultiplexer (computer) Laptop (in SM crew quarters) Primary Command Crew uses Progress Remote Workstation in SM Control workstation in SM

CO2 O2

H2O

O2 CO2

OXYGEN OXYGEN AIR AIR AIR H2O H2O O2 H2O/PERSPIRATION H2O H2O O2 N2 FUEL N2 CELL

O2

O2

N2 Multiplexer/Demultiplexers N2 (mounted externally on the truss).

N2 Laptop and TVIS Control (located near galley) N2 TORU Remote Progress Multiplexer/Demultiplexer Docking Workstation Memory Unit (MMU) Processor Data Cards in U.S. Lab

Human Research Facility Workstation

Russian Segment Workstations International Space Station Guide Systems Propulsion 54

Propulsion

The ISS Earth at an that ranges from 370 to 460 kilometers (230 to 286 miles) and a speed of 28,000 kilometers per hour (17,500 miles per hour). Owing to atmospheric , the ISS is constantly slowed. Therefore, the ISS must be reboosted periodically in order to maintain its altitude. The ISS progress service module fgb mustnode/airlock sometimes be maneuvered in order to avoid debris in orbit. Furthermore,shuttle the ISS and maneuvering system can be used to assist in

3 rendezvous and dockings with visiting , although that capability is not 7 1 10 usually required. 2 9 Although the ISS typically relies upon large gyrodynes, which utilize 6 4 electrical power, to control its (see “Guidance, Navigation, and 5 1 Progress Cargo Module 8 Control”), when that is beyond the production capability of the gyrodynes 4 Main (2) 7 Correction and Docking Engines (2) 2 Resupply Tanks 5 Attitude Control Engines (32) 8 Docking and Stabilization Engines (24) is required, engines provide propulsion for reorientation. 3 Progress Propulsion System 6 Propellant Tanks (4) 9 Accurate Stabilization Engines (16) Rocket engines are located on the Service Module, as well as on the 10 Propellant Tanks (16) Progress, Soyuz, and spacecraft. 6 10 The Service Module provides 32 13.3-kilograms force (29.3-pounds 5 7 3 2 1 force) attitude control engines. The engines are combined into two groups 8

4 9 of 16 engines each, taking care of pitch, yaw, and roll control. Each Progress provides 24 engines similar to those on the Service Module. When a Progress is docked at the aft Service Module port, these engines can be used for pitch

Progress Rocket Engines Service Module Rocket Engines FGB Rocket Engines and yaw control. When the Progress is docked at the Russian Docking Module, Progress is used for propellant Main Engines: 2,300 kgf (661 lbf), lifetime of 25,000 seconds FGB engines are deactivated once the the Progress engines can be used for roll control. resupply and for performing reboosts. one or both main engines can be fired at a time; they are fed from Service Module is in use. For the latter, Progress is preferred the Service Module’s propellant storage system Correction and Docking Engines: Besides being a resupply , the Progress provides a primary method over the Service Module. Progress uses Attitude Control Engines: 32 multidirectional, 13.3 kgf 2 axis, 417 kgf (919 lbf) four or eight attitude control engines, (29.3 lbf); attitude control engines can accept propellant fed all firing in the direction for reboost. Docking and Stabilization Engines: for reboosting the ISS. Eight 13.3-kilograms force (29.3-pounds force) from the Service Module, the attached Progress, or the FGB 24 multidirectional, 40 kgf (88 lbf) Orbital Correction : 1 axis, 300 propellant tanks Progress engines can be used for reboosting. Engines on the Service Module, kgf (661 lbf) Accurate Stabilization Engines: 16 multidirectional, 1.3 kgf (2.86 lbf) Soyuz vehicles, and Space Shuttle can also be used. The Progress can also be Attitude Control Engines: Service Module Propellant Storage 28 multidirectional, 13.3 kgf (29.3 lbf) used to resupply propellants stored in the FGB that are used in the Service Two pairs of 200-L (52.8-gal) propellant tanks (two nitrogen FGB Propellant Storage tetroxide N2O4 and two unsymmetrical dimethyl [UDMH]) provide a total of 860 kg (1,896 lb) of usable There are two types of propellant Module engines. The ESA ATV and JAXA HTV will also provide propulsion and propellant. The propulsion system rocket engines use the tanks in the Russian propulsion system:

hypergolic of UDMH and N2O4. The Module employs bellows tanks (SM, FGB), both to reboost capability.

