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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Confusion regarding the series for true anomaly on Wikipedia

I hope this is the right place to ask. Please point me elsewhere if that is not it the case. I'm trying to calculate the position of Earth in its orbit given the day of the year. I found this ...
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Satellite’s Position and Path on 2D Map

When the ISS orbit the Earth, its path traced on a 2D Mercator Earth Map is similar to a sinusoidal wave. I am wondering is there any way to determine the trig function of the wave, knowing the ...
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2 votes
1 answer
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If humans lived on the moon, could they send a mission with the same goals as Apollo to the Earth?

The humans on the moon have similar technology to the humans (us) on Earth.
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Plot ellipse using elements from TLE

I am trying to draw an ellipse as satellite orbit in three.js, It has an EllipseCurve class which takes these inputs and draws an ellipse around center. EllipseCurve( aX : Float, aY : Float, xRadius : ...
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5 votes
2 answers
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Relationship between osculating eccentricity and Brouwer-Lyddane short eccentricity

I was under the impression that the mean elements are given by taking the average over an orbital period of the satellite, i.e.: $e_{mean}(t) = \int_{t}^{t+T(t)}e_{osc}(t')dt'[0.367in]$ where $T(t)$ ...
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7 votes
6 answers
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Could a spacecraft theoretically fly a smooth, curved arc of a turn in space like an aircraft?

I understand there in no air is space which is what allows an aircraft to fly a curved flight path. This is strictly a theoretical question given today's technology. Here are the conditions: There ...
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Axis of an orbiting spaceship

When a spacecraft orbits around earth (assume a "long" spacecraft, so that it can have an axis along its length), does its axis PITCH so as to maintain itself (axis) tangential to the earth'...
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Gravitational field of the Moon and Earth

Is there any method to find a point or plane in space where the gravitational field of the Moon and Earth are the same? And if so, what happens to a spacecraft if it passes through that point or ...
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1 vote
1 answer
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Satellite's EO sensor footprint on ground

I'm a student and I'm trying to compute the footprint of a generic EO sensor starting from sensor's characteristics and position and velocity vector of my satellite in ECEF coordinates. I followed ...
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Why is my C++ code for an orbit propagator wrong?

I tried making an orbit propagator C++ code. Its values seem to be propagating evenly but still I get a straight line orbit instead of an elliptical one. Why? ...
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1 vote
1 answer
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How to plot a satellite's orbit around Earth in MATLAB?

Given orbit height, mass and initial velocity how should I plot a satellite's orbit in MATLAB? I was hoping to use verlet integration (I need to implement a solver) possibly the velocity-verlet. I ...
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9 votes
6 answers
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How could 99942 Apophis, in 2029, be captured and brought into a low Earth orbit?

I'm currently attempting to plan out a mission where, in 2029, during Apophis's close approach to Earth, a rocket is sent up to intercept Apophis and decelerate it, making it orbit the Earth. At it's ...
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5 votes
1 answer
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How to find the hyperbolic angle given the mean anomaly?

I'm modelling a hyperbolic gravity assist trajectory around Jupiter and trying to calculate the coordinates for each hour interval before/after passing periapsis. I've calculated $M_h = 0.0176$ is the ...
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How far is the solar system's center of mass from the sun? [duplicate]

We often say that the planets orbit the sun. But, in reality, they orbit the solar system's collective center of mass. How far is that point from the center of the sun?
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2 votes
1 answer
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How does one calculate the look angle for non-geo satellites (i.e. LEO, HEO, etc.)

I'm trying to find a way to calculate look angles to not just GEO satellites, but LEO, MEO, and HEO sats. The only calculator I've found myself is here, which was referenced for a similar problem on ...
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Is there a python library to determine the position of a satellite at a given time from TLE data excluding the Satellite catalog number?

Or perhaps some simple code or formula that achieves this. I've used pyephem but it requires a Satellite catalog number.
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Why doesn't NASA fly its rockets on suborbital trajectories to the Moon?

After trying it out in Kerbal Space Program for a while, I was wondering why NASA doesn't fly on suborbital trajectories to the Moon. When I tested this idea in Kerbal Space Program I found out that ...
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3 votes
1 answer
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Are there any studies on Mars-Earth ballistic cyclers taking Mars-gravity assist into account?

In studies pertaining Earth-Mars cyclers, purely ballistic cyclers are usually relegated to many orbit solutions. For instance the classic Aldrin cycler, while elegant, can't achieve the desired turn-...
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How do I correctly convert State Vectors to Orbital Elements to State Vectors at t (sec since epoch) in 2D?

