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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.

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What is this perturbation effect called, and what would be an analytical expression for the resulting eccentricity oscillations?

In this answer I've generated some oscillations of eccentricity by being somewhat naughty and propagating a TLE for +/-250 days from epoch. I believe it's okay for the purposes of demonstrating gross ...
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Can objects be deorbited by a satellite using a magnetic field?

Can a magnetic field be made around a satellite for a split second to gain or loose momentum from another satellite or debris with a few passes with a near-miss trajectories on larger debris? Could a ...
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Differences between SGP8 and the standard SGP4? Is it ever used in practice?

The Wikipedia article Two Line Element Set says: The SGP4 model was later extended with corrections for deep space objects, creating SDP4, which used the same TLE input data. Over the years a ...
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How much delta-v would Hayabusa-2 need per day to remain 20 km sunward of Ryugu?

Hayabusa-2 is near the astroid Ryugu, and both are essentially in nearly-matching heliocentric orbits around the Sun. Hayabusa-2's "hangout" is about 20 km sunward of Ryugu. For the purposes of this ...
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Does the International Space Station get TV?

For obvious reasons the ISS cannot get cable TV. Can the ISS get the new digital air TV or satellite TV using an issued dish and receiver like a house? How would that be done compared to how it is ...
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270 views

Hyperbolic orbit: correct?

I'm writing a sci-fi story. The protagonist wants to strap rockets to an asteroid and send it rocketing to earth, into orbit, to harvest the metals, etc. An acquaintance (i lost contact with him but ...
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What exactly means universal variable x and z?

I have been studying by myself Orbital Mechanics, and when solving the Lambert Problem, it's common to use the universal variable approach. I understand the algorithm, but I haven't found any book ...
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Best heading for Hohmann transfer in real life

Assuming one wants to go from a 400x800 to a 1000x1000 orbit. The solution that require the least D/v is a Hohmann transfer, with one burn at the perigee and one burn at the new apogee (or vice versa)...
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Nature of Hayabusa-2's “Home Position” relative to Ryugu? Is it Ruygu's L1?

This tweet "from Hayabusa-2" via JAXA shows the diagram below, which seems to suggest that the Hayabusa-2 spacecraft tends to remain between the asteroid Ryugu and the Sun. Does Hayabusa-2 have to ...
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Can a satellite utilize gravity gradient stabilization, solar power, electrodynamic tethering and dynamic quadrupole momentum at once?

Have any analysis been done using 2 or more devises above to function as a satellite where 1 alone would not to maintain orbit without propellants? Will this system or one with a different ...
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Simplified WGS84 or EGM2008 model for rapid computations?

I am searching for a simplified model of EGM2008 that can be used for rapid, repetitive computations. It needs to be valid only up to GPS altitudes. I'm thinking such a model already exists but cannot ...
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How are co-located satellites positioned relative to each other?

I'm trying to learn about co-located GEO satellites. When I first heard about them, coming from a planetary orbital mechanics background, the first thing I pictured was based on the epicyclic ...
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1answer
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What would the perihelion of Ulysses's orbit have been without a trajectory adjustment after its Jupiter swingby?

I'm wondering what the perihelion of the orbit of Ulysses spacecraft would have been had a trajectory adjustment after its Jupiter swingby not taken place? On Wikipedia it says "The size and shape of ...
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1answer
122 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 ...
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1answer
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Do Lagrangian points apply to eccentric orbits or binary systems?

The assumptions about the Lagrangian points being stable (...in the traditional meaning of the word: not moving around; they are unstable in the mathematical sense, except for arguably L4, L5) that I'...
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How is the Chebyshev method used by JPL?

In the DE packages, NASA gives us a series of coefficients for the Chebyshev approximation. As I understand it, those approximations are given by a series of polynomials $T_n$ for the interval $[-1,1]$...
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How to get from the perturbative acceleration formula to the acceleration on the 3 axis in the case of the oblate Earth, considering j2?

