# 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].

1,178 questions
Filter by
Sorted by
Tagged with
72 views

### Free Return Transfer Problem

I'm trying to understand how a free-transfer return works. It makes sense to me conceptually, but putting numbers to it it is unclear. I'm not sure how to obtain information about the transfer ...
68 views

### Good example of early and simple orbital mechanics?

I am doing a talk on Katherine Johnson at my school extremely soon and I was wondering if you could give a relatively quick example of a simplified calculation in any kind of orbital mechanics ...
540 views

### Velocity of a rocket needed to get to Mars

At 2:16 in this video, Don Pettit says he used the Rocket Equation to determine the velocity of the rocket needed to travel to Mars, which was 16 km/s. I am not sure as how he did it though, and was ...
171 views

### Could a solar sail composed of smart glass stay near the L1 point of Venus?

From answers to this question i've learned that the Lagrangian L$_1$ point of Venus is not stable, despite the almost circular orbit of the planet and the fact that it has no moon. Nevertheless would ...
151 views

### Circular to elliptical orbit delta V requirements

this might be a dumb question, but i've been recently trying to calculate the delta V to deorbit a satellite, and I've run into a problem. Assuming a 400km circular starting orbit(and disregarding ...
4k views

### How does a Spacecraft change its orbit?

I am a high school student. I saw the latest Indian spacecraft "CHANDRYAANN 2", which was in orbit around the Earth for 14 days..... I am so curious to know how a spacecraft changes its orbit. I ...
175 views

### How to find the optimal launch trajectory for a rocket launched from a planet with an atmosphere?

I originally asked this question on maths stack exchange As the title states I am trying to find the optimal launch trajectory for a rocket launched from a planet with an atmosphere (Earth) in order ...
92 views

### Inclination maneuvers for GEO satellites

I was wondering about the orbital location to perform inclination nulling maneuvers for GEO satellites. I know from basic astrodynamics that the best place to perform inclination correction is at ...
140 views

### Better launching location to Neptune

I'm a big fan of space movies, especially when they're based on actual science and/or near-future. So of course I went to see Ad Astra (IMDB). In a nutshell, Brad Pitt's character flies into an orbit ...
71 views

### How does the “eccentricity-inclination vector separation” technique work for colocated GEO satellites?

This answer to How are co-located satellites positioned relative to each other? links to the paywalled paper Separation of Geostationary Satellites with Eccentricity and Inclination Vector with the ...
354 views

### Orbital mechanics: Jump from ISS, where will I meet again?

This is a hypothetical question, and I hope it is on-topic here. If an astronaut would stand on the surface of the ISS, and they will make a jump directed perfectly towards the earth, what will their ...
110 views

### Finding Equations for all of the Orbitals of the planets - IB Math IA

I am doing an IA for an IB math course and my topic is "have/will all the planets ever come within a certain degree of each other?" I am starting out by nullifying certain aspects that would make ...
74 views

### Interplanetary Taxi Orbit

I would like to know the feasibility of an interplanetary "bus" or "taxi" which moves between, say, Earth-Mars or Earth-Venus without entering the orbit of either. The idea is that the taxi is large--...
387 views

### Lightsail-2: Increased Orbit from Sunlight or Lowering Periapsis?

Has Lightsail-2 really increased the total energy of its orbit by utilising energy from sunlight, or has it simply exchanged energy by lowering its periapsis in order to raise its apoapsis? And if so, ...
40 views

### How to deteremine the angle between Sun and 2 probes?

I have the orbital position and velocity and the orbital parameter of 2 spacecraft at LEO, how to define the angle between Sun - Probe 2 - Probe 1 in ECI frame (If you imagine at a point sun then ...
90 views

### Issue with SGP4 modelling from scratch in MATLAB

I am trying to develop the code from this source , this research paper and from this too as same as bibliography of that aforementioned source. So, here as you can see at page 14, they have defined ...
189 views

### Orbital vocabulary confusion! How can the tangential velocity of an elliptical Kepler orbit not be tangent to the orbit?

I'm now officially confused about the usage of "tangential" when breaking down orbital velocity components. It started with edits and comments on this answer to Orbital speed is (vector) sum of ...
132 views

### What would be different about satellite orbits if Earth were prolate? Would we have Sun-synchronous and Molniya orbits?

