After millions of years on Earth, it was only until the last century that anything has escaped the planet’s gravitation pull. The historic day remains marked on October 1957, when the rocket called The Sputnik successfully reached orbit. Since then, thousands of spacecraft have made it to space carrying satellites, telescopes, and occasionally humans.
Limits of Chemical Rockets
Those same rockets still serve as our only form of transportation to outer space. As the use of the spacecraft grew, so did the human imagination. We now have goals to visit Mars, travel further into space, and advance current technology. All of which chemical rockets have failed to meet. But how, exactly?
First, let’s talk about what makes up a rocket.
Rockets are powerful engines intended to carry objects past our planet’s atmosphere and into space. They’re propelled by thrust, a force that burns fuel as exhaust gases escape the engine.
The main components that form a rocket include the payload, guidance, and propulsion system, which makes up the structure system.
The payload system is at the top of the rocket. It’s space where cargo, satellites, or humans are kept. The standard shape for the payload system is typically a cone, but the design can change depending on the mission.
The guidance system ensures that the rocket stays on its planned route. Inside is a series of computers and radars used to maneuver the spacecraft while flying. It has three fundamental parts: navigation, guidance, and control.
Navigation tracks the rocket’s location. Guidance acts as the driver. It uses the data gathered by the navigation system to send signals to flight control, enabling the aircraft to complete its launch. Lastly, there’s the control which accepts directions from guidance to make changes in aerodynamic/engine controls.
The propulsion system takes up most of the spacecraft. It’s made up of the components that launch the rocket into orbit, like the engine, fuel, and oxidizer.
All three of these systems have to work together to pull against gravity and launch.
What Makes A Rocket Inefficient?
When they run out of fuel, the empty container is detached to increase efficiency. This is called staging, and it’s why you never see a full rocket in space. The guidance system is the extra boost the rocket needs to make it into orbit. The rest of the rocket either gets burned in the atmosphere, crashes back on Earth, or becomes space debris.
It’s difficult to get it back, that’s why most rockets are single-use. Not to mention the payload expenses. It costs about $20,000 per kilogram just to put the rocket in space. That means if we sent an average human for exploration, it would cost $1.3 million.
Luckily, experts have come up with alternatives for space transportation. One intriguing concept involves the space elevator.
Introducing Space Elevators
The space elevator is a straightforward concept—it’s a long cable stretching from the planet's surface into space. It sounds like science fiction, but it can certainly become a reality.
Let’s go back to the year 1895. A Russian scientist by the name of Konstantin Tsiolkovsky first proposed the idea of a space elevator. His inspiration came from the design of the Eiffel Tower. Though, instead of a 324-meter tower, he suggested making a similar building that went all the way into space.
There are four basic parts: the tether, climber, anchor, and counterweight.
The tether, also known as the cable, is the long piece that connects the surface to space. This is the most essential part of the space elevator. However, there’s currently no material durable enough to create it. That was, until the year 1991, but we’ll get more into that later.
The climber operates as the “elevator carriage,” moving up and down the cable carrying cargo and (possibly) humans.
The anchor serves as the station to keep the tether grounded.
The counterweight is a large mass used to keep the cable taut. A heavy asteroid, space station, and are a few examples of objects that could act as the counterweight.
The Construction Process
How are we going to make a 100,000-kilometer elevator to space? It’s a bit complicated.
Let’s start with the location. The best place to start development would be near or along Earth’s equator, and there’s a reason for that. Above the equator, 35,786 kilometers into space, is the geostationary orbit. Here, the orbital period synchronizes with Earth’s rotation.
The geostationary orbit would work as the elevator’s center of gravity. This would keep the structure proportional to Earth’s rotation and make sure the cable remains upright. But how would the elevator be built?
First, a satellite is sent up to space and drops a ribbon, which is attached to the anchor back on Earth. Then, a climber is sent up, pulling a second ribbon alongside the first. This process is repeated with progressively larger climbers until the ribbon has been thickened to a cable, creating the space elevator. Though, it does take some time.
After 207 climbers, 2.3 tears, the cable would finally be equipped to support a 20,000 kg climber with a 13,000 kg payload. This construction is estimated to be about $40 billion.
Importance of Nanotechnology
Nanotechnology is the manipulation of matter at an atomic and molecular scale. The size of a nanoparticle is approximately 1 to 100 nanometers. To understand how small that is, a strand of DNA is 2.5 nanometers and human hair is 50,000 to 100,000 nanometers in diameter.
Still can’t wrap your head around it? Here’s a picture of it.
Finding material strong enough to create the elevator cable has posed a challenge. What does this have to do with nanotechnology? Everything. And it begins with carbon nanotubes.
Carbon nanotubes (CNTs) are framed as one of the strongest materials ever created. The person credited as the inventor is the Japanese physicist Sumio Iijima back in 1991.
Just a few years later, in 2000, an American scientist by the name of Bradley Edwards suggested creating a 100,000 km long ribbon using carbon nanotubes.
Since then, carbon nanotubes have been the highly suggested material used to create the cable. In addition to being strong, they would also be able to withstand severe weather, radiation, and other natural disasters.
Materials such as boron nitride nanotubes and diamond nanothreads are similar to carbon nanotubes, but they haven’t been researched enough to be considered for construction.
A lot of things can go wrong if we choose the wrong material, but the biggest safety risk is the elevator snapping in half. If it breaks near the anchor, the whole thing will drift into space. And if it breaks near the top, the cable will wrap around the Earth, creating dangerous space debris. The cable must remain stable, otherwise, there will be a serious threat to humans.
Why Do We Need One Anyway?
Current rocket technology is expensive. With space elevators, we can cut down on costs tremendously. Instead of spending $20,000 per kilogram, it would only cost $200–$500. Additionally, the environmental impacts of launching rockets will decrease since space elevators don’t burn fuel. They also allow for an easy way to dispose of space debris, lowering the risk of collisions.
If humans were able to build a space elevator, it would completely change the future of space travel. Countries like Japan and China already plan on building a space elevator by 2050. But only time will tell whether or not we’ll succeed.