Weather of Arabia - When people began exploring space in the 1960s, it cost more than $80,000 (adjusted for inflation) to put one pound of payload into low Earth orbit.
One of the main reasons behind this high cost was the need to build a new rocket and the cost per launch, but this situation began to change when Space X began to manufacture cheap and reusable rockets. Today, the company flies customer payloads to LEO at just $1,300 per pound.
This has made space available to scientists, startups, and tourists who could not have afforded it in the past, but the cheapest way to get into orbit may not be a rocket at all, but rather a space elevator.
The seeds for the idea of a space elevator were first sown by Russian scientist Konstantin Tsiolkovsky in 1895, when he visited the 1,000-foot-tall Eiffel Tower and published a paper addressing hypotheses for building a 22,000-mile-high structure.
This system would provide access to geostationary orbit, a height at which objects appear to remain stationary above the Earth's surface, but Tsiolkovsky acknowledged that no material could support the weight of such a tower.
In 1959, shortly after the launch of Sputnik, Russian engineer Yuri N. Artsutanov is a way around this problem: instead of building a space elevator from the ground up into space, you could start from the top.
specifically; He proposed putting a satellite into geostationary orbit and dropping a tether from it all the way to the Earth's equator. When the tether descends, the satellite will ascend. Once attached to the Earth's surface, the rope will stay taut, thanks to a combination of gravitational and centrifugal forces.
Then, we can send electrically assisted "climbers" up and down the rope to deliver payloads to any Earth orbit.
Credit: VectorMine / Adobe Stock
According to physicist Bradley Edwards, who researched this idea for NASA some 20 years ago, building a space elevator would cost about $10 billion and take 15 years, but once operational, sending a payload to any Earth orbit would cost about $100 per pound.
"Once you bring the cost down to near FedEx," Edwards said in an interview with Space.com in 2005, "it opens the doors for a lot of people, a lot of countries, a lot of companies to get into space."
In addition to the economic benefits, a space elevator would be much cleaner than using a rocket — there would be no fuel combustion, no harmful greenhouse gas emissions — and the new transportation system would not contribute to the same degree that expendable rockets could exacerbate the space debris problem.
Edwards wrote in his report to NASA that the technology needed to build a space elevator exists except for the material required to build the rope, which needs to be light but strong enough to withstand all the enormous forces acting on it.
The good news, according to the report, is that the ideal material - extremely strong and extremely small carbon nanotubes - will be available in just two years.
"The shell is not strong enough, nor is Kevlar, carbon fiber, spider silk, or any material other than carbon nanotubes," Edwards wrote. "Fortunately for us, carbon nanotube research is currently very active, and is rapidly progressing to commercial production."
Unfortunately, he miscalculated just how difficult it would be to manufacture carbon nanotubes — until now, no one had managed to produce a tube longer than 21 inches.
Further research into this material showed that it tends to tear under excessive stress, which means that even if we could manufacture carbon nanotubes to the required lengths, they would still be prone to breakage, which not only destroys the space elevator, but poses a threat to life on Earth.
Carbon nanotubes may have been the first candidate as a binding material for space elevators, but there are other options, including graphene, a two-dimensional form of carbon that's actually easier to scale than nanotubes (although it's still not easy).
Contrary to Edwards' report, Johns Hopkins researchers Sean San and Dan Popescu say that Kevlar fibers can work — we just need to constantly repair the rope, in the same way the human body is constantly repairing its tendons.
"Using sensors and smart software, it is possible to mathematically model the entire rope to predict when, where and how the fibers will break," the researchers wrote in a 2018 article in the journal Ion.
"When damage occurs, controlled fast ascents and descent vehicles will navigate along the rope in their stead, adjusting the rate of maintenance and repair as needed - mimicking the sensitivity of biological processes," the researchers continued.
Astronomers from the University of Cambridge and Columbia University also think that Kevlar fibers might be suitable for a space elevator - if we built it from the Moon instead of from Earth.
This wouldn't eliminate the need for rockets to reach Earth's orbit, but it would be a cheaper way to get to the moon. The force acting on a lunar space elevator may not be as strong as that acting on a space elevator extending from Earth's surface, according to the researchers, opening up more choices for tether materials.
Meanwhile, some Chinese researchers aren't giving up on the idea of using carbon nanotubes for a space elevator — in 2018, a team from Tsinghua University revealed that they had developed nanotubes that they say are strong enough to be a rope.
Researchers are still working on the issue of expanding nanotube production, but in 2021, China's state-owned news agency (Xinhua) released a video depicting a concept under development called the Sky Ladder, which would consist of space elevators above the Earth and the Moon.
After riding the space elevator on Earth, the capsule will fly to a space station linked to the rope of the space elevator on the Moon. If they can complete this project - which is a huge feat - China expects the Sky Ladder could reduce the cost of sending people and cargo to the Moon by 96%.
In the 120 years since Tsiolkovsky looked at the Eiffel Tower and thought of something much larger, significant progress has been made in developing materials with the properties required for a space elevator. At this point, it seems likely that we will one day have a material that can be made on the scale called for by rope - but by then, the need for a space elevator may have vanished.
Many aerospace companies are making progress developing reusable rockets themselves, and when these rockets join the market with SpaceX, the competition can drive down launch prices even further.
California-based SpinLaunch, on the other hand, is developing a giant thrust center to launch payloads into space, which much smaller rockets can propel into orbit. If successful (which is also uncertain), the company says the system will reduce the amount of fuel required to reach orbit by 70 percent.
Even if the "SpinLaunch" plan does not materialize, there are several teams working to develop green rocket fuels that produce very little (or no) harmful emissions. More work is needed to effectively scale its production, but overcoming this hurdle will be much easier than building a 22,000-mile elevator to space.
Source: freethink
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