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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 ...
Djembo's user avatar
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7 votes
1 answer
155 views

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 ...
Danny's user avatar
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7 votes
2 answers
2k views

How high did Philae bounce?

The Philae lander bounced off 67P/C-G due to low gravity, but how high did it actually bounce?
Mar's user avatar
  • 73
6 votes
1 answer
191 views

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 ...
c roald's user avatar
  • 161
4 votes
1 answer
179 views

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 ...
Woody's user avatar
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-3 votes
1 answer
118 views

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 ...
Luke Matthews's user avatar
18 votes
1 answer
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 ...
CapIsland's user avatar
  • 199
3 votes
2 answers
524 views

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 ...
DuckyPolice alt's user avatar
0 votes
1 answer
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
Zach's user avatar
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3 votes
3 answers
1k views

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 ...
Dan East's user avatar
3 votes
1 answer
154 views

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.
Mike Tuggle's user avatar
3 votes
2 answers
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.
LLLK7's user avatar
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2 votes
1 answer
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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) ...
truf's user avatar
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7 votes
1 answer
1k views

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 ...
The Rocket fan's user avatar
15 votes
2 answers
2k views

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 ...
Woody's user avatar
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3 votes
1 answer
416 views

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, ...
B2-B's user avatar
  • 31
2 votes
1 answer
502 views

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 ...
nigelg's user avatar
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1 vote
1 answer
232 views

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 ...
Electric-Basket's user avatar
3 votes
1 answer
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 ...
Andris Atteka's user avatar
1 vote
0 answers
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 ...
user avatar
3 votes
1 answer
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 ...
TheMatrix Equation-balance's user avatar
0 votes
2 answers
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 ...
TTomer's user avatar
  • 177
12 votes
1 answer
2k views

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 ...
Hale's user avatar
  • 231
1 vote
0 answers
44 views

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 ...
JM Yaden's user avatar
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1 vote
1 answer
223 views

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 ...
user48194's user avatar
6 votes
2 answers
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 ...
WhatIfEnjoyer568's user avatar
0 votes
1 answer
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 ...
KungFuNasi's user avatar
10 votes
3 answers
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 ...
Antti Rytsölä's user avatar
7 votes
5 answers
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 ...
Suddhasattwa Ghosh 's user avatar
3 votes
1 answer
247 views

To what percentage of the speed of light you need to accelerate to get artificial gravity at 1g?

Let's say you have a very powerful hypothetical fusion or matter/antimatter drive on a spaceship and you want to travel to a star nearby. Can you get 1g artificial gravity by accelerating? Or close to ...
jdiez's user avatar
  • 33
-1 votes
4 answers
920 views

How can I find the x, y position of apogee and perigee, if I only have the value of distance vector (position) and velocity vector?

I am currently working on a 2D space simulator where I have two bodies; one is still and other is an orbiting object, which I can also control like a rocket. I'm using the Newton's gravity: $F = \...
user325's user avatar
  • 29
6 votes
2 answers
255 views

What is the largest possible rocky body? [closed]

Suppose you start with a rocky sphere about 12,742 kilometers in diameter and continuously add more rocky material such that you don't smash this sphere to bits. What is the upper limit for this? ...
Frotz's user avatar
  • 161
6 votes
2 answers
956 views

How does gravity change beyond L2?

Why does gravity appear to increase again on the far side of L2 from earth as indicated on the gravitational contour diagram? One would expect gravity to continue to decrease as the distance from sun ...
Sunfish's user avatar
  • 61
3 votes
1 answer
505 views

When calculating the six Keplerian Orbital Parameters, why do we need both Eccentricity AND the Semi-Major Axis? Doesn't one tell you the other?

Perhaps I am misunderstanding elementary math, but.... How is it possible to know the eccentricity of an ellipse (e) but not the semimajor axis (a)?
Kurt Hikes's user avatar
7 votes
1 answer
1k views

Why does the eccentricity vector always point towards the periapsis of an orbit?

