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Where can I post my suggestions/questions/corrections/bug reports?

There is a web-based ORBITER discussion forum hosted by M6.net where you can post general questions/suggestions or bug reports. Just click at the "Web Forum" button on the navigator bar. You can also join the ORBITER mailing list to exchange email with other users to get the latest hints and tricks. Before submitting a bug report make sure you have the latest version, and that the problem is not already addressed in this FAQ or the forum. As a last resort, you can email me directly, but I cannot guarantee that I will be able to answer all Orbiter posts.

When will the next version be released, and what is going to be in it?

I don't announce release dates and feature lists. This is mainly because Orbiter is a hobby of mine, and I don't need the pressure of working against a deadline or fixed specification. I can't always predict how much time I can spend on Orbiter, so the interval between releases will vary. The features added in a new version are usually a mixture of my own ideas and user requests. Occasionally screen shots of the upcoming version will be posted on the Gallery page, just to keep the suspense up.

I have problems downloading Orbiter.

Remember you need only the "Base" and "Textures" packages to run Orbiter. Everything else is optional. Select a download mirror close to your location, and if necessary, try several (try to avoid the medphys server, because excessive demand on that server will get me into trouble ;) If you have a slow connection, you may try at a different time of day when net traffic is lower. A download manager may help as well. Please note that I am not able to provide a CD distribution service, although Orbiter occasionally features on magazine cover discs (so this may be your last option).

How can I create/import spacecraft into Orbiter?

If you want to create your own addons, you should download the Orbiter SDK (software development kit) package. This contains the libraries for compiling your own spacecraft code, sample code, a few utilities and documentation. As a minimum, you will need to create a mesh for your spacecraft model (look at the Related Sites page for links to mesh converters from popular 3-D model formats such as 3ds), and define its basic physical properties in a configuration (.cfg) file. For more sophisticated models you may need to write and compile a specialised vessel plugin dll. Alternatively, there are 3rd party wrapper dlls available which can be controlled via configuration scripts. Finally, you must design a scenario (.scn) which loads your new spacecraft to see it in action in Orbiter. It is probably easiest to modify an existing scenario file by replacing one of the vessel definitions. If you get stuck, you may want to ask for help (or propose a collaborative project) on the addon forum.


A previous installation worked fine, but the latest version causes problems.

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. Another good practice to maintain is that of backing up your Orbiter folder before installing an addon. This might not be practicable on very large Orbiter installations which can run to many hundreds of megabytes, but for small/medium installation on fast modern hardware it doesnt take very long at all to do.

After installation, I don't see any scenarios listed, or I don't get any textures.

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.

I can see the scenario list, but the Start button is inactive and I can't launch any scenarios.

The scenario list contains directories (indicated by the folder icons next to them) and scenarios (indicated by the red delta-glider icons). The Orbiter Launch button remains inactive as long as a directory is selected in the list. You must select a scenario entry before you can launch orbiter. After a fresh installation there will be no scenarios in the top-level directory, so you need to step down into one of the subdirectories (by double-clicking on them) to access a scenario.

Orbiter takes a long time to load.

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. B5. I get a low frame rate.

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

Here are a couple of possible solutions: Quit other programs running in the background. Run Orbiter in fullscreen mode. Use a lower screen resolution and lower colour depth (16 bit). Reduce planetary texture resolutions and don't use the highres planetary textures. Reduce the number of background stars. Turn off object shadows. (Most of these options can be adjusted in the Orbiter Launchpad dialog.)

Orbiter fails to run.

Make sure you have DirectX7 or higher installed. Make sure DirectX is operating correctly by running the DxDiag test program ( Do this by clicking Start then Run , then typing in "dxdiag" at the prompt and then pressing Enter or click Ok. ) Make sure your system meets the requirements specified in the Download page. Make sure the parameters in your Orbiter.cfg file agree with your system specs. The Orbiter.log file might contain information about what is going wrong.

My joystick is not responding.

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.

No sound!

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

Orbit deteriorates at 1000x and 10000x time acceleration.

Orbiter uses discrete time stepping for dynamics, essentially approximating smooth trajectories by piecewise linear segments. This is reasonably accurate for small time steps, but at extreme time acceleration a full orbit may be sampled by very few steps, at which point the method falls apart. As a rule of thumb: Don't use 1000x acceleration when your trajectory changes rapidly, e.g. in a low orbit. On the other hand, en-route to Mars 1000x acceleration should be safe. Orbiter now includes the option to "stabilise" orbits under certain circumstances. A stabilised orbit is assumed to be an unperturbed Keplerian orbit which can be solved analytically with a 2-body solution. This prevents orbital stations from falling out of the sky while you are on your way to Mars at 10000x time acceleration. A vessel orbit will not be stabilised if it engages its thrusters, if aerodynamic forces are acting on it, or if perturbations of the central body's gravitational field are larger than a user-defined threshold. Use the Launchpad dialog to activate orbit stabilisation.

