Downloading Rclsoftware Gravel 2.0 from the developer's website was possible when we last checked. We cannot confirm if there is a free download of this software available. The program relates to Education Tools. This free program is an intellectual property of Rclsoftware. We recommend checking the downloaded files with any free antivirus.
From the developer:
Gravel is a simple simulation which models the behaviour of astronomical objects in space, according to Newton's Laws of Gravity.
You define several objects (stating their mass (kg), position (m) and velocity (m/s)) and Gravel calculates how these objects would behave in space.
You can even tell Gravel to place one or more objects in orbit around an other object and Gravel will automatically choose the right orbital speed.
You may want to check out more software, such as Rclsoftware Gravel v3 SDK, Just Trains Seacow for RailWorks or DiRT2, which might be related to Rclsoftware Gravel.