# 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].

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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}=... 1answer 1k views ### Thrust and rotation strategy to circularize a standard GTO orbit using ion propulsion? The previous question How much time does it take to circularize a GTO orbit using ion propulsion? has a good, quantitative answer based on a known delta-v. But I'm wondering how would you actually ... 2answers 246 views ### Is “medihelion” a word? "Medihelion" is what I call the two points on a solar elliptical orbit where distance from the sun is the same as the ellipse's semi-major axis. These two points also correspond to the end-points of ... 1answer 1k views ### How much “wobble” does a typical geostationary satellite experience? Recall that geostationary satellites are placed into an orbit which is designed to stay above a fixed point on the Earth's surface. If the Earth and the satellite were both spherical cows in an ... 1answer 691 views ### Ephemeris data usage in interplanetary trajectory application I'm trying to write a Mathematica application that allows users to choose their date of departure and time-of-flight for an interplanetary transfer mission (currently only working for Earth-Mars ... 1answer 836 views ### No need for gravity assist with Falcon Heavy? Elon Musk is quoted to have said, after the launch of Falcon Heavy, that «it can launch things direct to Pluto or beyond, no stop needed, don’t even need gravity assist or anything». Now, I am not an ... 3answers 284 views ### How “locked” are Pluto and Charon? How much does each librate as seen from the other? Discussion below Are all or some geostationary satellites tidally locked to the Earth? got me thinking about Pluto and Charon. According to Wikipedia: Charon and Pluto orbit each other every 6.387 ... 1answer 1k views ### Is a lunar Sun-synchronous orbit possible at the “frozen” inclination of 86°? I have been considering if it would be possible to place a satellite in a Sun-synchronous orbit in one of the lunar frozen orbits at 86°. According to NASA scientists there are four inclinations for ... 1answer 5k 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 ... 1answer 533 views ### 3-Body Simulation and Accuracy of Lambert Interplanetary Solver I've found that using a Lambert solver together with the equations of the patched conic approximation for an interplanetary flight from Earth to Mars is quite inaccurate, when taking Earth's ... 5answers 4k views ### Why does launching east result in an orbital inclination equal to the latitude of the launch site? As mentioned briefly in this answer and this Everyday Astronaut video: And just as a reference, if you launched straight east out of Kennedy Space Center, you'd be on a 28.6° inclination which you ... 3answers 2k views ### Teleporting an object into geosynchronous orbit Assuming that a method was found to teleport objects, and at huge range, if an object was teleported from the surface to a location at the correct height (Wikipedia says about 42,164 km from the earth'... 5answers 6k views ### What is the smallest body that has sufficient gravity for another body to orbit it? In the question Will Rosetta have to adjust its orbit around Chury due to the comet's coma and tails? and related answers it is implied that the Rosetta spacecraft will actually orbit 67P/... 6answers 679 views ### How was Juno's arrival set up to be on the evening of July 4th? Presumable it is largely a coincidence that Juno arrives at the perfect moment for American pride in NASA's achievements, but not entirely. The video below of the trajectory, released in July 2011 ... 3answers 3k views ### If a rocket launched due East from a high latitude, what happens to its path? Let's say a rocket launches from Iceland at 65oN headed for LEO, but instead of using an inclination that works from that latitude, it heads due East. It attains orbital altitude and acceleration, and ... 3answers 5k views ### How long will a 500 km altitude satellite spend in Earth - shade per orbit I used to know how to do this, but for the life of me I can't remember the source of the equations. This is clearly a question of geometry rather that any specific space science however I still feel ... 2answers 3k views ### Why do malfunctioning satellites come back to Earth? In school, I learned that if a satellite moves at a speed$\sqrt{gR}$(the square root of the product of the acceleration due to gravity and radius of the Earth), then it will remain in Earth's orbit. ... 2answers 2k views ### Can a satellite orbit the ISS? Is stable orbit of a small satellite around the ISS theoratically possible with minimal station keeping? 2answers 971 views ### Aborting a de-orbit maneuver I was contemplating on how a de-orbit may be abandoned post completion of the orbit burn, say, from LEO. A situation in which this might be necessary would be detecting a breach in the heat shield ... 2answers 6k views ### What would happen if I throw a grenade in space? What would happen if I throw a grenade in space? Would it explode? Or will it just keep floating forever? 1answer 337 views ### Many moons in same orbit Is it possible to have a stable orbit comprised of many moons(>2) that keep themselves roughly equal distance apart? Sort of like Epimetheus and Janus around Saturn but comprised of many moons. The ... 6answers 1k views ### Is it theoretically possible to dispose of the larger pieces of space junk into the Sun? Space junk is a real threat to working satellites in the Earth's orbit. Is it theoretically possible to make this space junk escape from the Earth's gravity (by giving them some kinetic energy to ... 3answers 543 views ### Why are lunar orbits unstable? I've seen a few times now that objects in orbit around the moon tend to crash into it in relatively short time frames. The orbits tend to become more elliptical until they intersect the surface, is ... 4answers 829 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) 2answers 3k views ### What is the effect of gravity slingshots around Earth on Earth's rotation and orbit time, and is this effect worth considering? Several space probes have used gravitational slingshots around Earth as part of their mission plan to get to other places in our solar system. Some examples I could find quickly are Galileo, Messenger ... 2answers 179 views ### How much variation in orbit altitude is caused by gravitational variation, in LEO? Imagine a hypothetical spacecraft in LEO, at 200km. Ignore air resistance for a moment. It's actual height will vary, due to both gravitational anomalies and the shape of the Earth. Do we know ... 2answers 208 views ### Orbit stability This is my first question. I am a space enthusiast but I don't have a formal understanding of celestial mechanics, so I would like to ask how stable against perturbation an orbit is, given the ... 2answers 2k views ### Reasons for using a bi-elliptic transfer for Soyuz-ISS rendezvous According to the ESA movie Soyuz rendezvous and docking explained, Soyuz uses a bi-elliptic transfer to move from the phasing orbit to the ISS orbit. Why is this more complex transfer used instead of ... 1answer 5k views ### Geosynchronous orbits around other Solar System objects Earth's geostationary orbit has many human-made satellites which have helped vastly with communications and research. Aside from this artificial collection, are there any other objects orbiting a ... 2answers 685 views ### Falcon 9 maximum point-to-point landing range Has anyone here ever done enough back-of-the-envelope math to come up with a rough estimate of the maximum landing range of the F9 first stage? I'm talking unladen-swallow-quality math here -- trying ... 1answer 2k views ### Why are orbit raising maneuvers for Mangalyaan done in the early hours? I was reading this news article, and it was mentioned that orbit raising is done in early hours. In all the five orbit raising operations, they are raising them only during night. What could be the ... 1answer 953 views ### What happens to JWST after it runs out of propellant? JWST will be orbiting L2 which is unstable equilibrium thus will require propellant for station keeping. JWST will carry propellant for 5-10 years. What will happen once it runs out of propellant? ... 1answer 2k views ### Why was Kepler's orbit chosen to continue to drift away from Earth? The Kepler telescope was launched from Earth on March 7 2009 and placed in an independent orbit around the Sun, with a semimajor axis of 1.0132 AU, period of 372.53 days, and an eccentricity of 0.036 ... 1answer 9k views ### How does SGP4 work? For calculating orbital state vectors of satellites, SGP4 (simplified perturbations model) is often used in conjunction with two-line element sets to calculate future positions of orbiting objects. ... 2answers 851 views ### How (the heck) can 2014 MU69's orbit be know well enough for a close flyby by New Horizons? The object 2014 MU69 is much smaller and dimmer than Pluto. Even as New Horizons approaches, it will be much harder for its 8.2 inch aperture, cooled CCD long range imager LORRI to get a fix on it ... 2answers 1k views ### What are the practical limitations of gravitational assists? Is there any specific, practical reason why we couldn't have a probe swing by Saturn, Uranus, Jupiter multiple times, over and over, before getting hurled into interstellar space at insane speed, ... 1answer 249 views ### 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 ... 1answer 208 views ### 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 ... 3answers 978 views ### How is the minimal$\Delta v$transfer between non-coplanar orbits calculated? If the orbits are co-planar (lie in the same plane), the required minimal$\Delta v$is calculated by the well-known Hohmann transfers. But what is the case if they aren't co-planar? How many orbital ... 2answers 359 views ### What are the requirements for$ɣ\$ shape flyby?

