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Author Topic: question on G-SNDO autopilot  (Read 8017 times)

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Offline canadave

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14 March 2003, 00:40:20
Hey guys,

Question: when I use the ascent autopilot to get to ISS, it works great for putting me in a circular
orbit.  Unfortunately, that orbit is around 210km high, and the ISS shows as being at 360km!  Not
to mention that the heading is way off for me--I have more luck heading at 140 degrees than 43.  
Can anyone tell me why this is so far off for me?  I don't have any ISS add-ons, and I'm using
the "Landed at KSC" scenario that comes with the G-SNDO distribution.

Thanks!
Dave


Offline DanSteph

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Reply #1 - 14 March 2003, 00:56:20
You must wait that the ISS's orbit pass over you using accelerated time,
the curve of the ISS orbit on the MAP MFD must pass right over KCS
and the cross showing ISS must be one centimeter before KSC

it the curve surrounding KCS RISE you must launch 42,5° (42 or 43)
if the curve FALL you must launch 135°

During ascent you can *FORCE* the autopilot to yawn with the joystick
to correct the small RINC error remaining (wait first that it finish to decrease
himself then force it a bit to correct remaining difference)

and the target is LEO (Low Earth Orbit) it's a common technique used
while reaching higher altitude is really easy in LEO.



When orbit like this , it's Time to launch at 42°


Dan



Offline canadave

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Reply #2 - 14 March 2003, 01:38:07
Ah.  I see! :)  OK, so I guess I was launching when the line of ISS's orbit was FALLING.  And then I
guess what you're saying is that once in LEO, I can fire main engines and ascend the last 150 km
to ISS without much hassle?

Then my next question is, why go to LEO first?  Why not just go all the way to ISS's altitude in one
shot?

Thanks!
Dave

p.s. that would all go great in the documentation ;)
p.p.s. thought you were going to sleep? :P


Offline sebfly

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Reply #3 - 14 March 2003, 08:37:11
Hello,
Once you're in LEO "Parking orbit" it is only a small burn to elevate your orbit to the 370 odd km,
but you have to circularize it one you reach your new Apd. That is burn a little more (all prograde)
to make your ecc close to 0 again. I will have to do some tests but I am not sure going directly to
370km is more economical (fuelwise) that going to LEO and THEN change altitude. But you can try
to write another ascent program to take you there directly.
There is a little mistake in the doc, when you load the "Landed at KSC" scenario of the DGII, the
launch heading will be around 135° not 43° (in this case), at least that's how the scenario sets it  
up for me (ISS orbit NW to SE).


Offline DanSteph

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Reply #4 - 14 March 2003, 08:45:57
Seb,

I was assuming that everyone knowed how to set a proper orbit for launch
but I will change the scenario so the Iss is in position for a launch a 42°
when you start in game....

This said the problem will be the same if one want to launch for Mir later
I suppose I must add that in the doc ?

and Dave LEO is much more economical in meaning of fuel.
reaching high orbit take about no fuel in comparison.

Dan


Offline sebfly

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Reply #5 - 14 March 2003, 09:53:24
Hi Dan,
I guess the basic trick can be included in the doc, that is roughly:
Target orbit over launchsite NW to SE ("falling"), launch heading roughly 135°
Target orbit over launchsite SW to NE ("rising"), launch heading roughly 45°
When target orbit is "flatter", then use headings between 45° and 135° (including 90°)

Of course there is TransX that will tell you exaclty what launch heading you need. I really need to
learn this TransX....

BTW Dan, I installed DX8.1 and still my sound is messed up... :(
Thanks for all the help you gave me still. I think I will post this in martin's forum and see what
comes up....


Offline DanSteph

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Reply #6 - 14 March 2003, 10:04:18
Seb,

mhhh and what about the framerate ?  if the proc is too busy
there is no more place to process the sound this is perhaps why ?
I think more and more about a driver problem, that seem consistant while
you just installed Win2000, did you try detonator ? (do you have a nvidia?)      


Dan



Offline sebfly

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Reply #7 - 14 March 2003, 10:17:27
Got the last version of Detonator XP, the card is a GForce 2 MX200 32MB. Proc is Duron 1Ghz
It is a processor iand win 2000 issue, because when i turn off all the eye candy in orbiter and switch to say
800x600 res, the sound improves a bit as well as the framerate of course...I also tried a fresh
install without patch 0303 and an older version of the DG and the problem is still there, so it is not
a patch problem nor a new version of DGII problem (even though is eats up more cycles). I am still
investigating, there are a few more options i have to examine, will keep you posted...

P.S. where did u get that nice backgound for the map MFD?? Looks really nice.



Post Edited (03-14-03 10:40)


Offline DanSteph

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Reply #8 - 14 March 2003, 12:47:20
I found it at AVSIM don't recall the name of the add-on....
I think there is also map for moon and mars (not sure for this one)

Good luck, I hope you will be able to resolve this issue,

Dan


Offline canadave

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Reply #9 - 14 March 2003, 16:44:55
Good morning all! :)

Seb, this link should do the trick for your color maps:
http://library.avsim.com/sendfile.php?DLID=23992

Cheers,
Dave

>edited by big brother to add URL Tag


Offline OrbiterBri

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Reply #10 - 14 March 2003, 20:07:04
All,
Regarding Launch heading. I found best thing to do if you are using default KSC scenario is to
change programme and rename it (PRO104SPEC42 to PRO104SPEC135) then call the new program
at launch I only changed the heading to 135deg and very good result very small burn to correct
Apd and Ped Rinc was less than 1.5deg.
Maybe it would be more usefull if the documents taught people how to write there own programs
they could call?
Does any one know how to calculate a launch window date for any target i.e ISS,moon,mars Etc.
and how do you change this date in the scenario to save sitting on the runway for ages?

Regards, Brian.

« Last Edit: 14 March 2003, 20:54:54 by OrbiterBri »

Offline DanSteph

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Reply #11 - 14 March 2003, 20:54:54
Brian,


The new version dated 11 march have some new feature as well as a new way
to enter heading for the ascent autopilot: instead of editing a txt file,the program
is now called "PRO903.txt" mean that at load you can directly type your launch
heading without editing anythings
eg type:
PRO903SPEC42    load the ascent prog and set the launch heading to 42°
PRO903SPEC135  load the ascent prog and set the launch heading to 135°

This version has also new feature but you may see into this link to have a list of them (the thread have the 8 march date but see at the end for the 11 march release):
http://orbit.m6.net/v2/read.asp?id=7517


Dan

« Last Edit: 14 March 2003, 20:54:54 by DanSteph »