# Questions tagged [gravity]

Questions regarding the attractive force present between two masses. If about research in artificial gravity (i.e. manmade substitutes for gravity), please use the artificial-gravity tag.

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### What is the order of magnitude of perturbing forces in a lunar orbit in relation to the orbital altitude?

Although there are many sources that compare the magnitude of perturbing forces in an Earth orbit (see for example the answer to this question), I haven't been able to find the same information for ...
• 11
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### How is the equation for non-spherical gravitational accelerations derived?

I am referencing Vallado (4th edition) to understand the acceleration contributions on a spacecraft due to non-spherical gravitational effects. Generally, I understand this derivation, except for how ...
• 215
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### How high did Philae bounce?

The Philae lander bounced off 67P/C-G due to low gravity, but how high did it actually bounce?
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### Are the Jupiter-Io Lagrange points stable?

Lagrange points are solutions to the three-body problem. Moving among Jupiter's Galilean moons seems likely to be at least a six-body problem, so there is no reason to assume the three-body solutions ...
• 161
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### How do Inertial Navigation Systems compensate for their inability to measure gravitational acceleration?

Inertial Navigation Systems calculate position by measuring acceleration. But they are unable to measure gravitational acceleration since gravity always acts equally on the test mass and the ...
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### Artifical Gravity central core [duplicate]

so have read about the centrifugal acceleration to create artificial gravity. Being mindful of the limitations of getting objects into space, the question is more curiosity. Is it possible to work ...
6k views

### Person falling from space

A person at rest 500 km above the Earth falls straight downwards. She has a snug magical force field around her that is totally rigid and completely protects her from outside heat. The force field ...
• 199
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### If a baby was born on the ISS, what would its nationality be?

If a baby was born on the ISS, what would its nationality be? Many countries grant citizenship to any baby born within their territory, but the ISS is not national territory ... or is it? If a ...
263 views

### What speed could you achieve by slingshotting around earth from moon?

Imagine Apollo 13 had fuel to burn engines on the way back to earth but instead used earths gravity to accelerate and the slingshot around earth
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### Would orbital ring platforms affect the orbit of a planet?

If we built an orbiting platform of sufficient mass (let's say, made from harvested asteroids) that was anchored at both poles of the planet it surrounded, would such an addition to the planet's mass ...
• 31
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### Can a ship's thrusters amplify a gravity assist?

If a ship successfully absorbs a planet's kinetic energy to increase its speed, can it add to that speed by firing its thrusters? Thank you very much.
266 views

### Do knots behave any differently in zero gravity?

What happens to knots in zero gravity? Do they behave any differently? I've tried to do some reading on it, but I can't find anything related to knots in zero gravity.
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### Reducing degree of ICGEM's Gravity Field Models for orbit propagation

I would like to use one of the static gravity field models published at ICGEM for satellite orbit propagation. For example, EGM2008. Its degree is 2190. I would like to use only 360 (may be even less) ...
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### 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 ...
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### How do the interferometers on the drag-free satellite LISA receive power without altering their geodesic trajectory?

LISA is a proposed space probe designed to measure gravitational waves. It aims to measure gravitational waves directly by using laser interferometry. It uses a drag-free satellite design to protect ...
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### Calculating and Drawing the orbit of a body in a 2D gravity simulation in python

I'm making a space exploration game and its in a 2d plane so no z axis, and I'm using Newton's law of universal gravity, I would really like to calculate anddraw the predicted trajectory of a body, ...
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### 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 ...
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1 vote
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### What will be the escape velocity for a human body?

Now imagine an average man of 70kg floating in space with no gravitational forces acting on him. Now a pebble(25 grams) spawns into existence near him. So now there's a gravitational force between ...
2k 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 ...
1 vote
82 views

### How would low gravity on Mars be a stress factor on plants?

As a 12 year old doing a science project for my local science fair I have found that many experiments that try to simulate how the environment would be like on Mars while growing plants always forget ...
1k views

### How to maintain balance and center of gravity when pushing a 100-ton piece of asteroid?

I understand that rotating momentum around a fixed axis can help with the center of balance. But is it enough? In my case, a space tug has to burn its engine for 1 min, accelerate a 100-ton piece of ...
94 views

### Is it possible to avoid tearing apart from a blackhole if moving fast enough?

I have a spacecraft zooming directly into a blackhole with constant thrust. Considering the gravitational force of that blackhole and that there is no terminal velocity to slow me down. According a ...
• 177
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### If Earth had a second moon, where would it be positioned? [closed]

Could Earth theoretically have another moon, beside the existing one, that would have a stable orbit? If it is possible, could Newtonian physics describe where it would be (i.e its position relative ...
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1 vote
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### Time a rocky satellite in lunar "frozen" orbit spends in Earth's umbra during total lunar eclipse

I am wondering how long a large satellite in a lunar frozen orbit would remain in the Earth's umbra during a total lunar eclipse. The satellite is spheroid with a diameter of 200 km. Let us say that ...
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1 vote
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### Gravity Calculation Inaccurate?

For the past week, I've been working on an Effective Gravitational Acceleration calculator on Desmos. This calculator ignores drag and assumes that a rocket is flying up completely straight. What this ...
386 views

### How much gravity do Humans need?

My question is how much gravity do Human Beings need to be reasonably healthy long-term? I am aware that the current answer to this question is "We don't know", but I wish to know if we have ...
128 views

### Spacewalk From Earth To Luna [closed]

A question that I have not seen but have been curious about…… I have a little bit above average (I think) of how gravity works or what gravity is but can’t figure this out; Let’s pretend that we make ...
5k views

### When staying indoors, can missing gravity be replaced with blowing air?

As I was watching Ad Astra (Great movie, but where does the gravity come from?), I had the idea that in a building or closed vehicle in a low gravity location, maybe air pressure could be used to ...
3k views

### Gravitational field of the Moon and Earth

Is there any method to find a point or plane in space where the gravitational field of the Moon and Earth are the same? And if so, what happens to a spacecraft if it passes through that point or ...