Space Shuttle Orbiter

USA

THE SHUTTLE ORBITER FLEET

OV-101: Enterprise, test vehicle (now owned by Smithsonian Institution).
OV-102: (1981) Columbia, first operational shuttle.
OV-099: (1983) Challenger, destroyed in explosion Jan-1986.
OV-103: (1984) Discovery.
OV-104: (1985) Atlantis.
OV-105: (1992) Endeavour, replacement for OV-099.

The Space Shuttle Orbiter is a wide-body, delta-winged airplane and space vehicle. It is constructed primarily out of aluminum and covered with reusable surface insulation. The Orbiter is propelled by 49 rocket engines employed in various combinations for liftoff, attitude control in space, and for initiating reentry. Electrical power for Orbiter systems is provided by fuel cells which produce, as a byproduct, water for drinking.

The Space Shuttle Orbiter is designed to deploy and/or retrieve payloads utilising the 18.3 x 4.57 m cargo bay, permiting in flight servicing or Earth return. An array of standard payload platforms, including the European Spacelab or commercial Spacehab modules, can be carried into space and returned to the Earth at the completion of a mission. A highly articulated mechanical arm called the Remote Manipulator System (RMS), can be operated by Shuttle astronauts while inside the Orbiter cabin. The RMS is used to extract payloads from the cargo bay and deploy them outside of the Orbiter.

The forward section of the Orbiter contains the flight deck and crew quarters for the astronauts. During launch up to four astronauts may sit on the upper flight deck and up to four more on the middle crew quarters deck. The forward portion of the flight deck resembles the cockpit of a jet airliner but features separate controls for flying in space and flying in the atmosphere. The aft portion of the flight deck contains four stand-up duty stations including the controls for the RMS. The crew quarters deck is entered through an open hatch in the flight deck floor. The crew quarters contain eating, sleeping, and sanitary facilities. Located at the aft end of the crew quarters deck is an air lock through which astronauts may enter the cargo bay when extravehicular activities are necessary.

