Chapman Challenge

[atuhalpa]

I do understand that Piper. What is puzzling to me is, and correct me if I am wrong, the variables for the inclination change seem to be 1: The position of the flyby relative to Jupiter as referenced to the ecliptic grid; i.e. whether the probe is at 1 o'clock, 2 o'clock, 3 o'clock etc., and the distance from Jupiter. If lets say 2007 TD74 is at 35deg inc how do you dial that change in to your flyby position? I realize that I must either go north ecliptically or south ecliptically depending on which node is coming up (LAN or LDN) but what escapes me , and I have done tests using the scenario editor and editing orbital elements is what is the "formula" if there is one.

This may be the question that reveals my ignorance of the concept: Do you use the outward angle and inclination angle adjustments in the sling direct step as in a regular sling to fine tune the change?

How do you know what your final inclination change will be?

Good god I hope I am not being redundant.

 

[flytandem]

I set up the sling graphically (visually). First I finding out the time to sling and then set up the sling itself.

When to sling:
First you must be encountering Jupiter at the point in time when Jupiter is at the node with the Trojan. That can be done graphically actually. I find out the MJD of intended sling at Jupiter by first placing a surrogate ship on Jupiter surface with scenario editor. I turn autoplan off and then set up as sling direct. Target should be chosen as which ever Trojan you will want to sling to. Then with outward and inclination at zero, I add some velocity, and a white line showing the axis of intercept with the trojan appears. I advance the date of the sling and watch the hyperbola move around. It has a contact point where it is just tangent to Jupiter orbit. Don't look at the little radius dashed line, just estimate the tangent contact point. When the contact point sits appears as close as you can tell to being on the white line, you have the MJD date of the sling. You can also take it a step further and then raise the velocity of the sling to match what you estimate your encounter speed might be with Jupiter when coming from Earth with the Chapman Probe. And play around with the actual sling.... this would be the next step.

Also, using a surrogate is a great way to just play around with how the sling from Jupiter can work. You can quickly change when you sling and how fast. You can change which Trojan and what the sling angles are. What a great way to quickly understand and "see" what's happening.


Setting up the sling:
Let's say you have the TransX stage up that is the sling. It could be either the same surrogate ship on Jupiter you are playing with or the advanced stages of a flight plan from Earth, either directly or via inner planet slings. But, you have a ship that is to be slung off Jupiter to the Trojan.

Notice that you have a couple of blue orbits one being Jupiter and the other the Trojan you are targeting. Set up your graph projection as "plan" so you will always be looking normal to your ships path. Raise the sling velocity to anything from 5Km to 7Km if it's a manual sling from the surrogate, or just use "inherit velocity" of you are coming from Earth.

As you increase the inclination angle of the sling you will see the trojan change from somewhat oval to either more oval or becoming more rounded and circular. If more oval, change from adding inclination to going negative. Now as you keep changing the inclination you'll see the trojan becoming circular but also at some point your sling hyperbola (meaning you would actually escape the solar system) shows a capture of the solar system and for a bit of adjustment the blue orbits of Jupiter and Trojan are very small and impossible to see. Or just change "scale to view" to "target" and this won't be a problem. Look for the Trojan to become more rounded. When the Trojan is very circular, your ship's sling orbit will be not too far off the plane of the Trojan's. Hopefully the ships orbit will shrink to under the size of the Trojan's orbit while the Trojan orbit is showing fairly circular. This would mean that you will be on the same plane as the Trojan, at least approximately.

At this point be sure Orbits to Icept value is set to 0.5 . And you will see the location of the rendezvous with the Trojan that will be about one orbit after your Jupiter sling. Play with inclination and a bit of outward as you like, to minimize both the encounter distance to the Trojan and the encounter speed. Emphasize the encounter speed reduction. You could have a miss by 15G at the Trojan and only a couple hundred m/s MCC might fix that. So if getting the encounter that last 15G right from the sling causes a raise in the encounter speed by 500 or 1000 m/s then best to take a bit of a miss but get the soft encounter speed. It's all a bit of an art actually.

I realize that a computer program set up to really tweak the whole thing to minimize deltaV is what NASA JPL ESA et al would do. But it's amazing how close to minimums one can get just eyeballing it and never crunching a single formula. To me the beauty is in "seeing" the operation in the mind's eye and letting common sense guide you to a solution.


-----Post Added-----


FLIGHT REPORT
Destination 2002 GE39
Depart Earth MJD56949.8 Pro=10.0Km, Out=601.4m/s, Pl.Ch.=-1.575Km/s.
Jupiter MJD57532 sling angles Out= -7.2 deg, Inc=-121.1 deg.
Arrive "2002 GE39" MJD 61263 Encounter Vel=947m/s

The challenge was that the initial transfer burn used up all the fuel in the stages and it was necessary to quickly jettison the last stage, transfer focus to the Frigate and to set up the remaining part of the transfer burn before getting too far from Earth and out of the gravity well.

The sling is straightforward and arrives very slowly at the Trojan Asteroid. Remaining deltaV in the Frigate was 1862 m/s and Chapman Probe fuel still 100%.

screenshot then code of final orbit below.