I am following Rene Schwarz' formulas and I've verified my calculations work using the converter by Tony Dunn. State Vectors to Orbital Elements Orbital Elements to State Vectors Convert between ...
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What is the maximum distance between two satellites orbiting at 400 km that would still allow them to communicate with each other using radio waves?

All satellites have the same inclination. At an altitude of 400 km, the circumference of their orbit is $2\pi \cdot (6371+400) = 42\ 543$ km. If, for example, you have only 2 satellites separated by ...
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2 votes
0 answers
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How does one generate a formula(s) for an artificial satellite's location at time t given a set of known locations at discrete times?

Given a set of spatio-temporal points in space {(Lat_1, Lon_1, Alt_1, Time_1), ... (Lat_n, Lon_n, Alt_n, Time_n)}, I need a function (i.e. a formula) that takes these points (or subset of points) as ...
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9 votes
5 answers
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Do two objects with intersecting orbits have to collide given enough time?

If I have two objects orbiting a central body, both in elliptical orbits, with an intersection at their shared periapsis, is it inevitable that they collide? I think the answer is no, but I'm ...
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2 votes
3 answers
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State vector conversion when changing central body

I have the following state vector of a spacecraft : [X, Y, Z, VX, VY, VZ]. The state vector is expressed in the inertial frame of the central body. I would like to convert this state vector when ...
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8 votes
3 answers
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Is escape from earth, hyperbolic in reality?

I have been reading on orbital mechanics and its strewn everywhere that beyond the escape velocity from any orbit around the earth, the trajectory is a hyperbola that approaches V_infinity and with ...
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1 answer
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Predicting Satellite Flyover Calculations by Hand

Recently I used transit-finder.com to get a really cool picture of the ISS transiting the sun. The prediction from the website was spot-on. Since then I'm absolutely fascinated by how the prediction ...
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1 answer
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How much energy would be required to launch a 10km x 10km x 10km cube into LEO?

I know this is a bit of a ridiculous scenario, I am just looking for a very conservative estimate as to how much force would be required to get something orders of magnitude bigger and more awkard ...
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1 vote
1 answer
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How to calculate time since ascending node crossing?

Basically I want to calculate the elapsed time since passing the last ascending node crossing for a satellite in Earth orbit (assuming two-body motion). If the orbit is circular, then we can simply ...
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1 vote
1 answer
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Formula for Determining Time to Perform Delta-V Burn Given Propulsion System Parameters

Question is as stated. Determining how much delta-V one needs to change orbits is pretty straight forward with the rocket equation. However, I’d like to see if there’s a way to calculate delta-V from ...
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6 votes
1 answer
299 views

How to attain an equatorial orbital inclination from a non-equatorial launch site?

The orbital inclination of a satellite is limited to inclinations roughly equal or greater than the latitude of the launch site, unless additional energy is expended for an orbital plane change. In ...
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What maneuvers could be useful to move between two sun synchronous orbits with different times?

Consider two sun-synchronous orbits with similar orbital elements, except for their times. For example 8h and 9h orbits. Their semi-major axes (a), inclinations (i), and eccentricities (e) are the ...
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3 votes
1 answer
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Targeted Sub-Orbital Optimization Problem

I was messing around with some orbital dynamics for a simulator I am working on, and I came across a snag that I have not been able to figure out. Specifically, I am trying to minimize the required ...
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Are the reaction wheels' spin rate (their angular momentum) initialized before launch?

It would seem that there should be an inertial reference frame established before launch by imparting a known spin rate to each reaction wheel while the rocket is on the launch pad.
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12 votes
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Why does a launch due south (180° azimuth) not translate into a polar orbit from Vandenberg?

I found this image showing the allowable launch azimuths for Vandenberg AFB and I was wondering why a 180° launch azimuth doesn't match a 90° inclination orbit. This led me to question the equation ...
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Is the impact of Chang’e 5-T1 rocket stage on the Moon's far side on March 4th likely to launch any debris into Moon or Earth orbit?

