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 is satellite's footprint/coverage calculated?

I was using Orbitron - Satellite Tracking software the other day and I saw that clicking on any of the satellites, you will see their footprint (they are usually not-ideal circles, usually ellipses), ...
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Is it possible to throw a baseball so hard it circles the earth above your head?

Assuming the earth had no atmosphere, and you could throw a baseball as fast as you wanted to, and you were standing on the surface of the earth, is it possible to throw the baseball so fast that it ...
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Why is the re-entry velocity of Orion almost the same as the escape velocity?

I have read that the predicted re-entry speed on the Artemis I mission for the Orion spacecraft into the Earth's atmosphere is about 24,500 mph or 10.9 km/s. Why is it almost the same as Earth's ...
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Largest single burn spacecraft delta-v in deep space?

This 700 m/s maneuver that was avoided got me thinking and then CNN's NASA mission will zoom by asteroid before returning sample to Earth said: "Leaving Bennu's vicinity in May puts us in the '...
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Why would a launch request for a gravitational assist at Mars specify a DLA (Declination of Launch Asymptote) of 30 to 32 degrees?

The recent intriguing question Why is NASA proposing an EMEJ (MEGA) trajectory for Europa Clipper instead of EEJ? quotes "A launch service request... recently put out for Europa Clipper to do a ...
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1answer
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How to know in which quadrant is the RAAN?

Having found the right ascension of the node, for example, $$ \begin{align*} \boldsymbol{\Omega} &= cos^{-1}\frac{N_X}{N} \\ &= \underline{15.60^\circ} \end{align*} $$ How do we know in ...
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How would an n-body numerical orbit simulator use hierarchy in its Jacobian?

This question is about techniques to calculate orbits. The Github post On the dynamical stability of Principia's modified Jool system (cited in this answer) says: Principia computes the trajectory of ...
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Minimum delta V required to return a piece of metallic asteroid 16 Psyche to Earth?

Suppose somebody sent a rover to Psyche 16 and found massive concentrated deposits of platinum-group metals near the surface, and turned it into a 10 ton sphere of platinum/iridium/osmium/gold alloy ...
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rocket trajectory simulation in inertial frame, with drag

I created a rocket trajectory simulator and optimizer using the following equations of motion for a non-rotating frame of reference $$\dot{v} = \frac{T \cos \varepsilon - D}{m} - g \sin \gamma$$ $$v \...
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1answer
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What is the purpose of eccentric, parabolic and hyperbolic anomaly?

I am currently reading David Vallado's 'Fundamental of Astrodynamics and Applications' and I have this doubt on the 2nd chapter named 'Kepler's Equation and Kepler's Problems'. Although I understand ...
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Are Jool's moons' orbits stable?

The fictitious Kerbol system includes ...five planets: Moho, Eve, Kerbin, Duna and Jool; and two dwarf planets: Dres and Eeloo; orbit around it. Kerbol contains 99.97 % of the mass in the Kerbol ...
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Why does it cost more to get to L4/5 than C3=0?

I was looking at Delta-V budgets and noticed that it costs 4.1 km/s to get from LEO to L4/5, but just 3.2 km/s for LEO to geocentric C3 = 0 (escape velocity). I find that counter-intuitive. Why does ...
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Does apsidal precession rate have any dependence on the argument of periapsis? Perhaps higher order?

Writing this comment got me thinking, which invariably leads to confusion in my case. @DavidHammen's answer to show that for Juno's near 90° polar orbit the major precession is apsidal; periapsis is ...
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How big is an orbit of "X by Y miles"?

While reading the NASA overview of Apollo 11, says: Apollo 11 launched from Cape Kennedy on July 16, 1969, carrying Commander Neil Armstrong, Command Module Pilot Michael Collins and Lunar Module ...
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"NASA's Europa Clipper has been liberated from the Space Launch System" How would the "physics" of a Starship-based mission differ from SLS?

The Hill's NASA's Europa Clipper has been liberated from the Space Launch System is quite an illuminating read about the politics of space launch. However, I noticed that it also says: Both the ...
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Can a satellite orbit the ISS?

Is stable orbit of a small satellite around the ISS theoretically possible with minimal station keeping?
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1answer
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How can you calculate a course based on constant acceleration burn and deceleration burn?