BEGIN_DESC
In orbit around "2002 GE39".
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 61263.3573118669
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Fregat1
END_FOCUS

BEGIN_CAMERA
  TARGET Fregat1
  MODE Cockpit
  FOV 10.00
END_CAMERA

BEGIN_HUD
  TYPE Orbit
  REF AUTO
END_HUD


BEGIN_SHIPS
Delta4HV:Delta4HVD4HV
  STATUS Orbiting Sun
  RPOS -323615343935.46 10818045210.11 -482828573542.91
  RVEL 13670.672 -186.186 3739.090
  AROT 3.00 3.59 -72.01
  NAVFREQ 0 0
  CONFIGURATION 2
  PAF 3
  MET 372723263.2
  HEIGHT 25.0
  UPGRADE 
END
Delta4HV-SRB2L:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS 25.3303833 4.5850280
  HEADING 313.68
  NAVFREQ 0 0
END
Delta4HV-SRB2R:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS 25.3343595 4.5868365
  HEADING 165.32
  NAVFREQ 0 0
END
Delta4HV-SRB1L:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS 25.3387973 4.5738527
  HEADING 296.78
  NAVFREQ 0 0
END
Delta4HV-SRB1R:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS 25.3420295 4.5782731
  HEADING 305.34
  NAVFREQ 0 0
END
Delta4HV-LHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS 30.1210866 0.7617813
  HEADING 57.40
  NAVFREQ 0 0
END
Delta4HV-RHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS 30.2878093 1.0071703
  HEADING 276.79
  NAVFREQ 0 0
END
Delta4HV-STG1:Delta4HVD4HVcore
  STATUS Landed Earth
  POS 83.3479516 -25.7850329
  HEADING 277.51
  NAVFREQ 0 0
END
Delta4HV-LHF:Delta4HVD4HVfair3
  STATUS Landed Earth
  POS 93.3346940 -28.2122024
  HEADING 101.26
  NAVFREQ 0 0
END
Delta4HV-RHF:Delta4HVD4HVfair3
  STATUS Landed Earth
  POS 88.4465484 -27.1225726
  HEADING 330.66
  NAVFREQ 0 0
END
Fregat1:cvelfregat
  STATUS Orbiting 2002 GE39
  RPOS 11503.45 -3602.81 -94.26
  RVEL -1.884 -6.006 -0.497
  AROT 85.77 22.39 -179.28
  PRPLEVEL 0:0.357
  NAVFREQ 0 0
  XPDR 0
  PAYLOAD ChapmanOuter ChapmanOuter SpacecraftChapmanOuter 0.00 -0.15 2.00 1365.00 0.00 1.00
END
END_SHIPS

BEGIN_ExtMFD
END

 

[atuhalpa]

I can get the surrogate on jupiter , and I can turn autoplan off, but I am lost as to how to get to sling direct without going through the other "normal" stages of transx. I sure wish there was a flow diagram for transx, you know like little boxes with arrows to other boxes for the different stage that show how to navigate through the different stages. I'll keep trying to muddle through your post as I do appreciate the time you have taken to explain things.

I am really lost. I went back and tried to follow what you said to do in the post but I just got more confused. I need something like an ultra detailed directions list and I don't really expect anybody to take the time for that. I'll just have to get it by total immersion and figure it out myself.

 

[flytandem]

OK. On Jupiter. TransX up.

click VW to get "Setup"
click "-" (as needed) to toggle to Escape.
click FWD.
Now you have the next stage where you are leaving Jupiter.

In setup view (you should still be there, if not click VW as needed).
click VAR to get Autoplan, then click the "+" to turn it off.
click VAR to get Plan and the plan is probably "eject". Click "+" to show "sling direct".
click VAR to get Graph Projection and then click "+" as needed for "Plan".

click VW to get sling direct view.
click VAR to get Velocity, then "+" to add how much you want. 6K?
click VAR to get Inherit Velocity, then click the "+" to make it "No".
click VAR to get Date and then change date with "+" or "-"

VAR will also toggle your sling angles Outward and Inclination. Leave Inclination at zero if you are looking to find where your node is with your target and advancing date to the node. Then once there you can start playing with the two angles and the velocity.

Remember that if you are looking for an intercept with your target after a full orbit then in Setup, the VAR Orbits to Icept needs to be set to 0.5 .

cheers,
rob

 

[atuhalpa]

Thanks flytandem!

Thanks so much. The concise instructions in your last post are enough to kickstart my brain. I spend so much time here on orbiter sometimes I get mental blocks. I am going to take the time to analyze transx and do a diagramed flow chart. It will help me to navigate through the different stages in a more informed manner.

 

[flytandem]

I just tried a different approach to a Trojan. Well same overall trajectory to get there but arriving at 2008 RL32 I decided to use the Fregat as an impactor. I was encountering at about 1406 m/s. I lined up for a glancing hit on the sunny side of the rock. 15 minutes before impact I jettisoned the Fregat and did a small lateral burn to arrive with the Chapman Probe about 500 meters above the surface above the impact site.

