Advanced Question Wo2001 Station V to Venus

[Lupin_Yonder]

Hi there
I'm trying out the World of 2001 scn of station V to Venus.
I'm finding that the station is a bad place to launch from as its orbital inc is 57.25inc 233.53Lan and Venus is 9.58inc Lan 349.97.

Now plane changes are very fuel costly as I have discovered but I'd rather not use the scenario editor to change my inc, but do it within the constraints of the scenario.

I keep reading that changing your inc is much cheeper in fuel if done at a low velocity at the apogee but even if I extend my apogee out to ApR 9m my inc rate change is only 0.12 deg/sec.

I have tried creating a transX plan with a large plane change and I was under the impression that if done, I would not need to change my orbital inc as this would be incorperated into my transx ejection burn. To be honest at this point I get confused by the Ejection orientation variable in the escape plan stage, changeing this seems to lower my Rinc to about 20deg but I can't get it lower than that. This variable is allways a bit of a mystery to me.

I have however completed the excellent fly tandem tutorial of Mars surface to Venus but this scenario accounts for the inclination in the take off.

P.S. Sorry for long post but I wanted to make myself clear.

 

[Urwumpe]

Simple: Don't do a plane alignment for interplanetary flights. That is the most stupid thing you can do, especially since the planets are orbiting the sun in different planes than Earth.

 

[Ark]

I just use IMFD, it handles off-plane interceptions pretty well.

 

[Lupin_Yonder]

OK fine, no plane alinement's needed, great!
But I could still use some help.
So I have a good TransX plan for Venus, I have set my Periphrasis distance but I still am unsure of how to use the Ej Orientation variable. I kind of understand the process used in the fly tandem Mars to Venus tutorial but as I'm not launching from the surface I don't know what I should be doing/looking for with this Variable.

P.S. Thanks for calling some one asking a question stupid.

 

[Urwumpe]

P.S. Thanks for calling some one asking a question stupid.

No problem.

I still say that a plane alignment for interplanetary transfers is the most stupid thing you can do. you can of course decide to prove me wrong and find something more stupid.

 

[Lupin_Yonder]

I'm fine with it being stupid but I obviously didn't know that, being a little new to the sim, I don't need to prove myself right or you wrong. I just thought you put it a little bluntly considering I was just looking for some help.
But anyway, lets not get off topic, I'm still confused

 

[Urwumpe]

Well, I don't work with TransX, though I know it can also handle such transfers.

Do you know what "patched conics" mean? This is the approximation in trajectory planning, that is used for such missions.

http://ccar.colorado.edu/~nerem/zipfiles/cloutier/patchedconics.html

 

[dgatsoulis]

Hi there
I'm trying out the World of 2001 scn of station V to Venus.
I'm finding that the station is a bad place to launch from as its orbital inc is 57.25inc 233.53Lan and Venus is 9.58inc Lan 349.97.

Now plane changes are very fuel costly as I have discovered but I'd rather not use the scenario editor to change my inc, but do it within the constraints of the scenario.

I keep reading that changing your inc is much cheeper in fuel if done at a low velocity at the apogee but even if I extend my apogee out to ApR 9m my inc rate change is only 0.12 deg/sec.

I have tried creating a transX plan with a large plane change and I was under the impression that if done, I would not need to change my orbital inc as this would be incorperated into my transx ejection burn. To be honest at this point I get confused by the Ejection orientation variable in the escape plan stage, changeing this seems to lower my Rinc to about 20deg but I can't get it lower than that. This variable is allways a bit of a mystery to me.

I have however completed the excellent fly tandem tutorial of Mars surface to Venus but this scenario accounts for the inclination in the take off.

P.S. Sorry for long post but I wanted to make myself clear.

Hi Lupin_Yonder,

I'm assuming you're talking about the "2001-Cytherean Station One" scenario, where you have to take an Aquarius spacecraft from Station-V to Venus.

