Hohmann transfer orbit facts for kids

A Hohmann transfer orbit is a special path a spacecraft takes to move from one orbit to another around a planet or star. Think of it like changing lanes on a cosmic highway! This method is the most efficient way to do this, saving a lot of rocket fuel. It uses an oval-shaped orbit to make the journey.

A simulation of a Hohmann transfer orbit. The spacecraft moves from a smaller, inner orbit to a larger, outer orbit.

To use a Hohmann transfer, a spacecraft needs two pushes from its engines. The first push puts it onto the oval-shaped transfer orbit. The second push helps it settle into the new, desired orbit.

How Does a Hohmann Transfer Work?

Imagine a spacecraft orbiting Earth in a low circle. If mission control wants to move it to a higher orbit, they use a Hohmann transfer.

Here's how it works:

• First Push: The spacecraft fires its engines briefly. This burst of speed makes its orbit stretch out into an oval shape. This oval orbit touches both the old, lower orbit and the new, higher orbit.
• Cruising Phase: The spacecraft then travels along this oval path. It doesn't need to use its engines during this part. It's just coasting, pulled by the planet's gravity.
• Second Push: When the spacecraft reaches the highest point of its oval path, which is also the height of the new orbit, it fires its engines again. This second push gives it just enough speed to enter the new, circular orbit.

This two-step process is like throwing a ball up into the air and then giving it another gentle push when it reaches the right height to keep it floating there.

Why is it Fuel-Efficient?

The Hohmann transfer orbit is considered the most fuel-efficient way to change orbits. This is because it uses the least amount of velocity change, or "delta-v," as scientists call it.

Here's why it saves fuel:

• Using Gravity: Instead of constantly burning fuel to fight gravity, the spacecraft uses the planet's gravity to help it along the oval path.
• Short Bursts: The engines are only fired twice, for short periods. This is much more efficient than burning fuel continuously.
• Minimum Energy: This path requires the smallest total change in speed to get from one circular orbit to another. Less speed change means less fuel needed.

Saving fuel is very important for space missions. Fuel is heavy, and launching heavy things into space is expensive.

Real-World Uses of Hohmann Transfers

Hohmann transfer orbits are not just a theory. They are used all the time in real space missions!

• Moving Satellites: Many satellites are launched into a low orbit first. Then, a Hohmann transfer orbit is used to move them to their final, higher orbits. This is common for communication satellites that need to be in a specific high orbit.
• Reaching the Moon: When a spacecraft travels to the Moon, it often uses a type of Hohmann transfer. This is called a Lunar Transfer Orbit (LTO). The spacecraft starts in Earth orbit, gets a push to go on an oval path towards the Moon, and then gets another push to enter Moon orbit.
• Interplanetary Travel: While a simple Hohmann transfer is great for moving between orbits around the same body, traveling between planets is more complex. However, the basic idea of using efficient, oval paths is still key. More advanced methods, like the Interplanetary Transport Network, build on these ideas to use even less fuel by taking advantage of the gravity of multiple planets. For example, the NASA InSight probe used a path similar to a Hohmann transfer to get from Earth to Mars.

Images for kids

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  An example of a Hohmann transfer orbit between Earth and Mars, as used by the NASA InSight probe.       InSight ·       Earth ·       Mars

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  This graph shows how the total energy changes during a Hohmann transfer between two circular orbits.

See also

In Spanish: Órbita de transferencia de Hohmann para niños