a pressurization system using N2 to manage the flow of receive and to deliver propellant, and propellants to the engines. diaphragm tanks (Progress), able only to deliver fuel. Sixteen tanks provide 5,760 kg

(12,698 lb) of N2O4 and UDMH storage: eight long tanks, each holding 400 L (105.6 gal), and eight short tanks, each holding 330 L (87.17 gal). IInternatiional Space Statiion Guiide Systems 55 Extravehicular Activity

Extravehicular Activity (EVA)

To date, there have been more than 69 EVAs (operations outside of the ISS pressurized modules) from the ISS totaling some 400 hours. Approximately 124 spacewalks, totaling over 900 hours, dedicated to assembly and maintenance of the Station will have been accomplished by Assembly Complete. Most of these EVAs have been for assembly tasks, but many were for maintenance, repairs, and science. These tasks were conducted from three different —the Shuttle Airlock, the U.S. Quest Airlock, and the Russian Pirs. Early in the program, an EVA was conducted from the Service Module Transfer Compartment. EVAs are conducted using two different spacesuit designs, the U.S. Extravehicular Mobility Unit () and the Russian Orlan. The operational lessons of the ISS in the areas of EVA suit maintainability, training, and EVA support may prove critical for long-duration crewed missions that venture even further from Earth. International Space Station Guide International Space Station Guide Systems Systems U.S./Joint Airlock 56 57 Extravehicular AMctivityobility Unit

U.S./Joint Airlock (Quest) Extravehicular Mobility NASA/ Unit (EMU) NASA/Hamilton Sundstrand/ILC Dover ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The Quest airlock provides the capability for extravehicular activity (EVA) using ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ the U.S. Extravehicular Mobility Unit (EMU). The airlock consists of two compartments: the Equipment Lock, which provides the systems and volume The EMU provides a crewmember with life support and an enclosure that enables for suit maintenance and refurbishment, and the Crew Lock, which provides the EVA. The unit consists of two major subsystems: the Life Support Subsystem (LSS) actual exit for performing EVAs. The Crew Lock design is and the Assembly (SSA). The EMU provides atmospheric containment, based on the Space Shuttle’s thermal insulation, cooling, solar , and /orbital Crewmember exits Rack the airlock extra- airlock design. debris (MMOD) protection. vehicular hatch. Cabin Air Vent Communications Carrier Equipment Lock TV Camera Cabin Air In-Suit Drink Bag Rack Power Supply Assembly (PSA) Crew Lock Radio Caution and Warning Display and Computer Battery Charging Assembly (BCA) Control Console Battery Stowage Antenna Assembly (BSA)

In-Flight Refill Unit (IRU) Sublimator EVA Extravehicular Mobility Unit Water Tank Hatch (EMU) Water Recharge Bag Luminaire

Don/Doff Contaminant Assembly Oxygen Control Control Cartridge Actuator 1 Primary 2 O Tanks Space Suit 2 Suit Assembly 4 Common Berthing (SSA) Secondary 3 Layers 5 Mechanism and Node O2 System Hatch Connection for 6 Service and Intravehicular Cooling Umbilical 1 Thermal Micrometeoroid Garment (TMG). Cover: Hatch Ortho/KEVLAR® reinforced with GORE-TEX®. Primary Life Support Extravehicular Hatch System (PLSS) 2 TMG Insulation. Five to seven layers of aluminized Nitrogen Tank Mylar® (more layers on arms and legs). Temperature Control Valve 3 TMG liner. Neoprene-coated nylon ripstop. 4 Pressure garment cover. Restraint: Dacron®. Nitrogen Tank Mike Fincke, flight on Expedition Colored 5 Pressure garment bladder. Urethane-coated 9, inside Quest’s Equipment Lock. ID Stripe nylon oxford fabric. Toolbox 2 6 cooling garment. Neoprene tubing.

