What will become of the Earth after the orbital shift? Engineer's view

2024 Author: Seth Attwood | [email protected]. Last modified: 2023-12-16 15:55

In the Chinese science fiction film Wandering Earth, released by Netflix, mankind, using huge engines installed around the planet, attempts to change the Earth's orbit to avoid its destruction by the dying and expanding Sun, as well as to prevent a collision with Jupiter … Such a scenario of a cosmic apocalypse may one day actually happen. In about 5 billion years, our sun will run out of fuel for a thermonuclear reaction, it will expand and, most likely, swallow our planet. Of course, even earlier we will all die from a global rise in temperature, but changing the Earth's orbit may indeed be a necessary solution to avoid a catastrophe, at least in theory.

But how can humanity cope with such an extremely complex engineering task? Space systems engineer Matteo Ceriotti from the University of Glasgow shared several possible scenarios on the pages of The Conversetion.

Suppose our task is to displace the Earth's orbit, moving it away from the Sun about half the distance from its current location, to about where Mars is now. Leading space agencies around the world have long been considering and even working on the idea of displacing small celestial bodies (asteroids) from their orbits, which in the future will help protect the Earth from external impacts. Some options offer a highly destructive solution: a nuclear explosion near or on the asteroid; the use of a "kinetic impactor", the role of which, for example, can be played by a spacecraft aimed at colliding with an object at high speed to change its trajectory. But as far as the Earth is concerned, these options will certainly not work due to their destructive nature.

In the framework of other approaches, it is proposed to withdraw asteroids from a dangerous trajectory using spacecraft, which will act as tugs, or with the help of larger spaceships, which, due to their gravity, will withdraw the dangerous object from the Earth. Again, this will not work with the Earth, since the mass of objects will be completely incomparable.

Electric motors

You will probably see each other, but we have been displacing the Earth from our orbit for a long time. Every time another probe leaves our planet to study other worlds of the solar system, the carrier rocket carrying it creates a tiny (on a planetary scale, of course) impulse and acts on the Earth, pushing it in the direction opposite to its motion. An example is a shot from a weapon and the resulting recoil. Fortunately for us (but unfortunately for our "plan to displace the Earth's orbit"), this effect is almost invisible to the planet.

At the moment, the most high-performance rocket in the world is the American Falcon Heavy from SpaceX. But we will need about 300 quintillion launches of these carriers at full load in order to use the method described above to move the Earth's orbit to Mars. Moreover, the mass of materials required to create all these rockets will be equivalent to 85 percent of the mass of the planet itself.

The use of electric motors, in particular ionic ones, which release a stream of charged particles, due to which acceleration occurs, will be a more effective way of imparting acceleration to the mass. And if we install several such engines on one side of our planet, our old Earth woman can really go on a journey through the solar system.

True, in this case, engines of truly gigantic dimensions will be required. They will need to be installed at an altitude of about 1000 kilometers above sea level, outside the earth's atmosphere, but at the same time securely fixed to the surface of the planet so that a pushing force can be transmitted to it. In addition, even with an ion beam ejected at 40 kilometers per second in the desired direction, we still need to eject the equivalent of 13 percent of the Earth's mass as ion particles to move the remaining 87 percent of the planet's mass.

Light sail

Since light carries momentum but has no mass, we can also use a very powerful continuous and focused beam of light, such as a laser, to displace the planet. In this case, it will be possible to use the energy of the Sun itself, without in any way using the mass of the Earth itself. But even with an incredibly powerful 100-gigawatt laser system, which is planned to be used in the peakthrough Starshot project, in which scientists want to send a small space probe to the nearest star to our system using a laser beam, we will need three quintillion years of continuous laser pulse to to meet our orbit reversal goal.

Sunlight can be reflected directly off a giant solar sail that will be in space but anchored to Earth. As part of past research, scientists have found that this would require a reflective disk 19 times the diameter of our planet. But in this case, to achieve the result, you will have to wait about one billion years.

Interplanetary billiards

Another possible option for removing the Earth from its current orbit is the well-known method of exchanging momentum between two rotating bodies to change their acceleration. This technique is also known as gravity assist. This method is often used in interplanetary research missions. For example, the Rosetta spacecraft that visited comet 67P in 2014-2016, as part of its ten-year journey to the object of study, used gravity assist around the Earth twice, in 2005 and in 2007.

As a result, the Earth's gravitational field each time imparted an increased acceleration to the Rosetta, which would have been impossible to achieve with the use of the engines of the apparatus itself. The Earth also received an opposite and equal acceleration momentum within the framework of these gravitational maneuvers, however, of course, this had no measurable effect due to the mass of the planet itself.

But what if you use the same principle, but with something more massive than a spacecraft? For example, the same asteroids can certainly change their trajectories under the influence of the Earth's gravity. Yes, a one-time mutual influence on the Earth's orbit will be insignificant, but this action can be repeated many times in order to ultimately change the position of the orbit of our planet.

Certain regions of our solar system are quite densely "equipped" with many small celestial bodies, such as asteroids and comets, the mass of which is small enough to draw them closer to our planet using appropriate and quite realistic technologies in terms of development.

With a very careful calculation of the trajectory, it is quite possible to use the so-called "delta-v-displacement" method, when a small body can be displaced from its orbit as a result of a close approach to the Earth, which will provide a much greater momentum to our planet. All this, of course, sounds very cool, but earlier studies were carried out that established that in this case we would need a million such close asteroid passages, and each of them must occur in the interval of several thousand years, otherwise we will be late by that time when the Sun expands so much that life on Earth becomes impossible.

conclusions

Of all the options described today, using multiple asteroids for gravity assist seems to be the most realistic. However, in the future, the use of light may become a more suitable alternative, of course, if we learn how to create giant space structures or super-powerful laser systems. In any case, these technologies may also be useful for our future space exploration.

And yet, despite the theoretical possibility and the likelihood of practical feasibility in the future, for us, perhaps the most suitable option for salvation would be resettlement to another planet, for example, the same Mars, which can survive the death of our Sun. After all, humanity has long been looking at it as a potential second home for our civilization. And if you also consider how difficult it will be to implement the idea of a displacement of the Earth's orbit, colonizing Mars and the possibility of terraforming it to give the planet a more habitable appearance may not seem like such a difficult task.