Manual

Manual Version 1.4

Copying / Warranty

This software is free software and you can freely distribute it with out any fee. All the files must be in place. This software is the property of Jarmo Nikkanen. It is also a Windows software and there is NO WARRANTY of any kind. There is no guarantee of any system damage or miss calculations it might cause. Using this software is at your own risk. This software is created for Martin Schweiger's "Orbiter" the space flight simulator version 021202.

Installation

Unpack the package in to the Orbiter installation folder. Unless you have all ready done.

Manual sections:

Begin
Plane changes
Capture burns
Transfer
Map
Approach
Aero-brake
Orbital

Approach to Mars

Key Controls

A	Approach program	R	Reference, Approach selection
X	Transfer program	T	Target setup
N	Map	M	Display mode
F	Next Program	P	Projection
I	Next Page	1-6	Custom buttons

I	will start this MFD

Begin

Interplanetary MFD is mostly designed for interplanetary travels. Of course it can be used for Earth to Moon trajectories and some orbital maneuvers. You should all ready be familiar with the orbiter, MFDs and a basics of orbital mechanics. Many programs will share the information with a Map, that is a general display for graphical data. Trajectory generated by a trajectory engine is plotted to the Map. I-MFD is using auto referencing so you should not need to touch (Ref) button very often. You can override the auto reference manually if needed.

When inputting numerical data it is possible to define a unit. d=day, h=hour, k=kilo, M=mega, g=giga, a=AU, b=bar, u=micro. m=milli. "12d" means 12 days. Also "16e-2" will work

Some words about plane changes

	Basics: Here is an image that shows a plane change. The plane change will always happen in a node that is a point where two orbital planes intersect each other. In this case ship´s orbital plane and Mars's orbital plane. You should always check the plane alignment when you pass the node. Magnitude of the plane change impulse is greatly depending from the velocity that the ship is moving and relative inclination (an angle between orbital planes). The plane change should be made accurate. Even if the relative inclination is small 0.1 deg it may become a great distance after a voyage of few AUs as shown in the image. If the plane change fails or it is drifting from some other reason. It is possible to make a course correction to create new opportunity for the plane change. This will happen by using P2. Auto LoN will seek the plane change position so that the sum of correction and plane change burns is minimum. Other values should correspond ship´s current course. In most cases the Auto LoN will offer you an orbit where the LAN is at the intersection point. There wont t be a plane change. That's ok when you are targeting the planet it self but there may yet come even greater plane change if you are going to some of the moons. Note: Approach program may not work correctly if there is a plane change between ship and target. dV = 2/r * sqrt(mya(1-e^2)) * sin(Rinc/2) = 2hsin(Rinc/2) / r plane change used in orbital program dV = Rinc sqrt(mya(1-e^2)) / r = Rinc * h / r, where h is angular momentum plane change used in orbiter
Pic. One	Positions for plane changes: DeltaGlider is approaching the Jupiter however we have set a target to the orbit of Europa. And we have to make a plane change. When the ship is in hyperbolic transfer orbit it is good to make a burn if the node is far from the periapis. Like in a picture one. That will took 45 seconds for 20 degree change it's OK. The worst possible case is where the node is close to periapis as shown in a picture two. That will took 134 seconds for 5.4 degree change that's too much. If we examine this little more it is not that bad after all. In this kind of case just do not make the plane change, make the retro-burn to enter elliptical orbit as shown in a picture three. There is new opportunity for the plane change close to apoapis. That's a great place to make that burn. That will only took 19 second to make the same plane change that would have taken 134 second in periapis. If the Ap distance is higher the burn time would be even lower. You can also use P2 to plan the plane change in a position where it's magnitude in low. Targets are different in pictures but do not care about that.
Pic. Two	Pic. Three

Capture burns

This picture shows a different methods to enter a circular orbit (7000km) from a hyperbolic transfer orbit. Middle section shows probably the most common method. On the top of the picture pilot fires a retro rockets to slow down the speed and decrease the Pe distance to 7M. That burn will take 85 seconds. At the periapis pilot makes an other retro burn to enter the circular orbit. Total burn time is 194 seconds. That's the highest value in these three methods. Left picture is showing a case where the ship enters elliptical orbit after a huge retro burn at the hyperbola periapis. And a second small burn at the periapis again to enter circular orbit. That's makes 191 seconds total. Right side picture is showing the minor course correction using P2 magnitude of 8.8 seconds. Orbit circulation burn at the periapis magnitude of 160 seconds that makes the total burn time to169 seconds that is significantly smaller than in two other cases.

