Puzzling Flight Results - Why Do You Think It Happens

[VinceC]

A high school rocket club I am part of is test flying a rocket they will take to the ARC Finals in a couple of weeks. The Club is practicing consistency during their launch procedures. Same everything with the flights within minutes of each other. They seem to be encountering conditions where they have 3-4 predictable, "straight" flights to target altitudes and then one will head off "crooked" reaching a much lower altitude. These "crooked" flights are not into the wind. Not a rocket scientist so I am stumped. Just trying to learn. Thanks in advance for your thoughts.

Vince

 

[cls]

hi, my first guess would be the rocket hangs on the rail somehow, and or the rail and pad aren't rock solid stable.

can you post a video of an angled takeoff? would be interesting to compare with a video of a straight up launch.

are the launches using the same rocket every time? are the rail buttons clean? no scratches, grooves, etc? is the rail smooth, inside and out? does the rocket always slide smoothly up and down?

same motor every launch? do they all ignite cleanly, no chuffing?


You are wise to keep practicing! best wishes at the big event!

 

[Scott_650]

Here’s another vote along with cls for the rocket hanging up on the rail/rod or some movement from the launcher. It doesn’t take much to disturb a nominal flight in the few seconds it’s sliding along the rail.

 

[smstachwick]

A high school rocket club I am part of is test flying a rocket they will take to the ARC Finals in a couple of weeks. The Club is practicing consistency during their launch procedures. Same everything with the flights within minutes of each other. They seem to be encountering conditions where they have 3-4 predictable, "straight" flights to target altitudes and then one will head off "crooked" reaching a much lower altitude. These "crooked" flights are not into the wind. Not a rocket scientist so I am stumped. Just trying to learn. Thanks in advance for your thoughts.

Vince

I’ve seen some speculation on my local TARC teams that the eggs may be shifting in flight.

 

[Tractionengines]

WHAT MOTOR? Some "chuff" [start slower, sometimes, leading to lower rod exit velocity], some start "fast".

HOW LONG IS USABLE LAUNCH RAIL? Is it a rod or a rail?

What is calculated rod/rail exit speed based on their simulation, at actual useable rail length? [ distance from TOP rail buttons, to tip of rail]

 

[rcktnut]

Thrust Misalignment

 

[gldknght]

If you are using a rod, you could be seeing the results of "rod whip". Even a strong momentary gust of wind can deflect the tip of the rod if the rod length is long enough. So the deflected flight path could be in almost any random direction.

How stable is your launch pad base? If you press down on it, is there any lateral movement, or change in the rod / rail angle?