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 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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How to best think of the State Transition Matrix, and how to use it to find periodic Halo orbits?

I'll state my mathematical question about the state propagation and state transition matrices first, then show you a simple problem for which I would like to use these concepts to generate a densely ...
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Why is a near rectilinear halo orbit proposed for LOP-G (formerly known as Deep Space Gateway?)

Why is a near rectilinear halo orbit a good place for a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway)? Are there specific logistical and orbital-mechanical advantages over ...
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What is a near rectilinear halo orbit?

A proposed option for the lunar orbit of a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway) is a near rectilinear halo orbit, or NRHO. This excellent answer discusses the ...
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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 sort of orbital elements are used to describe halo orbits?

For standard orbits we can use Keplerian elements, TLE, or other similar. These don't make much sense for Halo orbits, which are not around a central body, but around a Lagrangian point, and follow an ...
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SpaceX's 4,425 satellite constellation - what's the method to the madness?

The BBC article SpaceX aims to launch internet from space discusses the SpaceX proposal for a dense array of over 4,000 LEO satellites for global internet coverage, and links to SpaceX non-...
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How is the altitude of a satellite defined, given that the Earth is not spherical?

The altitude of a satellite is the distance between the Earth's surface and the satellite, but the Earth itself is not spherical. At the equator the Earth's radius is 21 km more than at the poles, and ...
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What are the choices today for orbital mechanics simulation software?

I used to be familiar with the various choices out there for orbital mechanics simulation software. Alas, those days are gone. What are the choices today, preferably sorted by platform? This ...
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What can the KSP game actually teach about spaceflight and orbital mechanics, and what are its limitations?

I have seen at least several different users mention that they've found Kerbal Space Program helpful to understand issues of spaceflight and orbital mechanics. According to Wikipedia: While the game ...
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How can I intuitively understand gravity assists?

For example: How should a spacecraft pass the Moon to reach escape velocity from Earth? How should it pass Venus for a slingshot towards Jupiter orbit? Conversely, to descend Venus to Mercury? Is ...
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How can I plot a satellite's orbit in 3D from a TLE using Python and Skyfield?

I have obtained a Two Line Element (TLE) of a satellite in Earth orbit from Celestrak at https://www.celestrak.com/NORAD/elements/ and I would like to use it to calculate an orbit. How can I ...
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What artificial satellite has the farthest orbit around the Earth?

What is the furthest Earth orbiting satellite? What is its speed and purpose?
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TESS orbit and moon resonance

On April 17, SpaceX will launch TESS satellite. Satellite description: The Transiting Exoplanet Survey Satellite (TESS) is a planned telescope for NASA'S explorer progra. designed to search for ...
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Are some Halo Orbits actually Stable?

UPDATE: I found another reference! While I always enjoy a good video starring Jimmy and Linda Carter, this one has Dennis Wingo describing ISEE-3's original Halo orbit. He describes Sun-Earth $L_1$ as ...
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The Orbital Mass Accelerator Engine Theory

Can 2 satellites equal in weight traveling on the same orbital path in the opposite directions intersect and propel each other to gain altitude in orbit? Can orbital perturbation be negated during ...
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Going from LEO to lunar using only low-thrust ion propulsion - can it be done?

@SF.'s question What are the parameters of the new Iodine electrical rocket engine developed by RSC Energia? links to the short RT article 'Ten times cheaper': Russian space company testing iodine ...
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What happens to JWST after it runs out of propellant?

JWST will be orbiting L2 which is unstable equilibrium thus will require propellant for station keeping. JWST will carry propellant for 5-10 years. What will happen once it runs out of propellant? ...
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How (the heck) can 2014 MU69's orbit be know well enough for a close flyby by New Horizons?

The object 2014 MU69 is much smaller and dimmer than Pluto. Even as New Horizons approaches, it will be much harder for its 8.2 inch aperture, cooled CCD long range imager LORRI to get a fix on it ...
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For the mathematical relationship between J2 (km^5/s^2) and dimensionless J2 - which one is derived from the other?

The term $J_2$ seen in discussions of nodal precession of orbits (e.g. sun-synchronous) appears to come in two flavors. For example, in the Wikipedia article Geopotential model it has a value of $1....
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Did DSCOVR travel “along the stable manifold of it's future SE L1 Halo orbit” to get there?

I just wrote (and have since removed) the following paragraph in this answer: As can be heard in this video SpaceX's launch of the DSCOVR spacecraft to Sun-Earth L1 went there almost directly. The ...
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How often does ISS require re-boosting to higher orbit?

I know that ISS, being in low Earth orbit, requires regular boosts. But I can't seem to find information on how often does this happen. Is it done during each resupply mission, only during some of ...
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Is SGP4 propagation necessarily more accurate near the epoch chosen for TLE generation?

This interesting answer includes a quote from Space-Track: From Space-Track.Org FAQ TLEs can contain future epochs. About 20 satellites are categorized as "multi-day objects" ...
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The strange orbit of Ofeq 11 - how does it (actually) do this?

I assume the retrograde orbit ($\theta_{inc}=142°$) is a side-effect of geography - ocean overfly access only lies West of the secured launch site - this article in Spaceflight 101 makes several ...
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Rotating in orbit?

