© 1999 by Donald F. Robertson.

E-MAIL: DonaldFR@DonaldFRobertson.com.

This article originally appeared in Space and Communications.

It was reprinted in Earth Space Review.

Building the Space Station represents a unique point in human history. Even as it is finally getting under way, few people -- supporters and opponents alike -- realize just how big and potentially important the project really is, or how difficult building it will be.

Learning to assemble large and complex structures in the microgravity of space is fully comparable to humanity's invention of large-scale construction in stone. That is believed to have been developed by the Egyptian physician and architect Imhotep, who built the Step Pyramid at Saqqara almost five-thousand years ago.

It is no accident that Imhotep is one of the very first names, of a person who was not a king, that survives in history. Once you have learned to build with stone, instead of mud brick, you can construct large and permanent structures outside of the desert, in the wetter climates that dominate Earth's surface. In building the Space Station, humanity is learning nothing less than how to build large and permanent structures in the microgravity environment that dominates the Universe.

That is a lot to live up to, but the completed Space Station will be suitably impressive. Seen from the overhead docking windows of an approaching Space Shuttle, the orbiting base is dominated by four dark blue solar "wings," two at each end of a long backbone truss. Each wing consists of a pair of thirty-four meter long solar panels, set end-to-end with the truss in between. Like giant flowers, these structures slowly track the sun, smoothly turning on bearings almost as wide as the Shuttle's huge payload bay -- rotating once as the Station completes each ninety minute orbit around the Earth. All together, the truss and solar wings span more than a tenth of a kilometer.

A dozen major pressurized modules cluster under the center of the truss, surrounded by an equal number of temporary and cargo modules, freight and rescue vehicles, and other major components. Behind this cluster is the Russian station, an attached set of modules and solar arrays mounted on their own, vertical truss.

This orbiting "village" houses and employs a full-time international crew of up to seven women and men. When a Space Shuttle is docked, the Station provides for an equal number of temporary workers.

Built on Earth, a structure like the Space Station would dominate the center a large city. Three-hundred-and-fifty kilometers overhead, building the Space Station is comparable, both in scale of effort and relative difficulty, with ancient Egyptians building the pyramids -- and just about as useful, say the project's army of critics. (See the box, "The Debate That Never Dies.")

Building the Space Station will probably be more difficult than anyone guesses today. This article will emphasize that difficulty since even on Earth all construction is risky. Because of the Space Station's size and complexity, there are likely to be many changes and difficulties along the way.

Can the project weather the inevitable setbacks? All of the analysts interviewed for this article agreed that the Space Station's political support is surprisingly strong. This year's funding battles were fought over space science, while significant cuts to the Space Station were never seriously considered. For better or worse, it is likely that something comparable to NASA's current plan will be built.

To understand why building the Space Station will be difficult, consider the first, relatively simple task of docking and connecting the Station's first two modules. The first module is an orbiting Russian "construction shack" called the Functional Cargo Block, or Zarya ("sunrise" or "dawn," as in a new beginning; the accent is on the second syllable). The second module is an American docking node, a port with six births, called "Unity."

Once in orbit, astronaut Nancy Currie used the Shuttle's Canadian arm as a crane to slowly lift the massive Unity module out of its launch position in the Shuttle's payload bay. She rotated the Node upright, then held the hatch at one end of it just over the orbiter's airlock in the front of the bay. Thrusters on the Shuttle were fired to push the Shuttle's airlock onto the module's docking mechanism, creating a hard dock.

With the Node extending up out of the payload bay, the Shuttle crew spent about a day maneuvering the orbiter toward the Russian block, which had been waiting in orbit.

Once the Shuttle approached, Currie used the arm to "snare" a grapple fixture mounted on the multiple docking sphere on the front of Zarya, careful of the Russian module's large and extremely delicate solar arrays and antennae.

The Unity module, sticking up out of the Shuttle's payload bay, blocked her view out of the Shuttle's overhead docking windows. So, Currie used television cameras in the payload bay and on the arm, and a Canadian "Space Vision System" that geometrically lined up dots painted on the modules, to place Zarya just above the far end of the Node. Again, the Shuttle and attached Node were driven into the Russian module with the Shuttle's thrusters. Overcoming minor problems caused by the Shuttle's arm, the crew tried again and eventually achieved a hard dock.

Over the next several days, Astronauts Jim Newman and Jerry Ross conducted three long space walks to connect a number of critical data and power umbilicals between the joined spacecraft. While the connections were made, Russian Cosmonaut Sergi Krikalev used portable computers on the orbiter flight deck to check that data were flowing correctly between the modules.

