Have you ever wondered just how tall we could build something? Whilst we’ve had modern skyscrapers for almost 2 centuries now advances in material science and building construction techniques means that the helm of the tallest building never lasts for long. The Burj Khalifa currently stands as the world’s tallest structure with it’s tip tickling 830m tall. That’s pretty impressive but it definitely makes you wonder just how far we could push it, which this video explores in depth:
He hits on some good points and of course the tallest structure ends up being a space elevator. I’ve written about them in the past hitting on some of the same issues that the video mentions but interestingly there’s actually a couple other potential structures that could achieve great heights without having to go to the extremes of the space elevator. They’re still not your traditional building however, but they’re quite fascinating in their own right.
One such structure is called a Space Fountain. Instead of relying on a rigid structure like a normal building or tensile strength like in the space elevator the space fountain instead relies on a stream of particles shot through it at high speed to keep itself erect. Such a system need not be set at a geostationary point nor does the orbital end have to stretch all the way past geosynchronous orbit for it to be able to work. Of course the main issue with it is the high energy requirement and the rather catastrophic consequences should the particle containment system fail. Still it’s quite a novel idea, even if it will likely never see the light of day.
Another idea that’s similar to the space fountain is the Orbital Ring concept. In essence you’d wrap the earth with a giant steel cable which would then be accelerated to slightly above orbital speed. Then you’d dangle tethers from it back down to earth, much like you would do with a space elevator. The really cool thing about this kind of structure is that you could also place such stations in geosynchronous orbit by causing the ring to precess around the earth. This could be used quite effectively to make things like GPS and satellite communications better due to the reduced distance. Again its somewhat fanciful due to the high capital cost of setting it up (getting 18,000 tonnes into orbit ain’t cheap) but it is another clever way of building something tall that doesn’t go the full space elevator route.
You know for all the writing on space I’ve done over the past few years I’ve never once mentioned one of the most intriguing ideas in this field: the space elevator. I’m not sure why I avoided it to be honest as the idea has good foundations in science and manages to generate a whole lot of interesting debate whenever it’s mentioned. It’s not like I haven’t talked about completely theoretical space technologies before either so today I’d like to introduce you to the space elevator concept and go over why it might (and might not) be the technology we should be pursuing in order to fundamentally change the way we access space.
At it’s core the space elevator is a simple idea. You see there’s an orbit around the earth where a satellite will, for all intents and purposes, remain steady over a point on the earth. Currently this space is filled with GPS and meteorological satellites since their mostly fixed position is highly desirable for such applications. These are referred to as geostationary orbits and they all lie directly above the earth’s equator. Theoretically then if you were to put a satellite at one of these orbits and then connect it directly to the place on earth which it hovers over you could then gain access to space by simply running up the cable, a damn sight more elegant than strapping everything to the top of a giant explosion and pointing it upwards.
This idea has numerous advantages over chemical rockets, not least of which is the significant reduction in cost in getting payloads into orbit. Most designs have the runners, the vehicles which “run” up the cable, being powered either directly from the cable itself or by power beaming technologies. This means that you’re not taking all your fuel up with you making the potential payloads much cheaper to deliver into orbit as you can use electricity generated on the ground. The end in geostationary orbit could also be used as a launch platform, enabling much bigger spacecraft to be built and launched into our solar system. It sounds like the perfect solution to many of the challenges behind getting into space but of course there’s always a catch.
The biggest challenge that a space elevator faces is finding a material capable of anchoring a satellite to the earth. Such a material needs to be light with an extremely high tensile strength, far beyond that of any metal or fiber that’s currently available. It also has be manufactured in great lengths on the order of 36000KMs to be able to reach the required height for geostationary orbits. To date the only material that has all these characteristics is carbon nanotubes which match the required strength and weight almost perfectly with the added benefit of being able to conduct electricity. However the inability to make them in lengths any greater than a few centimeters means that until mass fabrication method is discovered carbon nanotubes are unfortunately a pipe dream effectively killing any space elevator before it gets off the ground.
There are also many other factors that need to be considered before a working space elevator can be created. Whilst there’s little danger from the cable breaking to people on the ground (it would most likely flutter harmlessly down to earth) both the runners and the station need considerable contingency systems to be able to deal with this event. Also for payloads that require a non-geostationary orbit (I.E. low/high earth orbits) a space elevator does not provide any velocity to the craft, meaning to achieve a proper orbit you still need to hit Mach 25 unless you want to come back down to earth in a hurry. This is much easier when you’re in space, but it still means that you have to carry up significant amounts of fuel if that’s you’re goal.
Despite these problems however a space elevator is still an extremely attractive possibility and since most of the required technology is already available the idea is now starting to gain traction. Japan is planning to allocate some $10 billion into building the world’s first space elevator and whilst I’d forgive you for not taking them seriously Japan does in fact have a very good space program, they even run supply missions to the International Space Station. Such a commitment to the idea means that the space elevator has a strong possibility of becoming real in the next couple decades, and the flow on effects will have global implications.
Space was once only a realm for dreamers, then super governments and then finally the mega-rich. However the continued revolutions in this industry are driving the cost of space access down to unprecedented levels, serving to make space travel as commonplace as airline travel is today. It’s not going to happen today or in the next 10 years even, but we’re are on the cusp of a fundamental change to the world around us and it is on the back of a space elevator that we shall achieve it.