I did 2 runs at it. The first had me doing a braking burn to put the Chapman in orbit while the impactor impacts the rock behind me during the burn. The second was no braking burn but to just slow a couple m/s for the last 3 minutes, so I would get a good view of the hit. It was interesting to see a good zoom of the impactor probably 1 to 1.5 Km away and the rock comes across the screen, and suddenly the impactor goes tumbling off the screen. I recorded both runs. Too bad cratermaking and debris isn't sim'ed.


-----Post Added-----


Here's the impact scenario from the flight described above. Copy, paste and enjoy. Try on normal speed then in slow motion warp 0.1 .

BEGIN_DESC
Fregat1 impacts "2008 RL32" with Chapman probe in position to 

watch and nearly gets hit by the rebounding Frigat1. 
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 61699.1266935439
END_ENVIRONMENT

BEGIN_FOCUS
  Ship ChapmanOuter
END_FOCUS

BEGIN_CAMERA
  TARGET ChapmanOuter
  MODE Cockpit
  FOV 30.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD

BEGIN_MFD Left
  TYPE Orbit
  PROJ Ship
  FRAME Ecliptic
  ALT
  REF 2008 RL32
  TARGET Fregat1
END_MFD

BEGIN_MFD Right
  TYPE Surface
  SPDMODE 1
END_MFD


BEGIN_SHIPS
Delta4HV:Delta4HVD4HV
  STATUS Orbiting Sun
  RPOS -613975648602.33 14204700253.62 18031556376.47
  RVEL -1443.362 -477.414 -8995.128
  AROT 17.58 -34.65 -8.94
  NAVFREQ 0 0
  CONFIGURATION 2
  PAF 3
  MET 442354363.1
  HEIGHT 25.0
  UPGRADE 
END
Fregat1:cvelfregat
  STATUS Orbiting Sun
  RPOS -632773603786.68 -268301658676.03 -421700033750.21
  RVEL 8145.307 -3679.149 -7831.474
  AROT 65.05 -10.15 29.37
  PRPLEVEL 0:0.280
  NAVFREQ 0 0
  XPDR 0
END
ChapmanOuter:SpacecraftChapmanOuter
  STATUS Orbiting Sun
  RPOS -632773602403.00 -268301660654.12 -421700033633.86
  RVEL 8147.039 -3680.207 -7830.832
  AROT 103.54 44.53 42.61
  PRPLEVEL 0:0.988
  NAVFREQ 0 0
  RCS 1
  CTRL_SURFACE 1
  CONFIGURATION 1
  CURRENT_PAYLOAD 0
  SEQ 0 -2 0.000000
END
END_SHIPS

BEGIN_ExtMFD
END

-----Post Added-----


Another option for hitting a Trojan.
Name: 2007 TD74
Depart Earth MJD 55402.6555
Pro= 9.359 Km/s
Out= 0
Pl.Ch.=737 m/s
Target encounter date at Jupiter= MJD 75120 and sling to the asteroid is, Out=0, Inc= -114 degrees.

This actually launches before the challenge start date of Jan 2011 I'll bet a similar plan can be done one Jupiter orbit (~12 years?) later.

It's a type 2 orbit to Jupiter in that it passes the Ap and is dropping back toward the Pe when it encounters Jupiter. The target encounter speed was 7400 m/s as this would be perfect for the sling to the Trojan, but this transfer to Jupiter came close with something like 7800 m/s encounter speed. The arrival at the Trojan is very soft at about 900 m/s and is less than 2 degrees off alignment with the Trojan. It had the smallest dv requirement enroute of any of the asteroids I ran so far but had a fairly healthy transfer burn from Earth. Luckily even with the Fregat on board the upper stage was not used up completely but still had 1% fuel remaining and completion of the transfer burn.


-----Post Added-----


Just can't get enough of working the setup and doing the flight for these Trojans so here's another one I just flew.
Trojan: 1998 WW37
The concept this time is to start by finding precisely when and how fast to encounter Jupiter and also what sling angle. Then do the best transfer from Earth with emphasis first on arrival date and also but lesser on being within reason of the specified encounter speed. The speed difference would be made up with a burn at the Pe of Jupiter to make it exactly like the initial setup asks. It turned out to be the best way yet with very little DV used.

Here's the initial setup requirement.
Sling Jupiter on MJD 58230. Encounter speed 6400 m/s. Sling outward=0 inclination= 111.14 degrees. Encounter at 1998 WW37 is predicted to be 823 m/s.

In looking for a window to depart Earth I played around and though not perfect I found the following Earth departure data.
Date: MJD 57350.0117
Prograde: 8.607 Km/s
Outward: 2.249 Km/s
Plane.Ch.: -4.070 Km/s

On the way to Jupiter focus on doing MCC to get the arrival date as close as possible to 58230. You'll notice the encounter speed is a bit light by 350 m/s, but because the sling will be set up manually (inherit velocity off, vel=6400, and date manually set to match your actual arrival date) TransX tells you how much prograde dv to add and when to add it, which will be at the Pe. Because it was in the gravity well there was a bit of savings and my burn asked for only 280 m/s.