The astronauts installed communications antennae and attached tool boxes, handholds, and equipment sockets to the outside of Unity for future use. This hardware had to be installed in space, rather than on the ground, because there was not enough clearance massive Unity module and the edges of the Shuttle's payload bay during launch. The astronauts also manually released a stuck antenna on Zarya.

After checking air seals, part of the crew boarded the embryonic Space Station for the first time. Entering through the Shuttle's airlock, they installed air fans to circulate air between the modules, lights, and parts of the communications system.

Multiply all of that by nearly forty major missions over six years, some of which require far more complex assembly tasks. Astronauts and Cosmonauts plan to spend almost a thousand hours in open space, piecing the Station together. Experience suggests that this is an under-estimate.

Lieutenant Colonel Rich Clifford flew three Space Shuttle missions and became the first American astronaut to work in open space from Russia's space station, Mir. Later, he was Manager of Space Station Flight Operations at the Station's prime contractor, Boeing. He told me, "There are many unknowns in the space environment. Your power tool may fail and you have to go to manual backup. The more you use a manual tool, the more tired you get. When you get tired, you start making mistakes. There are some surprises up there, and we should not expect everything to go smoothly."

One of the greatest technical challenges of building a large orbiting base is that, as each part is added, the Space Station must remain a viable vehicle. It can't be built, like a sea-going ship, in dry-dock. At every point during construction, it has to function as a working spacecraft, keeping its solar arrays pointed at the sun and its antennae aimed at Tracking and Data Relay satellites overhead in geosynchronous orbit. It must always remain fueled and stable in orbit while awaiting the next component.

On Russia's Mir, each module is an independent spacecraft. When one of them failed to dock, the Russians simply backed it away, figured out what went wrong, and tried again. The Russian parts of the Space Station will be built the same way.

Western modules are incapable of independent flight and cannot be stored in orbit for a second attempt. That may seem short-sighted compared to the Russian method, but once a module is successfully docked, the hardware that let it fly independently becomes useless and takes up valuable volume inside the module. The shuttles carry enough resources to allow at least two attempts to dock each module. If all attempts failed, the Shuttle would return the module to Earth, while engineers figured out what went wrong.

Two Shuttle flights a year are reserved for "Station support," and one of these missions could be used to re-fly a module that failed to dock. Since the early Space Station must be assembled in sequence, that could cause a domino effect, delaying the rest of construction. Astronaut Kevin Chilton, a previous Manager of Space Station Operations at NASA, said, "By design, whatever configuration you're in, if you have to stop [construction] you could survive [in orbit] for a year without adding any new elements or parts."

Russia spent many years experimenting with small Salyut stations, consisting of just two or three elements, before trying to build Mir. They were concerned about rigidity: could a large and complex structure like Mir, held together by nothing but its docking ports, be rigid enough not to leak air? Cosmonauts literally pushed themselves into the walls of early Salyut stations to test the harmonic vibrations of docked modules.

Unlike the Russians, NASA has not tested their plans by building smaller, experimental space stations. The International Space Station is far bigger than Mir, and its structure is more complex. While Mir's major components are all directly docked to each other, the Space Station has large and massive elements supported on long open trusses.

Clifford said that Boeing is "pretty confident in the analysis of the dynamic loads and the static loads of the [main] truss or backbone of the Space Station, and that it will accommodate all of the loads that we expect to impart on it." If the ground-based analysis proves wrong, NASA does not currently have the ability to weld extra bracing onto the truss, although Clifford said that this is something that can be developed if it proves necessary. NASA had planned to try out a Ukrainian space welding tool on a Shuttle mission, but that test was bumped for Station assembly experiments that NASA considered more urgent.

The Space Station has many thousands of connections, and, no matter how careful ground-based engineers are, once you get to orbit the risk that some vital connection won't fit is high. Russia's delays in building the Service Module may prove to be a blessing in disguise. Most of the early NASA modules were completed more-or-less on time, but since they could not be launched, they backed up in the Space Station Processing Facility. NASA used this opportunity to attach fluid, power, and communications lines to make sure that they all "talked" to one another.

Experience with Russia's Mir space station has illuminated a number of potential risks that NASA had not expected.

Mir has repeatedly lost her "sun lock," with inevitably dire results. With the solar arrays no longer pointed at the sun, Mir's batteries quickly drain. Mir's crew wakes up in the pitch dark of a powerless station. They find their way through a maze of dark, equipment-filled modules to their Soyuz crew transport. There, they use manual controls and the Soyuz' thrusters to point the entire station toward the sun until the batteries gain enough charge to take over and run the computer. It takes several days to spin the high-power gyrodynes back up. The "gyrodynes" are massive gyroscopes used to automatically orient the station while burning little thruster fuel.

