# 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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### Question about the Hohmann Transfer: why does delta-v go down when transferring to a higher orbit?

I'm trying to estimate the delta-v (and, by applying the Rocket Equation, the propellant) required to lift a payload from LEO to a higher orbit. As I understand it, the standard way to do this is with ...
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### C3 calculation in interplanetary missions

I'm starting to study Astrodynamics and I'm trying to make a Porkchop plot for a Mars mission to compare the results with actual porkchop plots which I found on the internet, so I know if my ...
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### Launch windows for on-orbit rendezvous

Suppose you've got a spacecraft in an orbit similar to that of ISS (let's say 51.6 degrees, but about 19 km lower). Suppose also you want to launch a second spacecraft to rendezvous with the first, ...
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### Finding Delta V to circularize orbit after a transfer orbit.

I have been working on calculating all the the delta V needed to fly a rocket from one planet to another. I have worked out the delta V needed to raise the orbit to intercept the second planet, but ...
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### While descending from orbit, can a blimp glider skip an atmosphere to shed speed?

While descending from orbit can the air be thin enough for a glider type blimp to slowly shed speed? Could a blimp skim the atmosphere around a planet, slowly decreasing air speed, without the need ...
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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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### How do spacecraft rendezvous in orbit?

Given two spacecraft (let's say, the ISS and an unmanned resupply capsule), how do the two spacecraft rendezvous with each other in space? If they're moving at the same speed in space, they'll never ...
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### Earth Moon Pork chop plot

Does pork-chop plots exist for Earth-Moon System? I could only find pork-chop plots for Earth-planet systems.Could someone please shed some light on this topic?
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### What is the frame of reference for orbital speed?

Don't treat this question lightly. It's a thing that's been biting me for a pretty long time, and while it's "intuitively obvious", if you get into finer details, it gets quite convoluted. So, a ...
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### If we could send an orbiter to the Pluto-Charon system, could we put it in a stable orbit?

The barycenter of Pluto and Charon is in space between the two bodies, close to Pluto. It is the center point of the animation below. The image is roughly to scale. Note that the two bodies are ...
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### Gravity assist for manned travel

Since we already use gravity assist to launch satellites through the solar system, is there any way we can use gravity assist to speed up a manned trip to a planet such as Titan or Europa, while also ...
411 views

### Do all dangerous asteroids first pass through keyholes?

Scitech Daily's MIT Engineers Devise the Best Way to Deflect an Incoming Planet-Killer Asteroid Now MIT researchers have devised a framework for deciding which type of mission would be most ...
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### Was the lunar landing site always in the same plane as the CM's orbit?

Did the Apollo command module always pass directly over the lunar landing site? Or were they sometimes in different planes? My inclination (pun intended) is that staying in the same plane would ...
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### How does SGP4 work?

For calculating orbital state vectors of satellites, SGP4 (simplified perturbations model) is often used in conjunction with two-line element sets to calculate future positions of orbiting objects. ...
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### Why does in-flight mission abort often ends in ballistic high-g reentry?

I am seeing a lot of references to the “ballistic reentry” mode of the crew return vehicle in relation to the abort during the powered ascent stage. In partiulat, the recent crewed Soyuz MS-10 abort ...
560 views

### 3-Body Simulation and Accuracy of Lambert Interplanetary Solver

I've found that using a Lambert solver together with the equations of the patched conic approximation for an interplanetary flight from Earth to Mars is quite inaccurate, when taking Earth's ...
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### How much variation in orbit altitude is caused by gravitational variation, in LEO?

Imagine a hypothetical spacecraft in LEO, at 200km. Ignore air resistance for a moment. It's actual height will vary, due to both gravitational anomalies and the shape of the Earth. Do we know ...
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### Which orbital maneuver is currently regarded as the most viable for a human mission to mars?

I realize that there are different orbital maneuvers for different goals (e.g. optimizing time, efficiency, cost, etc.). However, which variables are currently considered as the most important to be ...
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### Number of burns for optimal launch ascent

If we consider Mars, with its relatively low gravitational acceleration and low density atmosphere, I had always assumed that if we have a single-stage-to-orbit launch vehicle on the surface of Mars ...
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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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### 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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### Why is it so difficult to predict the exact reentry location and time of a very low earth orbit object?

Many artificial satellites are going to do a destructive reentry in the atmosphere and some will reach the ground, constituting a significant threat (e.g. GOCE, UARS). Often I heard that for those ...
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### What do the shaded vertical lines in the animation of Gravity assists of space probes, mean?

