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Author Topic: DG-III Competition 'From KSC to ISS'  (Read 13395 times)

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Offline Simonpro

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Reply #25 - 30 May 2004, 11:22:50
You an engineering student?
The only people i know who work 70+ Hrs a week are engineering students, physics students and doctors. :)


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Offline Cracker

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Reply #26 - 30 May 2004, 11:33:32
Not a student. I finished mech. eng. at Ga. Tech in '74. As the profit margin has evaporated for private enterprise in
these projects, for some reason the investment in time for many disciplines has increased. My niche, precision
layout/asbuilt, has become absolutely critical-path. I often coordinate and execute precision layout on projects in the
hundreds of millions of dollars, providing field layout for all crafts, each having several, if not dozens of crews. I start
at 5:00AM, get off at 7:00 or 8:00PM. I've been showing industrial construction personnel where to stick it for
decades now.
Cracker

Engineer involved in infrastructure improvement and repair.

Offline DocHoliday

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Reply #27 - 30 May 2004, 13:47:09
Okay, so to put some science back into the fancy flying we are dealing with this.. in a nutshell.


http://orbiter.vidmar.org/images/DG3-ISS-direct-ascent.jpg

Sorry for the shabby graphics, I'm not a pro with Photoshop either. Now if you can get a reliable ascent program, all
you really need to do is measure time in which you get to the ISS altitude, possibly also at that time MECO should
occur and then compare that against the path ISS travels in the same amount of time (assuming an almost circular
orbit), extrapolate it's location and you're set. You should come to stationkeeping pretty close in. This was actually
done on later Apollo missions with the LM launching from Moon and docking with the CSM ! The latter part of the
calculus even I could do :) But the former part involves integration if we didn't have the option to test drive it and can
be pretty tricky :wor:

Been trying to do this before, but manual launch creates too much of an unpredictable launch curve, autopilot on the
other hand does not.

Enthusiastic cheer!



Post Edited ( 05-30-04 16:51 )

~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline McBrain

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Reply #28 - 30 May 2004, 14:18:35
Thanks, Doc!
Will try it right now!


Cheers,

McBrain

----------------------------------------
In a world without walls and fences, who needs windows and gates?

Offline Cracker

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Reply #29 - 30 May 2004, 15:22:59
mjd53155.4163

109sec eng. start, turbo

134 sec, gear, pitch45

167sec, 132deg hdg, pitch 45
alt 6.049
spd 279.5

232sec,pitch45, alt 22.21
spd 475.1
at this point, trim ceases to be effective, reset to null, manual pitch up to 60

358sec, pitch 60, spd 1.345, alt 98.59

466sec
pitch 0,
alt 217.9, spd 2.306

507sec,
acq ISS
pitch 0, alt 262.75, spd 2.768

679 sec, pitch 2, alt 338.9
spd 5.464
turbo off

717 sec, MECO
pitch 2, alt 342.1, spd 5.782;took off a little too soon, ISS is slightly behind, letting her catch up...

839 sec
main engine restart, pitch 17, alt 322.8, spd 5.812;using docking hud cross in circle to null deltaV...
MECO
still letting her catch up a little, now 82.57k away, deltaV 1.197k

1017 sec
deltaV nulled, dist to ISS 102.5, re-orient  and main eng at 30%

1132 sec
dist 71.66k deltaV446.9

1174 sec, main @ 100%
51.07k, 592.5 DeltaV

1225 sec
re-orient facing away from ISS, dist 20.5k, DeltaV 591, mains @turbo 'til deltav near zero.

1530 sec, dist 30m

pretty sloppy, I left a minute or so too soon.
25-1/2 minutes to station-keeping.

Engineer involved in infrastructure improvement and repair.

Offline DocHoliday

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Reply #30 - 31 May 2004, 00:14:40
Damn, I'm getting too old for this :)

Been tampering with the PRO903 file for a while now. The damn curve always overshoots. I have no patience to fly
manually and record what I do. Must be a mathematical way to compute this. (my variatrion of lazy!) I tried extending
the original plan, just doubling all the altitudes above 40000m but it starts to pitch down too late then..

Anyone ahead of me on this AND willing to share the secret?


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline Cracker

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Reply #31 - 31 May 2004, 00:22:09
Obviously I'm not doing it "right", as I have to spin around and decelerate with full throttle (turbo) to null out my
relative velocity. I did manage to attain station-keeping with ISS in just over 16 minutes this morning, though. It's just
the "motor-head" coming out in me.

Engineer involved in infrastructure improvement and repair.

Offline DocHoliday

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Reply #32 - 31 May 2004, 00:57:51
Well, the "right way" is to achieve an identical orbit to the ISS's and when you cut your engines be like 400m away
from the ISS.. that's the elegant way, but not the fastest tho. Just like in the diagram I posted.

You guys are probably just taking off, with blazing engines in an attempt to catch the station and end up in a highly
elliptical orbit or a ballistic course back to earth and spend a lot of fuel to get to station-keeping. Fast but costly.

Argh. Need to keep trying.


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline schumanna

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Reply #33 - 31 May 2004, 11:06:52
Quote
DocHoliday wrote:
http://orbiter.vidmar.org/images/DG3-ISS-direct-ascent.jpg

Sorry for the shabby graphics, I'm not a pro with Photoshop either.


DocHoliday very nice work.  That is a perfect example of good work and understanding of a flight path and your
graphics are great.  I must really study it more and figure out the perfect time when to lunch etc..
I never really gather the data when I fly like most of you have but I will :)
It is interesting to see what other ppl do so I and others can maybe learn from it. :)  Or? haha

When I take of I usaly make sure my ECC 0.000 or close anoff and a then I  lin up my Orbit with the station.  I am usaly 44100 km away from the station so I dont know if that is really right.  It usaly takes me 4 orbits to catch up.  Now that has gat to be rung right?



