Brian Wang has a recent article updating the quest of China’s Broad Group to build the world’s highest tower of 838 metres, over a time period of only 6 months. It looks as if the Sky City project may actually be built.
In one building, there will be accommodation for 4450 families in apartments ranging from 645 SF to 5,000 SF, 250 hotel rooms, 100,000 SF of school, hospital and office space, totaling over eleven million square feet. The building footprint is only 10% of the site; the rest is open parkland.
If you would rather walk rather than wait for one of the 92 elevators, there is six mile long ramp running from the first to the 170th floor. Beside the ramp are 56 different 30 foot high courtyards used for basketball, tennis, swimming, theatres, and 930,000 square feet of interior vertical organic farms.
The building is designed to be earthquake resistant to Magnitude 9, and to a 3 hour fire resistance rating, provided by ceramics installed around the structure. 16,000 part time and 3,000 full time workers will prefabricate the building for four months and assemble on site in three months. The Broad system is based on prefabricated floor panels that ship with everything need to go 3D packed along with it, so they are not shipping a lot of air. It all just bolts together. BSC claims that by building this way, they eliminate construction waste, lost time managing trades, keep tight cost control and can build at a cost 50% to 60% less than conventional construction.
An 800 metre tower is roughly one half mile tall. But there is no reason to believe that Zhang Yue will stop there. He already has plans to build a 2 km tower.
A mile high tower expanded upward from the basic plans of the Burj Khalifa would have a footprint of about 5 acres, and house 40,000 people in luxury. Source Respected futurist Josh Hall believes that the entire population of the Earth could fit inside the area of the US state of Montana — locating just one mile-high tower in the middle of each square mile of the state.
How High Can You Build a Skyscraper?
The mile-high skyscraper makes a little more sense to build now than it did when Frank Lloyd Wright designed one nearly 60 years ago. Wright imagined, on the fringes of Chicago, a habitable 528-story sundial called the Illinois. That idea wasn’t buildable then; its successor would still be risky, financially ruinous, slow to construct, and inefficient to operate.
… I asked William Baker, the SOM structure guru who figured out how to make the Burj Khalifa stay up, how he would respond if a hypothetical developer with limitless resources came to him and said: Okay, time to quit screwing around with ten stories there and 100 feet there. Let’s build the mile-high tower.
“Yup,” he answered. “Okay.” (Baker is from Missouri, and he is frugal with words.)
“How about a mile and a quarter?” I pressed.
“Yeah, we’d figure it out.”
And at what point do you stop being able to figure it out?
“I’m not sure. A mile would be twice the Burj. For now, let’s double what we have. Then we can figure out how to double it again.” So, two miles, then? __ Justin Davidson
One of the biggest problems with a 2 mile tower may be the elevators:
The biggest problem, though? Elevators. Technologically, designers and engineers have hit the ceiling, and we have no solution yet. The issue is that cables longer than 600m are simply too heavy to winch. So, until we can solve this, the dream of the 5km-high megatower will remain a fantasy. __ BBC
“The predominant problem is in the elevator and transportation system,” says Adrian Smith, the architect behind the current tallest building in the world and the one that will soon outrank it, the kilometer-tall Kingdom Tower in Jeddah.
But in terms of structural limitations, the ultimate expert is likely William Baker. He’s the top structural engineer at Skidmore, Owings and Merrill and he worked with Smith on the Burj Khalifa, designing the system that allowed it to rise so high. That system, known as the buttressed core, is a kind of three-winged spear that allows stability, viably usable space (as in not buried deeply and darkly inside a massively wide building) and limited loss of space for structural elements. __ CityLab
Other ideas for overcoming the one mile height limit are presented at the link above.
Assuming the problems with the vertical transport mechanism is solved, Josh Hall has another suggestion: Build a series of 100 km towers and place a 300 km long horizontal “beam” across the top of the towers.
Build a structure 100 kilometers tall and 300 kilometers long. Put a linear induction (or other electromagnetic) motor along the top. An elevator goes straight up 100 kilometers to the starting end. Payloads are then accelerated horizontally into orbit with an acceleration of only 10 G’s (which appropriately cushioned humans can stand for the 80 seconds required). This hybrid approach overcomes the drawbacks of both the typical orbital tower schemes (it’s less than 1% the height of a skyhook) and electrolaunch ones (air resistance at 100 km is a million times less than at sea level).
Halfway to Anywhere
It might be possible to design the accelerator to allow a mass/ acceleration tradeoff, i.e. to launch 10 tonnes at 10 G’s or 1 tonne at 30 G’s. Freight that can withstand 20 G’s can be launched at escape velocity, and sent more or less directly to the moon. 30 G’s puts it into a (Hohmann) transfer orbit to Venus or Mars.
Once the tower is in place, it would be practical to launch other accelerators (in pieces) to orbit. An orbital accelerator would have the advantage of low rendezvous velocities, and the disadvantage of needing to fire something backwards periodically to maintain its orbit. It could be much longer than the tower and thus could form a second stage capable of launching humans on transplanetary trajectories at survivable accelerations. __ Josh Hall
There should be plenty of living space inside the many 100 km support towers to house one fourth of the people currently living on Earth. Four of these structures dispersed among the wealthy populations of North America, Europe, East Asia, and South Asia / Arabia, should provide housing for everyone on the planet. But with cheap space launch readily available for both cargo and colonists / space miners, we may see large numbers leaving the home planet for the endless space and resources beyond.
Regardless, it should be clear that using very tall towers, most of this planet’s urban populations could be housed using only a very small footprint of actual land. The technical details remain to be solved, but the potential should be obvious.
Another concept for building a tall tower uses helium-filled modules such as what Neil Craig describes. Clever use of lighter-than-air modules might provide a number of approaches to orbital space, including the 3-stage system described in this PDF document.