If you set up your second stage (Eject Plan) correctly (Prograde vel: -3.28k Ch. Plane vel.: -1.541k) you will get a Cl. App. value of about 93M, which is pretty good for an ejection burn.

When you switch back to the Escape Plan, you will notice that you are about 57 degrees off plane and it is very costly to get that Rinc down to zero.

But if you change your "Eject orientation" to 57 degrees, you will see the Rinc
reducing to a minimum of about 7 degrees. Also change your Pe distance to 7.087M to match your current orbit.

Those 7 degrees of Rinc. can be reduced to less than 0.01 with two or three burns. Just make sure you make a Orbit+ or a Orbit- burn when your ship passes a node. (When your orbit is close to the gray line in the Escape plan).

After that, proceed with the ejection burn and plan an MCC after you've left Earth's SOI. You shouldn't need more than two corrections for the whole trip, and you can make it to Venus with more than 55% fuel left, more than enough for an orbit insertion burn and then a rendevouz with the orbiting station.

Hope this helps.

Have fun, happy orbiting!

 

[Lupin_Yonder]

Hi Lupin_Yonder,

I'm assuming you're talking about the "2001-Cytherean Station One" scenario, where you have to take an Aquarius spacecraft from Station-V to Venus.

If you set up your second stage (Eject Plan) correctly (Prograde vel: -3.28k Ch. Plane vel.: -1.541k) you will get a Cl. App. value of about 93M, which is pretty good for an ejection burn.

When you switch back to the Escape Plan, you will notice that you are about 57 degrees off plane and it is very costly to get that Rinc down to zero.

But if you change your "Eject orientation" to 57 degrees, you will see the Rinc
reducing to a minimum of about 7 degrees. Also change your Pe distance to 7.087M to match your current orbit.

Those 7 degrees of Rinc. can be reduced to less than 0.01 with two or three burns. Just make sure you make a Orbit+ or a Orbit- burn when your ship passes a node. (When your orbit is close to the gray line in the Escape plan).

After that, proceed with the ejection burn and plan an MCC after you've left Earth's SOI. You shouldn't need more than two corrections for the whole trip, and you can make it to Venus with more than 55% fuel left, more than enough for an orbit insertion burn and then a rendevouz with the orbiting station.

Hope this helps.

Have fun, happy orbiting!

Thank you so much, just the kind of reply I was looking for.
I will give this a try asap and let you know of the results.

 

[dgatsoulis]

I've noticed that the dv required for the plan i suggested to you is about 3700 m/s

This will take the Aquarius a little bit more than 2200 seconds of burn time due to its poor accelaration.

You may want to "brake" the burn into 2 (or more) perigee "kicks".

I did it with two: Started the first kick at 500 seconds to Pe and burned prograde for 1000 seconds and at my second pass from the perigee made the rest of the burn.

 

[Lupin_Yonder]

Thanks dgatsoulis for your help. I have changed my Ej Orientation to 57 as you suggested ( this matched my current Inc which is 57.25 ) but my Rel Inc is now 117.5 deg. Massive . If I change my Ej Orientation I found that with experimenting I could get it down to Rel Inc 21.24 at Ej Orientation -61.82.

Here is a scenario of my current TransX plan Docked to Station V

View attachment 2001 - Cytherean Station One -Lupin.scn

 

[dgatsoulis]

Thanks dgatsoulis for your help. I have changed my Ej Orientation to 57 as you suggested ( this matched my current Inc which is 57.25 ) but my Rel Inc is now 117.5 deg. Massive . If I change my Ej Orientation I found that with experimenting I could get it down to Rel Inc 21.24 at Ej Orientation -61.82.

Here is a scenario of my current TransX plan Docked to Station V

View attachment 4667

Either something is wrong on my end, or the scenario you've posted doesn't have the TransX plan setup properly. I see that you have targeted Venus, but i don't see any Prograde Vel. or Change plane Vel. values set in the second stage (eject plan) when i run the scenario. I also see the Pe distance set to 835.2M !? in the first stage and no change in the eject orientation.

