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Old 09-27-2012, 01:22 PM   #16
boogabooga
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Dgatsoulis, that Apollo article was a great read. I understand better how flytandem was using the out of plane orbit.

So, if I understand correctly, Apollo used an out-of plane but mostly prograde TLI and then made a plane change for landing point alignment during LOI, which is exactly opposite of how I am doing it. This was to maintain a free return trajectory, and also because not having an in-plane launch allowed for a 2.5 hour, rather than instantaneous launch window.

There is no weather in Orbiter we don't need long launch windows so launching in-plane I think is the way to go. Nor do we need to be confined to free return. The original question was how to make the ejection burn with inclination change, so that you arrive on the Moon, passing over the required base already, with no inclination burn on SOI required. With a traditional approach, this is certainly possible and I think the best way to go is by offsetting the moon at TLI, which I demonstrated in IMFD.
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Old 09-27-2012, 02:37 PM   #17
dgatsoulis
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Quote:
Originally Posted by boogabooga View Post
 So, if I understand correctly, Apollo used an out-of plane but mostly prograde TLI and then made a plane change for landing point alignment during LOI, which is exactly opposite of how I am doing it. This was to maintain a free return trajectory, and also because not having an in-plane launch allowed for a 2.5 hour, rather than instantaneous launch window.
Yes, that's pretty much it. There were many restrictions: flight time, free return trajectory, long launch windows to overcome weather issues and so on. In a sense it wasn't the spacecrafts that chose the landing sites, rather the landing sites chose the spacecrafts+restrictions.

Quote:
The original question was how to make the ejection burn with inclination change, so that you arrive on the Moon, passing over the required base already, with no inclination burn on SOI required. With a traditional approach, this is certainly possible and I think the best way to go is by offsetting the moon at TLI, which I demonstrated in IMFD.
It's a nice and elegant way to do it, I use it myself quite often.
But the OP also mentioned potential Δv savings from flying to the moon this way instead of the usual.

What I have found is that the increased intercept velocity at the Lunar Pe, leads to a more expensive LOI burn, which almost cancels out any benefits of not having to perform the MCC for the base alignment.

In IMFD starting from a coplanar orbit, you need to mix the plane change in your prograde burn, in order to offset and you end up using more Δv. And -same as an offplane burn- you also reach moon periapsis at high velocity.

It really depends on what your goal is. If you want to make a "single burn to Brighton Beach" flight then the way you've been using is great, because it uses IMFD's superior map program, to let you now where you are, where you will be and how much Δv you'll need. (BTW you can also use the map program with TransX, but only after you've performed the burn.)

If you are a Δv budget freak (like me), you'll see that using this method isn't really any better than performing a base alignment burn.

Just my
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Old 09-28-2012, 04:59 PM   #18
boogabooga
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Hmm. I'm not noticing a big difference in cir velocity at lunar Pe.

Do you have Lunar Base Aurora? It's at 28.5 S, so I've used it as an example, instead of the extreme latitude Brighton Beach. Here is the relevant part of the config.

W-Aurora.cfg:
Code:
BASE-V2.0
Name = Aurora
Location = +42.46 -28.54
Size = 200
ObjectSize = 200
MapObjectsToSphere = TRUE
Here is a scn for a DG in the lunar plane with IMFD TLI setup, no offsets.

Code:
BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 51983.0639846748
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01S
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01S
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Orbit
  REF AUTO
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL-01S
  ActiveProg 1 1
  DataA 1 3 0 0 0 0
  DataB 3.375 1 51983.10354121545 0 0 4.932418488553791 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare -1
  mfdProgram 2
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL-01S
  ActiveProg 1 1
  DataA 1 3 0 0 0 0
  DataB 3.375 1 51983.10354121545 0 0 4.932418488553791 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare 0
  mfdProgram 4
END_MFD

