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Tschachim
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« on: May 02, 2007, 04:19:01 PM »

Hi Apollo fans,

I was curious if it's possible to land the LM on the Moon and return to the Earth with the latest Beta 20070429. The LM internal systems are still in an early stage of development, so I don't expect to use the LM realistically or historically correct, just land and fly back "the Orbiter way". Since it looks like I'm not the only one interested in that I decided to post a kind of "journey diary". Happy

I decided to use the Quickstart Mode because I don't want to have much work in the CSM, for the LM there's not much difference to the Standard Mode anyway. Also I used Apollo 14 because of the nicer landing site compared to the flat Apollo 11 site. So at first I fixed the "Scenarios\Project Apollo - NASSP\Quickstart Missions\Apollo 14\Apollo 14 - Launch" scenario, which is already committed to CVS, and here we go:



During prelaunch and launch I did nothing except turning on time acceleration and the Saturn V put me in a nice Earth Parking Orbit of 185.4 x 183.2 km as intended. I continued with the TLI burn using IMFD 4.2.1 (not 4.6) as explained in the wiki. This was my IMFD screen directly after burn calculation, the use of a 2nd IMFD in map mode is optional, but very informative (and accurate!)



I did the burn using the IMFD autoburn feature and the burn was just perfect, the IMFD map mode reported after the burn that I'll directly crash into the center of the Moon. That's not something I actually want to do Wink, but I'll correct that later.

LV seperation, transposition, docking and LM extraction was routine, again I did it as explained in the wiki. And here's the CSM/LM stack on the way to the Moon:



Up to now the mission wasn't very exciting, everything was working fine as documented and expected and Trans Lunar Coast was even more boring Wink, I did just nothing, not even PTC, and used time acceleration 1000x until the automatic "it's time for correction" call happend at about T+60h.

The IMFD map mode still showed a direct Moon impact and now with the first Mid Course Correction (MCC) I really should fix that. Since I left the "well documented mission phases" I had some more work to do. I used the IMFD Base Approach program with the Moon as reference, "Fra Mauro-Base" as target (you need to type that actually), altitude 110k, approach for "Orbit-Insert" and a time to ejection of 300s (to have enough time before the burn) which resulted in the following screen, the use of a 2nd IMFD in map mode is optional again:



Two things are important to do before activating the IMFD autoburn feature:

- Switch both SIG COND/DRIVER BIAS POWER switches on panel 7 (left) to OFF, otherwise the RJ/EC will "overwrite" IMFDs attitude commands.
- Orient the CSM/LM stack manually using the IMFD Burn Vector (BV) screen, IMFD has problems orienting the bulky stack properly.

After that's IMFD did the burn correctly. Approaching further to the Moon I noticed that the Base Approach program showed a decreasing periapsis altitude (and so an increasing burn time), the IMFD map showed a negative (but stable) periapsis altitude. So I did my 2nd (and last) MCC burn more smart. Wink I waited until I was inside the lunar SOI at about T+75h and used the same Base Approach program configuration as before, but adjusted my altitude until I had an periapsis altitude of 110 km on the IMFD map (Plan button, blue trajectory). I ended up with an altitude of about 200 km in the Base Approach program. This worked great for the map mode and in the reality.

Next step is LOI, which is rather simple since here LazyD's "autopilot coverage" begins. There are a couple of Simple AGC programs both for the CSM and the LM explained in the LMDoc.txt file in your "Doc\Project Apollo - NASSP" folder. LOI is program P16, which I started about an hour before periapsis:

SIG COND/DRIVER BIAS POWER - AC1, AC2 again
SC CONT - CMC
dV THRUST A - NORMAL
DSKY: V37E 16E

The DSKY shows:
   R1=time to ignition(before ignition)/time to cutoff(after ignition)
   R2=altitude xxx.x km
   R3=offplane distance xxx.x km

Time acceleration can be used until the burn starts. Everything runs automatically, I just did nothing (again) and watched the burn from outside:



The burn took place at about T+80h, I ended up with a quite low orbit, 133 x 49 km, but I decided that this is fine for now (the Moon has a spherical gravity field in Orbiter, no MASCONs). I had 30% SPS propellants left, we'll see if I come back with that...



