Choose a launch system Large or small. For this example I will be using the Small launch system.

1) In the "G" menu set shortcuts for
.....a) Launch Loader Small Ship
.....b) Launch Rail Small Ship
.....c) Launch Slide Small Ship

2) Place one or more Launch Rail Small Ship in a line (on a large ship/station). The Direction of the launch is indicated by the yellow and black arrows inside the rail itself.

3) Place a Launch Loader Small Ship on the end you will be loading from. The Loader has a taper making one opening larger and tapering down to aid in the insertion of the Slide.

4) Go to a control panel or flight seat and find your Launch Rails Small Ship. I sujest you Group them together.
Set the Field width to 3-5m
Set the Field depth to 3-5m
Set the Field Height from 20+m
Make sure Acceleration is 1.00G

Width and Depth will set the field size above and to the sides of the Rail.
Height will set the size of the field along the length of the Rail.

TIP: The longer the Height the more the field will over lap the joining rails. The rails are 3 blocks long = 7.5m. so a setting of 20 will overlap ~3 rails gravity giving 3Gs of force in the field along the rail. A setting of 60 will give you ~6Gs

5) Install the Launch Rail Slide Small Ship on a small ship. You may want to do this away from a Gravity field as the mass will interact with the artificial mass of the Rail.
Set Friction to 0%
Set Restitution to 0%
Set Virtual Mass to Any Value (the higher it is the faster you will launch)
NOW TURN OFF THE SLIDE!!

6) Fly your ship and guide the Slide into the Rail using the Launch Loader Taper to assist you.

7) Some game mechanic may keep you from launching when you turn the slide on. To correct this.
Set your desired Virtual Mass
Put a shortcut on the hotbar for Slide Off/On, Increase Mass, and Decrease Mass.

To launch Follow this order

Decrease Mass X1 push
Slide On
Increase Mass x1 Push
ZOOOOOOOOOOOOOOOOOOOMM off you go.

(((((((I figured out The issue with failed launches. Its a Ball thing. If its not in motion when turned on it seams to not be influenced by gravity until the mass changes or it moves. The only other option is to make it a mass block but I fear it would be destroyed traveling the rail.
Solution: Move your ship forward some/ set forward thrust over ride/ change mass on the slide.))))))

Don't forget to turn off your dampers and then turn off the slide once you disembark.

Again the Space Ball mechanic is buggy. sometime just turning the ball off will make it remain the same mass as it was set. It is better to decrease the mass to zero Via the hotbar shortcuts or a timer block that will do it for you.