# Questions tagged [orbital-mechanics]

Orbital mechanics (also called astrodynamics) is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft on an orbital or escape trajectory. For the movements of celestial bodies, use [celestial-mechanics], not this.

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### Would it take less thrust overall to put an object into higher orbit?

Obviously, the engineers put things up to LEO for a reason, but my understanding is that much of the burn is used in getting the object up to orbital velocity. Higher orbits are slower, but is the ...
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### How can flyby missions work?

I understand that a small object (Spacecraft) which approaches a large body (planet) will be accelerated. But as the gravitational field is a gradient field, the small object should lose all the ...
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### What is the maximum possible delta v we could achieve from assembling a chemical rocket in orbit (not launching a final stage from the ground)?

To clarify, this is about an orbital assembly. I am not asking the maximum weight of launch vehicles or anything relating to that. This is a pure hypothetical scenario in which we have an infinite ...
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### How to find the velocity vector of a planet in orbit argument of periapsis or longitude of the ascending node?

Edit : This question has been answered. If anybody else creating a fictional planet has a similar question to mine, with a not-so-good understanding of orbital mechanics such as me, the answer should ...
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### GMAT Lambert problem

I would like to plan a mission in GMAT to a certain asteroid, whose orbit and SPK file I have added in GMAT. However, I don't know how to solve the Lambert problem in it to first find the intersection ...
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### Is it possible to easily change the inclination when using momentum exchange tethers?

Access to space using Momentum exchange tether (like Skyhook, Space elevator,...) is economical, but only to specific orbits. And changing the inclination of the orbit is very uneconomical. Is there ...
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### Does an interplanetary trajectory exist to escape the Solar System and impact the Sun "simultaneously"?

This question is inspired by Do you need 0 km/s velocity to crash into the sun? which brings up the peculiarity (at least to the layman) of Solar System escape from 1 AU taking less $\Delta V$ than a ...
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### Is it possible to have a closed(-ish) natural motion circumnavigation around an eccentric target? If so, what parameters define the NMC orbit?

Natural motion circumnavigation (NMC) is when a chaser spacecraft is set in an orbit similar to a target spacecraft's such that the chaser naturally circumnavigates the target spacecraft as a result ...
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### Calculating downrange and crossrange distance and velocity relative to a surface point

I've started to go about implementing a descent guidance algorithm I found in a 1997 paper by D'Souza. However, I've hit a snag. The coordinate system is in terms of downrange position ($x$, relative ...
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### Could Kessler Syndrome be used to control the temperature of the Earth?

Imagine launching a bunch of tiny reflective particles in orbit. This would reflect sun away from earth. Based on the orbit, you could have a swarm only go over certain parts of the earth. Or only ...
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### Whats the time dependency of r and angle in Hohmann transfer?

Reading Bate Muller White and trying to find time dependency of angle and distance of Hohmann transfer orbit. Basically I'd like to plot how the vehicle flies from earth to mars and where it is in ...
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### Testing astrodynamics software [closed]

As I’ve been developing my own solutions (and implementing existing ones) to problems in astrodynamics to solve textbook questions and to build applications, I’m becoming increasingly interested in ...
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### Issue in orbit propagator with wmm2020 output

I am trying to build an orbit propagator with input of latitude and longitude in wmm2020 to plot the magnitude of the geomagnetic field. The orbit seems good but the field plot is completely wrong. ...
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### Where does this formula for the argument of periapsis come from?

I was looking at Poliastro/Hapsira python code determining orbital elements from the position and velocity vector. On this line, argp or $\omega$ is determined as (...
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### After a spacecraft departing from the ISS has performed its deorbit burn, what is the altitude at the perigee of its elliptical orbit typically?

I am attempting to quantify how aggressively returning spacecraft reenter the atmosphere. There is likely a trade-off between aerobraking more gradually and splashing down accurately. I'm hoping that ...
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### Does earth's revolving around sun affect polar orbit ground track?

