How Fast Does The International Space Station Travel?
How Fast Does The International Space Station Travel?
The International Space Station, like most artificial satellites, orbits in low Earth orbit at an altitude of approximately 250 miles. Its orbital speed, estimated by national space agencies, is around 17,700 mph.
The station's incredible speed is difficult to fathom. It covers a distance of roughly 700,000 kilometers in just one day, which is roughly twice the distance between the Earth and the Moon. Completing 16 orbits per day, each orbit takes just over an hour and a half. The astronauts on board have the opportunity to witness the sunrise 16 times a day or an astonishing 5,840 times per year. It's hard to imagine the awe-inspiring experience of witnessing so many dawns in space.
Do Astronauts Feel The Speed On The International Space Station?
Now that you have an understanding of the International Space Station's incredible speed, it's important to note that the acceleration experienced by astronauts is what we perceive, not the actual speed. As you may know from travelling by plane, higher speeds often result in stronger g-forces affecting passengers and crew. However, this is not the case in space, as it's not just about weightlessness and a lower free fall acceleration than on Earth, but also the gravitational forces at play.
In orbit, astronauts experience two accelerations of the same magnitude: centripetal (towards the Earth) and centrifugal. These forces perfectly balance each other, so when the station reaches a constant orbital speed, the astronauts feel no movement at all. If the station changes its orbit height, there may be slight sensations of acceleration, but it does not cause significant discomfort.
What Makes The International Space Station Move So Fast?
Upon the launch of the initial module, Zarya, to low Earth orbit (LEO), it was immediately accelerated to reach the necessary speed of 17,700 mph. This speed was subsequently sustained by the vehicles delivering the remaining modules for assembly, as well as crew and supply missions. With each successful docking, the station receives an additional propulsion boost, which is a recurring process to avoid critical changes in its orbit. This helps to regulate the speed of the ISS and prevent it from moving too far from the Earth.
What Keeps The International Space Station Moving?
ISS maintains a stable orbit due to its speed, which prevents it from succumbing to the gravitational pull of the Earth. The balance between the velocity and gravity vectors determines the station's radial trajectory, while its speed is determined by its altitude. In the absence of external factors, this speed can remain constant indefinitely, ensuring a stable orbit.
The height of the ISS's orbit was carefully chosen, taking into account the station's mass (400 tons) and the need to avoid high levels of space radiation for astronauts. Going higher is not feasible, while a descent to lower altitudes would cause the station to slow down due to atmospheric drag. Hence, engineers calculated the optimal orbit parameters for the ISS to function as a long-lasting Earth satellite.
Is The ISS Moving At A Constant Speed?
The exact speed of the ISS cannot be determined as it varies based on the height of its orbit, which can range from 278 to 460 kilometers. The fluctuation is caused by the gravitational pull of celestial bodies such as the Moon, the Sun, and comets, resulting in a gradual change in the station's parameters, including altitude and speed. The speed of the ISS, therefore, cannot be fixed and is subject to change due to external factors.
Furthermore, the ISS is at risk of colliding with space debris and meteoroids, which could damage its surface. To mitigate this, astronauts on board the ISS perform periodic orbital adjustment manoeuvres using orientation motors and low-power pneumatic installations to make small adjustments to the station's position, sometimes as little as a centimetre.
