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Author Topic: LVDC++ targeting?  (Read 2416 times)
eddievhfan1984
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« on: June 01, 2014, 06:51:45 PM »

As a curiosity, I enabled the LVDC for AP7. Works relatively fine, but how do you get the program to retarget its orbital parameters? By default, it injects the vehicle into a 100x100 nm orbit, which is the parking orbit for TLI, but 7's orbit was around 120x150 nm. How do I do this?
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meik84
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« Reply #1 on: June 02, 2014, 02:12:16 PM »

Jupp, that 100 x 100 nm orbit is in for testing. Don't know any easier way to see if what I'm doing is right. Wink
Anyway, you've got to change e (the eccentricity), f (true anomaly) and C_3 (vis-viva energy at cutoff). I had the parameters for AP7 somewhere, just can remember where. Ashamed I'll dig around and come back.
Oh, and be warned: I don't know what happens if you sep the CSM from the SIVB. That's not implemented yet.
Edit: try: e = 0.004, f = 0 (never explicitly stated, but sensible), C _3 = - 60157329. I'm really anxious about the results. Wink
And don't forget to recompile after changing; you wouldn't be the first to wonder.*whistle*
« Last Edit: June 02, 2014, 02:33:49 PM by meik84 » Logged
eddievhfan1984
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« Reply #2 on: June 02, 2014, 09:20:22 PM »

Thanks. Maybe I could find a way in the code to accept the external scenario variables and convert it into the necessary targeting parameters. Wink
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eddievhfan1984
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« Reply #3 on: June 23, 2014, 03:48:51 PM »

Regarding that above post, which header/source file handles the transfer of pad loads/scenario data from the scenario file into the various routines?

Edit: I just tried out your values. Placed me in a near-circular 136 nm orbit. I also noticed a left yaw of about 5-10 degrees upon IGM start. I can try my own vis-viva calculations, but IDK what the pad radius (which I understand the LVDC and AGC used as Earth's radius reference) is for that.
« Last Edit: June 23, 2014, 09:11:32 PM by eddievhfan1984 » Logged
meik84
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« Reply #4 on: June 24, 2014, 05:36:29 AM »

I forgot to mention that e, f and C_3 are set to AP8's values somewhere below in the code. Delete those and it should work. It does for me at least.
The yaw might come from the unsolved problem with the IMU/gravity calculations. LVDC's state vector at cutoff is quite off in crossrange, but I don't know why.
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eddievhfan1984
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« Reply #5 on: June 24, 2014, 04:26:46 PM »

I commented those values out, actually. I can do the work myself, but it would be really helpful if I knew what the reference pad radius was, so I can make sure I'm setting the C_3 correctly.
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eddievhfan1984
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« Reply #6 on: July 04, 2014, 06:27:40 AM »

So, I managed to do a successful test flight, using the C_3 and eccentricity values for 120 x 150 nm. It put me in an orbit more like 129 x 136.

Here's my targeting parameters:

C_3: -60202271.22105 J/kg (Math cross-check is good, double the vis-viva energy of the orbit and such)
e: .00418 (Math cross-check means it should be .00421, but would that be a significant error?)
f: 0 (This is probably only important if we want to satisfy the conditions of a Mode IV abort—V_I >22 200 fps, h-dot >160 fps, and h >100 nm)

It is a touch perplexing. And due to a saving quirk, every time I save the launch scenario, the launch vehicle is somewhere else on Earth in the reload, so I have to do all the launch checks from T-4 hours every time I tweak targeting parameters. >.<
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meik84
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« Reply #7 on: July 04, 2014, 02:07:28 PM »

Hm. With my parameters, I get 149.6 nm x 122 nm. It even cuts off at exactly +10:20, just like the real one. Shocked
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And due to a saving quirk, every time I save the launch scenario, the launch vehicle is somewhere else on Earth in the reload, so I have to do all the launch checks from T-4 hours every time I tweak targeting parameters.
Did I really upload a version with 'armed' load/save routines? At least you are getting the same error I get. And it drives me nuts, because I don't get the cause. I've revised the EMS a little bit, but I can't release it to the masses because I had to change the load/save routines. Guess what -when I save and load with the 'new' EMS, the rocket is somewhere on earth doing crazy things. Evil or Very Mad
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eddievhfan1984
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« Reply #8 on: July 04, 2014, 06:41:26 PM »

Well, I loaded all the data in the correct place in LVDC.cpp. I even did the same thing in the Saturn V code just for thoroughness, so I'm rather confused by this.

Do you have any pre-launch scenarios I can use so I don't have to do the 4 hours again?

Also, what's newly featured in the EMS? Very Happy
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meik84
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« Reply #9 on: July 05, 2014, 08:40:37 AM »

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Well, I loaded all the data in the correct place in LVDC.cpp. I even did the same thing in the Saturn V code just for thoroughness, so I'm rather confused by this.
See below. I'm not lying. Wink
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Do you have any pre-launch scenarios I can use so I don't have to do the 4 hours again?
Take the one below. You could also do the whole prelunch stuff with a 'normal' scn, save when you are ready (but don't save after t -1:00 -LVDC needs the GRR trigger and won't lunch otherwise) and just add the infamous line to the scn.
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Also, what's newly featured in the EMS?
Oh, there where some minor things. Some thing wasn't implemented correctly, you couldn't follow the checklist at one point (forgot which point, though). I've also added some dV test/VHF ranging instructions to the scrolls and increased the number of th reentry test patterns to the right value.


* cutoff.gif (479.96 KB, 1440x900 - viewed 246 times.)
* Apollo 7 Virtual AGC - LVDC.scn (83.26 KB - downloaded 114 times.)
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eddievhfan1984
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« Reply #10 on: July 05, 2014, 09:31:37 PM »

LOL I wasn't implying deceit, good sir. Just trying to figure out why my own performance is messy.

EDIT: I ran it again, double-checking my values. I got a perfect 133 x 134. I even changed the targeting parameters in TABLE_15 for good measure (since they could've overwritten the presets). When you load in the targeting values, do you use the preset/initialization variables, TABLE_15, TABLE_25, or is there some other targeting variable set I haven't noticed?
« Last Edit: July 06, 2014, 02:47:14 AM by eddievhfan1984 » Logged
meik84
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« Reply #11 on: July 06, 2014, 01:05:56 PM »

As I said, verify that e, f and C_3 aren't set to any different value later in the code. Look especially for e = 0 and such stuff.
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eddievhfan1984
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« Reply #12 on: July 06, 2014, 08:31:11 PM »

I think I found it. e and f are reset to 0 in the area of the code concerning runtime variables. Let's see if I can score this time.

EDIT: Definitely a step in the right direction. Got 118.3 x 147.4, V_I 25 563 fps at cutoff. \m/
« Last Edit: July 06, 2014, 08:47:53 PM by eddievhfan1984 » Logged
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