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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This ISS trash deployment looks more like 2 feet than 2 inches per second, was it too fast or are these articles incorrect?

Digital Trends' Watch a NASA astronaut jettison part of the ISS into space which was linked in says: Writing in Air & Space last year about the process of jettisoning objects, veteran NASA ...
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How are co-located satellites positioned relative to each other?

I'm trying to learn about co-located GEO satellites. When I first heard about them, coming from a planetary orbital mechanics background, the first thing I pictured was based on the epicyclic ...
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How long would a Falcon Heavy last in orbit around Mars before degrading?

Elon Musk made another characteristic splash recently with his plan to launch a Falcon Heavy into orbit around Mars, with the bonus payload of his personal Tesla Roadster inside. Of course, it's an ...
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Transform ECI to ECEF

I need to transform ECI to ECEF coordinate. Here, I need the formula in math and algorithm. I have looking for the formula in the internet, but I can find one. I have x, y, z cartesian coord in ECI. ...
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How much energy is needed to bring Phobos closer to Mars?

Because Phobos has always the same face turned toward Mars, an electric propulsion system could be placed at the front to slow down the orbital speed. But what would be the energy needed to supply the ...
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Two 1000 kg gold spheres orbit their CM in near-contact, great way to measure G or limited by spaceflight issues?

The hypothetical, non-existent crowdfunding site go-launch-me is so confident, they are offering a two-for-one special. For a limited time, if your project is funded they will foot the bill for a 2nd ...
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How accurate can near earth asteroids be tracked?

To get more statistical significance for the suspected flyby-anomaly (or to refute it), it would be desirable to track as many hyperbolic earth flybys to within 1mm/s as we can get. Can we track ...
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“Pythagorean Three Body Problem” - need some points from an accurate solution for comparison

note: if you up-vote (or even if you don't), don't forget to scroll down and see the excellent answer as well - it's beautiful! The Pythagorean Three Body Problem also know as Burrau's problem is a ...
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Why do (did) they think WT1190F is low density?

A piece of space debris WT1190F is in the news in part because it has been far from earth (farther than lunar distance) in the past but will should have already re-enter earth's atmosphere in a few ...
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Finding x,y,z, vx,vy,vz from Hyperbolic orbital elements

I've written 2 functions to convert elliptical orbital elements to state vectors and vice-versa. Here is a web page containing them: http://orbitsimulator.com/formulas/OrbitalElements.html But my ...
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Totally Non-elliptic Rocket Path

I had never noticed it before, but when I was watching Apollo 13, the path of the rocket looked like this. Obviously since it's going around the moon, it won't actually be elliptical, but that doesn't ...
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Range of travel time between particular planets using the Interplanetary Transport Network/Interplanetary Superhighway?

I understand the Interplanetary Transport Network allows for travel at low speeds between different planets in the solar system using very little energy. Is there flexibility in how long it would take ...
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What is the sign of Earth's J2?

From Wikipedia's Geopotential model; The deviations of Earth's gravitational field from that of a homogeneous sphere and the question For the mathematical relationship between J2 (km^5/s^2) and ...
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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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How much less delta-v would it take to reach the Sun using Venus and Earth flyby's compared to direct?

@TomSpilker showed that the minimum delta-v to go from Earth orbit into the Sun is about 20.89 km/s. That's going from 200 km LEO to "perihelion at the sun's photosphere (guaranteed complete entry!)" ...
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Why would Humanity Star not be visible from North America (USA?) until March?

A quote near the end of the BBC's article 'Disco ball' put into space from NZ says: Jonathan McDowell, a satellite-tracker and astronomer at the Harvard-Smithsonian Center for Astrophysics, ...
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Questions about the Dynamic Solid Tide

I found the following plot in the book Satellite Orbits; Models, Methods, Applications by Oliver Montenbruck and Eberhard Gill, Springer, 2000. The figure and description can also be found in google ...
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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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Can orbital maneuvers be performed by a solar sail to correct eccentricity?

