At present, Mir is orbiting without a crew. The last two cosmonauts to visit the station returned to Earth in June. The next crew is set to go up in November, according to MirCorp, the private consortium that recently agreed to lease the station for commercial purposes. What's more, in an effort to add years to the station's lifespan, cosmonauts will begin testing a new propulsion technology some time later this year or next.

The heart of the new technology is an electrodynamic tether, a long thin wire that will attach to Mir and draw electrons from Earth's ionosphere [Fig. 1]. As with an electric motor, this current-carrying wire will experience a force as it passes through Earth's magnetic field, a force that will, it is hoped, stabilize Mir's altitude.

With its economy in a decade-long decline, Russia has been hard pressed to maintain both Mir and the ISS. The Russian-built Zvezda service module for the ISS, for example, should have been launched more than two years ago; it is now expected to go up this month. Schedules for other components promised by Russia have similarly slipped.

NASA had tolerated Mir's existence as long as terminal breakdown or euthanasia seemed imminent. And indeed, the Russian government had promised to de-orbit Mir sometime this year. But in February, the Netherlands-based MirCorp, backed by two U.S. and British telecommunications multimillionaires, agreed to sink US $100 million to $200 million a year in the hobbled space station. The money is being used to finance new launchings and to upgrade the station for research and commercial activities, including advertising and space tourism.

NASA administrator Dan Goldin is not amused. Among other things, he has charged that Mir's revival is being accomplished using spacecraft promised to Mir's international counterpart and paid for by the United States. The Mir-saving tether technology itself is also largely based on NASA-sponsored research and development.

The U.S. space agency desperately needs Russia's full attention on the ISS. "Initial manned capability" of the station is set for November--the same month a crew is scheduled to go to Mir--and ISS construction is supposed to wrap up by mid-2003. But work on the station has already been stalled for over a year, and this new development could shift the timetable months, or even years, into the future.

Undeniably, Russia has a strong attachment to the 14-year-old Mir, a lingering symbol of the once-mighty Soviet space program. In fact, throughout much of last year, a groundswell mounted in Russia to preserve the station--somehow. Space officials, cosmonauts, politicians, scientists, and other public figures paraded before the Russian news media to call for Mir's perpetuation beyond the promised termination date.

Russian President Vladimir Putin has said that his Administration is committed to supporting both space stations. In February, he vowed to "stand by all existing agreements" on the ISS. Those agreements include providing the service module, with its crucial life support systems; docking and airlock modules; a science power platform; and other research units. Further, Russia is to launch two manned Soyuz spaceships and four to six unmanned Progress supply vehicles to ISS every year for at least five years.

On 12 April, the 39th anniversary of Yuri Gagarin's mission as the first cosmonaut in space, Putin restated his commitment to both projects. But, he added, "national priorities must take precedence."

A firefly for Mir What exactly is this engineering novelty that may save Mir? Simply put, the electrodynamic tether--nicknamed Firefly--will attach to Mir and draw electrons from Earth's ionosphere to flow along its length. This setup will create a current, which will in turn raise the station's orbit. If successful, it will be the first practical application of nonrocket propulsion in space. [For a discussion of how electrodynamic tethers work and other promising applications, see "The tether solution" ] At present, regular shipments of rocket fuel are needed to maintain Mir's altitude, so the tether will make keeping the station in operation much cheaper.

Much of the technological groundwork for the Mir-saving tether was sponsored by the U.S. space agency, an irony that experts both inside and outside NASA have noted. As early as 1996, scientists and engineers from NASA's Marshall Space Flight Center, Boeing, the University of Michigan, the Massachusetts Institute of Technology, the Smithsonian Astrophysical Observatory, and Tether Applications proposed using an electrodynamic tether for keeping the ISS aloft. The actual design and construction of Firefly was done by a team of Russian and non-NASA U.S. engineers, working on shoestring budgets measured in the tens of thousands of dollars. Their work was sponsored by a California-based group called Finds, the Foundation for the International Non-Government Development of Space.