After that the full orbit to catch the Trojan was about 0.5 degrees offplane which is very close. Minimal corrections were needed as compared to all previous Trojan chases I've done and the arrival speed at 1998 WW37 was actually only 817 m/s as compared to the predicted 823. Amazing how close actually.

I lined up to hit the Trojan dead center and separated from the Fregat while 5000 Km from the rock. The Fregat continued as an impactor and the Chapman Probe was then offset to arrive 1Km agl and subsequently braked into orbit. Because the Fregat was a direct hit within a meter or two of center, it just hit and stuck like wet spagetti to the wall. At least the way I cook it. :rofl:

BEGIN_DESC
1998 WW37. Fregat on the ground looking up at the Chapman Probe passing overhead.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 61638.1165163182
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Fregat1
END_FOCUS

BEGIN_CAMERA
  TARGET Fregat1
  MODE Cockpit
  FOV 20.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD

BEGIN_MFD Left
  TYPE Orbit
  PROJ Target
  FRAME Ecliptic
  ALT
  REF 1998 WW37
  TARGET ChapmanOuter
END_MFD

BEGIN_MFD Right
  TYPE Map
  REF 1998 WW37
  OTARGET ChapmanOuter
  TRACK ON
END_MFD


BEGIN_SHIPS
Delta4HV:Delta4HVD4HV
  STATUS Orbiting Sun
  RPOS -416482636105.69 25289584985.12 -22633857005.65
  RVEL -11555.652 199.638 -14662.383
  AROT 13.09 28.56 136.35
  NAVFREQ 0 0
  CONFIGURATION 2
  PAF 3
  MET 370521534.7
  HEIGHT 25.0
  UPGRADE 
END
Fregat1:cvelfregat
  STATUS Landed 1998 WW37
  POS 12.7514809 48.5752705
  HEADING 34.12
  RCSMODE 2
  PRPLEVEL 0:0.671
  NAVFREQ 0 0
  XPDR 0
END
ChapmanOuter:SpacecraftChapmanOuter
  STATUS Orbiting 1998 WW37
  RPOS 2333.60 -1083.99 -2820.94
  RVEL 1.296 -0.496 1.274
  AROT -158.26 -39.21 -163.22
  VROT 0.00 0.00 -46.43
  PRPLEVEL 0:0.635
  NAVFREQ 0 0
  RCS 1
  CTRL_SURFACE 1
  CONFIGURATION 1
  CURRENT_PAYLOAD 0
  SEQ 0 -2 0.000000
END
END_SHIPS

BEGIN_ExtMFD
END

 

[atuhalpa]

What should I do to learn what you know about transx and slings? I am obsessed with learning how to tag that perfect inclination change/ orbit circularization. I suppose I just work through all your sling tutorials and do a bunch of my own til I can do them in my sleep. I was pondering some method of recording a session of you doing a trojan sling with something like the video capture MFD with a voice over, but I doubt that is going to happen. Just how long have you been tinkering with transx? It seems like you know it better than anyone else in the forum. You have probably forgot more about transx than I'll ever know.....................(sigh)


-----Post Added-----


Wow! You should do a tutorial "Fun with the Fregat". I just ran your Fregat impact scenario and when the Fregat bounced off of 2008 RL32 and narrowly misses the Chapman I damn near fell on the floor laughing.
You are truly astounding with your transx mastery..

 

[flytandem]

Here is a great exercise in learning the sling from Jupiter to a Trojan. I have played around with using a surrogate on Jupiter and have learned that it takes about 5 minutes to nail a very precise sling date, velocity, and outward&inclination angles. I went through a dozen or more Trojans gathering the data in about an hour. But I will present one Trojan's data. And I then have the first part of the flight (the transfer from Earth to Jupiter) completed and the scenario provided below starts just before TransX switches to the Jupiter encounter. You will run the scenario and manually enter all the data for the sling. Then just run the scenario at warp 100,000 and after 30 minutes you will need to do your own decisions on MCCs to hit the Trojan.

Sling data I found for Trojan "2008 GC1"
Sling date= MJD 58607.1059
Encounter (sling) velocity= 7.702 Km/s
Outward sling angle= 13.9862 deg
Inclination angle= -113.8116 deg

In setting this scenario up for you I had to then find a way to leave Earth to arrive as close as possible to that date and with something not hugely off in the encounter velocity. I found one but didn't spend a lot of time so perhaps you can do better but, and just FYI, to get to the point of the scenario below I left Earth with the following details in TransX.
Earth departure date= MJD 56981.5372
Prograde Vel= 9.099 Km/s
Outward Vel= 26 m/s
Plane Change= 469 m/s
From low Earth orbit the actual dv needed was about 6600 m/s as I recall. There was about 280 m/s left in that delta4 heavy or whatever that upper stage is called that you supplied my on the disc. There was some moderate mid course correction on the way especially in trying to get to Jupiter exactly at the right time.

