Artificial gravity: why we need it, how we’ll do it.
Have you ever watched Star Trek? And The Martian? And artificial gravity? For those who watched, have you ever noticed that Captain Kirk is standing still on the Enterprise? Why is that? I mean, if you are in the deep space, far from any planet’s gravitational attraction, you should be floating because of the absence of gravity.
Captain Kirk is standing with his feet on the Enterprise’s deck. He seems to weight the same that he would weight here on Earth, and also all the objects on the Hermes – as the interplanetary craft in the Martian is dubbed – are behaving as if they were in your room, and not in a spaceship travelling in the deep space. Something in the Enterprise and the Hermes is simulating and creating gravity.
How artificial gravity is possible?
How is it possible? We know that Star Trek is sci-fi. But what about real life? Is it possible to recreate artificial gravity? And why do we need artificial gravity? Let’s try to understand it better. Imagine that you’re inside a vehicle — or another machine — and you are spinning around so fast that the force presses your body against the wall or seat.
As you spin faster and faster than pressure forcing you against the wall increases (and conversely it decreases as the spin slows down). Sure you’ve experienced it before. The weight feels exactly like the force of gravity that keeps your body grounded to the earth. Think about it.
You may have experienced it in your childhood, when you visited for the first time an amusement park ride, with a classic Rotor Ride that has produced a great deal of joy since the middle of the 19th century. Did you remember it? How was it? I remember mine. It was so cool! But then I vomited.
By the way, a handful of people, including astronauts, experience the same phenomenon in a human-rated centrifuge, a machine that spins to produce these high “G forces,” also called acceleration.
They experience this G-force aboard high-performance aircraft during high speed turns, and during launches into space and when spacecraft rapidly slow as they reenter Earth’s atmospheres.
What is reduced-gravity aircraft?
Now I want to ask you a question: have you ever heard of a reduced-gravity aircraft? A reduced-gravity aircraft is a type of fixed-wing aircraft that provides brief near-weightless environments for training astronauts, conducting research and making gravity-free movie shots.
Versions of such aeroplanes were operated by the NASA Reduced Gravity Research Program, and one is currently operated by the Human Spaceflight and Robotic Exploration Programmes of the European Space Agency. The unofficial nickname “vomit comet” became popular among those who experienced their operation.
The aircraft gives its occupants the sensation of weightlessness by following a parabolic flight path relative to the centre of the Earth. While following this path, the aircraft and its payload are in free fall at certain points of its flight path.
The aircraft is used in this way to demonstrate to astronauts what it is like to orbit the Earth. During this time the aircraft does not exert any ground reaction force on its contents, causing the sensation of weightlessness.
Initially, the aircraft climbs with a pitch angle of 45 degrees using engine thrust and elevator controls. The sensation of weightlessness is achieved by reducing thrust and lowering the nose to maintain a neutral, or “zero lift”, configuration such that the aircraft follows a ballistic trajectory, with engine thrust exactly compensating for drag.
Weightlessness begins while ascending and lasts all the way “up-and-over the hump” until the craft reaches a downward pitch angle of around 30 degrees. At this point, the craft is pointing downward at high speed and must begin to pull back into the nose-up attitude to repeat the manoeuvre.
The forces are then roughly twice that of gravity on the way down, at the bottom, and up again. This lasts until the aircraft is again halfway up its upward trajectory, and the pilot again reduces the thrust and lowers the nose. This aircraft is used to train astronauts in zero-g manoeuvres, giving them about 25 seconds of weightlessness out of 65 seconds of flight in each parabola.
During such training, the aeroplane typically flies about 40–60 parabolic manoeuvres. In about two-thirds of the passengers, these flights produce nausea due to airsickness, giving the plane its nickname “vomit comet”.
But let’s go back to the Rotor Ride. This type of rotation produces gravity — artificial gravity to be precise. It provides weight to your body! You can’t distinguish the artificial-gravity weight from the weight on Earth: to your bones and your muscles, it wiìould be pretty much the same!
How to create artificial gravity?
If one wants to recreate Earth’s gravity on a spaceship, there are two main ways: the first one is to accelerate it at a constant acceleration of 9.81 m/s^2. And you may think there is no problem with it, but we have to deal with the speed of light! If you had an acceleration of 9.81 m/s^2, you’d soon reach the speed of light, experiencing all the consequences to which this situation would have. (For example, you would find yourself with an unexpected huge mass, so that it will be impossible for you to have the energy to accelerate!).
The second way it’s a little bit complicated but it doesn’t have problems in terms of speed of light, because it makes use of rotating spaceships, that recreate artificial gravity differently.
Consequently, for decades, science fiction writers have envisioned rotating spaceships that create artificial gravity for astronauts during the longest phases of space missions. These phases are when they are not extra-heavy due to the ship accelerating to build up speed, or decelerating in the atmosphere, but weightless due to the craft coasting, negating the effects of gravity.