Warning: We can not assume that the method would be as good in all situations.

Warning: Plane changes are not notified. Plane change should be done at highly elliptical orbit as shown in a previous chapter. This, however won't change the total burn time except by the magnitude of plane change and that is the same in all these cases.

Note: This scenario is distributed with I-MFD "MarsApproach" Approach to Mars

Transfer

Transfer program is used for course corrections and interplanetary transfers. Most transfer programs lets you to define delta velocity and ejection time. However this transfer program offers few other ways to do that. This was just an experiment but after all it has worked much better than I first imagine. So P2 is now upgraded to full status as a navigational tool. This program may offer you a transfer orbits those are not so fuel efficient. But you should be able to calculate transfer orbit even if the planet alignment is not optimal for transfer. However I am sure that this program will also save a fuel. As calculated above. Also there are no program for all kind of problems. You should learn to understand what the sub-programs (P1,P2,P3) are doing. Think about transfer program as an toolkit of navitational tools. Some maneuvers requires usage of multible tools. Three tools (P1,P2,P3) can be connected to each other at the same time.

Program - P1

P1 is traditional transfer program using delta velocity and launch time (Lnc) or launch position (Tra), where 0 deg is periapis. Negative dV indicates retro-grade burn.
New option is escape, when the escape is selected dv is outward velocity relative to velocity of the planet. That can be positive only. P1 can be used for planet escapes for an example.
Future plans: Support for 2-body escape like from the Moon to the Mars

Program - P2

P2 (Mode 2) is planned for course corrections and transfer calculations. It allows definition of transfer orbit using a longitude of node (LoN), a longitude of apoapis (LPe, LAp) and a distance of apoapis (ApD, PeD). Setup reference and target after selecting the program. Reference first and target must orbit the reference planet. Traget can be also one of the specials (g, r, e). Also target should be the same as the target in a map especially when the position of (LoN) has a greater meaning. If the target is different you may experience some weard actions like the node is not moving or moving weardly.

Warning: When using P2 to move from retro to pro-grade orbit or wice versa the trageting vector may start to move with great speed when the ship's orbit will cross the planet center. Do not try to follow it. It will settle down in a few seconds.

A little of theory
There are two static points in a transfer orbit the reference object and the ship. These two points are forming a line known as the radius vector and that's static. It means that it can change only with the time. Where ever you select the third point, orbital plane will rotate around the radius vector and that will set some limitations. In this mode the third point is selected from the target plane and you can adjust it's longitude (LoN). So the LoN is the primary setting even if LAp is more used. LoN setting will come more critical when the inclination between orbits is greater. LoN and LoN+PI are also the positions where the plane change will occur. The longitude of node (LoN) will also effect to the magnitude of the plane change impulse. P2 program will automatically decide whether this LoN represent the ascending node or the descending node. I hope that this would work as planned. Mathematics behind the P2 is kinda complicated. Development process continues.

Periapis/Apoapis
This will select witch point to adjust periapis or apoapis. One rule could be that if you are going to lower orbit use periapis and to higher orbit use apoapis.

Pro/Retro-grade
Pro/Retro grade selection allows to select whether the orbit is Pro-grade (inc<90) or Retro-grade (inc>90) orbit. If this mode is incorrectly set the burn time is too high or low. Also time to periapis (PeT) may be useful when figuring out this setting. This will also select witch direction the ship is moving towards the periapis or away from the periapis.

Operating Modes:

Default	This mode will use the same LAN (LoN) as the ship´s current orbit. This is the default setting
Manual	This mode allows manual definition of LoN, If you touch the LoN setting this mode will be activated.
Apsides	Apsides will place the node in to the periapis. So that the line on nodes will matches with the line of apsides. This mode is good in most cases for planet approaches. Plane change is cheap to make at apoapis when the ship is highly elliptical orbit.
Auto LoN	There is a new option the "Auto LoN" that will seek the optimal position for a plane change. This, however may not work in all cases where the inclination is great. Auto LoN will seek the plane change position so that the sum of correction and plane change burns is minimum (optimal case). In most cases the Auto LoN will offer you an orbit where the LoN is at the intersection point. There won't t be a plane change. That's ok when you are targeting the planet it self but there may yet come even greater plane change if you are going to some of the moons. ( experimental feature )

Adjusting values:
After you have selected the Reference and Target. The first thing to do is setting up the Periapis/Apospis mode this will also reset the program. Choose Pro or Retro-grade orbit. After that setup values it is recommended to setup the distance setting first. If you adjust the longitude of periapis in a zone where it is not defined periapis distance is increased automatically. However this won't effect to the value you have set. PeD will also decrease automatically.