It is predicted that the Chang’e 5-T1 rocket stage will impact the Moon's far side on March 4th. The stage apparently weighs about 4 tonnes and will impact at 2.5 km/s at a shallow angle. There's ...
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how I can find the radius vector and the velocity vector satellite in elliptic orbits? [closed]

In order to evaluate the following expression at each point in an elliptical orbit, I first need the state vector $\mathbf{r}, \mathbf{v}$. $$ \omega_j=\frac{1}{r^2||\textbf{v} \times \textbf{r}||} \ \...
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Different/better ways to calculate the shadow region passage of the satellite and the effect of orbital elements, other than shadow cone technique?

The NASA Technical Publication Method for the calculation of spacecraft umbra and penumbra shadow terminator points; TP-3547 describes the following: A method for calculating orbital shadow ...
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What are "transcritical, pitchfork, period-doubling, torus, and subharmonic bifurcations" in the context of three-body orbits? (e.g. butterflies)

MattB's excellent and well-sourced answer to Where do the butterflies land on this bifurcation plot? (Earth-Moon three-body butterfly orbits) begins: I'm fairly certain that the butterfly family is ...
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6 votes
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How frequent are (or will be) JWST station keeping burns at L2?

Does anyone have solid information regarding the scheduled/anticipated station keeping burns for JWST at L2? In an online video I've heard mention of 'every 21 days' which at first look seems ...
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Where do the butterflies land on this bifurcation plot? (Earth-Moon three-body butterfly orbits)

Below is a $\mu = 0.01215$ bifurcation plot from E. J. Doedel, E.J. et al's Elemental periodic orbits associated with the libration points in the circular restricted 3-body problem International ...
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2 votes
2 answers
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How a continuous thrust orbit transfer can be compared with Hohmann transfer?

Suppose that I have found the solution of an optimal continuous thrust planar orbit transfer from circular orbit A to orbit B by means of a numerical method. It's considered that the mission must be ...
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Is DTM2000 density model expecting adjusted or observed solar flux?

I know two models to calculate the atmosphere density during a satellite orbit propagation. The two models are NRLMSISE-00 and DTM-2000. To feed the models I'm using Space Weather Data provided by ...
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3 votes
2 answers
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How to propagate the orbit of a satellite analytically using Lagrange planetary equations/VOPs and compare them with numerically propagated solution?

I have propagated the orbit of a satellite from TLE elements numerically using RK4 method. But I'm bit confused when it comes to the propagation of satellite orbits using analytical approach. From ...
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How does JPL define the exact position of Lagrange points in the real solar system where (I thought that) they can't be defined?

My answer to Does the distance to L2 vary? is The correct answer is "No, they are only mathematically defined when the orbit is circular". but @DavidHammen's answer explains that they can ...
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4 votes
1 answer
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Can ion propulsion system be used to maintain lunar orbit?

I am doing research on propulsion systems and it was suggested that I use an ion propulsion system for a theoretical satellite I am tasked with designing, I need to maintain orbit for three years ...
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4 answers
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Does the distance to L2 vary?

Discussion of Lagrange point L2 and the JWST seem to be dropping out of the news cycle, so I thought I should ask this question while the topic is still warm. The distance of L2 for the sun/earth two ...
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Why is the eccentricity vector used to describe near-circular orbits?

When dealing with near-circular orbits I've seen the usage of the eccentricity vector defined as $$(e_x,e_y) = (e\cos\omega, e\sin\omega)$$ I've seen this in Schaubs' "Analytical mechanics of ...
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6 votes
1 answer
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With and without refilling at LEO, how much more than the landers weight of the Venera 9 mission could a Starship deliver near a pole of Venus?

Venera 9 was a Soviet space mission to Venus that consisted of an orbiter and lander with a launch mass of 4936 kg and with an entry mass of 1560 kg. It was the first spacecraft to return an image ...
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Where is Artemis on this Earth-Moon three-body bifurcation plot? Where's the near-rectilinear halo orbit for example?

Below is a $\mu = 0.01215$ bifurcation plot from E. J. Doedel, E.J. et al's Elemental periodic orbits associated with the libration points in the circular restricted 3-body problem International ...
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Has a spacecraft ever moved from one Earth-Moon halo orbit to another?

Answers to Where is the Wind going? Where has it been? (Global Geospace Science spacecraft 1994-071A) shed more light on how that orbitally gregarious spacecraft "got around" in the Sun-...
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How do I construct halo orbits around the Sun-Earth L2 point in GMAT? What should the state vector of the spacecraft be?

I am new to trajectory design, and have been using GMAT to learn it since it's free, unlike STK. I have been trying to design a script that takes a spacecraft from Earth orbit to a halo orbit around ...
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