BEGIN_VC
END_VC

BEGIN_SHIPS
ISS:ProjectAlpha_ISS
  STATUS Orbiting Earth
  RPOS 6160328.86 -2703959.11 -524389.16
  RVEL -2757.836 -6714.696 2493.674
  AROT -20.27 -50.93 -162.95
  VROT 0.14 -0.04 0.06
  AFCMODE 7
  PRPLEVEL 0:1.000000
  IDS 0:588 10 1:586 10 2:584 10 3:582 10 4:580 10
  NAVFREQ 0 0
  XPDR 466
  O2_TANK 100.00
  FOOD_TANK 100.00
  CFG_MONTH_O2 6.00
  CFG_MONTH_FOOD 6.00
  UCGO @@0,1,0,0,@@1,1,0,0,@@2,1,0,0,@@3,1,0,0,@@4,1,0,0,@@5,1,0,0,@@6,1,0,0,@@7,1,0,0,
END
Mir:Mir
  STATUS Orbiting Earth
  RPOS 5168755.44 -193776.31 -4235482.00
  RVEL 4844.602 428.793 5989.189
  AROT 14.74 -73.72 79.05
  VROT -0.14 0.00 0.00
  AFCMODE 7
  IDS 0:540 100 1:542 100 2:544 100
  XPDR 482
END
Luna-OB1:Wheel
  STATUS Orbiting Moon
  RPOS 2202255.60 405169.19 127.61
  RVEL -267.751 1455.289 0.073
  AROT -0.00 -0.00 107.74
  VROT 0.00 0.00 10.00
  AFCMODE 7
  IDS 0:560 100 1:564 100
  XPDR 494
END
GL-01S:DG-S
  STATUS Orbiting Earth
  RPOS -3525992.11 409486.76 -5466476.98
  RVEL 6550.240 -482.699 -4262.873
  AROT 102.60 -23.32 -127.51
  VROT -0.09 0.01 0.06
  PRPLEVEL 0:0.370139 1:0.989174 2:1.000000
  NAVFREQ 94 524 84 114
  XPDR 0
  RCOVER 1 1.0000
  RADIATOR 1 1.0000
  PSNGR 2 3 4
  TANKCONFIG 1
  AAP 0:0 0:0 0:0
END
SH-03:ShuttleA
  STATUS Landed Earth
  BASE Habana:4
  POS -82.3982414 23.0005396
  HEADING 70.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 0.0000 0.0000
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 0 0.0000
  PAYLOAD MASS 0.0 0
END
PB-01:ShuttlePB
  STATUS Landed Earth
  BASE Habana:1
  POS -82.4000000 22.9994604
  HEADING 22.00
  AFCMODE 7
  PRPLEVEL 0:1.000000
  NAVFREQ 0 0
END
GL-02:DeltaGlider
  STATUS Landed Mars
  BASE Olympus:3
  POS -135.4300000 12.7366196
  HEADING 0.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0 0 0
  XPDR 0
  GEAR 1 1.0000
  AAP 0:0 0:0 0:0
END
SH-01:ShuttleA
  STATUS Landed Moon
  BASE Brighton Beach:1
  POS -33.4375000 41.1184067
  HEADING 0.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 0.0000 0.0000
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 0 0.0000
  PAYLOAD MASS 0.0 0
END
END_SHIPS

BEGIN_ExtMFD
END
It starts out with negative PeA.
When I tried this, I used the Base Approach for MCC just outside the lunar SOI and again within the Lunar SOI and needed something like 120m/s. My circ. velocity at lunar Pe was something like 895m/s. Sure, this is higher than if I would have stayed in plane, but from what I have observed, if you must target the base, then circ. velocity is going to increase even if you do MCC closer to the moon.

Here is a setup for an offset TLI directly into an orbit to intersept the base:

Code:
BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 51983.0728067580
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL-01S
END_FOCUS

BEGIN_CAMERA
  TARGET GL-01S
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Orbit
  REF AUTO
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL-01S
  ActiveProg 1 1
  DataA 1 5 0 1 0 0
  DataB 194.6195068359375 1 51983.10355278953 0 0 4.93241848855379 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 6.143558967020042 1.455604596163268 2279141.834453923 2 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare -1
  mfdProgram 2
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL-01S
  ActiveProg 1 1
  DataA 1 5 0 1 0 0
  DataB 194.6195068359375 1 51983.10355278953 0 0 4.93241848855379 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 6.143558967020042 1.455604596163268 2279141.834453923 2 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare 0
  mfdProgram 4
END_MFD

