Embedded Files
In this unit, our task was to orbit around a planet called Kerbin. It would seem all one had to do was launch their rocket and let it do its thing. Wrong! Thanks to Newton we know that there are three laws that affect the rocket. His first law is "an object at rest tends to stay at rest, and objects in motion tend to stay in motion unless an unbalanced force acts on it." When the rocket is sitting on the launch pad, it will not start moving without an external force acting on it. The external force the rocket uses is called thrust allowing it to move upward. Not only does the rocket have to produce thrust, it has to produce enough thrust to overcome gravity and air resistance. Newton's second law is "force = mass * acceleration." We have learned that weight is a force, but gravity is not. Instead gravity is an acceleration and when multiplied by the rocket's mass, it equals the weight of the rocket. Newton's third law is "for every action, there exists an equal and opposite reaction." There is a force called the normal force which equals the force down on a surface. As the rocket sits on the launch pad, it pushes down like someone pushing down on a table, and the rocket stays there just like the person's hand doesn't go through the table.
We built two rockets. Our first rocket had solid propulsion which cannot be controlled once activated but is simple to use. The second rocket had liquid propulsion which the gas flow can be increased, decreased, or stopped but is more complex than solid propulsion. Both were not SSTO crafts (Single Stage to Orbit, a craft that achieves orbit without any detaching parts). A few instruments that were essential to launching include the altimeter (showing the height of the rocket off the ground), the atmospheric density (showing the thickness of the atmosphere around the rocket), and the WASD keys (change roll/pitch/yaw). Also, on the navball there are indicators for the orbital speed (showing the velocity of the rocket relative to the surface of the planet) and for the throttle, all which came in handy when launching. After hitting the spacebar to launch, we tried to keep our orbital speed at around 150 m/s - 200 m/s so that we would have enough fuel. To throttle up or down we needed to press the left shift key and left control key respectively. Around 10,000 meters we had to use the WASD keys to point the rocket's nose along the 90 degree line at 45 degrees inclination where we saw this on the navball. After our fuel ran out, we jettisoned our engines and throttled up our new engine. Using the M key we returned to Map Mode. There we watched our apoapsis, the point at which an orbiting object is farthest away from the body it is orbiting, reach 100,000m and then press the X key to kill all engines. At that apoapsis mark we created a maneuver to change our trajectory. By changing our trajectory, we had to be aware of the Oberth Effect, principle based on gravitational fields that states that since gravity grows stronger the closer you get to an object, that it requires more delta V to alter your trajectory inward the closer you are to a planet and the most when you're at the periapsis, the point at which an orbiting object is closest to the body it is orbiting and vice-versa. Our navball told us our delta V, the measure of the amount of "effort" that is needed to change from one trajectory to another. We were also told our "Node in T-" time. After it reached about 15 seconds, we prograded, burning in the direction you ARE going, and our delta V started going down. When it reached close to zero we killed all engines once again and we successfully orbited. Although I didn't land, I know that I would have to retrograde, burning in the opposite direction you are going to slow you down.
This unit has been a challenge but fun to tackle. It took some extra time in the engineering room and time at home on the demo version to accomplish orbiting. However, it opened my eyes to a new field of engineering that might be interesting to explore.
Report abuse