Once the Space Station gets past the United States' laboratory being installed, it will have redundant computers to maintain attitude control. NASA is designing work-arounds to regain attitude control as soon as it is lost and adding extra batteries so the Station can last longer without solar power.

One of the biggest lessons learned from the famously messy Mir involves logistics, making sure the Space Station has the supplies it needs when it needs them. Originally, the plan was to keep most large spare parts on the ground. NASA now intends to keep far more spare hardware in orbit than originally planned. That way, things can be fixed immediately rather than waiting for the next Shuttle or Russian Progress freighter. Platforms are being designed for the truss, which will hold the extra equipment.

One life-threatening problem is unavoidable, and will affect the Space Station as long as it remains in orbit. Space debris range from natural meteor showers, to human junk like derelict rocket stages and tiny paint chips, most traveling at extremely high speeds relative to the Station. Coincidentally, natural meteor showers are expected to be especially severe during early Station construction.

Space Station components are designed to withstand impacts by anything smaller than one-tenth of a centimeter without significant damage, and this covers the vast majority of objects likely to strike the Station. However, the smallest objects that can seen by ground-based radars are about ten centimeters across. Objects between these sizes are relatively rare, but could severely damage the Station, possibly penetrating a module and putting the crew in immediate danger. Independent analysts think that the risk of this happening at some point in the Station's fifteen year design life is high.

Japan plans to test a "pulsed laser" which can detect approaching debris. Unlike Shuttle orbiters, which frequently maneuver to avoid debris, the massive Space Station is a sitting target. Japan's laser may give the crew time to prepare to close off modules as soon as they are damaged, but meteor impacts may have to be "weathered" and repaired after they happen. Russia and NASA attempted to fix the Spectr module on Mir -- punctured when it was accidentally rammed by a Progress freighter -- to practice repairing Space Station modules. Finding and repairing the leak proved to be impossible, showing that a holed module may be a difficult problem to deal with.

That, and Mir's many near-disasters, beg the question, will the Space Station be safe? The short answer is, Of course not. The Space Station is an experimental base at the edge of a dangerous frontier: no one should expect it to be safe, least of all the astronauts who volunteer to work on it. On the other hand, the Station is not a space ship in the conventional sense. It is a permanent outpost in a stable orbit, with many separate airtight chambers, spare parts, and other supplies always close at hand. The Russian part of the Space Station, adapted from the Soviet Union's planned Mir-2, is largely self-sufficient. Each half of the Station has independent power and life support temporarily capable of supporting the entire crew. At all times, there will be enough rescue vehicles to return the entire crew to Earth.

The Space Station will quickly become the center of human activity in Earth orbit, and its very existence will increase the overall safety of human spaceflight. If a Station-bound Shuttle or Russian Soyuz crew transport were damaged and incapable of landing, even the early Space Station would be able support the crew for a short period while a rescue was organized.

Once the Russian Service Module is attached, sometime in early 2000, the Station will have a permanent life support system, and should be able to support a stranded crew for some time.

* * *

Even as it is being launched, the Space Station's design continues to evolve, providing hints to its ultimate future. NASA has added a third berthing Node to improve flexibility and safety by increasing the number of docking ports. Ultimately, this will allow the Station to expand beyond its initial design, currently planned to be complete in 2004. Italy will build the Node free of cost to NASA in exchange for experiment time on board.

Another reason for the additional Node is to provide a berth for a new kind of experimental multi-purpose module called "TransHab". TransHab is a low-weight cylindrical habitat made out of many layers of extremely strong fabric. After launch on a single Shuttle flight, it is inflated like a balloon to three times the volume of a typical Space Station module. The Station's original habitation module is "on hold," to save money. Because of TransHab's relative simplicity, some managers at NASA believe it would cost no more to build TransHab from scratch than to complete the habitation module.

After it is tested on the Space Station, TransHab is specifically designed to serve as the habitat module for a trans-Mars interplanetary spacecraft, and ultimately as a shelter on the surface of Mars. NASA also plans early tests of fully-closed life support, even growing oxygen- and food-producing plants on the Station.

Following an embarrassingly public debate, NASA Administrator Daniel Goldin over-ruled some NASA managers to confirm that the space agency's long-term goal remains to develop the technology to go to Mars.

TransHab is an example of the Space Station's most valuable capacity, argues space historian Tim Kyger, formerly a space expert on the Congressional staff and now Washington representative for an entrepreneurial launch firm. The Space Station allows NASA to flight test the technologies required to open the Solar System to human activity.