BEGIN_VC
END_VC

BEGIN_SHIPS
ISS:ProjectAlpha_ISS
  STATUS Orbiting Earth
  RPOS 2130123.95 -6239417.40 1333193.31
  RVEL -7146.742 -1963.803 2069.423
  AROT -72.17 55.06 -133.03
  VROT 0.13 -0.06 -0.03
  AFCMODE 7
  PRPLEVEL 0:1.000000
  IDS 0:588 100 1:586 100 2:584 100 3:582 100 4:580 100
  NAVFREQ 0 0
  XPDR 466
  O2_TANK 100.00
  FOOD_TANK 100.00
  CFG_MONTH_O2 6.00
  CFG_MONTH_FOOD 6.00
  UCGO @@0,1,0,0,@@1,1,0,0,@@2,1,0,0,@@3,1,0,0,@@4,1,0,0,@@5,1,0,0,@@6,1,0,0,@@7,1,0,0,
END
Mir:Mir
  STATUS Orbiting Earth
  RPOS 6505413.57 163910.47 1306157.11
  RVEL -1593.489 446.408 7593.512
  AROT 2.66 23.63 87.05
  VROT -0.13 -0.00 0.00
  AFCMODE 7
  IDS 0:540 100 1:542 100 2:544 100
  XPDR 482
END
Luna-OB1:Wheel
  STATUS Orbiting Moon
  RPOS 1733183.90 1417797.95 169.40
  RVEL -936.909 1145.320 0.034
  AROT 0.00 0.00 170.01
  VROT -0.00 -0.00 10.00
  AFCMODE 7
  IDS 0:560 100 1:564 100
  XPDR 494
END
GL-01S:DG-S
  STATUS Orbiting Earth
  RPOS 2174335.86 -66461.22 -6148910.32
  RVEL 7349.452 -677.425 2595.920
  AROT -85.80 -48.37 120.27
  VROT -0.16 0.00 0.03
  AFCMODE 7
  PRPLEVEL 0:0.370139 1:0.989174 2:1.000000
  NAVFREQ 94 524 84 114
  XPDR 0
  RCOVER 1 1.0000
  RADIATOR 1 1.0000
  PSNGR 2 3 4
  TANKCONFIG 1
  AAP 0:0 0:0 0:0
END
SH-03:ShuttleA
  STATUS Landed Earth
  BASE Habana:4
  POS -82.3982414 23.0005396
  HEADING 70.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 0.0000 0.0000
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 0 0.0000
  PAYLOAD MASS 0.0 0
END
PB-01:ShuttlePB
  STATUS Landed Earth
  BASE Habana:1
  POS -82.4000000 22.9994604
  HEADING 22.00
  AFCMODE 7
  PRPLEVEL 0:1.000000
  NAVFREQ 0 0
END
GL-02:DeltaGlider
  STATUS Landed Mars
  BASE Olympus:3
  POS -135.4300000 12.7366196
  HEADING 0.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0 0 0
  XPDR 0
  GEAR 1 1.0000
  AAP 0:0 0:0 0:0
END
SH-01:ShuttleA
  STATUS Landed Moon
  BASE Brighton Beach:1
  POS -33.4375000 41.1184067
  HEADING 0.00
  AFCMODE 7
  PRPLEVEL 0:1.000000 1:1.000000
  NAVFREQ 0 0
  XPDR 0
  PODANGLE 0.0000 0.0000
  DOCKSTATE 0 0.0000
  AIRLOCK 0 0.0000
  GEAR 0 0.0000
  PAYLOAD MASS 0.0 0
END
END_SHIPS

BEGIN_ExtMFD
END
For the same flight time, this adds about 20-30 m/s to TLI. Notice that cir is 903m/s, or 8m/s more.

So, as far as I can tell, the offset at TLI (second scenario) procedure will be more efficient if you can't keep the MCCs of the usual procedure (first scenario) under 30- 40ish m/s, which I have not been able to do.

(just noticed that I was using realtime instead of off-axis in posted scn. I have to test to see if this makes a difference)
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Old 09-28-2012, 11:23 PM   #19
dgatsoulis
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Quote:
Originally Posted by boogabooga View Post
 Do you have Lunar Base Aurora? It's at 28.5 S, so I've used it as an example, instead of the extreme latitude Brighton Beach. Here is the relevant part of the config.

W-Aurora.cfg:
Code:
BASE-V2.0
Name = Aurora
Location = +42.46 -28.54
Size = 200
ObjectSize = 200
MapObjectsToSphere = TRUE
I don't but I added a copy of BB at those coordinates and named it Aurora.

I haven't had time to try your scenarios but the numbers seem a bit high.

