Model rocket height help

• May 27th 2008, 12:41 PM
Kwish
Model rocket height help
So Im supposed to find the maxium height for which the rocket traveled and am not really sure how to do it, Ive only figured this out so far.

The angle which the rocket was at from where I was standing at its highest point was about 86 degrees and the distance I was away from it was 100 feet. So would I just do (100ft) x (86)tan? or what?
• May 27th 2008, 12:50 PM
janvdl
Quote:

Originally Posted by Kwish
So Im supposed to find the maxium height for which the rocket traveled and am not really sure how to do it, Ive only figured this out so far.

The angle which the rocket was at from where I was standing at its highest point was about 86 degrees and the distance I was away from it was 100 feet. So would I just do (100ft) x (86)tan? or what?

$tan (86) = \frac{h}{100}$

$h = 100 \times tan(86)$

By the way, are you into model rocketry?
• May 27th 2008, 03:11 PM
Kwish
Yea, a little bit. Im in the middle of making an aluminum model rocket in shop class, its for extra credit in my geometry class if it flies and I can calculate the height.
• May 28th 2008, 01:13 AM
janvdl
Quote:

Originally Posted by Kwish
Yea, a little bit. Im in the middle of making an aluminum model rocket in shop class, its for extra credit in my geometry class if it flies and I can calculate the height.

I loved building them. Only small ones though. Yet nowadays I dont have the time or money for it anymore.

Here's a few tips:

Use 4 fins instead of 3.

And when you're done building it, attach a rope to it somehow and swing it all around. Make sure there are no people near you and don't get dizzy and fall over. :D

If the rocket doesn't make any erratic movements when you swing it like that, it's a good indication that it will be stable in flight.

NEVER launch in wind. Not even the slightest little breeze.

The engines we used pops the nose out with a little explosion at the end, so we used to attach a streamer to the rocket, so it's clearly visible when it falls. (Of course you have to attach the nose to the rocket with a string too or you'll lose it! :D )
• May 28th 2008, 01:09 PM
Kwish
Thanks for the tips. But my teacher insists to launch it regardless of the weather (Worried). So is it possible to calculate the height with the wind slightly curving its path?
• May 28th 2008, 01:26 PM
janvdl
Quote:

Originally Posted by Kwish
Thanks for the tips. But my teacher insists to launch it regardless of the weather (Worried). So is it possible to calculate the height with the wind slightly curving its path?

Of course it's possible... It might be tricky though. But how is the weather currently? Favourable conditions?
• May 28th 2008, 04:58 PM
Kwish
Yea, its about 65 degrees out, sunny and I'd say about a 13 mph wind blowing east.
• May 29th 2008, 01:06 AM
janvdl
Quote:

Originally Posted by Kwish
Yea, its about 65 degrees out, sunny and I'd say about a 13 mph wind blowing east.

That's 20 kph... I don't like that. You did say you're making it out of aluminium, so it won't be as light as mine, but still.

Does your geometry teacher say you should take deviation due to the wind into account though?
• May 29th 2008, 12:15 PM
Kwish
Yes, he said need to take the wind into account. Its got me really stumped (Doh)
• May 29th 2008, 12:56 PM
janvdl
Quote:

Originally Posted by Kwish
Yes, he said need to take the wind into account. Its got me really stumped (Doh)

I think I might just be able to do it. You just fly it old chap :D
• May 29th 2008, 01:05 PM
topsquark
Quote:

Originally Posted by Kwish
So Im supposed to find the maxium height for which the rocket traveled and am not really sure how to do it, Ive only figured this out so far.

The angle which the rocket was at from where I was standing at its highest point was about 86 degrees and the distance I was away from it was 100 feet. So would I just do (100ft) x (86)tan? or what?

Quote:

Originally Posted by Kwish
Thanks for the tips. But my teacher insists to launch it regardless of the weather (Worried). So is it possible to calculate the height with the wind slightly curving its path?

Sorry guys, I thought you were just chatting about model rocketry. I didn't know there was a question unanswered here.

Yes you can take the wind into account. I'm going to keep things simple, though, so we don't have to solve differential equations. I'm going to assume that the wind causes the rocket's velocity to change by a constant amount, and the wind will be in the same plane that the rocket is fired in and in the same general direction. (In other words the wind is at the rocket's "back.")

The problem is virtually identical to what you did before. The max height calculation is the same, but now we have an additional v attached to the x horizontal component of the velocity. So the rocket will travel an additional d = vt in the horizontal direction compared to what it traveled before.

If your wind is doing something more complicated then we have to resort to differential equations and things like air resistance. If you need help with that kind of model, just let us know.

-Dan
• May 29th 2008, 01:57 PM
janvdl
Quote:

Originally Posted by topsquark
Sorry guys, I thought you were just chatting about model rocketry. I didn't know there was a question unanswered here.

Yes you can take the wind into account. I'm going to keep things simple, though, so we don't have to solve differential equations. I'm going to assume that the wind causes the rocket's velocity to change by a constant amount, and the wind will be in the same plane that the rocket is fired in and in the same general direction. (In other words the wind is at the rocket's "back.")

The problem is virtually identical to what you did before. The max height calculation is the same, but now we have an additional v attached to the x horizontal component of the velocity. So the rocket will travel an additional d = vt in the horizontal direction compared to what it traveled before.

If your wind is doing something more complicated then we have to resort to differential equations and things like air resistance. If you need help with that kind of model, just let us know.

-Dan

Am I correct when I say it seems you are assuming the wind blows the rocket in a straight (diagonal) line? I guess I was complicating things when I was thinking it could be blowing in a curvey sort of way (Speechless)
• May 29th 2008, 02:12 PM
topsquark
Quote:

Originally Posted by janvdl
Am I correct when I say it seems you are assuming the wind blows the rocket in a straight (diagonal) line? I guess I was complicating things when I was thinking it could be blowing in a curvey sort of way (Speechless)

I'm keeping it as simple as possible and assuming a horizontally blowing wind with the effect of increasing the horizontal component of the velocity by a constant amount.

-Dan
• May 29th 2008, 05:49 PM
Kwish
Thanks for all the help guys (Rock) I might be able to get this thing figured out now lol.