To develop Firefly, Finds turned to Joe Carroll, a San Diego, Calif., engineer and a veteran of many NASA and U.S. Defense Department space tether experiments. Carroll teamed up with Russian space engineer Vladimir Syromyatnikov, who has worked on the hardware for all of Russia's space stations. Once the MirCorp funding came through, building the tether took only a few months. In April, it was shipped to Russia for launch aboard a Progress supply drone later this year.

Firefly, formally known as the Mir Electrodynamic Tether System, or METS, will consist of a 5-km-long anodized aluminum wire hooked at the end of the station's Kvant 2 module. The 1-km section farthest from Mir will be bare metal, with a surplus jet backpack attached at the very end for ballast, to keep the line pointing straight down toward Earth. Just outside the module's airlock hatch, an electrical panel will be installed, and two 48-wire cables will connect the system to Mir computers and power supply. A few kilowatts of power from Mir's solar arrays will be channeled to the tether--power that will be needed to reverse the direction of the current in the wire, so that the station's orbit is raised, rather than lowered. The total assembly weighs 150 kg.

Once the tether is reeled out to its full length, the bare metal strip will begin collecting electrons from the ionosphere. As the electrons move up the wire toward the space station, a hollow cathode emitter mounted on Mir will spray them back into space, connecting the circuit.

To install the tether, Mir cosmonauts will perform a space walk. They will mount the apparatus on a ladder just outside the airlock, connect one of the two electrical cables, manually deploy a small pilot tether (which will later be used to tug the main tether out), and then attach the main tether to the old jetpack. Following verification of the space-to-ground data link, the crew will return to Mir.

Later that day or soon afterwards, the tether unreeling will begin. At full deployment, which takes about 5 hours, the tether will exert a force at its attachment point on Mir of about 12 newtons, displacing the complex's center of mass about 10 meters toward the ballast end of the tether. After several days of low-power checkout, the tether will be fully powered on.

There will be inefficiencies, of 25-30 percent, in this unearthly electrical motor. The main losses will be voltage drops in the electron collection, conduction, and emission, plus some loss in boosting the power from Mir's 27-V bus voltage to the 400-1500 V used by the tether system. Even with these inefficiencies, though, the numbers are attractive. The most efficient propulsive systems, such as an ion thruster or a plasma thruster, would consume about 0.25 kg of propellant per hour per newton of thrust.

Tether experts calculate that each kilowatt of power from the solar arrays will yield about 0.1 N of thrust. It's a tiny thrust, to be sure, but it is nearly continuous. Mir's altitude loss due to air drag is an annual 50-100 km, and the tether's air drag is about one-sixth that of Mir's. An average power of 1.4 kW would compensate for all air drag on Mir and the tether. That comes to about 1500 kg of saved propellant per year, or nearly one full load of a Progress supply ship, worth about $30 million.

The only nonrenewable part of METS is the 3 kg of xenon gas per year that will be used in the hollow cathode; the gas is ionized to stimulate the electron flow. The tether wire itself may also need replacing from time to time. Experts estimate that the risk of a Firefly-length tether at Mir's altitude being cut by a micrometeroid or space debris is 30-40 percent per year. So the plan is to send up spare parts--especially reels with new tethers--on later supply flights.

Telemetry will allow the Mir crew and the ground staff to monitor Firefly's hardware status, voltage, and power converter current output, as well as a few other parameters. The tether's computer will keep track of reel turns, temperatures of key components, and xenon tank pressure, and will provide self-test results plus more detailed data on any anomalies. Software commands to the Firefly computer will allow starting, stopping, and modifying control sequences, plus setting operating power levels and turning heaters on and off. If needed, the entire tether assembly can be jettisoned from Mir by either a hard-wired command or software.

So just how much time could Firefly buy Mir? Russian space experts insist their space station has many years of useful life remaining. Yuriy Semyonov, director of the Moscow-based Energia Space and Rocket Corp. (which builds and operates all Russian-manned space vehicles), estimates that after 14 years, Mir is barely halfway through its useful life. "We would want Mir to stand by the ISS at least over the first 15 years of its existence," Semyonov told reporters at the MirCorp contract signing in February.

Will past be prologue? Of course, the above scenario is the ideal. But space tethers are not magic, and past trials have been plagued by unpleasant surprises. The most dramatic occurred in 1996, when the 20-km-long insulated wire of NASA's Tethered Satellite System broke and sent its Italian satellite payload flying off [see "Spectacle in the sky"]. The break was later attributed to electrical arcing through damaged insulation on the wire.

