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# Questions tagged [orbital-mechanics]

Orbital mechanics (also called astrodynamics) is the application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft on an orbital or escape trajectory. For the movements of celestial bodies, use [celestial-mechanics], not this.

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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 ...
1 vote
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### What is the difference between these two Universal Gravitational Constants? [closed]

Can someone please help understand when to use each of these Universal Gravitational Constants. G = 6.67 x 10-11 N•m2/kg2 G = 6.67 x (10^(–11)) N(m^2) (kg^(2)) compared to G = 6.67 * 10-11 m3/kg-1s-2 ...
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### ISS (ZARYA) TLE to Latitude Longitude Conversion

I am trying to take TLE of ISS (ZARYA) and get the latitude longitude and height. I am aware the TLE is in TEME~(True Equator Mean Equinox) frame. This means that the TLE was generated considering the ...
2k views

### How to calculate the time to reach a given true anomaly? [closed]

I'm looking for a general formula or procedure calculate time to reach any given true anomaly.
117 views

### How would one obtain the longitude of satellite at the apogee?

I know that apogee longitude is a design point in Molniya orbits. Given the classical orbital elements, how can I find this value?
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### Orbit prediction for satellites using the Kepler model

I would like to know how to model the motion of satellites in orbit using Keplerian, i.e. develop a simulation model that tracks paths of satellites using Keplerian orbits in Python?
3k views

### Delta-v to hit the moon: is reaching Lunar L1 enough?

Lot of questions involve shooting things into the Sun. But there are no aliens on the Sun: they are on the Moon. I want to drop things on them, but since there's lot of them, I can just drop a ...
225 views

### Will this homopolar motor self rotate in a vacuum?

Is it convenient to ask about the motor from the link: Roller Homopolar Motor When it is on the table, the motor rotates freely, together with the attached conductor. Will the upper motor in the ...
647 views

### Orion re-entry velocity: Why is it higher than Apollo?

Title says it all. I am puzzled why Orion will be traveling faster than Apollo.
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### Which notes and/or books on mathematics, physics, 3D geometry preparatory to the study of orbital dynamics?

I have a master's degree in aerospace engineering and I'm preparing for job interviews for orbital mechanics/space flight dynamics engineer positions and I need material about maths, physics, 3D ...
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### What's the motion of two connected satellites orbiting the Earth after their separation?

Let's consider the following problem (it's a job interview question): two satellites are orbiting the Earth in a circular orbit; they are rigidly linked by a tether which is always pointing in the ...
235 views

### Can electrodynamic tether propulsion use the solar magnetic field?

Electrodynamic tethers have been proposed for satellite propulsion in the magnetic fields of Earth and the Gas Giant planets. Is it realistic to consider using the Sun's magnetic field for ...
376 views

### Roughly how many kinds of closed or periodic orbits are there in the circular restricted three-body problem?

Question: Roughly how many kinds of closed or periodic orbits are there in the circular restricted three-body problem? Has anyone made an attempt to enumerate and classify/categorize them? Notes: If ...
1k views

### How do we define the aphelion of Earth?

After seeing this question, I was curious on how we define the aphelion of Earth. On a quick search it said that the aphelion is the point when Earth is the furthest way from the sun. However, all the ...
1 vote
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### How do you calculate the characteristics of an orbit of an object launched from a mass driver?

What formula can I use to calculate the apoapsis of the orbit of an object launched from a mass driver on the moon at a given speed and angle to the surface (angle from horizontal)? The device will ...
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 ...
1 vote
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### Moving target during rendezvous

I am currently studying rendezvous and docking. I noticed the elliptic Hill equations only consider the acceleration of the target satellite due to its elliptic orbit (and fictitious forces in LVLH ...
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### 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 ...
2k views

### Distance from earth to another planet in solar system

Initially I thought that the problem is trivial, but it turned out to be something relatively complex. I found no one place that would answer the question directly nor a quick guide showing what ...
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### Why will JUICE take 8 years to reach Jupiter, longer than any earlier spacecraft?

Galileo took six years from Earth to Jupiter. Cassini-Huygens took three years to reach Jupiter and six years to reach Saturn. New Horizons took one year to reach Jupiter. Juno was launched in 2011 ...
231 views

### Calculate position of planet on fictitious orbit each day

I'm a software developer but my degree with in mathematics. I'm trying to develop a game/simulation of a fictitious randomly generated solar system, and trying to work out how to model and calculate ...
143 views

### TEME state vector to TLE orbital elements

I was looking at time series of some TLE parameter(semimajor axis, inclination, etc..) and I wanted to how those parameters evolve between measured time points. So i decided to feed TLE element to ...
140 views

### Positions of asteroids in heliocentric ecliptic (x,y,z) coordinates

I would like to make positions of asteroids in heliocentric ecliptic (x,y,z) coordinates plot for a given date, like in the image below (Matsuoka N. Ryo (CC-BY 4.0)). For that I need so-called state ...
4k views

### What causes a satellite's orbit to decay?

Why do orbits of satellites orbiting at sufficient speed, far beyond the Earth's atmosphere, decay if there is no atmospheric drag? What drag is applied on the satellites at that altitude?
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### I want to simulate the antenna pointing error when tracking LEO satellites

I am trying to simulate the antenna pointing error of our antenna when tracking LEO satellites using TLE data. I am using the Skyfield library in python. First I loaded the TLE data from the Celestrak ...
130 views

