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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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How to calculate the complete true anomaly motion in an elliptical orbit?

The true anomaly motion as I understand, is not constant in an elliptical orbit. The rate of change of true anomaly is not constant as in the case of circular orbits, in which case the true anomaly is ...
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Would a Hohmann transfer within LEO be useful?

Hohmann transfer is often used between a lower LEO orbit and MEO, GTO, GEO or beyond. But if the target is a high altitude within LEO, how would a direct ascent compare to ascent to a lower orbit ...
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Do horseshoe orbits have anything to do with Lagrange points? Do words fail us here?

I said (2010 SO16 is associated with Lagrange point L3 but wanders so far behind and ahead of it that the orbit is called "horseshoe"... and the comment was made: Not really. L3 is unstable. ...
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What are the conditions for re-entry of an object in a (highly) elliptical orbit?

There's something I don't understand: When it comes to de-commissioned satellites, rocket bodies etc. I thought one way of re-entry was via a highly elliptical orbit: The perigee gets low enough (app....
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Ordering of the Lagrange points

Is there any basis for the ordering of the L-points? Specifically, is there any particular reason for choosing L1 as the first L-point?
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Astrophysics on “The Martian”

In the movie the martian what was the purpose of the hermes crew in blasting a part of the ship? Was that explosion on the front or back of the ship? After the explosion what happened to the speed ...
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How fast can an orbit exist in the solar system?

How fast is too fast to stay in orbit around any particular large body in the solar system?
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How to calculate angle in elliptic orbit?

I would like calculate angle in elliptic orbit ZCP at any time, where: Z (position of periapsis), C (center of ellipse), P (current position of planet). I find topic, where is picture (in accepted ...
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Orbit, circularizing, apogee/perigee

First - my question: After the orbit insertion, in the coast stage, and assuming perigee is out of the atmosphere, and neglecting any external forces and influences - is the orbit now "fixed"? As in, ...
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If we can reduce travel time to Mars below the Hohmann standard, would we still use the same launch window?

If we can reduce the travel time to Mars below the Hohmann transfer orbit's typical 258 days, would we still use the usual Hohmann launch window or delay launch accordingly? For example, if we ...
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528 views

Cyclers To Mercury?

Is it possible to establish a practical 'cycler' transportation system between Earth and Mercury? The concept involves a small, manned payload (7.5 mt or less) doing the Earth departure and Mercury ...
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What is the order of magnitude forces due to Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare?

What in order of magnitude does pressures vary in LEO due to diamagnetic repulsion of Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare on an ideal satellite? Is there any ...
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Speed needed for the ship to escape Mars, on The Martian movie

Based on the two speeds and altitudes that are presented in the movie: "The Martian" which are respectively 741 m / s and 1350m, 850 m / s and 1843 m I would like to prove with calculations whether or ...
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How could transfers between SEL1&2 and EML Lagrange points be utilized?

The Earth has 7 Lagrange points nearby since SEL1 and SEL2 (Sun-Earth Lagrange points 1 and 2, respectively) are only between 3 and 5 LD (lunar distances) away from the five EML (Earth-Moon Lagrange) ...
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Launch profile autopilot

I'm new here, and I am delighted this forum exists! I'm working on a spaceflight simulator (FSX SpacePort) and currently, developing automated guidance module (I guess, a space autopilot). The ...
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How far will the debris cloud from Hayabusa-2's touch-and-go sample recovery travel around Ryugu? Will any have escaped to heliocentric orbit?

HAYABUSA2 MOMENT OF TOUCHDOWN This animation, extracted from a longer video, shows the moment of Hayabusa2's 21 February 2019 touchdown on asteroid Ryugu. JAXA Source: Planetary Society's Watch ...
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How do orbital spacecraft calculate reentry?

For a given spacecraft, in a given LEO orbit, assuming you have all the required data, how do you choose the needed burnout speed and timing (or position in orbit), in order to reach a certain point ...
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Why does Starman/Roadster have radial acceleration?

Discussion in chat pointed out that the SpaceX Roadster or Starman has a Marsden A1 coefficient. From solution 10 in Horizons: ...
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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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How do you determine the orbit of a satellite around some planet of unknown mass?

I am working on project where I want to derive the orbital equation for a satellite of Mass M, orbiting around a planet of Mass P. I want to do this with these unknowns first to then apply the orbital ...
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Walking in a rotating spacecraft and Newton's 3rd Law of Motion

I am wondering how Newton's 3rd Law of Motion would apply in the case of a man walking the length of a rotating spacecraft. Please reference the drawing below. Say that there was a spacecraft ...
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Diamagnetic Polar Orbit

This has nothing to do with electricity, Electrodynamic propulsion, or light sails. I am asking can a flat surface made of diamagnetic material like light sail displace Earth or the Sun's magnetic ...
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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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Orbit class or library or functions [closed]

I am (like a hundred other people, like a thousand other people) trying to make a space flight simulator. I'm not a student. (That said, I found Orbit – space flight sim. It’s excellent.* You ...
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Why don't SpaceIL's Beresheet spacecraft and Moon orbits line up?

The question Tracking SpaceIL Beresheet Moon lander links to some data files that are from the site: http://live.spaceil.com Raw data: http://live.spaceil.com/data/data_s1.txt (22/2 - 12/4) ...
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Mechanics of Sun-Synchronous Orbit & North Korea's KMS-4

QUICK QUESTION: Is North Korea's KMS-4 in a proper Sun-synchronous orbit? https://www.n2yo.com/?s=41332 2016-009A FOLLOW-UP QUESTION: How do I tell? I want to understand the mechanics. RESEARCH:...
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How SpaceIL Beresheet gets to Moon from GTO?

