# 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 calculate the delta-v correctly, this way does not seem to be correct?

I'm learning about Astrodynamics, and I would like to ask how can I calculate the $\Delta V$ for an interplanetary mission. I used a website for the porkchop plots (http://sdg.aero.upm.es/index.php/...
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### How to calculate drop due to ship docking at orbital tether

I am exploring some of the properties of a vertical orbiting tether (or non-rotating skyhook). This particular tether has a quite large mass at the location with a circular orbital velocity, with the ...
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### Are there any man-made satellites at Lagrangian points?

There are 5 lagrangian points. Are there any man-made satellites at any of those points? Is there a reason for the presence or absence of satellites at these points?
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### How to calculate libration amplitude of objects orbiting the $L_4$, $L_5$?

Is there a way to calculate the libration amplitude of a test object that orbits the $L_4$ or $L_5$ Lagrange points? By amplitude I mean the distance along the orbit between the two extremes of ...
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### The physics behind the Starshade

The Starshade is a space telescope with a large occulter that can fly off and block the light of a star so its telescope can picture the surrounding exoplanets: I ...
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### How far in the future can SGP4 make accurate predictions?

I want to find out how long before predictions for a satellites location made using the SGP4 algorithm break down. For example if I use TLE data from a satellite which was gathered today, how far ...
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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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### Does a change in the rotational speed of something on its own axis (rpm) affect its orbit?

For example: if a satellite in orbit around earth had its prograde rotational speed increased from 60 rpm to 600 rpm, would its orbit be affected? Another example would be if earthās rotational speed ...
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### How could a satellite follow earth around the sun while staying outside of earth's orbit?

I'm wondering if its possible for a satellite to follow earth around the sun while staying outside of its orbit. I wondering for the sake of space based solar infrastructure or just something ...
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### To what extent is the orbital Time Period of ISS affected by soyuz thrusters?

Numerically, to what extent is the orbital time period of ISS affected during the time when it boosts back higher to gain the lost altitude, using Soyuz thrusters/engines?
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### Optimal trajectory for solar electric propulsion?

Consider using solar electric propulsion for, e.g. Earth-Mars trip, or for asteroid retrieval mission. Is there a benefit to first entering an eccentric orbit so that part of the time is spent ...
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### How far away will I get if I'm --just under— escape velocity?

The escape velocity of earth is about 11.2 km/s. Let's say it was, for the sake of argument, exactly 11.2 km/s. If I go 11.199999 km/s, I'm going to fall back down to earth. But how can I determine ...
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### Is there a synchronous orbital height for Phobos?

My assumption is that any body in the solar system would have it's own specific geo-synchronous orbit height. But when I took a look at Phobos and calculated the GEO height based on the simple formula ...
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### What Earth gravity model is used for different types of calculations?

When performing orbital calculations, under what circumstances should I assume: a perfectly spherical Earth a reference ellipsoid a geoid no particular format at all
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### Effects On ISS Orbital Mechanics Resulting From Added Mass Of Dragon Capsule Visit

Does the ISS require any type of orbital mechanics management once the Dragon capsule was confirmed with a positive airlock seal, and the mass of the spacecraft, 2 additional astronauts, and supplies ...
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### How is a satellite constellation launched?

If want 10 satellites chasing each other around the earth (evenly spaced) all one the same plane, these satellites would be evenly distributed around the globe after launch by slightly raise or lower ...
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### Is there free, accurate and updated data on planetary body positions in the solar system?

I'm a software developer and I'm trying to move towards astrophysics. I wanted to create an accurate solar system model using real-time accurate data. I've found the NASA data site, however I can only ...
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### Sending a satellite towards or away from the Sun

I remember reading here that it is more difficult (cost? fuel?) to send a satellite towards the Sun compared to sending a satellite away from it. Is this true? And if it is, how come?
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### What is the highest velocity a spacecraft has left Earth?

The comment below @TomSpilker's answer I'd love to see anything in LEO that can impart 20.89km/s of delta V to anything. got me wondering what the highest velocity a spacecraft has left the Earth,...
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### How did Shepard's and Grissom's speeds compare with orbital velocity?

As is often said here and in XKCD, an orbit isn't merely high up... it's also going fast. The first two American astronauts -- Alan Shepard and Gus Grissom -- did indeed get "high up" enough to ...
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### How stationary is geostationary?

When a satellite is in geostationary orbit, it is supposed to stay above one spot of the earth and rotate around the earth at the same rate the earth spins. But how exact does that equality need to be?...
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### Calculate True Anomaly at future point in time with hyperbolic orbits

Given: Semi Major Axis (negative) Eccentricity (>1) Argument of Periapsis Inclination Longitude of Ascending Node Current True Anomaly Mass of Central Body How can one calculate the true anomaly at ...
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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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### Needed height from the release of a space elevator to get a stable elliptical orbit?

As we know, something released from around 36000 km height from a space elevator will remain in geostationary orbit around the Earth. Things released from lower will go into an elliptical orbit ...
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### How did the Apollo guidance computer handle the Earth-Moon system's rotation around the Sun?

In this comment I just wrote: "...but at all other times it is just doing math to calculate its trajectory." The math needed a stable clock Timing accuracy of the Apollo Guidance Computer? (also 2, ...
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### Terraform via moving Ceres To Mars orbit, using ion drive

EDIT: Apparently the accepted physics has changed, and we now use the convection model for generating planetary magnetic field, not the dynamo model. Next thing you know people will be telling me ...
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### How to determine $\Delta v$ loss due to gravitational pull from earth

How do I find the delta-v loss of a rocket while ascending to its apogee? Specification of Atlas V 541 rocket: Specification for Atlas V first stage: Dry Mass: 21054 kg Fuel and Oxidizer(RP1/LOX) ...
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### Where will objects end up, after losing stability at Lagrangian points?

