Warren,

Interesting commentary, but irrespective of the resolution, I have recently learned that baro based units are inherently inaccurate for a number of reasons, not the least of which are local and temporary departures from the 1976 model. My understanding is that the higher rez models offer more precision and if downloaded to a good program the data can then be massaged into more accurate readings. But that aint gonna happen--"gee guys wait til my ACME atmosphric integrator ver 2.31 comes up with the real altitude!"
The other reason is that the altimeter algorithms are all different and offer a best guess, but its only that so while you might put them into a hypobaric chamber and get significant correlation, the reported altitudes will vary by a significant margin. For LDRS I plan on flying four different brands plus GPS to see whats up with this.

So we seems weez stuck until GPS is good enough to nail the Z coord, currently need 4 sats in the sky, pretty well spread out to get the theoretical WAAS error times a factor of 1.5. Theoretically within 10M or so.

Con, given your interests the Loki/Ozark ARTS might be your best bet for now. (the picoalt I mentioned was for other uses). It attempts to solve a set of simultaneous eqns from acc data and baro to spit out thrust, impulse, Cd etc. Obviously a best guess as well as there are too many variables, but John Bixler loves his and uses it to characterize his research motors. If you like dinking with math/sims a no brainer.
JS

I'm within a couple shop hours of having my GPS downlink system functional. The GPS works AND the serial RF data link works... just have to get the RS232 integration down...

Then its just a packaging issue.

Warren

Warren,

Way 8) ! Hopefully in time for a blast at LDRS! I'm still waiting for the darn mini phono jack connector to take the audio out to the PC soundcard, so LDRS will be the first time for the Bee Line.
J

Hey Guys

I just found this interesting, at ROC Stock last weekend, one guy put a H999 in a minimum diameter unweighted rocket.
Flew it with a Perfectflite for deployment, that was completely unmodified, and everything whet fine. Oh man did it shoot up into the sky. We estimate the gees at 127. The Perfectflite was undamaged, but when he down loaded the data it looked really weird.

CJ Jones

sounds like he was a lucky man. You gotta figure and hope really that the alt decisions are based on sound data, from the report u gave data was corrupted, survived to tell about it, Guess my point is you gotta take these high gees flights seriously, certainly not a testimonial for MAWD.
j

So I am looking further into the ARTS Altimeter as a Back up and Data recorder for my RRC2X 40k for my L3 Flight. Curious how well if anyone knows that this ARTS does with dealing with High G forces and what about MAch delay issues? I just need some final questions figured out before I jump and purchase.

With that kind of acceleration, I'm surprised the unit survived. The big electrolytic capacitor on Perfectflight and also on Missileworks altimeters (the only brands I own) are poorly supported against acceleration and I've had them rip off of the PC board on one project due to acceleration (or rather rapid deceleration when it hit the ground - estimated only 80 g's rather than 127 as in the case described.)

Just a few weeks ago I potted one of my Missileworks altimeters and it wasn't difficult. I made a wall of masking tape around the board as a whole, then dammed off the terminals, the switch and the baro sensor, and then poured in about 3/8" of West Systems epoxy to cover the components. Of course this makes the unit completely unrepairable and voids the warranty, but it should make the unit proof up to well over a 100 g's if mounted long-ways in axis with the rocket. Flat on, I'd be concerned that the membrane in the barosensor would tear from it's own mass at significant G loads.

Well I went and Did it. I ordered the ARTS. I played with the software and read the manual and spoke to a few owners. looks pretty good.

They're a nice unit and I like the add-on GPS module. My biggest issue with it is price, but then again, I'm a cheapskate.

Warren

con,

I think you'll be very happy with the arts, John Bixler sent me some data he obtained with his, and it did everything but wrote an article about the flight. Very impressive attempt at using some math wizardry to compute too many unknowns at once. Course the CD on the Nike came in at 0.1, but the thrust data compared reasonably against his static tests IIRC.

As to the MAWD, short of a full potting, one can strip the film of the electrolytic can, lean it over, and epoxy it to the board. Warren is absolutely right that this is the achilles heel of the unit. I've sheared two off and I'm sorry to say both times it was from rapid D'celeration. Good news is PF fixed it for free both times, bad news is now I'm afraid its sitting at the bottom of the reservior at Bear Creek. 😥

John S

I knew there was a reason I didn't go down there to fly... my rockets historically have a strange magnetism that attracts them to places where they cannot be recovered... trees, power lines, bodies of water... That's why I love flying at the North Site... nothing to get caught on other than a few windmills with ladders up them...

Warren

In the ripleys BION category, I have flown exactly two rockets at crash, on a superb day, and both enjoyed superp boosts--and both got wet. In the first case, some helpful fisherman brought it ashore. In the second, no such luck. Needless to say it dampened my enthusiasm for the site and flying any kind of competitive event from there--cept maybe those 1/8 a's(what serves as an average igniter at NCR) and B superroc. Too old to be steeple chasing after rockets, even when they land vs splashdown. But an important asset to the rocket community in general--sort of a breeding ground for HPR enthusiasts who will sooner or later realize 125 gm of propellant aint that much. 😆
John S

lol, I've probably got 20+ launches at Bear Creek this year (only 10 minutes away 😀 ) and no wet rockets yet (knocks on wood). It certainly isn't a substitute for the north site, but it gets me through between NCR launches. G64's thru 29/240 motors still give a heck of a ride in a nice Lil Nuke or smaller PML kit.

I fly at crash from time to time, and have only dropped one in the lake (recovered it too). I just get lucky there I guess...

As I said, just snake bit. a great bunch of folk and some seriously talented folk fly from there routinely. I'm hoping that next year we can do a NAR sanctioned event from North or atlas as there are many events that just can't be flown from there. For the record both rockets went 3 to 5 k which is just too high for the site. Its fine for anything under 2500 on a decent day that isn't a duration event
John S