# How do you place a satellite in orbit?

With all the media frenzy about Spacex over the days we received a few requests asking us to explain how satellites are launched into orbit.

We shall do so through a thought experiment proposed by Isaac Newton when he was trying to understand how the moon was orbiting the earth.

## Newton’s cannonball

Just imagine standing on top of a really tall mountain with some cannonballs and a cannon.

We will start firing these cannon balls with different speeds by constantly increasing the amount of firepowder that we add and observing the response.

(a) Speed of cannonball < 7300 m/s

(b) Speed of cannonball ~7300 m/s —-> Circular orbit

( c) Speed of cannonball ~8000 m/s —-> Elliptical orbit

(d) Speed of cannonball ~11200 m/s —-> Parabolic trajectory

(e) Speed of cannonball – Crazy

## Gunpowders are not that powerful !

In the real world instead of using gun powder, we use much more sophisticated and powerful
solid rocket fuels which will take the satellite from earth and put it
in orbit.

But once the satellite once put in orbit just keeps falling into orbit.

This applies to the ISS as well: “ISS is always falling; Falling into orbit.

Although this is not by any means a comprehensive post on this topic, but hopefully this gives you a sense of the physics of how satellites are placed in orbit.

Have a good one!

** TRY IT OUT – Newton’s Cannon

Yes, sure its fun to see a lady spin around like that, but I had one of my friends ask me – “Where do you even use this mate?”

Here’s one application that I know very well off.

## Spin Stabilization

If you have ever seen a rocket launch, you might know that sometimes the rockets are given a spin while launching. This is known as spin stabilization.

Basically, the rotational inertia of the rotating body will stabilize the rocket against any disturbances and help maintain its intended heading.

The same principle is used in rifling of firearms as well. **

## YoYo DeSpin

Okay, now there is the question how to “De-spin” the rocket:

Well, you do what the lady does: stretch out your arms and you will slow down !

The rocket has weights connected to a cable that stretch out and almost immediately the rocket slows down. This maneuver is known as the YoYo DeSpin. ( Damn good name ! )

All thanks to the conservation of angular momentum !

Have a good one !

* Another method to stabilization : 3-axis stabilization

## Water droplets orbiting a needle in space.

This marvelous display of physics unfolded when tiny charged droplets of water were fired through a syringe towards a needle which was also statically charged. This experiment was conducted at the ISS in 2012.

The droplets remarkably began to orbit the needle, just like some satellites do around a cylindrical planet!

It’s the ISS and things float so, nothing exquisite about that but this demonstration is to illustrate the attraction of charged objects in space..

## What is this sorcery?

Since the water droplets and the needle are charged, the droplets are attracted to the needle. But hey, those drops also have some velocity, so they end up orbiting the needle instead of sticking right to it.

How cool is that?

Image Credit: NASA

# The Miura Fold

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The Miura fold is a method of folding a flat surface such as a sheet of paper into a smaller area. The fold is named for its inventor, Japanese astrophysicist Koryo Miura.

## Why it is awesome?

The Miura fold is a form of rigid origami, meaning that the fold can be carried out by a continuous motion in which, at each step, each parallelogram is completely flat.

This property allows it to be used to fold surfaces made of rigid materials; for instance, it has been used to simulate large solar panel arrays for space satellites in the Japanese space program.

The fold can also be unpacked in just one motion by pulling on opposite ends of the folded material, and likewise folded again by pushing the two ends back together.

In the application to solar arrays, this property reduces the number of motors required to unfold this shape, reducing the overall weight and complexity of the mechanism.

## Other cool stuff.

Miura folded maps. Snug it into your pocket when not in need and open it up in style when you are lost !