What is Orbital dynamics: Definition and 30 Discussions

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. The motion of these objects is usually calculated from Newton's laws of motion and law of universal gravitation. Orbital mechanics is a core discipline within space-mission design and control.
Celestial mechanics treats more broadly the orbital dynamics of systems under the influence of gravity, including both spacecraft and natural astronomical bodies such as star systems, planets, moons, and comets. Orbital mechanics focuses on spacecraft trajectories, including orbital maneuvers, orbital plane changes, and interplanetary transfers, and is used by mission planners to predict the results of propulsive maneuvers.
General relativity is a more exact theory than Newton's laws for calculating orbits, and is sometimes necessary for greater accuracy or in high-gravity situations (e.g. orbits near the Sun).

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  1. J

    I Plotting the orbits of the planets from Ephemeris data

    I would like to plot the position of planets around the Sun for different dates and describe their orbits. I got the Ephemeris data for each planet from the JPL Horizons System, I got: Date__(UT)__HR:MN R.A.___(ICRF)___DEC Ang-diam ObsSub-LON ObsSub-LAT ObsEcLon ObsEcLat however...
  2. L

    A satellite in orbit in a system with one planet and two moons

    1) Considering the forces on one of the moons, I have: ##\frac{GMm}{(10R)^2}+\frac{Gm^2}{(20R)^2}=m\frac{v^2}{10R}\Leftrightarrow v=\sqrt{\frac{G}{10R}(M+\frac{m}{4})}.## 2) Considering the initial situation in which the satellite is at rest on the surface of the planet...
  3. cianfa72

    I About the relation between number of sidereal and solar days

    Hi all, I've a doubt about the following formula for the number of sidereal vs solar days for a generic planet orbit (e.g. the Earth's orbit around the Sun): $$N_{sid} = N_{sol} + 1$$ Section 1.5 of the book "Foundation of Astrophysics" - B. Ryden shows how to calculate the above equation...
  4. B

    B How long it takes the Earth to fall halfway to the Sun--ellipse method

    There's a classic physics problem that is: If Earth is orbiting the Sun at 1 au from and is suddenly stopped. How long does it take to fall into the Sun (neglecting the size of the Sun/Earth)? I know that a clever way to solve this problem is by using degenerate ellipses and an object...
  5. E

    Orbital dynamics math review for a computer simulation

    The program begins by prompting the user to input the initial angle and speed. Once these values have been input, the program calculates the initial velocity components for the asteroid in two dimensions. printf("Input an initial angle from 10 to 80 degrees\n"); scanf("%f", &theta)...
  6. F

    A Calculating Orbital Trajectories for Spaceflight Simulators

    Hi! Basically I am developing a spaceflight simulator specifically for the space shuttle. Coding the Shuttles Systems etc. is not actually the hardest part, as I had thought before. The real problem is the physics engine :confused: The main problem I have is, that with all the Equations for...
  7. M

    On the convergence of the three body disturbing function

    For the three-body-disturbing function expanded in multipolar orders with respect to the ratio of the semi major axes, the function converges for small ratios, how to check the convergence for a certain set of parameters? I'm using the work of the Laskar in his paper "Explicit expansion of the...
  8. F

    Extract anomalies from two-line element set (TLE) on ISS

    Homework Statement I am faced to a problem of interpretation illustrated on figure below : I must precise that I talk about **mean anomaly**. Homework Equations for the 2 questions, I am asked to find : 1) at which anomaly is the ISS at the two lines epoch ? 2) at wchich anomaly is the...
  9. H

    B Feasibility of a L1 Gravity Swing Cold Launch?

    At an L1 LaGrangian point between two bodies, one could - materials science notwithstanding - pit two of Newton's Laws (LM3,UG) against each other to provide thruster-free stationkeeping. Would it be feasible to use that to launch free from the system ? either spit out like a watermelon seed...
  10. Russell Patterson

    I Do orbital dynamics scale linearly?

    I need to scale my solar system model and it's not working. I'm making an augmented reality app that shows a sample solar system rotating. It works great! (Thanks to this $7 program https://assetstore.unity.com/packages/tools/physics/gravity-and-orbits-solar-system-105300 . The Unity engine...
  11. L

    Maple Computational Hohmann Transfer on MapleSoft

    Hi, I am trying to recreate an Interplanetary Hohmann transfer orbit from Earth to Mars similar to image A below (the red line). However, Earths orbit is not circular, It is more of an elliptical orbit rather than circular. I was able to successfully plot the orbits of both Earth and Mars...
  12. rcgldr

    Astronaut shoots a bullet into the sun - gravity assists?

    This question came up at another forum. The delta-v of potential guns is limited to the range 3 km/s to 11 km/s (hydrogen gun). Assume the astronaut is either on the moon or orbiting the moon. I'm wondering if a single impulse followed by gravity assists (and ideal planet alignment) could result...
  13. M

    Newtonian energy integral and suitable boundary conditions

    I have a (somewhat) strange energy equation which has the following form: KE = A + B W + C \exp(-D W), where A,B,D are known constant, C is an unknown constant to be determined and kinetic and potential energy are given by KE and W respectively with W\equiv W(r) i.e. is a function of...
  14. P

    I The Sun's habitable zone and orbital resonaces/stability

    Let's say there's five Mars/Earth massed planets orbiting a star like the sun between 0.6 AU and 2 AU, what orbital resonance configuration can they be into ensure maximum stability? Would adding gas giants to the system enhance stability?
  15. S

    I Can a planet have multiple large moons?