Program will be reset to defaults in these conditions:
The target has changed, Reference planet has changed, Periapis/Apoapis - mode is changed. If you wish to reset the program manually toggle Pe/Ap mode.

Program - P3

Latest addition to transfer programs is P3. This is used for a simple transfer calculations such as orbit circulation that is the default mode. This program can be executed at periapis or apoapis only. You can optionally adjust far side distance or set the delta velocity as needed. So this is similar to P1 in some point of view. However it is easier to use.

Program screen of P2:
This is a screen of the transfer program (Left Image). Select value you want to adjust by pressing (Nxt)(Shift-1) button. Adjust with (+,-) (Shift-2,3) and setup value from keyboard by pressing (Set)(Shift-4). (Adj) will change adjusting speed and (Cls) will close the program returning to menu. Press mode button to switch the vector display on. Vector on the screen will guide you to turn the ship to the right direction. Burn calculated by P2 is not a pro-grade but however the burn calculated by P1 is. You should keep the cross at center of the screen during a burn. It may drift a little at the end of burn. You may cut your engines and center it if that is required. (BT) is telling how long to use your main engines at full thrust to enter transfer orbit. When using launch time (Lnc) you must set it with (Set) button after that it can be adjusted by (+,-). (Tra) is the true anomaly of launch position. Also you should note that pressing shift (2,3) from keyboard will adjust values more quickly.

Program Menu
Program menu is shown in right image. (P1) will add new transfer program using mode 1 transfer and (P2) program will use mode 2 transfer and so on. (Edt) allows you to edit the program and (Del) will delete the program. Upper program will be the base for next program. Next program will continue the trajectory from the end point of previous program. When using P2 the reference may be different than in a previous program. But P1 must use the same reference as a previous program. Selected transfer orbit is shown on a map. If the ship (GL-02) is selected current ship orbit is displayed on map.

Program Flags
There is also some program flags indicating whether the orbit is drawn on the map or not (" D "). For an example you may not wish to draw the circulation orbit in to the map but you want to notify it in BT calculations. And there is also a flag indicating what orbit is used for intersection calculations. If the intersection orbit (" I ") is not set the currently selected orbit is used for intersection calculations and orbital data of that orbit is shown on the map. Mode flags are immediately after the program number like "P2DI".

Hypothetical orbit is displayed on map. Both MFDs must be running at the same time. When burn time (BT) is minimum it is good place to engage your engines. If the BT is decreasing you can wait the better launch position. This figure shows that DeltaGlider is approaching the mars how ever the pilot is decided to go lower orbit. Image shows the course correction by decreasing periapis distance and adjusting the longitude of periapis. This correction requires using main engines 18 seconds that makes about 120 kg in fuel. Grey hyperbola is showing the current orbit of the ship and green hyperbola in a new hypothetical transfer orbit. You can also adjust the LAN the place where the plane change will occur. When using this mode target must be set in both MFDs unless you are targeting the reference planet like in a picture above.

Map

Map is a general display for all kind of graphical data. It allows to view entire solar system as well a single target. (Slf) button selects how ship' s orbit is displayed. Available modes are: (1) Ship orbit with plane alignment line, (2) Dot and (3) Disabled. Press (Cnt) button to center the map in a point you want. x=ship, a=apoapis, p=periapis, f=first interception point, s=second interception point or type planet, ship or a station name to center it. Press the Mode button (Shift-M) to toggle between display modes. And those are: None, Orbital / Interception ( shown in a picture below) and Plane change mode.

The white dashed line with the boxes indicates the line where two planes are intersecting. Those planes are Ship´s orbital plane and the other is most often the target plane. If the target is not defined an intersection of Ship´s orbital plane and orbital plane of the Ecliptic is displayed.

