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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9
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2answers
1k views

Did any spacecraft ever use the Sun's gravity for acceleration?

Space probes often use planets to accelerate onto a trajectory towards their goal(s) without having to consume too much fuel. But the fastest acceleration would be made through the Sun's gravity if ...
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3answers
4k views

Does lower gravity on Mars make it unsafe and unhealthy for humans?

I've been thinking about proposals to live on Mars. One idea is to create an artificial magnetic field to protect from solar radiation. Another idea is to warm the planet using solar mirrors. In the ...
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1answer
156 views

How low would gravity have to be for the balance system to fail?

This is a very critical question that is necessary to get answered for flights to distant celestial bodies. The inner ear liquid makes you perceive which way you're pulled onto a celestial body. This ...
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1answer
69 views

If a spaceship were to lose all fuel, where does it go? [duplicate]

If a spaceship were to run out of fuel mid-flight, and it was between two solar systems, one with 2 suns and 6 planets, and one with 1 star and 10 planets, where does it go? I feel like I’m missing ...
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2answers
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Why does Voyager 1 lose speed after the sudden gain in speed from gravity assist?

The Voyager 1 loses speed gradually after gaining speed from gravity assist. Is the external thrust is applied in the opposite direction to move closer to the planet, or does the spacecraft lose its ...
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1answer
56 views

Would a space rocket launching from Ceres in a path to Jupiter be faster relatively to the sun than one launching from Earth?

Suppose you have a space rocket which when launching from Earth its speed relatively to Earth it's 11 km/s. For what I've read in another topic in Space SE, the orbital velocity of the planet where a ...
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3answers
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What will happen to human body when affected by two opposing G forces?

(I am not quite sure whether I should be asking this question here or in Physics exchange or biology exchange, but i decided to place it here due to the context that this question came to my mind.) ...
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1answer
167 views

How to calculate slowing effect of a planets gravity on a projectile that is launched upwards

The acceleration a ballistic projectile would experience at a certain height above a planet (neglecting any atmosphere) is given by $$a = -\frac{GM}{(R + h)^2}$$ where $G$ is the gravitational ...
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1answer
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Can an Asteriod be marshalled as a spacecraft providing sufficent earth like gravity for those on it [closed]

Can a sufficient massed and size asteroid in a safe area from earth have engines added and provide earthlike gravity for occupants to bring them reasonably close to planets and earth for supply and ...
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2answers
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What does Earth's J₂₂ moment look like?

Wikipedia's Geopotential model give's the form of the potential component linked to $J_2$ as $$u = J_2\frac{P^0_2(\sin \theta)}{r^3} = J_2\frac{1}{r^3}\frac{1}{2} \left(3 \sin^2\theta-1 \right) = ...
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1answer
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Could you carry around with you a rocket pack to get off Mimas?

This question was inspired by the one here: Is there a self-rounding celestial body from which an Olympian could jump into space? regarding the, apparently shown infeasible, idea of jumping off what ...
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Is there a self-rounding celestial body from which an Olympian could jump into space?

Is there a self-rounding object in our solar system whose mass is insufficient to prevent the highest jumping human from escaping its gravity?
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2answers
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How big are the tidal accelerations within the ISS?

This question asks about placing an object at rest in the International Space Station. But the ISS is a large object, large enough that gravity will vary across it and cause tidal forces that can ...
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1answer
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Help with Vector format N-body state transition matrix

[Update] This is for an on-board autonomous navigation system (3-dimensions, interplanetary) using a Kalman Filter. There is no target trajectory. I have the position and velocity measurement models ...
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7answers
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How much stronger does gravity have to be for space travel to be impossible? [duplicate]

I’ve heard that only a slightly stronger gravitational pull would make it impossible for rockets to launch. Is this true? I’ve heard this used as the reason why humanity is meant to be in space.
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How do stable equilibrium points work in GEO? If all geosynchronous spacecraft suddenly lost stationkeeping, would most “fall into” one or the other?