Toolbox 1 Oxygen Suit’s nominal pressure 0.3 atm (4.3 psi) Tank Liquid Cooling and Ventilation Garment Atmosphere 100% oxygen

Oxygen EVA Hatch Primary oxygen tank 900 psi Tank pressure

Length 5.5 m (18 ft) Secondary oxygen tank 6,000 psi (30-min The Simplified Aid For EVA Rescue (SAFER) provides a pressure backup supply) Width 4.0 m (13.1 ft) compressed nitrogen-powered backpack that permits a crewmember to maneuver independently of the ISS. Its prin- cipal use is that it allows a crewmember to maneuver back to Maximum EVA duration 8 h Mass 9,923 kg (21,877 lb) the Station if he or she becomes detached from the ISS. Airlock in preparation for launch in the Mass of entire EMU 178 kg (393 lb) Launch July 2001, on STS-104, ISS flight 7A. Space Shuttle mission STS-104 berths Quest to Space Station Processing Facility at date The Shuttle berthed to the starboard side of Node 1. the starboard side of Node 1 in July 2001. . Suit life 30 yr International Space Station Guide International Space Station Guide Systems Systems Russian Docking Compartment and Airlock 58 59 Orlan Spacesuit

Russian Docking Orlan Spacesuit Compartment (DC) and Science Production Enterprise Zvezda Airlock ( ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Pirs [Pier]) The Orlan-M spacesuit is designed to protect an EVA crewmember from the ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ S.P. Korolev Rocket and Space Corporation of space, , solar energy, and . The main (RSC Energia) body and helmet of the suit are integrated and are constructed of aluminum alloy. Crewmember in liquid cooling garment prepares View of the zenith end Arms and legs are made of a flexible fabric material. Crewmembers to enter Orlan hatch. of the DC, with probe enter from the rear via the backpack door, which allows Liquid Cooling Garment extended, as it prepares to dock with the ISS in 2001. Pirs provides the capability for extravehicular activity using Russian Orlan suits. rapid entry and exit without assistance. The Orlan-M Pirs also provides contingency capability for ingress for U.S. EMU EVAs. Addition- spacesuit is a “one-size-fits-” suit. Backpack ally, Pirs provides systems for servicing and refurbishing the Orlan suits. The nadir O2 Regulator Docking System on Pirs provides a port for the docking of Soyuz and Progress Communications Cap Reserve O Helmet 2 logistics vehicles. When the final Russian science module arrives, Bottle Docking System Probe Pirs will be moved to the zenith Service Module port. Attitude Control and Wide-Beam Antenna Suit Pressure Water Bag Zenith Docking Gauge System (male) and High-Gain Hatch Entrance to Electrical Wide-Beam Antenna Antenna Service Module Control Panel Lithium Hydroxide Cartridge Stela Manipulator EVA Boom for Moving Hatch 2 Fluid Umbilical Drain Valve High-Gain Crew and Cargo Connector Antenna Backpack CO2 Sensor Filter Attitude Control Closure Antenna Strap Water Filter

Kurs Antenna Cover Over Moisture Collector Refueling Separator Hydraulic EVA Hatch 2 Valves

Primary O2 Bottle

EVA Hatch 1 Movable Handrail Nadir Docking System Position of Crew While Preparing for EVA and Hatch Port for Pneumohydraulic Soyuz or Progress View of the nadir end of the DC. Safety Control Panel Tether Pressure and Deposit Interior Orlan Monitoring Unit Emergency Storage O Hose 2 Radio Apparatus Colored ID Stripe Interior Red—Commander Control Console Blue—Flight Engineer

Electrical Umbilical Battery

Nadir Docking System Refueling and Hatch Port for Hydraulic Valves Soyuz or Progress DC in preparation for launch. DC in preparation for launch.

