LAUNCH RAILS I HAVE KNOWN
LAUNCH RAILS
So, you've built a rocket and now you're looking for some type of rail to launch it from.
All sounding rockets need some type of rail to aim them in the right direction until they gain enough speed (about 100ft/sec) for aerodynamic forces to keep them headed where you want them to go. Of course if you've got a really big motor with high acceleration, you can get away with a zero length rail, the rocket just drops off and it's inertia holds it on course for the short period to aerodynamic speed. For the rest of us who worry about slow acceleration and ground sharks, I've started a list of common launch rails below.
The MRL
The drawings I have are Genuine NASA drawings, that is incomplete, so I had to calculate some of the measurements, and there was initially some confusion over whether the measurements were inch or metric. It is a slot rail with an "I" shaped lug that brackets the slot rail elements. This rail is used at Wallops and Poker Flat ranges.
The Conduit Strut Rail
This product has several brand names, Unistrut, Superstrut, etc. It is used as a wall mounted bracket in construction to hold electrical conduit in place. It comes in ten foot lengths, so splices will be needed for longer rails, and it is expensive.
Perlin
I have used 4x2 perlin for a launch rail. It is cheap, and light, and comes in long lengths. It is used in the construction of steel frame buildings. The dimensions vary however, and I usually reinforce the bottom end of the rail to support the rocket's dead weight. Available at steel suppliers.
I won't mention the sliding door hardware we stole off the barn and used on our first launch, even left the bogies on the rocket!
Linear Motion Rail
This product is used in linear motion systems. It has four slots in a square outer cross section. The interior is an X, so the slide button has the shape of a truncated cone. I have included links to suppliers sites below. It is VERY expensive.
This type of rail is also available from other sources.
Overslung rails - these are rails that the rocket sits on top of rather than hanging from. The Nike rocket system is a good example. The disadvantage of an overslung rail is that it induces rotation as the rocket leaves the end of the rail. This is not a problem if the rocket is launched vertically or guided.
The MRL uses a drop out section at the end of the rail equal in length to the rocket lug spacing so that the rocket drops clear of the rail at both lugs simultainously.
SORAC
This is an overslung "T" rail. It is made of two aluminum "T" extrusions welded into an I beam. Top width is 1 1/2 inches, beam height is 3 3/8. The thickness is 1/8 inch for both cross sections. The rail is in three sections, added together making 58
feet total length, hydraulically erected on a trailer with power supply,
valves, regulators, and data aq equipment in a rack. The lugs are made in
two 90 degree "Z" sections, each rivetted to the airframe to make a
channel for the tee.
Send me your favorite launch rail and I'll put it here.
Veronique
The French Veronique sounding rocket was unguided, yet did not have a launch rail. It used four long cables and a cruciform attached to the fins to hold the rocket plumb during it's slow acceleration. The cables were held in synch by a geared base frame that served as the launch platform. The cables played out freely, but as the cables always remained equal in length as the rocket rose, the base of the rocket always remained level and the rocket plumb. The cruciform dropped off after the cables ran out. It was a unique solution that I hope someone attempts on an amatuer level.