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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104
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12answers
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What are the choices today for orbital mechanics simulation software?

I used to be familiar with the various choices out there for orbital mechanics simulation software. Alas, those days are gone. What are the choices today, preferably sorted by platform? This ...
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What can the KSP game actually teach about spaceflight and orbital mechanics, and what are its limitations?

I have seen at least several different users mention that they've found Kerbal Space Program helpful to understand issues of spaceflight and orbital mechanics. According to Wikipedia: While the ...
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When was Newton “not good enough” for spaceflight; first use and first absolute requirement for relativistic corrections?

Concepts in Special Relativity (1905) and of General relativity (first developed between 1907 and 1915) substantially predated spaceflight; they were well known and had been tested well before objects ...
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Is it possible for a moon to have a higher surface gravity than the planet it is attached to?

Is it possible that a moon has a higher surface gravity than its planet? I guess it would mean that the moon has a higher mass, but then it would be the planet gravitating around the moon and the ...
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Game for teaching basics of orbital mechanics

I am looking for a game that would be suitable for teaching basic orbital mechanics concepts to primary school students (grades 6-8). Contrary to most of the questions here asking about spaceflight ...
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Can you tack against the sun using a solar sail?

Solar sails are a great, inexpensive way to move out from the sun, if you’re not in a hurry. Ocean going ships are able to tack against the wind, and to move up wind. Could a solar sail gain inbound (...
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Why did Saturn V not head straight to the moon?

This may seem a naive question, but as I understand it one of the reasons for the enormous energy expended by rockets is the extremely high speed (around 28,000kph) you need to achieve a stable orbit ...
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1answer
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How often does ISS require re-boosting to higher orbit?

I know that ISS, being in low Earth orbit, requires regular boosts. But I can't seem to find information on how often does this happen. Is it done during each resupply mission, only during some of ...
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Which is closer to Mars, Earth or the Moon?

Which is closer to Mars, Earth or the Moon? I'm writing a novel and I'm so grateful for the wealth of information. The only answers I find refer to Phobos and Demos Mars moons.
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How realistic is Kerbal Space Program?

Kerbal Space Program is an independent spaceflight simulation game, which has become quickly popular due to being (kind of) precise at simulating actual spaceflights. But how precisely? How close is ...
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Does a satellite naturally turn in phase with its orbit, always facing Earth?

Assume you want a satellite to constantly point its radio dish towards Earth while orbiting it, or its solar panels towards the Sun if it is instead orbiting it. Is any of the following true about ...
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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 ...
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Why should space probes have to orbit the Earth before being launched at other planets?

I'm curious to know why any satellites that need to be sent to other planets should be moving around the Earth rather than directly going towards their destination? Today, India launched one satellite ...
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The dreaded apocalyptic asteroid approaches Earth but lands safely on the Moon at zero relative velocity

An asteroid approaches and the Moon 'catches' it in the same way that a sports player catches a ball - that is to say by matching the velocity of the hand to that of the ball. Could a lucky slingshot ...
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Why should the James Webb Space telescope stay in the unstable L2?

We all know that James Webb Space telescope is planned to be launched in 2018. It has been decided that the orbit of JWST will be elliptical around the Lagrange point L2, which has been declared as ...
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Is there any reason why a spacecraft would not be able to turn around without a gravity assist?

Let's say you have a spaceship on its way to Mars; halfway there you decide you need to come back to Earth instead. Is there any reason a spacecraft would be unable to do this? Let's assume it began ...
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What uses would the Aldrin-Cycler have?

An Aldrin-Cycler is a vessel on an orbit on which it passes both Earth and Mars every few years without expending much fuel. At first glance this seems like a great thing for a permanent ...
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Why does this plot show Starman's speed relative to the Sun fluctuating so often?

After the launch of Starman, during the inaugural flight of SpaceX's heavy lift vehicle, the Falcon Heavy, PearsonArtPhoto set up a website to track various stats about Starman and his Roadster. A ...
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How to programmatically calculate orbital elements using position/velocity vectors?

I would like to build some orbital mechanical software from scratch. I feel that this would be a great way to learn the steps required to calculate different Kepler orbital elements of an object, plot ...
32
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3answers
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Could a partial space elevator be practical and useful?

Would it be technologically and economically practical to build and operate a space elevator that only provided transport between lower and higher orbital paths? Such a mechanism would only avoid ...
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How did the Lunar Module dock with the rest of Apollo 11 and what is the “CSM”?

I'd like to ask if anyone can, in layman's terms, describe the procedure by which the Apollo 11 astronauts were able to get back to their ship? I ask because the most accessible literature on this ...
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Why is delta-v the most useful quantity for planning space travel?

Many of the questions and answers on this site make use of the concept of delta-v. Is there an easy to understand the reason why delta-v, the magnitude of the change of the velocity, $|\mathbf{v}|$, ...
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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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Do any launches bypass LEO?

If sending a payload to GEO (geosynchronous orbit) or any other high orbit, you could start off launching to LEO (low Earth orbit), and then use a Hohmann transfer to raise the height of the orbit. I ...
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Is there a lot of space trash at the Earth-Moon Lagrange points?