So far, so good. I didn't expect any major problems up to now with the CSM only, of course. I now changed to the LM and did the following LM activation procedure:

In the LM:

DESCENT POWER, HI VOLTAGE 4 x ON (talkback gray) on panel 14 (<CTRL><RIGHT> twice from center panel)
MAIN SOV, SYS A/B 2 x OPEN (talkback gray) on panel 2 (center panel)
ENGINE ARM - DES on panel 1
EXPLOSIVE DEVICES, MASTER ARM - ON on panel 8 (<CTRL><LEFT> twice from center panel)
EXPLOSIVE DEVICES, LDG GEAR DEPLOY - FIRE (talkback gray)
DSKY: PRO, V37E 00E

That's all, the LM should be up and running (at least in an "Orbiter sense"). It doesn't matter if you're docked or not, so you can deploy the landing gear after undocking, too. I decided to do an "Apollo 11 style" landing (undocked LM does the DOI burn), because I want to test the LM. So next step was undocking:

Back in the CSM:
DOCKING PROBE - unguard, EXTD/REL

Now I wondered how the LM will perform in it's first burn, the Descent Orbit Insertion (DOI).
In the LM again, enter in the DSKY:

V37E 17E
V16E (to show the countdown)

The DSKY shows:
   R1=Number of passes BEFORE landing
   R2=MM SS minutes and seconds to plane change burn, or seconds if more than -99 minutes
   R3=Burn dv m/s MM.M

I used time acceleration until be burn began and it really worked fine, periapsis altitude 15 km:



Next I did the landing site alignment burn, which is only necessary if our offplane distance is greater than 24 km, but I wanted to check that anyway:

V37E 18E
V16E (to show the countdown)

The DSKY shows:
   R1=Number of passes
   R2=MM SS minutes and seconds to plane change burn, or seconds if more than -99 minutes
   R3=Burn dv m/s MM.M

In my case it was a really short burn, I don't know if it was really necessary. And now the really interesting part, the landing. About 1000km before the landing site I entered

V37E 63E

Well, and then I did what I have done most of the time: Nothing! Wink



...and the LM landed just perfect! The landing and lunar EVA is also explained in the wiki, so no need to talk about LDP etc. here, but of course I visited Cone Crater with the rover, which Big Al unfortunately didn't had in the real Apollo 14 mission... Happy

Looks like the LM works very well, I can provide some intermediate scenarios if wanted, but altogether it wasn't that big deal thanks to LazyD's great autopilots and Jarmo's IMFD, next we'll see if I come back to Earth, too.

To be continued...

Cheers
Tschachim
« Last Edit: June 07, 2007, 05:17:11 PM by Tschachim » Logged

Christophe
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« Reply #1 on: May 02, 2007, 06:12:09 PM »

Woaahhh!
I don't know how the hell you find the time to do all this for the project! Rolling Eyes
It's great.
Congratulations !  Thumbs Up

Hope we could do that with the vAGc, the "right way" very soon...
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slaintemaith
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« Reply #2 on: May 09, 2007, 12:43:07 PM »

Hrm.  Couldn't have been with the latest version.  When I ran that scenario the rocket wasn't aligned properly on the pad.  =P

I did, however, follow the footsteps of your mission and am happy to say it works just as described.  =)
And have I mentioned that I -really- like the LEM progams?  Can't wait until everything can be done with the AGCs in the CSM/LM.

Keep up the inspiring work, gentlemen!
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Tschachim
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« Reply #3 on: May 09, 2007, 02:25:17 PM »

When I ran that scenario the rocket wasn't aligned properly on the pad.

You need to do a "CVS Update" of your scenario folder.

Cheers
Tschachim
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Odyssey
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« Reply #4 on: May 10, 2007, 05:58:51 AM »

Tschachim.

Thats great work, well done. I have two questions.

1. Can all that you have explained be achieved using the standard mode?

2. If you use Transx for TLI can you still use the DSKY actions you described when doing the DOI and landing. For example, can I just target the base in the Map MFD and it will still work?

Thanks

Odyssey  Wink
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Odyssey Wink
Tschachim
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« Reply #5 on: May 10, 2007, 06:32:45 AM »

1. Can all that you have explained be achieved using the standard mode?

Yes, it's a lot of more work in the CSM, but not much difference in the LM (you need to press PRO a couple of times during a few Simple AGC programs, see LMDoc.txt).

2. If you use Transx for TLI can you still use the DSKY actions you described when doing the DOI and landing.

Yes, for DOI and PDI it's important where you are, not how you managed it to get there.

Cheers
Tschachim
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Odyssey
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« Reply #6 on: May 10, 2007, 05:39:51 PM »

Excellent. I'll give it a try and now doubt be asking yet more questions along the way  Ashamed

With regards to the LEVA, is it possible to this in standard mode? I know that with quickstart mode you can just press 'E' but do I have to do anything more in standard mode?