Try this:

BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol_2001
  Date MJD 51944.7765878391
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Aquarius1
END_FOCUS

BEGIN_CAMERA
  TARGET Aquarius1
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE TransX
  Ship  Aquarius1
  FNumber 3
  Int 1
  Orbit True
  Vector  3919576.65103 -537428.385324 5883171.52322
  Vector  -3650.32272161 -6283.53179054 1856.25449977
  Double  3.98600439969e+014
  Double  51944.7765868
  Handle Earth
  Handle NULL
  Handle NULL
Select Target
 0 Escape
Autoplan
 0  0
Plan type
 0  0
Plan
 0  1
Plan
 0  0
Plan
 0  0
Select Minor
 0 None
Manoevre mode
 0  0
Base Orbit
 0  0
Prograde vel.
 1  0
Man. date
 1  51944.7765868
Outward vel.
 1  0
Ch. plane vel.
 1  0
Intercept with
 0  0
Orbits to Icept
 0  0
Graph projection
 0  0
Scale to view
 0  0
Advanced
 0  0
Pe Distance
 2  7086777.87206
Ej Orientation
 1  0.998328332141
Equatorial view
 0  0
Finvars
  Finish BaseFunction
  Int 2
  Orbit False
  Handle Sun
  Handle Earth
  Handle Venus
Select Target
 0 Venus
Autoplan
 0  0
Plan type
 0  2
Plan
 0  0
Plan
 0  0
Plan
 0  1
Select Minor
 0 None
Manoevre mode
 0  0
Base Orbit
 0  1
Prograde vel.
 1  0
Man. date
 1  51944.7744591
Outward vel.
 1  0
Ch. plane vel.
 1  0
Intercept with
 0  0
Orbits to Icept
 0  0
Graph projection
 0  0
Scale to view
 0  0
Advanced
 0  0
Prograde vel.
 5  -3280.39097697
Eject date
 1  51944.7717471
Outward vel.
 6  0
Ch. plane vel.
 3  -1541.09964111
Finvars
  Finish BaseFunction
  Int 5
  Orbit True
  Vector  -4640553924.15 2322933841.98 -3257019223.14
  Vector  4872.67139919 -2345.50957363 3337.54892546
  Double  3.2485863e+014
  Double  52105.247184
  Handle Venus
  Handle NULL
  Handle NULL
Select Target
 0 None
Autoplan
 0  0
Plan type
 0  1
Plan
 0  0
Plan
 0  2
Plan
 0  0
Select Minor
 0 None
Manoevre mode
 0  0
Base Orbit
 0  0
Prograde vel.
 1  0
Man. date
 1  51944.7744515
Outward vel.
 1  0
Ch. plane vel.
 1  0
Intercept with
 0  0
Orbits to Icept
 0  0
Graph projection
 0  0
Scale to view
 0  0
Advanced
 0  0
Draw Base
 0  0
Finvars
  Finish BaseFunction
END_MFD

BEGIN_MFD Right
  TYPE Orbit
  PROJ Ship
  FRAME Ecliptic
  REF Earth
END_MFD


BEGIN_SHIPS
stationV:2001/stationV
  STATUS Orbiting Earth
  RPOS 3919249.07 -537994.15 5883446.77
  RVEL -3650.701 -6283.480 1855.874
  AROT -0.11 -0.02 -91.10
  VROT -0.00 -0.00 7.20
  IDS 0:520 100 1:522 100
  XPDR 500
END
Aquarius1:2001/AquariusIc
  STATUS Orbiting Earth
  RPOS 3919248.10 -537993.90 5883338.56
  RVEL -3650.718 -6283.478 1855.662
  AROT -0.09 -0.02 -91.10
  VROT 0.00 -0.00 7.20
  PRPLEVEL 0:1.000
  NAVFREQ 0 0
  XPDR 0
  DOORS 0 0.0000
  HAB 0 0.0000
END
CytSta1:2001/CytSta1
  STATUS Orbiting Venus
  RPOS 4604968.89 230438.73 5119834.80
  RVEL -4772.219 -2252.200 4393.529
  AROT 27.48 20.78 177.34
  VROT 0.00 -0.00 18.70
  PRPLEVEL 0:0.500
  DOCKINFO 0:0,Aquarius2
  IDS 0:320 100
  XPDR 500
END
Aquarius2:2001/AquariusIc
  STATUS Orbiting Venus
  RPOS 4604956.24 230454.11 5119864.36
  RVEL -4772.219 -2252.200 4393.529
  AROT -152.52 -20.78 2.66
  VROT -0.00 -0.00 -18.70
  PRPLEVEL 0:0.460
  DOCKINFO 0:0,CytSta1
  NAVFREQ 0 0
  XPDR 0
  DOORS 0 0.0000
  HAB 1 1.0000
END
END_SHIPS

