Leads
Year | Lead |
|---|---|
| Spring 2017 | Josef B |
Overview
When flying at supersonic speed, the wave drag - or the drag produced by trans- or supersonic shock waves - caused by rail buttons on the body of a rocket can become significant. A fly-away rail guide is a separate assembly that clamps onto the rocket on the pad and includes the rail buttons which would usually be on the rocket. When the rocket leaves the rail, the fly-away rail guide separates from the rocket mechanically via cam action. This allows the rocket to interface with a standard 80/20 slotted launch rail without the drag of external rail buttons during the majority of its flight. Bellow is a picture of the Project Virgo rocket with the first iteration of the fly-away guide attached.
History
The fly-away rail guide was originally created to support Project Virgo. This technology first flew on Virgo's first Flight Test. The rail guide successfully supported the rocket on the rail. However, due to an unforeseen mechanical binding mode, the rail guide failed to separate after the rocket left the rail. This resulted in Virgo reaching a significantly lower apogee than expected. The prototype rail guide did separate at apogee. However, this flight did determine that the carbon fiber rods used to bridge the two ends of the rail guide were sufficient to withstand the force of the rocket on the rail at takeoff. This prototype can be viewed in the zip labeled "FlyAway_v1"
The binding mode in the first version was eliminated by shortening the flanges opposite the rail-side of the guide and making the flanges on the rail side of the guide no longer tangent to the body of the rocket. This fixed design can be viewed in the zip called "FlyAway_v2" This version of the guide was flown at the Spaceport America Cup in 2017 and successfully both supported the rocket on the rail and separated from the rocket after it left the rail. This can be seen in the picture below. 
However, it was determined that the wooden dowels are not strong enough to withstand launch forces during a flight of the caliber of Virgo. Therefore, carbon fiber rods should be used, as originally suggested. Furthermore, the bottom part of the rail guide should be mirrored from the top, so that the guide cannot come apart under vertical friction forces, as can be seen in the above picture. This was done on the original guide but has not been done on the second version, so anyone seeking to use it should do this mirror in SolidWorks for themselves.
Additional Notes
- The guide was printed out of nylon infused with carbon fiber powder by Markforged. This was strong enough for Virgos flight
- The second version of the guide includes an attachment point for a streamer.
- Wooden pegs were used for the hinges of the guide for both flights. These proved adequate although the feature could probably be 3D printed as well.
Downloads