calculating height

[codyr]

im new and im just wondering if there was a formulae floating around for calculating that max alt of a rocket also taking into account the parabola instead of a straight line

thanks

 

[Mike]

There's plenty of software available that can simulate your models and give you a predicted alitude (as well as stability) scroll down to the Rocketry Software section of this thread, many of those have free demos you can download. SpaceCAD and Rocksim are the most comprehensive.

They will all assume your rocket goes straight up as it near impossible to predict exactly how much weather cocking will happen.

 

[Fore Check]

In Rocksim, you can set certain simulation parameters such as wind velocity, and at what elevation the wind begins. There is also a 2D flight profile feature for the sims, and on a few that I've done it *has* captured some weathercocking. At first I thought something was wrong, but I noticed that the wind speed was set at like 20 mph - I lowered it to 10 and re-ran the sim. The weathercocking was no where near as bad in the 2D profile and the altitude was greater.

 

[jerryb]

Originally posted by codyr
im new and im just wondering if there was a formulae floating around for calculating that max alt of a rocket also taking into account the parabola instead of a straight line

thanks

estes website has a pdf file that shows you how to calculate the altitude of your models.. I have it downloaded at work...

they have a way to figgure out the weathercock effect on your launch..but you have to have a 2nd observer for it to work..

I havent tried it..but it looked pretty good from what i read.

i'll see if i can find that file tomorrow

later
Jerryb

 

[DynaSoar]

Originally posted by codyr
im new and im just wondering if there was a formulae floating around for calculating that max alt of a rocket also taking into account the parabola instead of a straight line

thanks

You get the angle of the altitude, using 0 degrees as the line between you and the launcher. You multiply the trigonometric function TANGET of that angle times the distance between you and the launcher. Set up your observation point crosswind (90 degrees from up/downwind) and you'll be able to see the parabola and take your reading from the peak, even though it may drift a bit from directly over the pad. You can find tanget tables in many math books, much orcketry literature, or any halfway decent scientific calculator (the prefered method, unless you enjoy long multiplication exercises).

If you want to estimate the angle, your fist at arm's length is about 10 degrees. Otherwise you can build an angle finder out of a plastic semi-circular angle measurer from a drafting kit or supply store, and hanging a string and weight from it. Or more fancy designs as found in many rocketry books.

If you prefer walking, hold out a long stick point up at arms length with your arm pointing at the pad. When the rocket hits peak, put the tip of the stick at the peak and note where on the stick the launch pad is covered. Rotate the stick to horizontal and note where the end of the stick ends up crossing a line perpendicular to you and the pad. Go up to the pad, and pace off the distance to the point indicated by the rotated stick. That's your altitude.