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Questions tagged [celestial-mechanics]

Questions regarding the movements and interactions of astronomical bodies as it relates to spacecraft, their trajectories, and their maneuvers. For the motion of spacecraft themselves, see [orbital-mechanics].

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Why are orbits around a black hole not elliptic?

Most of the pictures of a black hole are like this: Source: https://cdn.mos.cms.futurecdn.net/HsDtpFEHbDpae6wBuW5wQo-970-80.jpg.webp Why are the orbits around it not elliptic? Is there any other ...
N.Li's user avatar
  • 123
2 votes
3 answers
209 views

Disposing of Obsolete Satellites by Propelling to the Sun

I'm not scientifically adept, so bear with me. Would it be feasible to retain enough fuel on new satellites/space stations, etc., that we could dispose of them when obsolete by sending them to the ...
user avatar
0 votes
1 answer
224 views

Does venus affect Earth's orbit more than Jupiter

(this question could also fit in Astronomy or Physics) Jupiter, with it's huge mass, is the obvious culprit for messing with Earth's orbit (and possibly climate). Although Jupiter is extremely massive,...
Kevin Kostlan's user avatar
3 votes
1 answer
78 views

Finding or calculating orbital velocities of celestial bodies at periapsis/apoapsis?

I'm writing a solar system simulation that uses n-body physics. To plug in the celestial bodies in our solar system, I'm copying orbital values from wikipedia. For one example, the wikipedia page for ...
xyz's user avatar
  • 31
0 votes
1 answer
185 views

Does every celestial body orbits something? [closed]

Pretty much the title is the question. Lets take the massive blackhole of our milky way does this black hole orbit something?
jordi rodriguez's user avatar
4 votes
1 answer
115 views

Meaning of superscript letters in sidereal time calculation

I'm following along with Dr Kelso's columns on CelesTrack and I've come across this equation. $$θ_g(0^h)=24110^s.54841+8640184^s.812866T_u+0^s.093104T_u^2- 6.2\times10^{-6} T_u^3$$ As you can see, ...
ScottishTapWater's user avatar
0 votes
0 answers
291 views

TEME to J2000 conversion algorithm

I've asked a few questions to do with this in the last day or so and received answers that have led to more questions... How to use David Vallado's AstroLib to do reference frame conversions https:...
ScottishTapWater's user avatar
12 votes
10 answers
4k views

Is there an elegant method to stop an asteroid's spin?

There have been proposals to mine asteroids, perhaps after “tugging” them to a more accessible location. As well, proposals have been made to move asteroids which threaten collision with earth. ...
Woody's user avatar
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2 votes
1 answer
452 views

Is this a typo in the Python Skyfield API? "International Coordinate Reference Frame (ICRF)"?

In the Python Skyfield library there is a position object skyfield.positionlib.ICRF, in the documentation it states: An (x,y,z) position and velocity oriented to ...
KDecker's user avatar
  • 365
3 votes
2 answers
192 views

Could we use Mars as as an asteroid mining base?

After getting a lot of helpful feedback I've arrived at a question: What if we setup base on Mars: I) Mine water, and split it for propellant. II) Load up light weight (expandable?) rockets with it....
Artem Shamsutdinov's user avatar
9 votes
2 answers
438 views

Why do the modified equinoctial elements use the semilatus rectum?

The classic orbit elements, $(a,e,i,\Omega,\omega,\nu)$, have annnoying singularities in their non-Keplerian perturbed dynamics at $i=0\pm \pi$ and $e=0$. So Arsenault, then Braucke & Cefola, then ...
J Peterson's user avatar
11 votes
5 answers
3k views

What processes create an object with an interstellar velocity?

An object like Oumuamua originates in a solar system. This object has roughly the inertia of everything else there. I can imagine stuff on the edge of the accretion zone for a star that...WANDER off......
Chris B. Behrens's user avatar
0 votes
2 answers
112 views

How to sort orbital positions in the order of following by spacecraft?