Post Edited ( 05-31-04 11:11 )

Owner of Astroide Chiron and Alpha Centaury

"Just because I don't care doesn't mean I don't understand". quoting Homer Simpson

Du & Ich...(Orbiter)...heißt, niemals alleine zu sein

Offline DocHoliday

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Reply #34 - 31 May 2004, 12:11:07
Yo Schumanna,

Yep, learning is one of the strongest aspects that keeps me personally attached to this community. I do object thou:
if my understanding were perfect, I'd have a solution by now and Dan would credit me for the ascent program in the
official DG3 release :) Thanks anyway.

Well, I won't go into the docking details here, because I don't know it all from the top of my head, besides a lot of
good tutorials are available but scattered around the community sites. I assume you read the Orbiter's own manual,
but just to repeat the procedure that you normally must follow. Take off, get to a circular orbit, change the plane so
your RInc is 0 deg or as close to that as possible. Then the fun begins. The orbit sync is one of the most complex
maneuvers in LEO in my opinion, appart maybe from reentry. Mainly because there are many way to do it. Different
people will go with different ones. I usually go for the safe and accurate versions. So I increase my apoapsis very
much - preferably so that I catch the ISS on my next pass through the periapsis. Which means my periapsis must be
quite close or on one of the ISS's extreme points (apoapsis or periapsis, it pretty much the same) when I start the
burn. At the apoapsis I again perform small RCS burn to again sync the interception time and possibly altitude of the
periapsis to match ISS's altitude at that point as much as possible. You can be creative and use prograde, retrograde
and even inward (left) and outward (right) thrusts. Just stay off the up/down thrusts, so you don't mess up your
RInc.  :) After one orbit I act as if I couldn't care less about docking to the ISS. I just make sure I end up in an
identical orbit to the ISS. Same apoapsis, periapsis, posibly also the positions of these 4 points should overlap. Only
then do I switch to docking and I can sometimes find myself as close as 500m from the ISS. The main reason why I do
this is because if you don't, you will experience all kinds of phantom velocity vectors. They happen because your
orbits are not equal and your vessel starts "to feel" the tendency to follow its true orbital path again after the
interception points is behind you. If the orbits are identical, you actually stay put where you are only mildly wobbling
around the ISS and you can take your sweet time to approach and dock. I think I learned this logic from Duncan
Sharpe or some other old space shark ages ago :) It takes a bit of practice and feeling, to know when exactly to start
the retro burn for apapsis reduction. The goal is to keep your periapsis where it was before the burn, so timing the
burn to start half burn time before your reach the periapsis is crucial. BurnMFD helps a lot with this.

Anyway, some other people prefer to dive and catch the station. But you can't dive indefinitelly, but you can raise
your orbit enough to catch the ISS. Of course if the station is ahead of you to begin with, it might take a looong orbit
for it to catch up with you. Just a matter of style I guess.

Anyway, this came out a lot longer than I planned. I am working on the ascent program, and I almost have it set to
MECO at 340km, then the actual test with the ISS will take place ;) Then I publish my findings :)

Cheers,


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline Schimz

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Reply #35 - 01 June 2004, 10:01:42
Here is mine :

http://www.orbithangar.com/searchresults.cfm?Catagory=default&OrbVer=default&Submit=Get%
2BResults&search=IssRun

Default DGIII to Iss (29 october, launch 15:50)

Delta gilder set with Mark V engines, huge fuel and 4 passengers.

time : 57min

/!\ due to the hi-speed during the flight (45000km/h), instrumental navigation is not recommended (waste of time),
use panels just for information.


Offline Schimz

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Reply #36 - 01 June 2004, 10:02:36
sorry double
Here is mine :

http://www.orbithangar.com/searchresults.cfm?Catagory=default&OrbVer=default&Submit=Get%
2BResults&search=IssRun

Default DGIII to Iss (29 october, launch 15:50)

Delta gilder set with Mark V engines, huge fuel and 4 passengers.

time : 57min

/!\ due to the hi-speed during the flight (45000km/h), instrumental navigation is not recommended (waste of time),
use panels just for information.



Post Edited ( 06-01-04 10:07 )


Offline DocHoliday

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Reply #37 - 01 June 2004, 16:16:30
I GOT IT! I GOT IT!!!!

THE ISS DIRECT APPROACH ASCENT PROGRAM!! :)

I'm openning a new thread. It think it's worth it!

Cheers,


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline Schimz

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Reply #38 - 02 June 2004, 11:15:07
10min better.
I think that must be feasible in 40min


Offline DocHoliday

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Reply #39 - 02 June 2004, 11:20:14
It is. I have it at 38 minutes, give or take one depending on your docking skills and speed. The nice thing, it is
repeatable and totally effortless.


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline Schimz

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Reply #40 - 02 June 2004, 11:25:26

the key is the retro burn


Offline DocHoliday

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Reply #41 - 02 June 2004, 22:46:24
actually in my case.. the plane change burn :)


~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15

Offline Schimz

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Reply #42 - 03 June 2004, 12:32:59
do it manually (w only the map MFD) during the 2 burns !

« Last Edit: 03 June 2004, 12:58:35 by Schimz »

Offline DocHoliday

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Reply #43 - 03 June 2004, 12:58:35
nah, too lazy for that :)


« Last Edit: 03 June 2004, 12:58:35 by DocHoliday »
~~~

"Mood is a matter of choice. I choose to have fun!" -Vidmarism No 15