External Tank Laboratory

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External Tank Laboratory
The External Tank Laboratory as seen from Space Shuttle Liberty on 30 July 2010 during STS-14W.
Station statistics
NSSDC ID:2010-099A
Call sign:Echo
Current: Echo 3 Crew
Launch pad:MPLC LC-1,
Perigee:336 km altitude (220 nmi)
Apogee:346 km altitude (230 nmi)
Orbit inclination:28.45 degrees
Average speed:7,706.6 m/s
(27,743.8 km/h, 17,239.2 mph)
Orbital period:93 minutes
Days in orbit:4774
(5 June)
Days occupied:4488
(5 June)
Number of orbits:74936
(5 June)
Orbital decay:2 km/month
Statistics as of 27 November 2010
(unless noted otherwise)

The External Tank Laboratory (ETL) is a research facility that is being assembled in low Earth orbit by the International Space Agency. On-orbit construction of the station began in 2010 and is scheduled for completion by late 2011. The station is expected to remain in operation until at least 2025, and likely 2030. With a greater cross-sectional area than that of any previous space station, the ETL can be seen from Earth with the naked eye, and is by far the largest artificial satellite that has ever orbited Earth. The ETL serves as a research laboratory that has a microgravity environment in which crews conduct experiments in biology, chemistry, medicine, physiology and physics, as well as astronomical and meteorological observations. The station provides a unique environment for the testing of the spacecraft systems that will be required for future missions to the Moon and outer Solar System.

The ETL project began in 2006, and the first component of the station, the External Tank Workshop, was launched in 2010 aboard an American space shuttle. Assembly continues, as pressurised modules, external trusses, and other components are launched by space shuttles and unmanned launchers. As of November 2010, the station consists of four pressurised modules and an extensive integrated truss structure (ITS). Power is provided by twenty-four solar arrays mounted on the external trusses. The station is maintained at an orbit between 306 km (190 mi) and 467 km (290 mi) altitude, and travels at an average speed of 27,743.8 km/h (17,239.2 mph), completing 15.7 orbits per day.

Operated by the International Space Agency and its member space agencies, the station is primarily controlled by the McGregor Space Center near Magnolia Bend, Louisiana with a backup control center in Geneva, Switzerland. Mission control centers operated by the American National Aeronautics and Space Administration (NASA), the European Space Agency (ESA), the Japan Aerospace Exploration Agency (JAXA) and the Canadian Space Agency (CSA). The cost of the station has been estimated by ESA as €50 billion over 30 years, and, although estimates range from 35-160 billion US dollars, the ETL is believed to be among the most expensive objects ever constructed. The station is serviced by SpaceX Dragon spacecraft, space shuttles and the Automated Transfer Vehicle, and has been visited by astronauts and cosmonauts from 7 different nations.


The External Tank Laboratory (ETL) is an internationally developed satellite currently being assembled in Low Earth Orbit. Primarily a research laboratory, the ETL offers an advantage over spacecraft such as NASA's Space Shuttle because it is a long-term platform in the space environment, where extended studies are conducted. The presence of a permanent crew affords the ability to monitor, replenish, repair, and replace experiments and components of the spacecraft itself. Scientists on Earth have swift access to the crew's data and can modify experiments or launch new ones, benefits generally unavailable on specialised unmanned spacecraft. Following the addition of the Centrifuge Accommodations Module, crews can now expose experiments to varying amounts of gravitation in an environment unavailable to ground based researchers. The ETL also plays host to crews from various international agencies, and is also a destination for space tourists.

The ETL serves as a test platform for orbital construction techniques and for research into the effects of long-term exposure to microgravity on the human body, the understanding of which will be essential for future long duration missions beyond the Earth-Moon system. The use of spent external tanks, and the ability to recycle a large number of consumables comprise some of the techniques learned aboard the station.

Part of the crew's mission is educational outreach and international cooperation. The crew of the ETL provide opportunities for students on Earth by running student-developed experiments, making educational demonstrations, and allowing for student participation in classroom versions of ETL experiments, ISA investigator experiments, and ETL engineering activities.


Interior view of the liquid hydrogen tank found on a Space Shuttle External Tank. Note the two men standing inside for scale.

The External Tank Laboratory was originally conceived as a way to convert spent space shuttle components into cost efficient and readily available spacecraft and space stations. Dubbed by the press as the spiritual successor to both Skylab and Space Station Freedom, the ETL eventually evolved out of the ISA's plans for deep space exploration. Seen as part of a series of stations derived from Shuttle components, the ETL marks the first step by the ISA at building space stations. The project will eventually launch a number of cancelled International Space Station modules and will allow scientists to study the effects of spaceflight on the human body in greater detail and ever before, and will also be able to carry out research into the feasibility of growing large amounts of crops in mircogravity.

