However, through the playful and still complex approach of Kerbal Space Program KSP - it is an awesome game I totally recommend to anybody remotely interested in space exploration - I picked up interest lately again and started reading into orbital mechanics, propulsion systems and related stuff in more detail.

This blog series is dedicated to summarising basic concepts at definitely super simplified and probably sometimes oversimplified and not entirely correct level. The easiest concept for me to grasp, since once can do it quite interactively in KSP is the concept of orbits and orbital changes through orbital maneuvers.

So this very first post of this series will cover my basic understanding of the concept of orbits. In mathematical terms, an ellipse is a plane curve surrounding two focal points andsuch that for all points on the curve, the sum of the two distances is constant. It is a generalization of a circle, where the two focal points are the same.

Yes, also circular orbits exist. There are a few important parameters describing an ellipse which will be referred throughout this blog series, so make sure you memorize and understand them, because they will keep popping up again and again. The length of the chord through one of the foci, perpendicular to the major axis, is called the latus rectum. One half of it is the semi-latus rectum. A calculation shows:. The semi-latus rectum is equal to the radius of curvature of the osculating circles at the vertices.

In physics, an orbit is the gravitationally curved trajectory of an object, like the the trajectory of any plane around a star or a satellite around earth. Unless mentioned differently, in this blogpost orbit refers to a regularly repeating trajectory, but there are also non-repeating trajectories. The post will stick to the classical Newtonian mechanics paradigm of describing orbital motion, which is an adequate approximation for most situations.

This principal is illustrated by the illustration above, where gravity from a massive body in the center green pulls a object travelling on a straight path pink object, black arrowseffectively bending the path with its constant pull red around the center body. Here, we visualize a cannon on top of a very high mountain which can fire at any imaginable speed. If the cannon fires its ball with a low initial speed, the trajectory of the ball curves downward and hits the ground A.

As the firing speed is increased, the cannonball hits the ground farther B away from the cannon, because while the ball is still falling towards the ground, the ground is increasingly curving away from it see first point, above. If the cannonball is fired with sufficient speed, the ground curves away from the ball at least as much as the ball falls â€” so the ball never strikes the ground.

It is now in what could be called a non-interrupted, or circumnavigating, orbit. As the firing speed is increased beyond this, non-interrupted elliptic orbits are produced; one is shown in D.

## Orbital basics

If the initial firing is above the surface of the Earth as shown, there will also be non-interrupted elliptical orbits at slower firing speed; these will come closest to the Earth at the point half an orbit beyond, and directly opposite the firing point, below the circular orbit.

At a specific horizontal firing speed called escape velocity, dependent on the mass of the planet, an open orbit E is achieved that has a parabolic path. At even greater speeds the object will follow a range of hyperbolic trajectories. The first two terms I learned about in KSP were the two apsis - probably because a lot of orbital maneuvers happen at those and they are pretty simple to comprehend. Apsis denotes either of the two extreme points i.This mod is not known to work with the latest version of Kerbal Space Program.

Proceed with caution. Hello everyone, Whitecat here creator of the Historic Missions Contract Pack and I wish to share with you the release version of my new project. I have been working on this for quite a while and can now release this mod after I finally had a break through in the code - as a result of months of tinkering!

Some mods in the past have come so close to this but none actually produced a viable working version This is the release version of 1. This version contains all of the features of 1.

## Interactive illustrated interplanetary guide and calculator for KSP

For the RAV, download version 1. Adjusted Decay Formulas Made way for Realistic Formulas Fixed a multitude of bugs here and there Finally fixed the black screen on load bug Added Planetarium Tracking option Can cause lag with 32 bit games and high vessel counts. Export Downloads. Export Followers. Export Referrals. Raw stats are from the beginning of time until now.

Each follower and download entry represents one hour of data. Uneventful hours are omitted. You'll get emailed updates for this mod. Game Version: 1. Downloads: 20, Author: Whitecat Mod Website: Forum Thread. Support this mod: Donate. Followers: Information Changelog Stats. What does it do? Supports all resource types and engines. Version 1.

Save a copy of the VesselData. Stats for Orbital Decay Downloads over time New followers per day.

