# Planetary Entry/Exit

This page is a guide for Engineers struggling to figure out whether their craft can safely leave or land on a planetary body, without having to do brute force trial and error. It will require the engineer to do some Basic math.

First, we must look at the basic variables Space Engineers works with. These are 1) Mass (measured in kilograms or kg ) 2) Planetary Gravity (measured in g) 3) Force (measured in Newtons and KiloNewtons)

Mass is automatically calculated for the craft as long as it is piloted. Even cargo components have mass in Space Engineers, but don’t worry: it is automatically calculated for the Engineer in the Info tab and in the pilot Heads-Up-Display. It is measured in kg.

Planetary gravity is a little bit more tricky. Although the game tends to measure it in ”g.” It should be noted that this is an implied physics ”g”. Meaning it is a gravtional porption relative to Earth’s gravity constant. This means Earth’s gravitational pull is 9.81 m/s^{2} or 9.81 meters per second squared. In this guide we will need the m/s^{2} acceleration of the current planet you are on.

Step 1: Find the Engineer standing surface g of the Planetary body you are attempting to Land or Exit from. Then convert that g into a meter per second squared number we can use. This number results in a meters per second squared number we can use. Don’t panic, for the sake of this tutorial we will not be altering the m/s^{2} variable; just pretend it is any other measurement.

The last variable we need is the thruster force. This number is the hardest of the variables to get, additionally the only thrusters that matter are the ones to be pointed in the direction of the planet. So calculating all your thrusters force is pointless. Furthermore, Ion Thrusters and Atmospheric thrusters Force output changes with altitude. Generally speaking if Atmospheric and Ion thrusters are used do not expect to get maximum force out of them in an atmosphere above 3,000 meters rendering it too late to reach 0 velocity or 0 m/s^{2}.

Step 2: Find the sum force of all thrusters used for braking/ resisting gravity.

To do this turn the thrusters off then, then go to a thruster control and then to the override force. Pull the bar all the way to the right. This will tell you the thrust force of that thruster in Newtons or KiloNewtons (Newtons *1,000). Reset the altered thruster to zero again, this will prevent it from static firing. The principle idea is that you sum all the thrusters you are using. Caution! A common mistake is to add up all the thrusters forces, but some thrusters’ force are measured in KiloNewtons NOT newtons. One KiloNewton is equal to 1,000 newtons. This is critical to understand.

Step 3: Setup the formula and double check your ship weight, and thrusters’ force.

It should look something like:

Planet’s gravity strength * Loaded ship mass in kg vs. Spacecraft’s Thruster force in Newtons.

Step 4: Plug 'n' chug both sides of the equation independently. That is calculate Planet’s gravity strength multiplied by the mass of the ship in kg. This is because Earth’s gravity is measured in newtons and pulls on this mass so many meters per second squared.

Step 5: Compare your final two numbers.

Gravity‘s pull on your vessel vs. Your vessel’s thruster force.

Outcome 1) Gravity’s pull on your vessel is > My vessel’s thruster force in Newtons.

Meaning: Your ship will crash or won’t lift from the planet.

Outcome 2) Gravity’s pull on your vessel is < My vessel’s thruster force in Newtons.

Meaning: Your ship will lift and fly through the atmosphere.

Outcome 3) Gravity’s pull on your vessel is = My vessel’s thruster force in Newtons.

Meaning: Your vessel will hover at it’s current altitude or glide/ fall down on its weak thruster side.

Warning!

This guide is for thruster force prediction. It does not include power consumption, fuel consumption, or gyroscope failure.