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        <a href="/"><h1>drones :)</h1></a>
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        <h1>Drones 101</h1><hr/>
        <h2>What is a Drone?</h2> 
        <p><b>An unmanned aerial vehicle</b>, commonly known as a <b>drone</b>, 
        is an aircraft without a human pilot aboard. Today the term drone has 
        broadened to include anything from the expensive 100 million USD war 
        machines :-( to few hundreds dollar octocopters which Amazon used to 
        deliver packages :-) </p>
        <br/>
        <h2>How do they work?</h2>
        <p>They are many types of drones, so let’s talk about drones that have 
        propellers. A drone with four propellers is called <b>quadcopter</b>, 
        the one with eight propellers is called <b>octocopter</b>, and so on. 
        The propellers on a drone is controlled by a <b>microcontroller</b>, a 
        microcontroller processes the signals received from its data buses, and 
        make responses based on the procedures programmed into the memory of a 
        microcontroller. In order words, a microcontroller is a digital computer 
        that tells each propeller on a drone exactly what to do. However, having a 
        digital computer is not enough, since we’ll have to deal with lots of 
        <b>physics</b> in order to fly a drone in real life. Basically, a drone 
        will not even take off without <b>the power of physics.</b></p>
        <br/>
        <h2>Physics of a Drone:</h3>
        <br/>
        <h3>Basics</h3>
        <p>First we can simplify the problem into a simple diagram known as 
        <b>free-body diagram</b> before getting into problems like "how does a 
        drone fly?" Let’s take Amazon’s drone as an example, the machine will weigh
        5.5 kg with a battery wright of around 2.2 kg, so the total mass of the 
        drone is 7.7kg:</p>
        <img src="./lib/img/01.png" alt=""></img>
        <p>Imagine the box shown above is the simplest form of the drone. We know 
        that it has a mass of 7.7kg and a weight force pulling it down due to 
        earth’s gravitational acceleration about 77 newtons. Weight force can be 
        calculate using <b>Newton’s Second Law</b>, that is, <code>F = ma</code>. 
        Where <code>m</code> is the mass and <code>a</code> is the acceleration:
        </p>
        <img src="./lib/img/02.png" alt="F = ma"></img>
        <p>Now, we know that in order to overcome gravity, it is necessary to 
        generate a force that is greater than 77 newtons. This can be accomplished 
        easily by using propellers. The basic idea is that a drone flies by pushing
        air down. When the propellers of a drone pushes air dow, the drone hovers.
        This is because of <b>Newton’s Third Law</b>, which is often stated as  
        “for every action there’s an equal and opposite reaction”:</p>
        <img src="./lib/img/03.png" alt=""></img>
        <p><i>/* the blue part is the air pushing down by the propeller 
          disks */</i></p>
        <br/>
        <h3>Buoyancy</h3>
        <p>The weight force we got here is 77 newtons; however, the 
        <b>apparent weight</b> might be slightly smaller due to the buoyancy 
        of the air. We can calculate the apparent weight by subtracting the 
        <b>buoyant force</b> from the weight force:</p>
        <img src="./lib/img/04.png" alt=""></img>
        <p>The equation for force of buoyancy is:</p>
        <img src="./lib/img/05.png" alt=""></img>
        <p>Where the density of the air is:</p>
        <img src="./lib/img/06.png" alt=""></img>
        <p>Now, we can work out the apparent weight, but since I couldn’t find 
        the <b>volume</b> of Amazon’s drone, let’s assume it’s
        0.0015 m^3 (1.5 liters). Finally we will get around 76.9 newtons of 
        apparent weight:</p>
        <img src="./lib/img/07.png" alt=""></img>
        <p><br/></p>
        <h3>Thrust Produces by Propellers</h3>
        <img src="./lib/img/08.png" alt=""></img>
        <p>A <b>drone</b> hovers because of the thrust produces by the propellers. 
        A spinning propeller sets up a pressure <b>lower</b> than free stream 
        on the top of a propeller and <b>higher</b> than free stream behind 
        the propeller. Downstream of the disk the pressure eventually returns 
        to free stream condition. The thrust produces by a propeller can be model 
        by this equation:</p>
        <img src="./lib/img/09.png" alt=""></img>
        <p>Where <code>A</code> is the area of the propeller disks and 
        <code>∆P</code> is the change in pressure.</p>
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<commit_msg>fix broken link<commit_after><!DOCTYPE html>
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    <meta charset='utf-8'>
    <meta http-equiv="Content-Language" content="en">
    <link rel="stylesheet" type="text/css" href="./lib/css/main.css">
    <title>Physics: Drones</title>
  </head>
  <body>
    <div class="wrapper">
      <div class="header">
        <a href="/"><h1>drones :)</h1></a>
      </div>
      <div class="nav">
        <ul>
          <li><a href="./" style="color: red;">frontpage</a></li>
          <li><span class="separator">|</span></li>
          <li><a href="./simulation/">simulation</a></li>
          <li><span class="separator">|</span></li>
          <li><a href="./about/">about</a></li>
        </ul>
      </div>
      <div class="body">
        <h1>Drones 101</h1><hr/>
        <h2>What is a Drone?</h2> 
        <p><b>An unmanned aerial vehicle</b>, commonly known as a <b>drone</b>, 
        is an aircraft without a human pilot aboard. Today the term drone has 
        broadened to include anything from the expensive 100 million USD war 
        machines :-( to few hundreds dollar octocopters which Amazon used to 
        deliver packages :-) </p>
        <br/>
        <h2>How do they work?</h2>
        <p>They are many types of drones, so let’s talk about drones that have 
        propellers. A drone with four propellers is called <b>quadcopter</b>, 
        the one with eight propellers is called <b>octocopter</b>, and so on. 
