Space elevators are less science fiction than you think

Space elevators are often dismissed as a sci-fi dream, but I think they will soon be there – maybe in two or three decades. Throughout my career as an aeronautical engineer and professor of physics, I kept coming back to the concept of a cable running from Earth to space, along which people and cargo could easily travel. In recent years, I and other researchers have come up with new ways to tinker with designs and answer questions about how space elevators work.

There are many reasons to build a space elevator. The obvious one is the main energy and cost savings; It’s a more practical way to get into orbit than rockets. Another reason that is often overlooked is accessibility. The word “space mission” would be replaced by the word “transit”, as flights into space would become routine and mostly independent of weather conditions. Transits involving humans will be safer than current practices, as astronauts must accept unlimited risk to their lives with each launch. The space elevator becomes a bridge to the entire solar system. Release a payload at the bottom, and it will go around the Earth, but do it at the top, and it will go around the sun; All without fuel.

While I may be an advocate of the space elevator, the truth is that I simply enjoy studying their mechanics. In a world with enormous problems, dreaming about such projects allows me to envision a scenario in which we become responsible custodians of the planet.

My story began in 2004, when I was a master’s student sitting at Professor Arun Misra’s desk, hoping that he would supervise my dissertation. Misra was the leading aerospace expert in the mechanical engineering department at McGill University, so I was pretty intimidated. Conversation went something like this:

Me: What kind of research do you think I could do?

Misra: Have you ever heard of a space elevator?

Me: no what is this?

Misra: Imagine a 100,000-kilometre cable stretched from the Earth’s equator and attached to a satellite at the far end. The system rotates with the Earth. Climbers can scale cable-transport payloads and then launch them into space. I was thinking you might study the dynamics of this system.

Me: This sounds… hard.

Misra: Your work will not be difficult. Building a real space elevator here on Earth….
That will be hard.

Fast forward a few years. I had recently published my master’s thesis titled Space elevator dynamics. I was now working as an engineer in satellite design. While out for the weekend, my boyfriend introduced me to his friend Colin as “The Space Elevator Guy.” My wife rolled her eyes. I explained to Colin how a space elevator could work.

Me: If you stood on the equator and stared at a satellite in geosynchronous orbit (about 36,000 kilometers in altitude), it would appear stationary in space, circling discontinuously around the Earth once a day because its speed is just right. Now, this satellite is dropping a cable to the ground, while at the same time using fuel to go higher. The cable is attached to the ground end where the satellite reaches the correct height and order resident rotates with the earth. The cable becomes the track that mechanical climbers scale like trains on a vertical railroad, hauling payloads into space.

Colin: But what keeps the cable taut?

I: A combination of gravitational and centrifugal effects, which compete with each other, and vary along the length of the cable. Under geosynchronous orbit, gravity wins out, and then centrifugal effects win out. The result is tension throughout, with maximum exact geosynchronous orbit.

Colin: It’s Friday night. Use smaller words.

Me: In order to build it, we need a material whose specific strength is about 50 times higher than that of steel. But, meanwhile, I and a handful of other people in the world pretend this problem will be solved and other engineering aspects of space elevators addressed while we wait.

Colin: Rad.

My wife and I crossed paths with Colin back in 2014. “How’s that space elevator going?” Asked. My wife closed her eyes, her face saying, “Please no.”

Colin: What I didn’t get is why isn’t the cable fully retracted when a climber is loaded onto it at the bottom?

I: If the climber is below the GEO, especially close to the ground, the end of the cable moves down a small amount, and the tension coil changes along the cable. The real problem is that the part of the cable between the climber and the ground experiences a drop in tension (as if you had held an elastic band vertically in tension, then affixed a block halfway along it). If the tension drops to zero, the cable will not be tensioned, and the structure will lose its inherent stability. It turns out that the climber (and whatever it’s carrying) can have a maximum mass of about 1 percent of the cable’s total mass. That’s still a lot of mass, though, because the cable is expected to be in the hundreds of tons.

Colin: How does this cable material come from?

Me: I told you, it’s nothing.

Colin: Get it, man!

It’s now 2022. I was recently presenting a summary of nearly two decades of my space elevator work at a symposium at Vanier College, where I teach physics. The talk ends and the question-and-answer segment begins.

Student 1: When will the elevator building materials be ready?

Me: Although manufacturing of potentially suitable materials has advanced in recent years, we are still at least 10 years away from a physical solution (one that has suitable properties, and can be manufactured reasonably quickly and affordably). It’s not unusual for new technologies to wait for better materials science, and fortunately, materials research is going for reasons that have nothing to do with space elevators.

Student 2: It looks really cool. But why should we build it?

Me: When you think about it, rockets as a means of transportation are preposterous. For a typical space mission, upwards of 90 percent of the total mass is on the launch pad he is fuel! It’s like being in a car with no engine, just a 100,000 liter pressurized fuel tank. We need to replace this inefficient way of escaping Earth’s gravity with a greener route into space.

NASA plans to get humans to Mars before 2040. I suspect people will actually be walking on Mars (at a cost of hundreds of billions of dollars) before we have a functioning space elevator, but for this to be a sustainable endeavor, it needs infrastructure like a space elevator, And it’s better sooner rather than later.

Student 3: So, when do you think one will be built?

I am: acclaimed author and engineer Arthur C Clarke, his novel Paradise Springs Dating the construction of the first space elevator, this question was raised in the early 1990s. His famous response was, “Maybe about 50 years after everybody stops laughing.” A more recent answer might be, “We’ll know we’re close when Elon Musk starts taking credit for it.”

Today, I feel a lot like I did as I sat nervously in Aaron’s office (yes, we still work together, I call him that now, and it will always be a little weird). This elegant path into space captures my imagination and fills me with hope.

This is an article of opinion and analysis, and the opinions expressed by the author or authors are not necessarily opinions Scientific American.

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