Due to budget restrictions, the Russian Federal Space Agency chose not to participate in the construction of the ETL. As such, there was no need for a high inclination orbit such as the one found on the ISS. The ETL's current orbital inclination of 28.5 degrees allows for space shuttles to use less fuel to reach the station, and also allows for larger payloads to be launched into orbit. The orbit also allows for crews flying to the Hubble Space Telescope to dock with the station in an emergency, which has eliminated the need for a rescue mission similar to STS-400.

Station structure


The assembly of the External Tank Station, a major endeavor in space architecture, began in May 2010. Astronauts install each element using spacewalks. By 18 November 2010, they had completed 20, all devoted to assembly and maintenance of the station. 15 of these spacewalks originated from the airlocks of docked Space Shuttles; the remaining 5 were launched from the station.

Pressurized modules

Module Assembly mission Launch date Launch system Nation Isolated View
External Tank Workshop
ECF1 10 May 2010 Space Shuttle Liberty, STS-12W USA STS-129 External Tank Separation.jpg
The initial component of the station, the ET used to launch STS-12W was converted into a wet workshop. The initial launch carried the ET itself, an Aft Cargo Carrier containing outfitting equipment, temporary solar panels and radiators for the station, and stabilization thrusters. The ET's hydrogen tank serves as the crew's main living quarters, and contains the life support equipment and experiment space. The oxygen tank is used as storage space.
ETL Truss Adapter
ECF2 18 June 2010 Delta IV USA
The second pressurized module launched, the ETL Truss Adapter connects to the External Tank Workshop (via PMA-1), and Clarity. The TAM is also the berthing location for the Z1 truss, which forms the backbone of the station's truss system.
(Node 1)
ECF5 26 August 2010 Space Shuttle Liberty, STS-17W USA Harmony Relocation.jpg
The first of the station's node modules, Clarity is the utility hub of the ETL. The module contains four racks that provide electrical power, bus electronic data, and acts as a central connecting point for several other components via its six Common Berthing Mechanisms (CBMs). The Serenity and Legacy nodes, the Cupola, as well as the Rafaello Pressurized Multipurpose Module are permanently berthed to the module. In addition, the module connects to both the ETL Truss Adapter, and the Discovery laboratory.
Cupola ECF5 26 August 2010 Space Shuttle Liberty, STS-17W Europe (Builder)
USA (Operator)
The Cupola is an observatory module that provides ETL crew members with a direct view of docked spacecraft and exterior operations, as well as an observation point for watching the Earth. The module comes equipped with workstations for manual spacecraft docking in an emergency, workstations to control the station's robotic arm and shutters to protect its windows from damage caused by micrometeorites.
ECF6 25 October 2010 Space Shuttle Liberty, STS-20W USA ISS Quest airlock.jpg
The primary airlock for the ETL, Venture hosts spacewalks with both US EMU and Russian Orlan spacesuits. Venture consists of two segments; the equipment lock, that stores spacesuits and equipment, and the crew lock, from which astronauts can exit into space. Exterior storage points also provide locations for storing and refilling up to four MMUs when not in use.
(US Laboratory)
ECF7 5 January 2011 Delta IV USA Destiny as just installed.jpg
The primary research facility for US payloads aboard the ETL, Discovery is intended for general experiments. The module houses 24 International Standard Payload Racks, some of which are used for environmental systems and crew daily living equipment, and features a 20 inch (51 cm) optically perfect window, one of the largest ever produced for use in space.
(Node 2)
ECF8 12 January 2011 Space Shuttle Patriot, STS-22W USA ISS Node 2 module.jpg
The second of the station's node modules, Fidelity is the laboratory hub of the station. The module contains four racks that provide electrical power, and providing berthing locations for several laboratory modules. The American BioLab, British NeuroLab and Borlaug agricultural research lab are permanently berthed to the module, and the module serves as a berthing port for the Italian Multi-Purpose Logistics Modules during shuttle logistics flights.
(Node 3)
ECF9 15 February 2011 Delta IV Heavy Japan (Builder)
USA (Operator)
Kibo PM InOrbit2.jpg
The third of the station's nodes, Serenity contains advanced life support systems to recycle waste water for crew use and generate oxygen for the crew to breathe, designed to supplement those found in the ETW. The node also provides four berthing locations for pressurized modules or crew transportation vehicles, in addition to the permanent berthing location for the Centrifuge Accommodations Module. Serenity is the first 'stretched' node at 40 feet in length to provide clearance for vehicles to safely dock without being blocked by the ETW.
Centrifuge Accommodations Module ECF11 14 March 2011 Space Shuttle Intrepid, STS-24W Japan (Builder)
USA (Operator)
ISS Centrifuge Accommodations Module.jpg
A previously cancelled ISS element, the Centrifuge Accommodations Module (CAM) is designed to expose experiments to varying levels of acceleration, providing various different levels of artificial gravity from between 0.01g and 2g. The CAM is designed to also provide Earth gravity simulation aboard the station, in order to isolate the effects of microgravity on specimens and allow specimens to recover from microgravity exposure. Originally built by JAXA for NASA.
(Pressurized Multipurpose Module)
ECF12 12 April 2011 Space Shuttle Horizon, STS-25W Italy (Builder)
USA (Operator)
STS-114 Raffaello module.jpg
The Raffaello PMM will house spare parts and supplies for the station's laboratory segment. The PMM was created by converting the Italian Raffaello Multi-Purpose Logistics Module into a module that could be permanently attached to the station.
(Hydroponics Laboratory)
ECF13 16 May 2011 Space Shuttle Patriot, STS-26W USA ISS-05 Advanced Astroculture soybean plant growth experiment.jpg
The Borlaug module is designed to be the first operational astrocultural research laboratory. The lab contains a number of racks for research into hydroponics and aeroponics in microgravity, with the eventual goal of growing food for use aboard the station.
(US Physiology Laboratory)
ECF14 7 June 2011 Space Shuttle Liberty, STS-27W USA Sts114-323-001.jpg
Part of the International Space Medicine Laboratory (ISML), BioLab is the core module of the ISML and also serves as the station's alternate medical facility in an emergency. The module is designed to carry out research into the effects of long term exposure to microgravity on the body, with experiments focusing largely on bone and muscle loss, cardiovascular function, and other responses to space adaptation syndrome. The module is also used to carry out research into medical response techniques for use during spaceflight and works in conjunction with NeuroLab to study neurological and vestibular responses brought about by microgravity exposure.
(US Neurology Laboratory)
ECF15 12 July 2011 Space Shuttle Intrepid, STS-164 England (Builder)
USA (Operator)
Part of the International Space Medicine Laboratory (ISML), NeuroLab is designed to carry out research on the effects of long term microgravity exposure on the vestibular and nervous systems.
(Node 4)
ECF16 20 August 2011 Space Shuttle Horizon, STS-165 Japan (Builder)
USA (Operator)
Kibo PM InOrbit.jpg
The fourth of the station's nodes, Legacy is one of the two primary docking locations for visiting capsules, along with Serenity. The node provides four berthing locations for pressurized modules or crew transportation vehicles, in addition to the permanent berthing location for the Venture airlock. Legacy is a 'stretched' node at 40 feet in length to provide clearance for vehicles to safely dock without being blocked by the ETW.
(Node 5)
ECF17 12 September 2011 Space Shuttle Patriot, STS-166 USA Iss Node 3.JPG
The fifth and last of the station's nodes, Integrity serves as an extra node for docking both manned and unmanned vehicles, as well as additional laboratory or logistics modules. American Space Shuttle Orbiters dock with the ETL via PMA-2, attached to Integrity's forward port.