As the earth revolves around the sun, does the ground track of a polar orbit change? I realize the oblateness of the earth causes precession of the nodes, I want to know if there's another effect. As ...
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### Why my calculations for the eccentric anomalies at the start and end of an interplanetery transfer seem to be off?

For a game, to determine an interplanetary transfer I have implemented the method from here. Using the data for their example problem, I get the result with the lowest $\Delta v$ which appears ...
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### Using Mars' inner moon Phobos as a brake

In case of a StarShip (but it could be any other lander), it would arrive a Mars with minimal fuel remaining and it would need to slowdown for reentry, how can it be slowed down for free? Maybe using ...
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### How exactly would nuclear thermal or nuclear electric propulsion enable short duration human missions to Mars?

Today (May 1, 2024) NASA Administrator Bill Nelson testified before the House Science, Space, and Technology Committee that nuclear thermal propulsion would enable us to go faster to Mars. He said: ...
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### Using Orbital Rings to Achieve High Escape Velocity

Hoping an astrophysics-calculation-competent person could help confirm this scenario: Say civilization has established an orbital ring around the Earth with an external launch track (using super-...
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### Is it possible to change a satellite's eccentricity without changing semimajor axis (instantaneous maneuver paradigm)? What else needs to "give"?

I've been wondering whether it's possible to change a satellite's eccentricity without changing its semi-major axis. (I'm assuming instantaneous changes in velocity.) At first I thought that this ...
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### What is the order of magnitude of perturbing forces in a lunar orbit in relation to the orbital altitude?

Although there are many sources that compare the magnitude of perturbing forces in an Earth orbit (see for example the answer to this question), I haven't been able to find the same information for ...
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Wikipedia informs me that In astrodynamics and celestial mechanics a radial trajectory is a Kepler orbit with zero angular momentum. Two objects in a radial trajectory move directly towards or away ...
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### How to calculate the ascending and descending node, as well as the true anomaly

I have the argument of perihelion, semi-major axis, eccentricity, inclination and mass. I have tried to look this up but get conflicting answers. Any help would be appreciated. (Edit) One physics ...
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### How to determine Euler parameters?

I have two questions and I can't solve the second one. Here it goes: Question 1 Consider a normalized system of units where µ = 1, Earth radius = 6378.165 km is the length unity, and T = 806.81 s is ...
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### How to apply primer vector theory to trajectory optimization under perturbed two-body problem?

I am currently reading the book Primer Vector Theory and Applications by John E. Prussing (https://doi.org/10.1017/CBO9780511778025) to learn primer vector theory. However, all the derivation and ...
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### Will there be a controll mechanism to keep spacex starship in a controlled position during coasting and/or reentry?

Looking at the really interesting imagery from Starship Flight 3, it is obvious that Starship is rotating (tumbling-ish) during coasting, and also during the initial reentry phase. The plasma streaks ...
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### Integration of Varying Forces, Impulses in Simulators

I am a software dude working on a personal project for building a spacecraft simulation software. And I've been looking into numerical integration methods, and I am just confused on how to tackle the ...
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### Does the dawn-dusk orbit maintain the inclination with respect to the ecliptic plane?

I'm trying to understand the mechanics of sun-synchronous orbits, specifically the dawn-dusk orbit. If I understand correctly, the RAAN rotates around the plane of reference of the Earth, which is the ...
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### How to calculate a Hohmann transfer when the target is moving retrograde

Exactly as the title says. I have two objects, both in circular orbits, and with the target object in a higher, retrograde orbit. How do I modify the Hohmann transfer formulae to find the angular ...
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### Orbit Determination from Position and Velocity

I'm working on a game, somewhat similar to KSP (no building rockets, just beautiful orbital acrobatics). It's in a "small" star system, radius of 6 AU, and it features celestial bodies ...
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### Hawkeye 360 Triangular Formation Flying Design

I recently chanced upon the paper Making the Invisible Visible: Precision RF-Emitter Geolocation from Space by the HawkEye 360 Pathfinder Mission (32nd Annual AIAA/USU Conference on Small Satellites) ...
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### At which direction do you apply thrust to perform an inclination change maneuver?

