[roc-chat] Re: Clarification
- From: Carlo Vaccari <airplaniac2002@xxxxxxxxx>
- To: roc-chat@xxxxxxxxxxxxx
- Date: Sat, 25 May 2013 17:54:14 -0400
OpenRocket does 95% what Rocksim can do, and I use it all the time for high
power design.
On May 25, 2013 4:43 PM, "Chris Coffee" <chris_coffee@xxxxxxxxxx> wrote:
> Thank you to all who have answered. Looks like he will be good to go
> for launch.
>
> I appreciate the insight into the mathematics of this. Since I am by no
> means a “seasoned flyer” yet, I was just going by what I learned in Mark
> Canepa’s book Modern High-Power Rocketry 2 which didn’t say anything about
> using the initial thrust. This is one of the reasons I really love this
> hobby! Not only do I get to see fire and hear the roars of the motors, but
> I get to meet a lot of very nice and helpful people.
>
> I am using ThrustCurve.org more and more and am learning how to read the
> graphs and other data. Unfortunately, I do not have RockSim. I thought it
> was only a $40 program so I went to purchase it and saw how much it really
> is...and just can’t see myself spending $130 on a simulator. I know I will
> have to break down at some point and buy it because this OpenRocket program
> just doesn’t do me much good with the high power stuff. I keep hoping that
> I can find someone that I can pay a little money to have one of their three
> installs, but not looking likely. I know it sounds frugal, which I am at
> this point because I have dumped between $900 and $1,000 on the project I
> will be flying at ROCStock. [image: Crying face]
>
> Looking forward to seeing everyone at ROCStock in a couple of weeks.
> Should be a blast!!! [image: Smile]
>
> Chris Coffee
>
> *From:* Mike Riss <rockt_dude@xxxxxxxxxxxxx>
> *Sent:* Saturday, May 25, 2013 12:53 PM
> *To:* roc-chat@xxxxxxxxxxxxx
> *Subject:* [roc-chat] Re: Clarification
>
> I'd like to second Jeff's referral to a great rocketry resource:
>
> thrustcurve.org
>
> You can look at the complete thrust curve over time, and in particular,
> the initial thrust. Look in the "Simulator Section" under "Options", one
> of which is "View Data" (the icon with the magnifying glass). The initial
> graph is in newtons, but there's an option to display in pounds.
>
> Mike
>
> --- On *Sat, 5/25/13, Jeff Gortatowsky <indanapt@xxxxxxxxx>* wrote:
>
>
> From: Jeff Gortatowsky <indanapt@xxxxxxxxx>
> Subject: [roc-chat] Re: Clarification
> To: "roc-chat@xxxxxxxxxxxxx" <roc-chat@xxxxxxxxxxxxx>
> Date: Saturday, May 25, 2013, 12:22 PM
>
> Chris I have always used average thrust. But Carlo is right. The first
> second of thrust appears to be about 45 or so pounds of thrust. That is a
> guess from looking at the ROCKSIM graph on thrustcurve.org.
>
> I have a rocket at 6.5 pounds, and an I100 with a 5 ft guide reaches 41
> ft/sec at guide departure (according to RS). I consider anything above 35
> to ft/sec fine under normal conditions. (I have gone as low as 28 to 30 tho
> some say that is too slow. But on a calm day I've done it.)
>
> ---------------------------------------
> Jeff Gortatowsky, Redondo Beach, CA | Twitter: JeffGortatowsky | Yahoo:
> indanapt
> "(Scientific) Skepticism is not a set of beliefs, it is a set of methods
> for asking questions about reality." -- Doctor Steven Novella
>
> ------------------------------
> *From:* Chris Coffee <chris_coffee@xxxxxxxxxx>
> *To:* roc-chat@xxxxxxxxxxxxx
> *Sent:* Friday, May 24, 2013 8:22 PM
> *Subject:* [roc-chat] Clarification
>
> A little help here, please? I need to know if someone can tell me if my
> calculations are correct for a Thrust-To-Weight calculation for an upcoming
> flight...and whether or not the rocket should be flown on said motor? Thank
> you.
>
>
> Madcow Sensor weighing in at 7 pounds on the pad. 54mm motor mount. Using
> a Cesaroni I100-RL-LB this is what I got:
>
> Average thrust of motor (according to ThrustCurve) = 98.5Ns
>
> Divide 98.5Ns by 4.45 to get 22.13 average thrust in pounds
>
> Divide 22.13 pounds of average thrust by 7 to get a Thrust-To-Weight ratio
> of 3.16:1
>
> Is this correct?
>
> If my math is correct, I would say that the rocket should not be flown
> with the I100.
>
> Okay, folks.....school me!!! LOL
>
>
> Christopher L. Coffee
>
>
>
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