Orbiter dies unexpectedly during startup ...

... 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.

Running Orbiter

I've installed Orbiter, how do I start?

Assuming you have configured the video and other options in the Orbiter Launchpad dialog, you are ready to take off. Pick a scenario from the list, and click the "ORBITER" button. In a nutshell, the most important controls are on the numerical pad of your keyboard: Ctrl+ for increasing main thrust, Ctrl- for decreasing main thrust or engaging retros, Ins and Del for increasing/decreasing hovers (if available), and cursor keys for attitude controls. You should read the Orbiter manual in the Doc folder for a full list of keyboard functions, as well as explanations of the instrumentation.

Why can't I get into orbit?

To reach orbit from a planetary surface, you need to do two things: attain sufficient altitude, and sufficient tangential velocity. The first point is easy, but unless you reach sufficient tangential velocity, you will simply fall back to Earth again in a ballistic trajectory. The required velocity depends on the orbit altitude and planet mass. For example, a low Earth orbit (LEO) requires a velocity of more than 7000 metres/second. Orbital launchers usually take off vertically to clear the dense part of the atmosphere quickly, before pitching down to add to the tangential velocity component. You should always launch into a prograde orbit (towards east) to utilise the planet rotation. Orbit insertion normally occurs in two stages: the initial burn leads to a ballistic trajectory, and a second (orbit insertion) burn at the highest point of the trajectory (apoapsis) to raise the periapsis (lowest point of the orbit). If you are new to Orbiter, you should try your first orbit insertions with one of the more powerful spacecraft, like the Delta-glider. The more realistic launchers, like the Space Shuttle, don't provide much margin for error. If you feel ready to take on the Shuttle, make sure you turn on the "limited fuel" option. With unlimited fuel, the Shuttle is too heavy to reach orbit!

I want to rendezvous with the ISS, but I can't even get close.

The first step for a successful rendezvous manoeuvre takes place before launch. You should launch into an orbit with as little inclination to the orbital plane of the target as possible. This means waiting until the orbital plane of the target passes through your launch site (use the Map MFD to monitor this). By launching at the right time and into the right direction, you can minimise the need for later corrections of the orbital plane (once in orbit, you can use the "Align orbital plane" MFD for eliminating any residual inclination). The next step is to catch up with your target, by modifying your orbit appropriately. Use the "Sync Orbit" MFD for this.

I can get close to the ISS, but haven't succeded docking.

Once you got close to your target (see C3), use the Docking HUD mode and the Docking MFD for final approach. The Docking HUD contains relative velocity indicators which help closing in on your target. You need to tune your navigation radios to the target's transmitter frequency to make use of the docking instrumentation. (You can find the target's transponder frequency (XPDR) in the vessel info sheet (Ctrl-I). Set one of your navigation radios (Shift-C) to that frequency, and slave the HUD and Docking MFD to the appropriate receiver). In the final approach stage, switch the nav receiver to one of the target's IDS (instrument docking system) frequencies, if available. This will activate approach path indicators in the HUD, and docking indicators in the MFD, to guide you to your final docking position.

How can I get from Earth to the Moon/Mars?

Orbiter now includes Duncan Sharpe's TransX MFD mode, which is a great tool for setting up interplanetary routes. You need to activate the TransX module in the Orbiter Launchpad dialog to use this. TransX is quite a complex navigation tool, so to understand the concept and options, make sure you read the TransX manual (in the Doc folder) carefully.

I want to see imperial units instead of metric.

All internal calculations performed by Orbiter are done in metric units (metre, second, kilogram, Joule, Pascal, etc.), for the simple reason that this is the only system I am familiar and comfortable with, and it is widely used by the scientific community. Likewise, all standard instrument readouts and data displays are in metric units (with very few exceptions, like the use of astronomical units (AU) for large distances). There is however nothing preventing an addon developer from implementing instruments which display their data in a different unit system, and it would be entirely possible to write imperial unit replacements for all standard MFDs. Just don't expect them to feature in the stock Orbiter distribution. If you want to see feet, fathoms, stones, barns or quarts, you will probably have to code them yourself.

I am looking for "ApD" in the Orbit MFD, but I have no idea where the "ApD" is.

The manual eventually tells you to "Cut Thrusters when your apoasis (higest point of the orbit) reaches 6.731M (the "ApD" entry in the left column of the orbit MFD).

ApD = Apoapsis Distance ApR = Apoapsis Radius ApT = Apoapsis Time.

ApD = ApR

ApD and PeD have been renamed ApR and PeR - they are the same measurement however. (Distance between highest (ApR) and lowest (PeR) points of your current orbit and the center of the planet/moon you're orbiting.)

If you only see ApA (Apoapsis Altitude) and PeA (Periapsis Altitude) in the MFD, press SHIFT + D to switch to the radius display mode.