Top Referrers spacedock. Want us to email you when it updates? Not now. Not ever. Remember Me.Home Discussions Workshop Market Broadcasts.

Change language. Install Steam. Store Page. Kerbal Space Program Store Page. It is only visible to you. If you believe your item has been removed by mistake, please contact Steam Support. This item is incompatible with Kerbal Space Program. Please see the instructions page for reasons why this item might not work within Kerbal Space Program.

This item will only be visible to you, admins, and anyone marked as a creator. This item will only be visible in searches to you, your friends, and admins. Put yourself in any Orbit Automatically with the Debug Menu.

Your Votes count and help keep the Guide in Circulation so other Players may find it more easily, Thank you very Much! Feel free to share links to this Cheat Sheet. Just some simple discriptions, value ranges, and some example pictures. I had gone through and written all this information down in a small note book, primarily for the SMA Values. Then I realized it might be helpful to others as well. So here it is with some extra KSP pics to put it into context.

I hope it is useful and helps anyone. This item has been added to your Favorites. Created by. Guide Index. Gilly Moon. Ike Moon. Laythe Moon. Vall Moon.Simply download the latest version from the SpaceDock: Here.

Install the contents of the Orbital Decay x. Keep up to date with development changes and bug alerts by checking the release forum: Here.

The four modeled types are:. Atmospheric Drag effects only the Semi Major Axis and Eccentricity, and therefore altitude and speed, of an orbiting vessel. The drag is greatest at low altitude orbits around planets with a dense atmosphere. This form of drag is also dependent on the Mass and Area of a vessel, and also the conditions of the solar system over a year cycle, such as Solar Radio Flux F The following equations define atmospheric drag on a satellite of Mass M KgArea AOrbiting Body b at altitude h Km with semi major axis a and orbital period Pwith solar flux F Thus decay rates from this can be as lower than 1mm per year.

This effect is one of the hardest to model in KSP since vessel objects on rails do not spin, similarly rotation axes are only calculated for an active vessel and albedo and other characteristics of satellites cannot be directly calculated since the composition and thermal properties of the object are not known. For the moment this is limited to estimations and approximations using real world analogues.

Hopefully compatibility with Persistent Rotation can be established and a more accurate model can be obtained. This perturbation is based on Mass concentrations on a planetary surface, on every body in the solar system, mass is never evenly distributed across the near spherical surfaces, for example, on the moon Mass concentrations Mascons cause orbits to bend and alter as the acceleration experienced by a satellite varies; causing changes in Inclination, Eccentricity, Semi Major Axis and position nodes.

The effects can vary in magnitude and can be devastating for low orbiting vessels, Mascons are the main cause of satellite decay around non atmospheric bodies.

The later Apollo missions released a multitude of small satellites to study the effect in greater detail across the 's. These changes are modeled on a planet by planet basis, currently only for Kerbin, Mun, Earth and Moon. The equations are quite complex and cannot be correctly described in this wiki however this Nasa Technical Report described the full effect and calculations can be derived from this.

The User Interface is a part of the stock toolbar and can be accessed by clicking on the 'cat' icon. Every controllable vessel has the ability to station keep, if the vessel has an ignited engine or RCS block and enough fuel. Once activated the fuel will drain based on the current decay rate and efficiency of the engines, station keeping will automatically be disabled if the station keeping fuel runs out.

The station keeping engine and resource can be set with the right click menu on the command module of the vessel in question. For optimum orbital lifetime a vessel should be beyond 2x the radius of the body it is orbiting, have a high mass and have a low surface area; or have plenty of station keeping fuel!

Skip to content. Orbital Decay Jump to bottom. Gravitational Perturbation This perturbation is based on Mass concentrations on a planetary surface, on every body in the solar system, mass is never evenly distributed across the near spherical surfaces, for example, on the moon Mass concentrations Mascons cause orbits to bend and alter as the acceleration experienced by a satellite varies; causing changes in Inclination, Eccentricity, Semi Major Axis and position nodes.

Station Keeping Every controllable vessel has the ability to station keep, if the vessel has an ignited engine or RCS block and enough fuel. Pages 1. You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window.The orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle.