BEGIN_ExtMFD
END

When the scenario begins press the FWD button twice to get to the 3rd stage and then the VW button to see the Encounter Plan. Then go back to the first stage to see the Escape plan. I've already adjusted the Ejection orientation to get a Rinc of 7,108 degrees.

Let me know if this works on your end and if you now know how to set it up for yourself.

Have fun, happy orbiting

 

[Lupin_Yonder]

Maybe the problem is differen't versions of TransX cos when I loaded your scenario I also didn't get your TransX plan. The version I'm using is TrasX-3.13.1.3.

Last Night I got to a point where I had copied a reasonable TransX plan into a manoeuvre ( in manoeuvre mode ) and was ready to start the burn. After the first orbit burning for 1000s I still had a lot of Dv left too add and by clicking the base orbits ++ update button I could see that by now I was way off hitting Venus at several G distance.

How Do I correct this in the second burn next orbit?

On the second orbit burn I noticed that my Dv would sometimes increase rather than drop. Is this due to flying inaccurately at the manoeuvre mode target ?

Thanks for the help so far, I'm learning a lot.

 

[dgatsoulis]

Maybe the problem is differen't versions of TransX cos when I loaded your scenario I also didn't get your TransX plan. The version I'm using is TrasX-3.13.1.3.

That's right. I downloaded the version you are using and i can see your TransX plan now. I can see that those 21 degrees of Rinc is probably the lowest you can get with that plan.

The scenario is at MJD 51944 (February 4th 2001) and you have set up MJD 52491 (August 5th 2002) to be your eject date. Why wait that long? Venus is in a pretty good position to make the transfer right "now".

If you set up the following plan on TransX you will make it to Venus somewhere near the end of July 2001.

1. On the second stage (eject plan):

1a.Reset the eject date and then add about half a day (51945)
1b.Set the Prograde Vel. to -3.299k
3c.Set the Ch Plane Vel. to -1.541k

2.On the first stage (escape plan):

2b. Set your Ej. Orientation to 57.06 degrees.

That should get you a Rel. Inc of 7.22 degrees and the dV required for the TVI is 3711 m/s, a 2454 seconds burn according to [nomedia="http://www.orbithangar.com/searchid.php?ID=4530"]Burn Time Calculator 2.0[/nomedia]

Here is the scenario with the plan already set:

