Questions tagged [astrodynamics]

The study of satellite orbits and space flight dynamics.

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Apse Line rotation maneuver in GMAT

How should I perform Apse line Rotation Maneuver in GMAT? Both orbits have same orbital elements except for the argument of periapsis. I have found out the intersection points and now and have also ...
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Initial Value in Vary Command (GMAT)

What number should I give as an initial value in GMAT's Vary command? I have been trying to use default values but in some missions this default value does not lead to the convergence of target or ...
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Space-track SGP4 on MATLAB

I am new to orbital calculations and online resources, so I was hoping someone would be willing to help me get started. I have downloaded the space-track Astrodynamic standard library and I am ...
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Multiple Stopping Conditions in GMAT Propagator [closed]

How can I specify multiple stopping conditions in GMAT? Propagate Synchronized DefaultProp(A){A.Earth.Latitude == '81.7570' & A.Earth.Longitude == '262.5365'} DefaultProp(B); I have tried this ...
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How to propagate satellite to orbit intersection (relative node) in GMAT? [closed]

I am trying to propagate the spacecraft to the intersection points of two orbits (relative node) in GMAT. The analytical calculations of the true anomaly of that point is done using the formulas in ...
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Earth to Mars Transfer using GMAT

I saw a couple of people mention here that in order to change the epoch date from the given Mars transfer example on GMAT I would need to change and re-optimize initial conditions. How would I do that?...
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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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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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Ноw to configure mission sequence for propagate until desired date in GMAT?

In GMAT, I have a state of satellite for a date (for example, 24.04.2022). Now, I need to propagate its motion for some days forward, until selected date (say, 29.04.2022). I added Propagation into ...
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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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Conversion of velocity vectors between ICRF frames with different central objects

Following the very nice answers to this question, I am trying to implement an appropriate procedure for change of central body during orbit propagation. The very interesting thesis by Mana Vautier ...
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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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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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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 can we determine the most appropriate central body for orbit propagation?

I have recently been experimenting with expanding my numerical propagator to satellites that orbit central bodies other than Earth. I started with the Moon (using GRGM1200B gravity model), and found ...
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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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Mission maneuver to Enceladus, I have some results from JPL trajectory browser, what comes next?

I am working on a project titled 'Astrodynamic mission maneuver to Enceladus'. I have found the launch date using NASA trajectory Browser. Can you let me know how to proceed further?
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How can I find the x, y position of apogee and perigee, if I only have the value of distance vector (position) and velocity vector?

I am currently working on a 2D space simulator where I have two bodies; one is still and other is an orbiting object, which I can also control like a rocket. I'm using the Newton's gravity: $F = \...
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James Webb Space Telescope Velocity Loss Formula or how fast will JWST be going on L+26

I was never great at math but now I wish I would have taken it more seriously. We have an office bet going and I need to come up with a formula to figure out the future velocity the JWST. I was able ...
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ISS propagation becomes much more accurate with reduced drag. Any ideas why?

I have currently been testing my implementation of a numerical propagator with the ISS. Without going into much details, the propagator considers Earth gravity (with the GGM03S model including zonal, ...
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Please explain a way of calculation of Lagrange multiplier in algorithm of low thrust transfer

In David Vallado's book 'Fundamental of Astrodynamics and Applications', chapter 6.7. ("Continuous-Thrust Transfers") there is an algorithm #47: Low Thrust Transfer. In this algorithm a ...
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4 answers
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Why are uncertainties of orbital state vectors provided as covariance matrixes?

I have recently become interested in testing a numerical orbital propagator with ISS ephemerides, following @RyanC's suggestion in this answer. Ephemerides for the ISS seem to be publicly available in ...
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"Hohmann-Like" and Chemical / Electric Thrust Comparison

Part of the work I have to do for my degree is to perform a "Hohmann-like" transfer between Earth and Mercury, of which I believe I have accomplished. I have attempted numerous times to ...
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GMAT B-plane Transfer to Mercury

I have been fighting with GMAT for about 3 days now trying to get this transfer to converge so literally ANY assistance and advice would be greatly appreciated. I need to do a direct hohmann like ...
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How to perform a Hohmann-like transfer to mercury on GMAT

I am trying to simulate a Hohmann-like transfer from Earth to Mercury and establish an orbit there on GMAT. I have the following values already: launch velocity (22.25 km/s) Launch burn (-7.53 km/s) ...
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4 votes
2 answers
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SPICE toolkit occultation finder doesn't work with spacecraft

I've to know if the sun is occulted by earth from my spacecraft which is in low earth orbit with these parameters (a:6700 km, e:0.0, i:5°, ...). I run the following method with search window start at ...
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What does it take to be an Astrodynamics Engineer?

Astrodynamics is really complicated and requires some incredible intuition for not just physics, but math and programming. Most job descriptions for Astrodynamics Engineer say something about a degree ...
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2 votes
1 answer
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Pure orbit inclination changing, why delta v differs between vector and numerical approach?

as said in the title I have different results between numerical en vector approach during inclination changing maneuver. The initial orbit : Perigee radius : 6700 km Eccentricity : 0.7 Inclination : ...
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Does other orbital parameters change on plane alignment impulsive maneuver?

