A year or so before The End, the process will begin.
At some point in the not too distant future, a multi-national project, costing tens of billions of dollars, employing the efforts of hundreds of thousands of people and responsible for cementing the foes of the past into the allies of the future will come screaming back to Earth in an impressive display of fireworks and thunder. The International Space Station – whose first elements were launched way back in November 1998 – is presently the largest artificial satellite ever placed into space by human hands. Weighing nearly a million pounds, it extends 240 feet long from the forward end of its Harmony node to the aft port of its Zvezda module and a full football field (more than 356 feet) across the width of its expansive solar arrays and trusses. Cost estimates for this astonishing accomplishment, the greatest engineering triumph in human history, are many and varied, but as a tool for bringing us closer together as a species, the station is unparalleled.
Precisely when the ISS will reach the end of its life is unclear, but the strategic planning will move into high gear at least a year ahead of the event. The first objective, according to ISS Program Manager Michael Suffredini in the ‘ISS End-of-Life Disposal Plan’, submitted to the Aerospace Safety Advisory Panel in October 2010, will be to ensure that required propellant reserves to execute a safe re-entry into the atmosphere are available, to configure the station in a manner which will ensure its controllability during descent and to dock whatever vehicles are needed to effect the de-orbit process. Then, four days before The End, the station’s perigee – the lowest point of its orbit, currently around 250 miles – will be propulsively lowered to the “minimum controllable altitude”. The final coup de grâce will come with a series of engine ‘burns’ from the de-orbit vehicle, which will cause the ISS to “drop as deep as possible into the atmosphere in one orbit” and ensure the effective capture and destruction in the atmosphere of “high-speed, high-Ballistic Number fragments”.
Fragments. This single word chills the spine of many who have invested their lives into the ISS and who have seen that investment bear incredible fruit: a truly international, multi-cultural outpost, permanently occupied for more than 12 years to date and resplendent in terms of technology and aesthetic beauty. That ‘international’ element is illustrated by the six souls who reside there as you read this article: a female commander of Indian and Slovenian ancestry, a Japanese engineer, a former Shuttle pilot and three Russians from regions as ethnically diverse as Belarus and Ukraine in the west to Chita in the east. And the very fact that none of these names or nationalities raised as much as an eyebrow when they roared into orbit is testament to the fact that flying representatives of many nations and cultures and religions – and both genders, too – is no longer the exclusive realm of the elite, but is becoming increasingly commonplace.
The craft which will be responsible for the final ‘execution’ of the ISS has yet to be formally decided, although current consensus favours a series of four Russian Progress resupply freighters, probably docked ‘radially’, their engines thrusting forward, aft, zenith and nadir, to “provide additional delta-V and pitch control” and “achieve tactical phasing” for entry interface. Over the final four days of the ISS’ life, by now long since de-crewed, the Progresses will fire together for 30 feet per second, per day, to set up the final phasing and orbit-shaping properties required for a safe and successful destructive dive into the atmosphere. At one stage, it was hoped that the Automated Transfer Vehicle might play a role in the de-orbit plan, but in April 2012 the European Space Agency announced that the fifth ATV – currently scheduled for launch in two years’ time – will be the last in the series. This is a pity, but Progress has a long-proven track record and is deemed the simplest and most cost-efficient option, with the greatest margin for success.
At present, the United States government has funded the ISS project until 2020, which means that only a decade will pass between the installation of the outpost’s final US modules and their decommissioning and destruction. However, two years ago, the heads of the involved space agencies – NASA, ESA, the Russian Space Agency, the Japanese Aerospace Exploration Agency and the Canadian Space Agency – met in Tokyo to discuss an extension as far as 2028, a full three decades after the launch of the station’s first element. In a joint statement, the partners “reaffirmed the importance of full exploitation of the station’s scientific, engineering, utilisation and education potential”, noted that there were “no identified technical constraints to continuing ISS operations beyond the current planning horizon of 2015 to at least 2020” and, moreover, that “the partnership is currently working to certify on-orbit elements through 2028”.
Meeting this target will be challenging, though far from impossible. Earlier in 2010, Michael Suffredini had already reported that he felt comfortable that the ISS was structurally capable of supporting a human presence until at least the early 2020s. Analyses of the factors relevant to an extension – including the procurement of spare parts and facility upgrades – are expected to be completed by all ISS partners no later than 2016. Options to seek ways of reducing the annual cost of station operations were also discussed. In July 2010, Simonetta di Pippo, ESA’s station director, mentioned the possibility of new water-regeneration systems to reduce the need to launch fresh supplies, as well as increasing the cargo capacity of the ATV and its successors.
Yet the ISS will come to an end someday…and before that day comes, the Russians have already hinted that they intend to undock their complement of modules and commission them as an entirely new research facility, called the ‘Orbital Piloted Assembly and Experiment Complex (‘OPSEK’ in Cyrillic). A pair of Progresses would transfer the complex – which will probably comprise the Zvezda service module, both the Poisk and Rassvet mini-research modules, the long-delayed (and still unlaunched) Nauka multi-purpose module, together with a possible six-port node and a pair of science power modules – from the ISS’ present 51.6-degree inclination into an orbit of about 70 degrees. In June 2009, it was announced that the Russians will use the new complex to assemble components for future interplanetary missions, possibly involving not only the Moon and Mars but even Saturn. Notably, one of its key functions would be to provide “medical and biological conditions required for the rehabilitation of interplanetary expedition crews after their return to Earth orbit”.
For now, the outpost’s future is beginning to brighten. In the wake of the retirement of the Shuttle fleet, SpaceX last month commenced the first of a dozen planned cargo delivery runs by its Dragon craft and Orbital Sciences is expected to follow suit with its Cygnus vehicle early in 2013. Russian Progresses currently fly four to five times per annum and, dovetailed into the manifest, are six-month-long visits by the European ATV and month-long deliveries from the Japanese H-II Transfer Vehicle. A ‘full’ crew of six inhabits the station for approximately ten months of each year – with occasional reductions from six to three crew members during ‘indirect’ Soyuz changeovers – and plans are expected to be announced in the next few weeks for a year-long US/Russian expedition in 2015.
The latter offers a greater indication than ever before that the station is now on the cusp of being utilised, not only for its scientific potential, but also for its potential as a testbed for demonstrating the technologies and establishing the life science baseline data needed for longer and more difficult missions beyond Earth orbit. Admittedly, missions as far afield as Saturn, with humans, seem a little on the wild side, in view of the current global economic climate and the paltry financial allocations of space agencies around the world.
However, the talk of utilising the ISS beyond 2020 for more than basic scientific investigation is heartening. Last December, Boeing authored a plan to use already-built ISS hardware – including a structural test article at the Kennedy Space Center which could be reconfigured as Node 4 – and place them into one of the Earth-Moon Libration (EML) points as an ‘Exploration Gateway’ to enable future lunar or Mars expeditions. Moreover, the recent re-election of President Obama to a second term in office has provoked a flurry of speculation that NASA will shortly make a major announcement about its future plans for both the station and exploration beyond Earth orbit.Missions » ISS »