Proposed modules

In addition to the above list, the International Space Agency is also considering the addition of a number of other pressurized components. A list of the modules currently under consideration is below and includes:

  • The Propulsion and Guidance Module would allow for independent orbital control and correction for the station, a task currently carried out by both Space Shuttle orbiters and the initial thrusters attached to the station during outfitting. The module would be designed for orbital refueling either by the crew of the station or automatically by visiting spacecraft. The module, which would be positioned below the Truss Adapter Module, would control a series of thrusters positioned along the station's truss system and at the "top" of the External Tank Workshop.
  • The Commercial Experiment Module, Enterprise, would allow for businesses to rent experiment space aboard the station and allow for those to be performed by visiting commercial astronauts. The module would be divided into several sections, with the initial pressurized lab providing most of the experiment space, an external research platform, and a logistics module for storage space.

Unpressurized elements

Power supply

Life support

Life on board

Sleeping in space

The station provides crew quarters for each member of permanent Expedition crews, with over 24 sleep stations located within the External Tank Workshop. The crew quarters are private soundproof booths in the shape of a wedge approximately 8 feet deep, and varying from 13 feet to 3 feet at the entrances. A crewmember can sleep in them in a tethered sleeping bag, listen to music, use a laptop, and store personal items in a large drawer or in nets attached to the module's walls. The module also provides a reading lamp, a shelf and a desktop. Visiting crews have no allocated sleep module, and attach a sleeping bag to an available space on a wall. It is possible to sleep floating freely through the station, but this is generally avoided because of the possibility of bumping into sensitive equipment. All crew accommodations are well ventilated; otherwise, astronauts can wake up oxygen-deprived and gasping for air, because a bubble of their own exhaled carbon dioxide has formed around their heads.


