# 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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### What is $\theta_{GMT}$?

What is $\theta_{GMT}$?, and how do you convert this into time and angle? I found this article, but I don't think it's exactly what I'm looking for. http://www.cs4fn.org/mobile/owntimezone.php
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### How are B-Plane parameters actually determined for a planetary flyby?

Reading from this document, I am trying to simulate the New Horizons probe trajectory in GMAT and I am puzzled with how the authors of the original paper (by legendary mission designer Robert W. ...
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### Calculate distance to Sun

At Cornell University's Ask an Astronomer I was reading How can I find the distance to the Sun on any given day? (Advanced) and it mentioned you can find the distance to the Sun on any day of any year ...
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### Analysing a phasing maneuver using GMAT- how do I reliably quantify their "phase difference"

I am trying to recreate a phasing problem that was solved on paper the previous semester, and verify my solutions using GMAT. Two identical satellites are released on a 550km sun-synchronous orbit by ...
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### Gravitational force of asteroid Bennu

How can the gravitational force of Bennu (being so weak) hold the spacecraft in orbit?
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### Calculating specific dates of reaching apses given orbital elements?

Given a specific date and heliocentric orbital elements ($a, e, i, \Omega, \omega$, mean anomaly) of a spacecraft in a heliocentric orbit, how can we calculate when it will reach perihelion and how ...
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### Thrust value for space mission from Earth's orbit to Venus' orbit

If I had to take a spacecraft from Earth's orbit (400km above earth) to an orbit around Venus (6151km X 50,000km elliptical orbit), how much thrust will I need. Delta V is 5km/s using hohmann transfer?...
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### What is the highest number of impulses required for an optimal orbital transfer?

Given two arbitrary orbits around a point mass, there exists some optimal transfer between them in terms of delta-v. What's the highest number of impulses such a transfer could require? (That is, I'm ...
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### Are ECI and ECEF both frames and/or coordinate systems? Is there a difference?

I don't know really know the difference between a frame and a coordinate system. I'd proposed ECEF and ECI tags, do we need them? Frames seems to be the standard in meta but there is concern so any ...
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### Satellite tracking telescope integrated program in Matlab

How can I get a comprehensive, integrated MATLAB program to set up and capture SGP4 output for telescope mounting? I am currently receiving state vectors from the SGP4 program, which include the ...
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### Magnetometer in space

See, i recently buy a magnetometer to experiment with arduino, i want start building a litle fly computer for a cubesat (this cubesat have an ion engine, so, have thrust). I start reading the Azimuth ...
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### Land a cubesat on the moon with ion engine

Say I have a 3U cubesat with a BIT-3 ion thruster, an iodine tank and landing legs. Can it land on the Moon with just an ion thruster?
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### Calculating Orbital Velocity without Semi-Major-Axis

When playing Kerbal Space Program, I realized that there is a difference between surface speed and orbital speed; this difference is quite variable, although the Kerbin's surface speed is only 175 m/s....
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### How to determine the delta V required in order for the satellite at pt. A to hit the earth at pt. B?

I'm confused about how would I go about obtaining delta-v in this case. I'm aware of orbital transfers such as bi-elliptical but that is not the answer to this. Kindly help
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### What would be the influence of nearby planets on a Dyson sphere or Dyson swarm?

Considering orbital mechanics, I would like to ask what would be the effect of nearby planets such as the Earth or Jupiter on a Dyson sphere. A Dyson sphere is not realistic because of the tremendous ...
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### Is this plot of deep space trajectories correct? Did most launch retrograde from Earth? Why do some change direction between planets?

This answer contains some nice plots of deep space spacecraft trajectories. Noticing that Voyage 2's heliocentric velocity dropped substantially just before 1990 I wanted to see why. Wikipedia's ...
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### How can we express velocity of the Apollo mission relative to a moon-centered reference frame instead of an inertial reference frame?

I am really interested in the Apollo mission and I was wondering how fast did the astronaut pass by relative to the moon. I wanted to compare it with the speed of the car. I have been able to ...
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### Travel time from lunar orbit (EML2) to Jupiter using skyhook only?

I am doing background research for a science fiction story, and hoping someone can help with this navigational question. Voyager 2 reached Jupiter from Earth in about 2 years. However (if I understand ...
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### How much delta-v have I used here? What's the "official" equation for delta-v from parametric thrust?

I took a break from Stack Exchange, jumped in my spacecar and flew the following squiggle: $$a_x = \cos(10 \ t)$$ $$a_y = \sin(5 \ t)$$ $$a_z = \cos(2 \ t)$$ starting at ...
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### Why is "delta-v + $\sqrt{{v_E}^2 + C_3}$ where ${v_E}^2 =$11.19 km/s" the correct way to calculate total propulsive delta-v? Please show all work

There is one answer to What spacecraft has had the greatest total propulsive delta-v? and I can not understand how its numbers have been calculated. Response to comments does not seem forthcoming so I'...
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### Tools for high-thrust trajectory optimization

I've tried using some of the freely available tools for making pork chop plots to explore the potential of transfers between planets. But as far as I can tell, these really are not designed for and do ...
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### Does mass of orbiting body affect the orbital speed? [duplicate]

Does mass of orbiting body affect the orbital speed? Suppose if Moon is at same distance from Earth as International Space Station. Would Moon's orbital velocity change? Also secondary question, ...
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### Do I have enough info to find the true anomaly of an orbit?

For a personal coding project, I'm trying to model orbits of satellites around the Earth. I take in some values from a user and use them to determine the shape of the orbit. I want to model the ...
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### What is the closest polar lunar orbit that can be sustained? What are the limiting factors on closest approach?