Assume that the vehicle is already at the orbital node. No combined plane changes are included. At which direction is the thrust applied to do an inclination change maneuver? So far, Google hasn't ...
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### Change in True Anomaly over time

From Wikipedia, the True anomaly is defined as the angle between the direction of periapsis and the position of the celestial body. I'm trying to find how the true anomaly changed over time for a ...
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### Orbital Pathing Question [duplicate]

I have seen nearly all orbital 2D projections done like a sine wave. However, when I watch a launch from say, Cape Canaveral, it always "appears" that they are launching due east rather than ...
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### Why are orbits around a black hole not elliptic?

Most of the pictures of a black hole are like this: Source: https://cdn.mos.cms.futurecdn.net/HsDtpFEHbDpae6wBuW5wQo-970-80.jpg.webp Why are the orbits around it not elliptic? Is there any other ...
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### Why does everyone say that it is better to launch a satellite into polar orbit from the pole than from the equator?

If the Earth were spherical, I would agree with this. But the Earth is not spherical. And at the equator, the radius of the Earth is 21 km greater than at the poles. By convention, the altitude of the ...
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### What Δv is needed to reach LEO from a space elevator?

In two recent questions about space elevators, the topic of reaching non-geostationary orbits came up, particularly the popular Low Earth Orbits. This question is simply about how hard exactly it is ...
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### Propulsion options for orbital transfers after release from space elevator

In a recent discussion of cost estimates of hypothetical space elevators it was mentioned that a space elevator is (obviously) well suited to bring payloads to a geosynchronous orbit while reaching ...
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### Has propulsion utilizing solar sail / drag effects of solar panels achieved orbital rendezvous? If yes, is there any utility for clearing space junk?

It has been proposed to use solar panels as solar sails and drag control by alternately feathering panels during different phases of orbit. It is claimed this can alter light pressure and drag enough ...
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### What is the current state of the art in converting between mean and osculating orbital elements?

I want to implement algorithms to convert from mean to osculating elements, and vice versa. I've been digging through Vallado's text (fourth edition), and under ...
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### What can one do as an individual to help support the development of skyhooks?

In my recent research on the potential of a SkyHook, I've found a startling gap: it seems like no one is actively pursuing this technology. Many, including myself, believe that this could be the ...
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### Is this depiction of a Z-Bar docking approach accurate?

I am writing a document about orbital mechanics am trying to depict the different docking approaches in a simple way. Since I am using paint.net to draw the pictures, my drawings are not that great. ...
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### What is the delta V required to access a polar lunar orbit?

The general reference figure (I use) for entering a low lunar orbit (polar included) is ~900 m/s, which is roughly what was set out in previous questions. However NASA released this white paper which ...
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The James Webb telescope is parked in a halo orbit around SEL2, beyond the Earth's umbra, to avoid solar eclipse by Earth or Moon. Is there anything else which could shade JWST?
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### How would one identify ionic thrust vs chemical thrust in an orbit transfer?

My nomenclature might be a bit off, I’m no expert but I’ve been reading to solve the question all the same. Say we detect an orbit transfer based off ephemeris records. We can get the 6 classic orbit ...
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### MATLAB Simple Elliptical Orbits with J2 perturbation and drag

For some reason I need to build a Elliptical Orbits satellite dynamic model by myself, in here I am using MATALB. The model its fine before (I think the J2 effect part works well) I add drag effect on ...
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### Would the Earth still precess if it were an ideal sphere?

I am trying (unsuccessfully) to acquire an intuitive understanding of planetary precession. Is Earth’s precession Torque-free Precession due to its asymmetry as per https://en.wikipedia.org/wiki/...
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### Can a meteor shower have a period of less than 1 year?

This question is inspired by the SE question Can a meteor shower have a interval greater than 1 year? Most meteor showers repeat yearly (or natural multiples of 1 year). Can a meteor shower have a ...
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