BEGIN_DESC
Contains the latest simulation state.
END_DESC

BEGIN_ENVIRONMENT
  System Sol_2001
  Date MJD 51944.7802744131
END_ENVIRONMENT

BEGIN_FOCUS
  Ship Aquarius1
END_FOCUS

BEGIN_CAMERA
  TARGET Aquarius1
  MODE Cockpit
  FOV 50.00
END_CAMERA

BEGIN_HUD
  TYPE Docking
  NAV 0
END_HUD

BEGIN_MFD Left
  TYPE User
  MODE TransX
  Ship  Aquarius1
  FNumber 3
  Int 1
  Orbit True
  Vector  2558240.20337 -2471091.26017 6132224.74718
  Vector  -4816.72525213 -5742.64105259 -307.735560687
  Double  3.98600439969e+014
  Double  51944.7802733
  Handle Earth
  Handle NULL
  Handle NULL
Select Target
 0 Escape
Autoplan
0 0
Plan type
0 0
Plan
0 1
Plan
0 0
Plan
0 0
Select Minor
 0 None
Manoeuvre mode
0 0
Base Orbit
0 0
Prograde vel.
 0  0
Man. date
 0  51944.7802733
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Pe Distance
 0  7090062.34951
Ej Orientation
 0  0.995989590943
Equatorial view
0 0
Finvars
  Finish BaseFunction
  Int 2
  Orbit False
  Handle Sun
  Handle Earth
  Handle Venus
Select Target
 0 Venus
Autoplan
0 0
Plan type
0 2
Plan
0 0
Plan
0 0
Plan
0 1
Select Minor
 0 None
Manoeuvre mode
0 0
Base Orbit
0 1
Prograde vel.
 0  0
Man. date
 0  51944.7801869
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Prograde vel.
 0  -3298.76631639
Eject date
 0  51945.0318903
Outward vel.
 0  0
Ch. plane vel.
 0  -1540.81929164
Finvars
  Finish BaseFunction
  Int 5
  Orbit True
  Vector  -4664414628.45 2280042864.05 -3251952472.73
  Vector  4851.58676727 -2355.8034497 3388.38470998
  Double  3.2485863e+014
  Double  52105.5960525
  Handle Venus
  Handle NULL
  Handle NULL
Select Target
 0 None
Autoplan
0 0
Plan type
0 1
Plan
0 0
Plan
0 2
Plan
0 0
Select Minor
 0 None
Manoeuvre mode
0 0
Base Orbit
0 0
Prograde vel.
 0  0
Man. date
 0  51944.7801029
Outward vel.
 0  0
Ch. plane vel.
 0  0
Intercept with
0 0
Orbits to Icept
0 0
Graph projection
0 0
Scale to view
0 0
Advanced
0 0
Draw Base
0 0
Finvars
  Finish BaseFunction
END_MFD

BEGIN_MFD Right
  TYPE Orbit
  PROJ Ship
  FRAME Ecliptic
  ALT
  REF Earth
END_MFD


BEGIN_SHIPS
stationV:2001/stationV
  STATUS Orbiting Earth
  RPOS 2557794.50 -2471627.00 6132321.08
  RVEL -4816.968 -5742.400 -308.147
  AROT -0.19 0.01 42.23
  VROT -0.00 0.00 7.20
  IDS 0:520 100 1:522 100
  XPDR 500
END
Aquarius1:2001/AquariusIc
  STATUS Orbiting Earth
  RPOS 2557792.24 -2471625.31 6132196.10
  RVEL -4816.992 -5742.384 -308.374
  AROT -0.16 -0.01 42.23
  VROT -0.00 0.00 7.20
  PRPLEVEL 0:1.000
  NAVFREQ 0 0
  XPDR 0
  DOORS 0 0.0000
  HAB 0 0.0000
END
CytSta1:2001/CytSta1
  STATUS Orbiting Venus
  RPOS 2880244.19 -486456.94 6240071.38
  RVEL -5966.310 -2211.361 2581.309
  AROT 27.45 20.79 13.55
  VROT -0.00 -0.00 18.70
  PRPLEVEL 0:0.500
  DOCKINFO 0:0,Aquarius2
  IDS 0:320 100
  XPDR 500
END
Aquarius2:2001/AquariusIc
  STATUS Orbiting Venus
  RPOS 2880231.54 -486441.58 6240100.96
  RVEL -5966.310 -2211.361 2581.309
  AROT -152.55 -20.79 166.45
  VROT 0.00 -0.00 -18.70
  PRPLEVEL 0:0.460
  DOCKINFO 0:0,CytSta1
  NAVFREQ 0 0
  XPDR 0
  DOORS 0 0.0000
  HAB 1 1.0000
END
END_SHIPS

BEGIN_ExtMFD
END

Don't forget to get the Rel. Inc down to less than 0.1 by burning Orbit+ or Orbit- when your ship is near an ascending or descending node. (where the gray line intersects with your current orbit, shown on the first stage of the plan).

