TUTORIAL FOR NEWBIES: USING TRANSX MFD. Beta version 0.1
Made by José Pablo Luna Sánchez. 2007.

Note: This is a beta tutorial, which means that it is not yet ready (incomplete) and it is being posted for discussion purposes and not as a definite tutorial.
As it is a beta, it may contain inaccuracies and problems that could misinform a newbie, mostly in the part of midcourse corrections.

Even if there is already a tutorial in a sticky thread by YesRushGen about TransX, I thought that a visual understanding of TransX MFD was required.
Very often pure text is not enough to understand instructions, you need to actually see things in order to have better awareness of what you do.
So I came to the idea of actually showing everything graphically so users may have visual awareness of what they are doing.

This is a tutorial based on my understanding of TransX after doing some research at the Orbiter forums and after testing by myself.
If you find any inaccuracies, please report them at the Orbiter forums so they can be corrected.

When I mean newbies, I mean people who has never used TransX.
Those who use this tutorial should at least know how to take off from Cape Cañaveral, go to orbit and dock with ISS.
I will not cover concepts related to orbit alignment, orbit circularization or raising apoapsis, which are necessary to go to ISS.

If you are a newbie and you have never tried interplanetary travel, I would advise to read my tutorial about Interplanetary MFD 4.2.1 at www.orbithangar.com and not this tutorial.

SPECIAL THANKS

YesRushGen for providing most of the steps for the Earth to Mars trip that were used here.

GENERAL CONCEPTS ON USER INTERFASE OF TRANSX MFD

Here we will cover some concepts you need to understand TransX displays.
We are not going to describe steps yet.
You need to understand how things look, before you even try to attemt a trip.

When you use TransX, you will have to plan your trip in Stages (FWD and BCK buttons).
Each Stage has several Views (VW button).
Each View has several Variables (VAR and -VR buttons).
Each Variable has several possible Values (++ and -- buttons).

For example, if we travel from Earth to Mars, we might need to plan our trip using 3 stages.
First you need to escape Earth gravity, then you need to cruise while affected by sun gravity and then you need to arrive to Mars.
For each stage you need to select views and variables and set values.

The structure of Views, Variables and Values is like a tree.
Some values may enable some views too.
Let's see this diagram.

For example:

• Set Setup > Select planets/moons > Moon or Planet, and it will enable the Escape Plan and Eject Plan views.
• Set Manoevre > Manoevre mode > On and you will have several variables enabled in the Manoevre view.

This table will be a very useful reference if you use TransX MFD.
This will help you to find values, variables and views with no effort.

From now on I will refer to views, variables and values and will not tell you which buttons to press.
For example, if you are in Eject plan and I tell you to set Setup > Graph Projection > Focus, you may need to press VW (to change view) and then press VAR (to select graph projection) and then ++ (to select focus value). You have that table, so now you know how to surf between views, variables and values.

BASIC CONCEPTS ON PLANNING

When you plan your trip, you may see something like image that is shown in the diagram.

• The Blue lines indicate the orbits and the current planet positions.
• The Yellow lines indicates your planned trayectory, and the expected points where your ship and the target planet will be at the end of the planned stage (closest approach).
  You may need to make those two points as close as possible if you want to reach your destinatation planet.
• The Green line indicates your current ship trajectory.
• The Gray line indicates the intersection of two planes: your planned trajectory plane and the destination planet orbit plane.
  You may want this line to be aligned with the final position of your planet and the final position of your ship so you don´t end up below or above your destination planet.
  Having the node aligned with your ship's and planet's final position means that you will intercept the destination planet.
  The planned trajectory and the planet orbit are inclined, so you have a relative inclination that could make you to miss the target.

This diagram shows the sun centered stage, the cruise stage, where we go from Earth to Mars.

The escape stage may look like the following picture.
This is the stage where we escape from Earth's gravity.
In the escape stage we are ejected from Earth's Sphere Of Influence (SOI).
SOI is the zone where Earth's gravity has a very significant importance, so basically inside of it we might say we perform Earth centered maneuvers.
Once we are out of Earth's SOI, we enter sun's SOI.

Notice that we have 3 vectors of velocity AFTER the ejection burn (that causes us to go along the planned trajectory) at the ejection point.
The actual Velocity vector is composed by the sum of those 3 components.
Those 3 components are perpendicular to each other.
Velocity vector is the velocity needed to achieve the planned trajectory described in the cruise stage, and that's why we define these velocities in the cruise stage and not in the escape stage.

• Prograde velocity is the velocity in the prograde direction.
• Outward velocity is a velocity that makes us to move away from the planet.
  It is aligned with the center of the planet in circular orbits.
  In non circular orbits it is just perpendicular to prograde in the orbit plane and may not be aligned with the center of the planet.
• Change plane direction is the velocity in normal or antinormal direction (so it is perpendicular to our current orbit plane).