I work on small application to apply impulsive maneuver on an orbit. I want to align two orbits in the same plane. After the execution of the function, original orbit has the same inclination and ...
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Find the Orbital Inclination given all other Elements and a Position on the Ellipse

I'm in a situation where I need to determine an orbit's inclination. At my disposal I have all of the orbit's other Keplerian elements, and I have the vector of a single point on the ellipse. Is ...
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Do fins with slightly different masses but the same surface area affect the stability of a rocket?

Each of four fins of a rocket are of slightly different masses like( 0.204, 0.2, 0.199 and 0.19 kg). If they have the same surface area, will that severely affect the stability (spin) during flight? I ...
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3 votes
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How would you calculate the Delta-v needed to intersect a target on the ground on a sub-orbital trajectory?

Let's say I have a sub-orbital trajectory, meaning I'm going to crash into the earth at some point within the first orbital period. I know the true anomaly in which I will impact the surface and by ...
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1 vote
1 answer
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How to calculate velocity vector in perifocal coordinates [closed]

Well the formula for it is here: Though if r is the radius and f is the true anomaly (which I assume is radians), then what is r dot and f dot respectively?
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How would you convert keplerian orbital elments into cartesain vectors with quaternions?

Coverting the keplerian elements to cartesain vectors ( posistion and velocity) is relatievly simple by using rotation matrices show in the document here: https://downloads.rene-schwarz.com/download/...
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Does a spaceship traveling to Mars from Earth via orbital skyhook still have to wait for a transfer window? [closed]

In order for it to make the three months travel time does it still have to wait for a transfer window or can it go at any time of the year?
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Difference between rotated frame and rotating frame

Suppose we have a spacecraft orbiting around Earth and we neglect all effects of Earth's $z$-axis motion, i.e., no wobble, precession, or nutation. For simplicity, we only assume a rotation rate $\...
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4 votes
2 answers
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Where can one find the accelerations due to high-order terms of the geopotential model?

The expression for the orbital perturbation due to J2 ($\mathbf{a_{J2}} = [a_r \ a_s \ a_w]^T$) as well as its derived effect on the argument of perigee and the right ascension of the ascending node ...
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Hill approximation of the CRTBP (Circular Restricted Three-Body Problem) derivation

Dear fellow space enthusiasts, Let us first consider the classical CRTBP equations of motion by defining the position vector of the spacecraft \begin{equation} \boldsymbol{r}=[x,y,z]^{T}, \end{...
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Working out time spent by spacecraft above certain latitudes

I'm currently working through some practice exercises and one is about how many minutes per orbit a spacecraft spends above a certain latitude. How can this be calculated? I can't find any equations ...
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Using the Clohessy-Wiltshire equation, what would be the expression for ' r '?

I'm looking for an expression for r. The difficulty I'm facing is simplifying the C-W equation
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2 votes
1 answer
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How can we express velocity of the Apollo mission relative to a moon-centered reference frame instead of an inertial reference frame?

I am really interested in the Apollo mission and I was wondering how fast did the astronaut pass by relative to the moon. I wanted to compare it with the speed of the car. I have been able to ...
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5 votes
1 answer
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Does the short-angle solution of Lambert's Method break down for very Delta-V intensive maneuvers?

Just a (hopefully) quick qualitative question that I'm having a bit of trouble extracting from the literature: I've implemented a universal-variables Lambert's method in python, and it has been ...
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13 votes
1 answer
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How to choose the best direction to leave Earth's sphere of influence?

What direction is optimal for spacecraft to leave Earth's sphere of influence (SOI) when it's going to an outer or inner planet? Let's presume that we have a spacecraft in a circular LEO (ecc=0.0). ...
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2 votes
2 answers
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Is it more efficient to burn all needed fuel in an Oberth manoeuvre at once or burn a fraction of the fuel for each orbit?

I was looking into Parker Solar Probes trajectory and was wondering what would be the most optimal way to utilize a retrograde thrust at perihelion to reduce the number of needed gravity assists. I ...
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1 vote
2 answers
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Apparent Centering Problem When Using the Perifocal System to Draw Orbital Ellipses

I am attempting to render orbital ellipses in software. Given a set of orbital elements, I am using the Perifocal system to determine a set of points along the curve of the ellipse. I am using the ...
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Does Kepler's Method for Determining Time of flight between two True Anomalies break down with eccentricities approaching 1?

Pretty simple question here. I'm calculating time of flight between two true anomalies by converting those true anomalies to mean anomalies and using the following equation: $\Delta t = t_2-t_1 = \...
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5 votes
3 answers
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Speed at aphelion is decreasing for Parker Solar Probe with each new orbit despite being closer to the Sun

Sorry for the really bad picture I am looking at some data from the Parker Solar Probe mission and I was looking at the speeds of PSP at perihelion and aphelion at each new, different, orbit (the ...
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1 vote
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Fundamentals of Rendezvous and Proximity Operations

I am trying to work out how to calculate / model a rendezvous and proximity operation between two spacecraft. I have read several research papers, but none of them walk me through step by step how to ...
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8 votes
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Increase in period and semi-major axis following near head-on collision between Cerise and Ariane debris (1996)

This report describes the collision of the French satellite Cerise with a piece of Ariane rocket debris (object no. 18208) in 1996: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?...
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