Thanks

Odyssey Wink
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Tschachim
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« Reply #7 on: May 11, 2007, 04:43:24 AM »

With regards to the LEVA, is it possible to this in standard mode? I know that with quickstart mode you can just press 'E' but do I have to do anything more in standard mode?

The 'E' key is working in Quickstart mode only, no lunar EVA in Standard mode currently, sorry. We'll do that later, of course, but since there's a lot of work to do in the LM it will take some time.

Cheers
Tschachim
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Odyssey
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« Reply #8 on: May 11, 2007, 01:58:07 PM »

That's a shame. When do you expect the LEVA ability will be implemented?
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Odyssey Wink
slaintemaith
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« Reply #9 on: May 11, 2007, 06:03:37 PM »

Any luck with getting home?  I'm finding the LM ascent programs to be ....well....  not as happy as the descent programs.
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Tschachim
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« Reply #10 on: June 13, 2007, 03:07:12 PM »

Hi Apollo fans,

after a loooong stay on the Moon it's time to return to Earth. Unfortunately this is not possible with the beta release used for the outward journey, so you need to update to the latest Beta 20070607 as explained here. There's no scenario incompatibility, so you can continue with a saved scenario. I personally started again from Earth, I had only 30% SPS fuel left, which was a little bit too less to return to the Earth properly, I needed to use the RCS for the TEC MCCs. It turned out that the LM was a little bit too heavy, additionally my TLC MCCs weren't perfect.

Launch, TLI and Transposition & Docking was the same. But this time I did only one MCC, again I waited for the automatic "it's time for correction" call happening at about T+60h. I again used the IMFD 4.6 BaseApproach program with the Moon as reference, "Fra Mauro-Base" as target (you need to type that actually), altitude 115k, "retrograde", approach for "Orbit-Insert" and a time to ejection of 600s (to have enough time before the burn). Then I used the IMFD map in plan mode to check the predicted trajectory and saw that my PeA (periapsis altitude) was much too low. So I increased the altitude in the BaseApproach program so that the map program (which is much more precise than any other prediction tool, including TransX, Transfer etc.) predicts a PeA of 115k (the screenshot shows 109.71k, but 115k would be better). So I needed just one quite small MCC (still bigger than the real ones):



The BaseApproach screen is already in burn vector (BV) mode, sorry. Perhaps I'll provide more comprehensive Quickstart Mode checklists similar to the TLI checklist for that in the wiki later.

Also the Simple AGC program P16 for the LOI burns is a little bit different now. Start P16 the same way as before, but now the first LOI burn (LOI1) stops earlier, so if your PeA was about 115 km before LOI1, your resulting orbit will be about 115 x 315 km. Apollo 11 and 12 then did a LOI2 burn to achieve a roughly circular orbit. To do that just execute P16 again at about 20min before next periapsis, your resulting orbit will be about 110 x 120 km. After LOI2 I had 35.6% SPS fuel left, which is fine for return to Earth. Apollo 14 and later didn't do a LOI2 burn but the DOI burn directly with the complete CSM/LM stack. That should be possible by using P17 in the CSM, but I didn't try that.

LM activation, undocking and landing was the same, so nothing noteworthy here. After landing I suggest to use the rover to visit Cone crater, thanks to Redburne the rover has great wheel and gear animations now:



Now it's really time to return back to the Earth. Make sure that the LEVA astronaut is back in the LM again (the rover is left behind on the Moon) and switch to the LM cockpit. Open OrbitMFD or MapMFD, select the CSM as target and wait until the CSM is about 1/4 orbit before passing over the landing site (i.e. you in the LM). Then do the following:

ENG ARM - ASC (panel 1)
Key in DSKY: V37E 12E

DSKY's R1 shows countdown to launch, you can use time acceleration up to about 1 min before launch, then switch back to 1x and, well, just do nothing. The LM ascent stage will separate, launch and put you in into an elliptical lunar orbit about 18 X 82 km, and close to coplanar with the CSM. After that the Simple AGC runs P34, the Transfer Phase Initiation (TPI) program. Please note that Apollo 11 and 12 used the coelliptic rendezvous procedure, which involves P32 and P33 before that, but I didn't try that. P34 shows a countdown to ignition:

R1: xx hours
R2: xx minutes
R3: xx.xx seconds

Again you can use time acceleration until about 2 min before the burn. P34 starts P42 automatically, which does the burn using the ascent engine. After that the Simple AGC runs P35, the Transfer Phase Midcourse (TPM) program. Again a countdown is displayed, this time the burn is executed by P41 using the RCS. After that P35 is executed again for the 2nd TPM burn, same procedure as usual.