Reading this question (Is the cupola, on the inside of the ISS, cold or warm to the touch?) prompted me to wonder about an object in orbit's orientation as it orbits its host object. For example, ...
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Are there terms for Earth orbits with rational number multiples of 1 sidereal day?

An Earth orbit with a period of 1 sidereal day (and zero inclination) is a geosynchronous orbit, orbits slightly above and below that are supersynchronous and subsynchronous orbits, and a Molniya ...
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Could the sun be used as a gravity assist outside the solar system (with current tech)?

I think I might have understood what this XKCD comic is trying to do. The diagram is proposing to use the Oberth effect at closest approach to the sun to escape the solar system! (image license: CC ...
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Is the “airship to orbit” mission profile feasible?

By one of those weird coincidences, I had been on JP Aerospace's site mere hours before reading this question about space dirigibles here. Their mission plan seems too good to be true. They are ...
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What are the conditions for re-entry of an object in a (highly) elliptical orbit?

There's something I don't understand: When it comes to de-commissioned satellites, rocket bodies etc. I thought one way of re-entry was via a highly elliptical orbit: The perigee gets low enough (app....
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Why do malfunctioning satellites come back to Earth?

In school, I learned that if a satellite moves at a speed $\sqrt{gR}$ (the square root of the product of the acceleration due to gravity and radius of the Earth), then it will remain in Earth's orbit. ...
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What is the ISS drag?

ISS constantly loses altitude to air drag and other forces (tidal, electromagnetic). While finding that rate in the sources isn't that hard, with orbital mechanics of altitude loss actually increasing ...
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Could a satellite in LEO “pump” or change mass distribution to gain forward momentum?

Similar to pumping your feet on a child's swing can a satellite run up and down a pole to produce a forward momentum? Red dots is the satellite's position running up and down the pole on an ...
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How will JWST manage solar pressure effects to maintain attitude and station keep it's unstable orbit?

The James Webb Space Telescope presents a huge reflective cross-section to the Sun's photons, and this can generate both torque and thrust. How will JWST manage solar pressure effects to maintain ...
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Thrust and rotation strategy to circularize a standard GTO orbit using ion propulsion?

The previous question How much time does it take to circularize a GTO orbit using ion propulsion? has a good, quantitative answer based on a known delta-v. But I'm wondering how would you actually ...
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Why should space probes have to orbit the Earth before being launched at other planets?

I'm curious to know why any satellites that need to be sent to other planets should be moving around the Earth rather than directly going towards their destination? Today, India launched one satellite ...
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Can a satellite work like a radiometer?

Like a Crookes Radiometer, could a satellite have a stiff vain to maneuver? With a white side to let light pass and the black side capture light radiation be enough provide radiation pressure to keep ...
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Spiraling out from circular orbit to escape via low thrust, what is γ (gamma)?

@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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Are large halo orbits around L₁'s and L₂'s preferred over small orbits for reasons other than geometry?

There have been many examples of the placement of satellites in orbits around Lagrange points, most have been sun-earth and earth-moon $L_1$ and $L_2$ due to their proximity to earth. In each case ...
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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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Juno's original orbit around Jupiter - is this apsidal precession? If so, need expression

Below is a plot of Juno's originally planned orbit around Jupiter, extracted from JPL Horizons. It's shown in J2000 ecliptic coordinates, centered on the Jupiter barycenter. It turns out the orbit is ...
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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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Brouwer-Lyddane mean semi major axis bias

I'm using the software GMAT (General Mission Analysis Tool) (website, YouTube) for propagating spacecraft and calculating their Brouwer-Lyddane (BL) mean semi-major axis (SMA). I found out something ...
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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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Can you tack against the sun using a solar sail?

Solar sails are a great, inexpensive way to move out from the sun, if you’re not in a hurry. Ocean going ships are able to tack against the wind, and to move up wind. Could a solar sail gain inbound (...
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Is it possible to reach the Sun without expending any fuel/reaction mass?

Imagine that I'm designing a space probe, that will initially be placed into an Earth-like orbit around the Sun. My goal is to have the probe fly/fall into the Sun; it's allowed to take as much time ...
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What's a Brouwer-Lyddane mean semi major axis, or any other, for an orbit in a lumpy gravity field?

The really nicely written question Brouwer-Lyddane mean semi major axis bias describes the use of the software GMAT (General Mission Analysis Tool) (website, YouTube, giant PDF for TESS) for ...
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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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Physical meaning of perigee advance

I'm starting to study orbital perturbations and I can't find any physical explanation about the perigee advance (apsidal precession) when considering Earth oblateness effects. Can someone give a ...
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Why would a slow spiral from a C3 of zero take about 2.4 times as much ΔV as an impulsive maneuver?

I just read a fascinating comment that I don't understand. In part it says ...the Oberth effect does not depend on the mass of the object. A slow spiral in to a low orbit from a C3 of zero will ...
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What precisely is downrange distance - how is it defined mathematically?

Wikipedia: Downrange is the horizontal distance traveled by a spacecraft, or the spacecraft's horizontal distance from the launch site. Spacecraft don't travel horizontally. I don't even know how ...

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