Questions tagged [orbital-mechanics]

Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft. For the movements of celestial bodies, see [celestial-mechanics].

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Is this C# code to obtain the coordinates of the planets correct?

This should be a comment to an 2012rcampion's answer to this question: Determining orbital position at a future point in time I'm using the linked data of that answer, under "Computing Position ...
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Simple explanation for the 2nd “cosmic speed”

Many sources can explain about the first, second and third cosmic velocities, but the explanations contain difficult formulas and are not easy to understand. I can check with a powerful magnet and an ...
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What altitude would an aphrodiosynchronous satellite need?

A geosynchronous orbit has a period of 24 hours, and mostly stays over the same location on the surface of the Earth. According to this blogger, the equivalent term for Venus should be "...
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J2000 to current ECI transformation matrix

I want to find the transformation matrix that converts an ECI frame at some time 't' (lets say t = 1st January 2020) to J2000 ECI frame (that is ECI frame at noon of 1st January 2000). From what I ...
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What was Chang'e-2's 3D orbit in space? (since it's not in Horizons)

edit: A simple web search in Chinese may turn up something, but I don't know anyone personally who is both both fluent and interested in space exploration. This is a pretty cool orbit - there must be ...
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Find the jump condition of the mass costate of a Launch Vehicle ascent problem solved via an indirect method (Pontryagin Minimum Principle)

I'm trying to solve a trajectory optimization problem for a class of problems like the old Altas-Centaur SLV3 Centaur launch vehicles. Those are a stage and a half design where the 2 LR-87 engines ...
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How was the radius of Venus measured so accurately (± 3 km) via radar in the mid 1960's, before Venera 4 and Mariner 5?

In several answers to the question When did planetary scientists realize Venus' surface pressure was almost 100x that on Earth? How did they find out? the known radius of Venus is mentioned. It was ...
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Why was Voskhod 1 at an inclination of 64.7° degrees while Salyut 6 launched from the same latitude was at 51.7°?

This answer to Have any Soviet-era astronauts reported seeing Earth's aurora or related luminescent atmospheric effects? mentions sightings from both Salyut 6 and Voskhod 1. While Salyut 6 orbited for ...
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Who called the Lagrangian points as “Libration” points and and why was the terminology “Libration” used?

I am curious about the naming and why were the equilibrium solutions of the CR3BP called as Libration points? Who called them that and what is the history behind it?
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Maneuver in the intersection of 2 orbits

The spacecraft transfers between two co-planar orbits. The initial orbit has the Ra = 2000km, Rp = 600km and ...
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Low earth orbit propagation in GMAT

I'm propagating a Low Earth orbit using GMAT. I 'm trying to make the propagation realistic, considering the zonal harmonics, Sun, Moon, Jupiter, Venus perturbations, tidal forces and solar ...
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What is the physical interpretation of the eigenvalues of the monodromy matrix and how are they associated with the invariant manifolds?

To define the monodromy matrix, assume that the period for one cycle of a halo orbit is denoted as $T$, the initial time as $t_0$, and the state-transition matrix is defined as $\phi$. Then, the ...
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The Martian: Does it really take a supercomputer to calculate spaceflight maneuvers?

My preemptive apologies for asking a question about a movie, and the spoilers within said question, but considering the widespread support for its scientific plausibility, I'm hoping you'll let it ...
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Have people in orbit ever been bothered by the difference between their orbit and the station's?

When floating inside a large space station, while away from its center of mass and without touching the structure of the station, the person floating and the station will have slightly different ...
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Terraform via moving Ceres To Mars orbit, using ion drive

EDIT: Apparently the accepted physics has changed, and we now use the convection model for generating planetary magnetic field, not the dynamo model. Next thing you know people will be telling me ...
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How to calculate the planets and moons beyond Newtons's gravitational force?

The question Calculating the planets and moons based on Newtons's gravitational force was pretty much answered with two items: Use a reasonable ODE solver; at least RK4 (the classic Runge-Kutta ...
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Who invented the sun-synchronous orbit?

