Voyager Setup

This exercise is just practicing doing a flightplan starting from being parked on Earth surface, planning a Voyager-like flight to eject Earth to Jupiter with a sling to Saturn.

This tutorial is designed to be used with Orbiter running in Window mode with the scenario "Voyager Setup" which is available here. Extract it into your Orbiter folder and it will then be found in your "Scenarios/Flytandem Tutorials" folder when you start Orbiter.


Bring up Transx in both left and right MFD's.

Note in the upper right that you are in Stage 1 of 1 and the View is "Setup".

Click either MFD the "++" button as needed to toggle to a target of "Escape".

Click the right MFD the "FWD" button. You have now created a Stage 2 in the right MFD. The Sun is at center and the blue circle is the Earth's orbit.

We now want to get a the Stage 2 target set as Jupiter. In the right MFD note you are in the View "Setup" and so now click the "++" as needed to toggle the target to Jupiter.

With the right MFD start planning the eject. Click the "VW" button to toggle to the View:Eject Plan as shown in the top right.

Become familiar with the variables of the eject. These are seen using the right MFD "VAR" button. Click it and scroll around through the variables
Prograde vel.
Eject date
Outward vel.
Ch. plane vel.

Now in each of these use the "++" and "--" button to play around with what they do. Remember the "ADJ" buttons change the rate of adjustment and include a Reset choice. Voyager 2 launched on August 20 1977 so advance the Eject date to that date. Unfortunately the date in the transx variable is only the MJD. But by looking at the sim date being currently Aug 10, advance the MJD. by 10 days of the current sim MJD ie; to 43375.****.

Try to get your planned trajectory to look something like the following. Note the white line which is the intersect of your trajectory plane with the plane of Jupiter's orbit. You need to get it to swing to meet where you cross Jupiter's orbit. Your goal is to reduce the closest approach to Jupiter (seen under "Cl. App. (rough)" on the left side of the right MFD).
If you are having trouble try the following variable values:
Prograde vel.= 9.718k
Eject date= 43375.4409
Outward vel.= -3.505k
Ch. plane vel.= -1.474k

Once you get the closest approach down under a few G's click the right MFD "FWD" button. You now have created the next Stage which is your encounter to Jupiter. Good idea to see more detail of the encounter by clicking the right MFD "VW" button as needed to see the Encounter view. You might see something like the following.
Let's leave the right MFD in this Stage and View and use the left MFD to get ready to continue adjusting. Left MFD click "FWD" until you are in Stage 2 and then "VW" as needed to toggle to the "Eject Plan" view.

We can see what the adjustment will do by looking at the right MFD. But all we know at this point is that indeed we are with an eject plan from Earth that will take is close to Jupiter. The purpose is to sling to Saturn. So let's set up the next stage...


SET the NEXT STAGE: The right MFD is in Stage 3. It doesn't matter whether you are in the Encounter view or Setup view, either way now click the "++" or "--" button repeatedly and you scroll through the moons of Jupiter with each one showing your closest approach by the yellow dashed lines, and leave it when you get to the choice "Escape". Now click the "FWD" button which creates Stage 4. The green orbit shows what will happen with your current plan after you sling past Jupiter.

TARGET:Click the right MFD "VW" button as needed to get "Setup View" in the top right. Click "VAR" button and scroll through to get "Select Target". It may have already been there but it's good to see the choices. The target says "None" at this point. Click the "++" or "--" buttons to select Saturn.

SLING: click the right MFD "VW" button as needed to get the "Sling Direct" view.

