Imagine a long tether linking Earth to space that could launch us to orbit at a fraction of the cost and slingshot us to other worlds at record speed.

That's the basic idea behind a space elevator.

Instead of taking six to eight months to reach Mars, scientists have estimated a space elevator could get us there in three to four months or even as quickly as 40 days.

The concept of space elevators isn't new, but engineering such a structure would be no easy feat, and many other issues besides technology stand in the way.

That's why the ambition to seriously build one is fairly recent.

The Japan-based company Obayashi Corporation thinks it has the expertise.

Japan aims to build a space elevator by 2050

Known for constructing the world's tallest tower, the Tokyo Skytree, Obayashi Corporation announced in 2012 that it would reach even loftier heights with its own space elevator.

In a report that same year, the company said it would begin construction on the US$100-billion project by 2025 and could start operations as early as 2050.

We checked in with Yoji Ishikawa, who wrote the report and is part of the company's future technology creation department, to see how the project is progressing ahead of 2025.

While Ishikawa said the company likely won't start construction next year, it is currently "engaged in research and development, rough design, partnership building, and promotion," he told Business Insider.

Some have doubted such a structure is even possible.

"It's been sort of a kooky idea," said Christian Johnson, who published a report on space elevators last year in the peer-reviewed Journal of Science Policy & Governance.

"That said, there are some people who are real scientists who are really on board with this and really want to make it happen," Johnson said.

A cheaper route to space

Launching humans and objects into space on rockets is extremely expensive. For example, NASA has estimated its four Artemis moon missions will cost $4.1 billion per launch.

The reason is something called the rocket equation. It takes a lot of fuel to get to space, but the fuel is heavy, which increases the amount of fuel you need. "And so you see the kind of vicious cycle there," Johnson said.

With a space elevator, you don't need rockets or fuel.

According to some designs, space elevators would shuttle cargo to orbit on electromagnetic vehicles called climbers. These climbers could be remotely powered – like through solar power or microwaves – eliminating the need for on-board fuel.

In his report for the Obayashi Corporation, Ishikawa wrote that this type of space elevator could help drop the cost of moving goods to space to $57 per pound. Other estimates for space elevators in general have put the price at $227 per pound.

Even SpaceX's Falcon 9, which, at around $1,227 per pound, is one of the cheaper rockets to launch, is still about five times as expensive as the higher cost estimates for space elevators.

There are other benefits besides cost, too.

There's no danger of a rocket exploding, and the climbers could be zero-emission vehicles, Johnson said. At a relatively leisurely pace of 124 miles per hour, the Obayashi Corporation's climbers would travel slower than rockets with fewer vibrations, which is good for sensitive equipment.

Ishikawa said the Obayashi Corporation sees a space elevator as a new kind of public works project that would benefit all of humankind.

There's not enough steel on Earth to make a space elevator

Right now, one of the biggest obstacles to building a space elevator is what to make the tether or tube from.

To withstand the tremendous tension it would be under, the tube would have to be very thick if it were made out of typical materials, like steel. However, "if you try to build it out of steel, you would need more steel than exists on Earth," Johnson said.

Ishikawa's report suggested Obayashi Corporation might use carbon nanotubes. A nanotube is a rolled-up layer of graphite, the material that's used in pencils.

It's much lighter and is less likely to break under tension compared to steel, so the space elevator could be much smaller, Johnson said. But there's a catch.

While nanotubes are very strong, they're also tiny, a billionth of a meter in diameter. And researchers haven't made them very lengthy. The longest is only about 2 feet.

To be properly balanced while still reaching geosynchronous orbit – where objects stay in sync with Earth's rotation – the tether would need to be at least 22,000 miles long, per Ishikawa's report.

"So we're not there," Johnson said of the nanotube length. "But that doesn't mean it's impossible."

Instead, researchers might need to develop an entirely new material, Ishikawa said.

Other obstacles

Whatever the material turns out to be, there are still other problems.

For instance, a space elevator's tether would be under such incredible tension that it would be prone to snapping, Johnson said. A lightning strike could vaporize it. There's also other weather to consider like tornadoes, monsoons, and hurricanes.

Locating the tether base at the equator would lessen the likelihood of hurricanes, but it would still need to be in the open ocean to make it more difficult for terrorists to target, Johnson said.

It would also take a lot of trips to make up for that giant price tag for construction.

That's only scratching the surface of the challenges. And they can't all be solved by one company, Ishikawa said. "We need partnerships," he said. "We need different industries."

"Of course," Ishikawa said, "raising funds is very essential."

That's a lot of obstacles to overcome to start construction in time for operation by 2050, especially since Ishikawa estimated it would take 25 years to build. He noted that the 2050 estimate always came with caveats about the technology progressing. "It's not our goal or promise," he said, but the company is still aiming for that date.

"I think that those time estimates are optimistic," Johnson said, "even assuming there was a breakthrough tomorrow."

This article was originally published by Business Insider.