Length 4.9 m (16 ft) The suit operates at a nominal 0.4 atm (5.8 psi) with a 100% oxygen atmosphere. Maximum diameter 2.55 m (8.4 ft) The suit’s maximum EVA duration is 7 hours. Mass 3,838 kg (8,461 lb) The of the entire Orlan assembly is 238 lb. Volume 13 m3 (459 ft3) Orlan is designed for an on-orbit lifetime of 12 EVAs Interior of Orlan suit with rear or 4 years without return to Earth. Launch date August 14, 2001, on access hatch open. Progress M, ISS mission 4R Inside Pirs, the crew prepares Orlan suits for EVA. Pirs Module location at Service Module nadir. International Space Station Guide International Space Station Guide Systems Systems Communications 60 61 Guidance, Navigation, and Control

GPS antenna on S0 Truss. Communications Guidance, Navigation, and Control (GN&C) The radio and communications network allows ISS crews to talk to the ground control centers and the . It also enables ground control to monitor and Ku band radio in U.S. Lab. maintain ISS systems and operate payloads, and it permits flight controllers to send The International Space Station is a large, free-flying vehicle. The attitude or orienta- commands to those systems. The network routes payload data to the different control tion of the ISS with respect to Earth and the must be controlled; this is important GPS centers around the world. for maintaining thermal, power, and microgravity levels, as well as for communications. Antennas The communications system provides the following: The GN&C system tracks the Sun, communications and navigation , • Two-way audio and video among crewmembers aboard the ISS, and ground stations. Solar arrays, thermal radiators, and communications antennas including crewmembers who participate in an extravehicular activity (EVA); aboard the ISS are pointed using the tracking information. • Two-way audio, video, and file transfer communication between the ISS and The preferred method of attitude control is the use of gyrodynes, Control Moment flight control teams located in the -Houston (MCC-H), (CMGs) mounted on the Z1 Truss segment. CMGs are 98-kilogram other ground control centers, and payload on the ground; (220-pound) wheels that spin at 6,600 revolutions per minute (rpm). The high- and large mass allow a considerable amount of angular • Transmission of system and payload telemetry from the ISS to the MCC-H and to be stored. Each CMG has and can be repositioned to any attitude. As the Payload Operations Center (POC); UHF antenna on the P1 Truss. the CMG is repositioned, the resulting force causes the ISS to move. Using multiple • Distribution of ISS experiment data through the POC to payload scientists; and CMGs permits the ISS to be moved to new positions or permits the attitude to be held • Control of the ISS by flight controllers through commands sent via the MCC-H. constant. The advantages of this system are that it relies on electrical power generated by the solar arrays and that it provides smooth, continuously variable attitude control. Tracking and Data Relay Satellites (TDRS) CMGs are, however, limited in the amount of they can provide (in ) and the rate at which they can move the Station. When CMGs can no longer provide Russian Satellite* the requisite energy, rocket engines are called upon. (in geosynchronous orbit)

S Band Service Module Star Sensor Control Moment Gyroscopes on the Z1 Truss.

U.S. Global Positioning ISS configuration, 2003–2006. Service Module System (GPS) Navigation Ku Band Sun Sensor Signal Timing and Ranging (NAVSTAR) Satellites

Russian Global Navigation Satellite System (GLONASS) Satellites

Service Module Horizon Sensor Control Moment gimbals used for orienting the ISS.