I have an orbiting spacecraft which keplerian elements is known. Also, I have a random-ordered list of true anomalies that represents spacecraft's positions on that orbit. How to sort this list to get ...
Robotex's user avatar
  • 604
1 vote
1 answer
243 views

How to calculate time needed for spacecraft to travel a given number of meters in elliptical orbit or hyperbolic trajectory?

We have elliptical orbit and spacecraft travelling it. I need a formula to calculate a time needed for spacecraft to travel given amount of meters starting from it's current position. Keplerian ...
Robotex's user avatar
  • 604
4 votes
2 answers
1k views

Is it possible to detect if orbits intersect or not and positions where they intersect if you know Keplerian elements (2D)?

I have two orbits and I know their Keplerian elements. Is it possible to find positions where two orbits are crossing if those positions exist? Is it possible to do it if spacecrafts are on orbits of ...
Robotex's user avatar
  • 604
0 votes
0 answers
138 views

How to calculate future true anomaly for hyperbolic trajectory? Did I make a mistake in my calculations?

I'm trying to calculate future spacecraft's position and velocity at time t. I need to calculate the true anomaly at time t for this. I've already made it for the elliptic orbits and it is working ...
Robotex's user avatar
  • 604
2 votes
1 answer
237 views

How to detect the correct sign of the true anomaly for position prediction (clockwise/counterclockwise rotation)?

I calculated spacecraft's keplerian orbital params from position/velocity using this formulas: https://drive.google.com/file/d/11KhEdFboZCPUjfibtjHaDBWtUTNmJxFA/view?usp=sharing Then I can predict ...
Robotex's user avatar
  • 604
6 votes
2 answers
357 views

Is a ballistic Jovian capture using the Galilean moons possible from interplanetary entry?

While spacecraft like Galileo and Juno did use gravity assist to supplement their insertion burns, as answered here, is it possible to enter Jupiter's orbit without a capture burn?
Enoch's user avatar
  • 317
1 vote
2 answers
232 views

How to correct my real orbit and turn it into predicted ideal orbit?

I want to launch my ship to the purple ellipse orbit. But because of non-ideal world I have non-ideal ship orientation and non-ideal thrust impulse. So, my initial speed is a bit bigger and it's ...
Robotex's user avatar
  • 604
0 votes
0 answers
79 views

How to correct orbit in case of perturbations? [duplicate]

I predicted the future position of orbital body and sent my spacecraft to that position. But the trajectory of body and spacecraft are changing because of perturbations. So, I need to correct this ...
Robotex's user avatar
  • 604
1 vote
0 answers
140 views

How to correctly change velocity in space?

The solver of the Lambert's problem gives me a hyperbolic velocity to move to some position on orbit. But the spacecraft is moving on orbit and changing the velocity takes some time. So, when I ...
Robotex's user avatar
  • 604
6 votes
2 answers
1k views

2 body equations of motion in 3D

How do you write the 2 body equations of motion in 3D as a system of differential equations
user44141's user avatar
3 votes
1 answer
160 views

For a crew-mission, in case of impromptu changes, what would be the most suitable depot locations for a re-supply?

Following the question on re-fuelling en-route to Mars, I am interested in exploring a mission architecture in which a crew may be offered different options for impromptu mission changes, for example ...
Ng Ph's user avatar
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3 votes
1 answer
105 views

Launch Elements

I already know about the six Keplerian Elements that are fundamental to a planet's orbit around the Sun, and for a few weeks now, I thought I'd got it down. Then, I wanted to have some fun, and test ...
Questioner's user avatar
-6 votes
1 answer
216 views

How exactly are we ranging distances of objects in space? Are we doing it for real or is it just a hoax? [closed]

I have been wondering, maybe some one could enlighten me as to the answer I have been looking for. I have googled, but I am after a more direct answer to this question. If light takes X time to travel ...
Maize's user avatar
  • 1
6 votes
2 answers
464 views

What is the cause of the horizontal drift in the ascend path of the Starship and other rockets?