If we start from the pertrubative acceleration formula, how do we get the expression for the acceleration for the 3 axis written under that form. I've used the partial derivative for the gradient ...
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1answer
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When Wikipedia gives the semimajor axis of the Moon's orbit, which distance does this represent?

The masses of the Earth and Moon are in a ratio of about 81:1, so they can be thought of as orbiting around their common barycenter which is inside the Earth, but about 2/3 of the way to the surface. ...
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How could an object barely exceeding escape velocity from the Moon eventually reach the Earth?

Since NASA is once again targetting low-cost missions to the Moon, I was thinking about low-cost methods of getting stuff from the Moon back to Earth. Although it seems reasonable to assume that ...
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How was the radius of Venus measured so accurately (± 3 km) in the mid 1960's, before Venera 4 and Mariner 5?

In several answers to the question When did planetary scientists realize Venus' surface pressure was almost 100x that on Earth? How did they find out? the known radius of Venus is mentioned. It was ...
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What's the planetary exploration word for “impact parameter” (distance of closest approach if gravity were “turned off”)?

In particle scattering there's a term called "impact parameter", which is the minimum distance a particle would pass a second particle at rest, if the attractive or repulsive force were ignored or "...
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Piggybacking to Enceladus

The latest NASA New Frontiers selection did not select any finalist proposals to Enceladus, which is one of the most promising targets for life in the solar system. It did however select Dragonfly, ...
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Is the Parker Solar Probe's semimajor axis being so close to that of Mercury's just coincidence? Does it help somehow?

Parker Solar Probe will end up in it's Sun-kissing orbit though a series of Venus flyby's, which roughly pins Parker's aphelion at Venus's semimajor axis or about 108 million km. Its final perihelion ...
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Diamagnetic Orbit

This has nothing to do with electricity or Electrodynamic propulsion. I am asking can a flat surface of diamegetic material be made into a sail similar to a solar sail to displace and repel through ...
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What is the optimal angle for a solar-sail deorbit towards the Sun when radial thrust is included?

In this answer there's a geometrical derivation of the optimal angle of a solar sail to deorbit a spacecraft into the Sun. The naive answer is 45° which would direct the reflected light directly ...
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Would a lower LEO ISS orbit really have a shorter eclipse duration than a higher one?

This comment says Lower orbit also mean shorter ones; for observations (one of the ISS missions) it is an advantage. It also have shorter night times (ie smaller batteries).. and the likely ...
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Geosynchronous Planetary Ring Challenge

A challenge for those of you with some math skills. we know the elevation and speed required to put a satellite into a geosynchronous orbit(or geostationary if you prefer), and that any further out we ...
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What is the importance of thrust control history in low-thrust optimization?

As I have mentioned before, I am trying to optimize an Earth - Mars low-thrust transfer using a particular method. It has been mentioned to me, and I have seen it in many papers, that thrust history ...
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2answers
133 views

What is the functional form for r(t) for a solar-sail deorbit into the Sun?

This answer describes a spacecraft in a heliocentric orbit using a solar sail to "deorbit" into the Sun by reflecting sunlight into roughly the prograde direction. In comments it was proposed that ...
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1answer
577 views

Is it possible to reach the Sun without expending any fuel/reaction mass?

Imagine that I'm designing a space probe, that will initially be placed into an Earth-like orbit around the Sun. My goal is to have the probe fly/fall into the Sun; it's allowed to take as much time ...
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Aerobraking on Mars

I am looking for a calculator or formulas that can be used to calculate the aerobraking on Mars mission. I have found some data on previous Mars flights where aerobraking was used and all my current ...
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1answer
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Angular momentum in non inertial frame [closed]

How to express the angular momentum in non inertial Earth frame like Earth Fixed frame so that angular momentum is conserved ? Is H = R x mV still valid when R and V are taken in the rotating frame ?
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Transformation between ICRF and Fixed in STK

I am building a satellite orbit propagator in MATLAB and I am using STK as a reference. Comparing TwoBody propagator using RKN78 (MATLAB) with HPOP (degree 1, order 1), I am getting quite good ...
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How much goes Phobos in the direction of Mars with a constant force in that direction? [duplicate]

Edit: Although this question may look similar to this one, here I am asking about a constant force in the direction of Mars, and no one of the answers there have answered this question. Because ...
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1answer
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What is the eccentricity of a near equatorial LEO?