Now when I flew the transfer from Earth to Jupiter, I did manage to get the Pe almost perfect in placement for the sling and only 4 minutes ahead of the required sling date (pretty anal I know, I used to happy being within 3 weeks of hitting Jupiter, heck even hitting Jupiter at all), but because the actual encounter velocity is somewhat less than the required sling speed there is a burn coming up you need to do at the Pe of Jupiter. This Pe burn was known as part of the transfer and planning. But the burn turns out to be about only about 380 m/s or so which is pretty small considering there isn't a lot left to have to do before hitting the Trojan and the arrival speed at the Trojan is something like 800 or 900 m/s depending on how your corrections go in the final orbit to the Trojan.

INSTRUCTIONS ON RUNNING THE SCENARIO
Bring up TransX in both MFDs.
In Setup View, Target Jupiter.
Forward.
In Setup, Escape.
Forward. (you are now planning your trip away from Jupiter)

In Setup View:
Target "2008 GC1"
Autoplan= Off
Plan= Sling Direct
Graph Projection= Plan
Scale to View=Target

In Sling Direct View:
Velocity= 7.702 Km/s
Outward= 13.9862
Inclination= -113.8116
Inherit Velocity= No
Eject Date= 58607.1059

Go back to Setup and for the Variable "Orbits to Icept", toggle it up to 0.5

Now you have your sling perfectly entered and go Back to Stage 2, View: Sling Direct. You will see a green radius line overlying a yellow dashed line. You will also see the required deltaV needed at the Pe of Jupiter. It's something around 380 m/s as I recall. Warp ahead carefully to close to the Pe. It's normal for TransX to initially give data showing your sling isnot perfectly aligned when it first switches stages. As you get closer to the Pe it slides back into place. As you approach the Pe turn "prograde" using the autopilot (or manually with the HUD) and when the time to start burn hits zero, apply full thrust and turn it off when it the deltaV hits zero. It's a bit like the maneuver burn in TransX except there is not target, it assumes you know to point prograde. You'll notice the information of your required deltaV disappears as you get to zero velosity. At this point the position of the sling, and now the speed is perfect.

Then coast for 30 minutes at warp 100K to go half an orbit around to the Trojan, and then decide what correction(s) to do for the remainder of the journey. There should be plenty of fuel without even having to dip into the Chapman probe. Even though the initial setup had a near perfect hit at the Trojan, it's likely you will burn a couple hundred or more m/s with your corrections. But given you still have well over 3K m/s in the can you are easily able to afford it.

The scenario:

BEGIN_DESC
Tutorial for the sling to 2008 GC1.
END_DESC

BEGIN_ENVIRONMENT
  System Sol
  Date MJD 58530.1894677777
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Fregat1
END_FOCUS

BEGIN_CAMERA
  TARGET Fregat1
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD


BEGIN_SHIPS
Delta4HV:Delta4HVD4HV
  STATUS Orbiting Sun
  RPOS -246554627295.31 3063425609.75 -790287615968.91
  RVEL 7651.025 102.341 2000.941
  AROT -13.42 34.74 100.09
  PRPLEVEL 2:0.019
  NAVFREQ 0 0
  CONFIGURATION 2
  PAF 3
  MET 133839621.9
  HEIGHT 25.0
  UPGRADE 
END
Delta4HV-SRB2L:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS -6.7137754 5.0893956
  HEADING 64.90
  NAVFREQ 0 0
END
Delta4HV-SRB2R:Delta4HVD4HVsrb2
  STATUS Landed Earth
  POS -6.7150821 5.0930395
  HEADING 77.77
  NAVFREQ 0 0
END
Delta4HV-SRB1L:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS -6.7030468 5.0913471
  HEADING 254.60
  NAVFREQ 0 0
END
Delta4HV-SRB1R:Delta4HVD4HVsrb1
  STATUS Landed Earth
  POS -6.7119203 5.0937039
  HEADING 262.29
  NAVFREQ 0 0
END
Delta4HV-LHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS -0.7002220 6.1726719
  HEADING 99.85
  NAVFREQ 0 0
END
Delta4HV-RHB:Delta4HVD4HVboo
  STATUS Landed Earth
  POS -0.6581705 5.9129964
  HEADING 266.59
  NAVFREQ 0 0
END
Delta4HV-STG1:Delta4HVD4HVcore
  STATUS Orbiting Sun
  RPOS -8085070432028.80 -25966818183398.80 79987609394062.33
  RVEL -60992.480 -194013.497 596708.132
  AROT -136.55 -11.47 -80.65
  VROT -15300.38 9481.47 0.00
  NAVFREQ 0 0
END
Delta4HV-LHF:Delta4HVD4HVfair3
  STATUS Orbiting Sun
  RPOS -77222346727161.41 -47427411261985.98 173507503276944.19
  RVEL -577562.769 -354361.655 1295463.849
  AROT 132.09 19.72 38.23
  VROT 10.46 -0.04 -1.18
  NAVFREQ 0 0
END
Delta4HV-RHF:Delta4HVD4HVfair3
  STATUS Orbiting Sun
  RPOS -10557904928478.86 -1832499780452.92 9588008236874.15
  RVEL -79260.091 -13649.193 70435.546
  AROT 101.42 -35.48 52.98
  VROT 3.82 -1.45 0.49
  NAVFREQ 0 0
END
Fregat1:cvelfregat
  STATUS Orbiting Sun
  RPOS -239048584059.80 3165991530.71 -791298208921.90
  RVEL 7684.273 98.220 1975.071
  AROT -0.67 -30.37 101.17
  RCSMODE 2
  PRPLEVEL 0:0.924
  NAVFREQ 0 0
  XPDR 0
  PAYLOAD ChapmanOuter ChapmanOuter SpacecraftChapmanOuter 0.00 -0.15 2.00 1365.00 0.00 1.00
END
END_SHIPS

