Very low drag (skinny & long) rockets are only at speeds low enough safely to deploy a chute very close to apogee (the point when the rocket start falling again).
The trick in knowing if your motors parachute ejection delay is too short and your chute is opening before your rocket slows down as it approaches apogee or if the motor delay is too long and gravity is accelerating your rocket past the parachutes safe deployment speed before the motor fires the ejection charge that deploys the chute.
Luckily the simulator shows you whether the acceleration was positive 100m/s indicating the motors delay is too short meaning you need to increase your motors ejection delay from say a C6-4 (4 sec ejection delay) to a C6-5 or C6-7 or if it is -100m/s you have to chose a motor with shorter delay such as a C6-5 0 C6-4.
Simulators are great at helping you choose the correct motor before your rocket becomes a lawn dart sticking out of someones head ;)
Some times the simulator just wont work with the motor you chose because the motors are not available with the correct delay time.
This happens a lot with long thin 24mm rockets flying on a D motor.Thus the bigger the motor and the more aerodynamic the rocket, the more important it becomes to get the ejection delay correct.
Great start! Have Fun On 11/15/2012 5:19 PM, Chris Coffee wrote:
Hi Tom,Will visit the Apogee link momentarily. I have already downloaded the OpenRocket software and was playing around with it last night. Absolutely none of it made sense to me...LOL! I designed a rocket (looked pretty cool) but when I ran the Sim it kept telling me that my chute was deploying at too high of velocity. It was deploying at 100 ft./s. Couldn’t figure out how to change that so I gave up on it for a while. Ha-ha.*From:* Tom Hanan <mailto:tom.hanan@xxxxxxxxxxxxxxx> *Sent:* Thursday, November 15, 2012 3:54 PM *To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx> *Subject:* [roc-chat] Re: Instructional/Educational MaterialThe Apogee RocSim Video Tutorial page has a great "EDUCATION" Tab at the top that covers a lot of what you might want.http://www.apogeerockets.com/Rocksim/RockSim_Video_TutorialsI personally use simulators to teach kids and interns the core intuition and skills they need to be successful in aerospace where safety matters.OpenRocket is an open source (free) simulator but lacks many of the teaching refinements of RocSim especially when you go super sonic.http://openrocket.sourceforge.net/features.html Have fun :) "Straw Hat" Tom On 11/15/2012 3:38 PM, Chris Coffee wrote:** Hello All,I have asked this question to two different people, and in line with human nature, got two different answers...LOL! So I put this out to everyone here in hopes that I can reap the benefits of a "majority rules" line of responses. I am looking for books, web pages, videos, etc. that will teach us most everything we need to know about model rocketry. I have found plenty of videos of folks building and launching rockets, but not any that have gone in depth into the *details *of the hobby. Examples would be Calculating COG & COP, Motor Designations/Properties/Characteristics, How to Determine Stability, etc. If anyone can please point us in the right direction to find this type of material, we would be very thankful. We have been told both that those types of materials do not exist (have to learn by trial & error), which I don’t really see being accurate. And we have been told that they DO exist BUT not sure where to locate them.
