But you're smart not to let the tool replace common sense. On the TARC Yahoo group someone wanted to know what was wrong with his altimeter. RocSim said the rocket would go to 800' and it only went to 600' so something had to be wrong with the altimeter.

__________________
Bill Spadafora
http://www.billsplumbing.com
billspad@comcast.net bill@billsplumbing.com

Many tools are worse than useless until you learn when and how to use them and understand their limitations (and yours.)

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Carl McLawhorn
NAR#4717 L2
semroc.com

Wow, extra BP for blow thru. Better not let MicroPicture find out that you do that. He'll have a cow, then he'll post some impossibly tiny pictures to support his position

Doug

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YORF member #11

What all types of logic did you work with, Carl? I'm guessing DTL and RTL were the common types in the early 70s.

For me, coming out of school in 83, LS-TTL was king, and was soon replaced by FAST-TTL. I did many board designs with that back in the late 80s. That technology will always be my paradigm.

I was actually a bit saddened a few years ago when I learned that all bi-polar logic had gone by the wayside

Doug

(And no, Bill, bi-polar logic is not the term used to describe how schizophrenics think )

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YORF member #11

We had to interface with some old IBM RTL logic boards, but everything we did from 1971 was TTL. 7400 series was on all the production boards when I started. I remember that I had to memorize most the Texas Instruments TTL Databook so I did not have to keep looking everything up. My first computer I built in 1973 was all 7400 series I.C.'s. The most complex part was the 74181 arithmetic unit. It executed the PDP-8 instruction set. I used it at home, but I could not get anyone at Telex interested in building "toy computers." When Intel introduced the 8008 microcomputer, I built a 7400 based board that executed the 8008 instruction set at 20 times the speed. Still no interest from Telex. The good part about it is that I always had a faster and better microcomputer in my basement than you could buy on the market.

I still design with 74HCT as glue. I just can't see the numbers on the surface mount parts. The sick joke is that as the early logic designers lose their eyesight, the IC companies make the parts even smaller. I used to laugh at my elders at Telex that carried a jeweler's loupe to see the parts back then. I did not realize I was laughing at my future self as well.

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Carl McLawhorn
NAR#4717 L2
semroc.com

Who is Micropicture?

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Carl McLawhorn
NAR#4717 L2
semroc.com

MicroMeister. He threw a fit a while back (on another forum) when it was suggested that some motor makers added a little extra powder in their boosters to guard against early burn-thru (thereby ensuring the same impulse level as like motors with delay). (I'm under the impression that some do/did, and some don't/didn't - ie, that it varied amongst motor makers.)

The "picture" reference has to do with the fact that his pictures are usually so shrunken as to be illegible

Doug

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YORF member #11

I didn't realize it went back that far.


I still have mine. It was a required text book in college, believe it or not.


I was surprised by that attitude in college. The professors were focussed on 500khz 6800 microprocessors, and even then I realized I could roll my own CPU out of discrete logic and bit slice that could run 10 or 20 or maybe even a 100 times faster. I think that was probably still true until the 68020 or 486's came along. Heck, Cray was still doing it that way for another few years until 500MHz processors overtook his stuff.


It's even worse now with laser branding. It's danged faint. And the light must hit it just the right way to get a good read. I actually have to use a stereoscope in the lab sometimes

Even then, that parts are so small now that we have to create encoded part numbering tables in the datasheets. The user reads a 4- or 5-character number off the IC package, then looks it up in the datasheet to get the complete umpteen character part number. If you don't already know the root part number, you won't know which datasheet to use. In some ways, the parts might as well be not branded

I don't think the various divisions within the company here cooperate on the encoded strings, so two entirely different parts, such as an op-amp and a temp sensor, which happen to share the same tiny package, such as a SOT23-6, might have the same encoded marking. So even if you can read the number, you still won't figure out what it is

Doug

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YORF member #11

Here's what RockSim suggests the flight performance could be for the A2-5. There may still need to be some tweaking with the numbers, as I think the RS engine editor is forcing slightly higher impulse and thrust values than what Carl gave earlier. Not by a whopping amount, but enough that the simulated performance might be a bit hot.

Design specs can be found on the 2D plan view. Launch rod was set at 48", but the model as-shown will launch from a 36" x 1/8" rod.

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Attached Files

A2 Test.rkt (112.1 KB, 9 views)

__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
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BARs helping BARs

SAM 0044
AMA 352635

Carl,

Thought you could use a little inspiration.

Here's a picture of the casting mandrel for a little something NASA's hard at work on these days.

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