As can be seen in the available videos on-line and in the following picture, as the rocket ascends, a horizontal drift in its path can be seen. I have forgotten the calculation of the Coriolis effect ...
Kamran's user avatar
  • 111
4 votes
0 answers
99 views

Why does ESA's TGO satellite not permanently serve as relay for Perseverance?

This question is about the orbital parameters of ESA's ExoMars Trace Gas Orbiter (TGO), so I am optimisitic that it belongs on astronomy SE. More specifically, it is about the orbital geometry of TGO ...
B--rian's user avatar
  • 215
1 vote
0 answers
73 views

Calculating the length of a launch window?

May somebody guide me what exactly determines the length of a launch window? When doing the (basic) celestrial mechanics caclulations for e.g. a transit from Earth to Venus, one usually assumes point-...
B--rian's user avatar
  • 215
4 votes
3 answers
264 views

How do space agencies choose arrival dates to planets (i.e. Mercury) from a gravity assist (i.e. Venus)?

Assuming I was looking for arrival opportunities from 2020 to 2030, how can I calculate the possible arrival dates to Mercury given a departure date from a gravity assist from Venus?
John's user avatar
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23 votes
5 answers
6k views

Can a moon orbit its planet faster than its planet rotates?

Can a moon orbit its planet faster than its planet rotates? Can a moon orbit its planet more than once per the planet's day? It seems possible but I'm not sure. Are there any known examples of this ...
user38319's user avatar
  • 255
5 votes
1 answer
322 views

Why is the gas giant grand tour interval 175 years when the synodic period of Uranus and Neptune is 171 years?

The "Grand Tour" path Voyager 2 took, flying past Jupiter-Saturn-Uranus-Neptune, repeats every 175 years. As the original paper by Gary Flandro puts it: Earth – Jupiter – Saturn – Uranus – ...
SE - stop firing the good guys's user avatar
1 vote
0 answers
55 views

Calculating Orbital Velocity without Semi-Major-Axis

When playing Kerbal Space Program, I realized that there is a difference between surface speed and orbital speed; this difference is quite variable, although the Kerbin's surface speed is only 175 m/s....
John's user avatar
  • 11
2 votes
0 answers
82 views

Can the location of an unknown planet that is absent from a planetary system be calculated from the orbits of the remaining planets?

In the book ‘Seeker’ by Richard McDevitt, two characters search for a lost planet. They know the star system currently has a number of celestial bodies in orbit around it and their orbits are ...
aquagremlin's user avatar
3 votes
0 answers
212 views

How to calculate the maximum heliocentric speed during a flyby?

The following graphs are related to the Voyager 2 / Jupiter flyby occurred on July 1979 (I did the calculation with the SPICE library and NAIF’s data files). We see that the maximum speed relative to ...
Cristiano's user avatar
  • 1,750
2 votes
1 answer
113 views

Could the orbit of a satellite place it on the z-axis of the ECI coordinate frame (x=y=0)?

It is mostly a hypothetical question; I assume the answer is no, but I am looking for any data to contradict my claim that there are none or at most only one satellite at a time which could ever ...
tdMJN6B2JtUe's user avatar
1 vote
0 answers
98 views

How is it possible to connect trajectories at a Poincare section using the "bisection" method?

When constructing a heteroclinic connection (a connection between two different periodic orbits at two different libration points), the stable and unstable manifolds of two different libration points ...
John's user avatar
  • 1,377
3 votes
1 answer
126 views

What does the term "libration point gateway" mean?

In the Circular Restricted Three Body Problem, natural paths exist between periodic orbits or the libration points that have negligible cost. These are commonly known as free transfers between ...
John's user avatar
  • 1,377
2 votes
1 answer
316 views

Is the Jacobi constant stationary along a periodic orbit?

