It’s not clear what motivated the reappearance of the Space Elevator ambitions of the highly accomplished Japanese engineering firm Obayashi Corporation on Australia’s ABC News today.
A desire to provide the terrorism terrified masses with a new distraction? Or stop us worrying about the federal budget, or the dismal and unprofessional quality of refereeing in the NRL?
Not that the space elevator isn’t a terrific story. But everything that is in the ABC item was announced by Obayashi (株式会社大林組 ) on 23 February 2012, and given something of a reality check not long after, as in this example.
The theoretical basis for space elevators is sound, as is the use of surplus atom bombs to propel an expedition to the next nearest star proxima centauri in only a few lifetimes. It’s just the practical details that tend to niggle.
With the right materials, which so far don’t exist except in theory, various types of ultra fabulous hi-tech elevators could lift objects to astonishing altitudes, such as to a mean distance from the surface of the equator at 35,786 kilometres, where anything pushed out the hatch would be in the geosynchronous orbit used by many communications and earth monitoring stations.
Go out further (Obayashi is proposing to go to a distance of around 90,000 kms) and objects could be flung away by the radial velocity of the end of the shaft, and other forces, on a variety of transfer orbits to the moon, the mineral rich asteroids, the planets and their own families of moons.
All at a fraction of the cost of conventional rocketry, once we can work out how to really do it, and with the materials, electromagnetic fields, or other accoutrements, needed to make it work.
Which isn’t to knock the space elevator concept, which no doubt will in a future lifetime be built, unless an even better idea with even more appealing characteristics emerges.
The mathematical implications of a space elevator are more than interesting. When tall structures are built on earth the variation of the value of the force of gravity between the top floor and the basement isn’t top of any list of design constraints, but given that gravity becomes weaker, while the lateral or tortional forces on a tethered structure rise, well, astronomically, the higher you go, then new sets of engineering disciplines become imperative.
Today’s geosynchronous satellites aren’t tethered. They wander around within certain limits from their theoretical spots above the equator. The tug of the earth on a supposedly locked geosynchronous satellite depends on the tidal pulses of oceans and the differential motions of the various mantles or layers of semi fluid material in the planet’s interior, and even the significant inputs of lunar and solar gravity as our moon and sun move closer to or further from the earth through orbital variations.
Translate those variables into waves of compression and relaxation that move up and down an incredibly thin and long object and you are in a place where engineering hasn’t gone.
There are enormous exchanges of cosmic and solar energy between the earth and space. Might a space elevator become some sort of lightning rod? Science needs to know with precision before something unexpected comes along to zap us.
The structure itself would have to be space junk proof, in fact, might only become feasible after the detritus of the earlier rocket ages has been cleaned up, long after most of us have been harvested.
The rocket age will eventually be replaced by something else. For all of the problems with space elevator stories, even ones that seem recycled, they may, one day, come true.