I hope you know that eccentricity can be derived from the position and velocity vectors of a spacecraft (only applies to a two body problem) through this formula : $$\textbf{e} = \frac{\dot{\textbf{r}}...
John's user avatar
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0 votes
0 answers
64 views

Since we humans are't able to process any dimensions like 4D and 5D, the distance between stars and galexies appers to be too far away [duplicate]

For exmaple a living oraganism of 2D world is unable to perseive a 3D world. Similary, do humans have such limitations to perseive the further dimensions that 3D, that could results in wrong ...
jidh's user avatar
  • 27
8 votes
3 answers
1k views

Differences between numerical propagators

I am a trainee who is working on a numeric orbital propagator developed in the company. I can't show you the code but I can tell you that the propagator was developed to work in Simulink. My job was ...
Frank's user avatar
  • 315
3 votes
2 answers
182 views

Can "prolateness" be characterized by a $J_2$ coefficient like "oblateness"?

When an imperfect sphere can be obtained by rotating an ellipse around an axis, it is called a spheroid. There are two types of spheroids, oblate ones and prolate ones. Most solar bodies can be ...
Ng Ph's user avatar
  • 2,734
6 votes
3 answers
364 views

Could you survive very high G's if your whole body was accelerated uniformly?

Could you survive high g's if your whole body was accelerated uniformly (not just by the seat of a rocket pushing on your back)? Your body is really only affected by gravity if you are touching ...
bacon gaming's user avatar
4 votes
0 answers
39 views

Can Interferometery be Used to Shorten the Solar Gravitational Lens Focal

The solar gravitational lens's focal is around 550 AU which is very far. Can we send a few telescopes that will stop midway (let's assume 150 AU) to collect the light and work as interferometry?
Mohamed Abduljawad's user avatar
7 votes
1 answer
250 views

Is 1/6 G enough for humans to stay healthy?

Micro-G is known to be detrimental to health in the long-term. However, the Moon is at $\frac{1}{6}$ G (while Mars is at ~$\frac{3}{8}$ G). Is $\frac{1}{6}$ G enough for humans to remain healthy in ...
DJG's user avatar
  • 804
26 votes
3 answers
6k views

What is the "mass" of a Lagrange point?

Of the five Lagrange points, L4 and L5, as stable points, can be orbited by asteroids, satellites, and any other useful or interesting object. Assuming two-body motion however, calculating orbits with ...
TheEnvironmentalist's user avatar
1 vote
2 answers
337 views

Energy to "nudge" a planet to a smaller orbit

Suppose we wanted to move a mass-$m$ planet to a much smaller new orbit around our mass-$M$ Sun. We'll assume the initial and final orbits are circles of radii $r_i,\,r_f$ with $r_f\ll r_i$, so GPE is ...
J.G.'s user avatar
  • 275
1 vote
2 answers
326 views

Would an increase of a planet's mass affect its trajectory?

If humans happened to colonize Mars some time in the future and increase its mass such that its gravity increases from 3.721 m/s2 to 9.8 m/s2, would it not fall into the Sun?
magamanmagama's user avatar
8 votes
2 answers
1k views

Is the weightlessness in a swimming pool the same as in outer space? [duplicate]

Astronauts practice the weightlessness of space in a swimming pool. Is this weightlessness the same as in space? Lets ignore the friction with water imagine them to be suspended in liquid helium...). ...
Deschele Schilder's user avatar
18 votes
7 answers
9k views

Is the zero gravity experienced in ISS the "artificial" kind?

I always wondered about the following: An astronaut floating inside a spaceship that is far from Earth or any other other planet will experience true zero gravity because there is negligible ...
Sprout Coder's user avatar
12 votes
3 answers
6k views

Does Virgin Galactic experience real weightlessness?

Does Virgin Galatic go into space high enough to experience real weightlessness? A CNBC article states it's more microgravity centrifugal: The spacecraft essentially does a slow back flip at the edge ...
mattsmith5's user avatar
2 votes
0 answers
74 views

What does "1g ref" mean in the ISS Crew Notebook?

Earlier I happened across What's the small white gadget with two black buttons in this video of the International Space Station? via the HNQ list. I was intrigued by the snippet from the "...
Vicky's user avatar
  • 121
6 votes
2 answers
853 views

What is a gravity gradient?

The statement: 'For most of that day, Mir remained in a "gravity gradient," (sic) which basically means that the most massive part of Mir naturally pointed toward Earth.' is in https://...
Matthew Christopher Bartsh's user avatar
1 vote
0 answers
98 views

Gravitational potential [closed]

I understand how we calculate gravitational potential and how we set it to be zero at infinity, and I understand its value at he Earth's surface is $-64\,\mathrm{MJ/kg}$ by using $r$ as Earth's radius....
James Oconnell's user avatar

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