It's hard to imagine how it could happen naturally since on geological timescales the Earth would either be spherical if it didn't rotate, or oblate if it did, but from an orbital mechanical ...
159 views

### How to calculate the radii of high orbits above the parallels of 45 and 80 degrees?

The new theories in the field demonstrate the possibility of non-Keplerian orbits. https://www.pourlascience.fr/sd/spatial/de-nouvelles-orbites-geostationnaires-10636.php I am interested in ...
140 views

### Did Juno just do a plane change? If so, by how much?

There are several reports in the news that the Juno spacecraft executed a very long propulsive maneuver so that it wouldn't pass through Jupiter's shadow. Apparently it would be in dark so long that ...
64 views

### Point Ahead Angle Calculation between LEO-GEO Satellite (ISL Scenario)

So, I have got two reference TLE from 2 different Satellite in LEO-GEO, which are as follows: (1st TLE for LEO, 2nd TLE for GEO) ...
171 views

### Do orbits change over a period of time, especially when the Star is not at the center (example: Didymos)?

Consider a celestial body, say the asteroid Didymos for example, with an elliptical orbit around the Sun. Now since the Sun has a huge gravitational pull and mainly because it is not at the center of ...
166 views

### When going to Mars, how do you measure exact distances to determine course corrections?

When probes fly to Mars, they must adjust their trajectories multiple times during transit to ensure correct orbit insertion. They fire their small onboard rockets a little bit to do this. But how do ...
3k views

### What kind of mission objective would make a parabolic escape trajectory desirable?

As far as I can tell, a trajectory with zero excess velocity would place it (essentially) in nearly the same orbit around the sun as earth (assuming it even departs far away enough for the sun’s ...
117 views

### Besides hyperbolic flybys, what are all the other cases where the Oberth effect can be used?

For hyperbolic and parabolic flybys it's common to take advantage of the Oberth effect and get the most delta-v from a propulsive impulse by doing it at the point of maximum velocity. Question: But ...
54 views

### Trivial lower bounds for single point mass delta-v problems?

Given two arbitrary elliptic orbits around an ideal single point mass, there will always exist a transfer with the minimal $\Delta v$ required. It's easy to find an upper bound for this ideal ...
32 views

### Velocity Vector Transformation for Point Ahead Angle and Doppler Shift Calculation for Inter-Satellite Link

So, I have the Radial and Tangential Velocity Vector (like in Figure 1) and also the Cartesian coordinate of 3D velocity vector. For reference, you can see in this link. Where, $o_{dot}$ vector matrix ...
6k views

### Does it require less energy to reach the Sun from Pluto's orbit than from Earth's orbit?

Somewhat inspired by this question and its answers, does it require less delta-v for an object to fall into the Sun the further away it is from the Sun? It makes sense that an object has to shed its ...
141 views

### Point Ahead Angle and Doppler Shift Frequency Changes Calculation with the tangential/radial velocity component for Inter-Satellite Link

While calculating the Point Ahead Angle we work with Tangential Velocity vector component and to calculate the Doppler shift i.e changes in frequencies, we work with Radial Velocity Vector component. ...
125 views

### How does the orbit of the Voyager and New Horizons probes manage to get into interstellar space?

I understand that every probe launched has been launched into an orbit. The further you want to go into the solar system, the faster it needs to be moving. And everything orbits the sun until it finds ...
177 views

### What is the purpose of orbital frame of reference for a satellite orbiting the earth?

Orbital frame of reference: a frame of reference with its origin on the orbit and x-axis pointing towards the velocity vector and z-axis towards the center of mass of the earth. the y-axis completes ...
57 views

### I consider it possible to reposition orbitals without reboost and no thrusters I would like to discuss this Idea with someone? [duplicate]

Ok I'm going to label this idea "Skiing in Space" as that analogy is possible the simplest to grasp the concept. When a person moves on skis he/she has to shift body weight to the relevant side to ...
71 views

### Why do the optimal thrust vectors point so far away from the velocity vector for the Psyche mission?

The question Psyche 16 - What will be learned in 2026? got me reading Wikipedia's Psyche (spacecraft) which links to the 35th International Electric Propulsion Conference paper Development of the ...
589 views

