Thruster mechanics

Thruster Placement

Thrusters can be placed anywhere on a ship. Unlike in real-world physics, thrusters do not apply any torque to the ship. Instead, they apply linear thrust in the direction opposite the nozzle.

There is an exception to this, however. If a ship is docked to another ship or heavy cargo, via magnetic landing gear, the other object's mass can cause the ship to rotate under acceleration. For more information on this, and how to avoid it, see docking.

For example, you see the aft thrusters of a carrier firing in the image above. Even though these thrusters are mounted on pylons far below the center of mass, they will accelerate the carrier forward without causing it to rotate. However, if heavy ships are docked in the hangar bay, the aft thrusters may cause the carrier to pitch upwards when fired.

Enclosing thrusters

Thrusters require clear space to avoid damaging other objects. Exceptions to this are: small ship thrusters don't damage heavy armor blocks on Stations or Large Ships (so you can build landing platforms), and asteroids.

A  Small Thruster on a Small Ship destroys an area of 3x3x4 (width, height, depth) behind the exhaust, assuming the space is completely enclosed and filled. A small thruster is capable of dealing damage of up to 5 blocks depth over open space.

Prior to Update 01.022, thrusters did not require open space to function. It was possible to enclose a thruster on all six sides without impacting its performance.

This has been the subject of heated debate on the Space Engineers forum. Some users consider it a bug while others consider it a feature. Even so, it was heavily exploited by designers building replicas of famous sci-fi spacecraft. Many of these designs lack a sufficient number of exterior thrusters to move them, if they have any at all. Thruster Damage can be toggled on and off in world settings, causing enclosed thrusters to destroy the blocks behind them or allowing them to function safely.

Capacity

When active, inertial dampeners can use 100% of the maximum capacity of all necessary thrusters. However, when fired manually via the 'w', 'a', 's', or 'd' keys, thrusters will only operate at 2/3 maximum capacity. The listed power and force ratings on the  Large Thruster and  Small Thruster pages reflect maximum capacity. When attempting calculations for a manual burn, remember to multiply these values by 2/3.

Calculating acceleration

According to physics, we know that force = mass x acceleration. Using algebra, we can then determine that acceleration = force / mass. But what does this mean, exactly?

Units

• Force: Newtons (N), 1 N = 1 kgm/s²
• Mass: Kilograms (kg)
• Acceleration: meters per second per second (m/s²)

Constants

• Thrusters only provide 2/3 of maximum power when manually fired.
• Inertial dampeners use thrusters' maximum power.
•  Small Thruster:
  • Small ship: 18,165 N maximum, 12,110 N on manual burn.
  • Large ship: 150,660 N maximum, 100,440 N on manual burn.
•  Large Thruster:
  • Small ship: 218,250 N maximum, 145,500 N on manual burn.
  • Large ship: 1,815,000 N maximum, 1,210,000 N on manual burn.

Equation

To calculate the acceleration of your ship, use the following formula:

$a= \frac{(N_l F_l + N_s F_s)}{m}$
Where:
$a$	: Acceleration (m s-2)
$N_l$	: Number of large thrusters
$F_l$	: Force of each large thruster (N)
$N_{s}$	: Number of small thrusters
$F_s$	: Force of each small thruster (N)
$m$	: Mass of the ship (kg)

Example

Let's assume we have a 15000kg small ship with one large thruster and four small ones pointing aft. We want to know how fast we'll accerate when we press 'w'.

Steps:
1.	Calculate small thruster force $N_s F_s = 4 \times 12,110 \text{N} = 48,440 \text{N}$
2.	Add the large thruster. $N_s F_s + N_l \times F_l = 48,440 \text{N} + 1 \times 145,500 = 193,940 \text{N}$
3.	Calculate acceleration. $a={\frac {193,940{\text{N}}}{15,000{\text{kg}}}}=12.93{\text{m}}{\text{s}}^{-2}$

Calculating time to velocity

Sometimes, it may be important to know how long it will take to accelerate to a particular speed. To calculate the amount this, you first need the rate of acceleration calculated above. Then, since we know that velocity = acceleration * time, you can use algebra to find the following equation:

Equation

$t=\frac {\Delta v} {a}$
$\Delta v=v_f - v_i$
Where:
$\Delta v$	: Change in velocity (m/s)
$a$	: Acceleration (m/s2)
$v_f$	: Final velocity (m/s)
$v_i$	: Initial velocity (m/s)

Example

Our ship in the previous example had an acceleration of 12.93 m/s². If we want to know how long it takes to accelerate from a stop up to the game's speed limit, we simply fill in the equation:

Steps:
1.	Get delta-v. $v=105 \text{m/s} - 0\text{m/s}$
2.	Calculate time. $t=\frac {105 \text{m/s} } { 12.93 \text{m/s}^2 } = 8.1 \text{s}$

Distance traveled

Another useful thing to know is how far you'll travel while accelerating. For example, if we plan on docking with a station or carrier, it's good to know exactly how close we can get before we have to start slowing down. For this, we need to know our initial velocity, our acceleration, and the time.

Equation

$d=v_it + \frac {at^2} {2}$
Where:
$d$	: Distance (m))
$v_i$	: Initial velocity (m/s)
$a$	: Acceleration (m/s2
$t$	: Time (s))

Example

Let's say we've got a small ship up near the speed limit at 100m/s. We want to slow down to about 10m/s in order to dock safely. Our ship isn't really designed for rapid deceleration, so our forward thrusters only generate an acceleration of 15m/s². (Note: since we're decelerating, we use -15m/s².)

Steps:
1.	Calculate how much time it'll take. $t=\frac {10\text{m/s} - 100\text{m/s} } {-15\text{m/s}^2}$
2.	$t=\frac {-90\text{m/s} } {-15\text{m/s}^2}$
3.	$t=6\text{s}$
4.	Then figure out how much distance we need. $d=100\text{m/s}(6\text{s}) + \frac {-15\text{m/s}^2 \ 6^2\text{s} } {2}$
5.	$d=600\text{m} + \frac {-15\text{m/s}^2 \ 36\text{s}^2} {2}$
6.	$d=600{\text{m}}+{\frac {-540{\text{m/s}}}{2}}$
7.	$d=600\text{m} - 270\text{m}$
8.	$d=330\text{m}$

So we need at least 330m to drop down to our safe speed.

When doing these calculations, it's important to remember that you get more power from inertial dampeners than from manual thrusters. It's even more important to remember your ship can have a different acceleration depending on how many thrusters point away from where you're moving.

Since most ships have more aft thrusters than fore thrusters, you can run into problems if you base all your calculations off aft inertial dampeners. You may well find yourself merging your hull into the side of a station.