Mode flags:

Cur	Indicator informs that only current target and the ship orbit is displayed. Press (Dsp) button to change this mode.
Azo	Indicates usage of auto zoom. Press (Azo) button to switch auto zoom on, it will be deactivated if you touch the zoom buttons (+,-). When you setup new target or reference auto zoom will be activated.
Int	Is indicating that interception mode is active. Press (Int) button to change the interception point and toggle it on/off. (See available modes below)
Soi	Text will appear when the SOI (Sphere of influence) is displayed. The radius of gravity zone within this object is dominant. Press (Soi) button to toggle this mode.
Plt	Informs whether the multi-body trajectory is plotted in a map or not. Toggle with (Plt) button
Low	Warning will be shown if the influence caused by reference object is low.

Special Orbits:

g	Geostationary orbit at equatorial plane (GEO) This works only with the same planets as Aero-brake see below. If the altimeter of GEO is greater than 2 * SOI this will be an equatorial orbit with a radius of 2 planetary radii. Radius vector is pointing to equinox. (Sun's transit). If the reference is illegal this is the same as 'e' below.
e	This is an orbit at Ecliptic plane with a radius of 2 planetary radii. Radius vector pointing to vernal equinox
r	This is an orbit of reference planet with a radius of 2 planetary radii. When the ship is orbiting the moon, this is the plane where moon is orbiting the Earth. The radius vector of this orbit is pointing away from the reference planet (Earth).

Intercept:

1	This is the first intersection point of two, two dimensional, orbits. The node we have been talking about is the third intersection point in three dimensional space. Also target position at the time of intersection must be notified. Intersection line indicates a position where these two orbits has the same radius. However the line may not be at the cross section point of these orbits because the position of cross section depends from where you are looking at it.
2	Second intersection point
Pe	Actually this is not an intersection point. But it works very much the same way. This can be used to calculate target position at the time when the ship is in periapis.
Ap	Same as above for Apoapis.

Projections:

Ecliptic	The Earth's orbital plane around the Sun
Self	Ship´s orbital plane or orbital plane of focused orbit (Transfer)
Target	Orbital plane of target planet or object
Center	Orbital plane of object currently centered ( Map only )
Intersect	Projection for displaying intersections. May not be good when using (Pe,Ap mode) (Map only)
AprOrbit	Approach orbit, Ship´s estimated orbit after maneuver. ( Approach, Aerobrake )

This picture is little old but the new Map is basically the same.

Gray dashed circle is the SOI that we have been talking about.

Inc	Ship's orbit inclination
RIn	Relative inclination between ship and target orbit
PeT	Time to periapis
PeD	Periapis distance
Ecc	Eccentricity of the orbit
TrL	Ship's current true longitude
ApD	Apoapis distance
Tn	Time to node, Time to plane alignment
PeV	Periapis velocity ( planet relative )
TIc	Time to intersect the target orbit
TrI	True longitude of the intersection
HoD	Horizontal ( Planar ) distance between ship and target position at the time of intersection
VeD	Vertical distance ( Orbit normal )
ReV	Target Relative Velocity at intersection point
Tb	Time to burn. Time to plane change
BT	How long to use main engines at full thrust

Approach

This is created for planet approaches. Simply press (Ref) button to setup planet you are approaching. If you want to go to the specific orbit around the target planet. Press (Tgt) button to set it. Then press (Upd) button to update. When update is in progress "Up" text will appear on bottom. Time used for calculations in update is the time to apoapis or periapis depending what you are approaching . Press (Set) button to set the time manually. Select operating mode by pressing (A/R) button. Available modes are (Manual / Auto / Realtime)

Auto mode will use the time specified before and it will update trajectory continuously. It wont change the time when getting closer to target, so hit the (Upd) or (Set) button sometimes.

Realtime mode updates the display in real time but it is less accurate. You must intercept the planet closer than 4 * SOI otherwise "No intercept" text is displayed. Realtime mode will use both 2-body and multi-body calculations.

(Map) button will change the mapping mode (the plot reference). This will effect to the way how the trajectory is drawn on the map. This works only with Manual/Auto mode.

dT	Time stepping for multibody calculations (debug only)
RIn	Relative inclination
Inc	Inclination
CVe	Velocity at circular orbit
LPe	Longitude of periapis
PeD	Periapis distance
PeT	Time to periapis
Tn	Time to node, Time to plane alignment
Soi	Sphere of influence. The radius of gravity zone within this object is dominant.
dV	Required delta velocity for maneuver
Burn	Estimated burn time
PeV	Velocity at periapis ( planet relative )

Multi-Body:

