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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.

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Timetravel missunderstanding(s)?… versus time dilatation during acceleration process [on hold]

Words are not the best way to communicate. To correctly describe my question I need to explain the context. If I say "timetravel" most people I have met will think about some sci-fi movie where bunch ...
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Rotating in orbit?

Reading this question (Is the cupola, on the inside of the ISS, cold or warm to the touch?) prompted me to wonder about an object in orbit's orientation as it orbits its host object. For example, ...
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1answer
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NAIF and SpiceyPy returning seemingly inaccurate results

I am yet another amateur astrophysics enthusiast creating a solar system simulator. I began by hard-coding planetary bodies and their satellite orbiting characteristics via JPL data tables such as ...
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1answer
137 views

Time dilation between Mars and Earth due to different mass

I am not sure I understand the Time dilation correctly but if mass has dirrect impact on time...than lets consider cosmological event - one orbit of planet Earth around Sun. This event will person on ...
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Why does the Juno spacecraft flyby Earth on the way to Jupiter?

Hohmann transfer to Jupiter is about 2 years 8 months. Juno spends 5 years getting there, almost twice as long. I note that it takes Juno 2 years 8 months to get to Jupiter after the Earth flyby, does ...
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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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Can the question below ignore the acceleration downwards to the centre of the Earth? [on hold]

The question "What would a "Kármán plane" look like, a bird, or a plane ?" clearly ignores the acceleration downwards to the centre of the Earth. The lift force for an airplane is: $$ F_L = 0.5 \rho ...
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Can the centrifugal force still be ignored as the lift force is a small fraction of the gravitational force at the Kármán line altitude? [duplicate]

The lift force for an airplane is: $$ F_L = 0.5 \rho v^2 S C_L $$ According to this talk page the lift coefficient for a supersonic airplane is: $$ C_L = \frac{4\alpha}{\sqrt{M^2-1}} $$ where $\...
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3answers
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Is the equation showed below the right one for an airplane flying at the Kármán line altitude?

$$\frac{GM_Em}{(R + h)^2} - \frac{ \rho v^2 S C_L}{2} = \frac{mv^2}{R + h}$$ $GM_E$ is Earth's standard gravitational parameter , $R$ is Earth's radius and $h$ the altitude of the airplane above the ...
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1answer
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How will JWST maintain its elliptical orbit around L2?

I understand that JWST will have a vertical elliptical orbit around L2, but what I don't understand is how the telescope will actually maintain an orbit if there is no body in L2 to actually orbit ...
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Which point in an orbiting body most closely follows its Keplerian trajectory?

Keplerian orbits can describe the motion of a negligible mass around a massive fixed central body, but they also describe the motion of two bodies around their center of motion. But which point ...
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1answer
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Why would the orbit of a satellite in GEO climb by 21 km in altitude over six months by itself?

This answer mentions several effects that tend to move geostationary satellites out of their "box" over time, but one really surprised me. According to the plot below (from there, but uncredited) the ...
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0answers
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Understanding shape of DSN's 'kinky uplink protocol' keeping frequency in coherent transponder's optimum bandpass?

This tweet by deep space SDR entheusiat Edgar Kaiser @df2mz shows a squiggly tone from MRO. Mars Reconnaiscance Orbiter (MRO) X-band downlink. The signal shows this kinky behavior due to a ...
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1answer
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How stationary is geostationary?

When a satellite is in geostationary orbit, it is supposed to stay above one spot of the earth and rotate around the earth at the same rate the earth spins. But how exact does that equality need to be?...
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How many kinds of closed or periodic orbits are there in the circular restricted three-body problem?

Question: How many kinds of closed or periodic orbits are there in the circular restricted three-body problem? Has anyone made an attempt to enumerate and classify/categorize them? Notes: If there is ...
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Determining the spacecraft position vector with respect to ICRF frame for Venus flyby

For an interplanetary mission design to Saturn, I have considered doing multiple gravity assists starting with Venus. I am using the JPL Horizons ephemeris and ESA Lambert Solver. I have the ...
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2answers
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How to calculate the planets and moons beyond Newtons's gravitational force?

The question Calculating the planets and moons based on Newtons's gravitational force was pretty much answered with two items: Use a reasonable ODE solver; at least RK4 (the classic Runge-Kutta ...
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Could the $C_L$ of the X-15 be calculated from the flight data near the Kármán line altitude?

The "lift coefficient" $C_L$ can be very different for one specific aircraft at different speeds. According to this article from NASA about the lift coefficient: So it is completely incorrect to ...
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Does an airplane in orbit near the Kármán line altitude, with the air providing lift, ever reach orbital velocity? [duplicate]

The equation for an airplane in orbit with the air providing lift would be: $$\frac{GM_Em}{(R+h)^2} - \frac{\rho(h) v^2 S C_L}{2} = \frac{mv^2}{R+h} $$ $GM_E$ is Earth's standard gravitational ...
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1answer
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Would the barycenter in a binary star system be ideal for a space habitat?

I was reading about binary star systems and saw a bunch of diagrams, mainly the following: Would there be benefits to creating a space station in the center of two binary rotating bodies? Would it be ...
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Why did rendezvous on Gemini 4 fail so badly?

I can't for the life of me understand why commander Jim McDivitt thought he could eyeball a rendezvous - point the nose and thrust . The futility of that technique is one of the first things even ...
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1answer
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Where does the definition of the Kármán line on Wikipedia come from?

According to Wikipedia's article about the Kármán line: The Kármán line is the altitude where the speed necessary to aerodynamically support the airplane's full weight equals orbital velocity ( ...
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How do long range space probes adjust trajectory?

