December 1, 2008
The Space Shuttle Endeavour safely landed at Edwards yesterday, completing a highly successful 16-day mission to the International Space Station (ISS), which celebrated a decade of continuous operation last week. It’s common in my business of planetary science to complain about the ISS, how it sucks up money that should be used for scientific exploration, and numerous other sins. Today, I write of its benefits and how it is relevant to our expansion into the Solar System.
The idea of a space station is very old; Wernher von Braun made it one of the first pieces of a broadly based transport system in space in his original Collier’s articles. In its original incarnation, a manned space station would do many jobs – Earth observation, including weather forecasting, communications relay, astronomy, a servicing port for trips beyond low Earth orbit. In fact, almost all of these tasks came to pass, but not at ISS. We watch and monitor the Earth with robotic spacecraft. An unmanned communications satellite (comsat) network 22,000 miles above the Earth acts as a relay network that ties the entire Earth together. The Hubble Space Telescope observes the heavens with crystal clarity. Many of the jobs von Braun envisioned for a space station are done today, but by robotic satellites, not humans at ISS.
What about the station’s role as a jumping off point for voyages beyond Earth? There hangs an interesting tale. When NASA first began thinking about lunar bases in the early 1980s, Space Station Freedom (as it was then called) served exactly that role. Station would be a transportation hub between the Moon and other destinations in cislunar space, such as geosynchronous orbit (where comsats reside). The Shuttle would deliver people and goods to the station in low Earth orbit and from there, they would journey to the Moon and beyond.
But Space Station changed. To maintain political support for the program, it morphed from Space Station Freedom into the International Space Station, with significant participation by Russia. For the Russians to be able to access station from their launch facilities in Kazakhstan, the inclination from the equator of the plane of its orbit changed from 28 degrees to 52 degrees. This new inclination enabled station to fly over 80% of the globe (good for Earth studies) but made it more difficult for Shuttle to reach (lowering the total mass Shuttle could bring up) and making the station much less attractive as a staging node for voyages beyond LEO.
These consequences were known at the time and as no future human missions were planned beyond LEO for the foreseeable future, made operational sense of a sort. Now we find ourselves with a space station, but apparently one not optimally placed to support our movement into the solar system. This is one of the many criticisms of station – that it is essentially a dead end and cannot be used as a “jumping off point” for future missions.
But I contend that ISS is useful for future lunar and planetary exploration. For one thing, building and operating a million-pound spacecraft for over a decade has surely taught us something about spacefaring. One of the most remarkable facts about ISS is that it went from drawing board (more accurately, from computer-aided design bits) to working hardware in space, without numerous prototypes and precursors, and it worked the first time it was turned on. By any standard, that is a remarkable achievement. We have learned how to assemble and operate complex spacecraft in orbit, in many cases solving deployment problems and coaxing balky equipment into operation, as exemplified by the recent experience of Don Pettit and Mike Fincke with the renowned urine conversion machine. Assembling complex machines and making them work in space is a key skill of any spacefaring society. Building and operating ISS over the last decade has taught us much about that skill.
The station could be made even more important and relevant to future operations in space. A key requirement of routine operations in cislunar space is the ability to manage, handle and transfer rocket fuel, particularly the difficult to manage cryogenic liquid oxygen and hydrogen. We could begin to acquire real experience working with these materials at ISS – transfer a quantity of water, crack it into its component hydrogen and oxygen using solar-generated electricity on orbit, and experiment with different methods of handling, conversion and storage of these materials. None of this requires a new module, but some specialized equipment could allow us to experiment with cryogenic fuel in microgravity, mastering a skill of vital importance to future operations in space and on the Moon.
A decade of building the ISS has taught us much about real spaceflight and the experience gained will be vital to future, long duration human missions. We should take advantage of this asset to explore further the technologies and techniques we will need to create a true spacefaring infrastructure, one of von Braun’s original goals of an orbiting space station.
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