At last the Simple AGC switches to P36, a fictitious program doing the final braking and station keeping. In reality this was done by the astronauts manually, and you can do it manually, too. Terminate P36 by keying V37E 00E, after that you can control the LM using Orbiter's rotational and linear RCS modes. But be careful with the linear RCS, the LM ascent stage uses the real LM thruster positions, which are the same as the descent stage (obviously) and aren't aligned with the center of gravity, so a lot of torque is produced and you need to compensate that.

P36 does all that automatically, I just did nothing during the complete ascent and rendezvous (as usual Happy). The DSKY shows

R1: Range x.xx km
R2: Rate x.x m/s
R3: Phase x.xx deg

During P36 I don't recommend time acceleration (or only in the beginning and 10x max.) and after a couple of minutes the LM will come to a stop with windows facing the CSM at a distance of 10 m. When velocities are damped, which again will take some time, but now time acceleration up to 10x is OK, the LM will pitch forward to present the docking port to the CSM. Change to the CSM and rotate it to "docking attitude". Then change to LM again and key V37E 00E. Finally change to CSM, give some linear forward RCS thrust and the CSM will capture and hard dock automatically, the trip to the lunar surface is finished.

Now it's time to return to the Earth with the CSM, so at first we need to get rid of the LM ascent stage:

CSM/LM FINAL SEP 1 (or 2) - unguard, up

For the trip home we'll do one big burn to leave lunar orbit, the TEI (Trans Earth Injection) burn, then do a couple of MCCs during Trans Earth Coast (TEC) and finally enter Earth's atmosphere for braking and landing. We won't enter Earth orbit, there's no "EOI" burn, so already the TEI burn aims at the landing (splashdown) point (or better the entry interface, a virtual point at which entry begins). Basically I did that using IMFD 4.6 as explained here or here using the following parameters:

Lon: -172W
Lat: -27S
Alt: 121.95k
ReA: 6.5
Ant: 21

Lon/Lat define the landing site, I hope I found the correct coordinates for Apollo 14. Again I used the IMFD map to optimize the burn in order to save fuel, which leads to the usage of 3 MFDs simultaneously, use the MFDs on the G&N panel below panel 122 for that.



This time I aimed for a PeA of 35k (this will be close to the real PeA when you are near enough to the Earth so that BaseApproach works precisely) and changed BaseApproach's Alt from 121.95k to 2.758 M by playing with this value to achieve that. Please note that Ant is wrong in this screenshot, it should be 21.

I had the problem that the map was jumping between this display and "invalid burn data", I don't know how to avoid that, so help is very much appreciated. Happy

I did the burn using IMFDs auto burn feature, but before that the RJ/EC needs to be disabled again:

SIG COND/DRIVER BIAS POWER 1/2 - OFF (panel 7)

I did the MCCs as explained here here and again used the map for "altitude correction", still aiming at a PeA of 35k. In order to hit the entry interface (a virtual point in 121.95 k altitude, 21 before the landing point, if I understand IMFD correctly), not only the PeA but also the position of the periapsis (and so of the entry interface) is important. Unfortunately I'm not able to calculate that from the map data, so I did more MCC burns, the first burn when I entered Earth's SOI and then 2 or 3 more burns, the last one only a couple of hours before arrival. During the first burns you'll notice that the predicted PeA in the map is changing quite rapidly, so you need to guess an altitude so that PeA is about 35k when the burn starts. During the last burn it shouldn't be necessary to change the altitude from 121.95k, PeA should be about 35k anyway and the entry interface position will be fine after that burn, too.