Lagrange points are the points in a multi-body gravitational system in which the gravitational force and centrifugal force sum to zero. The image below from this Wikipedia article shows the 5 ...
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Orbiting Earth before heading to Moon

Each of the lunar Apollo missions (Apollo 8-17) entered Earth orbit immediately after launch. Each mission then left Earth after a few orbits by burning the S-IVB engine, and headed off to the Moon. (...
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Is the “airship to orbit” mission profile feasible?

By one of those weird coincidences, I had been on JP Aerospace's site mere hours before reading this question about space dirigibles here. Their mission plan seems too good to be true. They are ...
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How is the altitude of a satellite defined, given that the Earth is not spherical?

The altitude of a satellite is the distance between the Earth's surface and the satellite, but the Earth itself is not spherical. At the equator the Earth's radius is 21 km more than at the poles, and ...
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Determining orbital position at a future point in time

This might come of as a millionth-time award winner beginner question, but since I'm not familiar with either correct terms or designations, I'll put this question in my own language, since I'm not ...
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Why is the ribbon of decommissioned geosynchronous satellites skewed?

I was looking at this 3D map of satellites orbiting earth and noticed something interesting. Around the green ring of active geosynchronous satellites, there is a ribbon of what I assume are obsolete ...
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Could we wait for Mars to come to us?

This may be a stupid question but I didn't find much information online about it. The concept is simple, could we launch a vehicle into space from Earth, stop right on Mars trajectory and wait for the ...
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Why is geosynchronous orbit an altitude, rather than a velocity?

When people talk about geosynchronous orbit--an orbit in which the satellite continuously remains "directly overhead" for the same ground position on Earth--they talk about it being at a specific ...
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How many petaflops does it take to land on the moon? What does Artemis need with an Aitken?

All of the top five answers to The Martian: Does it really take a supercomputer to calculate spaceflight maneuvers? are essentially "no, orbital mechanics isn't rocket science". Okay I have used some ...
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How can I intuitively understand gravity assists?

For example: How should a spacecraft pass the Moon to reach escape velocity from Earth? How should it pass Venus for a slingshot towards Jupiter orbit? Conversely, to descend Venus to Mercury? Is ...
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Is it possible to have an orbit around the earth and the moon

I was just wondering if it were possible to A) Orbit the moon and earth B) To orbit any two celestial bodies really?
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2answers
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How long does a CubeSat last?

If I were to launch a CubeSat, how long would it last before falling out of orbit and burning up in the atmosphere?
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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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How large is the Earth's gravitational Sphere of Influence and how can it be calculated?

There was a recent update on ISRO's Mars Orbiter Mission's (MOM) Facebook page that it has crossed the Earth's Sphere of Influence (SOI): MOM moves on! MOM is going to cruise out of the sphere ...
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How complex was the math and physics necessary to place Apollo 11 on the moon?

Specifically, I'm interested in how closely the models used to calculate the various burns and course corrections represented reality. Was standard Newtonian mechanics sufficient or were relativistic ...
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When you shoot for the moon and miss, where do you end up?

The first American moon launches were in the ranger program. Ranger 3 and 5 both missed the moon in their 1962 attempts. Where are they now?
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Could the sun be used as a gravity assist outside the solar system (with current tech)?

I think I might have understood what this XKCD comic is trying to do. The diagram is proposing to use the Oberth effect at closest approach to the sun to escape the solar system! (image license: CC ...
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Why does InSight plan to launch from Vandenberg

Why does the InSight Mars lander mission intend to launch from Vandenberg, which does not allow for prograde launches? Will it launch into polar or retrograde orbit? Why? It will do an interplanetary ...
24
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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:                 &...
24
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1answer
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How many active or inactive artificial satellites are in Mars orbit?

I just read in the BBC news that four nations have placed satellites in Mars orbit. How many active or inactive artificial satellites are there in orbit around Mars (2014)?
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SpaceX's 4,425 satellite constellation - what's the method to the madness?

The BBC article SpaceX aims to launch internet from space discusses the SpaceX proposal for a dense array of over 4,000 LEO satellites for global internet coverage, and links to SpaceX non-...
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How are flight plans calculated?

When a project like Rosetta is being developed, how are flight plans calculated? Do planners simply input the desired target into a program or a flight computer which spits out the optimum flight path ...
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What is the feasibility of a rocket hobbyist achieving a LEO orbit with a microsat?

Along with being a rocket hobbyist, I'm also an Amateur Radio Operator. I would like to determine the possibility of placing a "microsat" a miniature packet radio satellite, into a low earth orbit.
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Why does the ISS track appear to be sinusoidal?

Okay, time for a stupid question, but it keeps me up at night trying to figure it out. The ISS 'route' appears on paper as such: I am imagining it has to do with a combination of its orbit and the ...
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How does a spacecraft know that it is in orbit?

After a 5 year long journey in space, Juno finally reached and started orbiting Jupiter. How does the probe actually know that it is in orbit, so that it can send confirmation message like 'Welcome to ...
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What are these orientations called in orbit?

Let's say a spacecraft is in an orbit like this one: If the red arrows point to prograde and retrograde, and the blue arrows point to normal and antinormal, what do the green arrows point to? In ...

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