More specifically, after the main launch adjustments have been made using the primary boosters and temporary adjusting propellants how might even the slightest trajectory and orientation corrections ...
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6answers
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Is it theoretically possible to dispose of the larger pieces of space junk into the Sun?

Space junk is a real threat to working satellites in the Earth's orbit. Is it theoretically possible to make this space junk escape from the Earth's gravity (by giving them some kinetic energy to ...
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1answer
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Puzzler: Precisely what maximum distance from the Earth did the Apollo 13 astronauts achieve?

tl;dr: Both this answer and this answer quote Wikipedia to state that the Apollo 13 astronauts reached 404,171 km from Earth. I'm not able to reproduce that value. According to JPL's Horizons the ...
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2answers
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How (the heck) can 2014 MU69's orbit be know well enough for a close flyby by New Horizons?

The object 2014 MU69 is much smaller and dimmer than Pluto. Even as New Horizons approaches, it will be much harder for its 8.2 inch aperture, cooled CCD long range imager LORRI to get a fix on it ...
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1answer
498 views

Timing shadows from the Kuiper belt! Any news? Did it work?

update 24-Jun-2017: SOFIA Arrives in New Zealand to Observe Southern Skies There are plans to fly SOFIA through another predicted occultation path on July 17. SOFIA is a huge (2.5 meter dia.) infrared ...
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1answer
234 views

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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1answer
124 views

Where is Lucy going? (asteroid mission)

On Halloween (31-Oct-2018) NASA Goddard announced that Lucy has a green light: NASA’s Mission to Jupiter’s Trojans Given the Green Light for Development All I have are these links which are now ...
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Delta-v to move from GEO to GEO

To move a satellite in geostationary orbit, 166°55′E, to the antipode, 13° 4' 3.2" W, what delta-V would be needed for this to be accomplished? As for time constraints, I do not know what are the ...
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1answer
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Calculating a de-orbit burn, is this problem written correctly?

I'm having trouble finding the velocity and acceleration and therefore the time in seconds it takes, and I find the way the problem is written confusing, especially Determination of $\Delta V$: ...
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6answers
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Can you tack against the sun using a solar sail?

Solar sails are a great, inexpensive way to move out from the sun, if you’re not in a hurry. Ocean going ships are able to tack against the wind, and to move up wind. Could a solar sail gain inbound (...
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0answers
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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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1answer
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Algorithmic methods or techniques to find conjunctions in high N Keplerian element ensembles?

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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Algorithmic methods or techniques to find conjunctions in high N state vector ensembles?

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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1answer
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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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Is it correct to apply the vis-viva equation to an airplane that flies in a straight line at the Kármán line?

The vis-viva equation models the motion of an orbiting body and it applies when the only force acting on the body is it's own weight. So is it correct to apply this equation to an airplane that ...
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How much delta-v is expended to get <out of the atmosphere>

How much delta-v it's spent in getting up to avoid the air drag once in orbit?
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Does a credible Kármán plane reach escape velocity within 1 minute or does it follow the curvature of the Earth? [duplicate]

Edit: This question is no duplicate because here the dropping of the atmospheric density together with the horizontal line, play an important role. Furthermore none of the answers and question ...
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1answer
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Simulating a nanosatellite lunar flyby

I am trying to create a Lunar Flyby mission for small nanosatellites and I want to plot an orbit for it. The problem is that no website has proper information as to what variables, problems and ...
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1answer
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Could a ball of water stay in orbit?

Could a water bubble (spherical occlusion of water in air or vacuum) similar to the one in the picture below remain in Earth orbit without evaporating, dispersing, or disintegrating? Assume the orbit ...
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1answer
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Artificial ring around the Earth?

What pros and cons would a orbiting ring have for Earth? Is there enough satellites in orbit to form a joined ring?
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Are 2 satellites joined better than 2 apart?

Could new satellites be designed to intercept other older functioning artificial satellites or space junk already in orbit to add weight to the new satellite in order to last longer in orbit?
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2answers
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Is it correct to use the vis-viva equation when there are two forces acting on the orbiting body? [closed]

Edit: Although this question seems similar to the question "Is it correct to apply the vis-viva equation to an airplane that flies in a straight line", it is different because there the airplane flies ...
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What are the practical uses of a state transition matrix?

I am studying different dynamical models of relative motion of satellites. In my work, I've always just used a numerical integrator like RK78 to integrate the cartesian system of equations: $\dot{r}=...
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1answer
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Diagram of Hayabusa 2 in “Hill Coordinate System”; what is that exactly? How to convert it to inertial?

These JAXA's Hayabusa-2's two Tweets: 1 2 show a diagram of the spacecraft's motion relative to Ruygu in what they call a Hill Coordinate System, This is a diagram of the trajectory during solar ...
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1answer
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Spiraling out from circular orbit to escape via low thrust, what is γ (gamma)?

@MarkAdler's comment led me to ask Why would a slow spiral from a C3 of zero take about 2.4 times as much ΔV as an impulsive maneuver? which resulted in this tidy and efficient @MarkAdler answer which ...
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10answers
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Game for teaching basics of orbital mechanics

I am looking for a game that would be suitable for teaching basic orbital mechanics concepts to primary school students (grades 6-8). Contrary to most of the questions here asking about spaceflight ...
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2answers
793 views

Calculating velocity state vector with orbital elements in 2D

I'm writing a little project that simulates an orbit by converting from initial state vectors $\vec{r}$ and $\vec{v}$ to Keplerian elements, then converting back to $\vec{r}$ and $\vec{v}$ from those ...
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5answers
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Why did the rendezvous attempt fail on Gemini 4?

It is said in Wikipedia, that On the first orbit, McDivitt attempted to rendezvous with the spent Titan second stage. This was unsuccessful for a number of reasons: NASA engineers had not ...