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Orbital mechanics or astrodynamics is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.

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With what speed goes Phobos in the direction of Mars with a constant force in that direction?

Edit: Although this question may look similar to this one, here I am asking about a constant force in the direction of Mars, and no one of the answers there have answered this question. Because ...
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1answer
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What is the eccentricity of a near equatorial LEO?

I am trying to do some calculation on the 2-body problem but I am stuck as I need either the eccentricity or the periapsis of the orbit. I already have the orbital period which I assume as ~127 min as ...
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Can 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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33 views

Low arrival V-infinity?

So I am modelling an Earth - Mars low thrust trajectory in a simple manner. I'm telling my model to not model any trajectories where the spacecraft is moving any more than 200 m/s quicker or slower ...
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How will the Lunar Gateway go to L2 and L1?

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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1answer
83 views

How to determine an orbit of a satellite for a collision detection?

I'm trying to validate an collision detector , and for that I'm starting from a pair of initial conditions for a satellite.After that I will use an RK method to integrate . How can I determine a pair ...
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488 views

How is a Russian satellite's behavior “very abnormal”?

The BBC has a news article saying: "Mystery Russian satellite's behaviour raises alarm in US". But the article doesn't say how or why the behavior is "abnormal". And the linked transcript of Remarks ...
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1answer
94 views

Relativistic effect on satellite motion

I am using GMAT to propagate satellite motion. At first, I excluded all the propagators besides harmonics(of second degree and 0th order, as shown in the picture): Here are the results(...
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85 views

What is the timespan for a block from Phobos to reach a low orbit around Mars with a solar sail?

Edit: Although this question is marked as a duplicate of this one about solar sail thrust calculation, they are different because I ask about a solar sail that has an orbital trajectory and will have ...
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90 views

In what way(s) is OD (Orbit Determination) “an art”? [on hold]

A recent comment includes the following: As my professor of OD would say "orbital determination is more of an art than a science." and was also referenced in chat: But OD is really an art, as ...
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2answers
65 views

Onboard propagator in satellites SGP or J2

The Earth orbit propagator SGP4 (simplified general perturbation) was developed by NORAD to allow users to generate short-term prediction of satellite positions using two line element sets (TLEs) ...
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1answer
166 views

Apollo 10: Where's Snoopy?

During the Apollo program, we launched a total of 9 Lunar Modules (LM's). The Ascent module from Apollo 10, or "Snoopy," is unique in that it was neither deliberately crashed into the Moon (Apollo 11, ...
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67 views

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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Algorithmic methods or techniques to find conjunctions in high N state vector 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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0answers
22 views

How to specify constraints for launch windows

I'm trying to learn trajectory design and optimization, and I'm struggling to understand how one determines the launch window using trajectory design programs. I know that my satellite's initial ...
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2answers
79 views

Could the Lunar Lagrange Points work for space telescopes?

Every orbit in space has its pros and cons. Low Earth Orbit has accessibility but frequent eclipses whereas a Solar Lagrange Point is clear and stable but distant. In the case of the Lunar Lagrange ...
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1answer
56 views

JGM-3 vs EGM2008 coefficients

I've implemented the Earth harmonics calculation in JGM-3 model, using the coefficients from here ...
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2answers
3k views

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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3answers
223 views

How does the Parker Solar Probe have such a wide launch window?

The Parker Solar Probe is set to launch on August 11th 2018. It will perform 7 orbit-lowering gravity assists around Venus for ~6 years before reaching its final operational orbit. It has been well ...
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1answer
136 views

How does the ISS Transit Finder website get the position of the ISS so accurately?

The recent Petapixel article How to Shoot the ISS Flying Across the Face of the Moon gives a lot of detailed, helpful advice for photographing transits of the ISS across the disk of the Moon. For ...
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2answers
69 views

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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96 views

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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0answers
40 views

Calculating t(E)

The mean radius vector of an elliptic orbit is equivalent to the semi-major axis. If I sample the radius vector of an unperturbed elliptic orbit as a function of the eccentric anomaly with at a ...
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44 views

Software (besides Ltool) to simulate CR3BP (three body) problems?

Are there any other softwares for CR3BP besides Ltool? As I've learnt here Ltool is not generally available to the public. I would like to simulate three body orbits within the standard circular ...
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38 views

Why would ISRO's MOM-2 Mars orbiter mission's apoarion already be decided in such an early call for proposals?

ISRO's announcement Announcement of Opportunity (AO) for future Mars Orbiter Mission (MOM-2) says in part: It is now planned to have the next orbiter mission around Mars for a future launch ...
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0answers
49 views

What is optimum data interval algorithm for Orbit Determination?

