Rich Pitzeruse

Wow, cool! One single 200 page PDF file!

denverdoc

interesting, but who'd want to use a 38mm motor in a 4 inch rocket???

ddmobley

Did I miss something? I routinely flew 38mm motors in 4" rockets. An EZI, for example, flies nicely on I211's and J350's. I must have missed something.

Anthony Cesaroni

Well done nomograms. I would have loved to have seen the look on the Swiss watchmaker's face and heard his comments when someone first handed him a quartz oscillator way back when.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto

SpartaChris

Me. I'm not a performance junkie, and much prefer slower, more dramatic flights to any speed/altitude flight.

Chris at CLPL

I suspect that if he worked at Breitling, he just chuckled and went back to work.

DumasBro2

I think I'll just use wrasp or pwrasp. All those lines confuse me.

JRogers

Isn't a nomogram a test women over forty have to have done?

Art Upton

While EZ-Is do work ok on most I211s, I see them get their fins ripped off at the roots on higher average thrust motors. This has been told to me its because of the fin designs.

Do you have a non-glassed EZ-I that survived a J350

They were made for the H45, I65, J100, and J125 motors back in the day.

The New LOC Fantom-EXL takes on the role as the 4" kraft paper rocket with plywood fins and 38mm mount that can take the higher average thrusts

I've abused my stock LOC Fantom-EXL even with a Loki J520.

Juerg

But have a copy of the nomograms at hand for the moment when the laptop battery gets empty, the sun is too bright or if you just want to get a result within a few seconds.
It's not meant to replace simulations.

While nobody probably is carrying the printed file with him, on our launches we do have one copy available at the RSO table.
And it's being used, both by RSO's (to be able to counter "my 6" rocket has simed at 4000ft on a G80" - claims of rocketeers) and flyers (who are not sure about delay selection and don't have a computer at hand).
http://www.argoshpr.ch/Ima...imagepages/image110.html (right hand side on the table)

The coolest nomogram by Andreas Mueller is for sizing a black powder charge, really handy!

Juerg Thuering
TRA 04981 / TAP
(Switzerland)

Squirrel Works

You're thinking of a mammogram. They confuse me too. When I first heard of a mammogram I was thinking that a telegram is a piece of paper with a message on it.... A candygram is a box of candy with a message... Yeah, somebody send me a mammogram and tell them I'm a slow reader. Better yet, tell them I'm blind and send the braille version.

ddmobley

I don't have it anymore, but my very first rocket kit was an EZI-65, non-glassed, with an extended air frame for altimeter compartment. Flew it on J350's regularly...

Init 6

I don't see the point - of Aerotech that is

CTI Way to go!!!

Juerg

That got quite evident.
Let me clarify: Aerotech's point is that they gladly published work done and offered for publication by Dr. Andreas Mueller. We have been using those nomograms on our launches for a while yet. Service to the rocketry community is the keyword. Not AT vs. CTI...
(And no, Dr. Mueller is not linked to AT, he just enjoys their products)

Init 6

I was being a little tongue in cheek

But as someone who started rocketry in the UK after 'the fire', I find it difficult to see the need to grease o-rings etc. CTI seems a more 'evolved' product.


Must try to time my next visit to CH when there is a launch on.

oh, and anything that makes an RSO's life easier is a good thing.

Chuck_Rudy

I'm looking for how to adjust for launch altitude and wind......I think it needs more lines. I'll stick with CompuRoc. I've always wondered what actuaries do on their days off.

Chuck

Juerg

Beware, I'll tell Andreas (and as I know him, he'll gladly generate one with more lines, just for you)

Chuck_Rudy

Too late.

It's already been done.

It's called......

Plaid.

Chuck

Juerg

I can't resist to comment on that one, Anthony, as it WAS Swiss watch makers who invented the quartz oscillator
http://invention.smithsoni...ventors/researchers.html

Steve_Shannon

Not exactly - Swiss scientists and engineers (not watchmakers), working in the USA, developed a micromotor using quartz oscillators, but quartz oscillators were invented much earlier than that by the Curie brothers (French) in 1880 and 1881 and adopted by the U.S. Army Signal Corp before WWII, long before they were used in watches.
http://www.ieee-uffc.org/fc_history/bottom.html

Juerg

Yep, I was imprecise there, but we were talking about watches...
And those were developed in the CEH in Switzerland...

crontab

I'm not trying to start anything, but I have to ask: Why does it seem you only post in response to apparent slights toward Aerotech? I know you have posted comments on some altimeter threads, but with the majority of your posts being in defense of Aerotech, it makes you sound, well, like an apologist.

