Space elevators have been dismissed as science fiction fantasies. However, I believe they will be a reality soon, perhaps in the next two to three decades. As an aerospace engineer and physics professor, I have been drawn back to the idea of a cable connecting Earth and space that can carry people and cargo. Together with other researchers, I have discovered new ways to play with designs and answer questions how space elevators could function ..
There’s many reasons to build an elevator in space . It’s much more practical than rockets and offers major energy savings ;. Accessibility is another reason that is often overlooked. As trips to space are routine and almost always independent of weather conditions, the word “space mission” will be replaced with “transit”. Transits that involve humans would be safer than current procedures, in which astronauts must take a minimal risk to their lives for each launch. The space elevator is a bridge to all of the solar system. You can orbit Earth by releasing a payload from the lower portion. But if you release a payload from the upper portion, you can orbit the sun without fuel.
Although I may seem to be a space elevator advocate, the truth of the matter is that I just enjoy their mechanics. I find it fascinating to imagine a world where we are responsible custodians of this planet in the face of monumental problems.
My story begins in 2004, when I was a master’s degree student sitting in the office of Professor Arun Misra, hoping he would supervise my thesis. Misra was the top space expert at McGill University so I was a bit intimidated. The conversation went like this:
Me – What kind of research would you suggest I do?
Misra – Have you ever heard about a space elevator.
Me: No. What is it?
Misra: Imagine a 100,000-kilometer-long cable that extends up from Earth’s equator and is fixed to a satellite at the far end. The system moves along with the Earth. Climbers can climb the cable to transport payloads and then release them in space. I was wondering if you could study the dynamics of this system.
Me : This sounds… difficult.
Misra – It’s not hard work. You can build a space elevator right here on Earth ….
It will be difficult.
Flash forward a few decades. I had recently published my master’s thesis, entitled The Dynamics of a Space Elevator. I was now a satellite engineer. My friend introduced me to Colin, his buddy in satellite design. My wife rolled her eyes. Colin was intrigued by the idea of a space elevator.
Me: If you stood on the equator and stared up at a satellite in a geosynchronous orbit (approximately 36,000 kilometers in altitude), it would appear fixed in space, rotating unconnected around the Earth once per day because its speed is just right. Now the satellite drops a cable to Earth and simultaneously uses fuel to climb higher. The cable is fastened on the Earth end as the satellite reaches just the right altitude, and the system still rotates along with the Earth. The cable is used by mechanical climbers to scale the cable like trains on a railroad track, and deliver payloads to space.
Colin – But what keeps the cable taut and taut?
Me is a combination of gravitational-centrifugal effects that compete with each other and vary along the length the cable. Above geosynchronous orbit gravity wins and above it centrifugal effect win. The result is tension all around, with the maximum amount at geosynchronous orbit.
Colin – It’s Friday night. Use smaller words.
Me: To build it, we need a material whose specific strength is about 50 times higher than steel. While we wait, I and a few others pretend that this problem will be solved. We also work on other engineering aspects of space elevators.
My wife and I crossed paths with Colin again in 2014. He asked, “How’s that space elevator going?” My wife closed her eyes and said, “Please, no .”
Colin – What I don’t understand is why the cable doesn’t fall to the bottom when a climber loads onto it at the base?
Me – If a climber is located below GEO, especially near Earth, the cable’s tip will move down a small amount and the tension profile along it will change. The problem is that the cable connecting the climber to the Earth experiences a drop of tension. This is similar to holding an elastic band vertically under tension and attaching a mass halfway down it. The tension would drop to zero and the cable would become untieved, causing the structure to lose its inherent stability. A climber, and any other items it carries, could have a maximum weight of about 1% of the total cable mass. This is still a lot considering that the cable is expected be hundreds of tonnes.
Colin – How is the cable material progressing?
Me : I’ve already told you that this is not my thing.
Colin – Get on it!
It is now 2022. Recently, I presented a summary of nearly two decades worth of work on space elevators at a Vanier College seminar. I also teach physics. The talk is over and the Q&A begins.
Student 1 – When will the material to build the elevator be available?
Me: While the synthesis of potentially suitable materials has progressed in recent years, we are still at least 10 years away from a material solution (one having adequate properties, and that can be manufactured reasonably quickly at a reasonable cost). It is not uncommon for new technologies to wait for better material science. Fortunately, materials research continues for reasons that are not related to space elevators.
Student 1: This sounds great. But why build it?
Me – Rockets as a means to transport are absurd. For a typical space mission, upwards of 90 percent of the total mass on the launchpad is the fuel! It’s like being in a car with no motor, just a pressurized 100,000-liter fuel tank. This inefficient way of escaping Earth’s gravity must be replaced with a greener route to space.
NASA plans to get humans to Mars before 2040. Although I believe that humans will walk on Mars, it will take hundreds of billions of money before we have an operational space elevator, this infrastructure is essential for a sustainable endeavor.
Student 2: When do you think one of these will be built?
Me: Famed author and engineer Arthur C. Clarke, whose novel The Fountains of Paradise chronicles the building of the first space elevator, was asked this question in the early 1990s. His famous reply was, “Probably about 50 years after everyone quits laughing.” A more modern-day answer might be, “We’ll know we are close when Elon Musk starts taking credit for it.”
Today I feel exactly the same as I did when I sat nervously at Arun’s (yes we still work together and it will always seem a bit strange) office. This elegant avenue of space captures my imagination, and fills me up with hope.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.