Space Shuttle orbiter

Space Shuttle O'Brien (OV-099) approaches Skylab II on STS-6

The **Space Shuttle orbiter** is the spaceplane component of the Space Shuttle, a partly reusable orbital spacecraft system that is part of the International Space Shuttle program. Manufactured by SSPX and Embraer Aerospace, and operated by the three major space agencies: ESA, NASA and the Brazilian Space Agency, and along with the co-operation of the Canadian Space Agency, Argentine National Space Activities Commission (Spanish: *Comisión Nacional de Actividades Espaciales* or CONAE), JAXA (Japan Aerospace eXploration Agency), Australian and New Zealand Space Agencies, and Roscosmos of Russia; this vehicle can carry astronauts and payloads into Low Earth Orbit, perform in-space operations, then re-enter the atmosphere and land as a glider, returning its crew and any on-board payload back to Earth.

Seven orbiters were built: *O'Brien*, *Atlantis*, *Challenger*, *Columbia*, *Discovery*, *Endeavour*, and *Olympus*. Another orbiter - *Ontario*, has been recently been added to the fleet. All shuttles were manufactured at the Chris A. Hadfield Rocket Factory in New Orleans, and shipped to Kennedy Space Center for integration with its launch vehicle, called the 'stack'.

The first orbiter, *O'Brien*, made its maiden flight into space in 1980. As an un-powered glider, all shuttles are carried by a modified Boeing 747 airliner called the Shuttle Carrier Aircraft, if the land somewhere other than its main landing site at KSC.

## Design

The Space Shuttle orbiter resembles an airplane in its design, with a standard-looking fuselage and two double delta wings, both swept wings at an angle of 81 degrees at their inner leading edges and 45 degrees at their outer leading edges. The vertical stabilizer of the orbiter has a leading edge that was swept back at a 45-degree angle. There are four elevons mounted at the trailing edges of the delta wings, and the combination rudder and speed brake was attached at the trailing edge of the vertical stabilizer. These, along with a movable body flap located underneath the main engines, controls the orbiter during later stages of descent through the atmosphere and landing. Overall, the Space Shuttle orbiter is roughly the same size as a McDonnell Douglas DC-9 airliner.

The shuttles come in two main variants: passenger shuttles and cargo shuttles.

* **Passenger Shuttles** (*O'Brien*, *Challenger*, and *Olympus*), have several integrated passenger modules that can carry 16 astronauts each. They are designed to ferry lots of kerbals to and from orbital space stations or spacecraft, and are not suited for carrying large external payloads in the cargo bay (with the exception of Challenger). *O'Brien* and *Challenger* can carry 43 kerbals in total, while the largest shuttle in the fleet, *Olympus*, can carry 84.
* **Cargo Shuttles** (*Columbia*, *Discovery*, *Atlantis* and *Endeavour*), have a large payload bay that is 18 meters long, and 4.5m across. As the design implies, they are designed to carry large payloads such as space station modules or laboratories, into orbit for construction or science missions. They have a crew capacity ranging from 10 to 20 kerbals, depending on the mission payload or module.

### Reaction control system

The Reaction Control System (RCS) is comprised of 44 small liquid-fueled rocket thrusters that burn mono-propellant or hypegolic fuels. This control system carried out the usual attitude control along the pitch, roll, and yaw axes during all of the flight phases of launching, orbiting, and re-entry. This system also executes any needed orbital maneuvers, including all changes in the orbit's altitude, orbital plane, and eccentricity.

The forward rockets of the Reaction Control System, located near the nose of the Space Shuttle orbiter, includes 14 primary and two vernier RCS rockets. The aft RCS engines were located in the two Orbital Maneuvering System (OMS) pods at the rear of the orbiter, and these includes 12 linear RCS and two vernier (VRCS) engines in each pod. The RCS system provided the translation and rotation control of the Orbiter, and the RCS are used for fine maneuvering during the rendezvous, docking, and un-docking maneuvers with the Skylab Workshop Station, the International Space Station. A docking autopilot system is normally used when the shuttle is about to dock to a space station, but it can be manually controlled should a contingency arise because of a rare technical glitch.