I was explaining sun-synchronous orbits to a co-worker and he asked me who invented it and when. I could not find an answer on wikipedia or a quick google search, so I thought about asking here.
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Do you need 0 km/s velocity to crash into the sun?

I was reading a popular thread about the delta-v required to escape the solar system compared to the delta-v required to crash into the sun. I get it: the earth itself already has a high speed (29.7km/...
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How many times will the Photon fire its Curie in order to “reach the right spot” to deploy CAPSTONE towards the Moon?

The Verge's How small launcher Rocket Lab plans to pull off its first mission to the Moon next year says (though this has since been addressed†): Photon is going to need it all in order to get NASA’s ...
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Did Sputnik 1 tell us more than “beep”? What science was improved by information gained from its orbiting the Earth?

Sputnik 1 was the first artificial satellite launched by humans to orbit the Earth. This answer begins: Sputnik had just one single job: Prove its existence by sending a simple "beep" ...
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Satellite inclination, 3D scanning of earth's surface

Has any attempt been made to change the "plane" of the orbit (not altitude) of a satellite, across earth's diameter, continuously in small steps, from pole to pole for a satellite with zero ...
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Accuracy of converting from TLE/Orbital Elements to Cartesian if used for other propagator?

Say that I wanted to propagate a real-life satellite based on an initial position in space. However, the only source of data I can get is from a tracking website like CelesTrak or Space-Track, where ...
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Does the Earth's orbiting the Sun influence spacecraft in Earth's orbit?

As I try to comprehend how spacecraft are able to stay in orbit around the Earth I began to think about why the Earth's own orbit around the Sun does not influence spacecraft in Earth's orbit. I came ...
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How are gravity coefficients calculated?

I was reading Satellite Orbits - Models, Methods, and Applications by Montenbruck & Gill and was trying to use the equations in it to calculate $J_2$ as used in the GEM and JGM gravity models. ...
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Why will OGO-1 reenter from an elliptical orbit rather than circularize first?

According to all the sources cited in Why does OGO-1's trajectory and imminent reentry come from sky surveys and NEO tracking rather than normal satellite tracking? OGO-1 is in a highly ...
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Spacecraft Maneuvers as Intellectual Property? Wow!

In the past I had encountered a few mentions of orbits being patented (or at least applications filed) but didn't take much notice. Then I did a simple search and was blown away by the sheer volume of ...
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Optimization of low-thrust in-plane maneuver

I have to build an optimal trajectory between two orbits, which are in one plane, but with different semi-major axis, argument of perigee and eccentricity. I've read different articles regarding the ...
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How to implement SGP4 C++, satellite propagator?

I would like to ask about how to implement the SGP4 code in C++ by Vallado. How can I implement the libraries that are available in https://celestrak.com/software/vallado-sw.php. I think that are the ...
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Does Kerbal Space Program have a software migration path to Lagrange points, halo orbits, and other 3-body goodies?

At about 05:37 in Scott Manley video Kerbal Space Program 2 - What We Know About The Sequel So I’m cautiously optimistic and I really obviously want this to be ...
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Why do rockets coast before secondary payload deployment?

I was watching a falcon 9 launch. After SECO, stable orbit was achieved and the primary payload was deployed. The 2nd stage coasted for an hour (no burns in between) and then deployed rideshare ...
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Launch vehicle trajectory tool for ascent phase to orbit using PYTHON

Currently, I am developing a trajectory optimization tool for launch vehicle from lift-off to orbit using python for my project. Since I'm new to optimization problem, I am finding it hard to ...
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Is the Jacobi constant stationary along a periodic orbit?

In the book called "Chaotic Worlds: from Order to Disorder in Gravitational N-Body Dynamical Systems", link here, the author states that if the dynamical system has an integral of motion which is not ...
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Earth's Axial Precession and Frame Change [duplicate]

Is Earth's Axial Precession and change in Axial tilt values significant enough to be considered while writing Rotation matrix that converts Body frame into ECEF frame and also while propagating Orbit ...
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How to programmatically calculate orbital elements using position/velocity vectors?