### Negative elevation angle

What does it mean to have negative values of elevation angle from the low-Earth orbiting (LEO) satellite? Can the negative values of elevation angle be useful?
56 views

### Approach to Interplanetary Transfers in GMAT

I hope to find a straightforward process for designing interplanetary missions using the General Mission Analysis Tool (GMAT). This would involve calculating the required initial state, timing, and ...
2k views

### Help with fictional scenario: trapped in Lagrange Point orbit

I'm a full-time screenwriter trying to create a realistic sci-fi scenario, though not necessarily a hyper-realistic one like those in The Martian. Think more along the lines of pseudo-scientific ...
265 views

### Is it possible to create an analytical ephemeris from raw position and velocity of a Body?

I would like to have an analytical ephemeris for various bodies of the solar system (planets, natural satellites and asteroid). I have at my disposition spice kernels from which i can extract position ...
720 views

### How close do gravitational 2-body hierarchy levels get?

Due to very few 3-body arrangements being stable (this question thus excluding co-orbital objects like trojans), objects in space usually arrange themselves in a hierarchy of 2-body systems. When the ...
14k views

### Falcon 9 g-level/acceleration profile

I want to get an idea of how long the falcon 9 rocket accelerates and at what g level. Ideally a plot of gs vs time. I see various statistics like specific impulse and thrust and weight, is there a ...
5k views

### How did theorists determine that the atmosphere attenuates enough to support unpowered orbits?

Before getting rockets into space were scientists certain that the density of the earth's atmosphere would decrease with height enough to permit low earth orbits? If so how was that determined? (If ...
7k views

### Why is a near rectilinear halo orbit proposed for LOP-G (formerly known as Deep Space Gateway?)

Why is a near rectilinear halo orbit a good place for a Lunar Orbital Platform-Gateway (formerly known as Deep Space Gateway)? Are there specific logistical and orbital-mechanical advantages over ...
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### Change of inclination using low thrust

I am studying low-thrust maneuvers, in particular a change of inclination only. According to (Ruggiero et al., 2011)[1], if one writes the perturbation force in the Gauss planetary equations in terms ...
4k views

### What is the most fuel efficient way out of the Solar System?

I understand with current technology we can't just fly a straight line out of the solar system but which way out would need the least fuel? Currently to navigate the solar system it is a dance ...
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### Could a “solar gravitational synchrotron ” use solar thermal rockets to "powerslide" spacecraft out of the solar system?

Could a “solar gravitational synchrotron ” use solar thermal steam rockets to launch spacecraft out of the solar system? Solar thermal steam rockets https://en.wikipedia.org/wiki/Steam_rocket have ...
381 views

### Could the Lunar Lagrange Points work for space telescopes?

Every orbit in space has its pros and cons. Low Earth Orbit has accessibility but frequent eclipses whereas a Solar Lagrange Point is clear and stable but distant. In the case of the Lunar Lagrange ...
8k views

### Mars transfer window frequency

According to this website I drew up a timeline of Mars transfer windows and the time you'd need to stay on Mars before the next return window: Blue to red arrows are Earth to mars transitions, red ...
152 views

### 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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### What happens to orbit after a radial burn?

We know from Hohmann or bi-elliptic transfer maneuvers that a burn in the tangential direction of an orbit changes the radius of the orbit. But what happens to an object in orbit, when there is a burn ...
278 views

### How do I obtain geocentric position vectors at three successive times before I use Gibbs' method?

I would like to try out Gibbs' method of preliminary orbit determination, which requires that from observations of a space object at the three successive times $t_1$, $t_2$ and $t_3$ (\$t_1 < t_2 &...
1k views

### Propellantless propulsion in gravity field

I have a proposal for a following propellantless maneuver. It is propellantless in sense that no mass is lost from spacecraft. It is not reactionless as spacecraft interacts with planet through ...
572 views

### Mean to Osculating conversion for non-J2 averaged elements

What is the appropriate technique to convert mean elements (true anomaly averaged) into osculating elements when the model has J2, SRP, drag and additional forces modeled. Brouwer's transformation is ...
1 vote
135 views

### Distance between a satellite and an orbit

I would like to compute the distance between a satellite and a specified orbit. For instance, for an orbit at 897 km altitude, 0 degree eccentricity, 99 degree inclination, and RAAN of 0 degrees on ...
182 views

### What use (if any) does the "empty focus" of an elliptical orbit have in orbital mechanics?

The 2 bodies in a 2-body system orbit around their common barycenter, which is located at the common primary focus of both their orbits. The empty foci don't seem to have a job in celestial mechanics. ...
2k views

### Re-entry Dynamics

I've been reading around a lot and I haven't been able to find any clear explanations. Maybe I'm a bit confused or maybe I am just looking in the wrong places. My question is, what are some basic ...
1 vote
132 views

### Center of gravity changes against the vertical axis of the orbital plane: Help me open some minds with the math on the behavior of objects in orbit [closed]

Edit: Ok, thank you all for your input. I will attempt to clarify the question now based on the additional information I was able to garner from your comments. I believe the math formula I am looking ...
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### Can Tisserand's parameter be modified to correct for perturbing eccentricity?

Tisserand's parameter is an "almost" conserved quantity in the CR3BP, even after flybys (useful for identifying asteroids). $$T_P = \dfrac{a_p}{a}+2\sqrt{\dfrac{a}{a_p}(1-e^2)}\cos(i)$$ It ...