Steve_Shannon

And Japan, with watchmakers at Seiko working with quartz oscillators starting in the 1950s and getting to market first, in 1969...
http://invention.smithsoni...z/coolwatches/seiko.html

Init 6

Oops! Didn't mean to start an AT v CTI war. I'm just coming off an I540WT high and find it hard to conceive of anything as cool.

Maybe I just need to see more AT.

ddmobley

Users shouldn't have to explain their posting habits to others here, so before this escalates, let me say this seems like a personal attack. I shouldn't have to remind you of previous conversations about that.

Chuck_Rudy

This could get good, I may need to grab a beer. We have the 'oscillator origin occurance' and the 'Only AT for me' going on at once......now I want you to remember, let's keep it clean.......no rabbit punches, no kidney punches NO BLOWS BELOW THE BELT!!! Now go to your corners and come out fighting!!

BTW Init, a Blue Diablo motor is something to behold. They are the toughest thing for me to video, they just crank......but you have to be in the northeast to see them. The commercial guys do a nice job, but that ragged edge is fun to watch, even if they trip over it occasionally.

Chuck





Pfffffffffffffft....the sound of the air going out of the balloon.......the beer stays in the fridge.

Chuck

Juerg

Maybe because you want to see it this way?
Here for example, it's about work of a fellow rocketeer, in reality...
Apart from that, I am sharing Darell's view and will not enter that dispute.

Anthony Cesaroni

Selective history in terms of the device itself. Regardless, the early production of some Swiss designs were temperature sensitive and would change frequency with very slight temperature changes IIRC. A U.S. company capitalized on the anomaly and produced a temperature measuring device using it that can resolve a degree Celsius to more than 3 decimal places. That's not trivial and the coincidence advanced technology further. Most Swiss stuff rocks BTW aside from their culinary skills and the Swatch thing.

Industries can be technologically innovative regardless of nationally and methodology. There's nothing wrong with having a bit of fun along the way.


Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
http://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto

Steve_Shannon

Sorry Chuck! I hope I didn't come off as trying to start something other than friendly bantering with Juerg. Before becoming an engineer I used to be a jeweler and so the subject interested me. Most technology in the last century had multiple parallel paths, often without each other's knowledge, but eventually all of the research counts for something.

So, go ahead and have a beer. It's after 5 everywhere except the left coast. Even here in Montana

Chuck_Rudy

Steve


Thanks for the offer, I'll take you up on one someday, but I'll pass on it (the Weyerbacher Pumpkin Imperial Ale) tonight......what am I bid for these former ringside seats? Ah....I'll hold onto them, ya never know, we're always one post away from enlightening entertainment.

Point/Counterpoint was a great show, and I always enjoy a battle of wits. Some of them bring me to tears with the dripping sarcasm, dry humor and a wonderful pyramid of facts rolling on top of each other, sometimes entwining themselves into a tangled rat's nest of indecipherable white noise. So just in case, I'll keep watching.

Chuck

Andreas Müller

Actually, launch altitude is adjusted for. But it's there mostly to illustrate that it's a rather unimportant contribution. Density of air depends on pressure and temperature, and most simulation programs just take these from a standard atmosphere. However, usual variations of atmospheric conditions are on the order of 10% around the standard atmosphere. It doesn't even help to measure pressure and temperature at the launch site, because on sunny days (rainy days are less than perfect as launch days) the temperature gradient in the lowest layers of the atmosphere is usually far away from the one in the standard atmosphere. A precise correction would thus only be possible with data from a meteorological sounding, which has to be rather close to the launch site (a few kilometers). Hardly any rocketeer has access to such data (We, Jürg and I, did have a few months ago, when we could arrange for a meteorological sounding right at the launch site for a test).

Wind is even more complicated. When the rocket leaves the rail, it is usually still relatively slow, and it experiences weathercocking, i.e. during a very short interval the local wind speed "bends" the trajectory. Now the turbulent boundary layer of the earth is about 100-200m thick, i.e. by the very nature of turbulence, the wind speed and direction that causes weathercocking is to a large degree random. I.e. unpredictable.

