ORBITER Space Flight Simulator

Frequently Asked Questions

A. General

A1. Where can I post my suggestions/questions/corrections/bug reports?

There is a web-based Orbiter message board where you can post general questions and suggestions. It has dedicated sections for bug reports, addon topics, and all things spaceflight.
Additional forum sites and orbiter-related pages can be found under the Forum page and the Related sites page. Another useful link for tutorials and developer resources is the OrbiterSimulator Wiki. For general information on Orbiter, see the Orbiter Wikipedia entry.
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.

A2. 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.

A3. 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).

A4. 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.

B. Troubleshooting

B1. I have downloaded Orbiter, but how do I install it?

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.

B2. 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.

B3. 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.

B4. 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 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.

B6. Orbiter fails to run.

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.

B7. 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.

B8. No sound!

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.

B9. I don't see any stars.

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.

B10. Orbit deteriorates at high time acceleration.

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.

B11. 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.

C. Running Orbiter

C1. 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.

C2. 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!

C3. 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.

C4. 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.

C5. 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.

C6. 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.

C7. Why does the moon (sun, etc.) look so small?

The moon, as seen from Earth, covers an angular diameter of approximately 30 arc minutes (at a distance of ~385 000 km and diameter ~3 476 km, you can work it out for yourself). This is exactly the size at which it appears in Orbiter. There are two possible reasons why it may appear too small to you:

Too large field of view setting. If you want to see the moon and other objects in the simulation window at the same angular size as you would, for example, when looking out of a window, then the field of view (FOV) setting of the simulation must correspond to the viewing geometry. That is, the simulation window size and eye-screen distance. As a typical example, for a 19 inch monitor (4:3 aspect ratio) running Orbiter in full-screen mode, and a viewing distance of 60 cm, the correct (vertical) FOV setting would be 27 degrees. In practice, a much larger value is usually selected, to compensate for missing peripheral vision.

Optical illusion. People perceive the size of the moon to be much larger than it really is, in particular close to the horizon. Several explanations have been brought forward, for example http://www.noao.edu/outreach/nop/nophigh/steve8.html or http://facstaff.uww.edu/mccreadd/. You might want to take a photograph of the moon yourself, with a normal-focus length lens and including some trees or houses for reference. It is going to look smaller than you thought!