Other problems have occurred on some of the dozen or so space tether experiments. (Some of these involved nonconducting tethers connecting two orbiting bodies; through simple momentum exchange, the orbit of one body can be raised while the other is lowered.) Although the causes were identified and fixes were straightforward in each case, tether technology developed a tarnished reputation.

In a Finds-sponsored report, Carroll and Syromyatnikov expressed confidence that the Tethered Satellite System (TSS) problem will not doom Firefly. There are three fundamental design differences: Firefly's wire polarity is opposite that of the TSS; it uses only half the latter's voltage; and its wire is partially exposed and partially insulated, which, the report stated, "should generate far less volatiles [released gases] than the TSS wire did when the insulation was breached."

These design features, plus more careful fabrication of the tether, should greatly reduce the likelihood of a short-to-ground, which led to the TSS break and the loss of the Italian satellite.

Firefly's designers say that the tether could help shift Mir into an orbit closer to the international station's. Over a two-year period, the orbits would come to overlap. At that point, inter-station flights would become feasible. NASA space shuttles or Russian Soyuz or Progress vehicles could transfer thousands of kilograms of equipment and supplies. Some of Mir's science modules, mainly the Priroda earth observation complex, could also fly to the ISS, using their own rockets under autopilot control.

Rick Tumlinson, a U.S. space expert and an advocate of commercial space activities, has argued that the Firefly tether on Mir would actually benefit, rather than hinder, the ISS. He reckons that the tether would eliminate at least half the logistics support for Mir, making the station much less expensive to operate. In turn, that advantage would reduce the impact of prolonged Mir operations on the resources available for its international counterpart. What's more, if the tether works, it would be a boon to NASA's own ongoing efforts to apply the technology to the ISS--to meet its even more urgent need for altitude control.

The Threat from Mir Such arguments seem to have fallen on deaf ears at NASA. Tumlinson told IEEE Spectrum that some pro-NASA congressional staffers had been calling around various government agencies in Washington, trying to stall the license needed to export the tether to Russia. Under U.S. law, all space hardware is categorized as "munitions"--even Firefly, which is "just a reel of wire," Tumlinson said.

The idea that the tether is technically munitions may seem bizarre. But from the point of view of the U.S. space agency, a resurrected Mir is indeed a major threat.

Much of NASA administrator Dan Goldin's wrath has been focused on Energia. Long-standing NASA plans called for Energia to produce two Soyuz spaceships for use this year by the International Space Station. One was to send up the first long-term crew in October; the other was reserved for an all-Russian crew, which would be deployed in September in the event of a docking problem between the Russian-built service module (scheduled for launch this month) and the rest of the station. To help Energia complete the vehicles, NASA authorized $60 million in emergency funds last year.

Despite the U.S. agency's plans, the Russians have announced that two of the three manned Soyuz vehicles they will produce this year will go to Mir. One of them, Soyuz TM-30, was already used in April to send up a crew [Fig. 2]. A second Soyuz will take up a new crew in November.

"It is the director of the Energia company who proudly walked me through his plant and identified the tail numbers of two Progress and one Soyuz and thanked us for the support we gave so they could build them," Goldin told Congress in February. "It is the same person who without any consultation with NASA pulled those tail numbers to use to keep the Mir space station up." Tail numbers designate particular vehicles under construction.

Goldin called the reallocation of spacecraft to Mir "a major breach" and demanded that Energia return the $60 million. Russian officials said they would "do their best." Just to make sure, NASA associate administrator Joe Rothenberg announced he was "quarantining" a $7 million payment that had been planned for another project.

Meanwhile, at least one of the three unmanned Progress supply flights scheduled for the international station in 2000 has been reassigned to Mir. The Russians insist that Goldin approved the plan, but nobody at NASA claims to have heard of the agreement. Should the Mir reoccupation extend into 2001, the other two Progress vehicles will probably also be needed there.