Above the boundary layer, but still inside the Ekmann layer, we usually have varying wind directions ("Ekmann spiral"), and increasing wind speed with altitude. Again, a sounding or a wind profiler would be necessary to correctly adjust for these. But if we assume (incorrectly, for most weather conditions) constant average wind speed and direction, and ignore the problem of measuring it (wind a few meters above ground is not good enough), computing the wind influence after weathercocking can be done based on the nomogram with sufficient precision: multiply the wind vector with the time the rocket stays in the atmosphere. For the time up, take the apogee time from the nomogram, for the time down divide apogee by the sink rate (there is another nomogram for that .

When the boundary layer is not turbulent, wind speed is probably so small that it is not of interest (remember that the earth is quite large, so Reynolds numbers tend to be large just because of that).

The most serious contribution to imprecise trajectory simulations, however, is the fact that the drag coefficient is neither known nor constant during the flight. But if you believe your altimeter, the nomogram actually allows you to estimate the drag coefficient. To do this draw points (mass/altitude) into the nomogram (note that within a group, they all use the same mass and diameter scales, so that you can e.g. combine the results from flights with different motors on a single transparancy which you can lay over the nomograms). You will get a cluster of points. Take the center of gravity for this cluster and go to the left in the nomogram, "unwinding" the process of finding altitude and apogee time. Then you can read off the average drag coefficient for those flights.



I didn't quite get that one.

UncleVanya

Where would we get a copy of this or anything else other than the most recent Aerotech nomograms?

Chuck_Rudy

CompuRoc accounts for much, obviously not winds at 1K', and allows you to choose a few more variables on top of motor variables. With it you can get a very close (theoretical) estimate to the perfect day flight in which all variables are kept stable. As you state Cd is one of the biggest unknowns to most, but propellant performance variables are large also.

The smaller the motor the more insignificant I believe a sim is. Which makes it, and all other sims, only a best guess. So I take CompuRoc, feed into all the variables I can and enjoy some flights in the middle of the night from my desk. It does give me an idea of what an AT vs. CTI vs. EM vs. Loki or even vs. an old Kosdon could do under perfect conditions in the same rocket.....and that may be it's best reason to exist. In the real world (if I can believe my alt data) this motor on this rocket went 5K', under the exact same conditions a competitors motor should go 5.5K'.

http://homepage.mac.com/wesrudy/pics/CompuRoc.jpg

The nomograms are a tool (and a tool which looks like it took a bit of work), but just as in sims their usefullness is clipped by variable motor, air, winds, Cds, density etc etc variables.......as such they are useful for comparason with other motors for hypothetical differences, but will not be a failsafe tool. One day that will come and it will take up to the minute weather data along with real life Cd info and variabliity with changing speed.

That day's not here yet for us in the toy rocket world......when it comes it will be very cool.

Good work on the nomograms and as for the acctuary reply......I'd betcha Jeurg gets it.

Chuck

Andreas Müller

It will probably never come. Since you cannot measure the atmosphere exactly where the rocket will fly five minutes later, you have to predict the state of the atmosphere. However, there are limits in predictability, on the large scale given by the low resolution of atmospheric models (you cannot make larger computers than using all the silicon atoms on earth), and on the small scale by the probabilistic nature of turbulence. The first limitation was recently studied in a project which later grew into a weather prediction service (see http://www.meteoblue.ch). The second is the topic of many studies of probabilistic errors of ballistic trajectories.



An earlier version of the nomograms included lines that helped estimate these errors. They were later removed: too many lines

Juerg

Not really... (what may be a language problem...)

Steve_Shannon

Here is my understanding:

Actuaries calculate statistical probability for all kinds of things. Insurance companies hire them to calculate their risk in underwriting an activity. The job requires an almost fanatical attention to detail and understanding of statistics. Although the profession of actuary receives unusually high reports of job satisfaction, most people have the impression that generating actuarial tables would be the most boring thing in the world. I think the joke was that generating these nomograms would have required the same kind of skill and would have been a task an actuary would have been suited for.

Juerg

Well, maybe. But if somebody is ready to spend that time and generate something we all may profit from (saving lots of time), a joke probably isn't the adequate reaction...
That's why I thought he ought to be meaning someth