How can astronauts know how fast they are moving?

Let’s use our car again, but this time we will get real numbers from the accelerometer of our smartphone. Suppose we start at a red light and accelerate at 2 m/s² (meters per second squared) for five seconds. From the above equation, Δv₁ It will be 2 x 5 = 10 m/s, so this is our speed. Now, after cruising for a while, we accelerate again at 1 m/s² For another five seconds. Δv₂ So 1 x 5 = 5 m/s. Adding these two changes, our speed is now 15 m/s. And so on.

The only problem is that inertial measurement is not as accurate as the Doppler method over long periods, because small errors will continue to accumulate. This means that you need to periodically recalibrate your system using another method.

Visual navigation

On Earth, people have long navigated through the stars. In the Northern Hemisphere, all you have to do is find Polaris. It is called the North Star because the Earth’s axis of rotation points directly to it. This is why it appears stationary, while other stars appear to revolve around it. If you point your finger at Polaris, it will point north, and you can use that direction to go in any direction you want.

Now, if you can measure the angle of Polaris above the horizon, you will also know your latitude. If the angle is 30 degrees, you are at 30 degrees latitude. See, it’s easy. Once you can measure the position, simply do it twice and record the time interval to find your speed.

But celestial navigation works because we know how the Earth rotates, and that doesn’t help with spacecraft. Well, can we use the stars like you use cows on the side of the road? no. The stars are so far away, astronauts would need to travel many generations to detect any shift in their positions. Like a plane flying over the sea, you feel steady, even while traveling at 25,000 miles per hour.

But we can still use the basic idea. For visual navigation in space, the spacecraft can determine the locations of other objects in the solar system. By knowing the exact location of these objects (which changes over time) and where they appear in relation to the viewer, it is possible to determine the position by triangulation. Again, by taking multiple spot measurements over time, you can calculate velocity.

Ultimately, although starships lack speedometers, it is possible to track their speed indirectly with a little physics. But it’s just another example of how to do it Flying in space is a completely different matter– And it’s more complicated – than driving or flying on the ground.