Understanding Kepler's laws, a body with speed exceeding escape speed of a major body will move in a hyperbolic trajectory, entry and exit vector, a "less than ellipsis" curve. You don't get closed (...
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### At which point would two GSO/GEO satellites with similar orbital elements be closest to each other?

While I was answering another question on How closely spaced are satellites at GEO I came to realize I can't really word it with much conviction how two close proximity satellites in GEO/GSO orbits ...
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### Explanation of single-burn trajectories from Lunar surface to Earth surface

I learned of the fine book Soviet Robots in the Solar System from this excellent answer. One chapter in it describes how the Soviets had extreme mass limitations on their lunar sample return vehicle ...
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### How does the ISS Transit Finder website get the position of the ISS so accurately?

The recent Petapixel article How to Shoot the ISS Flying Across the Face of the Moon gives a lot of detailed, helpful advice for photographing transits of the ISS across the disk of the Moon. For ...
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### Oberth Effect for non-tangential acceleration

Due to the Oberth Effect, it is most efficient to accelerate a spacecraft along its orbit at or as close-as-possible-to periapsis, and decelerate within close proximity to apoapsis. But all ...
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### To what extent could a single Triton flyby slow down a direct Hohmann transfer to Neptune for NOI?

I can't seem to find any good sources online for this, all I get are documents on how Nice model was used to compute Neptune's gravity capture of Triton via a binary dissociation, possibly because of ...
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### How to calculate apoapsis of sub-orbital trajectory?

I have made a RK4 simulator for launching a cannonball from a tower. Which has the state variables: Position vector r Velocity vector v Mass of planet M To simplify it, working in only 2 dimensions (...
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### What force is bringing Cassini down into Saturn's atmosphere in another 145 days; drag, or…?

Headlines suggest (as do their articles) that as a gravitational result of Cassini's final flyby of Titan, it's fate is sealed and it's orbit is destined to take it into Saturn's atmosphere on ...
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### Why has the Earth's motion carried it out of view of Pioneer 11's antenna?

According to The Pioneer Missions, my emphasis, The Pioneer 11 Mission ended on 30 September 1995, when the last transmission from the spacecraft was received. There have been no communications ...