BEGIN_ExtMFD
END

Final Note.
The goal here is to see that with a desired sling at Jupiter, you must first make a transfer from Earth to Jupiter that ends up arriving at Jupiter like the scenario provided here, arrive at the right place and time. Then do the Pe burn if inherit velocity is "no" where you set the sling speed. Or no Pe burn if inherit velocity is "yes". Either way... you're on your way.

Finding the necessary data for a particular Trojan is actually simple using a surrogate on Jupiter but that's another tutorial.... hint... it's all about watching the axis line (that white line). Adjust sling date to get the node lined up with the sling, adjust the velocity to make the white line swing 90 degrees across from the sling location, and adjust the inclination angle to get a 1 orbit to make a rendezvous, and repeat these three a few times to get precise data.

 

[atuhalpa]

Eureka! I have found it!

Finally, the light goes on. I don't know it all yet but I have finally conceptualized the sling inclination change, the use of the "plan" graph, and the usage of the "orbits to Icept" and the back and forth and back and forth adjusting all the green lines and yellow dashed lines to coincide to place that package where you want it to go. I still need tons of practical to really drive it home and make it less tedious, but thanks to your persistence and detailed posts flytandem, I have decalcified a small section of my brain and made a breakthough to another level of understanding Orbiter, the most wonderful piece of freeware in the Orion arm of the Milky Way Galaxy. Once again, thank you for sharing your hard earned knowledge with me.

I Owe you a beer

 

[flytandem]

That's great atuhalpa!

Doing slings with TransX is considered by most Orbiters as quite advanced maneuvering. But with some practice it's actually really easy. And it soon becomes an art form because TransX has a tendency to wander slightly in its predictions of where you are going so there is a constant need for course corrections. But in most cases, the most accurate that it gets to predicting how your position in the sling will be is just before it switches to the sling being stage 1. That's why I gave the scenario as that moment.

And most Orbiters I think have traditionally done the sling as always completely free coasting and not played around with setting it up with a different velocity than what you have. Afterall to use a different velocity means having to blow fuel and somewhat defeats the point of using slings. But in effect if a burn has to be done somewhere along a long flightplan, then doing it in the gravity well makes a lot of efficiency sense so why not plan it into the sling.

When I saw the need to find slings off Jupiter to a large number of nearby targets, it just made sense to manually choose the date and speed of sling to see what one would need. Then do the work of finding a transfer from Earth that matches it.

But does one first have to manually choose the dates of the nodes, and then set up Earth Jupiter transfers to then find out how the sling will play out? No, planting a surrogate on Jupiter is a simple and fast way to gather data on all the Trojans. Nodal date, ideal sling velocities, and the 2 sling angles for a perfect rendezvous. It even shows the arrival dv needed at the Trojan.

Using a sling for a ship sitting on Jupiter is almost exactly like doing a normal eject plan from Jupiter just like you would for a ship leaving Earth for Mars for example. It's just that in the eject plan, you are given the 4 variables to play with as date, pro velocity, out velocity, and pl.ch. velocity (start date and 3 dimensions of speed). When doing it with a "sling" plan it gives the variables as date, velocity, outward angle, and inclination angle (start date, departure speed, and 2 angles). It's like doing it in polar coordinates instead of cartesian. If you wanted the overall departure speed to be part of the decision and if you will be using the information for a future ship that will be passing by to mimick the sling plan then "sling" with a surrogate sitting on Jupiter is a fast and easy way to collect all the data one needs.

BTW, there is so much fuel saved on average, after a trip to orbiting 2008 GC1, I ejected to meet and orbit a second Trojan, 1996 RJ. And Right now I am heading off from 1996 RJ to orbit a 3rd Trojan, 1986 TT6. Not bad for one ship/mission from Earth. But this will be the final resting place of the Chapman as it will be in orbit with just 200 or 300 m/s of fuel remaining. edit: in orbit at 1986 TT6 with 465 m/s remaining. not enough to go any further.

 

[atuhalpa]

Using a surrogate for planning is my next goal in this series.

By the way, how does using the D4HV as opposed to the Delta Glider stack up, that is pros, cons and general flight operations?

 

[flytandem]

Using a surrogate for planning is my next goal in this series.

By the way, how does using the D4HV as opposed to the Delta Glider stack up, that is pros, cons and general flight operations?

I assume you mean the stack of rockets you have in the scenarios to get the Chapman and Fregat up into LEO and boosted to an interplanetary transfer.