A value of 0 is a circular orbit, values between 0 and 1 form an elliptic orbit1 is a parabolic escape orbitand greater than 1 is a hyperbola. The term derives its name from the parameters of conic sectionsas every Kepler orbit is a conic section.

It is normally used for the isolated two-body problembut extensions exist for objects following a Klemperer rosette orbit through the galaxy. In a two-body problem with inverse-square-law force, every orbit is a Kepler orbit. The eccentricity of this Kepler orbit is a non-negative number that defines its shape.

For values of e from 0 to 1 the orbit's shape is an increasingly elongated or flatter ellipse; for values of e from 1 to infinity the orbit is a hyperbola branch making a total turn of 2 arccsc edecreasing from to 0 degrees.

The limit case between an ellipse and a hyperbola, when e equals 1, is parabola. Radial trajectories are classified as elliptic, parabolic, or hyperbolic based on the energy of the orbit, not the eccentricity. Radial orbits have zero angular momentum and hence eccentricity equal to one. Keeping the energy constant and reducing the angular momentum, elliptic, parabolic, and hyperbolic orbits each tend to the corresponding type of radial trajectory while e tends to 1 or in the parabolic case, remains 1.

For a repulsive force only the hyperbolic trajectory, including the radial version, is applicable. Next, tilt any circular object such as a coffee mug viewed from the top by that angle and the apparent ellipse projected to your eye will be of that same eccentricity.

The eccentricity of an orbit can be calculated from the orbital state vectors as the magnitude of the eccentricity vector :. The eccentricity of an elliptical orbit can also be used to obtain the ratio of the periapsis to the apoapsis :. The eccentricity of the Earth 's orbit is currently about 0.

Venus and Neptune have even lower eccentricities. Over hundreds of thousands of years, the eccentricity of the Earth's orbit varies from nearly 0. The table lists the values for all planets and dwarf planets, and selected asteroids, comets, and moons.

Such eccentricity is sufficient for Mercury to receive twice as much solar irradiation at perihelion compared to aphelion. Other Trans-Neptunian objects have significant eccentricity, notably the dwarf planet Eris 0.

Even further out, Sednahas an extremely high eccentricity of 0. Most of the Solar System's asteroids have orbital eccentricities between 0 and 0. The Moon 's value is 0. Neptune 's largest moon Triton has an eccentricity of 1.

However, smaller moons, particularly irregular moonscan have significant eccentricity, such as Neptune's third largest moon Nereid 0. Comets have very different values of eccentricity.

Periodic comets have eccentricities mostly between 0. Non-periodic comets follow near- parabolic orbits and thus have eccentricities even closer to 1. Examples include Comet Haleâ€”Bopp with a value of 0. Its orbital eccentricity of 1. It was discovered 0.

It has an interstellar speed velocity at infinity of The mean eccentricity of an object is the average eccentricity as a result of perturbations over a given time period. Neptune currently has an instant current epoch eccentricity of 0. Orbital mechanics require that the duration of the seasons be proportional to the area of the Earth's orbit swept between the solstices and equinoxesso when the orbital eccentricity is extreme, the seasons that occur on the far side of the orbit aphelion can be substantially longer in duration.

Today, northern hemisphere fall and winter occur at closest approach perihelionwhen the earth is moving at its maximum velocityâ€”while the opposite occurs in the southern hemisphere.

**KSP Maths #2: Inclination, ascending/descending nodes**

As a result, in the northern hemisphere, fall and winter are slightly shorter than spring and summerâ€”but in global terms this is balanced with them being longer below the equator.Variables of type Orbit hold descriptive information about the elliptical shape of a predicted orbit.

Whenever there are multiple patches of orbit ellipses strung together, for example, when an encounter with a body is expected to alter the path, or when a maneuver node is planned, then each individual patch of the path is represented by one Orbit object. This could be useful when you want to be able to get information about a hypothetical orbit that an object may someday end up in, even when its not in that orbit now.

One case where this may be useful is when trying to place a satellite into a desired final orbit say to fufill a contract. You may wish to see some information about that destination orbit even though no particular objects are in that orbit at the moment.