I'm wondering how close a lunar orbit can get at periapsis to the south pole. I want an orbit that is sustainable for at least ~20 orbits. I'm working on a small sat concept for studying the lunar ...
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### What does a low thrust apoapsis raising look like?

Say you are in a simple circular orbit, $r = 1$ and want to raise your apoapsis to some higher altitude, say an orbit $r_P = 1, r_A = 2$ A high thrust spacecraft would to this in one impulse, at \$\...
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### How to create a satellite intersection/conjunction in GMAT?

Starting to learn GMAT. I've been able to get my satellite to move around in space pretty well with various targets and maneuvers in the mission sequence. Now I would like to have my satellite target ...
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### Soyuz/spacecraft deceleration speed for reentry

I recently saw a program by Prof. Brian Cox (Human Universe Ep.1) where he mentioned that just by using two equations - f=ma and the universal law of gravitation, you could calculate how much a ...
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### Range of travel time between particular planets using the Interplanetary Transport Network/Interplanetary Superhighway?

I understand the Interplanetary Transport Network allows for travel at low speeds between different planets in the solar system using very little energy. Is there flexibility in how long it would take ...
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### Phasing maneuvers; methods to travel between satellites with very similar circular orbits

If you imagine two satellites orbiting earth, each in a circular orbit in the same plane and at the same altitude, but varying in their angular position, the simplest way in my mind to travel from a ...
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### J2000 to current ECI transformation matrix

I want to find the transformation matrix that converts an ECI frame at some time 't' (lets say t = 1st January 2020) to J2000 ECI frame (that is ECI frame at noon of 1st January 2000). From what I ...
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### What altitude would an aphrodiosynchronous satellite need?

A geosynchronous orbit has a period of 24 hours, and mostly stays over the same location on the surface of the Earth. According to this blogger, the equivalent term for Venus should be "...
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### Why was Voskhod 1 at an inclination of 64.7° degrees while Salyut 6 launched from the same latitude was at 51.7°?

This answer to Have any Soviet-era astronauts reported seeing Earth's aurora or related luminescent atmospheric effects? mentions sightings from both Salyut 6 and Voskhod 1. While Salyut 6 orbited for ...
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### Have people in orbit ever been bothered by the difference between their orbit and the station's?

When floating inside a large space station, while away from its center of mass and without touching the structure of the station, the person floating and the station will have slightly different ...
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### Maneuver in the intersection of 2 orbits

The spacecraft transfers between two co-planar orbits. The initial orbit has the Ra = 2000km, Rp = 600km and ...
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### Who invented the sun-synchronous orbit?

I was explaining sun-synchronous orbits to a co-worker and he asked me who invented it and when. I could not find an answer on wikipedia or a quick google search, so I thought about asking here.
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### How many times will the Photon fire its Curie in order to "reach the right spot" to deploy CAPSTONE towards the Moon?

note: it's been a year and a half and Capstone is scheduled to be launched soon, so perhaps there is more information available now? The Verge's How small launcher Rocket Lab plans to pull off its ...
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### Satellite inclination, 3D scanning of earth's surface

Has any attempt been made to change the "plane" of the orbit (not altitude) of a satellite, across earth's diameter, continuously in small steps, from pole to pole for a satellite with zero ...
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### Does the Earth's orbiting the Sun influence spacecraft in Earth's orbit?

As I try to comprehend how spacecraft are able to stay in orbit around the Earth I began to think about why the Earth's own orbit around the Sun does not influence spacecraft in Earth's orbit. I came ...
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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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### Optimization of low-thrust in-plane maneuver

I have to build an optimal trajectory between two orbits, which are in one plane, but with different semi-major axis, argument of perigee and eccentricity. I've read different articles regarding the ...
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### Why do rockets coast before secondary payload deployment?

I was watching a falcon 9 launch. After SECO, stable orbit was achieved and the primary payload was deployed. The 2nd stage coasted for an hour (no burns in between) and then deployed rideshare ...
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### Earth's Axial Precession and Frame Change [duplicate]

Is Earth's Axial Precession and change in Axial tilt values significant enough to be considered while writing Rotation matrix that converts Body frame into ECEF frame and also while propagating Orbit ...
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### Why will OGO-1 reenter from an elliptical orbit rather than circularize first?

According to all the sources cited in Why does OGO-1's trajectory and imminent reentry come from sky surveys and NEO tracking rather than normal satellite tracking? OGO-1 is in a highly ...
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### What is the simplest way to determine if two or more TLEs describe two or more satellites in lead-follow?

If two more more up to date TLEs have same inclination and the same period they are in the same orbit, but how do I check if they are also following each others path, in a train?
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### Apparent Centering Problem When Using the Perifocal System to Draw Orbital Ellipses

I am attempting to render orbital ellipses in software. Given a set of orbital elements, I am using the Perifocal system to determine a set of points along the curve of the ellipse. I am using the ...
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### Does the Newton-Rhapson solution to Kepler's equation diverge?

I have the following simple solution to the Kepler's equation which uses newton-rhapson iterative technique. I have read various papers about the initial guess and divergence near an eccentricty of 1, ...
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### Error in Propagating equatorial orbit using GMAT

I propagated an orbit with semi-major axis of 7000km and the rest of the keplerian orbital elements 0 on GMAT. Since the orbit is circular and in the Equatorial plane, it should not change over time. ...
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### How to calculate the local maximum solar radiation on Mars from day to day throughout a full martian year?

I would like to know where on Mars the least lowest daily temperatures depending on the time of year will be. At first glance one might think, as I did, that it has to be along its equator, but ...