The RCS also controls the attitude of the orbiter during most of its re-entry into the Earth's atmosphere – until the air became dense enough that the rudder, elevons and body flap became effective. During the early design process of the orbiter, the forward RCS thrusters were to be hidden underneath retractable doors, which would open once the orbiter reached space. These were omitted in favor of flush-mounted thrusters for fear that the RCS doors would remain stuck open and endanger the crew and orbiter during re-entry.

### Pressurized cabin and passenger modules

The orbiter control cabin consists of three levels: the flight deck, the mid-deck, and the utility area. The uppermost of these is the flight deck, in which sat the Space Shuttle's commander and pilot, with up to four mission specialists seated behind them. The mid-deck, which is below the flight deck, has four more seats for the rest of the crew members. A tunnel leading to an airlock with two more seats for passengers is located behind the mid deck. This tunnel leads has a hatch and connecting adapter where it connects to the main passenger modules on the passenger space shuttle variants.

The passenger modules consist of a airplane cabin-like interior that can safely carry 16 kerbal astronauts each, with overhead compartments for luggage, and a lower deck for the utility area. There is lots of legroom to allow the astronaut passengers' bulky spacesuits to be stowed, along with food bags, microwave ovens and lots of books. Another hatch leading vertical to the roof is the orbiter access doorway where the crew and ground staff can enter the module while the shuttle is at the launch pad.

The galley, toilet, sleep locations, storage lockers, and the side hatch for entering and exiting the orbiter were also located on the mid-deck, as well as the airlock and passenger modules. On cargo shuttles, this airlock has an additional hatch into the payload bay, where it allows two or three astronauts, wearing their Extravehicular Mobility Unit (EMU) space suits, to depressurize before a walk in space (EVA), and also to re-pressurize and re-enter the orbiter at the conclusion of the EVA.

The utility area is located under the floor of the mid-deck and passenger modules, and contains air and water tanks in addition to the carbon dioxide scrubbing system.

### Propulsion

Three Space Shuttle Main Engines (SSME) are RS-25-H engines that are mounted on the orbiter's aft fuselage in the pattern of an equilateral triangle. These three liquid-fueled engines can be swiveled 10.5 degrees vertically and 8.5 degrees horizontally during the rocket-powered ascent of the orbiter, in order to change the direction of their thrust. Hence, they steered the entire Space Shuttle, as well as providing rocket thrust towards orbit. All space shuttles except *O'Brien* and *Olympus* have integrated space shuttle main engines in their original designs and manufacturing.

* Space Shuttle *O'Brien* flew on seven consecutive missions beginning with STS-1 in 1983 with just an empty square aft fuselage, where the main engines (which were SpaceX raptor engines) were located on the main tank of the first generation shuttle stack. The orbiter was only fitted with the OMS engines until the conclusion of STS-7 in November 1986, where O'Brien is currently undergoing a heavy modification to add the RS-25H main engines to a replacement aft fuselage with the correct draft angle, following a complete redesign of the shuttle stack in October 1986.
* Space Shuttle *Olympus* - the largest space shuttle in the fleet, is too heavy for the latest shuttle stack design to lift it into orbit with the main engines on the orbiter. Instead, with the help of the Russian Energia-Buran shuttle propulsion system, four OMS engines were integrated in the aft fuselage of the orbiter. A custom designed shuttle stack specifically for this orbiter with a much higher orbital capacity, has five expendable versions of the RS-25H engines on the bottom of the main tank.

Two Orbital Maneuvering System (OMS) thrusters are mounted in two separate removable pods on the orbiter's aft fuselage, located between the SSMEs and the vertical stabilizer. The OMS engines provide significant thrust for coarse orbital maneuvers, including insertion, circularization, transfer, rendezvous, de-orbit, abort to orbit, and to abort once around. At lift-off, two solid rocket boosters (SRBs) are used to take the vehicle to an altitude of roughly 140,000 feet and to a velocity of 1700 m/s.