I am trying to find Optimum data interval algorithm for orbit determination. Because in Leo, Geo orbit updates the measurement data can be different so that I want to implement an optimum data ...
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1answer
86 views

Using of the coordinate systems in orbit propagation

For the orbit propagation in ECI coordinate system, considering the effects of zonal harmonics and Sun/Moon perturbations the following procedure was formed: Convert the state vector to ECEF ...
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1answer
507 views

Elliptical orbits transformed to “equivalent” circular orbit

I'm trying to transform Mars' elliptical orbit into its circular "equivalent". I understand that if the semi-major axis is used as the radius, and the mean angular rate and period are kept the same, ...
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2answers
122 views

Earth geopotential effect on orbit propagation

I'm trying to take into account the Earth geopotential effect on the orbit. The only term I could consider, is J2. Are the terms (J2, etc.) change with time? I ...
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43 views

How can I calculate Mean anomaly from True longitude?

So, I have - TLE data - Reference frame: QMOD - Type: Osculating - Semimajor axis - Eccentricity - Asceding node - ...
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0answers
50 views

variables affect the trajectory in a stochastic way

What are the different variables affecting the trajectory of a rocket in a stochastic way for getting potential three-sigma trajectory?
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1answer
56 views

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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1answer
39 views

What is the planned orbital configuration of Astrocast's planned IoT constellation?

The Space Daily article Astrocast signs contract with GomSpace Sweden to deliver propulsion systems says in part GomSpace Sweden - a subsidiary of GomSpace Group AB, has received an order from ...
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1answer
77 views

Will asteroid 2015 YA have a collision with Venus in october 2018?

When you use the Small-Body Data Browser of JPL Solar System Dynamics and do the search for asteroid 2015 YA, and after that push the [ show orbit diagram ] button, you can see that on october 12, ...
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2answers
112 views

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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1answer
50 views

Comparison of AOP change of the orbits

I'm comparing how the Argument of perigee (AOP) changes for 2 orbits (O1 and O2). The orbits ...
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1answer
125 views

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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1answer
125 views

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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How could asteroid 2013 ND$_1$$_5$ become a moon of Venus with the aid of rocket engines?

Notice: Although this question is similar to this one, it is different because asteroid 2012 XE$_1$$_3$$_3$ has a transitional path between Venus's Lagrangian points L5 point and L3 point, whereas ...
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1answer
114 views

Low earth orbit propagation in GMAT

I'm propagating a Low Earth orbit using GMAT. I 'm trying to make the propagation realistic, considering the zonal harmonics, Sun, Moon, Jupiter, Venus perturbations, tidal forces and solar ...
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1answer
133 views

Could asteroid 2012 XE$_1$$_3$$_3$ become a moon of Venus with the aid of rocket engines?

2012 XE$_1$$_3$$_3$ is an asteroid, classified as near-Earth object of the Aten group that is a temporary co-orbital of Venus. It is following a transitional path between Venus's Lagrangian points L$...
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2answers
124 views

A software for orbit propagation, considering Moon, Sun and zonal harmonics

I have to propagate the orbit of a satellite in 1 year, complying with the Sun, Moon and zonal harmonics effects. Is there preferably a free software, which could be used? I was suggested to use ...
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3answers
221 views

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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1answer
266 views

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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3answers
2k views

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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1answer
177 views

Maneuver to the optimal point of a given orbit

There is a spacecraft on an initial orbit. There is a target orbit. The Keplerian elements are given for the orbits. The problem is: when and what $\Delta V$ to apply to the SC to move it to the ...
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1answer
81 views

If a spacecraft is orbiting around the Moon, what direction would the nadir axis be?

Nadir for a craft orbiting the Earth would be radially in, is nadir always pointed towards the Earth or is it pointed towards the celestial body that the craft is orbiting?
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141 views

Outlier detection algorithm for orbit determination, how do different ones compare?

I have been reading about outlier detection algorithm for improving determinations based on realistic data. Outlier exclusion is an important tool in any analysis of realistic noisy data. There are ...
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2answers
89 views

Is it possible to orbit a black-hole AT the event horizon? [closed]

https://en.wikipedia.org/wiki/Black_hole#Innermost_stable_circular_orbit_(ISCO) ISCO is apparently the current theoretical limit for orbiting black holes (as sourced by wikipedia). Original Question:...
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3answers
643 views

A spacecraft leaves Earth exactly with escape velocity V2 - what trajectory it will have in Solar System?

A textbook solution: if a spacecraft leaves the isolated Earth with escape velocity V2 (=11.2 km/s at Earth's surface) it will have parabolic escape trajectory. But Earth is in orbit around Sun. The ...