In some ways the rocket is easier and some ways harder. The rocket only does one basic change of pitch gradually lowering from vertical to horizontal while the deltaglider must first pitch up then then at some point pitch back down. The rocket is simpler from the point of view that yawing is just that, yawing which is to get the relative inclination correct, while in the deltaglider you must do a combination of rolling and a bit of pitch mixed in to get a change in relative inclination. Although once out of the atmosphere the deltaglider then can just yaw like the rock.

But the rocket is tougher in my opinion at the start. Being pointed straight up I have no idea what direction the roll attitude is so it's a challenge to decide how much a mix of pitch and yaw to do in the first 10 seconds to get started on the correct heading. And the roll response of the rocket is very sluggish so if one wants to have either a heads on the top or on the bottom of the craft rolling and stopping the roll takes care and patience. I seem to be about 80% success rate in getting the rocket to orbit and I know if I have blown it usually in the first 30 seconds and just restart. If I make it past 30 seconds I can get it into orbit.

An interesting challenge is if there happens to be not enough dv in the upper stage to do the entire transfer burn and there is the need to dip into the Fregat. It means that with perhaps a couple hundred m/s dv still to do, I have to jettison, switch vehicles, and create an entire TransX plan before the craft has slowed too far in speed. It would be nice if TransX had the ability to just download the plan from the other ship instantly so I could take just a few seconds to continue with the burn. Maybe TransX can get the plan but I haven't spent much time checking how.

Once on the way, the Fregat, or Chapman or Deltaglider are to me all the same. Navigate, turn and burn. I hardly ever use anything but the glass cockpit showing just the MFDs.

 

[T.Neo]

Is carrying a fregat all the way to Jupiter orbit realistic? Wouldn't the propellant burn off, or the batteries die?

 

[flytandem]

Is carrying a fregat all the way to Jupiter orbit realistic? Wouldn't the propellant burn off, or the batteries die?

I have no idea what realistic is as far as a stack of simulated rocket ships. The only thing I have is the CD sent over and the selection of asteroids it had. But even if the Chapman were on its own, I assume then it would make many of the climbs to orbit and transfers easier because it wouldn't be needing to carry the Fregat's mass. And the Chapman with over 2900 m/s dv, would work just fine for most if not all of the solutions and still have plenty of fuel left over. One wouldn't be doing 3 asteroids in 1 mission though. Maybe 2 rocks? The trip to "2008 GC1" and then to "1996 RJ" had a really small encounter speed of something like 850 m/s to the first rock 150 m/s to the second so that might be a way to get 2 for 1 using just Chapman.

 

[atuhalpa]

Fly, In the scenario file there is an entry under BEGIN_SHIPS for the D4HV, "HEADING" that you can set for azimuth and that translates to a forward push on a joystick(if one was connected) to pitching to that azimuth heading. I think it is in a "notes" file to you in the orbiter folder or the scenario folder. I use it by setting up transx, saving, fast forwarding to t-0 and noting azimuth heading, then entering the value in the HEADING parameter. When you restart the scenario all you have to do is push forward on the stick and you pitch to the correct azimuth, comprende?

I did some research on the fregat. I was used on the Russian Fobos missions as an orbital brake so it's operational life time is at least as long as a Mars mission. The data sheet claimed it could be restarted at the least 20 times. So it probably isn't too far fetched to take it to a Trojan.

 

[flytandem]

Fly, In the scenario file there is an entry under BEGIN_SHIPS for the D4HV, "HEADING" that you can set for azimuth and that translates to a forward push on a joystick(if one was connected) to pitching to that azimuth heading. I think it is in a "notes" file to you in the orbiter folder or the scenario folder. I use it by setting up transx, saving, fast forwarding to t-0 and noting azimuth heading, then entering the value in the HEADING parameter. When you restart the scenario all you have to do is push forward on the stick and you pitch to the correct azimuth, comprende?

Thanks!. Well that would surely take out the drunken wanderings of my first 30 seconds on each flight.
Hey I also noticed that on startup, the heading isn't being shown in TransX stage 1 but rather a relative inclination much like it was already flying. But if I touch "T" once to get warp 10, there is a screeching sound like tires on the ground and TransX shows the heading. It behaves like the craft is in the air floating and needs warp 10 for a short burst to get it onto the ground. It can be returned to warp 1 (real time) then and the heading info stays until I launch.


-----Post Added-----


Ooops forgot to mention. Others may have already talked about this so pardon if it's redundant.
When reopening scenario saves it often causes CTD. I think it has to do with TransX not being able to see file names that have a space in them. Example "2008 GC1". It would probably be able to open it if it were called "2008-GC1". Not sure though. I've thought about renaming all the configuration files and I guess the sol file would have to be edited to change all the asteroid names. But I really have little ability and would probably just screw it all up. I would probably make my Chapman Orbiter folder unusable and have to reload it from the CD. I know I can edit the scenarios by first deleting all the TransX info and it opens fine. Then I must set up the TransX flightplan info after opening each save.

 

[flytandem]

A couple more flight reports. Flights to "2002 FR4" and a flight to "2002 CM208".

