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  #11  
Old 02-08-2021, 06:29 PM
shockwaveriderz shockwaveriderz is offline
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Quote:
Originally Posted by georgegassaway
Check out the many Little Joe-II drawings on my website, at:

http://georgesrockets.com/GRP/Scale/DATA/LJoeData.htm

The drawings use STA numbers , with dimension lines going form most of them to show distances.

Nice thing about STA numbers is you can directly derive a length without adding up end-to-end-to-end dimensions, or having way too many dimension lines involving common start points. Just go from where you want to start, to where you want to stop.



The Space Shuttle STA numbers are wild. Different STA points for the Orbiter, ET, and SRB when stacked together. Also, in X, Y, and Z axes. Maybe I'll post and example of that later.


George I sent you an email about a rc bg PHOTO I HAVE FOR YOU.....
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  #12  
Old 02-08-2021, 06:51 PM
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OK, here's a shuttle drawing I made, that is reduced in size. To see a bigger version where the STA numbers are readabler, click this link: http://georgesrockets.com/GRP/Scale...tlesideview.GIF



And then there is a webpage I have, with a lot of scans of ICD's, mostly of the ET and some SRB.

http://georgesrockets.com/GRP/Scale...a/ICD_data.html

The drawing below shows ET attachment struts for the orbiter.



Detail "D" is the bipod that attached the ET to the obtier nose. Note that at the top of the bipod, defines STA#'s for both the ET and the Orbiter in the "X" axis. The XT is the Tank's X cordinate, and XO is the Orbiter's X coordinate, a common reference of the same exact place. A bit down from that, you see a ZO 283.841, for the Orbiter's interface plane in the Z axis.

Use this link to see a larger readable version.

http://georgesrockets.com/GRP/Scale...Orb_struts2.GIF

BTW - that particular Detail D shows that the shuttle orbiter moved upwards 5.5 inches from before fueling, to launch. Because of the ET tank shrinkage when loaded with liquid hydrogen (The SRB aft struts also pivoted to account for the shrinkage).
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  #13  
Old 02-08-2021, 07:24 PM
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Thank you for sharing your info here, George!
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  #14  
Old 02-09-2021, 11:12 PM
olDave olDave is offline
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Quote:
Originally Posted by frognbuff
It can be frustrating when Station 0 isn't where you think it should be. ......


The main reason that many manufacturers (aircraft as well as missiles) use a theoretical station 0 that is located well out in front of the vehicle itself is to allow for future versions.

If you put the origin of your coordinate system exactly on the point of the nose, then any time you have a revision of the nose shape, or a growth/stretch version, or any other significant change, you would have to go through the entire drawing system and generate a new set of location dimensions for all parts, as well as re-numbering the mass properties database, and a lot of other paperwork revisions.

Almost all vehicle config changes will still be using almost all of the previous vehicle parts, so why make yourself have to do a bunch of extra work?

Placing station 0 out in front of the nose by two inches or two miles does not matter, as long as you know the definition of your coordinate axes.
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  #15  
Old 02-10-2021, 06:38 AM
frognbuff frognbuff is offline
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Quote:
Originally Posted by olDave
The main reason that many manufacturers (aircraft as well as missiles) use a theoretical station 0 that is located well out in front of the vehicle itself is to allow for future versions.

If you put the origin of your coordinate system exactly on the point of the nose, then any time you have a revision of the nose shape, or a growth/stretch version, or any other significant change, you would have to go through the entire drawing system and generate a new set of location dimensions for all parts, as well as re-numbering the mass properties database, and a lot of other paperwork revisions.

Almost all vehicle config changes will still be using almost all of the previous vehicle parts, so why make yourself have to do a bunch of extra work?

Placing station 0 out in front of the nose by two inches or two miles does not matter, as long as you know the definition of your coordinate axes.