Best examples of artificial gravity
Two examples of artificial gravity in science fiction are the 2015 film “The Martian” and the 1968 epic “2001: A Space Odyssey.” “The Martian” features the Hermes, an interplanetary craft, with a large, wheel-shaped section that rotates on its journey between Earth and Mars.
Did you see the film? It’s one of my favourites! As the camera zooms in, you notice that “up” for astronauts inside the Hermes is always toward the centre of the wheel, while “down,” the “floor,” is the rim. Also, space Station V in “2001: A Space Odyssey” is a spinning station that generates artificial gravity equal to that of the moon’s gravity.
Why we need artificial gravity?
But why we want to recreate gravity? It is something that we can avoid. Isn’t it? Apart from mere comfort, there are good reasons why we need artificial gravity on long-distance space missions.
For one, in weightlessness our bodies changes in ways that could be harmful when astronauts arrive at their destinations — such as Mars — or return to Earth. Bones would lose mineral content (they would soften, becoming vulnerable to fracture); muscles would shrink and weaken; fluids would shift toward the head and also would be excreted from the body, causing changes in the cardiovascular system and lungs; the nervous system would be thrown out of whack, and in recent years space medicine researchers have found what could be permanent eye damage in some astronauts.
Researchers are getting a better idea of it with volunteers and astronauts, developing new technologies measuring the damage caused by weightlessness pushing blood upwards to the head, and we found that arteries get stiffer by quite a bit while they’re in space.
In fact in six months in space, the arteries get stiffer by the equivalent of about 20 years of aging with muscle and artery damage. Add to that research suggesting that gravity may be required for humans to have a normal pregnancy in space and it almost seems like a no-brainer that any spacecraft carrying humans around the solar system either should rotate, or have some part of the ship that does.
Is it possible to travel in an artificial gravity spacecraft?
Are NASA and others researching the possibility to travel in an artificial gravity spacecraft? The answer is yes. Since the 1960s, NASA scientists have been considering the prospect of artificial gravity by way of rotation.
However, the effort, funding and overall enthusiasm have waxed and waned through the decades. One example is the Nautilus-X project. The Nautilus-X ( Non-Atmospheric Universal Transport Intended for Lengthy United States Exploration ) is the project of a possible embodiment Multi-Mission Space Exploration Vehicle) developed by Technology Applications Assessment Team of NASA.
The spacecraft was designed for long-duration missions (one to twenty-four months) to travel out of the atmosphere with a crew of six. To reduce the effects of microgravity on human health, the vehicle will be equipped with a centrifuge. The vehicle proposed is relatively cheap by space systems standards [being estimated to cost 3.7 billion dollars (USD). However, this project’s development was cancelled.
While NASA has not emphasized research on artificial gravity over the past half-century, scientists both inside and outside of the space agency are studying a range of situations. Mice spinning in a small centrifuge aboard the International Space Station survived with no problem and Earth-bound humans are learning how to adapt in spinning rooms.
There’s one at the Ashton Graybiel Spatial Orientation Laboratory at Brandeis University and the DLR Institute of Aerospace Medicine in Cologne, Germany, is home to the DLR Short-Arm Centrifuge, Module 1. It’s the only one of its kind in the world researching the effects of altered gravity, especially as it pertains to health risks that occur in microgravity.
Why haven’t we built ourselves a centripetal space station yet?
One problem is the size. In fact, the scale of such a craft would pose some (big) problems. According to physics, the smaller the spacecraft is, the faster it has to rotate, so if you’re going to generate gravity, it’s got to be done with a large spacecraft that spins very slowly. The bigger the disk, the slower you can rotate it.
For example one-half, the usual amount that you feel on Earth — the length of the radius of rotation (the distance from you standing on the floor to the centre of whatever is spinning) determines how fast you need to spin.
Build a wheel-shaped craft with a radius of 738 feet (225 meters) and you’ll produce full Earth gravity (known as 1G) rotating at just 1 RPM. It would be great: nobody would vomit in that case.
Why artificial gravity bother in research?
But if the need for artificial gravity is so clear, why bother with research in space, or on Earth? Why don’t engineers simply get to work designing spinning ships, like the Hermes? The answer is that artificial gravity is complicated. It requires a trade-off because all that spinning creates problems. As on the Rotor Ride, moving your head while you’re spinning that fast causes nausea.
Anyway, as for Captain Kirk and the objects on the Enterprise spaceship, other than the floor being a little bit curved, things aboard such a craft would feel pretty normal. But building and flying such an enormous structure in space would entail numerous engineering challenges: we are pretty sure that even Elon Musk, our hero, doesn’t know how to build such a structure! Today’s missions, anyway, are fortunately short-term space missions.
Short-term space travel doesn’t really need artificial gravity. Most of the research done on ISS relies on the lack of gravity. And on a long-term mission, say, to Mars, the last thing NASA wants is an even bigger, fuel-hungrier, more expensive spacecraft.
In this article, we have talked about artificial gravity. Why we need artificial gravity and how it works. We have also talked about many queries related to artificial gravity. No doubt we are clear about it but it’s really very difficult to implement those things to create a artificial gravity.
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