### What target is the most difficult to reach in the solar system?

"Most difficult", as in the minimum $\Delta v$ required, the objective being capture into an orbit around the object. Looking through some Delta-v maps, I would suspect the answer to be some inner ...
970 views

### Transform ECI to ECEF

I need to transform ECI to ECEF coordinate. Here, I need the formula in math and algorithm. I have looking for the formula in the internet, but I can find one. I have x, y, z cartesian coord in ECI. ...
91 views

### Orbital insertion with “inertial parachute”?

Inspired by Is there any way to land a rover on the Moon without using any thrusters?, but off-topic as a solution as that question asks specifically about crumbling zones. The idea: A spacecraft ...
200 views

### Why is Wikipedia's delta-v from the Moon to Mars transfer so much lower than mine?

I tried to write a nice answer to this first question by a new user, but I've crashed and burned. I calculated the escape from the Moon to be about 2,376 m/s which is close to 2.3 km/s shown in the ...
159 views

### Can the electric field of the Earth's be used for satellite maneuvering?

Is it feasible to create a strong dynamic dipole inside a satellite so that it can be rotated on its axes and even possibly pushed in a direction due to the Earth's Normal Electric field. This might ...
113 views

### What does Cees Bassa's Doppler plot of Chandrayaan 2 show?

Cees Bassa's tweet shows a plot of received frequency versus time, with the Doppler shift of the Moon's center of mass subtracted. For a lunar orbit the resulting plot would show sinusoidal-like ...
132 views

### Generating TLEs with STK Using SGP4 Propagator;

STK has two methods for generating TLEs; Trajectory Sampling method and Single Point method. I have read the differences both of them at http://help.agi.com/stk/index.htm#stk/tools-10.htm but I am ...
123 views

### What do all these vectors point to in this New Horizons trajectory/operations simulation?

Sir Brian May's New Horizons music video (below) shows an animation of the spacecraft and its launch vehicle from countdown to MU69 Ultima Thule. Part way through the video at about ...
133 views

### Could a trajectory from Earth really wrap around Jupiter and then head straight into the Sun? [duplicate]

Comments below How much less delta-v would it take to reach the Sun using Venus and Earth flyby's compared to direct? tend to suggest that one way to send a spacecraft into the Sun (either straight in ...
462 views

### What is the highest velocity a spacecraft has left Earth?

The comment below @TomSpilker's answer I'd love to see anything in LEO that can impart 20.89km/s of delta V to anything. got me wondering what the highest velocity a spacecraft has left the Earth,...
142 views

### How much less delta-v would it take to reach the Sun using Venus and Earth flyby's compared to direct?

@TomSpilker showed that the minimum delta-v to go from Earth orbit into the Sun is about 20.89 km/s. That's going from 200 km LEO to "perihelion at the sun's photosphere (guaranteed complete entry!)" ...
50 views

### Delta-v cost of longitudinal plane change correction?

In a recent question, the slow drift of a landing site on a rotating body relative to an orbiter came up. This would sometimes require a plane change correction when one desires to recover the ...
1k views

### Was the lunar landing site always in the same plane as the CM's orbit?

Did the Apollo command module always pass directly over the lunar landing site? Or were they sometimes in different planes? My inclination (pun intended) is that staying in the same plane would ...
698 views

### What's the eccentricity of an orbit (trajectory) falling straight down towards the center?

Discussion below this answer has got me thinking. A circular orbit has eccentricity of $\epsilon = 0$, ellipses $0 < \epsilon < 1$ (between but not including 0 and 1), and parabolic and ...
3k views

### slowest crash on the Moon?

Let's say I launched something into lunar orbit with minimal of propellant - just enough for trajectory corrections and then a final push to de-orbit. What is the slowest crash landing speed (both ...
99 views

### Help Finding A Book

I am trying to find the book that contains the following chapter: https://www.faa.gov/about/office_org/headquarters_offices/avs/offices/aam/cami/library/online_libraries/aerospace_medicine/tutorial/...
200 views

### Is it possible to identify the main systems that would be present in a generalized space station?

What are the main parts of any space station? I have been making a 3D model of a hypothetical space station, and I'd like to ask if it is possible to identify some main components and/or subsystems ...