The ETL features a shower similar in design to the one used aboard Skylab. Located within the External Tank Workshop (ETW), the shower features a floor to ceiling curtain for crew privacy, a flexible shower head and a separate vacuum system used for drawing off water. While crews reported no issues in the shower design, they have noted that drying in space can be a difficult task; as such, most crewmembers prefer to use wet washcloths for daily use. Crews are also provided with rinseless shampoo and edible toothpaste to save water.

There are four space toilets located on the station, with two within the ETW and the others located within Clarity and Fidelity. These Waste and Hygiene Compartments use a fan-driven suction system similar to the Space Shuttle Waste Collection System. Astronauts first fasten themselves to the toilet seat, which is equipped with spring-loaded restraining bars to ensure a good seal. A lever operates a powerful fan and a suction hole slides open: the air stream carries the waste away. Solid waste is collected in individual bags which are stored in an aluminium container. Full containers are transferred to Dragon or ATV spacecraft for disposal. Liquid waste is evacuated by a hose connected to the front of the toilet, with anatomically correct “urine funnel adapters” attached to the tube so both men and women can use the same toilet. Waste is collected and transferred to the Water Recovery System, where it is recycled back into drinking water.

Food and drink

Most of the food eaten by station crews is frozen, refrigerated or canned. Menus are prepared by the astronauts, with the help of a dietitian, before the astronauts' flight to the station. As the sense of taste is reduced in orbit because of fluid shifting to the head, spicy food is a favourite of many crews. Each crewmember has individual food packages and cooks them using the onboard galley, which features two food warmers, a refrigerator, a freezer, and a water dispenser that provides heated, unheated and cold water. Drinks are provided in dehydrated powder form, and are mixed with water before consumption. Drinks and soups are sipped from plastic bags with straws, while solid food is eaten with a knife and fork, which are attached to a tray with magnets to prevent them from floating away. Any food which does float away, including crumbs, must be collected to prevent it from clogging up the station's air filters and other equipment.

Following experiments performed by the crew of STS-10W, several major beverage companies have developed specialized packages to allow crew members to drink sodas such as Coca-Cola and Pepsi. The packages were tested on initial shuttle flights, with the mixture being modified following each mission due to crew requests. The Echo 1 crew reported that the final drink mixtures being flown to the station were markedly improved over the initial trials, however astronaut Derek Ozark stated in an interview with students that "they still haven't gotten it quite right. You get an awful lot of gas with these, so I try not to overdo it."


The most significant adverse effects of long-term weightlessness are muscle atrophy and deterioration of the skeleton, or spaceflight osteopenia. Other significant effects include fluid redistribution, a slowing of the cardiovascular system, decreased production of red blood cells, balance disorders, and a weakening of the immune system. Lesser symptoms include loss of body mass, nasal congestion, sleep disturbance, excess flatulence, and puffiness of the face. These effects begin to reverse quickly upon return to the Earth.

To prevent some of these adverse physiological effects, the station is equipped with two treadmills, an aRED (advanced Resistive Exercise Device) which enables various weightlifting exercises, and a stationary bicycle. Each astronaut spends at least two hours per day exercising on the equipment. Astronauts use bungee cords to strap themselves to the treadmill. Researchers believe that exercise is a good countermeasure for the bone and muscle density loss that occurs when humans live for a long time without gravity, and further research on the effectiveness of various forms of exercise is being performed using the BioLab module.

Station operations

Visiting crews

Each permanent station crew is given a sequential expedition number, preceded by the name "Echo". Expeditions have an average duration of half a year, and they commence following the official handover of the station from one Expedition commander to another. Expeditions currently consists of seven member crews, with future plans calling for between fourteen and twenty-one crew members on the station at one time.

Visiting spacecraft

Spacecraft from a variety of space agencies and private companies visit the station, with each serving a variety of purposes. A fleet of four American Space Shuttles operated by the ISA out of the Kennedy Space Center and serves as the principle assembly platform for the station. Originally, the ISA intended to perform crew rotation and logistics flights mostly with Space Shuttles; however, this was eventually deemed too expensive. As a result, crew rotation missions were originally scheduled to be carried out by Orion capsules, which were deemed more cost effective to operate. While still capable of docking with the station, the ongoing Phoenix Program uses a majority of the capsules for lunar flights. The Automated Transfer Vehicle from the European Space Agency also provides emergency resupply missions to the station in the event other spacecraft are unable to dock for an extended amount of time, however the ESA does not launch scheduled supply flights to the station during normal operations.

Following a successful flight of the SpaceX Dragon on December 8, 2010, the ISA announced that all future crew and cargo missions to the station would take place aboard Dragon spacecraft. Up to five Dragon capsules are expected to dock with the station at once during normal use, providing support for up to 21 crew members.

See also

External links

Official webpages of the participating space agencies
Interactive and multimedia