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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Interpolating precise ephemerides of GPS satellites

My objective is to obtain at least a sub-meter position accuracy by interpolation of the GPS ephemerides. There is conflicting research outside, where some authors state that a simple Lagrange or ...
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How long does the SYLDA fairing stay in orbit after deploying?

For dual-manifest missions, Ariane 5 often uses the Système de Lancement Double or SYLDA system to encapsulate the lower of two stacked satellites. It can be seen in the following image encapsulating ...
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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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SpaceX 2nd stage or tumbling satellite? WSW to NE over FL

Around 2040 EST We viewed an irregularly flashing object flying from WSW to NNE (roughly) from Jacksonville FL. Is the SpaceX 2nd stage still up there and if so, would it be tumbling and visible? Is ...
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Understanding formula for geocentric position of Moon

I am trying to understand a basic formula in a Celestial Mechanics reference. The formula is for the position of the Moon in a geocentric frame. The reference claims in line (981) that this should be ...
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How can I plot satellite's trajectory from three different TLEs to detect any deviation on path with time?

I have obtained TLE information of a satellite from space-track.org for three different times. I am trying to study any deviation of the satellite trajectory from its usual path. Here I am comparing ...
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Is there a general relativistic relativistic rocket equation?

I am not to familiar with rocket equations but I know that if you combine special relativity with classical mechanics you get "c" as a speed limit. Basically the closer you get to "c" the more you ...
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Algorithmic methods or techniques to find conjunctions in large ensembles of state vectors?

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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Did Rosetta improve on models of non-gravitational effects on comet 67P's orbit?

Question: Since the presence of the Rosetta spacecraft near comet 67P allowed for a detailed mass measurement, extremely precise position and velocity determinations, and physcal measurement and ...
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Orbital insertion with “inertial parachute”?

Inspired by Is there any way to land a rover on the Moon without using any thrusters?, but off-topic as a solution as that question asks specifically about crumbling zones. The idea: A spacecraft ...
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Software for orbital sketches

I am looking for recommendations on software that can create orbit sketches such as the image below. Adding an informative sketch to an article can help readers better understand the idea. I am ...
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Is the Parker Solar Probe's semimajor axis being so close to that of Mercury's just coincidence? Does it help somehow?

Parker Solar Probe will end up in it's Sun-kissing orbit though a series of Venus flyby's, which roughly pins Parker's aphelion at Venus's semimajor axis or about 108 million km. Its final perihelion ...
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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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Were the Apollo lunar ALSEP transmitter signals ever analyzed or used after the experiments were shut down?

This answer to the question Why were the “perfectly functioning” seismometers placed by Apollo 12, 14, 15 and 16 astronauts all shut off in 1977? links to a NASA News Release No: 77-47 dated September ...
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Small-bodies landing strategies

Looking at past landing missions on small bodies such as Eros, Itokawa and 67P I found different landing strategies Eros: NEAR Shoemaker probe performed 4 impulsive pre-planned open-loop maneuvers to ...
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Locally optimal control for low thrust transfers with J2 and other Earth perturbations

Background As detailed in this answer low thrust optimization is subject of ongoing research. There are a few closed-loop control laws which allow to achieve a locally optimal (but close to globally ...
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Solutions to a “Lambert's problem in velocity”

Lambert's problem (also here and here): $$\mathbf{r_1}, \mathbf{r_2}, t \rightarrow \mathbf{v_1}, \mathbf{v_2}$$ was solved by Johann Heinrich Lambert via Lambert's Theorem (see references below). ...
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How to calculate if a co-location intercept is possible in a ballistic counter-battery scenario

Let us presume that we have a scenario with ballistic objects. As an example, one object $m_1$ is launched at time $t_0$ from Earth Location $a$ towards Earth Location $b$, both of which are in the ...
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Laplace Method for Orbit Estimation

I have a question about Laplace angle-only method for orbit determination where the line of sight vectors are being interpolated. I read somewhere that the method fails (due to a matrix being singular)...
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How to get lunar L, B, C parameters from the Moon's 3x3 rotation matrix from the Python package Skyfield?

Answers to What are the “Moon L, B, C” angles shown in this solar eclipse simulation? explain that L and B (or "l" and "b") are the "selenographic coordinates of the Moon's apparent center" (latitude ...
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Where can I find data on satellite orbits?

I'm an enthusiast who'd like access to satellite orbital data to simulate / plot trajectories of manmade satellites (of any kind) on my home computer. Where's the best place for me to find this kind ...
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How much harder would space exploration be if the Earth rotated like Uranus does?

Let's say the Earth got knocked a bit silly in the distant past and somehow space-loving life evolved on this planet. They roll around on an Earth with an axial tilt of 98°. How much harder is it for ...
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Analytical treatment of relative positions between satellites?

I have been searching the internet for estimation of relative position between two satellites. However, all sources seem to be pointing to methods used for proximity operations, where the math ...
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Solar system galactic velocity vector relative to ecliptic plane

The Solar system moves through the Milky Way galaxy with velocity of 230 km/s. The ecliptic plane is located ~60 degrees with relation to the galaxy plane, according to this source. The page also ...
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What is known about the trajectory of J002E3 (Saturn V IV-B stage of Apollo 12)?

This answer taught me about J002E3, an object detected in Earth orbit in 2002 that is assumed to be the Saturn V IV-B stage from Apollo 12. It's trajectory through space is fascinating: (source) ...
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Good example of early and simple orbital mechanics?