This unique model would spend very little time in Earth's shadow and eccentricity correction is performed on every pass. Can the angle of the hard flat solar sail or one big solar vane maintain an ...
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What exactly is “OMS2 Phase Angle”?

The vertical axis of this plot in this answer to How far apart are ISS launch windows? is labeled OMS2 Phase Angle (deg) and I don't know what that is. It's possible that OMS is related to things ...
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In a 3D space defined by semimajor axis, eccentricity and inclination, what would be the shape of the space where SDP4 works better than SGP4?

@BillGray's answer to Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4? is quite interesting and informative; I fail to do it justice by summarizing it as ...
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How to find T₀ and other parameters from a TLE to calculate an approximate mean anomaly?

The equation for mean anomaly is $$M = \sqrt{\frac{\mu}{a^3}} (t-T_0)$$ How could I extract information from a TLE in order to calculate a mean anomaly? Would I use this equation, or something ...
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How to understand this NASA animation of Juno's passes near Jupiter?

I don't understand! Rotating frame? I see Orion pass by around 00:30 to 00:36, that's a clue. Why the first two passes are on the same side (in this view) but the rest alternate? edit: This is ...
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Point Ahead Angle and Doppler Shift Frequency Changes Calculation with the tangential/radial velocity component for Inter-Satellite Link

While calculating the Point Ahead Angle we work with Tangential Velocity vector component and to calculate the Doppler shift i.e changes in frequencies, we work with Radial Velocity Vector component. ...
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How much does it cost to land on a lunar mascon?

This answer to Delta-v for landing on the moon estimates that to go from a circular orbit at 110km to a landing on a spherical Moon would require an absolute minimum of 1736 m/s and the Apollo landers ...
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How did the Lunar Module dock with the rest of Apollo 11 and what is the “CSM”?

I'd like to ask if anyone can, in layman's terms, describe the procedure by which the Apollo 11 astronauts were able to get back to their ship? I ask because the most accessible literature on this ...
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How can I predict what an object's orbital state vectors will be in the future?

I have a position and velocity vector for an orbiting object and can calculate the orbital elements. From a simple two-body situation, how can I predict where in the orbit the object will be at some ...
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Is it possible to have an orbit around the earth and the moon

I was just wondering if it were possible to A) Orbit the moon and earth B) To orbit any two celestial bodies really?
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At which point would two GSO/GEO satellites with similar orbital elements be closest to each other?

While I was answering another question on How closely spaced are satellites at GEO I came to realize I can't really word it with much conviction how two close proximity satellites in GEO/GSO orbits ...
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How complex was the math and physics necessary to place Apollo 11 on the moon?

Specifically, I'm interested in how closely the models used to calculate the various burns and course corrections represented reality. Was standard Newtonian mechanics sufficient or were relativistic ...
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What is the most fuel efficient way out of the Solar System?

I understand with current technology we can't just fly a straight line out of the solar system but which way out would need the least fuel? Currently to navigate the solar system it is a dance ...
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Do we sufficiently understand mechanics of Lagrange point stationkeeping for EML2 rendezvous and assembly?

I've been watching some recorded videos from the April 22 - 24, 2014 Humans2Mars conference (videos and live streams, when available, are on the National Institute of Aerospace channel on Livestream), ...
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A spacecraft leaves Earth exactly with escape velocity V2 - what trajectory it will have in Solar System?

A textbook solution: if a spacecraft leaves the isolated Earth with escape velocity V2 (=11.2 km/s at Earth's surface) it will have parabolic escape trajectory. But Earth is in orbit around Sun. The ...
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How can you predict an orbit, based on an initial position and an initial direction vector?

I've been developing a planetary simulator in Unity 3D (C#) and I need some help, however I feel this would be a better place for it. I'm starting my planet from a position vector. On initialisation I ...
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How long does one orbit around the Moon take in a typical parking orbit for a stage a lander is going to meet?