  

When we plan our trip we need to know what each velocity is.
Here a more detailed view of the different names of each velocity in different MFDs.

Now let's try to plan a real trip.

PLANNING THE TRIP TO MARS

• Open the Checklists directory and open your Quickstart scenario.

• Press F1 to enter the cockpit.
• Press F8 twice to see the 2D panel where we are going to work.



• Press SEL button
• Select TransX

  

  Just like in Orbit MFD, you'd be seeing planet Earth as a gray circle and your orbit as a green ellipse.

• Set Setup > Select planets/moons > Escape.
  With this stage now set in its basic configuration, TransX is now ready to plan the next stage, which is the cruise stage.
  If you have problems to set this Escape value, you may need to use the reference table above, to find where this value is and what buttons you need to do this.

  

PLANNING CRUISE STAGE

Let's make a break to understand what we need to do.
Do not touch your MFD until I told you to do so.

Planning criuse stages means that you need to adjust some variables:

• You set a target planet/moon
• Adjust prograde velocity. That tells you how elliptical will be your trajectory to reach the planet.
• Adjust launch date. That will make the final planet position and the final ship position in your planned trajectory to meet.
• Adjust change plane velocity that will move nodes resulting of ship trajectory and destination planet orbit. You need to align the nodes with the final position of your craft. That will make you not to end above of below your destination planet when you get there.

  

So basically you move final planet position and final ship position together and then you move the nodes to the final position of your ship.
So basically you are aligning 3 straight lines.
Now let's continue with the checklist, lets do some changes in our TransX MFD...

• Press FWD to go to the next stage (stage 2)
• Set Setup > Select planets/moons > Mars
• Select Eject Plan > Prograde Vel.



• Increase prograde velocity with ++ button until the planned trajectory (yellow ellipse) intersects the orbit of Mars.
  Notice that your screen may not look the same, but the important thing is that it intersects the orbit of Mars.

• Select Eject Plan > Eject date
• Use ++ and -- buttons to make the two yellow straight dotted lines (final ship position and planet final position) are together.
  This will adjust the launch date.
  If those lines are already together, ignore this step.
• Select Eject Plan > Ch. plane vel.
• Try to align the gray straight line (or is it white?) with the final positions of planet and ship with the ++ and -- buttons.
  You need to minimize the closest approach (Cl. App.)
  Notice that your screen may not look the same, the important thing is that all 3 straight lines are together.

  

• You will need to try combinations of Prograde Vel., Eject Date and Ch. plane vel. so you minimize the closest approach.
  Remember that you have ADJ and -AJ that allows you to do some fine tuning of values.
  You need to make Cl. App. to be just below 2G (which is 2 million km).
  Fine tuning Cl. App. to lower values is innecesary, because you will have midcourse correction burns.
• Take note of the Eject date you just have. You will need it later.

  

PLANNING DEPARTURE FROM EARTH

• Press BCK button to go back to stage 1.
  You now see the trajectory we need to exit Earth's gravity.
  We need to finish our escape plan.



• Select Escape Plan > Pe Distance
• Set tuning scale to Medium using -AJ button
• Using -- button set value to 6571M

  

This will set the altitude of the circular orbit from which you plan to depart.
In this case it is 200km above the ground (6571 km).

• Set Setup > Graph projection > Focus
  This will change your projection from Ecliptic to a projection that makes things easier to visualize, you will have always be travelling counterclockwise.
• Select Escape Plan > Ej. Orientation
• Set a value for the eject orientation that will determine a launch heading (and therefore an orbit inclination).

  

  If your heading ranges from 0 to 180 it will take advantage of Earth rotation.
  If your heading ranges from 180 to 360 it will go against Earth rotation.
  If your heading is 90 you are taking the more fuel efficient orbit, for it uses Earth rotation to maximum gain of speed.

DEPARTING FROM EARTH

First we need to get close to the launch window.
Notice that the launch window and the ejection date are not the same.
We launch at the launch window, we make some trajectory adjustments and later we start performing the ejection.
Before we eject we need to do some previous steps.

• Press F4
• Select Custom >Scenario editor > Ok > Date
• Input the Eject date you had minus 0.5 in the MJD field.
  It would give us 12 hours to reach orbit and be ready to perform an ejection burn.
  In this image Eject date in stage 2 is shown.
  As you see Eject date in this example is 51978.6980 while the one we input substracts 0.5, so it ends up being 51977.6980
  Your Eject date may be different from the MJD date you set.

  MJD date = Eject date - 1



• Press Apply button
• Close Scenario editor window
• Close Main window

Now we need to wait for the launch window.

As you may notice there is an intersection between the orbit we could see in MapMFD and the ejection trajectory (which doesn´t appear in Map MFD).
That intersection is a point called node.
Due to Earth rotation, the launch site will move, so we need to find a moment when the node and launch site are as close as possible.