The (currently unanswered) question Quantitatively, how deep are the stable equilibrium points in GEO? How much delta-v to move from one to the other? (also see comments at Delta-v to move from GEO to ...
6
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1answer
90 views

Gravity turn: How to reorient along zero angle of attack

I was doing some back-of-the-envelopish calculations on gravity turns. Now the basics are clear to me (I think), but this detail escapes me: After liftoff we perform pitchover manouvre at time T+x, ...
2
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1answer
134 views

How big would a collection of asteroids near the Moon's L4 point need to be to aggregate naturally into a “stepping stone” for space exploration?

Wouldn't it be useful to catch few meter sized near-Earth asteroids whenever opportunity knocks and "lock them up" at the L4 Langrangian point of our Moon ? Although at the L4 and L5 Lagrangian ...
2
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1answer
102 views

Is it possible to have a planet made entirely out of water? [closed]

Let's say we had a mechanism of adding unlimited amounts of water at a certain point in space. How much water could we add until the water molecules would turn into something else due to gravity? What ...
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5answers
14k views

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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2answers
214 views

Comparison of Titan to Europa

Why does Titan have an atmosphere denser than that of the Earth? And why does Europa not have even a fraction of Titans atmosphere given that it is not that small as compared to Titan?
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1answer
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Zonal vs Tesseral part of geopotential?

So I've only recent started to try to wrap my brain around geopotential models. I've done work with some special perturbations using $J_2$ before, however I've never dealt with a full spherical ...
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3answers
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Does trajectory of an object orbiting a planet depend on the object's mass? (With hypothetical Apollo example)

For example (hypothetically), if an Apollo crew of one of the lunar missions went on EVA just after Trans Earth Injection burn and carefully released a small bolt, or a plastic package from their food,...
2
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2answers
186 views

At a height of 100 km, what speed do you need to be going to escape Earth's gravity?

I understand that the escape velocity of Earth is 11 km/s. However, Earth's gravitational sphere of influence is not infinite, so it is possible to go slower than that and still escape the sphere of ...
2
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3answers
323 views

What is the gravitational acceleration of the Sun?

What is the gravitational acceleration of the Sun? I've seen numbers such as 274 m/s2, but that doesn't make sense to me seeing that relatively weak sources of spacecraft thrust such as Electric ...
2
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1answer
144 views

How heavy can a fuel tank get before making it heavier is a liability under any circumstances?

This Question may bend the boundaries of this community a little, since it's mostly about hypothetical rockets that would never be built. Considering a filled fuel tank has to withstand a lot of ...
2
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2answers
134 views

Would more or less gravity make you proportionately stronger?

It is known you can lift more if gravity is weakened, but more weighs less in less gravity. Though what is the ratio compare to normal gravity...like if you can lift 100% of your body weight in a ...
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1answer
125 views

The earth's moon versus Phobos and gravity

Our moon weighs 7.35 x 1022 kg and Mars' moon Phobos, weighs 10.6 × 1015 kg. How much would need to be added to Phobos to give it the same gravitational "impact" on Mars, as the Moon currently has ...
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1answer
100 views

Have gravitation multipoles of Jupiter and Saturn beyond J2 been measured or at least estimated? At least the zonal harmonics?

This excellent answer has me wondering if there are any measurements or estimates of gravitational multipole moments of Jupiter or Saturn beyond J2. Here is what I found for J2 (in unitless form) in ...
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1answer
132 views

What would be different about satellite orbits if Earth were prolate? Would we have Sun-synchronous and Molniya orbits?

It's hard to imagine how it could happen naturally since on geological timescales the Earth would either be spherical if it didn't rotate, or oblate if it did, but from an orbital mechanical ...
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1answer
178 views

What is the highest gravity planet we could launch a single person from?

According to some reports a human can survive at up to ~5 gravities while other reports suggest launching from > ~2 gravities might not be possible with rocket engines. Many super Earths have surface ...
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0answers
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Variable Gravity, how long in each?

Centrifugal force can be used to simulate gravity in space vehicles. Assume the "gravity" in our space vehicle can provide environments ranging from 2 gravities to none (micro), either by changing ...
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1answer
209 views

Halley comet flyby

Halley's comet's next perihelion will happen around mid 2061. Considering, that its orbit is retrograde (viewable here), is it possible to build a flyby trajectory by means of gravitational ...
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2answers
351 views

What are the calculations for gas transport to the Moon with a pipeline?