In the TV series The Expanse, a sci-fi space-engine called the "Epstein Fusion Drive" is a thruster capable of performing constant acceleration (up to and beyond "20g" (about $200 ...
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Satellites Orbital Parameters

I want to access satellites' orbital parameters like inclination, right ascension of ascending node and argument of perigee. Unfortunately, I haven't been able to find this information. Is there a ...
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3answers
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Bucket loop between Earth and Moon?

Please don't bite my head off. If this is so stupid that it deserves to be squashed, I'm quite happy to delete the question. I mainly would like to know whether anyone's ever suggested this (I ...
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Why is the Orbital Velocity after SECO of Crew Dragon with 27K km/h lower than of ISS?

Crew Dragon after SECO: Orbital Vfelocity at 27,000km/h at 200km altitude (roughly 9-10min after liftoff). ISS Orbital Velocity at ca. 28,000 km/h at 400km altitude.iss_altitude,iss speed However from ...
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I want to simulate the antenna pointing error when tracking LEO satellites

I am trying to simulate the antenna pointing error of our antenna when tracking LEO satellites using TLE data. I am using the Skyfield library in python. First I loaded the TLE data from the Celestrak ...
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1answer
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Are solar sail spirals logarithmic? Can this be shown analytically or by dimensional analysis alone?

There are several questions and answers here about spiraling towards or away from the Sun using solar sails tilted by roughly 45 degrees to convert the sunlight's incoming radial momentum into ...
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Why did my vis-viva math solution get so close despite being wrong? Under what conditions would it have been a good approximation?

I tried to answer Equation for Velocity and distance from Sun of a solar sail powered spacecraft but I'm missing something. I set up a math solution and got about 0.4 year to reach zero velocity based ...
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1answer
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How did the Kepler Telescope establish its orbit after third stage burn? (Follow Up)

note: This is a follow-up question based on a discussion under this answer. The Kepler Telescope was (is) in a heliocentric Earth trailing orbit, but I want to figure out how it was able to reach this ...
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Nickname and citation for famous, historic three-body spacecraft trajectory design "manual"; something like "DoKaRoMo"?

There is a heavily-cited work about the use of three-body orbits with four authors, I think some at NASA at the time. I know that I've cited this abbreviation in my own posts a few times, but I can't ...
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Station-keeping delta-v per year for an Earth-Moon vanilla halo orbit?

This answer reminds us that an Earth-Moon L1 or L2 vanilla1 halo orbit remaining always visible to some patch on the Moon's surface requires station-keeping. Queqiao uses such an orbit having ...
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Why shouldn't we illustrate spacecraft trajectories on top of static pseudo-potential surfaces?

Three-body spacecraft orbits1 are regularly discussed here and from time to time someone will include a pseudo-potential plot from Wikipedia in their explanation. The discussion often goes south when ...
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2answers
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Patched conics Earth to Mars transfer, find Vinf at arrival at Mars

I've tried to solve a patched conic problem found on the 8th chapter of Fundamentals of Astrodynamics, Bate, Mueller and White, Dover 1971. Attached is the problem, which concerns the sub part (e), ...
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How did the Kepler Telescope reach its orbit?

The Kepler Telescope was (is) in a heliocentric Earth trailing orbit, but I want to figure out how it was able to reach this orbit exactly. It was launched on a Delta II with 3 stages and I studied ...
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1answer
195 views

Calculated Classical Orbital Elements of the ISS seem to differ from the actual ones

I am trying to calculate the Classical Orbital Elements of the ISS using Python, and then compare them with the "actual" ones provided on the Internet. However, my obtained data differs by a ...
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GMAT - Locating inter-spacecraft contact instead of spacecraft to ground station

GMAT implements two "event locators" that find eclipse times and line of sight intervals. However, this only lets you analyse data between a ground station and a spacecraft. Is there a way ...
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Orbital mechanics from Daniel Suarez's book "Delta-V"

In the book Delta-V, a climactic scene involves a high-acceleration return from the orbit of Ryugu to Earth. The book makes a big deal about the delta-v needed for the trajectory (hence the name) so I ...
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How to calculate the very special orbit of 2020 SO

From a NASA JPL page: Earth May Have Captured a 1960s-Era Rocket Booster Source (Sorry, I got an error when I tried to include an animated gif.) 2020 SO was captured by Earth's gravity on Nov. 8, ...
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Modelling a circularizing burn at Apogee

I am relatively new to rocket physics and am looking into modelling burns. Is there a good place to start modelling an orbital burn? I know about the rocket equation but perhaps that is not what is ...
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1answer
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How do I obtain geocentric position vectors at three successive times before I use Gibbs' method?

