Splash modeling is great but its an order of magnitude better IF you
close the model loop by launching a short duration version of a motor
with the same initial impulse to minimize the splash window for the test
launch. You need to add weight to keep "all things equal" with the
lighter shorter duration motor. This is much easier to do in the amateur
world with re loadable motors that allow you to include spacer or
different grain formula to reduce burn time. Unfortunately the solids
tend to have reduced initial thrust based upon smaller grain surface
area unless the formula compensates for that. But hybrids can be light
loaded to deliver short test flights.
All of this is the same thing we tell newbies. Launch with a smaller
shorter duration motor first to get a feel for the airframe before you
take you altitude shot! Just because its harder and more complex with
laregr motors does not mean that we shouldn't be doing it! After all it
is that desire to master MORE complexity that draws many of us to larger
rockets with higher power.
On 6/16/2015 10:29 AM, Cliff Sojourner wrote:
You can do splash for models, for example spot landing contests.
Does anyone know, does openrocket do splash analysis?
On June 16, 2015 9:45:20 AM PDT, R Dierking <applerocketry@xxxxxxxxxxx> wrote:
So motor variability includes thrust vectoring?
Hum… all parameters varied?
OK, I’ve never done that because I haven’t even come close to
launching a high alt rocket. So, please forget my reference to
the splash analysis. Perhaps for now just keeping the topic to
the <20K’ rockets?
James, next time you do the analysis for one of your high alts,
please let me see the results and the track the rocket actually
took. Maybe someday, way in the future, I’ll need to do this.
*From:* James Dougherty <mailto:jafrado@xxxxxxxxx>
*Sent:* Tuesday, June 16, 2015 9:20 AM
*To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
What Cliff said :-)
Sent from my iPhone
On Jun 16, 2015, at 6:00 AM, R Dierking <applerocketry@xxxxxxxxxxx
<mailto:applerocketry@xxxxxxxxxxx>> wrote:
So the analysis does take into account launch angles. But,
what’s the maximum angle? Wow, than a high launch angle and
altitude could take your rocket out of even Black Rock and it
would be acceptable? I've heard that in the future FAA is
interested in roll control. I wonder why and if launch angle
(intended and true) would be important.
*From:* Cliff Sojourner <mailto:cls@xxxxxxxxxxxxx>
*Sent:* Monday, June 15, 2015 11:51 PM
*To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>
On 2015-06-15 11:46, R Dierking wrote:
This is an interesting problem, and a solution would help
many people. Really, what’s the use developing a
complex ‘splash’ analysis for a high alt flight if you
don’t even know what direction the rocket will be going
20’ off the ground! And, if you are off 5 degrees at that
point, it makes a lot of difference where your rocket is
going to be at +10K’.
hi Richard, not picking on you tonight, really :) Splash
analysis is a "monte carlo" simulation, many many flights with
all parameters varied, such as launch angle, wind speed and
direction, motor variability, etc. at the end you can say
with great statistical confidence that the rocket really will
fly and land somewhere on the splash chart.
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
