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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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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Orbiting Earth before heading to Moon

Each of the lunar Apollo missions (Apollo 8-17) entered Earth orbit immediately after launch. Each mission then left Earth after a few orbits by burning the S-IVB engine, and headed off to the Moon. (...
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Why is the ribbon of decommissioned geosynchronous satellites skewed?

I was looking at this 3D map of satellites orbiting earth and noticed something interesting. Around the green ring of active geosynchronous satellites, there is a ribbon of what I assume are obsolete ...
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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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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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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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Where to find the best values for standard gravitational parameters of solar system bodies?

Where can I find the best values to use for standard gravitational parameters of solar system bodies for numerical simulation experiments? Here are two sets I've put together. The first set is from ...
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Calculations Apollo astronauts were trained to do by hand if loss of guidance computer and/or data & coms link to Earth?

This answer to the question is it possible to navigate space travel with no computer? currently contains the line Yes, as long as you don't care where you end up but I am not so sure this is true. ...
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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 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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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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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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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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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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Deriving the changes in Keplerian Elements induced by small impulses

I'm trying to make derive a concise table of the effects on each Keplerian orbital element for a small impulse in the Radial, Tangential, or Perpendicular direction at periapsis or apoapsis, good to ...
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What is the escape-velocity for our galaxy?

What should be the escape velocity for our galaxy and can we calculate it? For instance, if we assume that we don't know the mass of our galaxy, you may consider it as small 'm'.
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Apollo 10: Where's Snoopy?

During the Apollo program, we launched a total of 9 Lunar Modules (LM's). The Ascent module from Apollo 10, or "Snoopy," is unique in that it was neither deliberately crashed into the Moon (Apollo 11, ...
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What's the reasonable “window” in days for a Mars-Earth Hohmann transfer?

As any popular science reader knows, when traveling between Earth and Mars, there's a Hohmann transfer opportunity about every two years (I believe it's every 26 months, specifically). What I've ...
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Could JWST stay at L2 “forever”?

Using only reaction wheels powered by solar panel and the sunshield as a sail (in continuous active attitude control) to generate thrust from solar photon pressure in the desired direction, could JWST ...
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Spacecraft Maneuvers as Intellectual Property? Wow!

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 activity - ...
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How much “wobble” does a typical geostationary satellite experience?

Recall that geostationary satellites are placed into an orbit which is designed to stay above a fixed point on the Earth's surface. If the Earth and the satellite were both spherical cows in an ...
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No need for gravity assist with Falcon Heavy?

Elon Musk is quoted to have said, after the launch of Falcon Heavy, that «it can launch things direct to Pluto or beyond, no stop needed, don’t even need gravity assist or anything». Now, I am not an ...
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How was Juno's arrival set up to be on the evening of July 4th?

Presumable it is largely a coincidence that Juno arrives at the perfect moment for American pride in NASA's achievements, but not entirely. The video below of the trajectory, released in July 2011 ...
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Launching east from a mountain on the equator at midnight during a new moon; ranking of each contribution?

This answer is intriguing and I'm curious if it's correct, and especially which effects are most important. If you want to avoid gravity assists, the most fuel-efficient way out of the Solar System ...
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Why doesn't the ISS use ion engines to maintain altitude?

So the ISS uses small thrusters on the Soyuz (usually) to perform occasional reboost burns to raise its orbit. This goes through, from what I can tell, around 3,500 kilos of fuel per year. Would it ...
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2nd stage speed - with respect to what? (SpaceX webcast of Orbcomm OG2 deployment)

As a follow-up question to this answer by @TildalWave, exactly what frame is used to calculate the "speed" in the inset display of speed and altitude in the SpaceX broadcast of the Falcon 9 launch and ...
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What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?

The Teslarati article SpaceX’s Falcon Heavy flies a complex mission for the Air Force in launch video discusses the upcoming third Falcon Heavy mission STP-2 and quotes the caption on the linked ...
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Why is Nodal precession affected by the rotational period of the planet?

The $J_2$ term in Nodal Precession equation has the rotational period of the planet. I understand that the oblateness of the sphere with an equatorial bulge induces a torque on the orbit of a ...
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What (the heck) are “space-fixed coordinates” as described in Apollo mission trajectory analyses?

