Navball
The navball is one of the primary instruments to control the craft. Understanding the navball is critical to successful flight, both in space as in atmosphere. When the camera is not in chase mode only the navball can tell the current orientation and what the rotation commands will perform. It is similar to the artificial horizon used in real-world planes.
Contents
Point of reference
As all movement in space is relative. The point of reference determines the object from which all distance measurements and velocity vectors are made. Clicking this area will toggle the point of reference between Surface and Orbit, as indicated by the green text. If a target is selected, there is a third option, Target. Changing the point of reference changes the location of the prograde and retrograde markers (described below).
To land on the surface of a planet or other celestial body, it is important to have the reference set to Surface to account for the rotation of the celestial body. For orbital maneuvers (i.e., not landing), the planet's rotation is unimportant, except in the case of a synchronous orbit, in which case the point of reference should be set to Orbit, which is like Surface but without accounting for the planet's rotation.
Speed
Your speed is measured relative to the point of reference and is given in meters per second (m/s). Speed is never negative. Even when you're moving toward a target (as in a docking maneuver), your closing speed will always be shown as a positive number.
Ball instrument
The most important part is the center ball, which shows the current orientation of the craft and multiple directions which maybe important for future movements.
While on the ground, the blue background hemisphere indicates the skyward direction (up; away from the center of gravity), while brown indicates groundwards (down, towards gravity). The thin white line separating the blue and brown hemispheres is the artificial horizon. These indicators are relative to the part from which the craft is controlled, not necessarily the nearest planet, target, or orbital plane. This can be changed by selecting Control from Here when right-clicking on docking ports or command modules that may be on the craft.
Level indicator
The level indicator is the gold V-shape in the center of the navball, which shows the direction the craft is facing (its orientation). The level indicator never moves; the navball rotates beneath it, providing a kind of cockpit window view without any window needed. For example, rotating the craft around its roll axis will turn the navball upside down.
Markers
On the navball are three different types of markers. All markers except the maneuver marker come in pairs, with an opposite marker on the opposite side of the virtual ball.
Prograde and retrograde
The green prograde marker indicates the direction of movement (which may not be the direction the craft is facing). Conversely, the green retrograde marker always faces in exactly the opposite direction; the direction the craft has come from. If the prograde marker is exactly aligned with the gold level indicator, the craft is facing "forwards" in the direction of travel. As the craft orbits around a body, these markers will gradually move, because orbits are circular (or elliptical), while orbiting spacecraft typically hold still. Burning in the prograde direction will accelerate the craft, while burning retrograde will slow it down. Burning in any direction other than exactly prograde or retrograde will cause the prograde/retrograde markers to move toward/away from the direction the craft is pointing. These markers are relative to the point of reference.
Target prograde and target retrograde
If a target is selected, the purple icons will indicate the heading directly to the target. Because the target is typically moving, the target markers move as well. Usually the target marker and velocity marker don't follow exactly the same path and tend to drift away. This is important for docking, which requires frequent input to hold the craft on course. These markers are not relative to the point of reference.
Maneuver prograde
If a maneuver is planned on the map, the blue Maneuver marker points in the direction needed for the burn. This is the only marker without an opposite pair.
Symbols on the ball instrument
Level indicator
Prograde
Retrograde
Target prograde
Target retrograde
Maneuver prograde
Information around
On maneuvers, there is a maneuver Δv indicator, a green bar and small info text right of the navball. The bar indicates the total amount Δv required in the maneuver direction and it will deplete as the burn is performed. Below that is indicated how long the burn will have to continue until the maneuver is completed. This is a mere estimation based on the current maximum thrust available. When engines get activated or deactivated this value will adjust instantly and may result in a longer burn time. It won't change when the engines run at a lower thrust level but simply reduce slower. Below that is a timer indicating the time left until the craft reaches the maneuver node. It is unclear when to start the burn:
- Start prior to the maneuver so that it finishes on T-0
- Start halfway through so that it half of the maneuver's Δv is applied on T-0
- Start the maneuver on T-0
Throttle
Throttle is at how much power all engines are running (in percent). Beware of full throttle, as engines can overheat and then can be destroyed. This throttle will always control all engines, so if the engines are not balanced there is no way to balance this by reducing the power for those engines which apply to much thrust. Also it controls the engines equally at the given percentage so smaller engines will apply lower force. It can't throttle solid rocket boosters.
Heading
The heading is the direction in degrees that the craft is facing. As most bodies are rotating eastwards it is more fuel efficent to head at the east.
G forces
G forces are the pressures exerted due to acceleration measured in a factor of g. One g is approximately 9.81 m/s2. Not to be confused with the SI-unit gram.
Hide
Clicking the little arrow on the top of the navball (Hide) will toggles its display on-screen.
Basic controls
These are the most basic orientation controls of the craft, here is a short explanation on how their actions are represented on the navball with the default key bindings:
- W moves the indicator down on the navball.
- S moves it up.
- A moves it left.
- D moves it right.
- Q rolls it counterclockwise.
- E rolls it clockwise.