I would like to build some orbital mechanical software from scratch. I feel that this would be a great way to learn the steps required to calculate different Kepler orbital elements of an object, plot ...
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What is the simplest way to determine if two or more TLEs describe two or more satellites in lead-follow?

If two more more up to date TLEs have same inclination and the same period they are in the same orbit, but how do I check if they are also following each others path, in a train?
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SpaceX 2nd stage or tumbling satellite? WSW to NE over FL

Around 2040 EST We viewed an irregularly flashing object flying from WSW to NNE (roughly) from Jacksonville FL. Is the SpaceX 2nd stage still up there and if so, would it be tumbling and visible? Is ...
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Determining orbital position at a future point in time

This might come of as a millionth-time award winner beginner question, but since I'm not familiar with either correct terms or designations, I'll put this question in my own language, since I'm not ...
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How does orbital altitude nomenclature work?

The orbital phase of many probes around a planet or moon is frequently described as N km x M km, with N and M being two numbers. For example, China's Chang'e 5 lunar orbiter was "placed in a 200 by 5,...
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Apparent Centering Problem When Using the Perifocal System to Draw Orbital Ellipses

I am attempting to render orbital ellipses in software. Given a set of orbital elements, I am using the Perifocal system to determine a set of points along the curve of the ellipse. I am using the ...
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Delta-v penalty for stopping in a distant Earth orbit versus using atmospheric reentry for braking and returning to Earth from Mars?

Comments below this answer to What precautions are planned to prevent an accident or anomaly from releasing Martians into Earth's environment? say: Seems to me like a high earth orbit lab might be a ...
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Does the Newton-Rhapson solution to Kepler's equation diverge?

I have the following simple solution to the Kepler's equation which uses newton-rhapson iterative technique. I have read various papers about the initial guess and divergence near an eccentricty of 1, ...
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Will the Emirate Mars Mission, Tianwen-1 and Mars 2020 Mission get closer to each other or spread out on their way to Mars?

The brand new Where Is Roadster page Spacecraft launched to Mars in 2020 (announced here) currently says that it has been: 13 days, 3 hours, 47 minutes and 13 seconds since the Emirates Mars Mission ...
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Why is the bend angle of a hyperbolic trajectory giving different results?

The bend angle ($\delta$) is the reflex angle between the two asymptotes of a hyperbolic trajectory. From this Stack Exchange answer, the formula to calculate the bend angle is: $$ \delta = 2 \sin^{-...
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How to calculate the local maximum solar radiation on Mars from day to day throughout a full martian year?

I would like to know where on Mars the least lowest daily temperatures depending on the time of year will be. At first glance one might think, as I did, that it has to be along its equator, but ...
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Error in Propagating equatorial orbit using GMAT

I propagated an orbit with semi-major axis of 7000km and the rest of the keplerian orbital elements 0 on GMAT. Since the orbit is circular and in the Equatorial plane, it should not change over time. ...
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Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v needed to move from one to the other?

This answer discusses a spacecraft in GEO using a two-impulse (circular → elliptical → circular) raise & lower maneuver to move (phase) itself by 180 degrees in longitude then return to synchrony. ...
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Keplers equation: written in change in eccentric anomaly

I am reviewing the "Fortran Astrodynamics Toolkit (can be found here) and even more specifically at the two body propagation method implemented in this Kepler module for elliptical and circular ...
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Why can't I just use dot product angles to get satellite vision of a point on Earth?

Right now I'm using MATLAB and can easily get the ECEF coordinates of the satellite and the point on the Earth. Since ECEF is cartesian, why can't I just rearrange: $$ r_{es}\cdot r_{ps} = \|r_{es}\| ...
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Getting back from the Moon

This link describes the way back from the Moon surface to the orbiting spacecraft. But how could that spacecraft get back to the Earth? It is a long journey. How much rocket fuel would be needed, in ...
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Is a 2:1 “figure-eight” Lissajous orbit possible in the Circular Restricted Three Body Problem?

Was Queqiao in a halo or Lissajous orbit? Why do sources disagree? says Proper halo orbits have the same period for their in-plane oscillations and out of plane oscillations, so they are closed ...

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