If we launch now and node and launch site are not close, we will spend much more precious fuel aligning orbits.
Even if we launch when launch site and node are very close, we still have a Relative Inclination (RInc) between ejection trajectory and the orbit we could achieve from our current latitude.
We need to make RInc to be as low as possible.

When we are landed we can´t see what is our current RInc.
It will appear in TransX MFD when we take off if we have the ejection stage visible in our MFD.

• Select Escape Plan view for Stage 1
• Press T to accelerate time.
• Press R to decelerate time when launch site and node are aligned so we can launch.
  Your display may be different, but the important thing is that we have launch site and node more or less aligned.
  If we could achieve a circular orbit and we can align our orbit with the ejection trajectory before Pe MJD (when we perform the ejection burn), we would be very efficient.
  But it is very likely that we won't be like that.
• Take off and the RInc data will appear, try to find a heading that minimizes it.

  

• Turn on Orbit MFD in another MFD screen
• Select Escape Plan > Pe Distance
• Raise apoapsis until ApR is equal to Pe Distance



• Circularize your orbit
• Wait until your ship gets close to the node.



• This is how Trans X display would look.



• Go normal or antinormal and make a burn to reduce RInc.
  You will stop the burn when either RInc is close to 0 or when the nodes are perpendicular to your craft position.
  In the following example, nodes are perpendicular to your craft position.



• Notice that if nodes are perpendicular to your craft position, you will need to wait until you reach a node to make another normal or antinormal burn to reduce RInc.
  As RInc gets close to 0 you may use your RCS engines in linear mode to do some fine tuning of RInc to make it get closer to 0.



• Activate Prograde autopilot
• Wait until T to Pe gets close to 0 and start the ejection burn and keep burning.



• Press FWD to see stage 2
  The current orbit will appear in TransX MFD as soon as it becomes hyperbolic.



• Continue the burn until planned trajectory and current trajectory fit together.



• Turn prograde autopilot off
• Press BCK to see stage 1.
  Your current orbit could be misaligned with the planned trajectory.
  If that's the case, we need to align it.
  It means we need to correct our outward velocity component to match the planned trajectory



• Select ROT mode (RCS rotation mode with / key)
• Select OBT (Orbit) display in your HUD.
• Rotate 90 degrees to the left or to the right (from prograde orientation), depending on the type of misalignment.
  Your HUD may look like this (prograde direction should be to the left or to the right, depending on the direction you turn)

  

This is how the ship looks when facing the planet (inward).

This is how it looks when facing space (outward).

• Make a burn until both trajectories are aligned.
• Activate prograde autopilot
• Burn until DeltaV is near 0. You may use your RCS engines in linear mode for fine tuning your DeltaV.

Congratulations now you are in your way to Mars.

MIDCOURSE CORRECTION

• Open TransX in the other MFD and change stage, so you can see stages 1 and 2.
• Make sure Stage 1 shows Escape plan view.
• Accelerate time until your ship is at the node between your trajectory and Mars orbit.



• Turn Prograde autopilot on
• Make sure your RCS thrusters are in linear mode
• Use keypad 6 and 9 keys to bring DeltaV as close as 0 as possible.
  You may do some fine tuning by pressing CTRL 6 or CTRL 9.
• Use keypad 2 and 8 keys to bring RInc near 0.
  You may do some fine tuning by pressing CTRL 2 or CTRL 8.
• Use keypad 1 and 3 keys to bring RInc near 0.
  You may do some fine tuning by pressing CTRL 1 or CTRL 3.
• Accelerate time. Stage 1 screen will be replaced by stage 2 and you will wait until you are half the way.

Notice that course corrections are performed going prograde and using RCS thrusters in linear mode.
The final effect of out thrusters is very similar to the one we had when we faced Earth or space when we departed.
But in this case RCS thrusters are strong enough, so we do not need to face Earth or space.

While we are prograde (Prograde autopilot is on) our RCS thrusters will change the three components of our velocity.

• Prograde velocity: Keypad 6 and 9, Main engine, retro thrusters
• Outward velocity: Keypad 1 and 3.
• Change plane velocity: Keypad 2 and 8.

The goal is always to change our velocity vector to reduce the closest approach distance.
The bigger the closest approach the more distant will be from Mars.
We need to at least enter Mars SOI if we want to make our orbit circular.
And if we want to spend less fuel, we better reduce our closest approach distance.

Another Mid course correction can be done about half the way between the two planets.

• Use retros or main engine to make Cl. App (closest approach) as small as you can.
  It may not reach 0.
• Use RCS linear mode, keypad 6 and 9 keys to make Cl. App. even smaller
• Use keypad 2 and 8 to make Cl. App. even smaller.
• Use keypad 1 and 3 to make Cl. App. even smaller.
• Now use fine tuning to make it even smaller, just like we did before.



• Wait until you are 3/4 of the way to Mars and do another midcourse correction.