Like magnet-powered elevators, for instance. This would be a serious problem if we want our tower to contain residences and offices. But before we go selling our elevator ad space, we need to see if it would be safe for us to go up that high in the first place. And our space tower would be 11 times taller than that.
It would take a lot of pressure to pump water up so high. It would need hundreds of water reservoirs located at different levels through the building.
These water reservoirs would be filled in sequence, with each one being used to fill the one above it, all the way to the top. If the residences were to use as much water as the residences in the Burj Khalifa per day, we estimate that our space tower would use about 13 Olympic size swimming pools of water per day.
And even if we solved all those challenges, there would still be one underlying issue that could inevitably sink the whole project. How big is the Sun compared to the Earth? Imagine you were able to shrink the Sun to the size of a basketball. At that point, the Earth would be reduced to the Life on Mars might be like this. And if you happen to go outside, it would be in your big As commonly conceived today, a space elevator would consist of motorized elevator pods that are powered up and down a ground-to-space tether.
The tether would stretch from a spaceport at the equator to a space station in geosynchronous orbit overhead. It will simulate on a small scale the conditions that the components of such a system would encounter. The steel tether to be used in the experiment is too heavy to be used as a full-sized space elevator, which must, of course, extend for tens of thousands of miles.
The big difference comes from the centrifugal forces. But the moon-based spaceline would orbit just once a month—a much slower rate with correspondingly lower forces. In extending from the moon to Earth, the spaceline would pass through a region of space where terrestrial and lunar gravity cancel each other out.
This region, known as a Lagrange point, becomes a central feature of a spaceline. Beneath it, closer to Earth, gravity pulls the cable toward the planet.
But above it, closer to the moon, gravity pulls the cable toward the lunar surface. But the cable need not stretch all the way to be useful.
They go on to suggest that a proof-of-principle device made from a cable about the thickness of a pencil lead could be dangled from the moon at a cost measured in billions of dollars. The savings would be huge. And it would open up an entirely new region of space to exploration—the Lagrange point.
This is of interest because both gravity and the gravity gradient in this region is zero, making it much safer for construction projects. By contrast, the gravity gradient in low Earth orbit causes orbits to be much less stable. Neither is there any significant debris in this region.
Beyond that, we can imagine space-based megastructures many kilometers in size, powered by solar energy, perhaps encompassing whole planets or even stars. In recent years, engineers have been able to build on grander scales thanks to the strength and reliability of substances such as novel steel alloys. But as we enter the realm of megastructures—those of 1, km or more in dimension—maintaining safety and structural integrity has become a fiendish challenge. It turns out that biological design , equipped with around 3.
Before the age of materials science, engineers had to look to nature for creative tricks to help them overcome the restrictions of their materials.
Classical civilizations, for example, souped their war machines with twisted tendons made from animal hides, which could extend and snap back to launch projectiles at the enemy. But then substances such as steel and concrete arrived, and became successively tougher and lighter.
Once structures turn into megastructures, though, calculations show that this risk-averse approach places a cap on their size. Megastructures necessarily push materials to their limits, and remove the luxury of weathering comfortable levels of stress.
However, neither the bones nor tendons in our bodies enjoy this luxury.
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