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Chapter 3 - Main Reactor

In this chapter, you will get your main reactor systems online by combining your knowledge about functions, operators and conditional statements.

To do that, you will need to

  • understand how to write and how to call functions
  • be able to write if and if else statements
  • know some functions from the Math library:
    • Math.min and
    • Math.max will be very helpful.

Finding the source code

The JavaScript filepath for this lesson is 

src/mainReactor.js

Go on and open it up in your editor.

Challenges

A nice, warm breeze makes its way unto the bridge as the life support systems pick back up from where they left off, bringing a faint smell of air refreshener with it. The backup reactor seems to be perfectly able to handle the current power drain and keep the lights on.

You let yourself relax a bit, knowing that any immediate danger has past.

The next step will be bringing the main reactor back online, a tricky undertaking since you really don't want it to go critical and blow up. As you scan the designs, you come across a set of simulations that were written to check the reactor for safe operations. That's going to be helpful.

The solar flare has wiped a total of four functions off the reactor handling procedures. They seem to be interconnected and based upon some reactor control subroutines that are luckily still there.

The first thing that's missing is just the calculation logic for summing up the total current power output from both the main reactor and the backup reactor. Next up is a function for checking whether the power draw is within tolerance of the produced power. The emergency shutdown sequence itself is still functional, but the code that is supposed to call it is gone. And finally, you'll need to write the logic handling the power generation for both the main and the backup reactor. This is where the simulations will come in handy.

Calculate the total power output

Find the function getTotalPowerOutput. It does not take any parameters. Instead, it's intended to gain all values it needs from two functions in the coreSystem/reactorControl code. These are already written functions that you can simply call from withing getTotalPowerOutput.

The two functions are getMainReactorOutput and getBackupReactorOutput. Both do not take any parameters. Your function should return the sum of the return values of these two functions.

Explanation: These functions return global states that are set in the testing procedure. So, before the testing scripts call getTotalPowerOutput(), they update an internal state. Whenever you call getMainReactorOutput() or getBackupReactorOutput(), this internal state is then returned. All functions you have to write in this session use this kind of logic.

Establish whether the power output is within tolerance

After having written the calculation logic for the total power output, you read over the technical definitions of your reactors.

Your backup reactor can produce between 0 and 10 power, and is never critical.

Your main reactor can produce between 0 and 50 power, and goes critical whenever it produces more power than is drawn from your ship systems.

Ship systems always draw from the main reactor first, and only then from the backup reactor.

You can get the current power draw of your ship systems from another function in the coreSystems/reactorControl scripts. This one is called getPowerDraw, takes no parameters and returns the current power draw as a numeric value.

Complete the function isPowerOutputInTolerance. It takes no parameters and returns a boolean value: true if the current power output is okay, false if the current power output is critical.

Examples: Assuming a main reactor output of 20 and a backup reactor output of 5:

  • For a power draw of 25, your function should return true.
    • All power produced is used, so the main reactor is not critical.
  • For a power draw of 30, your function should return true.
    • All power produced is used, so the main reactor is not critical. 5 power less than required from ship systems is produced, which means not everything will be running, but the reactor is fine.
  • For a power draw of 20, your function should return true.
    • Not all power produced is used. But the power from the main reactor is used first, so all 20 power from the main reactor is drawn. The 5 extra power from the backup reactor are not used, but the backup reactor never goes critical, so all is good.
  • For a power draw of 18, your function should return false.
    • Not all power produced is used, and not even all 20 power that the main reactor produces is used. This will cause the main reactor to go critical.

Shut down the main reactor if necessary

Now that you have a test for whether the power output is within tolerance, you can make use of that to reimplement the functionality to automatically shut down the main reactor if needed.

Your pretty sure that this function saved you when the solar flare hit, otherwise the reactor might have blown. Too bad the code has been erased, but you'll just have to rewrite it.

Find the function called performEmergencyShutdownIfNecessary. It does not take any parameters, and is not expected to return anything. Instead, make use of your isPowerOutputInTolerance function to test whether the reactor should shut down, and call shutDownReactor from the coreSystems/reactorControl scripts if needed. shutDownReactor does not take any parameters and also does not return anything.

Adjusting power generation

You're almost done with the main reactor systems, but the hardest part is still left to do. This one might take some thining and some testing. You read through the reactor guidelines, once more, and write down these rules for your program:

  • The main reactor can produce between 0 and 50 power.
  • The backup reactor can produce between 0 and 10 power.
  • All power from the main reactor must be used, or it needs to perform an emergency shutdown.
  • The main reactor output can only change between -10 to +10 in one step.
  • The backup reactor can always be set to any number between 0 and 10.
  • If possible, all power needed by the ship systems should also be provided.

You look at the simulations and add one in for simulating a solar flare. Some of them are pretty complicated and are not needed right away, but you might want to try your hand on them anyway. So you've added a constant, runAdvancedSimulations, to toggle them on or off.

With everything being prepared, you set yourself down to write that power adjustment script. Find the function called adjustReactorSystems. It does not take a parameter, and is not expected to return any value. Instead, it should call the functions adjustMainReactorOutput and adjustBackupReactorOutput from the coreSystems/reactorControl scripts. Both of these functions take one numeric parameter and do not return anything. When called, the functions check whether the value you are providing for the respective reactor is valid and then update the reactor output.

Your goal is to write logic that will correctly set the power output of the main and the backup reactor using these two functions. To do so, you will need to know the current power draw, which will be changing between calls to adjustReactorSystems and which you can get by calling getPowerDraw, as you did for the power tolerance calculations. You might also have to reuse getMainReactorOutput and getBackupReactorOutput to implement the change between -10 and +10 rule. Finally, don't forget to shut down the reactor if it becomes necessary - you should be able to reuse your performEmergencyShutdownIfNecessary function.

Explanation: The testing scripts contain two simulations, Simulation 1: Interplanetary flight and Simulation 2: Emergency shutdown after flare, that your function implementaiton needs to be able to handle. These simulations start off by setting values for the starting output of the main and backup reactor as well as the current power draw, and then go through a series of steps where they

  • set a new power draw
  • call adjustReactorSystems
  • check that all systems are powered, and
  • check that the reactor status is as expected (online or offline).

In other words, the global state of the reactor and ship systems is going to change in between calls to adjustReactorSystems, so you'll need to read that state, calculate the correct power settings, and set them via adjustMainReactorOutput and adjustBackupReactorOutput.

Hint: This is by far the trickiest problem you have encountered in this course so far. Feel extra free to ask for help. The intention of this problem is to tie everything you have learned so far together, and to really write some clever code. It's fine if it takes you a while, but don't wait to get help until you're frustrated.

Hint hint: The Math.min and Math.max functions could be very useful here.

Hint hint hint: If you finished the example, you can change runAdvancedSimulations to true to see if your reactor script can also handle the Simulation 3: Highly dynamic power draw and Simulation 4: Full utilization tests.

Next steps

This is the end of the main reactor lesson. The next lesson is still in preparation and will come online soon.