Multi-body calculated trajectory is plotted in the Map ( grey curve ). This is showing how much 2-body calculations and real trajectory may be different. Multi-body calculations can be used to estimate ship captures to planet/moon orbits or even in some gravity assist scenarios. Multi-body calculations requires a lot of CPU power and it may have an impact to frame rate. You can adjust how much power is used for calculations (Cal / Page 2) Also time stepping (Stp / Page 2) can be adjusted that will effect to accuracy. That will also increase maximum plotted distance. From page 2 you can see what bodies are used in calculations and you may set two additional bodies manually. When approaching the Earth you should setup Moon manually as an gravitational body. Also increase stepping (Stp) when calculating long distances Earth->Mars or Jupiter. Stepping can be from 1 to 10

Multi-body trajectory can be updated by pressing (Upd) button. Automatic update can be enabled from (A/R). "Short range" text will appear if the multi-body trajectory can not reach the periapis. It may also appear if the periapis distance is very small. ( 100m ). Trajectory time can be set manually by pressing (Set) button. You can interrupt update by pressing (Upd) button again. "Up" text is shown when the update is in progress.

When approaching Luna-OB1, it is possible to use gravity assist to enter the orbit having inclination close to station's inclination.

Aero-brake

Setup reference by pressing (Ref)-button ( the planet you are approaching ). (Prs) is the "surface" pressure in Pascals. And (Dns) is the "surface" density. Press (Att)-button to change the attitude mode and it must match with the ship.

There is "dV" that will tell how much velocity the ship will lose during the brake. And there is also G-force indicator that will show the maximum G-force during the brake. There is a minimum altitude during aerobrake "Pe Alt" , time to periapis "Pe Time" and periapis velocity "Pe Vel" (air-speed). "Ecc" is an eccentricity of orbit after the aerobrake. "Ap Dist." is apoapis distance after aerobrake. Be sure you have turned the ship in correct attitude when the aero-brake begins other wise it will fail. If you notice that you are going to brake too much you can abort the brake by turning the ship Pro-grade. That will decrease the drag much. "Re-Entry" - text will appear if the ship is not going to stay on orbit. Grey line indicates the position where the altitude is minimum or the surface contact position. Time to periapis must be lower than 20ks to be able to use this.

Warning: There is some hardcoded data in aerobrake program and it can be used only with the planets listed below except Pluto. Hopefully orbiter api supports the access to planetary data later in future. Also note that atmospheres must be correctly defined in configuration files. "Alt (12Pa)" is the altitude where the aerobrake usual happens.

Thanks to Hot Dog for a help with this data.

AtmAltLimit:
Limit = -Pressure / ( Gravity * Density ) * ln( 8e-11 / Density )

Altitude, having a pressure of x Pascals:
Alt( x ) = -Pressure / ( Gravity * Density ) * ln( x / Pressure )

Pressure and density at altitude "alt". This, of course, does not notify the temperature changements in atmosphere.
Prs( alt ) = Pressure * exp( alt * Gravity * Density / Pressure )
Dns( alt ) = Density * exp( alt * Gravity * Density / Pressure )

Problems:
If the estimated trajectory starts to change with great speed when the ship is close to periapis. The ship is not actually braking the amount that the MFD expects it to brake. That may be caused by many different variables. AtmAltLimit, Pressure/Density settings in MFD/cfg-file. The settings must match between MFD and cfg-file. Also incorrect attitude (navmode) will cause this failure.

Orbital

Orbital program is a collection of few minor programs for orbital maneuvers. Circulate simply circulates the orbit it can be executed at any point in a orbit. Other programs requires the target. Find Target, Velocity Match, Orbit Match that is planned to be executed in a point where two orbits intersects and it is designed to be used with orbit sync. MFD After the burn ships orbit will match with the target orbit. Find Target can be used to find targets when they are out of visual range or if they are too dark to being seen. Velocity match is for final approach to station or very small moon. Usual the ship´s HUD will offer the same program.

Plane change
Latest addition to orbital programs is a Plane change. That can be executed in highly elliptical orbits where traditional method fails. Also the burn time required by this mode is little less. After engaging engines plane change will be locked to the velocity being targeted. Press (PlC) button to unlock after the plane change is completed. This burn will temporary decrease periapis distance so if you abort the burn be careful that you don't hit the planet..

A plane change vector used in this program is simply calculated ( n1 + n2 ) * dV / length ( n1 + n2 ), where n1,n2 are normal vectors and dV is required dV for the plane change.