SPACE SHUTTLE ORBITER SPECIFICATIONS

First launch: 12-Apr-1981
Number launches: 112 to end-2002
Principal uses: US manned capability to beyond 2010 (four reuseable Orbiter fleet), 25,000 kg payload delivery to LEO, satellite retrieval/in situ repair, short-duration science platform, Space Station assembly/servicing
Availablity: typically 7-8 flights/year manifested but with restricted commercial access
Cost: NASA's figures for the first 20 missions (1981-85) showed an average cost of $257 million. STS-27 military mission cost to NASA in Dec-1988 was reported at $375 million. Constuction cost is about $1.3-2 billion per orbiter (each capable of >100 missions)
Performance: OV-103/104/105 can deliver 24,990 kg into 204 km LEO; they are called 55K Orbiters because of their 55,100-pound capacities (the design goal was 65K). OV-102 can only handle 21,140 kg because of its greater dry mass
Crew size: 2 min, 8 max
Endurance: originally 9-10 days; OV-102/104 were modified as 16-day Extended Duration Orbiters (EDO); OV-105 was constructed with EDO capacity. OV-104/105 are capable of carrying EDO kits allowing up to 28-day missions, although none is yet planned
Wingspan: 23.79 m
Length: 37.24 m
Height: 17.27 m
Habitable volume: 71.5 m³
Dry mass: 82,288 kg OV-102, 78,448 kg OV-103, 78,687 kg OV-104, 79,135 kg OV-105
Landing mass: 104,328 kg max, defined by abort requirements
Main engines
    engines: three Rocketdyne SSME fed by external tank
    propellant: LOX/liquid hydrogen
    thrust: 1,668 kN Sl, 2,090 kN vac
    specific impulse: 363 s SL, 455 s vac
    burn time: typically 520 s
Orbital maneuvering system
    engines: single Aerojet x two pods
    propellant: NTO/MMH
    propellant mass: 21,660 kg total in two pods
    thrust: each 26.7 kN vac
    specific impulse: 313 s vac
    burn time: 1,250 s total
    delta v: 700 m/s
Reaction control system
    thrusters: 38 x 3870 N + 6 x 106 N
    propellant: NTO/MMH
    propellant mass: about 3,300 kg
    specific impulse: 289 s vac
    total impulse: 9,355 kNs
Crew module: the pressurized crew module is an independent 71.5 m³ vessel of welded aluminum suspended within the forward fuselage. The largest of ~300 penetrations are the two hatches and 10 windows. The crew module is divided into three principal areas. The flight deck (upper) provides side-by-side seating for two pilots with dual controls, two stowable seats for Mission Specialists and controls for all on-orbit operations. On the middle deck, provisions are made for four more seats, bunks, galley, airlock, toilet and three electronics bays. The lower deck contains environmental control systems and storage facilities.
Air lock: the mid-deck houses the 4.26 m², 1.6 m inner diameter, 2.1 m long airlock. The airlock is sized to accommodate two fully suited astronauts (three suits are carried on most EVA designated missions). Pressurization can be controlled from inside the airlock or mid-deck. The suits are mounted on the walls, where they are checked out/recharged. Two 102 cm D-shaped hatches open forward and down against the main pressure
Remote manipulator: a 408 kg, 15.3 m long, 38 cm diameter graphite/epoxy Remote Manipulator System (RMS) arm is installed along the port sill for deployment/recovery of up to 29,500 kg payloads, providing a work platform and for vehicle inspection
Thermal protection: the reusable thermal protection system (TPS) is applied externally to maintain the airframe outer skins <175^oC during reentry when temperatures on the nose and wing leading edges can reach 1,650^oC. Some 25-50 tiles are now replaced after each mission. The 27,500 tiles/blankets are designed for 100 missions although totals and types vary slightly between Orbiters
Environmental/life support: cabin air is supplied through two independent loops from the fuel cells' cryogenic oxygen tanks and four 23 kg supplies of nitrogen in the forward bay. The cabin mixture is held at 21% O₂/79% N₂ normal atmospheric pressure but reduction to 0.69 atm is effected prior to EVAs. Most of the mid-deck sub-floor is devoted to environmental control. Two main 11,000 rpm fans circulate air in five major loops. In the older system, air is drawn through two replacable LiOH/charcoal canisters to hold CO₂ content <1% and remove odors. A 147 kg Regenerative CO₂ Removal System is carried by the EDOs. Air is cooled after flowing through the filters by four heat exchangers. These are part of two parallel water coolant loops. The warmed water is pumped to a cargo bay Freon-21 heat exchanger as part of the main thermal control system. Two parallel Freon loops pumping 1,220 kg/h reject their heat through four pairs of radiator panels, 3 m x 4.6 m, exposed on the inner payload doors. The Orbiter's three independent 27-32 V electrical buses are supplied by three 92 kg, 7 kW fuel cells on the forward cargo bay floor. Reactants are drawn from up to five pairs of cryogenic tanks: 354 kg oxygen and 42 kg hydrogen from each pair. The 11 kg/h of water byproduct is diverted into the cabin tanks for drinking or cooling purposes. For 16-day EDO missions a cryogenic pallet is carried in the aft cargo bay. The 2,926 kg pallet plumbs four tank sets to the current five. It could carry a further four sets for 28-day missions
Auxiliary power units: hydraulic power used to be generated by three 39 kg, 103 kW APUs in the aft fuselage, each drawing on 134 kg of hydrazine. Improved APUs were introduced on OV-105 and retrofitted to the others. They are activated 5 min before launch and the OMS deorbit burn to provide hydraulic control of the Orbiter's aerodynamic surfaces, main engine gimballing, undercarriage deployment and braking power
Avionics/control: fully fail-operational/fail-safe guidance, navigation and control system, incorporating Honeywell 4-channel fly-by-wire electrical flight control system for operation of all control surfaces and engines. Central data processing is by five IBM Advanced System/4 Pi Model AP-101 General Purpose Computers (GPC) and two 34 Mbit mass memory tape recorders. Telemetry is provided at 51.2 kbit/s to the ground control system. The 1972-designed GPCs are being replaced with AP-101S models. The three Singer-Kearfott KT-70 IMUs are being replaced by Kearfott's HAINS. GN&C is supported by two orthogonal Ball star trackers, three Northrup rate gyro assemblies, three Bendix accelerometer assemblies, three Hoffman L-band ARN-84 TACAN, Eaton Corp AIL Div triplex Ku-band Microwave Scan Bean Landing System and two Honeywell C-band radar altimeters. It is hoped eventually to replace both TACAN and MSBLS with GPS. Communications and tracking equipment includes two Ku-band rendezvous radar/TDRS satellite comms antenna, two P-band UHF for EVA/ATC, Conrac S-band FM for Orbiter/ground and payload comms, Ku-band radio for orbiter/ground comms and Ku-band for rendezvous
Landing gear: retractable tricycle type, nose 81 cm diameter, main 113 cm diameter, twin wheels/brakes with pneumatic shock absorbers. Deployed hydraulically in about 5 s some 15 s before touchdown, with pyrotechnic backup. Rated max landing speed 415 km/h. A manually deployed 12.2 m diameter drag 'chute on a 26 m line is now incorporated at the tail base to shorten rollout by 760 m and cut nosewheel contact speed by 37 km/h to 260 km/h, reducing tire/brake wear. It also improves handling characteristics, particularly in crosswinds and on wet runways

Ref.: #37

Home