In the book called "Chaotic Worlds: from Order to Disorder in Gravitational N-Body Dynamical Systems", link here, the author states that if the dynamical system has an integral of motion which is not ...
John's user avatar
  • 1,377
8 votes
1 answer
2k views

What is the physical interpretation of the eigenvalues of the monodromy matrix and how are they associated with the invariant manifolds?

To define the monodromy matrix, assume that the period for one cycle of a halo orbit is denoted as $T$, the initial time as $t_0$, and the state-transition matrix is defined as $\phi$. Then, the ...
John's user avatar
  • 1,377
9 votes
4 answers
9k views

Calculate flight path angle given semi-major axis, eccentricity and distance from the focal point

How can I, given the semi-major axis (α), the eccentricity (ε), and the distance from the focal point (r), calculate the flight path angle (φ)? (As shown above)
konmal88's user avatar
  • 193
3 votes
2 answers
2k views

What is the analytical closed-form solution of the two-body problem to verify its numerical integration results?

The purpose is to study the motion of two celestial bodies analytically. What is the closed-form of the two-body problem if I was to solve it analytically without using a numerical approximation ...
John's user avatar
  • 1,377
1 vote
0 answers
94 views

Why does the Sun track out a seemingly sinusoidal path on the celestial sphere? [closed]

I know it's somehow related to the way things are projected but it hasn't quite clicked yet. The question arose because I wanted to understand the path of the eclipitic after reading about it here: ...
keynes's user avatar
  • 11
11 votes
1 answer
732 views

Why is FORTRAN recommended for astrodynamics rather than MATLAB?

I understand that FORTRAN might be faster in terms of computation time, but I don't understand why it is always recommended by people in the field. Everyone tends to avoid MATLAB for astrodynamics; is ...
John's user avatar
  • 1,377
3 votes
2 answers
2k views

Geocentric latitude and longitude of sub-satellite point

I was trying to derive the expressions for the geocentric latitude and longitude of the sub-satellite point using Keplerian elements. The final equations connecting the combination of the Keplerian ...
budding physicist's user avatar
3 votes
2 answers
1k views

STK Astrogator Earth Flyby

TLDR: How do you set up an EEV maneuver, specifically, how do you go from an earth orbit to a heliocentric orbit with a periapsis within Venus’s orbit in astrogator? I know the theory but astrogator ...
Joe Blow's user avatar
  • 131
4 votes
1 answer
751 views

What does "Poisson's formula" refer to in this calculation?

I am not entirely sure if this question belongs to this forum, but I don't know where else to ask. I am following a Rocket Propulsion course. There is a section concerned with the Velocity ...
Roger Pedrós Bòria's user avatar
1 vote
3 answers
3k views

Do Kepler's laws of planetary motion apply also to satellites of the Earth?

Do Kepler's laws of planetary motion apply also to satellites in orbit around the Earth? I would assume yes, but I'm not sure why...?
Nancy Gutz's user avatar
6 votes
1 answer
4k views

C3 calculation in interplanetary missions

I'm starting to study Astrodynamics and I'm trying to make a Porkchop plot for a Mars mission to compare the results with actual porkchop plots which I found on the internet, so I know if my ...
Alberto De Celis Romero's user avatar
2 votes
0 answers
727 views

How to get the coordinates from NASA JPL Ephemerides DE430 ( ECRS) to ECI?

I'm trying to make a software that determines the orbit of a satellite which is affected by the Sun and Moon. The coordinates [x y z] that I have for the satellite are in Eci. For the position of the ...
Alexandru Lapusneanu's user avatar
2 votes
0 answers
537 views

How to derive the differential equations of motion for a dumbbell system ,eg. dumbbell satellites around earth?

From Eq. 2.13 from Orbital Mechanics for Engineering Students (Curtis, 2005) the equation of relative motion between two bodies orbiting around a center of mass can be written as: $$\ddot{\mathbf{r}}...
CSpitzer's user avatar