I would like to try out Gibbs' method of preliminary orbit determination, which requires that from observations of a space object at the three successive times $t_1$, $t_2$ and $t_3$ ($t_1 < t_2 &...
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1answer
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My vector math seems to be off in this 2D simulation of a solar system

I intend to simulate gravitational acceleration on a 2D plane (simplified, no gravitational constant). My code is interpreted without any error in the console, but instead of having the two circles ...
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1answer
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Tutorial for orbits from TLE data

I've been looking for a new hobby, and have been reading some about satellite tracking. I was wondering if there was a good tutorial that walks through how to use TLE data. So far I have found ...
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1answer
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GMAT targeting - why targeting RMAG and DEC works while RadApo and INC doesn't?

The GMAT examples demonstrate targeting using this method for targeting a specific Apoapsis increase maneuver: Vary the prograde speed Apply Maneuver Propagate to the Apoapsis Achieve "the ...
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What is/was legacy TLE ephemeris type 2? (TLE, line 1, column 63)

Wikipedia's Two-Line Element Set entry for line 1, column 63 (1.12) says: Ephemeris type (internal use only - always zero in distributed TLE data)13 13Celestrak Frequently Asked Questions: Two-Line ...
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Using the Clohessy-Wiltshire equation, what would be the expression for ' r '?

I'm looking for an expression for r. The difficulty I'm facing is simplifying the C-W equation
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How do space agencies choose arrival dates to planets (i.e. Mercury) from a gravity assist (i.e. Venus)?

Assuming I was looking for arrival opportunities from 2020 to 2030, how can I calculate the possible arrival dates to Mercury given a departure date from a gravity assist from Venus?
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When B is directly below A, as shown, what's B’s velocity (in vector notation) relative to A?

Spacecraft A and B are in coplanar circular orbits around the Earth. The orbital radii are as shown in the figure. (Not looking to use C-W equation. Just the equation describing relative velocity ...
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Can we just throw a satellite in to mars orbit with a very high spin?

I am thinking about this scenario of throwing a satellite to Mars orbit with a high spin, Can we just throw that? one hypothesis can be that high-frequency spinning generates apparent gravity so it ...
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When sending astronauts to the ISS, how does each spacecraft sense the other? [duplicate]

When spacecraft with astronauts tries to dock with the ISS, are there special sensors in each used to track the other? Does one usually do the detection, tracking and orientation in order to "...
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Can a moon orbit its planet faster than its planet rotates?

Can a moon orbit its planet faster than its planet rotates? Can a moon orbit its planet more than once per the planet's day? It seems possible but I'm not sure. Are there any known examples of this ...
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What are the shortest orbital periods used for their repeat ground track properties?

The most well-known repeat ground track orbits are geostationary and geosynchronous orbits, having orbital periods in a 1:1 ratio with the revolution of the Earth. Faster repeat ground track orbits ...
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1answer
277 views

Under what conditions can a non-resonant satellite stay hidden from an observer on the ground?

From the perspective of someone on the ground, a satellite is usually not above the horizon all the time. But can a satellite have such an orbit that it is never above the horizon? Such orbits clearly ...
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Are LVLH and RSW coordinate systems the same thing?

I've been reading into satellite relative motion, and I noticed that the literature split on using LVLH (local vertical local horizontal) and RIC/RSW (radial intrack crosstrack) coordinate frames. ...
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2answers
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Is it possible to predict if an orbiting satellite will pass over a given point on Earth after n periods?

I'm learning basic astrodynamics, and I have a question that I cannot find on the Internet (maybe I'm not looking hard enough). My question is, is there a way to predict how many periods would a ...
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Changes in Orbital Parameters Due to Drag

Other than STK, are there any commercially software packages available to model changes in orbital parameters due to increases/decreases in satellite drag. I am trying to figure out if aerodynamic ...

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