GTO is an orbit which has its main axis in the plane of Earth's equator. Moon orbit has a different plane. This means until GTO main axis isn't on the intersection of equator and Moon orbit, you can't ...
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Time to fall into the Sun from Mars orbit

If a body starts to fall freely from Mars orbit towards the Sun, then how can we calculate the time to touch the Sun' surface? I have tried the third equation of motion that says R=(1/2 dg)*dt^2. ...
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Stabilization of Lagrange point asteroids

There are a couple discovered asteroids that orbit around L4 or L5 Sun-Earth Lagrange points https://en.wikipedia.org/wiki/(419624)_2010_SO16 https://en.wikipedia.org/wiki/2010_TK7 From what I read ...
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A spacecraft leaves Earth exactly with escape velocity V2 - what trajectory it will have in Solar System?

A textbook solution: if a spacecraft leaves the isolated Earth with escape velocity V2 (=11.2 km/s at Earth's surface) it will have parabolic escape trajectory. But Earth is in orbit around Sun. The ...
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Launching east from a mountain on the equator at midnight during a new moon; ranking of each contribution?

This answer is intriguing and I'm curious if it's correct, and especially which effects are most important. If you want to avoid gravity assists, the most fuel-efficient way out of the Solar System ...
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Why were the Sputniks launched to such high apogee?

Sputnik I was launched to reach as high as 939 km above the sea level and made 1440 orbits. Vostok I with Gagarin aboard was launched to 327 km for one orbit. Wouldn't 200 km or even less be enough to ...
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Cheapest rocket to go to space?

Have you ever heard of the old movie Salvage? The TV movie, “Salvage,” aired on January 20, 1979. The film begins with Harry successfully bidding for a vintage bi-plane and then reselling it in pieces ...
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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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Is there a simple relation between delta-v and travel time?

For example, if it takes a delta-v of 4 km/s to fly from LEO to Mars in 8 months, according to one mission plan, would it take half the time, 4 months, if the delta-v was doubled to 8 km/s? Is there ...
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Why does in-flight mission abort often ends in ballistic high-g reentry?

I am seeing a lot of references to the “ballistic reentry” mode of the crew return vehicle in relation to the abort during the powered ascent stage. In partiulat, the recent crewed Soyuz MS-10 abort ...
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True Anomaly of Circular Orbit

How would you calculate the true anomaly of a circular orbit (e=0)? I'm trying to design an orbit for a mission on STK and so I'm not sure what the eccentric anomaly (in order to calculate true ...
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Why is momentum transferred to the moon?

The moon whizzes around the Earth, dragging water after it and producing tides. In a comment on this question, I asserted this would sap the momentum of the moon causing it to fall to Earth. This was ...
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Orbital mechanics: trying to understand counterintuitive behavior (braking to overtake)

If one spacecraft wants to overtake another (e.g. for a rendezvous), it has to (counterintuitively) brake, go into a lower orbit and use the higher angular velocity of that orbit/shorter orbital ...
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How did the Apollo guidance computer handle the Earth-Moon system's rotation around the Sun?

In this comment I just wrote: "...but at all other times it is just doing math to calculate its trajectory." The math needed a stable clock Timing accuracy of the Apollo Guidance Computer? (also 2, ...
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Compute heliocentric ecliptic coordinates from Kepler's laws

I'm writing a program to compute the heliocentric ecliptic position of planets and asteroids. I want to output rectangular coordinates oriented according to the ecliptic: positive X in the direction ...
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Apollo Missions - Travel time to moon [duplicate]

I must be missing something - escape velocity is about 25,000mph. The distance to the moon about 240,000 miles. That computes to about a 9 hour flight. Why did it take 3 days for Apollo missions to ...
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Why is Angular Momentum of Satellite Rotating in ECI Frame?

Summary: The angular momentum per unit mass of satellite is rotating in ECI x-y plane and I can't understand why. I'm very new to orbital mechanics. What I'm doing: I'm taking the cross product of ...
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How might one approach using AI (convolutional neural network) to predict collisions in orbit?

CNN's Tomorrow's Hero profile Meet Amber Yang. She's trying to prevent a space debris catastrophe describes an investigation into the use of a convolutional neural network (CNN) to predict possible ...
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How to construct $B^*$ drag term in TLE?

Is it possible to calculate $B^*$ term in TLE data using only a few or more velocity and position vectors for a satellite?
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Delta-V chart mathematics

Could someone explain me the mathematics behind the Delta-V charts one can find on internet such as:                 &...
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What are the practical uses of a state transition matrix?

I am studying different dynamical models of relative motion of satellites. In my work, I've always just used a numerical integrator like RK78 to integrate the cartesian system of equations: $\dot{r}=...
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How to calculate the kilowatt hours (kW-h) needed for a solar-electric engine to produce a given delta-v?

A spacecraft is in LEO and I would like to reach a certain point in space; let's say Mars. If I look at the diagram in this answer I see that the delta-v from low Earth orbit to low Mars orbit is ...
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Ratio of low-thrust slow spiral to Hohmann transfer $\Delta V$?

Going from one circular orbit to another, there are tables out there and equations that give the total $\Delta V$ needed for a two or three impulse maneuver scenario. For a very low thrust propulsion ...
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Did the astronauts of Gemini 4 have any realistic rendezvous simulator training of orbital mechanic effects?

Gemini 4 was launched on June 3, 1965. It mission included the first attempt of a rendezvous manoeuvrer in space. The rendezvous test failed. Two years earlier, in June 1963, the Rendezvous Docking ...