Russian Lira (transmits direct HCMG 2 HCMG 3 to ground) Fringe Pattern UHF Band H EVA Crew- CMG 1 Corner Prism Yuri Onofrienko during communications . members Detector

Mirrors (3) Optical Cavity H H Ham Radio (transmits Output Pulses CMG 1 CMG 3 directly to the ground) Anode (2) HCMG 2 HCMG 4 Laser Counterclockwise Beam Mission Control Center The Rate Gyroscope Discharge HNET (relays communications Assemblies (RGAs) are to remote locations) Space Shuttle the U.S. attitude rate S Band and Ku Band (relayed sensors used to measure the changing orientation of the from the ISS via TDRS satellite) H H ISS. RGAs are installed on the Transducer Cathode Sensor Input NET 1 NET 3 back of the Truss, under the Rate H H GPS antennas, and they are NET 2 NET 4 impossible to see on the ISS Path Length Tammy Jernigan wearing EMU communications * Luch not currently in use. unless shielding is removed. Control Circuit are induced as CMGs are repositioned. carrier (“” ). International Space Station Guide International Space Station Guide Systems Systems Electrical Power System 62 63 Thermal Control System

Electrical Power System Thermal Control System (EPS) (TCS)

The EPS generates, stores, and distributes power and converts and distributes The TCS maintains ISS temperatures within defined limits. The four components Crewmember Mike Fincke replaces the secondary power to users. used in the Passive Thermal Control System (PTCS) are insulation, surface coatings, Remote Power Controller Module (RPCM) heaters, and heat pipes. on the S0 Truss. The Active Thermal Control System (ATCS) is required when the environment

Solar Array Wing (SAW) (has 2 arrays and or the heat loads exceed the capabilities of the PTCS. The ATCS uses a mechanically 32,800 solar cells; converts sunlight to DC pumped fluid in closed-loop circuits to perform three functions: heat collection, heat power, producing a maximum of 31 kW at the beginning of its life and degrading to 26 kW Photovoltaic Radiator (circulates transportation, and heat rejection. after 15 years; each cell is approximately cooling fluid to maintain EPS/ 14% efficient, which was state-of-the-art at Inside the habitable modules, the internal ATCS uses circulating water to trans- battery temperature) the time of design) port heat and cool equipment. Outside the habitable modules, the external ATCS uses circulating ammonia to transport heat and cool equipment.

Nickel-Hydrogen Batteries (store Port and Starboard electrical energy for use during the night; Solar (Array) Alpha Rotation Radiator panels Battery Charge Discharge Unit [BCDU] Joint (SARJ) (tracks the Sun from truss below controls each battery’s charge) throughout Earth orbit) U.S. solar array. Coolant Water Pumps Solar Array

Sunlight Main Bus Switching Units (MBSUs) (route power to proper locations in the ISS) Electrical Energy Electrical Energy

Direct Current (DC) Switching Unit (DCSU) (routes power from the solar array to the MBSUs in the S0 Truss that control power to different ISS locations) Sequential Shunt Unit Primary Electric (SSU) (maintains constant Power (160 V DC) voltage at 160 V, sending Beta Gimbal (used for excess power back to array) tracking the Sun because External Ammonia Coolant Loop External Ammonia Coolant Loop of seasonal changes)

Power Coming in from Arrays MBSUs

Truss Electronics Control Unit Remote Power (ECU) (controls pointing Controllers (RPCs) Heat Exchangers Integrated Equipment of solar arrays) (control the flow Interface Internal Water Powered Assembly (IEA) Truss of electric power Coolant to External Equipment (houses EPS hardware) U.S. Lab to users) Ammonia Coolant (creates heat)

Moderate- DC-to-DC Converter Units Module Temperature (DDCUs)—Some Located on Water Coolant External Ammonia Truss (convert primary Power Going from Loops (17 oC, Coolant Loops (remove 160-V power to secondary MBSUs Through 63 oF) heat through radiator) 124-V power) Umbilicals into U.S. Lab

DDCUs—Some Located in Modules (convert primary 160-V power to secondary 124-V power) Radiator

Russian Triol Fluid Water Coolant Loops Coolant Loop (4 oC, 40 oF)

Starboard radiator panel Crewmember Mike Fincke holds an RPCM in the after deployment. Quest Airlock. It was later used to replace an RPCM on the S0 Truss. Solar Array. Russian Module Coolant Pumps MCC Houston