After you've made the TVI, TransX will automatically delete the first stage of the plan, once you are far away from Earth and show you the stage 2. At first you'll notice a large Cl App Distance, but as you timewarp you will see that distance being reduced. (if you executed your ejection correctly).

Start setting up a Mid Course Correction (MCC) when that distance reaches a minimum and then starts to go up again. After that i usually do another correction at about half the distance of my first MCC and the target. (In this case Venus).


Now, a different "approach".

If you MUST leave on the date you have initially set up, here is a little trick i learned from flytandem.
I use this when my orbit has a very high Relative Inclanation to the TransX's ejection plan and/or (in this case) when my ship has poor acceleration.

1.First use the scenario editor to set the date 6 days before your eject date (52485). Reset all your settings on TransX and setup the plan again. The new settings you will use, should be close to the ones you had, but they will not be EXACTLY the same. (That's because of the change in the date).

2.Once you are happy with the plan, undock and make a prograde burn untill your ApA is about 249.0M. That's close to the edge of Earth's SOI. (G=0.51 on Orbit MFD).

3.When you are close to your ApA make another Prograde burn to circularize your orbit.

4.Make the Orbit+ or Orbit- burn at the right time to get the Rinc down to zero. (It will take much less burn time now)

5.When your ship is almost opposite to the Pe shown in the escape plan of TransX (Ang to Pe 179.5) burn retrograde to get your PeA as close to the atmosphere as you can. (I usually go for an ApA of 230k)

6.Set your Pe Distance on TransX to match your current PeD on Orbit MFD.

This is a way to make big plane alignments and use less fuel.
(You can read about the advantages and disadvantages of different types of orbits here)

Even with that retrograde burn to get your Periapsis back near the atmosphere, it should take less fuel than making the alignment burns at your starting orbital altitude.

That's about it for now.

Have fun, happy orbiting

 

[Lupin_Yonder]

Thanks so much, I'm downloading burn calc 2 atm and will let you know the results.

The reason why my Ej was so far in the future was because I was under the impression that the best practice to setup trans X plans is to first find a date where the target Planet is closest then work from that point with the other variables.

 

[dgatsoulis]

The reason why my Ej was so far in the future was because I was under the impression that the best practice to setup trans X plans is to first find a date where the target Planet is closest then work from that point with the other variables.

And you would be right. It is a very good way to set up a TransX plan.

But sometimes your plans DON'T have to be "Hoffman Transfers".

(As you've already found out) you must also take into consideration the plane alignment's dv required for your plan. Especially when you fly ships with a poor thrust/weight ratio.

A good way to look at it, is to find out your ships maxdV capacity (If you don't want to do the Math, it can be easily done with the burn time calculator) and then see if your ship can handle the dv required for your trip. (Taking into consideration the dv required for your target's Orbital Insertion burns also).

Hope my post helps,

Have fun, happy orbiting


P.S. If you want to see ART being made in Orbiter with TransX you may want to see the Aerosling playback on this page.
This is advanced level material, but when you have a good grasp of TrasnX you'll agree with me that... flytandem is an artist!

P.P.S. I strongly suggest to LEARN how to do the MATH FIRST (with pen and paper) and THEN use shortcuts. You'll find it much more satisfying. In the same way you know how to add/subtract/multiply/divide and THEN use a calculator.

 

[Gumdrop]

Old topic but I was just attempting this scenario yesterday so I thought I would add some advice -- for the record.

Your initial orbital plane is indeed unaligned with the ejection orbital plane but I found it helpful to rotate the ejection plane so that the ascending and descending nodes are lined up with the planned hyperbolic ejection orbit's periapsis. This way you can boost yourself into a high apoapsis (100M or so) and do a large plane change. The high altitude will use considerably less Delta-V PLUS you have already gotten a head start on your ejection.

Just a useful tip...cheers.