# Rocket wind tunnel testing

1. Sep 24, 2007

### Rattboi

How does a rocket get tested in a wind tunnel? what is it's orientation?

an airplane is facing the air, like in reality, as it flies. so does that mean you mount a rocket vertically, but have the wind come on the side? or do you mount it pointing in the direction of the wind?

and does that mean you have to rotate everything around when you are building the forces and moments database?

2. Sep 24, 2007

### mgb_phys

If you are testing it in flight you point it into the wind in the same way as an aircraft (ie horizontally). I suppose you could mount it vertically if you are trying to find out what happens when it is on the pad and the wind is blowing past it.

Main difficulty is probably finding a supersonic wind tunnel.

3. Sep 24, 2007

### fleem

The lift, drag, and air flow patterns around an aircraft (for a given wind speed and angle of attack) are unaffected by the weight of the aircraft. Of course, the weight of the model in the wind tunnel must be known simply so it can be subtracted from the measured downward force while it is in the wind tunnel. After all these other forces and the various flow patterns are discovered, then one can easily ask questions like, "will that lift be enough to hold up an aircraft of a certain weight?". So it isn't necessary to orient the wind tunnel.

4. Sep 25, 2007

### FredGarvin

Here are a couple of pictures for you. Like was already mentioned, the orientation of the model is such that whatever it is you are investigating is what is happening. If you are interested in flight characteristics, then it is mounted pointing into the flow of the tunnel. If you want to know about structural issues when it is on the launch pad, then you would orient it perpendicular to the flow. The main thing is is that the model orientation changes. The tunnel does not.

http://web.mit.edu/cats/www/photos/2002/2002_IAP/Jan29_Carl/Carl_slide1.jpg
http://www.staynehoff.net/saturnv-aedc.jpg