# 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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### 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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### 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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### 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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### 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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### 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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### 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. ...