SCALE OF VIEW: Depending on how close your initial plan to Jupiter was it's possible the resulting green orbit of Stage 4 (right MFD) is HUGE and well outside the orbit of Saturn. This forces the view of Saturn to be too small to see since we are currently seeing all of the green orbit. If this is the case you can change the scale by clicking the right MFD "VW" to Setup then "VAR" as needed to get "Scale to view" and then the "++" button as needed to toggle to "Target". Then go back to the "Sling Direct" view by clicking the "VW" button as needed. ADJUST: We need to adjust to get the yellow dashed trajectory close to Saturn. You'll see the two radius lines going from the center of the right MFD out to Saturn's orbit. Might look something like the following image (ignore what your green line looks like at this point).
With the right MFD click the "VAR" button and scroll through the various options. "Inherit vel" should be "On", if not click the "++" to turn it on. You now want to adjust the "Outward angle" and the "Inc. angle" (inclination angle) one at a time back and forth using the "++" and "--" buttons using gradually smaller adjustment increments "ADJ" to reduce the closest approach "Cl. App. (rough)" much like you did in getting your eject from Earth to hit Jupiter. I suggest that you first adjust (click and hold) the outward angle set with coarse increment and swing it around a full 360 adjustment to see what happens. It might make this step clearer as to what's happening.

Eventually when you have brought the Cl. App. to a minimum (should be well under 1G) you might find your yellow lines hiding behind the white line and approach distance looking much like the following image. (continure to ignore the green orbit trajectory)
Now click the right MFD "FWD" button and see what this encounter with Saturn looks like. Click the "VW" button as needed to toggle to see the Encounter view. The green line is your orbital path relative to Saturn (the white circle). It's not critical to be close as shown in the next image. Just have the green trajectory within a few diameters of Saturn at this point.
Use the "BCK" or "FWD" buttons on each MFD to have the left MFD on Stage 2 and right MFD on Stage 3 as shown in the top right of each MFD.


In the left MFD toggle the "VW" button to get the "Eject Plan" view so you'll have access to the variable of you eject from Earth.

In the right MFD toggle the "VW" button between "Setup" and "Slingshot". The Setup view is an overhead view of your trajectory around Jupiter. The Slingshot view is an inline or horizontal orbital plane view looking at Jupiter with the dashed yellow line showing the radius of the desired Pe and the green line showing your currently planned Pe (a short line is a smaller Pe). Your goal is to modify the velocities in Stage 2 (left MFD) to get the green line (right MFD) to match the yellow line both in direction and length. Important to watch the numbers in the lower left of the right MFD. As the two lines get close try to get the R. Inc close to 0 (zero) and Pe Ratio close to 1. (The Window size of Orbiter makes it just barely enough to see both the right MFD graphics and have access to the left MFD buttons). When the adjustment is done it might look like the following image.

Changing the Past affects the Future!

Click the right MFD "FWD" to stage 4. You'll probably notice that the initial nice close approach that you previously made to Saturn has changed. This is because the changes you made to hit the sling position have changed the time and speed and direction of your arrival at Jupiter and since Jupiter and Saturn are moving it consequently has changed what will be needed to hit Saturn. Don't worry, it's not an endless loop. Simply readjust the outward and Inclination angles in stage 4 to get the "Cl. App." low again, then look at stage 3 to see what change THIS has done to you yellow radius line. You'll probably see that it has changed it but not very much so getting the green line back onto the yellow line will require only small adjustments which probably will not affect the Saturn encounter very much.

SUMMARY: You now have a 5 stage plan with the stages looking something like the following 5 images.

Now in either MFD...

Click back "BCK" as needed to get to Stage 1.

Then click the "VW" to get the "Setup" view as shown in the upper right.

Click the "VAR" until it toggles to say "Select Target"

Click the "++" button until it toggles to show "None"

Click the "FWD" button.

These steps are the transx equivalent of CTL-ALT-DEL. ;)

Sorry about that, all your stages have been deleted. I know it hurts. But it's for your own good. When you actually fly the plan, you will no doubt have plenty of deviations in your eject burn from Earth that require manoeuvre corrections going to Jupiter which will rapidly cause the sling to Saturn to change. Get fast at going back and forth between setting the desired sling to Saturn and correcting your current trajectory to get the green Pe line to match the yellow Pe line. Try setting up this flight plan again (if possible without refering to the tutorial). If you can do that then wait 24 hours and do it again. Or maybe try adding Uranus after Saturn making a total of 7 stages.