I am doing a talk on Katherine Johnson at my school extremely soon and I was wondering if you could give a relatively quick example of a simplified calculation in any kind of orbital mechanics ...
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Interplanetary Taxi Orbit

I would like to know the feasibility of an interplanetary "bus" or "taxi" which moves between, say, Earth-Mars or Earth-Venus without entering the orbit of either. The idea is that the taxi is large--...
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Trivial lower bounds for single point mass delta-v problems?

Given two arbitrary elliptic orbits around an ideal single point mass, there will always exist a transfer with the minimal $\Delta v$ required. It's easy to find an upper bound for this ideal ...
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Just how record-setting was the launch-to-docking time of the April-4-2019 Progress resupply mission?

Digital Trend's article 3-plus-hour supply trip from Earth to International Space Station breaks record mentions that this was even faster than the typical "fast-track" Russian launch-to-docking time ...
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Proper handling of terminal guidance of finite burn closed-loop execution for rendezvous conditions?

I'm writing some software which uses Optimal Control Theory / Calculus of Variations / Pontrayagin's Minimum Principle / Primer Vector Theory to do closed-loop execution of finite burns (in KSP). ...
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How will the Lunar Gateway go to L2 and L1; how much delta-v is needed?

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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Variation in Earth's aphelion and perihelion

I see from Astropixels.com that Earth's aphelion and perihelion each vary by a little over 29,000 km, while the earth-moon barycenter wobble is about 4,000 km. Is Astropixels.com correct? Are Jupiter ...
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(How well) Did Juno provide any insight into the Flyby Anomaly?

I ran across an old BBC article titled Juno: The spacecraft putting sling theory to the test — Why a probe passing our planet on its way to Jupiter might end a decades-old mystery, and reveal ...
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Differential Equations for Rocket Launch in Polar Coordinates

I'm trying to understand the equations of motion for a rocket launched from earth, through the atmosphere, and into LEO. I found a set of ordinary differential equations which describe the motion of ...
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Are ion thruster trajectories classified as brachistochrones?

Usually, when performing trajectory optimizations for chemical rockets, the limiting factor is the $\Delta v$ budget. That means velocity change is the optimization factor, with things like transfer ...
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Resonances and the seven sisters recently discovered

In reference to the discovery of seven planets around Trappist-1, I'm just wondering if any of these planets are in an orbital resonance and if that is the case, what the implications for habitability ...
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extreme longevity of geostationary orbits

I was speculating that geostationary satellites could be around possibly for billions of years (i.e. much beyond the point where plate tectonics would have erased all traces of human civilization on ...
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How does a butterfly orbit move in 3D? Way to generate or visualize?

The paper Earth-Moon Near Rectilinear Halo and Butterfly Orbits for Lunar Surface Exploration (AAS 18-406) says Periodic Orbits in the Earth-Moon System The current investigation focuses on ...
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Could a solar sail composed of smart glass stay near the L1 point of Venus?

From answers to this question i've learned that the Lagrangian L$_1$ point of Venus is not stable, despite the almost circular orbit of the planet and the fact that it has no moon. Nevertheless would ...
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Delta-v cost of longitudinal plane change correction?

In a recent question, the slow drift of a landing site on a rotating body relative to an orbiter came up. This would sometimes require a plane change correction when one desires to recover the ...
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Mean to Osculating conversion for non-J2 averaged elements

What is the appropriate technique to convert mean elements (true anomaly averaged) into osculating elements when the model has J2, SRP, drag and additional forces modeled. Brouwer's transformation is ...
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How accurate can a point in space be determined by the likes of the ICRF?

How accurately could a 3D point in open space (i.e. not on an object), say at an elevation of 30,000m above sea level, be located or modelled using the likes of the International Celestial Reference ...
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Transfer between circular orbits in up to 5 maneuvers

There are 2 circular orbits with different inclination and RAAN. I have to transfer from a specific point (true anomaly given) of one orbit to a given point of another in 1 month. The period of the ...
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Is the Gateway's halo orbit bound to Earth? Would the Gateway remain in Earth orbit of the Moon disappeared?

Discussion below this answer involves my feeling that calling halo orbits in very asymmetric systems (e.g. Sun-Earth or Earth-Moon) as orbits around the primary, in 1:1 resonance with the secondary. ...
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Can we calculate elliptical properties in a spherical coordinate system?

Can we calculate the elliptical properties like the semi-major axis and eccentricity using the state vectors (position and velocity) in the spherical coordinate system? http://www.braeunig.us/space/...
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How do I calculate re-entry velocity when decaying from a circular orbit?

I am trying to find the velocity of an object during re-entry so that I can calculate the peak heat flux but I'm a bit stuck. I know how to find the velocity of the original, circular orbit (300km) ...
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How do I calculate the change in the argument of periapsis after a plane change maneuver?

Let's say I have a spacecraft in an initial geocentric orbit with the following parameters: a = 7,960,000 m, e = 0.010, $\Omega$ = 180$^{\circ}$, i = 98$^{\circ}$, $\omega$ = 90$^{\circ}$, $\theta_0$ =...
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Which two spacecraft have spent the longest times in libration point orbits? (Lagrange points, Halo, Lissajous, etc.)

Libration point orbit is a general term including halos, Lissajous', and a whole zoo of others associated with Lagrange points in three-body systems. Which two spacecraft has been in such an orbit ...
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Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v to move from one to the other?

This answer discusses a spacecraft in GEO using a two-impulse (circular → elliptical → circular) raise & lower maneuver to move (phase) itself by 180 degrees in longitude then return to synchrony. ...
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How would propagation differ between a GEO and a Retrograde GEO?

A Binary Equatorial Synchronous Retrograde Orbit is an orbit that would travel in the opposite direction of GEO and would pass over the same point on Earth twice per day at the same altitude of GEO. ...