About half an hour before periapsis (PeT) I began with the entry procedure, thanks Chode the Simple AGC does all the work:

Key V37E 61E

Flashing V06N61
         XXX.XX   Impact Latitude
         XXX.XX   Impact Longitude
          +/-1      RollCode

Latitude and longitude are calculated based on a nominal reentry down-range (historical), and zero cross-range and should be close (i.e about +/- 1) to the target landing site, -27S  and -172W. Next I changed the predicted values to the target values:

V21E
-02700E
V22E
-17200
PRO
PRO

Flashing V06N60
         XXX.XX     Predicted maximum G force
         XXXXX m/s  Predicted velocity at entry interface
         XXX.XX     Entry angle

Enter PRO:

Flashing V16N63
         XXXX.X     predicted range from 0.05G to splash
         XXXXX m/s  predicted Velocity at 0.05G
         XX  XX     min  sec   until 0.05G

I waited until R3 is at about 10 min, then PRO, program advances to P62

Flashing V50N25
         00041      Checklist Code (perform CM/SM separation)
      
I did what the AGC told me:

AUTO RCS SELECT (16) - MNA or MNB (panel 8 )
SIG COND/DRIVER BIAS POWER 1/2 - AC1/2 (panel 7)
S/C CONT - CMC (check) (panel 1)
ELS LOGIC - unguard, up
CM RCS PRPLNT 1/2 - up, talkbacks gray (panel 2)
C/W CSM - CM
MAIN BUS TIE (2) - up (panel 5)

... and ...

CM/SM SEP 1 or 2 - unguard, up

... and the CM separates from the SM. After that the AGC controls the CM during entry, Chode explains that here like this: 

Enter PRO:

Flashing V06N61
         XXX.XX   Impact Latitude
         XXX.XX   Impact Longitude
          +/-1    RollCode

Last chance to change the landing point (V21-25).

Enter PRO:

P63 takes over, display shows:

Flashing V16N64N
         XXX.XX     Drag Acceleration
         XXXXX m/s  Inertial velocity
         XXXX.X km  Range to splash

Attitude hold is engaged to orient correctly for entry interface. When Drag acceleration reaches 0.05G, program automatically advances to P64.

P64 (nominal)

If entering from Earth orbit (with entry angle around 2 to 3 degrees), should proceed to program 67.

If entering from trans-lunar orbit (with entry angle around 6 to 7 degrees), should stay in P64, attempting a constant drag level until sufficient energy is lost, then the AGC advances to P67.

P67:

Flashing V16N66
         XXX.XX deg   Commanded Bank Angle
         XXXX.X km    Downrange Error
         XXXX.X km    Crossrange Error

When your velocity drops low enough, P67 shuts off the control jets and displays:

Flashing V16N67
         XXXX.X km    Range to target splash
         XXX.XX deg   Present Latitude
         XXX.XX deg   Present Longitude
      
At about 7.5 km altitude the apex cover (forward heat shield) is jettisoned automatically and the drogue chute is deployed, at about 3.2 km altitude the main chutes are deployed. At 0 km altitude splashdown happens (what a surprise Wink ), the main chutes are released automatically. Press "J" after landing to open the hatch and "J" again to enter the raft.
 


I had a quite smooth entry with about 8g maximum, range to target landing point was 7.7 km, I assume this is very well within the reach of the recovery forces.

Well, that's all, this time much more bugfixes and changes were necessary to complete the mission, so it wasn't that relaxing than the journey to the Moon, but I hope it's now possible again to fly complete Moon landing missions, not really historically correct, especially in the LM, but at least the "Orbiter way". Comments and suggestions are welcome as usual. Happy 

Cheers
Tschachim
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bluespace88
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« Reply #11 on: June 13, 2007, 04:02:31 PM »

Awesome tutorial  Thumbs Up

Just a question.  Would IMFD 4.2.1 still work in this case, because I recall 4.6 having autoburn problems.

Looking forward to coming home, which I haven't done in a while since NASSP 5.0
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Tschachim
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« Reply #12 on: June 13, 2007, 04:39:23 PM »

IMFD 4.2.1 is also working except for the "3 MFD stunt" for TEI, 4.2.1 supports only 2 MFDs, but you can still use Orbit-Eject together with BaseApproach, of course. But I only had Autoburn problems during TLI and I'm not sure if I did something wrong, I need to recheck that sometime, so I suggest 4.6 at least after TLI.

Cheers
Tschachim
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michaelrad55
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« Reply #13 on: June 15, 2007, 05:10:31 PM »

I have two questions.  How much propellant do you suggest I have left for the return ride home?  I have about 30% left.  I'm probably going to go back before the first MCC call-up and try optimizing better now that I know i can get to the moon.  Second, how do I get on the lunar rover?  Thanks
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Tschachim
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« Reply #14 on: June 15, 2007, 05:25:41 PM »

30% is tight, 35% should be fine. Press V to spawn the rover while the astronaut has the focus (Quickstart Mode only): http://nassp.sf.net/wiki/LM_landing_checklist_%28Quickstart%29

Cheers
Tschachim
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