course_planning:184_projects:s18_project_7 [Projects & Practices in Physics]

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===== Project 7 =====

==== Project 7A: Artemis's Last Hope ====
After you stabilized Spurgeon, team leader Melissa Lewis decides Artemis 13 needs to go home before anything else happens. Just as she gives the order to rotate boosters in order to send the ship home the crew feels the spacecraft rock violently and warning lights start going off everywhere. The command ship starts to lose all of its power. After a quick investigation, it turns out that the circuit that controls all of the key systems is currently drawing too much current from the battery. You are in constant communication with Austin about the issues you are encountering and a bright but intense intern proposes a risky but possibly brilliant solution. They want to take two batteries from the mostly dead Command Ship and use them to help power the Artemis. In addition to the 230 V main battery, they say they need 140 V ($V_{bat1}$) from the Command Ship battery and only 5 V ($V_{bat2}$) from the backup battery to get them home. From the ship manual you find the following resistances for different components that need to be powered in order to get you all home: 
  * Gauge Lights: $R_{GL}=100\Omega$
  * Navigation System: $R_{NS}=700\Omega$ 
  * Steering/Direction Control: $R_{SDC}=950\Omega$ 
  * Engine Cooling System: $R_{ECS}=500\Omega$ 
  * Air Filter: $R_{AF}=300\Omega$ 
  * Waste Management System: $R_{WMS}=425\Omega$

{{  184_notes:project7a.png?550 }}

Will this circuit work without drawing any more than the 0.35 A from the main battery?

==== Project 7B: Power Is Everything ====

The Artemis 13 was able to turn on its boosters and move the craft towards home. Since power is in short supply, several non-vital systems were shut down. However, to successfully go through the landing sequence they MUST turn on the guidance computer system (GCS), Environmental Control Systems (ECS), Communications Relay (CR), the warm-up control for the primers for the parachutes (PP), and the Command Control Module (CCM), as well as a floodlight (FL) in the cockpit using only the main battery (230 V). 

Your team on the ground has been working in a simulator to figure out how to turn on each of the systems in various orders, but keeps running into problems. If the total current from the main battery on board exceeds 0.35 A, the battery will die and the Artemis will lose power before it can return safely to Earth. Your flight expert has sent over the most recent steps he has tried and the data they collected for each step. 

  - Turn on only the CR, which seems to work properly and only draws 0.242 A from the battery.
  - Then turn on the PP, which decreases the current from the battery. The CR seems to barely be functioning so you conclude that it is running at it's minimum power of 18.35 W.
  - Next they turned everything off, and switched on only the PP and the FL. Immediately the warning light goes off in the simulator because the current from the battery is way too high at 1.48 A and the flood light has burnt out because the power in the bulb was 264.6 W (exceeding their maximum power rating of 120 W).
  - You decide to start over and turn everything off again. You turn on the GCS, ECS, and CCM - which seems to be perfectly alright. The current from the battery is maintaining at a nice and safe 0.188 A. Since this combination works well, you grab the hand-dandy multimeter and find that the GCS, ECS, and CCM have the same current but that the GCS is using the most power (17.7 W) and the ECS is using the least (10.6 W).
  - Just to try one more thing, they turn everything off and then turn on only the PP and the GCS. You find that even though they have the same voltage the current going through these elements are different.
 
Mission Control wants to try to turn everything on at once as it is currently configured. They are running out of time and need to get something to the Artemis. Will the current configuration of these elements in a circuit allow the Artemis 13 to get home safely??

<WRAP info>
=== Learning Goals ===
  * Use resistor combination rules, loop rule, and node rule to determine the circuit set up.
  * Calculate the equivalent resistance of a circuit.
</WRAP>