Kerbal Space Program

ligh cyan: current orbit
yellow: target orbit
yellow dotted: predicted orbit
purple: sphere of inference, where maneuver can be added for sling-shot, fly-by or orbiting
Kerbal Space Program - Tutorial For Beginners - Interplanetary Transfers - YouTube

periapsis: highest speed, lowest orbit
apoapsis: lowest speed, highest orbit (most fuel efficient to change orbit)
inclination change is more efficient at lower speed

Kerbal Space Program - Tutorial For Beginners - Interplanetary Transfers - YouTube
Kerbal Space Program - Interplanetary Transfer Tutorial Engineering Style - YouTube

Advanced Maneuver Mode in Kerbal Space Program 1.7 - YouTube

Transfer Window Planner by TriggerAu
Transfer Window Planner on SpaceDock
[1.7.x] Transfer Window Planner v1.7.1.0 (August 19) - Add-on Releases - Kerbal Space Program Forums

KSP Mods - Maneuver Node Evolved - YouTube
Maneuver Node Evolved on SpaceDock

[1.8.x] Precise Maneuver editor - Add-on Releases - Kerbal Space Program Forums

Precise Node Continued on SpaceDock

Orbiting

also called "circularize"

Kerbal Space Program - Career Mode Guide For Beginners - Part 5 - YouTube
Kerbal Space Program - Career Mode Guide For Beginners - Part 10 - YouTube Launch a Satellite Into a Specific Orbit

Oberth effect - Wikiwand firing rocket engine at high speed causes greater change in kinetic energy than when fired at low speed
Exploiting The Oberth Effect (again) in Kerbal Space Program - YouTube

How Gravity Assists Work - YouTube
Kerbal Space Program - Using Gravity Assists To Save Fuel - YouTube
Visiting All Kerbal Planets Using Gravity Assists - Kerbal Space Program 1.7 - YouTube

Intercept
Elliptical Orbit to SOI Edge
Low Orbit

Figures are for Kerbin only

points 45 degree to the East at altitude of 10km
check apoapsis (highest point) in map, keep time to apoapsis increasing
if using 2 stage, deploy second stage at altitude of ~20km
when apoapsis reach 70km and add maneuver
accelerate along apoapsis to make target orbit to orbit the earth (Orbit Insertion)
make sure periapsis (lowest point) > 70km
point vehicle to blue maneuver vector
wrap to maneuver and control throttle according to maneuver
split the burn time to two halves around the maneuver time

Deorbiting

Kerbal Space Program - Career Mode Guide For Beginners - Part 6 - YouTube

Figures are for Kerbin only

Orbit Insertion

create maneuver to the orbit with the lowest periapsis
create maneuver opposite to desired landing site
accelerate retrograde to decrease periapsis to just above the atmosphere (35km)
entering Kerbin's atmosphere will be safe with parachute

Descending

Figures are for Kerbin only

wait until speed is < 300m/s
deploy parachute (should be above 1000m)

[1.5.1, 1.3.1] Trajectories v2.2.1 (2018-04-28) : atmospheric predictions - Add-on Releases - Kerbal Space Program Forums stock trajectories does not account for atmospheric drag and planetary rotation
KSP Easy Mods Episode 8 - Trajectories - YouTube
KSP Mod Overview: Trajectories - YouTube

Delta-V

Kerbal Engineer Redux - Mods - Kerbal Space Program - CurseForge
[1.3.0] Kerbal Engineer Redux 1.1.3.0 (2017-05-28) - Add-on Releases - Kerbal Space Program Forums shows Delta-V maps
Releases · jrbudda/KerbalEngineer latest release
KSP Easy Mods Episode 11 - Kerbal Engineer Redux - YouTube
KSP Mod Overview: Kerbal Engineer Redux - YouTube

Cheat sheet - Kerbal Space Program Wiki Delta-V maps
[1.7.3] Community Delta-V Map 2.7 - Tutorials - Kerbal Space Program Forums

Docking

use lower orbit to catchup, higher orbit to retrograde
use maneuver to reach within 0.3km of target
https://youtu.be/lg3iOKAOJ-A?t=671, select port as target on both vehicle and let SAS does its job

Docking Port Alignment Indicator on SpaceDock
[1.8.1] Docking Port Alignment Indicator (Version 6.8.5 - Updated 12/14/19) - Add-on Releases - Kerbal Space Program Forums

KSP Easy Mods Episode 7 - Navball Docking Alignment Indicator & Docking Sounds - YouTube

Mods

CKAN (The Comprehensive Kerbal Archive Network) - v1.30.4 Hubble - Add-on Releases - Kerbal Space Program Forums
User guide · KSP-CKAN/CKAN Wiki

[1.8.x-1.10.x] Module Manager 4.1.4 (July 7th 2020) - Locked inside edition - Add-on Releases - Kerbal Space Program Forums
[1.3.0] Community Database of Module Manager Patches for Stock KSP - Add-on Releases - Kerbal Space Program Forums
sarbian/ModuleManager