I am trying to do some calculation on the 2-body problem but I am stuck as I need either the eccentricity or the periapsis of the orbit. I already have the orbital period which I assume as ~127 min as ...
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Can Lissajous orbits have stable/unstable manifolds?

The question Did DSCOVR travel “along the stable manifold of it's future SE L1 Halo orbit” to get there? is specific to DSCOVR's trajectory from Earth to its primarily heliocentric orbit near Sun-...
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1answer
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Low arrival V-infinity?

So I am modelling an Earth - Mars low thrust trajectory in a simple manner. I'm telling my model to not model any trajectories where the spacecraft is moving any more than 200 m/s quicker or slower ...
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How will the Lunar Gateway go to L2 and L1?

In a talk to the press which can be heard in the YouTube video NASA Administrator Jim Bridenstine Explains the Lunar Gateway, NASA director Jim Bridenstine says after about ...
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1answer
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How to determine an orbit of a satellite for a collision detection?

I'm trying to validate an collision detector , and for that I'm starting from a pair of initial conditions for a satellite.After that I will use an RK method to integrate . How can I determine a pair ...
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649 views

How is a Russian satellite's behavior “very abnormal”?

The BBC has a news article saying: "Mystery Russian satellite's behaviour raises alarm in US". But the article doesn't say how or why the behavior is "abnormal". And the linked transcript of Remarks ...
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1answer
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Relativistic effect on satellite motion

I am using GMAT to propagate satellite motion. At first, I excluded all the propagators besides harmonics(of second degree and 0th order, as shown in the picture): Here are the results(...
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2answers
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What is the timespan for a block of Phobos to reach a low orbit around Mars with a solar sail?

Edit: Although this question has been marked as a duplicate of this one about solar sail thrust calculation, they are different because I ask about a solar sail that has an orbital trajectory and ...
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2answers
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Onboard propagator in satellites SGP or J2

The Earth orbit propagator SGP4 (simplified general perturbation) was developed by NORAD to allow users to generate short-term prediction of satellite positions using two line element sets (TLEs) ...
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1answer
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Apollo 10: Where's Snoopy?

During the Apollo program, we launched a total of 9 Lunar Modules (LM's). The Ascent module from Apollo 10, or "Snoopy," is unique in that it was neither deliberately crashed into the Moon (Apollo 11, ...
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1answer
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Algorithmic methods or techniques to find conjunctions in high N Keplerian element ensembles?

Suppose I wanted to answer the question Will Starman/Roadster pass particularly close to any asteroids in the next few years? or try to predict satellite conjunctions around Earth (e.g. Celestrak's ...
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How to specify constraints for launch windows

I'm trying to learn trajectory design and optimization, and I'm struggling to understand how one determines the launch window using trajectory design programs. I know that my satellite's initial ...
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2answers
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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 ...
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1answer
129 views

JGM-3 vs EGM2008 coefficients

I've implemented the Earth harmonics calculation in JGM-3 model, using the coefficients from here ...
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What are “Ohms burns” in the context of Scott Kelly, KSP, and the Space Shuttle?

The Ars Technica video Astronaut Scott Kelly teaches orbital mechanics with Kerbal Space Program (also in YouTube) is a little bit humorous. When Scott Kelley is talking about orbit circularization ...
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How does the Parker Solar Probe have such a wide launch window?

The Parker Solar Probe is set to launch on August 11th 2018. It will perform 7 orbit-lowering gravity assists around Venus for ~6 years before reaching its final operational orbit. It has been well ...