Kyger calls TransHab NASA's "stealth Mars program," and considers it a shrewd political strategy. By testing the technologies for interplanetary flight at the Station, NASA will develop those technologies without ever having to get formal approval for a Mars mission. This also will keep Mars in the news while avoiding the kind of large project that would engender political opposition.

"By the time it actually happens," says Kyger, "people will not be surprised" that we are going to Mars. "They will expect it."

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SPACE STATION DEPLOYMENT,

FLIGHT AFTER FLIGHT AFTER FLIGHT

by

Donald F. Robertson

All great projects start small, and the Space Station is no exception. During its first year in construction, the orbiting base will be much smaller than Russia's Mir space station, now in orbit.

Because of problems with Space Shuttle wiring, and reported troubles with Russian software, Station assembly is running several months later than planned in the latest public schedule (June 1999). The project will almost certainly fall even further behind, but the sequence of the first eleven missions is unlikely to change.

FLIGHT-1A/R

(the first mission)

Zarya is the first component of the Space Station and it was successfully launched on 20th November 1998. It is adapted from Mir-2, planned by the old Soviet Union to replace Russia's current orbital base, Mir. When Russia entered the Space Station program, Boeing, the American prime contractor, paid the Russian space company RSC-Energya to modify a Mir-type module for use on the International Space Station. (The "A/R" designates that the first module is an American and Russian co-production.)

The Zarya "Functional Cargo Block" is essentially a complete, independent spacecraft, weighing some twenty tons. It is 12.5 meters long and just over four meters in diameter.

Analogous to the initial shelter and fuel depot at a remote construction site, the Functional Cargo Block is the core from which everything else will ultimately be built, and the eventual link between the Western and Russian halves of the Space Station. "You've got to have something to build on, and that something has to be sturdy and stable and provide you with support," said Astronaut Kevin Chilton, a previous Manager of Space Station Operations at NASA.

Zarya contains a relatively small habitable volume, berthing ports to dock future modules, and rocket engines both for re-boost and to orient the module in space. It has a large volume of fuel to stabilize the early Station. Refueling lines were recently added to the block's nadir (Earth-facing) port to increase the Station's ability to remain in orbit if there are problems during construction. Russian Progress freighters or U.S. Space Shuttles carrying fuel and bulk cargo can now dock with the port and transfer fuel. Later, the Functional Cargo Block will be used as a fuel depot.

The solar arrays span thirty meters providing up to 7.5 kilowatts of power. Once the Russian block's arrays and antennae were deployed, and most of its systems were activated, the on-board rockets were fired to move it from its temporary parking orbit to the Space Station's assembly orbit. There, it waited a little over two weeks for the Space Shuttle Endeavour to deliver the next component.

FLIGHT-2A

(the second mission)

The initial American part of the Space Station is the first of three "Nodes." Each cylindrical Node contains four equally-spaced radial side ports, and one port at each end. Attached to the end ports are Pressurized Mating Adapters, tunnels strong enough to hold a one-hundred ton Shuttle. One adapter connects the Node to the Functional Cargo Block launched earlier; the other provides a berthing port for Space Shuttle orbiters and Russian Soyuz crew transports. Zarya's solar arrays provide the power to operate Unity, which has no power source of its own.

Connectors external to the adapters distribute power and data between the two modules, and to docked Shuttles and Soyuz.

The Nodes are modules in their own right, containing a large pressurized volume, and utilities like air supplies, wiring, and ducts. This first Node will be the core of the American station, to which most of the United States' components will eventually be attached.

One day after Unity was docked to Zarya, the Space Shuttle left and Zarya's engines fired to boost the Station to a higher orbit. Over the following months, friction with the extreme upper atmosphere caused the orbit to decay back down to the Station's construction altitude.

A logistics mission on the Space Shuttle Discovery was the third flight on the Space Station's schedule, launched on 27th May 1999. This mission used a commercial Spacehab double cargo module to stockpile about two tons of supplies at the Station. An American construction crane, and parts of a Russian one, were installed on the Station's exterior.

Because of Russia's on-going economic problems, Shuttle logistics missions have replaced many of the originally planned Russian Progress freighters. Before leaving, Discovery used excess fuel to boost the Station's altitude.

FLIGHT-1R

(the fourth mission)

The third major component of the growing base, the Russian Service Module, is very similar to the "base block" of Mir. Called Zvezda, it is thirteen meters long and about four meters in diameter. It has three pressurized compartments. The forward compartment has three berthing ports, one facing up away from Earth, one down, and one facing forward. At the back of the Service Module is a large airlock equipped with Russian space suits.