Example Animations from Wikipedia — https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Animation_of_Voyager_1_trajectory.gif https://en.wikipedia.org/wiki/File:...
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### Earth polar orbit to Lunar polar orbit

Suppose you wanted to achieve a polar orbit around the Moon, starting from LEO. Would it be better to start from a polar orbit around the Earth? "Better" meaning using less fuel, having more frequent ...
344 views

### How much accuracy is required to achieve interplanetary orbit without adjustment or deceleration?

It seem that "Around 15,000 tonnes of meteoroids, micrometeoroids and different forms of space dust enter Earth's atmosphere each year" some references say "Millions of meteors occur in the Earth's ...
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### Calculation of V1 (orbital speed) during ascent

I am studying instrumentation of NASA's Orion spacecraft, and there is a readout for V1 (I am assuming this is the "first orbital velocity", for circular orbit), and it seems to be in small decimals. ...
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### What is the largest body in the solar system we could meaningfully and accurately adjust the orbit of?

There is a lot of science fiction and emerging science that move comet and asteroids as part of the main plot. Pretty much everything in our solar system, is in orbit around the Sun, or in orbit ...
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### Earth departure flight path angle for fast Earth-Mars transfers

I'm interested in Earth-Mars transfers that are optimized for speed rather than fuel savings. For standard elliptical, parabolic, and hyperbolic transfers, it appears that the Earth departure flight ...
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### 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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### How are Two Line Elements (TLEs) obtained?

This question is a follow up of another question I have asked recently. For the sake of experiment I propagated the ISS's position (using SGP4) from epoch of first TLE to the epoch of next released ...
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### RIP Kepler, how shall we call your orbit? Does this cyclic flip-flop process have a name?

So long, and thanks for all the Fish Planets The captions in the NASA Ames Research Center video What Will Happen to NASA’s Kepler Spacecraft? read as follows: NASA’s Kepler space telescope found ...
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### What could a High Earth Orbit be used for in practice?

I was perusing wikipedia and saw this awesome infographic: Original location of infograhpic: Wikipedia Then it hit me, in all the time I've been browsing space articles and such... I've never ...
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### Trouble deriving rectangular components of acceleration of satellite in orbit around Earth with J2 consideration

I am trying to derive the rectangular components of acceleration for a satellite in orbit, with Earth oblateness in consideration, in order to use the RK4 method to find the updated position and ...
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### How much harder is it to land on the Moon away from the equator and the poles?

If a ship enters orbit around the Moon's equator, any place on the equator is equally accessible and doesn't take long to get to. The ship passes over the same strip of land with each orbit. Equally, ...
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### Are Lagrangian points associated only with the smaller body?

Diagrams of Lagrangian points I've seen always show the points near the smaller object, following its orbit about the larger one. For instance: from Wikipedia. But in fact the smaller object ...
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### Position of shuttle viz iss

Is the shuttle ahead of the ISS in the orbit before docking. Does the international space station catchup with the shuttle in the same orbit?
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### Python Libraries: Numerical Propagators and Access Calculations

I have written some of my own code in Matlab that performs two body unperturbed as well as J2 perturbed orbit propagation. I am shifting to a new environment that requires the use of Python, and can't ...
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### What are the orbital-mechanical advantages of a long (100+ second) sub-orbital coast phase?

This answer to Trajectory to get into orbit says: In most real launches to low Earth orbit, the burn continues from liftoff until orbital insertion, without a coasting phase. Some (like Antares) do ...
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### Specific kind of orbital transfer?

What do you call the kind of transfer that takes an orbiting body from orbiting the planet of the system to orbiting a moon of the system. I am merely looking for the name of this kind of transfer ...
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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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### 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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### Calculating the time since periapse of an orbital position

Given ... A known position along a planets orbit The semi major axis The eccentricity of the orbit The period of orbit is it possible to calculate the time since periapse of this orbital position?...
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### How to calculate the kilowatt hours (kW-h) needed for a solar-electric engine to produce a given delta-v?

A spacecraft is in LEO and I would like to reach a certain point in space; let's say Mars. If I look at the diagram in this answer I see that the delta-v from low Earth orbit to low Mars orbit is ...
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### Are there some three-body orbits that can't be escaped? Can we know without propagating forever?

update: Searching for "choreographies" I found this Physics SE question which is related but different because it asks only if periodic solutions can be proven to be periodic numerically and my ...
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### A constant parameter in a three body system?

In a two body system, there are a lot of orbital parameters not changing over time, like eccentricity or the orbital plane. A constant parameter can be a combination of two or more, like even though ...
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### Space rocket payload by inclination

I know that near the equator where the inclination is 0° it is easier to put payloads to low earth orbit because of the advantage of rotation speed of earth which saves more fuel. Saving more fuel ...
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### Equation of motion for Geocentric orbit

I'm simulating the motion of a body in a Geocentric orbit by integrating the equation of motion. I'm using the following equations for the acceleration of an object in a gravitational field defined ...
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### Trajectory Optimization To The Moon (Case Study: Chandrayaan-2)

People always ask this million dollar question of " What is the best path/trajectory to take to reach a certain orbit or point in space". Chandrayaan-2 had a pretty neat transfer to the moon, it took ...