        The propellers on a drone is controlled by a <b>microcontroller</b>, a 
        microcontroller processes the signals received from its data buses, and 
        make responses based on the procedures programmed into the memory of a 
        microcontroller. In order words, a microcontroller is a digital computer 
        that tells each propeller on a drone exactly what to do. However, having a 
        digital computer is not enough, since we’ll have to deal with lots of 
        <b>physics</b> in order to fly a drone in real life. Basically, a drone 
        will not even take off without <b>the power of physics.</b></p>
        <br/>
        <h2>Physics of a Drone:</h3>
        <br/>
        <h3>Basics</h3>
        <p>First we can simplify the problem into a simple diagram known as 
        <b>free-body diagram</b> before getting into problems like "how does a 
        drone fly?" Let’s take Amazon’s drone as an example, the machine will weigh
        5.5 kg with a battery wright of around 2.2 kg, so the total mass of the 
        drone is 7.7kg:</p>
        <img src="./lib/img/01.png" alt=""></img>
        <p>Imagine the box shown above is the simplest form of the drone. We know 
        that it has a mass of 7.7kg and a weight force pulling it down due to 
        earth’s gravitational acceleration about 77 newtons. Weight force can be 
        calculate using <b>Newton’s Second Law</b>, that is, <code>F = ma</code>. 
        Where <code>m</code> is the mass and <code>a</code> is the acceleration:
        </p>
        <img src="./lib/img/02.png" alt="F = ma"></img>
        <p>Now, we know that in order to overcome gravity, it is necessary to 
        generate a force that is greater than 77 newtons. This can be accomplished 
        easily by using propellers. The basic idea is that a drone flies by pushing
        air down. When the propellers of a drone pushes air dow, the drone hovers.
        This is because of <b>Newton’s Third Law</b>, which is often stated as  
        “for every action there’s an equal and opposite reaction”:</p>
        <img src="./lib/img/03.png" alt=""></img>
        <p><i>/* the blue part is the air pushing down by the propeller 
          disks */</i></p>
        <br/>
        <h3>Buoyancy</h3>
        <p>The weight force we got here is 77 newtons; however, the 
        <b>apparent weight</b> might be slightly smaller due to the buoyancy 
        of the air. We can calculate the apparent weight by subtracting the 
        <b>buoyant force</b> from the weight force:</p>
        <img src="./lib/img/04.png" alt=""></img>
        <p>The equation for force of buoyancy is:</p>
        <img src="./lib/img/05.png" alt=""></img>
        <p>Where the density of the air is:</p>
        <img src="./lib/img/06.png" alt=""></img>
        <p>Now, we can work out the apparent weight, but since I couldn’t find 
        the <b>volume</b> of Amazon’s drone, let’s assume it’s
        0.0015 m^3 (1.5 liters). Finally we will get around 76.9 newtons of 
        apparent weight:</p>
        <img src="./lib/img/07.png" alt=""></img>
        <p><br/></p>
        <h3>Thrust Produces by Propellers</h3>
        <img src="./lib/img/08.png" alt=""></img>
        <p>A <b>drone</b> hovers because of the thrust produces by the propellers. 
        A spinning propeller sets up a pressure <b>lower</b> than free stream 
        on the top of a propeller and <b>higher</b> than free stream behind 
        the propeller. Downstream of the disk the pressure eventually returns 
        to free stream condition. The thrust produces by a propeller can be model 
        by this equation:</p>
        <img src="./lib/img/09.png" alt=""></img>
        <p>Where <code>A</code> is the area of the propeller disks and 
        <code>∆P</code> is the change in pressure.</p>
      </div>
      <div class="footer">
        <p>
          The Site is Licensed Under the
          <a href="https://raw.githubusercontent.com/ssiscsc/ssiscsc.github.io/master/LICENSE">
            MIT License.</a>
        </p>
      </div>
    </div>
  </body>
</html>

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