The middle compartment contains personal quarters for the crew -- each with a small window. It also has a galley, exercise equipment, toilet, and a table with a large viewing port. The Service Module supplies life support for the early Station, as well as communications, electricity, and a data processing and flight control system provided by Europe.

The Service Module is launched on a Proton rocket, and docked via remote control to the Functional Cargo Block and Node-1, already in orbit.

After the Service Module is docked to the Station, a second Shuttle logistics mission flies with a double commercial Spacehab module. The Shuttle Atlantis unloads supplies, begins outfitting the new living quarters on Zvezda, and finishes construction of the Russian crane.

FLIGHT-3A

(the sixth mission)

Flight-3A features four spacewalks. Astronauts install an aluminum truss to the Node's zenith port (which faces away from Earth). The "Zenith-1" or Z-1 truss supports the large Ku-band dish antennae aimed at geostationary relay satellites, and "Orbital Replacement Units" containing the communications electronics. The antennae give the Station high-data rate full-orbit communications with Earth. Orbital Replacement Units are standardized electronics boxes containing Space Station subsystems; an old one can be easily exchanged for a new one, either by the crew or using the Space Station's robot arm. The truss also contains supporting structures and utility lines for a massive solar power array to be added later.

The Zenith-1 truss contains gyroscopes which rotate at 6,600 revolutions per minute. These apply torque to the Station, orienting it relative to the Earth while minimizing fuel use. Plasma Contactor Units emit electrons to keep the Station electrically neutral while it plows through the low Earth orbit radiation environment. The truss has a number of workstation sockets, hand-holds, and foot restraints.

A third Pressurized Mating Adapter is docked to the Earth-facing berth on the Node, opposite the truss.

EXPEDITION-1

(the seventh mission)

With the Zenith-1 truss installed, the Space Station is ready for its first permanent crew. A Russian Soyuz transport carries Yuri P. Gidzenko, Sergei K. Krikalev, and William M. Shepherd to work on board the Station for about four months. They continue checkout and assembly work, do some early science, and test mission procedures to be used during operational Space Station expeditions. The crew's Soyuz spacecraft remains with the Station after they leave, as an emergency lifeboat.

FLIGHT-4A

(the eighth mission)

Flight-4A is one of the most visually spectacular flights of the entire Space Station assembly. Astronauts install the first of the Station's four giant solar array wings in a temporary position on top of the Zenith-1 truss. This double array provides high power for early science experiments. Later, the wing will be moved to its permanent position on the port side of the backbone truss.

The astronauts start by mounting an additional truss segment to the top of the Zenith-1 truss. The new truss contains replaceable batteries, two large ammonia radiator panels, pumps to move the ammonia coolant, and the solar wing itself. Once installed, the crew slowly unfurl each side of the array to its full thirty-four meter length -- for a total span (including the central truss) of over seventy meters.

From this point on, the Space Station becomes a high drag vehicle. The giant solar wing plows through Earth's thin upper atmosphere, causing the Space Station to lose altitude much faster than before. The Station is designed to survive for about ninety days without refueling, but after Flight-4A, to avoid falling behind, Progress tankers must be launched to schedule. Space Shuttle refueling missions were planned before the Russians joined the program, and, given Russia's economic troubles, many of those are likely to be reinstated.

FLIGHTs-5A through -6A

(the ninth through the eleventh missions)

Even with the uprated, "heavy lift" Shuttle Endeavour with its Aluminum-Lithium external tank, the laboratory Module is too heavy to be launched with most of its science gear. On Flight-5A, the "Destiny" science module is launched with only four of its twenty-four experiment racks on board. The laboratory is docked to the Node, opposite the Russian modules.

One logistics Shuttle flight, carrying supplies and more racks for the lab, is launched between missions 5A and 6A. This flight represents the first use of a re-usable Italian logistics module called Leonardo.

On Flight-6A, additional science and storage racks are launched inside a second Italian logistics module called Raffaello. The Space Station's Remote Manipulator System, a Canadian robot arm, is attached to a mount on the exterior of the Lab Module. Later, the arm will be moved to a kind of rail car which moves around the Station on truss-mounted tracks.

If all goes well to this point, approximately one year after assembly began, the Space Station is ready for its first complex scientific experiments. Station assembly continues for about four more years, slowly adding new capabilities and the international laboratories.