Quote:
Originally Posted by boogabooga View Post
 It starts out with negative PeA.
When I tried this, I used the Base Approach for MCC just outside the lunar SOI and again within the Lunar SOI and needed something like 120m/s.
. You probably made the burn too late. Even for BB, I've never had to use more than 50 m/s.

Quote:
Originally Posted by boogabooga View Post
 My circ. velocity at lunar Pe was something like 895m/s. Sure, this is higher than if I would have stayed in plane, but from what I have observed, if you must target the base, then circ. velocity is going to increase even if you do MCC closer to the moon.
You could have saved ~90 m/s if you had arranged it so that you reached the Moon at its apoapsis. From a coplanar transfer, the circ. burn is about ~805 m/s for a 50 km alt circular orbit.

I've written a script to help me keep track of my Δv, I'm attaching it here if you want to use it. It gives you info about how much Δv you have used and how much you still have, also your fuel and how much time has passed from the start of the scenario. It's great when you want to keep track of missions and compare them.

The ship has to be a Deltaglider named GL1.
Code:
BEGIN_SHIPS
GL1:Deltaglider
In order for the Δv counter to work properly you have to set the propelant to these values:
Code:
PRPLEVEL 0:0.1366028 1:0.03000000
For the weight to be correct you also need to have no passengers.(Delete the "PSNGR 2 3 4" line from the scenario).

This sets you up with 6000 m/s of Δv, more than enough to make the transfer, LOI and landing. Unzip the file in your Orbiter directory and add the line Script Challenges/DG/Direct_landing/Challenge1 after the date between the BEGIN_ENVIRONMENT - END_ENVIRONMENT lines.

Here is an example of how the scenario should be ( I used your first scenario in your last post, deleted the irrelevant ships).

Code:
BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 51983.0639846748
  Script Challenges/DG/Direct_landing/Challenge1
END_ENVIRONMENT

BEGIN_FOCUS
  Ship GL1
END_FOCUS

BEGIN_CAMERA
  TARGET GL1
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Orbit
  REF AUTO
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL1
  ActiveProg 1 1
  DataA 1 3 0 0 0 0
  DataB 3.375 1 51983.10354121545 0 0 4.932418488553791 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare -1
  mfdProgram 2
END_MFD

BEGIN_MFD Right
  TYPE User
  MODE Interplanetary
  Scenario Old2
  MapMFD V5
  Reference Auto
  Target moon
  Center moon
  Data 0 1 1.64328122463323e-005 0 0 0 0 0 1 1 0 0
  MassLimit 1e+020
  CMode 1
  Config 1 1 1 1 800000 0
  ExtMode 2
  Periapis Moon
  END 
  CorMFD V4
  Reference Earth
  Target Moon
  Source GL1
  ActiveProg 1 1
  DataA 1 3 0 0 0 0
  DataB 3.375 1 51983.10354121545 0 0 4.932418488553791 0 51986.22222235093 0
  DVProg 0 0 0 1
  AdvConf 0 0 1 0 0
  Guidance 0
  END 
  EjectMFD V5
  Reference Auto
  Data 0 1 3 0 1 51983.05807148456 10
  Guidance 0
  END 
  BaseAprMFD V2
  Reference Auto
  Target none
  Source none
  DataA 0 0 120000 0.10821 0.366519 1 1 51983.05807148456 51983.05807148456 0
  DataB 0 3 0 1 0 1
  END 
  SlingMFD V4
  Reference Auto
  Source none
  Data 0 1 1 3 0 1 51983.05807148456 0
  END 
  LaunchMFD V4
  Target None
  Data 0 1 1 3 0 1 0
  END 
  CF1_DataA 0 1
  CF1_DataB 51982.6685767396 10 120000 2 20 150000
  CF1_SecTgt Aurora
  mfdShare 0
  mfdProgram 4
END_MFD

BEGIN_VC
END_VC

BEGIN_SHIPS
GL1:Deltaglider
  STATUS Orbiting Earth
  RPOS -3525992.11 409486.76 -5466476.98
  RVEL 6550.240 -482.699 -4262.873
  AROT 102.60 -23.32 -127.51
  VROT -0.09 0.01 0.06
  PRPLEVEL 0:0.370139 1:0.989174 2:1.000000
  NAVFREQ 94 524 84 114
  XPDR 0
END
END_SHIPS

BEGIN_ExtMFD
END
Unzip the file in your Orbiter directory and it should go in it's place.

