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ISS Final Stage
ISS Final Stage - The International Space Station in as planned at completion. From top to bottom, Soyuz rescue craft, Russian Service Module, Functional Cargo Block, NASA docking module, US Habitat Module, truss, US Lab Module, European Columbus and Japanese JEM modules, docked US space shuttle. The inside panels on the trusses are thermal control system radiators; four sets of blue solar panels are at the end of each truss. The station will orbit at an altitude of up to 370 kilometres at an inclination of 51.6 degrees. The solar panels will generate 110 kilowatts of power, with 46 kilowatts available for science experiments. Total station pressurised volume will be 1300 cubic metres, over three times that of Mir.

Credit: NASA. 34,755 bytes. 320 x 245 pixels.

Program: ISS. Objective: Manned. Type: Space station.

In November 1998, on two continents, the first modules of the International Space Station had left the factories and were ready for orbit. Crews were in training for their assigned flights to the station. After fourteen years of tortured development and political upheaval, mankind's outpost in space for the 21st century seems finally ready to go.

President Reagan, in his spend-to-the-death race with the Soviet 'Evil Empire', tasked NASA in 1984 to provide America with space station Freedom. NASA lumbered into action. The current mantra 'faster, better, cheaper' was then unknown. A bizarre programme-management scheme had each station subsystem being developed by different NASA centres and contractors. By 1990, the first operational date had slipped from 1994 to 1997 and the station had ballooned into a $30 billion, 298-tonne monster.

Meanwhile, the Russians successfully assembled and operated the 124-tonne Mir station. The station's modules were evolved from those of the secret military Almaz station of the 1970s. Mir and its crews whirled round and round the world, through the collapse of the Soviet Union and Russian economic meltdown. By 1993, Russia had acquired unmatched experience in long-duration human flight, but it was apparent that there was no money for the follow-on Mir-2.

By this time, NASA had scaled down its station in the seventh redesign in nine years. This more modest station Alpha deleted most of the original science experiments, but would still cost more than Clinton was willing to spend. In October 1993, with the gunfire of the coup attempt outside their windows, NASA negotiators in Moscow agreed to the 'International Space Station' (ISS), a merger of stations Alpha and Mir-2.

The latest crisis came in April 1997 when NASA noticed that the essential Service Module, originally the core for the Mir-2 station, was still only an empty hull even though it was meant to be launched eight months later. Without the Service Module, the station would not have the rocket power needed to reboost its orbit and prevent it from spiralling in to a fiery re-entry. After an American ultimatum, Yeltsin put his government deeper into debt and saved the program.

Construction of the ISS began with the launch of the NASA-funded, Russian-built Zarya Functional Cargo Block (FGB, from its Russian name) in November 1998. A few weeks later, the shuttle *Endeavour* rendezvoused with Zarya and attached the first American module. Astronauts Jerry Ross and Jim Newman conducted three spacewalks to make electrical and data bus connections. By July 1999, it is hoped that the delayed Russian Service Module will dock with the complex.

Thereafter, permanent occupancy can begin. In January 2000, veteran cosmonauts Yuri Gidzenko, Sergei Krikalyov and astronaut Bill Shepherd will arrive aboard a Russian Soyuz spacecraft for a five-month stay. No less than 33 assembly flights are scheduled through to July 2004, with additional equipment, habitation or laboratory modules being added every month. At first the cluster will resemble Mir. But on the fourteenth flight, in the spring of 2001, the long truss will be installed. This will be extended on following missions and huge solar wings deployed, until the station achieves its final form.

NASA plans six research facilities initially devoted to fluids and combustion, materials science, gravitational biology and human zero-gravity adaptation. The first US lab module will be attached in March 2000, with the Canadian remote manipulating system arriving a month later. The Japanese JEM module is planned for July 2002. Europe's Columbus module is scheduled for October 2003.

A major concern is whether the Americans will have the nerve to stay the course when inevitable mishaps occur. The station, like Mir, will require constant maintenance. It could not be shut down if America stopped shuttle flights for years as it did after the *Challenger* explosion. Russian engineers calculate that there is a 23% chance that the exposed Service Module will be punctured by orbital debris during the lifetime of the station. Although the alloy and type of construction there would contain any puncture within a 70x70-centimetre panel, they believe an impact on the American section would result in fractures propagating quickly across a 400x400-centimetre area, leading to explosive decompression, an uncontrollable spin and rapid break-up of the station. Fortunately the probability of such an impact is only 2%.

The reality of 2001 will not quite match the vision of the film of the same name. But if all goes well there will be an international space station, where crews from all the nations of the Earth conduct experiments in the spirit of international science instead of that of nationalist competition. The systems proved on the station will then be available for the outward push of mankind, together, to Mars, Europa and 'Beyond the Infinite'.

Appendix - Comparison of ISS with Freedom and Alpha Stations:

ISS final configuration is similar to Alpha configuration 'A' in comparison to original 'Freedom' configuration:

                         Freedom     A      B         C
Cost to Finish ($Bil)     20       16.5     19.3     15.1
Complete Date             09/2000  10/2000  12/2001  01/2001
Annual Ops Cost ($Bil)    2.4      1.4      1.5      1.0
Crew Size                 4        4        4        4
Research Hours/Year       6566     6724     6566     6866
Alpha Gimbal              Y        N        Y        N
Total Avg. Power (kW)     68.3     57       68.3     46.5-62.9
Avg. User Power (kW)      34.2     31       40.3     24.4-40.2
Total Pressrzd Vol(m^3)   878      760      878      1117
User Science Racks        46       39       46       72
External Attach Sites     14       21       15       14
Tot. Asmbl/Outfit Flights 20       16       20       9
Tot. Asmbl EVA Hours      381      224      311      24
Logistics Flights/Year    4        6        6        6
Maintain EVA Hours/Year   253      187      253      80
Major Events: .
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Last update 12 March 2001.
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© Mark Wade, 2001 .