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WHEN A SHUTTLE IS LOST. . . ?

by

Donald F. Robertson

Reliable Space Shuttle operations are vital to building the Space Station, and important for using it. Sooner or later, it is inevitable that another Shuttle will be lost in a catastrophic accident. What happens to the Space Station then?

Kevin Chilton, an earlier NASA Manager of Space Station Operations, said that if NASA lost one of the three orbiters that have been upgraded into "heavy lift" vehicles, "you continue to fly with the remaining high performance vehicles. You would have to slow down your build rate, but you could still build" the Space Station.

And after the Space Station is safely in orbit? "That's what the Russians are for," says John Pike, aerospace analyst with the Federation of American Scientists. "As long as [NASA] has the Space Station with the Russians involved," if a Shuttle is lost, the Russians can probably launch enough fuel and supplies to keep the Station in orbit and productive until the Shuttle begins flying again. Chilton agreed. "If you had a Challenger-like accident, where you had a significant stand-down and you had to make design improvements to the Shuttle, that is a benefit of being teamed with the Russians."

The Space Station might survive in orbit when another Shuttle is lost; will it survive in Congress? "Yes," says Pike, who believes that the Station has strong underlying political support. "It will take some singing and dancing and arm-waving. But, in broad terms, you can see what the space program looks like with the Russians, and with the Space Station, but without the Shuttle. If you take the Russians out and you lose the Space Shuttle, you don't have a [human] space program."

Even with perfect Shuttle reliability, the Space Station project will run into problems getting enough access to orbit. There are serious questions about whether the Russians can build enough Progress tankers to refuel the Station. If not, this job will fall on the already-stretched Shuttle. Nonetheless, Chilton said that the three "heavy lift orbiters are pretty much scheduled [exclusively] for the Space Station." That leaves Columbia to support the Hubble Space Telescope and conduct the other non-Space Station missions that require a crew in orbit.

Advocates for commercial space development argue that commercial launch vehicles should be used to supply the Space Station. The large number of logistics missions could provide strong incentives for companies to reduce the cost of access to orbit.

In the short term, relying on the commercial launch industry might not be easy. The Space Station is being built at a time of unprecedented demand for commercial access to orbit, and there is little existing launch capacity anywhere in the world that is not already spoken for. Nobody dreamed this would be a problem when the Space Station was first proposed.

On the other hand, troubles with several major commercial satellite projects are showing how fragile some of that commercial demand may be. Several new launch vehicles will come on line in the first few years of the next century, and many analysts are already worried about a glut in capacity to get into space. That may not be a bad thing, at least for the Space Station. As intensified competition lowers launch costs, the Station may cost less to operate.

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WE ALREADY HAVE A SPACE STATION:

WHAT HAPPENS TO MIR?

by

Donald F. Robertson

The Space Station's orbit is moderately similar to that of Russia's existing space station, Mir. Should Mir be left in space as a source of spare parts and equipment, and as an orbiting life boat in case of a catastrophic emergency on the Space Station? Russia dearly would like to keep her independent orbital base alive, possibly as a commercial outpost, even after the newer Space Station is built. Unfortunately, Russia has no obvious way to come up with the hundreds of millions of dollars a year it costs to maintain Mir.

In the past, Russia has shown remarkable inventiveness at earning money from her orbital base, usually by flying other countries' experiments or astronauts for a fee. However, Boeing had a contract to market space on Mir for commercial use, and little came of that; nor has money materialized for several other increasingly desperate schemes. Many of Russia's old customers are likely to be holding out for the newer, international base. Currently, Mir is abandoned in orbit as Russia waits hopefully for money to appear.

Even if money is found, Russia will have trouble building enough Progress freighters to refuel even one base in orbit, let alone two. The Russians are under intense pressure from NASA to get Mir out of orbit by early 2000 so that they can use their limited resources on the newer station.

Mir would be the largest and most complex artificial structure ever to enter Earth's atmosphere. There is no guarantee that Mir will fall harmlessly into the ocean, as planned. Both NASA and the Russians have a miserable record at predicting where large spacecraft will fall after re-entry.

There is a third alternative. "There is no reason," said Rich Clifford, an ex-astronaut and a previous Boeing Manager of Space Station Flight Operations, "that [Mir] modules that are in good shape, such as the Piroda [environmental research] module, could not be undocked from Mir and re-docked to a berth on the Space Station." NASA has vetoed this idea, ostensibly for safety reasons. NASA also refused to help move valuable internal equipment from Mir to the new base. Earlier, NASA refused Russian requests to make travel between Mir and the Space Station easy by putting them in the same orbit.