    I thought that I'd posted this here, but perhaps not. I've had it on the OtherWorlds and the Physics stackexchange with no results. I grew up with countless alien planet covers depicting 2-3 moons all considerably larger (telephoto lens...) than Luna's appearance from earth. Luna from Earth...
  16. J

    A Series of Exoplanets in Our Solar System

    In this alternate universe, Earth is the same as back home--8,000 miles wide, 25,000 around, six sextillion tons, orbiting a G-type main-sequence star from a distance of 93 million miles. But here, the similarities end. MOON DIAMETER--3,273 miles MASS--0.025x that of Earth DISTANCE FROM...
  17. J

    B E=0. What Does That Mean for the Seasons?

    Currently, Earth's eccentricity (orbital shape) is 0.0167086. Zero is a perfect circle whereas One is parabolic escape orbit and any greater becomes a hyperbola. And in the theory of the Milankovitch cycles, Earth's eccentricity varies between 0.000055 and 0.0679 over a period of 100,000 years...
  18. xpell

    B When are we "trailing" the Sun in its galactic revolution?

    Hi! I guess this question must be easy, but it's driving me crazy: in what time of the year does the Earth "trails" the Sun in its current galactic movement towards Vega? And, could you please confirm that during this period Vega is not visible because it's always facing the "day side" of the...
  19. I

    What are J2 perturbations and how do they affect satellite orbits?

    Homework Statement Hi! I am trying to solve a problem where I need to calculate a satellite's orbit, but first I would like to ask for some clarifications from someone here that might know this stuff. I need to design an orbit so that no maneuvers (one part of the problem) are necessary to...
  20. I

    Is the Analysis of the Space Shuttle's Orbit Correct?

    Homework Statement Hi, I have a textbook problem from a course that I need help with Question: You’ve just completed an analysis of where the Space Shuttle must be when it performs a critical maneuver. You know the shuttle is in a circular prograde orbit and has a position vector of...
  21. M

    A Need help with satellite navigation? Any textbook recommendations?

    Hey guys, looking to get some advice on satellite navigation. Can anyone recommend a nice textbook covering Newton, Kepler, Lagrange etc and their contributions to orbital motion. Also any textbooks on MATLAB or Maple examples of orbits - relativistic or Newtonian it doesn't matter. Not put off...
  22. A

    I Seeking "simple" orbital path planning for game development

    Hi PhysicsForums! I'm a game developer planning a project involving simplified, idealized orbital mechanics. I made this reddit post which did not generate the sort of response I was hoping for, but it summarizes my issue in greater detail for anyone curious...
  23. J

    I Spacecraft Launches: Perigee & Apogee - Why Terminate?

    why spacecraft launches are usually terminated at either perigee or apogee?
  24. Odious Suspect

    Deriving this "familiar arccosine form" of integral

    I posted a question about this yesterday, but realized I had made a stupid mistake in my derivation. Orbital dynamics: "The familiar arc-cosine form" That error has been corrected. I still have a deeper question. I believe this expression can be developed using the geometry of an ellipse in...
  25. Odious Suspect

    Orbital dynamics: "The familiar arc-cosine form"

    This arises in Joos's discussion of planetary motion, at the following URL: https://books.google.com/books?id=wFl2MkpcY6kC&lpg=PP1&pg=PA91#v=onepage&q&f=false I've modified the notation in obvious ways. He asserts that the following expression is "the familiar arc-cosine form": $$-\int...
  26. K

    Need assistance with orbital dynamics questions

    Hello, I am currently writing a novel and there are quite a few situations that I would like to create that involve orbital dynamics. I would like to be as realistic as possible. I am seeking a knowledgeable person that can ballpark these problems. I do not think that it would take to much of...
  27. A

    Gaining Understanding Orbital Dynamics & N-Body Simulation

    Hello. I have a project in school in which I will be attempting to gain an increased understanding of orbital dynamics and the maths related to it and using this information to create a n-body simulation. I have a like 3-4 months to finish it and I'm currently in high school so I am only...
  28. P

    An odd question on orbital dynamics

    Is there any kind of celestial event that could occur that could completely lock the Earth's rotation such that it is constantly facing the sun, in the same way the moon is tidally locked to the earth? What would it take? Could it be caused by the passage or entrance of a new gravitational...
  29. J

    Astrophysics: orbital dynamics - duration of a transit of Venus

    Edit: perhaps this might belong in one of the Physics help forums? Oops. Mods, please move if so! Homework Statement Show that a transit of Venus across the Sun’s disk lasts at most about 8 hours. The synodic period of Venus is 584 days and its orbital radius is 0.723 A.U. The Sun’s angular...
  30. B

    How can I find the shape of an orbit under an inverse cube law of force?

    Homework Statement I've found the a general form of equation for the explicit integration of the shape, r(\theta), of a one-body-problem (a particle rotating about a set point, O) for arbitrary \mathbf{f} = -f(r)\hat{\mathbf{r}}, and used it to find r(\theta) for an inverse square law f(r) = \mu...
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