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 might one approach using AI (convolutional neural network) to predict collisions in orbit?

CNN's Tomorrow's Hero profile Meet Amber Yang. She's trying to prevent a space debris catastrophe describes an investigation into the use of a convolutional neural network (CNN) to predict possible ...
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Navigating in space with only cameras

I'd like to figure out how to determine where something is in space (solar system) based only solely on measurements that can be preformed on location visually/with a camera. Let's say I'm floating in ...
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Does the “17” really mean anything with respect to GNSS orbits being rational factions of a sidereal day?

This answer suggests that the orbital periods of the four large GNSSS contstellations are linked to the sidereal rotation period of the earth by rational numbers with 17 or 34 as the denominator in ...
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What altitude would an aphrodiosynchronous satellite need?

A geosynchronous orbit has a period of 24 hours, and mostly stays over the same location on the surface of the Earth. According to this blogger, the equivalent term for Venus should be "...
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Does trajectory of an object orbiting a planet depend on the object's mass? (With hypothetical Apollo example)

For example (hypothetically), if an Apollo crew of one of the lunar missions went on EVA just after Trans Earth Injection burn and carefully released a small bolt, or a plastic package from their food,...
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What is the smallest body in which a sling shot maneuver can be performed?

This question asks about the smallest sling shot maneuver performed. What was the smallest intentional, acknowledged slingshot maneuver? I'm asking how small of an object be to perform a sling shot ...
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What's the eccentricity of an orbit (trajectory) falling straight down towards the center?

Discussion below this answer has got me thinking. A circular orbit has eccentricity of $\epsilon = 0$, ellipses $ 0 < \epsilon < 1$ (between but not including 0 and 1), and parabolic and ...
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Can one put a large nickel-iron asteroid into an elliptical solar orbit that results in a soft(ish) earth landing?

My daughter and I are debating whether it is technically feasible to bring a nickel iron asteroid to the surface or the earth non-destructively. I felt it was impossible. Her thought was that with a ...
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What is “propulsive passivation” and why will the SpaceX STP-2 mission do it?

The Teslarati article SpaceX’s Falcon Heavy flies a complex mission for the Air Force in launch video discusses the upcoming third Falcon Heavy mission STP-2 and quotes the caption on the linked ...
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How would a laser “shoot down” space junk?

This question links to an article describing a ground-based laser designed for shooting down orbiting space debris: "The scientists intend to use the massive soon-to-be-built telescope at the Altay ...
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How long would a Falcon Heavy last in orbit around Mars before degrading?

Elon Musk made another characteristic splash recently with his plan to launch a Falcon Heavy into orbit around Mars, with the bonus payload of his personal Tesla Roadster inside. Of course, it's an ...
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Is there a simple relation between delta-v and travel time?

For example, if it takes a delta-v of 4 km/s to fly from LEO to Mars in 8 months, according to one mission plan, would it take half the time, 4 months, if the delta-v was doubled to 8 km/s? Is there ...
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Could Starman get ejected from the Solar System?

This is not about a prediction of Starman's fate, although it might be interesting to find it so. This is about any object having similar aphelion and perihelion values to Starman (Elon Musk's Tesla ...
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Is space mining and development as shown in the television show “The Expanse” realistic?

In the television show "The Expanse", we see the Solar System having been partially colonized and developed during the 23rd century. The spacecraft in the show appear to depend on conventional ...
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Propagation of pressure waves in Low Earth orbit

So in a Wikipedia article about space debris i read that---- At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight atmospheric drag, lunar perturbations, ...
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Why doesn't the ISS use ion engines to maintain altitude?

So the ISS uses small thrusters on the Soyuz (usually) to perform occasional reboost burns to raise its orbit. This goes through, from what I can tell, around 3,500 kilos of fuel per year. Would it ...
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Lunar Free Return Trajectory Simulation

I have been trying to simulate a lunar free return trajectory using the state vectors for the Apollo spacecraft provided by JPL after they had performed their trans-lunar injection burn. My ...
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How did Voyager 1 avoid crashing into Jupiter?

Consider the following video (taken from here): To me it looks like Voyager 1 will crash into Jupiter. Obviously Voyager 1 didn't crash into Jupiter, but at a glance it looks like it will. What ...
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Differences between launch injection and transfer orbits for geostationary satellites

I am familiar with all different orbits but I struggle with the new launch injection method in GTO. What are the differences between sub-synchronous and super-synchronous transfer orbits compared to ...
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Can a projectile fall into a low Earth orbit?

One of the problems with space flight is the speed required to achieve orbit; 17,500 mph. One of the ways I've always thought to achieve this was to launch at a low speed to a very high altitude then ...
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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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How did the Apollo guidance computer handle the Earth-Moon system's rotation around the Sun?

In this comment I just wrote: "...but at all other times it is just doing math to calculate its trajectory." The math needed a stable clock Timing accuracy of the Apollo Guidance Computer? (also 2, ...
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How can a planet “catch” an asteroid?

When an asteroid enters the sphere of influence of a planet and the periapsis is above the atmosphere (if it wasn't and the object doesn't leave the atmosphere at escape velocity, the object would ...
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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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Did the “Zvezda” module really dock to the ISS 2 weeks after launch?