I'll try your scenarios and compare the Δv expenditure to a couple of mine for a landing at the coordinates you provided.
Attached Files
File Type: zip Script.zip (2.6 KB, 8 views)
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Old 09-29-2012, 09:50 PM   #20
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I completed a test run so we can compare results for a coplanar transfer. As a starting point I used the first scenario you posted. The first thing I noticed was that it wasn't exactly in plane with the Moon, but a 0.17 R.Inc. wouldn't lead to too much trouble, so I kept it as it was. (I prefer my launches with < 0.05 R.Inc.)

The initial burn was 3147 m/s prograde with a tiny amount of inward (7m/s), to adjust my PeA to ~50km. Including spacecraft orientation and a slight adjustment, I ended up using 3148.44 m/s for a transfer that leads to a 6km PeA at the Moon. (Pic1 Pre-burn, pic2 post-burn).


I coasted until I was outside Earth's SOI, oriented the spacecraft in a prograde relative to the Moon direction and performed small linear RCS burns to start minimizing my R.inc relative to the base and push the node to my direction. Repeated the process at the node. (Pics 3, 4 and 5). In total, I used 29.44 m/s to get a R.inc of -0.15 to the base, with a PeA alt of ~2km


Then I setup a BaseApproach burn (orbit-insert), for a PeA of 2km. Total cost was 6.82 m/s. The LOI burn would cost 811.6 m/s (pics 6 and 7)

600 km away from the base, I had used a total of 3996.74 m/s and all I needed was a good landing. I performed a manual "tail-sitter" one, using my hover engines, with a cost of 1873.26 m/s (Pics 8 and 9)


Total Δv from scenario start to landing: 5870 m/s

So to sum up the results:
As I said in my previous posts, the offset transfer leads to a high PeA velocity that cancels any benefits of not having to perform MCCs for base alignment. In this example, even if we count the spacecraft orientation Δv, I used ~100m/s less than the 2nd scenario you posted. The real question is: Does it really matter?

Depends on how you want to fly your missions. A single burn to landing is cool if that's your goal.

Saving 100 m/s from a well tested and nicely flown mission, is mine. (Δv freak)

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Old 09-30-2012, 11:27 AM   #21
boogabooga
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I haven't tried the script yet but I did notice the discrepancy in your first photos. Your PeT is 438ks, and it appears that your entering prograde lunar orbit. I like to use transfer times of 250-270 ks into retrograde orbits, because of (almost) free return characteristics, similarity to Apollo, etc.

What I was trying to show was that the offsetting technique was at least better than not, for the same flight time, and otherwise similar flight profiles. I would imagine this will be especially true if the technique used for base alignment was as crude as the stock Map MFD, which was being suggested in the first post.

I fully acknowledge that there are better ways of minimizing total delta-v.
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Old 10-03-2012, 11:43 PM   #22
blixel
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Quote:
Originally Posted by dgatsoulis View Post
 The third way is the Belbruno-Miller transfer. Basically you make a transfer to the Moon and sling past it, to an orbit with an apoapsis almost at the edge of Earth's gravity well and a periapsis at the height of the Moon's orbit. Timing it correctly, leads to a low intercept velocity (300 to 400 m/s) instead of the traditional (800-900 m/s). So you get in a lunar orbit without a LOI burn.
The downside of this method is that the flight-time is much longer. (+60 days).
Very interesting. Is this at least somewhat similar to the method NASA used for the Grail mission? I was stunned when I first heard it took over 100 days for those probes to get to the moon.

---------- Post added at 11:43 PM ---------- Previous post was at 10:17 PM ----------

Quote:
Originally Posted by dgatsoulis View Post
 Unzip the file in your Orbiter directory and it should go in it's place.
Just a heads up... The zip file puts the script in Challenges/DG/Challenge1 but the scenario file is set to look for it in Challenges/DG/Direct_landing/Challenge1
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Old 10-03-2012, 11:55 PM   #23
dgatsoulis
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Yeah, Grail did use that transfer. It was first used on JAXA's Hiten spacecraft in the early '90s and 2 or 3 more times after that.

Have a look at this post for links with some more information.

Thanks for the heads up. The solution is simple: Either create a Direct_landing directory in the Script and place the file in there, or delete the Direct_landing/ part from the scenario.
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