Frequently Asked Questions.

When you download Orbiter, you get a zip file (such as orbiter060929_base.zip) which contains all the program and data files required to install and run Orbiter. Unlike some other software packages, Orbiter does not come with a utility that performs the program installation. Instead, all you have to do is to unpack the zip file into a directory of your choice. (To do this, you need an unzip utility such as winzip.) This may look a bit inconvenient at first, but it has some distinct advantages:

• Orbiter does not modify any of your Windows system files or registry entries, so there is no installer required to perform behind-the-scenes magic without the user's consent. Orbiter installation is completely transparent, and all you get is a new directory, containing the complete Orbiter installation.
• This also means that multiple Orbiter installations can coexist on the same computer in different directories, without interfering with each other. This is particularly useful if you want to try new addons without compromising your stable Orbiter installation, or if you want to maintain different Orbiter "themes", for example a "realistic" and a "science fiction" Orbiter installation.
• Orbiter uninstallation is equally simple: Just delete the Orbiter folder with all files and subdirectories. No need for a dedicated de-installation utility that may leave residual files behind or corrupt the registry.

Once you have unpacked the Orbiter download file, just double-click on the "orbiter.exe" entry in the main orbiter directory to launch Orbiter. For quick access, you can also create a shortcut for orbiter.exe and copy it to your Windows desktop.

Sometimes this problem occurs if a new version is installed over an old one. It is strongly recommended to always install new versions from scratch into a new directory rather than overwriting an existing installation. Installing from scratch can also solve problems caused by addons which are no longer compatible with a new version. If you suspect a problem may be caused by an addon, re-install your addons one at a time and see whether you can identify the culprit. If you can, you may consider notifying the author of the addon.
Multiple Orbiter installations can co-exist on the same computer, so it is a good idea to keep your old Orbiter version to fall back on, in case you can't get the latest version to work on your system.

This problem usually occurs if you forget to restore the Orbiter directory tree when extracting the packages. When using WinZip or a similar utility to unpack the Orbiter packages, you need to activate the "Use folder names" option (or an equivalent option to that effect). After unpacking the Base and Textures packages, your Orbiter root directory should contain (amongst other things):

• The orbiter executable (Orbiter.exe)
• A number of subdirectories, including Meshes, Scenarios, Textures

If all files ended up in a single directory, you made a mistake when unpacking.

ORBITER loads a large number of texture maps (mainly planetary surfaces) during startup. Loading these maps will be very slow if your graphics card does not support texture compression, because textures must then be decompressed on the fly. To reduce the loading time (and the amount of memory required for textures):

• Disable high-resolution textures if you have any. High-resolution textures are located in the Textures2 subdirectory. The easiest way to disable them is to rename the directory. Orbiter will then use the lower-resolution textures in the Textures directory.
• Turn off visual effects in the "Visual effects" tab of the Orbiter Launchpad dialog. In particular the Cloud layers and Specular water reflections options are texture-intensive.

Make sure you have selected a hardware render device in the "Video" tab of the Orbiter Launchpad dialog (for example "Direct3D HAL T&L"). Avoid the much slower software devices, such as "RGB Emulation". If possible, use a hardware transform and lighting (T&L) device.

Apart from that, all the usual advice for performance-critical simulations applies: Quit other programs running simultaneously (either in the foreground, or as background jobs). On computers with low-end graphics run Orbiter in fullscreen mode, use a lower screen resolution and lower colour depth (16 bit). Reduce the level of "eye-candy" by turning off the options under the "Visual effects" tab of the Orbiter Launchpad.

Make sure you have DirectX7 or higher installed.
Make sure your system meets the requirements specified in the Download page.
Make sure that you have installed Orbiter correctly.
Make sure that you have configured Orbiter correctly - in particular that the options under the "Video" tab of the Orbiter Launchpad are properly set.
The Orbiter.log file might contain information about what is going wrong.

Make sure you have enabled the joystick in the "Joystick" tab of the Orbiter Launchpad dialog.
The joystick is usually mapped to the reaction control system (RCS) or aerodynamic control surfaces of your spacecraft, so remember:

• In vacuum, aerodynamic control surfaces obviously have no effect - the spacecraft orientation can only be controlled with the RCS.
• Conversely, in a dense atmosphere, the RCS may be too weak for attitude control. Control surfaces will be more effective.
• When both RCS and control surfaces are disabled, the joystick has no effect.
• In linear RCS mode, the joystick will not rotate the spacecraft, but add to the linear velocity vector.

If your joystick has a throttle control, you can use it to manipulate the main engines. If your throttle control is not responding, try selecting a different throttle axis from the Launchpad dialog.

The basic Orbiter installation doesn't support sound, but there is a popular addon available which adds this functionality: DanSteph's OrbiterSound plugin, available from his addon page or from the Orbiter file repository at AVSIM.

Orbiter renders stars (except for our sun, of course) as single pixels of varying intensity. This makes them quite faint (in particular at high screen resolutions), but also fairly realistic.

If your Orbiter definitely doesn't show any trace of stars, first check for the obvious: make sure that the star count, brightness and contrast levels under the "Parameters" tab of the Orbiter Launchpad are set correctly. If this doesn't help, and in particular if you also don't see any grid and constellation lines in "Planetarium" mode, then the most likely problem is the anti-aliasing setting of your graphics card. Try to open the configuration tool of your graphics driver, and disable anti-aliasing.

Orbiter uses numerical integration methods for propagating spacecraft states from one simulation frame to the next. The accuracy of this method depends on the simulation time interval between frames. While Orbiter's numerical implementation is quite sophisticated (including high-order Runge-Kutta and symplectic integrators, and subsampling of time steps), it may still lead to problems when extreme time accelerations are used during high-acceleration phases of a spacecraft (e.g. in low orbit).

It is generally a good idea to avoid high time accelerations when in low orbit, and in particular during powered flight. Orbiter also provides an "orbit stabilisation" mechanism that disables the numerical state integration in critical phases. Orbit stabilisation can be configured in the "Extra" tab of the Orbiter Launchpad.

... and the Orbiter.log file shows something like

ERROR: DDraw object is still referenced: 50
ERROR: Destroy framework objects failed

This orbiter log message is a generic indicator that something went wrong and orbiter tried a shutdown during which it couldn't remove all its previously created graphics objects.

This could be caused by any number of problems, for example by low system memory, by a graphics driver problem, another process running in the background, a misbehaving addon, or by a bug in the Orbiter core.

Try running a fresh orbiter installation (without any addons), use a low-resolution video resolution (say 800x600), try different video devices, turn off all the options in the "Visual parameters" tab, and don't use any high-resolution textures.

If nothing helps, your last option may be posting a message on the forum with as much information about your system (hardware, OS, graphics drivers, DirectX version etc.) as possible. With any luck, somebody with a similar system may have a solution.