@Ludo's answer to If I wanted to reconstruct an entire Apollo mission's crewed spacecraft trajectories, what are the key sources of historical data I'd look for? shows the table and its source shown ...
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Could a (differently) inclined orbit remain above a Lunar pole half of every revolution?

Let's say that we want constant communication between the Lunar north pole and Earth. The 5.145° orbital inclination of the Moon means that the (mountain at) the Lunar north pole will have line-of-...
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What is the basic mechanics behind the way the orbits of the twelve Vela spacecraft evolved over decades?

After reading the question Where is Vela 1A? Is there any information what its orbit would be like now? and the answer there, it looks like they were deployed in roughly 5 day, 100,000 km circular ...
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How to generate Chebyshev coefficients to produce an ephemeris file?

I am currently trying to perform the same interpolation that NASA uses to generate their Development Ephemeris files (Chebyshev coefficients). I have a table with position and velocity of the major ...
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Launch windows to Mars

I just watched a National Geographic documentary on ExoMars. In it, they mentioned there were 2 launch windows in early 2016 for the TGO/Schiaparelli launch, one in January and one in March. Quote ...
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How could a trip to Mars benefit from a “Distant (Lunar) Retrograde Orbit” DRO?

This guest blog text by Martin Elvis mentions a kind of orbit which I've never heard of before. How does the orbital mechanics work so that a DRO could benefit an interplanetary mission? ... ...
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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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The plane of the orbit of Juno around Jupiter is not the ecliptic plane. How did it get into this plane?

Did Juno start off its course on the ecliptic plane from the earth orbit and then left it at insertion to Jupiter's orbit over its north pole or it was always in that plane?
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Is it possible for amateurs to determine the orbit of satellites

Maybe some people urge this is a DIY site question but i thought here is the proper place to ask this question. Is it possible for amateurs like students with commercial and available equipment like ...
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How to determine an algorithm for Low Earth Orbit propagation, considering perturbation from the moon, sun, etc?

I'm trying to determine an algorithm for orbit propagation for a satellite on LEO, with high accuracy in a six month time ...
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Did Tiangong-1 turn the engines on?

The following graph shows the Tiangong-1 radius vector at the perigee, semi-major axis and apogee (scaled to 6371 km just to show an approximate altitude) and its orbit eccentricity: I used the SGP4 ...
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Differential Equations for Rocket Launch in Polar Coordinates

I'm trying to understand the equations of motion for a rocket launched from earth, through the atmosphere, and into LEO. I found a set of ordinary differential equations which describe the motion of ...
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How to get lunar L, B, C parameters from the Moon's 3x3 rotation matrix from the Python package Skyfield?

Answers to What are the “Moon L, B, C” angles shown in this solar eclipse simulation? explain that L and B (or "l" and "b") are the "selenographic coordinates of the Moon's apparent center" (latitude ...
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Would it be possible to Boost ISS to L1 or Lunar Orbit?

NASA and Russia plan to retire the ISS before 2030, and to launch a new lunar outpost to lunar orbit. This output could then be a gateway to future mission to Mars or the outer solar system. My ...
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How to calculate the orbital distance between 2 satellites given the TLEs

I have 2 LEO satellites with the same orbital plane with same inclination & longitude of the ascending node. I have the TLEs for each satellite. How do I calculate the orbital distance between the ...
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What's the planetary exploration word for “impact parameter” (distance of closest approach if gravity were “turned off”)?

In particle scattering there's a term called "impact parameter", which is the minimum distance a particle would pass a second particle at rest, if the attractive or repulsive force were ignored or "...
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Why is DSCOVR in a Lissajous orbit? Wouldn't a halo orbit completely avoid the Sun exclusion zone?

Halo orbits are a sub-class of Lissajous orbits. See this answer for (much) more on that. DSCOVR's orbit will put it in it's Sun Exclusion Zone in about 2020 where the communications line of sight ...
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Flying to orbital nodes

Given the Keplerian elements for an object for current time. The object is on ellyptic orbit. How to calculate, at what time the object will be on one of the orbital nodes? That's required for ...
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Can objects be deorbited by a satellite using a magnetic field?

Can a magnetic field be made around a satellite for a split second to gain or loose momentum from another satellite or debris with a few passes with a near-miss trajectories on larger debris? Could a ...

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