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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Did Rosetta improve on models of non-gravitational effects on comet 67P's orbit?

Question: Since the presence of the Rosetta spacecraft near comet 67P allowed for a detailed mass measurement, extremely precise position and velocity determinations, and physcal measurement and ...
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How far would the Mars L1 Lagrangian Point be from Mars?

I am a sci-fi writer, and I've heard about the concept of putting some type of magnetic deflector near the Sun-Mars L1 point to deflect charged particles from the Sun to reduce radiation effects on ...
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How will the Lunar Gateway go to L2 and L1; how much delta-v is needed?

In a talk to the press which can be heard in the YouTube video NASA Administrator Jim Bridenstine Explains the Lunar Gateway, NASA director Jim Bridenstine says after about ...
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Do Lissajous orbits have stable/unstable manifolds?

The question Did DSCOVR travel “along the stable manifold of it's future SE L1 Halo orbit” to get there? is specific to DSCOVR's trajectory from Earth to its primarily heliocentric orbit near Sun-...
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Equation for orbital period around oblate bodies, based on J2?

In this answer I point out that the period of items (ring particles, moons, spacecraft, etc.) around an oblate body will not scale exactly as $a^{3/2}$ because the closer you are to the planet, the ...
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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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What uses would the Aldrin-Cycler have?

An Aldrin-Cycler is a vessel on an orbit on which it passes both Earth and Mars every few years without expending much fuel. At first glance this seems like a great thing for a permanent ...
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Does a satellite naturally turn in phase with its orbit, always facing Earth?

Assume you want a satellite to constantly point its radio dish towards Earth while orbiting it, or its solar panels towards the Sun if it is instead orbiting it. Is any of the following true about ...
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Do any launches bypass LEO?

If sending a payload to GEO (geosynchronous orbit) or any other high orbit, you could start off launching to LEO (low Earth orbit), and then use a Hohmann transfer to raise the height of the orbit. I ...
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Why does the ISS track appear to be sinusoidal?

Okay, time for a stupid question, but it keeps me up at night trying to figure it out. The ISS 'route' appears on paper as such: I am imagining it has to do with a combination of its orbit and the ...
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How does the poliastro python package “Going to Mars with Python” example work? What's it really doing?

@astrojuanlu's answer mentions the existence of the Python package poliastro, and in the documentation there I found an example titled Going to Mars with Python using poliastro among others. Input ...
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Brachistochrone variation for Earth-to-Mars Orbit

Wouldn't a Brachistochrone curve to Mars orbit be a much faster and more efficient way to send personnel and equipment to mars as compared to the Hohmann transfer if we used an Ion engine? The below ...
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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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Timing shadows from the Kuiper belt! Any news? Did it work?

update 24-Jun-2017: SOFIA Arrives in New Zealand to Observe Southern Skies There are plans to fly SOFIA through another predicted occultation path on July 17. SOFIA is a huge (2.5 meter dia.) infrared ...
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What is the functional form for r(t) for a solar-sail deorbit into the Sun?

This answer describes a spacecraft in a heliocentric orbit using a solar sail to "deorbit" into the Sun by reflecting sunlight into roughly the prograde direction. In comments it was proposed that ...
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Help with my tensor tension; how to derive and calculate this rigid body gravity gradient torque?

Tensors make me tense. Imagine a long thin rod in a circular orbit. The gravity gradient will produce a net torque on the rod whenever it is not oriented parallel, or perpendicular to the radius ...
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What is the difference between halo orbits and Lissajous orbits?

The Wikipedia articles for halo orbit and Lissajous orbit leave me wondering how these two orbits are different from an orbital mechanical point of view. Could they be discussed together here, so I ...
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Analytical expression for the ground track of the International Space Station

For a maths task in school, I am investigating the orbit of the International Space Station around the Earth. I understand that when the 3D movement in space is represented on a 2D surface, the ...
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Was this large pieces of “space junk” just released from the ISS in the “nadir and retrograde” direction?

According to Space.com's 02-Feb-2018 article Cosmonauts Break Russian Spacewalk Record During Space Station Antenna Repair: The cosmonauts spent the day replacing an electronics box for a high-gain ...
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Is the ideal transfer between two arbitrary planar orbits always a bi-tangential ellipse?

I was reading Hollister David's short paper on bi-tangential transfers. The example he uses is a transfer between a planar circular and an elliptical orbit. I am wondering: Is an ideal, that is, the ...
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Converting Orbital Elements to Cartesian State Vectors

Updated 2016-12-12 I'm writing an orbital mechanics program in Unity. I convert an orbiting object's position and velocity into orbital elements, then converting the orbital elements back into ...
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Why would Sun-synchronous orbits be impossible around perfectly spherical bodies?

This is a special case follow-up to Are sun-synchronous orbits possible around any body? Reading Wikipedia on Sun-synchronous orbit a few days ago when trying to refresh my memory on orbital mechanics ...
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What are these orientations called in orbit?

Let's say a spacecraft is in an orbit like this one: If the red arrows point to prograde and retrograde, and the blue arrows point to normal and antinormal, what do the green arrows point to? In ...
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How much delta-v can we squeeze out of a gravitational slingshot and what factors limit it?

A lot of space probes use gravity assists from various space objects to boost their speed and save on propellant requirements. On what factors does the increase of delta-v depend? My guesses are: ...
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How often does the ISS orbit align with the day/night terminator?