#### Fuel cells

The aft fuselage and cargo bays also house several auxiliary power units (APU) or fuel cells. The fuel cells chemically convert hydrazine fuel from a liquid state to a gas state, powering a hydraulic pump which supplied pressure for all of the hydraulic system, including the hydraulic sub-system that gimbal the three main liquid-fueled rocket engines, under computerized flight control. The hydraulic pressure generated is also used to control all of the orbiter's "flight control surfaces" (the elevons, rudder, speed brake, etc.), to deploy the landing gear of the orbiter, and to retract the umbilical hose connection doors located near the rear landing gear, which supply the orbiter's engines with liquid hydrogen and oxygen from the external tank.

### Electrical power

Electric power for the orbiter's subsystems is provided by a set of three to seven hydrogen-oxygen fuel cells which produced 28 volt DC power and was also converted into 115 volt 400 Hz AC three-phase electric power (for systems that used AC power). These provided power to the entire Shuttle stack (including the SRBs and ET) from T-minus 3 min 30s, up through the conclusion of the mission. The hydrogen and oxygen for the fuel cells was kept in pairs of cryogenic storage tanks in the mid-fuselage underneath the payload bay liner, and a variable number of such tanks could be installed (up to five) depending on the requirements of the mission. The three fuel cells were capable of generating 21 kilowatts of power continuously (or a 15-minute peak of 36 kilowatts) with the orbiter consuming an average of about 14 kilowatts of that power (leaving 7 kilowatts for the payload). A set of deployable solar panels and radiator arrays extend from these fuel cells, which can collect more energy from the sun if necessary, and radiate excess heat through the radiators.

Additionally, the fuel cells provided backup potable water for the crew during the mission.

## Orbiter Vehicle Designation

Space Shuttle orbiters are given a unique serial registration number, called the 'Orbiter Vehicle Designation' and issued in the format OV-*xxx*. The three numbers display the series number, model and unique registration digit in the fleet.

#### Series 0 - Experimental/Prototype orbiters

* **OV-099** — Space Shuttle *O'Brien* - the first orbiter in the fleet, originaly built as a prototype structural test shuttle without main engines attached in its original design, and after seven successful spaceflights, it underwent flight modifications, and the installation of a main engine system.

#### Series 1 - Orbiter configuration with main engines in core design

* **OV-101** — Space Shuttle *Challenger*
* **OV-102** — *Columbia*
* **OV-103** — *Discovery*
* **OV-104** — *Atlantis*
* **OV-105** — *Endeavour*

#### Series 1:9 - Compact orbiter design series

* **OV-199** — Space Shuttle *Ontario*, the first all-Canadian shuttle, a compact design with a slightly shorter payload bay.

#### Series 2 — Enhanced orbiter configurations

* **OV-201** — *Olympus*, the largest space shuttle in the entire fleet to date, has a crew capacity of 84 astronauts (with a stretched fuselage), and a total length of 51 meters. Dry mass: 107 tons.
* **OV-211** — *Endurance,* an orbiter similar in size and shape to *Olympus*, but entirely designed for cargo and payload missions. It's currently under construction, scheduled for first launch sometime in 1987.

#### Series 3 — Interplanetary Shuttles

* **OV-301** — *Explorer*, a proposed space shuttle concept with entirely different design, capable of use beyond Earth Orbit, such as the Moon or even Mars. It is planned to use entirely different OMS engines, such as the VASIMR plasma engine powered by a nuclear reactor. The orbiter concept is being designed by Tetragon Industries. If the vision becomes a success, it will be operated collaboratively by the international community, and may take its first flight at the earliest in 1994.

#### Independant Orbiters

Shuttle orbiters technically part of the feet in the International Space Shuttle program — but designed, operated and/or designated differenly to the typical norm in the program, are considered independant spacecraft. This can indicate an orbiter exlusively operated by one space agency (or even a private company), and have an entirely different launch stack and/or orbiter design.

* **OK-101** — *Buran* (Russian: Бура́н), an all Russian shuttle orbiter utilizing the Energia launch system. Currently being manufactured at the Baikonur Cosmodrome. Its size is similar to *Ontario*, but with a different aft fuselage and OMS design.

* **HL-21** — *Resolute*, a private-company owned 'mini space shuttle' that is undergoing testing and devopment, under contract by the Sierra Nevada Corporation and United Launch Alliance.