I have been pondering the relative advantages of placing a base near the Moon's equator, or at the poles. The poles have been defended as having a superior business case because of deposits of ...
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Calculating velocity state vector with orbital elements in 2D

I'm writing a little project that simulates an orbit by converting from initial state vectors $\vec{r}$ and $\vec{v}$ to Keplerian elements, then converting back to $\vec{r}$ and $\vec{v}$ from those ...
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How deep is the force well of L4 and L5 Lagrangian Points of Earth-Sun set?

The Lagrangian Points are points in space, where the combination of gravitational pull of a set of two bodies and the centripetal force of orbiting one of them add up to zero. The special property of $...
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Tiangong-1 reentry impact place probabilities

Following all the news concerning Tiangong-1, I have seen the following plot made by the Aerospace Corporation where Blue area: null probability of impact Yellow area: high probability of impact ...
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Will Rosetta have to adjust its orbit around Chury due to the comet's coma and tails?

ESA's Rosetta spacecraft is scheduled to orbit 67P/Churyumov–Gerasimenko after it reaches the comet by mid-2014: Rosetta's main objective is to rendezvous with, and enter orbit around, comet 67P/...
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Orbital mechanics: trying to understand counterintuitive behavior (braking to overtake)

If one spacecraft wants to overtake another (e.g. for a rendezvous), it has to (counterintuitively) brake, go into a lower orbit and use the higher angular velocity of that orbit/shorter orbital ...
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How to get semi-major axis from TLE?

This should be fairly straightforward, but, how do I get the semi-major axis (a) from at TLE. For example if I have the TLE: ...
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Could you stably orbit around a square (cubic) body? Would the orbit destabilize automatically if not corrected by input?

Given that the cubic body is of homogeneous mass (say Iron) and we want to start with the best possible orbit and input nothing afterwards, could something orbit this cubic body stably?
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What are the practical uses of a state transition matrix?

I am studying different dynamical models of relative motion of satellites. In my work, I've always just used a numerical integrator like RK78 to integrate the cartesian system of equations: $\dot{r}=...
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Is there any reason to send space probes along the plane of our solar system instead of perpendicular to the plane of our solar system? [duplicate]

Is there any reason to send deep space probes (Pioneer and Voyager) along the plane of our solar system (maybe with a slight inclination) instead of perpendicular to the plane of our solar system? If ...
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Is a lunar Sun-synchronous orbit possible at the “frozen” inclination of 86°?

I have been considering if it would be possible to place a satellite in a Sun-synchronous orbit in one of the lunar frozen orbits at 86°. According to NASA scientists there are four inclinations for ...
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How might one approach using AI (convolutional neural network) to predict collisions in orbit?

CNN's Tomorrow's Hero profile Meet Amber Yang. She's trying to prevent a space debris catastrophe describes an investigation into the use of a convolutional neural network (CNN) to predict possible ...
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Why has the Earth's motion carried it out of view of Pioneer 11's antenna?

According to The Pioneer Missions, my emphasis, The Pioneer 11 Mission ended on 30 September 1995, when the last transmission from the spacecraft was received. There have been no communications ...
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How useful is the Interplanetary Transport Network?

Wikipedia summarizes the Interplanetary Transport Network/Interplanetary Superhighway fairly succinctly, although it's pretty vague to someone who doesn't know what's going on: The Interplanetary ...
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How does a butterfly orbit move in 3D? Way to generate or visualize?

The paper Earth-Moon Near Rectilinear Halo and Butterfly Orbits for Lunar Surface Exploration (AAS 18-406) says Periodic Orbits in the Earth-Moon System The current investigation focuses on three ...
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What is hyperbolic eccentric anomaly F?

I have no idea what this is and have been searching on the net but all I get is eccentric anomaly. The equation that relates hyperbolic eccentric anomaly F to its true anomaly $\theta$ is exactly the ...

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