You pass in the Keplerian parameters that define the orbit which are typically the values you will see on a contract parameter for putting satellites into desired orbitsand the orbit object you make can then be queried for things like its apoapsis, periapsis, etc. As much as possible we have tried to present everything in kOS as degrees for consistency, but some of these may have slipped through.

If you see any of these being reported in radians, please make a bug report. Even though orbital parameters are traditionally done in radians, in keeping with the kOS standard of making everything into degrees, they are given as degrees by kOS.

If the orbit is closed, then this value will be in the range [ But if the orbit is open, then this value will be in the range The difference is because it does not make sense to speak of the orbit looping all the way around degrees in the case of an open orbit where it does not come back down. Note that the above switch between Both conditions look similar on the game map so it may be hard to tell them apart without actually querying the eccentricity to find out which it is.

Kerbal Space Program uses this internally to track orbit positions while under time warp without using the full physics system. Describes the way in which this orbit will end and become a different orbit, with a value taken from this list. The current velocity of whatever the object is that is in this orbit. Be aware that this is not just a velocity vector, but a structure containing both the orbital and surface velocity vectors as a pair.

See OrbitableVelocity. When this orbit has a transition to another orbit coming up, this suffix returns the next Orbit patch after this one. The number of patches into the future that you can peek depends on your conic patches setting in your Kerbal Space Program Settings.

When this orbit has a transition to another orbit coming up, this suffix returns the eta to that transition. The number of patches depends on your conic patches setting in your Kerbal Space Program Settings.

List of Orbit Objects. Deprecated since version 0. The epoch timestamp seems to change when you go on or off from time warp.

It this orbit is the orbit that will remain forever. Scalar m. Scalar s. Scalar deg. Next Orbit.Eve is the second planet from Kerbol and is the second largest body orbiting it. It is purple in appearance. It has one small moon, a captured asteroid called Gilly. Eve seems to be the real life analougue of Venus. Eve is the closest planet to Kerbin and the potentially the easiest to reach, requiring the least delta-v of any planet.

### On the dynamical stability of Principia's modified Jool system

However, a slight inclination relative to Kerbin makes encounters slightly harder. Having a similar size to Kerbin gives it a large gravity well. The result is that it requires the most delta-v of any celestial body with a solid surface to escape from it. Its thick atmosphere much thicker than Kerbin makes aerocaptures and landings easy, but makes a start from sea level even harder because most fuel will be wasted on overcoming atmospheric friction.

The combination of high gravity and thick atmosphere makes return missions from the sea level of Eve very difficult. Eve has several oceans and large, flat continents with a few mountain peaks. The composition of the liquid which fills the oceans and lakes is unknown, but it is unlikely to be water because the boiling point of water is slightly below the surface temperature, even when taking the high atmospheric pressure into account.

According to the devs during a livestream, it was joked that the lakes were made of rocket fuel. The land masses look like purple sand dunes. Its tallest point is m above sea level and is just south of the equator, at 1. Eve's atmosphere begins at 96, Its atmospheric pressure fades exponentially, with a scale height of m.

The atmosphere should be superheated due to the thick atmosphere trapping in heat, much like Venus. From within Eve's atmosphere, the sky appears indigo during nighttime. During dawn and dusk, the sky is green. The atmosphere is possibly composed of iodine, given its purple coloration.

Jet engines do not function in Eve's atmosphere, since it contains no oxygen â€” they make noise and consume fuel, but they produce no thrust. Planes with other propulsion methods do however work very well in Eves atmosphere and are a great way to explore the planet. Try to stay on a height between 35 km and 25 km where the atmosphere generates enough lift to glide and steer, but not so much drag that it slows you down too much. As with version 0.

The following table gives terminal velocities at different Eve altitudes. These are also the velocities at which a ship should travel for a fuel-optimal ascent from Eve, given the game's model of atmospheric drag. Eve's only natural satellite is the tiny captured asteroid Gilly in a highly eccentric and inclined orbit.

Gilly is currently the smallest celestial body in the Kerbol system. A synchronous orbit of Eve requires an altitude of Sign In Don't have an account? Start a Wiki.

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