This paper, acquired from this question about tethers on the Moon, describes LADDER, a mission to deploy a Lunar Space Elevator (LSE). The space tether, made of Zylon fiber, would be 264,000 km long,...
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1answer
246 views

How were Mars' zero elevation datum defined? What are their shapes?

Discussions on Boiling ponds and pools on Mars? led me to Wikipedia's Mars; Geography and naming of surface features which says: Because Mars has no oceans and hence no "sea level", a zero-...
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1answer
6k views

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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10answers
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If a spaceship ran out of fuel somewhere in space between Earth and Mars, does it slowly drift off to the Sun?

Pretty much what the title is saying. I feel like I am missing something fundamental here and this is driving me crazy. Does a spaceship which is out of Earth's gravity drift to the Sun eventually?
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4answers
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How is lower/no gravity simulated on a planet with gravity, without leaving the surface?

I have seen videos of simulated lower gravity (possibly for training astronauts). I am curious what methods/techniques can be used to simulate lower gravity like environments without leaving the ...
3
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2answers
157 views

When calculating the future orbit of an artificial Earth satellite, is the Moon's gravity significant or insignificant?

Imagine a mathematician is plotting the future orbit of a satellite to be launched and put in orbit around the Earth. When they are making their calculation, is the moon so far away and the ...
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1answer
115 views

How do you calculate the ∆v required to increase apoapsis to a certain height?

To calculate the ∆v needed to increase our apoapsis from a low orbit of 100km to 400km, we find the velocity at 100km using the semi major axis (which is 250km, in this case), and then find the ...
2
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2answers
131 views

why dose reentry speed need to be so fast [duplicate]

I have been wondering this since I was a kid. watching films of capsules and shuttles heating up and all that tile trouble and work that went into all. I would always wonder why they dont slow down ...
2
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1answer
192 views

How do you calculate gravity loss (simplified)?

Assume a rocket with constant mass and thrust. To simplify things, we can ignore aerodynamic drag, and we'll also not perform a gravity turn, hence our flight plan is as follows: -Burn radially from ...
4
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1answer
459 views

Can a “gravity assist” at a black hole accelerate light faster than the speed of light? [closed]

With the help of a gravity assist from a black hole, can light travel faster than its natural light speed?? Satellites use gravity assistance. In a similar way can light traveling near black hole ...
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0answers
36 views

How much higher could g be before we couldn't launch rockets? [duplicate]

Obviously having a higher gravitational acceleration makes it harder to get rockets into orbit / escape. How much stronger could earths gravity be before we would no longer be able to do the sort of ...
13
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1answer
1k views

How many satellites can stay in a Lagrange point?

Lagrange points as I understand it are points in space between 2 objects where the gravitational pull between them is effectively equal. That makes station keeping at these points relatively easy. ...
2
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1answer
69 views

How microgravity in space affects body parts

There are things that naturally face downwards, like hands. How would they be affected in space microgravity? Would they rise or point downwards?
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2answers
271 views

What Gravity does the Sun affect items with at the distance of 1 AU?

At the surface of the Earth, the force of gravity is defined as 1 G. I am wondering what gravitational force the sun excerts at the distance of 1 AU (the distance Earth is at). Imagine it like this; ...
6
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1answer
113 views

What's the point/area of space called where there is equilibrium between 2+ different gravitational forces?

For some reason I want to call it a 'gravity well' but I know that a gravity well is just the gravitational force distribution in space due to an object with mass. But regarding my question, isn't ...
2
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2answers
136 views

What is the formula for Legendre Polynomials from EGM96 calculated in F447.f program?

The F447.f program is designed to calculate the geoid undulation for EGM96. I'm trying to understand how it accomplish this calculation. I stuck in ...
2
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0answers
148 views

Lambert problem solver needed for custom gravity in Python

I need to solve the Lambert problem, however, I have a custom gravity model. My ODE of motion is: ...

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