In the following image (coming from SAT-Flare) you can see the orbit of the ISS (in red) and the day/night terminator (in blue). The terminator separates night from day along the surface of the Earth. ...
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Is the difference in orbital velocity of different parts measurable on board the ISS?

When two objects are in different orbits of the same body, no matter how close they are, the inner object will always be faster - it will move farther away from the outer one (until it gets closer ...
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Are patched conics (and by induction, KSP) “useless” for simulating ion propulsion?

My previous KSP question What can the KSP game actually teach about spaceflight and orbital mechanics, and what are its limitations? resulted in some really productive discussions and under-the-hood ...
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To what extent could a single Triton flyby slow down a direct Hohmann transfer to Neptune for NOI?

I can't seem to find any good sources online for this, all I get are documents on how Nice model was used to compute Neptune's gravity capture of Triton via a binary dissociation, possibly because of ...
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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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How did NASA determine the distance and velocity of voyager 1?

According to Wikipedia At a distance of about 125.97 AU (1.884 × 10$^{10}$ km) from the Sun as of September 9, 2012, it is the farthest manmade object from Earth As of 2013, the probe was moving ...
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What are “Ohms burns” in the context of Scott Kelly, KSP, and the Space Shuttle?

The Ars Technica video Astronaut Scott Kelly teaches orbital mechanics with Kerbal Space Program (also in YouTube) is a little bit humorous. When Scott Kelley is talking about orbit circularization ...
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Low Energy Transfer within Earth-Moon system

Practical aspects of a total low energy transfer to the Moon have been seen in missions like GENESIS, which uses Weak stability Boundary legs of Earth and Sun to reach ESL-2. This four body model ...
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Does the “17” really mean anything with respect to GNSS orbits being rational factions of a sidereal day?

This answer to Why are orbital periods different for different GNSS positioning system constellations? suggests that the orbital periods of the four large GNSSS constellations are linked to the ...
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Lunar Free Return Trajectory Simulation

I have been trying to simulate a lunar free return trajectory using the state vectors for the Apollo spacecraft provided by JPL after they had performed their trans-lunar injection burn. My ...
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What is this algorithm to calculate orbital state vectors?

I came across the following algorithm to calculate the cartezian vectors from the orbital elements: First calculate some coefficients that will be used in determining the position: $$ r_x' = a (\cos ...
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Algorithmic methods or techniques to find conjunctions in high N Keplerian element ensembles?

Suppose I wanted to answer the question Will Starman/Roadster pass particularly close to any asteroids in the next few years? or try to predict satellite conjunctions around Earth (e.g. Celestrak's ...
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Why does InSight plan to launch from Vandenberg

Why does the InSight Mars lander mission intend to launch from Vandenberg, which does not allow for prograde launches? Will it launch into polar or retrograde orbit? Why? It will do an interplanetary ...
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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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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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Ratio of low-thrust slow spiral to Hohmann transfer $\Delta V$?

Going from one circular orbit to another, there are tables out there and equations that give the total $\Delta V$ needed for a two or three impulse maneuver scenario. For a very low thrust propulsion ...
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Why does TDRS 1's inclination evolve so much differently than that of all the others starting in 1995?

The plot below is from the question Why do the geosynchronous TDRS satellites have this distribution of inclinations?, and the explanation says Inclination and mean motion (rev/day) for TDRS ...
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How to calculate the flight path angle, γ, from a state vector?

@Julio's excellent answer describes a flight path angle, and explains that it is the angle between the tangential direction (perpendicular to the radial vector to the central body) and the current ...
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Low-thrust spiraling to escape, is the flight path angle (gamma) at C3=0 always 39 degrees?

@MarkAdler's comment led me to ask Why would a slow spiral from a C3 of zero take about 2.4 times as much ΔV as an impulsive maneuver? which resulted in this tidy and efficient @MarkAdler answer which ...
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Why would Hollywood's Planet X (at earth's L3) be unstable?

This NASA website states "NASA is unlikely to find any use for the L3 point since it remains hidden behind the Sun at all times. The idea of a hidden "Planet-X" at the L3 point has been a popular ...
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How to best patch my conics?

I thought I'd try to use patched conics to see what it's like. I'll go from LEO to LXO (low Planet-X orbit), co-planar all the way. If I understand correctly, I'll have (at least) five conics. The ...
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Is Dawn's upcoming low periapsis orbit for XMO7 “resonant”?

The Spaceflight Insider article Dawn will enter lowest ever orbit around Ceres says: In his Dawn Journal blog, mission director and chief engineer Marc Rayman discussed the challenges of bringing the ...
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How to find Near Rectilinear Halo Orbits (NHROs)?

Looking all the good questions and answers in this site referent to CR3BP dynamics, periodic orbits, state transition matrices, etc. I wonder: what algorithm or steps do I have to follow to find the ...
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Can someone help Scott Manley explain this Snoopy-capturing maneuver?

In his recent video Apollo 10's Lunar Module Snoopy Is Lost In Space - Could We Bring it Home? Scott Manley uses some fancy supplemental techniques in KSP to simulate and explain a possible mission to ...
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What do the green lines represent in this Lagrange Point animation?

This is one of my all-time YouTube favorite videos. It's an illustration of the Earth-Moon Lagrange points in orbit around the sun for a year. Put on your headphones, dim the lights, and set YT to HD. ...
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Parallel orbits around the Earth - effectively?

edit: For the purposes of this exercise, one could consider using three or four identical spacecraft, and using the "best two out of three (or four)" for interferometry at any given moment. In 1994, ...

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