Quite possibly true for aircraft, but definitely not true for the Atlas and Delta launch systems. As stated before, the intent for these SLVs was to ensure alignment of flight and ground segments. Hard to tank a vehicle when the swing arm misses the fill/drain coupler by 10-15 feet!
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  #16  
Old 02-10-2021, 10:42 PM
PeterAlway PeterAlway is offline
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Just some interesting variations (it's been a while, so these might not be exactly correct. For the Saturns, STA 0 was 100" behind the first stage engine gimball axis. For the Titan, it was 500 inches in front of the stage separation plane. NASA would print station diagrams for their individual sounding rocket rounds with two systems, one with STA 0 at the nose tip for whatever the payload configuration was, and one with STA 0 at the nozzle exit plane (NEP) of the first stage. The Atlas had its STA O forward of the nose of the original version, at a point that happened to be 1310 inches in front of the main engine nozzles. Black Brants usually had the STA O point af the front of the motor.

For some rockets, the STA numbers were always consistent, and for some, they shifted with configuration.

I ended up adopting STA numbers for all my drawings, even when the original designers didn't use STA numbers, for threeo reasns:

First, if there are a lot of dimensions to cover, point-to-point arrows become really cluttered.
Second, point-to-point arrows often conceal inconsistencies. Many times I've looked closely at drawings to discover the numbers don't add up, and I don't want that in my drawings.

Third, point-to-point dimensions conceal missing information. It's really frustrating when I find source drawings that at first glance seem to have everything I need, but there's no actual indication of where the fins lie along the length of the body, or where a transition lies along the length of the body. By working with station numbers, it keeps me honest,

By the way, when I draw, I almost always type in the station numbers first, then draw in the construction lines based on the numbers typed into the drawing. That way, if I mis-type, the drawing will look obviously wrong, and I'll catch the mistake. Sometimes I don't work that way, and it tends to cause embarrassing mistakes.

I know it's not ideal to force the modeler to subtract to numbers to get their model measurement, but truth be told, the point-to-point dimensions on a source drawing aren't always the ones you need, so you have to add or subtract anyway. At least with station numbers, the required information should always be there.

By the way, errors are still inevitable. For instance, the blueprints I'm working on now for the Astrobee 500 include an overall drawing with station numbers, and a bunch of smaller drawings of component parts, and even accounting for overlapping or telescoping parts, the numbers don't add up and there are fractional-inch errors. Yet they are better than what I worked with for the original RotW drawing (I learned that the Asp motor had a fiberglass insulating shell added that increased the diameter by a fraction of an inch).

Anyway, I wish all those modelers good luck making sense of my drawings!

Peter Alway
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  #17  
Old 02-10-2021, 11:15 PM
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Peter,

I guess dimemsioned rocket drawings just happen to be your station in life ...
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  #18  
Old 02-11-2021, 02:04 AM
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Forgot to point out a "fun" thing about the Little Joe-II STA number ZERO point, or STA 0.00. It really and truly is at the "top" of the Little Joe-II launch vehicle. But I do not mean the tip of the Apollo escape tower. I mean the interface point between the Little Joe-II itself, and the base of the "Apollo" portion. Except for QTV, there was a 10 to 15" adapter ring first, then Service Module and the rest of Apollo. And so, everything above STA 0.00 is negative numbers, while everything below is positive numbers.



But the nice thing is, you do not have to subtract the "Apollo" STA numbers from the Little Joe STA numbers. Just add.

For example, take the STA -633.376 at the tip of the escape rocket nose in the A-002 drawing, and add that to the STA 350.0 at the base of the Little Joe-II body, and it adds up as 983.376.

NOT a length of -283.376 which you'd get if you used the negative value at the tip.

And see, I just defined a dimension that is not on the above drawing, but the STA number easily lets you generate it. Which, again, is why STA numbers are so useful. To define a distance from one location to another, that can be too much hassle to get into trying to have a dimension line for everything. As it is, I got a bit creative with some dimension lines branching off with 45 degree doglegs to share common start-end point arrows with other dimension lines.
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  #19  
Old 02-11-2021, 08:37 AM
shockwaveriderz shockwaveriderz is offline
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Hey George: I got some new RC BG information and pics I would like to send you.....i sen you an email via Ye Old ....let me know

Terry
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  #20  
Old 02-11-2021, 09:14 AM
olDave olDave is offline
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Quote:
Originally Posted by georgegassaway
......And so, everything above STA 0.00 is negative numbers, while everything below is positive numbers.....


And while this is perfectly fine to an engineering brain, it seems to hurt the heads of many other people out at the bomber factory. Thus the push to keep all the numbers "positive"
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