Kerbal Space Program Tutorial - How To Install Mods - YouTube
KSP/GameData/ will be unioned to KSP/

SpaceDock > KSP
Mods - Kerbal Space Program - CurseForge
Steam Community :: Kerbal Space Program

Kerbal Space Program: BASIC MODDING! - YouTube
KSP Easy Mods - YouTube
Kerbal Space Program - Guide To The 10 Most Essential Mods & Add Ons - YouTube
The Best Mods For Kerbal Space Program - Part 2 - Presentation Improvements - YouTube
9 Kerbal Space Program Mods I Can't Live Without AND Duna Tutorial - YouTube
Kerbal Space Program Mods - YouTube
The Best Kerbal Space Program Mods | PC Gamer

Near Future Spaceprogram on SpaceDock collection

PersistentThrust + SolarSailNavigator (necessary for low thrust engines)
Katniss's Cape Canaveral (LC-39A/B and surrounding area)
Minimum Ambient Lighting
StageRecovery (recovery money)
Waypoint Manager
HyperEdit teleportation, orbit and vehicle testing
KSP Easy Mods Episode 12 - Kerbal Alarm Clock - YouTube alarm added in 1.12, but mods may require this mod

Tracking Station Evolved on SpaceDock
[1.9.x] Haystack ReContinued - Add-on Releases - Kerbal Space Program Forums

[1.8.1-1.10.1] Realism Overhaul v13.1.1 [29 Jun 2021] - Add-on Releases - Kerbal Space Program Forums hard mode

Development

Add-on Development - Kerbal Space Program Forums

Auto Pilot

kOS: Kerbal Operating System terminal, programming language
KSP-KOS/KSLib: The standard library and examples for the Kerboscript language

KSP Mod Overview: GravityTurn - YouTube automate take offs

MechJeb2 - Mods - Kerbal Space Program - CurseForge auto pilot, trajectory prediction (togglable)
Kerbal Space Program - Guide To MechJeb 2.0 - Apollo 人大卜卜 Style Mun Mission - YouTube

Pilot Assistant (useful for time wrap)

Camera

Camera Focus Change (use O use any point as camera focus)
Hullcam VDS Continued (use -/= to cycle through camera, bksp to reset, good for take offs)
Camera Tolls continued

Science

[1.9.x] ScienceAlert ReAlerted : Experiment availability, now with DMagic support - Add-on Releases - Kerbal Space Program Forums

SCANsat on SpaceDock

DMagic Orbital Science on SpaceDock

Crafts/Parts

KerbalX - KSP Craft Sharing Simplified
Crafts - Kerbal Space Program - Steam Workshop
Craft Kitchen - Kerbaltek

[1.11.x] Near Future Technologies (All1.11.x) - Add-on Releases - Kerbal Space Program Forums

K2 Command Pod
Near Future Construction (structural parts)
Near Future Propulsion (VASIMR® Engine)
Near Future Electrical (Nuclear Reactor)
Interstellar Extended (Hydrogen Fuel tanks and radiators)
SSTU (Orion capsule used in the lander)
Habitat pack
Stockalike Station Parts Expansion Redux (Habitation modules)
Tundra Exploration (Starship, plumes to be released soon)
Planetside Exploration Technologies on SpaceDock Rover
M.O.L.E. on SpaceDock
Deep Space Surface Habitat Unit Pack on SpaceDock
Kerbal Planetary Base Systems on SpaceDock
KerbalX - USI Exploration Pack
[1.11.x] USI Exploration Pack - Small parts, big adventure! [v 0.6.0] - Add-on Releases - Kerbal Space Program Forums
Releases · KSP-RO/FASA-RO NASA's Apollo Mission crafts
[DEV HALTED][1.3] CxAerospace: Stations Parts Pack v1.6.2 [2017-5-24] - Add-on Releases - Kerbal Space Program Forums

Bluedog Design Bureau (BDB): USA historical parts.
Tantares: Russian historical parts.
Knes: European historical parts, plus many conceptual parts that never flew.
Near Future: this is a collection of mods, not just one. It adds a flexible set of parts that encourage your own unique designs. Also looks for other mods by the same author (Nertea) that have a similar integrated art style.

KSP Easy Mods Episode 14 - Kerbal Inventory System & Kerbal Attachment System - YouTube EVA construction added in 1.11
[1.8.1] Kerbal Konstructs - 1.8.1.15 - 15.Dec.2019 - Add-on Releases - Kerbal Space Program Forums

Kerbas-ad-astra/KronalVesselViewer: For capturing orthographic and offset views of spacecraft in KSP.
KSP Mods - Kronal Vessel Viewer - YouTube "schematic" view of your craft

Real Scale Boosters on SpaceDock
To be used with Real Solar System