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The Solar System Discovery Kit

SSDiscKit Software Download
for Win OSeswindows logo

DOWNLOAD v3.01 (14.5MB) - DX8.1 req'd
DirectX 8 or better required
3D accelerator strongly recommended

Screen Capture: Earth from 80000 km

This Discovery Kit allows you to experience and learn planetary dynamics. Watch the Moon orbit the Earth and then compare it to Jupiter's moons dancing to the same time scale. This demonstration lets you experience the motion of the planets in true to life scales. Designed to run on Windows systems for DirectX 8, a 3D accelerated card is pretty much essential for this to work well. I believe that it will actually display without a 3D card, but the frame rate will be too slow and the program will be unresponsive. If you do have the hardware, you might find this entertaining or educational. My name is Paul R. Dunn and I authored this software in the year 2000.

This is some software I have always been dying to play with, but never found, so I finally made it myself. I have been improving it step by step and still may or may not improve it further in the future depending on interest. The renderings are based on fairly accurate calculations and data and certain true to life phenomena are plainly visible. Observe, for example the changing angle of sunlight over the course of each year to see how the seasons are affected. Watch the moon turn through a full circle of phases to demonstrate how the moon enlarges and shrinks and wobbles a little each month. Now observe the moons of Neptune or of Pluto. Gaze back at the planets from the moons!

How the Software Works

You navigate through the Solar System using the menus to go directly to Planetary systems by name. Once you are there, you can zoom in and out by using the 'cursor up' and 'cursor down' keys. Using 'cursor left' and 'cursor right' will adjust the time scale. The range to the time scale allows you to slow the scene down to less than one scale minute (of model time) per real-time second (about 10x faster than reality) or view model time race by at about 300 years per real-time second (roughly 1 billion x faster). A variety of vantage points can be viewed this way.

You can zoom the display in and out to carefully inspect some well detailed maps of the major bodies in our Solar System. The main purpose of the application is to observe the motion of the planets. This is best achieved by adjusting the time scale to the appropriate subject matter. While viewing any particular planet, adjust the speed so that its day or its year takes up a second or two in real-time to observe what happens throughout these cycles.

I welcome feedback or bug reports if you find any, but if it just won't work on your system, remember: DirectX 8 and a 3D accelerator card are essential. Some hardware combinations might cause the software to complain and report that it is reverting to 'software rendering'. If this happens it might be best to run the program in full screen mode ('Alt-Enter' will pick a default mode or press 'F2' and select one). Higher resolutions will look better and display more stars, but will run at a slower frame rate producing a choppy effect. The smaller moons will be hard to spot at low resolutions, especially when they are at low phase and little light is striking them. Hardware plays a big factor in deciding what resolution to choose. All I can suggest is to try several settings. I developed it on a PIII-600 with an ATI Rage 128 video card and I like to run it at 1920x1440. This is the maximum my video card / monitor combination will support and I still get a reasonable display rate. The star rendering algorithm has been optimized in V2.01, significantly improving frame rate.

I welcome comments or questions on the kit. If you have tried it and like it or are having difficulty with it please write to me, the developer (email address in footer). I would be interested to know what you do with it. Before you write, though, please ensure that you have installed DirectX8 or better. You will get an error message that d3d8.dll is missing if you haven't installed it. A link to DX9 is provided above where the download link is.

Screen Capture: Saturn and its seven classic moons
year - day of year - 24 hour time

The display shows the progression of time. It provides an indication of the passage of time with relation to the motions modelled.

Limitations of the Simulator

If you are trying to use this simulator to predict when you might see the next transit of Mercury, or to see how the Moon will look one week from tonight then you are out of luck. The Solar System Discovery Kit, does not have any real-time representation for several reasons.True planetary orbits are very complex and are subject to many variations. Perturbations and precession are two main elements that are ignored. For explanations of what these are see the links at the bottom of this page. For the Earth to precess through 180°, it takes about 26000 years. Due to the speed that the sim is capable of running at, 26000 years can pass in less than 90 seconds at full speed, but you won't see any precession. At slower speeds the sim could run for years before getting close to that simulated timemark. As far as this Discovery Kit goes, the orbits of all of the planets are considered stable. The same orbital parameters are used for every calculation that the sim goes through. The orbital parameters used for the planets can be found in the first table here (external link). Notice in the second table (same page) that all of the elements change slightly through time.

This sim is somewhat like those old solar system models with gears and cranks and coloured balls that all dance around a light bulb sun. Digital electronics have allowed much better precision, but what you see is still a far cry from the reality of it.

What the Simulator Provides

As well as helping novice astronomers with identifying the planets and moons, an observer of the Solar System Discovery Kit can see the shape of the orbits of the planets, and it demonstrates some of the patterns that emerge from orbital motion. Eccentricities become observable when time is controlled and the affect of a highly inclined axis like that of Uranus become very apparent when its year is reduced to a few seconds. Planets etch out epicycles in the sky when viewed from other bodies. The sim will demonstrate this process when you watch, for example, Mars from the Earth system. The links below explain orbits and some of the surprises you come across are observable in the Discovery Kit.

What's New in Version 3?

Version 3 includes the following new features and bug fixes:

How did I make this?

Many of the surface maps used to render the planets and moons in the application are based on scientific data gathered by the jet propulsion laboratory. The following references have helped to organize and present the data, and without them these planets would not look so realistic. The rings of Saturn are based on brightness and transparency maps from Björn's site. I'm not sure how true to life their behaviour in the oblique and direct sunlight is, but I have managed to make an effective rendering.

Some maps, like the Earth texture, were constructed by myself from a collection of maps found at these sites. The program itself, was written with Microsoft Visual C++ and Microsoft's DirectX SDK. I used a basic D3DApp framework used in some of the tutorials that come with the SDK. And now you can play with it for free.

The star data is parsed directly from NASA JPL's SAO Star Catalog; a file (sao.pc) which can be found at NASA Jet Propulsion Lab's web site. The PPM Catalog (found here), can also be used with the SSDiscKit. A menu item let's you select the active database, SAO or PPM. The SAO.pc file distributed with the kit since v2.00, is current as of Jan 05, 2001.

I especially thank the following resources and urge you to check out their web sites.

Why is it free?

I believe strongly in the free distribution of information. This program wouldn't even have been possible without the internet or the free availability of planetary bitmap textures, and astronomical databases. Programming and Astronomy are both hobbies of mine. I wrote the code to entertain myself and to get my own perspective on the Solar System. Now that I have done so, you can see it too. Also, thank you for visiting my site, for reading this far through the gobbledy-gook, and for supporting my efforts.

Links of interest

These links take you to sites that explain the physics of orbits.


Valid HTML 4.01! yet another web page arranged and Dunn by Paul,
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copyright © 2000,2001 (2006-08-20)