FLIGHT REPORT "2002 FR4"
Perhaps the toughest Trojan for me so far. Definitely not recommended as a first attempt at a Trojan. Had trouble getting a low velocity eject from Earth. I had to dip about 600 m/s into the Fregat just to complete the TJI burn. The plan called for a gravity well burn of about 600 m/s at the Pe of Jupiter and the encounter velocity at the trojan was about 1400 m/s. All added up it took every last drop of the Fregat to get into orbit at the trojan and actually I was about 10 m/s short and had to detach the Chapman for that last 10 m/s. It left the Fregat out of fuel and slowing walking away from the asteroid.
Here are the departure and sling data.
Depart Earth:
MJD 56934.2502
Pro= 8.331 Km/s
Out= -3.704 Km/s
PlCh= 5.883 Km/s
Arrive Jupiter MJD 57891.1759
Set manual sling Vel=6631 m/s
sling angle Out= -5.6 degrees
sling angle Inc= +112.82 degrees



FLIGHT REPORT: "2002 CM208"
Was actually very easy. Could be a good candidate for a first try at a Trojan. I was a bit sloppy on the climb to orbit ending up with a high 240km agl parking orbit. I ended up needing about 90 m/s of the Fregat to complete the TJI burn. But the gravity well burn at Jupiter was a light 160 m/s (retrograde) and the encounter speed at the trojan was also very light being about 650 m/s. It had the craft in orbit around the trojan with still about 2400 m/s in the Fregat and the Chapman still attached and full.
Depart Earth MJD 55786.3133
Pro= 9.177 Km/s
Out= -154.7 m/s
PlCh= 1.902 Km/s
Arrive Jupiter MJD 57293.8259
Manual sling Vel= 6588 m/s
sling Out angle= +5.3 degrees
sling Inc angle= -110.00 degrees

It's interesting having to complete a TJI burn with the Fregat. What I did was, when the upper stage of Delta4 runs out, I make sure that the direction is correct and killrot. Write down how much dv is left in the TransX burn. Also look at the ClApp at Jupiter as an extra bit of info. Then jettison and switch into the Fregat and killrot to be sure the direction is still good. Bring up Transx and escape,target Jupiter. Bring up Burntimecalc and look at the total dv and subtract the missing dv to get what should be left after doing the remaining part of the burn. Then start burning watching the remaining dv drop toward the proper fuel level and also to watch the Cj App in TransX. They usually both hit their target value and if needed I err on the side of getting the ClApp in TransX correct. Then enter all the data for the entire trip and plan on doing a proper MCC in the next 5 minutes to make sure the TJI is clean.

 

[Piper]

The latest version of the Chapman probes (v3.0) is out, and I'll have the next Chapman Challenge up tomorrow. Great job people! flytandem, those transX plans are amazing! Especially that last one, it by far beats my most efficient Trojan trajectory (about 940m/s).

 

[flytandem]

Thought I'd toss out one more Trojan flight.
"2002 EK127"
Depart Earth MJD 56167.3337
Pro= 8.909 Km/s
Out= -1.508 Km/s
PlCh=3.503 Km/s
Encounter Jupiter 57491.3759
Set up a manual sling with the above encounter date and,
Vel = 6591 m/s
Out Angle= 0
Inc Angle= 114.1452
Encounter Vel with 2002 EK127 = 1290.

Notes: Fairly straightforward with using about all the Delta4 fuel but not needing any of the Fregat fuel to complete the TJI. The gravity well burn at Jupiter was a prograde 270 m/s burn. Total with all MCC was about 2000 m/s. DV left in Fregat about 1700 m/s, Chapman still full.


-----Post Added-----


Flight report:
"1999 XJ55"
Depart Earth 56601.6501
Pro= 9.271 Km/s
Out= 0
PlCh=1.564 Km/s

Arrive Jupiter 58484.0
Sling inherit velocity=Yes
Out angle=0
Inclination angle=110.746

Encounter Vel at 1999XJ55 =~ 750 m/s

An easy climb to orbit and there was plenty of fuel in the Delta4 heavy with about 270 m/s spare dv. Some wasted MCC and blew a lot more than I should both getting to Jupiter in the slot and to rendezvous with the Trojan. In orbit at 1999 XJ55 there was 2182 m/s dv remaining in the Fregat and Chapman still full. Approx 1550 m/s used for all MCC and rendezvous after the TJI. Somewhat sloppy.

 

[atuhalpa]

Has having the option of setting the initial azimuth allowed you to complete the TJI's of these subsequent missions with the EDS ( earth departure stage) dV? That is if you hadn't got sloppy, as you stated in an earlier post?

Also Fly, if you want to tinker with the new Chapman probes, including the ion drive Chapmans, you will need to add some files to the spacecraft folder in the config folder, add some scenario templates to the chapman probe scenario folder and change the masses in the scenario folders. The modifications are required because of the nature of the CVEL launch vehicles. Of course you must also download and install the updated Chapman package from Orbiter hangar mods. If you want I can get the config and scenario mod package together and email it to you as it won't be very large.

I almost forgot. You need the IEATMFD to control the ion drive probes. There is a post by piper and another by myself that has the link to the download. If you search the forum for IEATMFD you will find it. I found it.

http://myweb.tiscali.co.uk/briansuti...te/ieatmfd.zip