Unrealistic plans Diverting supply drones from the ISS means more than just being unable to restock the astronauts with clean science gear and underwear. The Progress vehicles were to carry rocket propellant, to be used to counter the station's orbital decay due to air drag. Without the propellant, the station has been dropping dangerously close to the minimum safe altitude.

As a temporary fix, NASA's space shuttles can burn some propellant to make small orbital corrections in the ISS. This was in fact done in May, during the space shuttle Atlantis's repair mission. The agency is also building an interim control module that will carry large amounts of fuel. So far, though, the module hasn't been scheduled for launch.

No new work has been done on the ISS since late 1998, when NASA sent up the first two parts. Russia's Zvezda service module, the key life-support section, was supposed to follow within a few months, but the launch schedule continued to slip [Fig. 3]. Without it, the station remained uninhabited.

Finally, a "firm" date for the service module launch was set: 12 November 1999. NASA inspectors who visited the payload processing facility at the Baikonur Cosmodrome in Kazakhstan reported that the module was nearly complete--despite the fact that critical components, such as a rendezvous guidance radar and flight software for the German-built control computers, had not yet been delivered.

In the end, bad luck provided a face-saving way out. On 27 October, at Baikonur a Russian Proton rocket blew up, the same kind of rocket slated to carry the 20-ton service module into orbit. It was the second such failure in recent months. All further Proton launchings were then grounded.

Investigators identified a faulty batch of rocket engines, and commercial launchings resumed in February. But for Russian program flights, an entirely new set of engine turbopumps had to be manufactured. At press time, the service module was set to launch on 8 July.

Some Congressmen who listened to Goldin's laments in February were furious about the lack of progress. They ripped into the NASA administrator for years of self-delusion and poor judgment, and for relying on Russian participation in the international station. Dana Rohrabacher, chairman of the House Space and Aeronautics Subcommittee, thundered: "No other recent problem in our space program has cost the American people so dearly, both in money and lost opportunities. Nothing has been so destructive as the naive assumption that Russia's government would spend its limited resources to help us build the International Space Station."

In response, Goldin tried to put the best face on it: "I don't want to sound like Pollyanna but we will somehow, some way, get through this."

In the meantime, the ISS continues to orbit Earth. Occasionally, maneuvering rockets are fired to raise the orbit or to dodge pieces of space junk. Already, equipment has begun breaking down. The space shuttle crew that visited the station in May devoted almost their entire trip to repairs.

Limited resources Even if Firefly works and even with MirCorp support, Russia will have to scramble to build new spacecraft and launch vehicles. The government must also pay the salaries of key personnel required for human space operations. Retirements, deaths, and attrition to jobs with living wages have already thinned out the staff of the Mission Control Center near Moscow. Most of the space workers who remain have another family member with a "real job" elsewhere. If the service module goes up this month, that group is to be transferred from Mir operations to the ISS.

Another team, from the Khrunichev space factory in southcentral Moscow, is responsible for controlling the ISS's Zarya module. Although the manpower of the team has been severely strained, the factory has had a healthy cash flow from Proton rocket launch sales and can afford to hire enough specialists.

Elsewhere, the scientific infrastructure needed to plan and operate research on any space station has all but melted away. At the Institute for Biomedical Problems in Moscow, for example, medical experts who study human reactions to spaceflight have all taken other jobs.

In this environment of fiscal collapse, the Russian government agreed last year to let Energia seek private funding to keep Mir going. The government retained ownership of the station, but Energia would now be its operator--and fund-raiser. At first, Energia estimated that it needed more than 7 billion rubles (US $200 million) per year to operate Mir. But that figure gradually fell, as Energia's hunt for outside funding led to several embarrassing wild-goose chases. One British investor proved long on promises and short on cash. Negotiations with China and other countries were rumored but never substantiated. Some Western research teams expressed interest, but even combined, their offers failed to approach the funding required.

Last November, the Duma, Russia's parliament, allocated 1.5 billion rubles (about US $50 million) to keep Mir going, on condition that the money come out of profits from licensing Russian aerospace technology. It was a phantom allocation: licensing income totaled less than $1 million for all of 1999, and no actual cash was ever transferred to Energia. A charitable fund has also been soliciting donations from Russian citizens to keep Mir going. By the end of February, it had raised only 485 000 rubles, barely $15 000 at current exchange rates.