The Lagrangian points are points of unstable balance (at least gravitationally; L4 and L5 are stable thanks to Coriolis force.), and that means an object not stabilized actively will fall out of them ...
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### Why don't SpaceIL's Beresheet spacecraft and Moon orbits line up?

The question Tracking SpaceIL Beresheet Moon lander links to some data files that are from the site: http://live.spaceil.com (also linked here): Raw data: http://live.spaceil.com/data/data_s1....
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### Are transfers between two orbits commutative?

Are the propellant mass and transfer time from orbit A to orbit B the same as from orbit B to orbit A, considering low-thrust propulsion? That is, in the case of dealing with Keplerian orbit ...
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### Python API for JPL Horizons?

I found the python package HorizonJPL in the Python Package Index, but it looks like it's limited to activity in 2013. When I go to the linked documentation page https://docs.google.com/document/d/...
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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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### Is a sun-blocking orbit possible?

Is it possible for an orbital "sun shade satellite" to have a geosynchronous equatorial orbit such that it is in an approximately straight line between the Sun and a fixed point on the Earth's ...
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### When (roughly) will North Korea's Kwangmyongsong-4 satellite re-enter?

North Korea recently launched Kwangmyongsong-4 but it wasn't entirely successful and is tumbling out of control. I read on a Wired article that āThis thing is probably a failed attempt to get higher ...
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### What is a “Y-Thomson spin”?

I am new in the field of Spacecraft Attitude Dynamics and Control, and came across the terminology "Y-Thomson spin". What is it? Where can I read more about this attitude control mode?
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### How could transfers between SEL1&2 and EML Lagrange points be utilized?

The Earth has 7 Lagrange points nearby since SEL1 and SEL2 (Sun-Earth Lagrange points 1 and 2, respectively) are only between 3 and 5 LD (lunar distances) away from the five EML (Earth-Moon Lagrange) ...
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### Orbital rendezvous with low-thrust engines?

The Hohmann Transfer is clear enough; Accelerate on your (circular) orbit at the right time, raising the apoapsis until it meets the target orbit. Once there, burn again to raise the periapsis - ...
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### Lightsail-2: Increased Orbit from Sunlight or Lowering Periapsis?

Has Lightsail-2 really increased the total energy of its orbit by utilising energy from sunlight, or has it simply exchanged energy by lowering its periapsis in order to raise its apoapsis? And if so, ...
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### What are the effects of orbital reflectors and advertising on scientific observation?

There's a couple of startups and initiatives which are proposing "space billboards" which have been getting a lot of bad press recently. Most of the proposals involve a bunch of cubesats with large ...
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### How does the delta V to reach and orbit L4 and L5 compare to entering orbit around the Moon?

The L4 and L5 Lagrange points, 60 degrees in front of and behind the Moon in its orbit around Earth, orbit at the same speed as the Moon. But when a spacecraft flies to the Moon, the gravity of the ...
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### Does it even make sense to talk about Mercury's triangular libration points (L4, L5)?

The recent question How much radiation shielding would be required for a habitat at MercuryāSun L5? got me thinking. There are a large number of disadvantages and challenges to building or putting a ...
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### What are the “Moon L, B, C” angles shown in this solar eclipse simulation?

The NASA Goddard video Tracing the 2017 Solar Eclipse is a visualization of the calculated shape of the umbra during the upcoming August 2017 total solar eclipse, as it moves across North America. The ...
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### Is it possible to leave the Solar System by repeatedly using gravity assists from the Earth?

If a spacecraft was accelerated to just above Earth's escape velocity, it would begin orbiting the sun with an orbit very similar to Earth's. Could the spacecraft then repeatedly perform a gravity ...
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### Why is Dawn in a much higher observation orbit than Rosetta?

Dawn orbits Ceres at thousands of kilometers periapsis altitude, and doesn't seem to plan to go lower than 375 km. In contrast, Rosetta has been down to about 30 km altitude, and will finally even try ...
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### Orbital propagation: atmospheric drag

I'm developing the numerical orbital propagator. I've already implemented the Newtonian gravity (Earth, Sun, Moon), Earth harmonics, SRP and relativistic effect. The software is compared with GMAT ...
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### Earth polar orbit to Lunar polar orbit

Suppose you wanted to achieve a polar orbit around the Moon, starting from LEO. Would it be better to start from a polar orbit around the Earth? "Better" meaning using less fuel, having more frequent ...
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### Can I use Tsiolkovsky's rocket equation in combination with this equation for a Hohmann transfer to find what mass of propellant is needed?

I'm wondering if it's appropriate to use the two equations in order to solve for m0/m1 to find the mass of propellant needed to perform a hohmann transfer. If it isn't, can someone suggest an ...
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### Hohmann Transfer Equation of Motion

I'm working on a school project on calculating the Keplerian orbital motion of objects and then plotting/animating the trajectories. One feature I want to include is plotting a Hohmann transfer from ...
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### Apollo 15 State Vector recreation

I am trying to get the state vectors for Apollo 15 before, during, and after critical manoevers [sp]. IE TLI, LOI1, LOI2, lunar launch, preocking, postdocking, and TEI. I am a totally newbie at all ...
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 ...