I’ve probably seen this kind of science fiction scene several times. The stubborn spaceship captain and his crew appear to be running away from the aliens/spewing supernova/using fuel. But then, soon, they find the planet! So they burn a rocket towards it, then dive in and use that gravity to safely use Things Shot. Hooray! Cue victory music.
So, at least it’s on the silver screen. But does this operation work in real life?
yes! Well, it’s not the way it is in movies, but it’s the case. However, it is widely known as a gravity power plant Most scientists call it gravity supportit is an essential tool for most interplanetary missions.
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The idea seems simple enough. When a spacecraft approaches a giant object, for example, the gravity of a planet, a planet, will bend its orbit and change the direction of the spacecraft. But there’s more to it: spacecraft can actually speed up using planetary gravity or After this operation, the speed will be slower and it will be easier to sail to the outer or inner planets, respectively.
The part that bends the trajectory is apparent enough, but the speed-up or slowdown parts are rather counterintuitive. It is related to gravity symmetry.
If you drop the rubber ball a little further away from the ground, it will accelerate as it falls, and accelerate to an impact. It then bounces back, moves up and slows down as it does. It will eventually stop. But in any case, It cannot bounce higher than the height you dropped it. Just as the energy of motion (energy of motion) fell, it fell, it slowed backwards, so we lost it again. This action is symmetrical so at best (if you have a completely elastic ball and you do this experiment in a vacuum), it will bounce back to the same height as you dropped it.
The same applies to spacecraft approaching planets. The gravity of the world accelerates you as you fall, you whip with the closest approach (it’s the “slingshot” part), and lose that extra speed as you move, as the gravity of the planet is still pulling you. The spacecraft will move when that gravity grip slips off. For the planet At the same speed as the first approaching.
If all bonus speeds are lost along the way, how can I use this manipulation to accelerate the spacecraft? The important thing is the phrase “for the planet.” For example, if you approach a planet at 20km/s per second, you will depart at the same speed. But it’s your speed measurement For the planet.
At the same time, importantly, the planet orbits the Sun. As you approach a planet from behind (i.e. the direction of its movement), the planet’s gravity gives you a boost, which also draws you in a heliocentric sense and adds a portion of your orbital velocity. It speeds you up on the way to your destination and gives you a kick compared to the sun. Essentially, spacecrafts earn net profits of speed by stealing a little of the planet’s orbital kinetic energy.
Second, this means that the planet actually slows down a bit in orbit around the Sun. But don’t be afraid: planets are slower in proportion to how big it is than spacecraft. Comparing a typical Wanton probe to a world several times more, the planet is not slow at all. It can activate 1 million probes and cannot communicate differences in orbital speed. The bacteria that bounce off you while you walk will have a much greater impact on you.
The reason it’s worth tackling the gravitational support trouble is that the spacecraft is launched by a rocket and can only accelerate to top speed. For today’s rockets, these speeds are very low and interplanetary distances are so large that even the fastest and most direct voyages take years (or decades at destinations in the outer solar system). While spacecraft can be loaded with more fuel and burned to load faster, there are limitations too. Fuel has mass and needs to accelerate that extra mass. This will take more fuel. This Catch-22 is explained by what is called Rocket equationand that means the amount of fuel you need to add to move a little faster. very Quick.
Therefore, shave times for voyages require other methods, such as sucking speeds from large, juicy planets along the way. For example, the Cassini Probe to Saturn, launched in 1997, was a huge spacecraft the size of a school bus, with a mass of 2.5 metric tons without fuel. (Along with launch vehicles and other equipment, the addition of the fuel needed to fulfill the mission on Saturn tilted the scale to 5.7 metric tons.) It would have actually taken forever to reach Saturn on a rocket back then. So the mission planner took advantage of Jupiter to pass the spacecraft and manipulate a speed boost slingshot, which saved quite a lot of time. In fact, to go out to Jupiter in the first place, Cassini also played two fuel-saving Venus, which steals the planet’s orbital energy every time, and one Venus of Earth.
Gravity assist also works the opposite. The Earth orbits the Sun at more than 30 km/s, so firing a probe on the Sun or inner planet is very stiff due to its lateral velocity. Instead, mission planners prefer routes with more circuitry. They launch spacecraft at a speed sufficient to fall, for example, in the opposite direction of Earth’s path around the Sun, where they donate some of their orbital energy to the planet, falling towards the Sun. Bepicolombothe European Space Agency and the Japanese Aerospace Exploration Agency’s mission to Mercury did exactly this, passing Earth once and Venus twice, entering near Mercury. Still, I had to sum it up Six Gravity helps past mercury match the orbital velocity of the planet around the Sun. The last assist will be in January 2025, and will enter mercury orbit in November 2026.
Gravity Assist is a symbolic example of why space travel is difficult-that teeth After all, it’s truly rocket science. Gravity is the greatest culprit. Escape from the Earth is the biggest part of the problem. Ironically, gravity can be very easily reached most of the rest of the solar system.