New lease on life

Through Tumlinson, Anderson met Jeffrey Manber, Energia's U.S. representative. Along the way, Chirinjeev Kathuria, president of the London-based New World Telecom LLC, also agreed to invest. Manber then arranged for the investors to meet with his Russian colleagues, and after several months of negotiations and mutual assessments, their new partnership was formalized.

On 17 February, representatives from MirCorp and Moscow's Energia Corp. gathered in London to sign a joint lease for the space station. "This isn't a Band-Aid to keep Mir alive," said Tumlinson. He likened NASA's role in exploring low-Earth orbit to that of Lewis and Clark, the early explorers of the United States, a role that has now ended. "This is a history-changing moment--it's the handoff of the frontier from governments to the people," he said.

Among MirCorp's plans is to set up an Internet portal on Mir, linked to Earth through relay satellites (which have yet to be launched). The portal would provide content for terrestrial Web sites. Color video of Earth from space would also be sold. In addition, MirCorp believes that individuals will pony up the $20 million for a one-week tourist trip to Mir (and also complete the requisite three months of training beforehand).

Andrew Eddy, who used to head ISS commercialization planning for the Canadian Space Agency, is MirCorp's senior vice president for business development. At the London signing, he downplayed the notion that Mir and ISS were competitors or even enemies. "It's very much a complementary initiative," he told reporters. "Once we start flying commercial clients on a regular basis to space, that will be very much to the benefit of the ISS partners." This is because, he continued, once the international space unit becomes operational, "there will be a pool of commercial clients who are used to flying in space, who understand the value of space activity to their business."

Despite the heroic efforts to save Mir and mollify NASA, though, one troubling fact remains: Mir is not, and never has been, a good platform for sophisticated research. Its power systems provide neither adequate wattage nor any guarantee of continuity and stability; the power needed to run the tether will further tax the available supply.

Another drawback is that the microgravity environment, critical for materials processing, is subject to frequent physical shocks and stresses due to station operations. And with the tether running out from Mir's airlock, the station's horizontal orientation in relation to Earth will be fixed. This means some of the station's scientific instruments, which must be pointed by turning the entire vehicle, will no longer be usable.

Nor would its tether-enhanced orbit really allow Mir to service other satellites. To experienced spaceflight experts, many of the promises from MirCorp seem naive.

Mir awakens

Naive or not, with corporate backing, Mir now looks as if it may go on for at least a few more years--particularly if the Firefly tether performs as ordered.

On 25 January, 136 metric tons of slumbering space station awoke. Responding to commands from Earth, the station restarted its main computer and powered up its precision pointing devices, the gyrodines. Eight days later, a Progress supply drone reached Mir, carrying rocket fuel meant originally to de-orbit the station; instead, the craft nudged it into a higher orbit. Over the course of a week, the station's altitude lifted from 315 km to 360 km, and later to 400 km.

The computer was then returned to hibernation until just before the launch of Soyuz TM-30, carrying cosmonauts Sergey Zalyotin and Aleksandr Kaleri. They reached Mir on 6 April. Another Progress vehicle arrived later in the month. After attending to a small but troublesome air leak and other housekeeping chores, Zalyotin and Kaleri departed Mir in mid-June.

The crew's visit to Mir ended a successful experiment in running the station remotely. Mir had been uninhabited since last September. Shortly before the last crew left, they hooked up a new high-reliability analog computer to Mir's autopilot. For the next six months, the computer ran a minimum level of equipment, mainly the radio link with Earth. It also kept Mir in a slow spin that oriented its solar arrays more or less toward the Sun, providing adequate power for the station's hibernation mode.

Over the summer, MirCorp will continue to try to recruit new investors and customers. The schedule calls for the next manned flight in November, followed soon after by delivery of the Firefly tether assembly aboard a supply drone and then installation and deployment of the tether.

At the London signing in February, Jeffrey Manber, the former Energia official and now MirCorp's president, was upbeat about the station's prospects: "We believe the story of the Mir space station and our efforts to keep it in orbit will be one of the great stories of the decade and perhaps of the century."

"The tragedy will not be if we fail," he added. "The tragedy would be if we didn't even try."

To Probe Further