Planetary Ingress and Egress: The Space Elevator

We must find a better way to move ourselves, and our stuff, into space. Rocket boosters are messy, expensive, dangerous and wasteful.

The potential solutions include space elevators, high-altitude rail guns, and gravity-modification technology. There are engineering problems with each–including the need for certain breakthroughs (some more astounding than others) and the commitment of necessary resources. Following is a brief discussion of the first option.

The Space Elevator Solution

This illustration by artist Pat Rawling shows the concept of a space elevator as viewed from the geostationary transfer station looking down the length of the elevator towards the Earth.

The concept of a space elevator has been around now for a long time. It’s a structure that stretches from the ground into space, with every part of the structure moving with the Earth in essentially geostationary orbit. People and things could be lifted up its length and into space relatively cheaply, with the true cost of the structure being the up-front design and construction. Also, escape velocity is automatic for anything leaving the structure from above the geostationary point.

The notion is a dream, and it’s easy to imagine a space-faring civilization engineering such elevators in a ring of spokes around the equator of each of its civilized worlds. It is being studied at NASA’s Marshall Space Flight Center’s Advanced Projects Office. Present proposals envision a structure extending from Earth’s surface through geostationary orbit (for a center of mass at about 35,786 km) with a cable tethered to the top. Electromagnetic vehicles would travel along the cable as the structure provides mass transport for people, payloads and power between space and Earth. Advancements in materials research helps improve the potential of a workable space elevator.

But the idea is also crazy dangerous (should something go wrong), enormously expensive to build with present technology, and a commitment of global resources that exceeds anything that has ever been done. Will it be done? Yes, some day. Anytime soon? NASA’s plans seem to expect such structures near the end of the 21st Century. But that is probably optimistic, at least for Earth, unless some substantial breakthroughs occur that improve the cost, effectiveness and safety of the project.

It’s perhaps far more likely that we’ll see the first space elevator on the Moon or Mars. Both locales are smaller than Earth with less atmosphere, making the engineering easier and the resource commitment less. It would be easiest on the Moon. But whether it’s cost effective on the Moon is yet to be seen. It’s pretty easy to get into orbit from the moon, and there are cheaper structures that might be more practical–like electromagnetic rails that shoot cargo and passengers up a ramp and into orbit. As is the case with all or most transport technologies, it will depend on the cost factors in play at the time the location is developed. (The Moon will be humanity’s most valuable source of raw materials for a long time once we step into space on a more permanent basis. Until then, it’s exploitation is not quite worth the startup cost.)

Mars is probably perfect for a space-elevator system. It’s gravity makes liftoff expensive using rocket boosters, and its atmosphere, which will thicken once we start making it a home, takes management. The martian moons, Deimos and Phobos, will have to be considered, and might become part of the system. But we have a lot of wrangling ahead of us about Mars and what can be done with it before we seriously plan a permanent structure to manage transport up and down its gravity well.

Bottom line: Let’s keep working on it. We can do it off world first, if our expansion proceeds. And unless a better idea congeals, when the cost of building an Earth elevator approaches shouting range of reasonable, let’s make a commitment and start building the next wonder of the world.

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