Launch Guides Basics
Model rockets need something to guide them in the right direction (that being straight up) until the fins stabilize the model. And, there are three basic types: round rods that use launch lugs (commonly known as 1/8", 3/16" and 1/4" diameter steel launch rods); square extruded aluminum channels that use rail buttons and launch shoes (commonly known as 1010 and 1515 rails); and towers, which are basically three or more rods mounted inside of metal rings that create an open tube that the model slides down into (no attached rail guides are used).
Supported Launch Guides
Launch Lugs: Low power model rockets are guided off the pad by launch lugs (short small diameter tubes attached to the body tube) which slide over a rod. The lugs guide the rocket up the rod until sufficient speed is developed for the fins to stabilize the model. These rods vary in diameter and length depending on the size and weight of the model, and the thrust of the motor. Low power launch lugs are usually just larger that 1/8" with mid power lugs are slightly larger than 1/4".
Rail Buttons: Rail Buttons are used in place of launch lugs when the size of the model makes it unsafe to use a rod. Launch rods tend to bend slightly from the force of the thrust until the rocket stabilizes and, with larger rockets, this can become unsafe. In place of the rod, a channel is used (commonly 1" or 1-1/2" square aluminum), and the side profile of a rail button looks like an “H” with the top and bottom of the letter sliding down into the channel. Launch buttons have the capacity to guide rockets weighing from a few pounds to a hundred pounds or more.
Limited Support and Unsupported Launch Guides
Warning: OpenRocket lacks native support for Launch Shoes.
Launch shoes are a mix between launch lugs and rail buttons, usually made from aluminum. Looking down a rocket from the nose to the tail, launch shoes have the same profile as rail buttons. But, when you look at them in a side view, rather than being round, launch rails have length, like a launch lug. They can look like miniature I-beams. Although OpenRocket doesn’t support launch shoes as a single component, the pod and fin set components can be used to create them.
The simulated results with launch shoes has not been verified and should not be relied upon without actual flight test verification and Cd adjustments of your own.