To outsiders, NASA's reluctance to compromise on Mir often appears unreasonable, even though any compromise would cost NASA money. It is easy for Russian legislators to detect an American plot to deprive Russia of her independent prospects in space, contributing to the growing animosity between the two countries. Russian resistance to abandoning Mir is likely to increase as the terminal date grows closer.

Given the greater resiliency that having a backup station would provide to the human infrastructure in low Earth orbit, it would almost certainly be best to use the fuel that would have de-orbited Mir to boost it to a higher storage orbit, where she may be of use later on.

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THE DEBATE THAT NEVER DIES:

WHY BUILD THE SPACE STATION?

by

Donald F. Robertson

The immanent prospect of a permanent base in orbit has intensified opposition to human spaceflight, especially among scientists. The Space Station represents something of a point of no return: once it is finished, tens of billions of dollars will be invested in hardware and people in orbit -- and in ground-based facilities in Congressional districts.

Politically, it may be difficult to retreat from that investment in human space exploration, even in the face of great financial or technical hardship. Russia has a space program today largely because she had a space station. Even in the economic depths immediately following the collapse of the Soviet Union, it proved politically impossible to retreat from the investment in Mir, and it is proving almost as difficult during the current economic collapse. Many feel that the same will be true of the International Space Station, and that it will become a permanent drain on the world's finite funds for science.

The long-term cost of the Space Station over its full fifteen-year operational life will be some fifty-eight billion dollars, according to NASA. That includes the money that has already been spent. However, if you add fully-amortized Shuttle flights and other expenses to the tab, critics say the Station will cost one-hundred billion dollars or more -- and that's just the United States' share. For what NASA spends on the Space Station in just one year, more than eight Pathfinders could be sent to Mars. What do we get for all of that money?

Nothing, says Robert Park, a physicist with the American Physical Society who is one of the Space Station's most steadfast and respected scientific opponents.

I asked Park when it will be too late to stop building the Space Station. It is "never too late." Park would write off the billions already invested "in the blink of an eye." Even after the base is partially built in orbit? "Stop! Putting good money after bad is not a good policy at any time."

Park says that when the communications satellite was first proposed by Arthur C. Clarke, it was envisioned as a human space station with a crew "to change the vacuum tubes." In reality, today's comsats are relatively inexpensive robots with far more capacity "than anything Clarke could have ever imagined." That is a lesson that NASA has yet to learn: the Space Station is something out of the past, says Park, and robots can do everything that humans can do in space, at far less cost.

Park's opponents say that robots cannot do anything they are not programmed to do, and that the Space Station will pay for itself by finding the unexpected. Most Station advocates interviewed for this article hedged their answers, saying the Space Station has many purposes and science is only one of them. However, some people who have studied the history of science believe that Station opponents greatly underestimate how scientifically valuable the first fully-equipped laboratory in orbit will prove to be. For example, rather than trying to guess how a comet works by looking at it from afar, or by sending a robot to examine a comet "in the wild," scientists could evaporate various ices under controlled microgravity conditions in the laboratory module to test theories on how cometary physics actually works.

Space historian Tim Kyger, a former space expert on the Congressional staff and now Washington representative for an entrepreneurial launch company, argues that to date space science has been almost entirely observational. For the first time, the Space Station will allow hands-on, experimental, laboratory science in the environment that dominates the Universe, outside of Earth's "special case" environment. Historically, a new capability in a new environment has almost always led to dramatic and completely unexpected advances.

Asked if he could justify the tens of billions of dollars being spent on the Space Station in potential scientific results, ex-astronaut and a previous Boeing Manager of Space Station Flight Operations, Rich Clifford, said, "I think the payoff in benefits is truly in the medical community. We will have a tremendous research facility up there . . . and we don't know what the results will be."

Robert Park scoffs at the idea of doing medically valuable biology on the Space Station. "It almost always comes down to these few pathetic experiments with protein crystals which they hype beyond belief." Advocates say that growing larger and more perfect protein crystals in the microgravity of space lets scientists better measure their structure; that knowledge allows easier and better drug design.

Ursula Goodenaugh, Professor of Biology at Washington University in St. Louis, agrees with Park. "The reason that I have taken time out of my lab to comment on this [Space Station] is that what is being offered [in Congressional testimony] is embarrassingly inaccurate." She believes that any scientifically valuable microbiology that can be done on the Space Station can be done on Earth. She fears that "when the Space Station fails to cure cancer," as has been explicitly advertised by NASA, it is scientists like her who are going to be left trying to explain why it was built.

