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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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Computing the local orbital frame vector directions and angles of gyroscope direction in the satellite

In the context of the study of a cubesat (little satellite), I am asked to define the local orbital frame and compute the local orbital frame vector directions as a function of time and get the ...
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482 views

Would any manned orbital launches to date have been possible (but lower) if they were launched retrograde instead of prograde?

Manned launches have always been launched prograde to take advantage of the Earth's rotation velocity boost, and often in order to match the prograde orbit of another spacecraft for rendez-vous. I ...
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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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1answer
145 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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367 views

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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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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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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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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1answer
127 views

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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1answer
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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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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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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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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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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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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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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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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
132 views

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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1answer
445 views

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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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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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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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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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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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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1answer
135 views

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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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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0answers
86 views

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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103 views

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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1answer
159 views

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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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
141 views

How much does the tidal effect affect satellites in a retrograde orbit?

How much more unstable are satellites in retrograde then a pro-grade orbit? Does the stability of a retrograde orbit increase with altitude? This answer said this orbit is unstable and made me think,...
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How would propagation differ between a GEO and a Retrograde GEO?

A Binary Equatorial Synchronous Retrograde Orbit is an orbit that would travel in the opposite direction of GEO and would pass over the same point on Earth twice per day at the same altitude of GEO. ...
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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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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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1answer
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How well the orbits of Jupiter Trojans to be visited by Lucy may be predicted?

The orbits of the large planets are very well known and their position may be precisely predicted for the planning of complex swing by maneuvers of interplanetary space probes. There are exact ...
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2answers
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How to correctly make a fake, counter-propagating TLE?

In this answer I have said: Do not make FAKE TLEs! I would now like to make a fake TLE. Specifically I'd like to generate a counter-propagating "twin" of an orbit by flipping inclination by 180° ...
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How presise could 2 satellites “thread the needle” in orbit?

I have a question about using a magnetic field to propel 2 satellites off each other while traveling in opposite directions on the same orbital plain to intersect either 2:1 or 1:1 on each orbit ...
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1answer
121 views

How fast are trips to the Moon for unmanned spacecraft typically?

The period of an orbit around the Earth is given by: $$T = 2 \pi \sqrt{a^3/GM}$$ For Earth GM is about 3.986E+14 m^3/s^2. Put in $a$ = ((6378+400)*1000) for the ISS in LEO (as a test) and you get ...
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Launch Vehicle LM2D

As it is well known, the circularization of orbits needs at least 3 stages. How could the Chinese launch vehicle LM2D circularizes its orbit with only 2 stages?
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Could Galileo GNSS satellites 5 and 6 join the constellation if their orbit was raised, or is even more delta-v needed?

The Gallileo GNSS satellites numbers 5 and 6 have been used to make a record-breaking precision measurement of gravitational time dilation as a bi-product of them being in the wrong orbit. See (just ...
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1answer
56 views

Would the orbits intersect during 7 days?

I'm calculating the probability of collision of the satellites. I'm trying to filter the set of orbits to minimize the calculations. Which conditions may definitely say that the given 2 orbits ...
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4answers
353 views

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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1answer
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Calculating the radial, in-track and cross-track distances

I'm computing the relative distances between satellites. The following picture shows the distances, which are considered as risky. What do Radial, In-track and Cross-track mean and why are they ...
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5answers
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The dreaded apocalyptic asteroid approaches Earth but lands safely on the Moon at zero relative velocity

An asteroid approaches and the Moon 'catches' it in the same way that a sports player catches a ball - that is to say by matching the velocity of the hand to that of the ball. Could a lucky slingshot ...
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1answer
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How do you find lunar flyby using Apollo 13 mission report data?

Link to mission report: https://www.hq.nasa.gov/alsj/a13/A13_MissionReport.pdf So Im trying to do analysis on the mission phases of Apollo 13 but my part is to only focus on the flyby part. My ...
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Proper handling of terminal guidance of finite burn closed-loop execution for rendezvous conditions?

I'm writing some software which uses Optimal Control Theory / Calculus of Variations / Pontrayagin's Minimum Principle / Primer Vector Theory to do closed-loop execution of finite burns (in KSP). ...
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2answers
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How does a Mars lander reach a chosen landing site?

I see lots of questions how landing sites are chosen, but none so far how these landing sites are reached. It already looks like magic how the target planet can be reached at all, but when are ...