Today I've read in the Facebook group of Roscosmos (original text in Russian) that 16 years ago on this day the Zvezda module was launched into space. According to the article 2 weeks later it docked ...
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How can I predict what an object's orbital state vectors will be in the future?

I have a position and velocity vector for an orbiting object and can calculate the orbital elements. From a simple two-body situation, how can I predict where in the orbit the object will be at some ...
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Why is it best to perform an orbital inclination change at apoapsis?

Wikipedia on its page on efficiency of orbital inclination change writes: However, maximum efficiency of inclination changes are achieved at apoapsis, (or apogee), where orbital velocity V, is ...
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Deviation of semi-major axis

If I calculate the semi-major axis of Molniya-1T with $a = \sqrt[3]{\dfrac{GM}{n^2}}$ with $n=3.18683728\text{ }d^{-1}$, I get another apoapsis ($a=19505.7$ km) as noted at Heavens Above: apogee ...
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What shape was Apollo 13's orbit in a non-rotating reference frame?

The classic diagram of Apollo 13's trajectory is a figure-8 (eg. Wikipedia's illustration). This is clearly drawn in a reference frame that's rotated to align with the Earth-Moon axis. What shape ...
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Change of inclination using low thrust

I am studying low-thrust maneuvers, in particular a change of inclination only. According to (Ruggiero et al., 2011)[1], if one writes the perturbation force in the Gauss planetary equations in terms ...
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How do stable equilibrium points work in GEO? If all geosynchronous spacecraft suddenly lost stationkeeping, would most “fall into” one or the other?

The (currently unanswered) question Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v to move from one to the other? (also see comments at Delta-v to move from GEO to ...
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How long can a moon orbit a planet?

Today it was announced that Phobos was formed in a giant explosion, similar to how the Moon was formed. Phobos is actually coming closer to Mars every year, and has an expected 10 million year ...
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How to get earth-centered, earth-fixed coordinates from Skyfield?

I recently started using Skyfield (python) to find (x, y, z) coordinates of things in space. Now I'd like to transform between Earth-Centered, Earth-Fixed (rotating) and Earth-Centered Inertial (non-...
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How will Akatsuki get into orbit around Venus?

JAXA's Akatsuki was supposed to enter orbit around Venus in 2010, but the insertion failed. Its orbital maneuvering engine was supposed to burn for 12 minutes to get it into position, but it stopped ...
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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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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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How can I figure out the distance to Juno at any point in time?

Juno will fly by Earth on October 9, 2013. There is an event to encourage Amateur Radio Operators to say high to the satellite. What I'm trying to do is figure out if I have any chance of pulling it ...
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Is an orbital epoch merely a timestamp?

Just what the title states please. This site writes to say Orbit epoch is the time at which the established orbital elements are true The site goes on to mention sub-elements - Start Day The ...
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Phasing maneuvers; methods to travel between satellites with very similar circular orbits

If you imagine two satellites orbiting earth, each in a circular orbit in the same plane and at the same altitude, but varying in their angular position, the simplest way in my mind to travel from a ...
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How can I calculate the orbital elements from two position vectors and a time difference?

I have two position vectors for my satellite, and I know that the satellite reaches these two positions 15 minutes apart. I know I can find the inclination using linear algebra and my position ...
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How can debris from an impact escape to a stable orbit?

Please help me understand: As far as I understand it, when an object gets thrown off the surface of a planet by an impact and doesn't reach escape velocity it is on a suborbital trajectory and ...
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How to calculate the time to apoapsis & periapsis, given the orbital elements?

I have the 6 orbital elements (excluding Time of Periapsis Passage, obviously), 2 state vectors, and a lot of other parameters like orbital period. I am looking to use them to calculate the time to ...
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Is a manned craft powered by Solar Sail feasible from Earth Orbit to Lunar Orbit

Trying to ask a series of questions but I'm breaking up the overall point into easier "chunks" to not make the overall question too broad. Question 1: Designing a craft for transfer from Earth to ...
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What was the first practical use of a satellite constellation?

If I loosely define "constellation" here as a group of earth satellites where different ones are visible at different times, and you need all or most of them to get round-the-clock coverage, some ...
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How does one spacecraft best visit multiple asteroids?

Dawn visits both Vesta and Ceres, thanks to its patient solar electric ion propulsion. AFAIK more xenon and perhaps a little more hydrazine for the attitude thrusters, would've sufficed to give it ...
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Can spacecraft rendezvous in orbit on planetary missions

Since we have yet to lose personnel onboard the ISS due to starvation, I assume that space agencies have got a good handle on the mechanics for a rendezvous in low earth orbit. What would be the (...
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What precision is needed for aerocapture?

In his excellent answer to the question of how we make a round trip journey to Mars, @MarkAdler mentions that aerocapture would be used to get into orbit around Mars, saving fuel and therefore weight. ...
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When could MAVEN launch to get to Mars, if it misses its launch date?

What kind of transfer orbit will MAVEN follow? If it is a Hohmann Transfer Orbit which will be effective only when the launch point and destination of spacecraft are in straight line. Earth is its ...
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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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Besides hyperbolic flybys, what are all the other cases where the Oberth effect can be used?

For hyperbolic and parabolic flybys it's common to take advantage of the Oberth effect and get the most delta-v from a propulsive impulse by doing it at the point of maximum velocity. Question: But ...

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