Coincidentally, I interviewed Goodenaugh on the same day the NEW YORK TIMES reported that the number of new AIDS cases worldwide is now believed to be some 120,000 per day, twice the number previously thought. Unless a solution to AIDS is found, almost all of these people will prematurely die. Goodenaugh cited this figure, and said, "The cost of doing research [in space] is so huge that [for what the Space Station project is spending] we could build on this planet vast institutes to study" diseases like AIDS, which would answer far more than we will discover in space.

The real motivation for studying biology on the Space Station is not to learn anything about biology per se, Goodenaugh accused, but to prepare for colonizing Mars. "The closest analogy is religion," said Goodenaugh. "There really do seem to be some genuine zealots," people for whom human space exploration "is so important that it outweighs any other criteria. For others, that is not a relevant way to prioritize." She would feel more comfortable if human spaceflight was presented without scientific justification. "That would be much more honest, then people could listen and decide where they come down."

Clifford did not dispute these views, saying, "The ultimate goal of the Space Station is to do life science research with the goal of putting humans on Mars. I can't say that the billions of dollars spent on assembling the Space Station could not be put into better use doing common research down here, but it is the human desire to explore, and we are going to explore and accomplish these [scientific] objectives at the same time."

I asked Goodenaugh if the human space program is not a natural extension of the historic human drive to expand into new territory. She agreed that, in theory, this is true, and even volunteered that the drive to expand into new ecological niches is basic to all biology. However, "The space program to date has shown us that there are a lot of things that we can put on television that just aren't going to happen" in reality.

From a more positive perspective, John Pike, aerospace analyst for the Federation of American Scientists, agreed with Goodenaugh's religious analogy. He said, "You have this very small minority of people who have had this personal 'revelation' that [human] spaceflight is important and means something. They have to trick the other ninety-five percent of taxpayers into paying for their own private, religious obsession." Does Pike share this 'religion'? He laughed, and said, "Yes! My first conscious memory was when I was four years old and went out into the back yard and saw Sputnik-1."

Nonetheless, Pike agrees with Station opponents that, "The value of the science that can be done on the Space Station is trivial compared to the cost of the Space Station. Piloted spaceflight is about politics."

Today, the Space Station has just three purposes, says Pike. None of those have anything to do with science. Those purposes are, to "demonstrate that America and Russia are not adversaries, to keep Russian rocket scientists inside of Russia and out of North Korea, and to sustain political support in Congress for the piloted space program" which is important to some politically powerful individuals. Pike believes that, in spite of all the controversy surrounding the Space Station, "All three of those [purposes] are working, which says to me that this is a politically well-grounded program."

Historian Tim Kyger agrees, saying that the Space Station is "our prime foreign policy engagement with Russia, and cheap at the price. History will show that this was the correct thing to do." Kyger also agrees that the Space Station is on firm political ground, saying that the political debate has degenerated to a squabble between Congressional Republicans and the Administration over "who is going to take the political heat for the cost overruns."

Asked if geopolitics can sustain human spaceflight over the long term, Pike laughed and said, "Well, we've managed to fool 'em for four decades now."

Maybe so, but Robert Park views the whole idea of human spaceflight as fundamentally inappropriate to the space environment. The very first discovery of the space age was that "radiation levels in space are much more severe than we had previously imagined. Even if we were going to spend this enormous amount of treasure" to send human beings to Mars, Solar and cosmic radiation will ensure that Mars "is as far as we can go. No one in their wildest dreams" thinks that human beings can physically explore the rest of the Solar System.

As might be expected of an astronaut, Rich Clifford does not agree. Asked if he saw any ultimate limit to human endeavor in space, Clifford said, "I sure don't. A hundred years ago, people would have thought we were crazy to say that we could even leave the Earth's atmosphere." What about the radiation? "That is what we are hoping to get an answer to on the Space Station."

So, who is "right?"

It should be obvious to anybody following this debate that there are two completely different world views involved. One view sees the singular purpose of space exploration to be the scientific reconnaissance of the Solar System and the Universe. The cheapest way to achieve that is with robot spacecraft and automated telescopes. The other view sees the Solar System as an arena for detailed physical exploration by human beings, leading to space-based industries and eventual trade between planetary colonies.

Both sides are technologically and scientifically literate. Rhetoric aside, it is likely that a future dominated by either robotic or human exploration of the Solar System is viable, albeit at greatly differing costs.

Almost everyone interviewed for this article agreed that this is essentially a religious debate. It is in the nature of religious arguments that they cannot be proved right or wrong.

Human spaceflight is extremely expensive, and there may indeed be better ways to spend the money. Yet, the cultural milieu, steeped in Star Trek, is not opposed to the Space Station -- and the long-term financial commitment that it represents.

END