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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How much does it cost to land on a lunar mascon?

This answer to Delta-v for landing on the moon estimates that to go from a circular orbit at 110km to a landing on a spherical Moon would require an absolute minimum of 1736 m/s and the Apollo landers ...
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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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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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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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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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Would human “superpowers” in low gravity fade away through reduced muscle mass?

If suddenly put in a low gravity as on the Moon or on Mars, humans should feel very strong, easily breaking some olympic records for example. Apollo astronauts have said that they did not get tired ...
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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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At what surface gravity can't astronauts do full steps anymore?

We know that on the Moon in ~1/6 g the Apollo astronauts couldn't make full steps because they jumped with each step. At what surface gravity could you walk more like on Earth and at what gravity ...
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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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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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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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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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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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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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Could a human jump off Mimas without return?

A similar question has already been asked on dwarf planet Ceres: Could a Human reach escape velocity by jumping from the surface of Ceres (a dwarf planet)? Ceres has 2.9% of Earth's gravity. Saturn's ...
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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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Earth gravity lens focus

Reading this question and then this report in a comment by @called2voyage At some point they talk about possibility to send (using antimatter as propellant) a space mission to solar gravity lens ...
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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 ...
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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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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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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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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 ...
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Will people living on Mars for several years be able to return to Earth without consequences?

Living without gravity has consequences for the bones and muscles. To counter that astronauts have to do exercise and lifting regularly when they go to the ISS. Are there similar plans to counter this ...
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How much is the difference of gravity attraction between the highest and lowest point on Mars?

Mars has a very high mountain, Olympus Mons (25 km), while Hellas Planitia is a 9 km deep crater. How much would the weight of a person weighing 100kg on Earth, change between the highest peak of ...
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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, ...
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Where is Luna 1?

Luna 1 was the first attempt by the Soviet Union to crash land into the surface of the moon but narrowly missed after a programming error becoming the first man-made object to escape Earth's ...
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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 ...
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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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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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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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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 ...
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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 ...
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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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Max g survivable suspended in water?

With something like a coil gun mass driver in mind where the more acceleration the cheaper the design in mind: If you were to suspend the astronauts in a shallow layer of water and horizontally ...
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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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Does prolonged space flight have any effect on the physical traits of the human body?

Can a variable of physical traits like height, weight, complexion be changed in outer space? Maybe by gravity or by something else that determines these traits (like the UV rays of the sun that ...
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Why did Voyager 2's velocity drop far below escape velocity before the first gravity assist?

As per @kasperd's comment on another question. Looking at the graph below, it appears that Voyager 2 started at just over escape velocity of the solar system. Just before the Jupiter flyby, it was ...
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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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For the mathematical relationship between J2 (km^5/s^2) and dimensionless J2 - which one is derived from the other?

The term $J_2$ seen in discussions of nodal precession of orbits (e.g. sun-synchronous) appears to come in two flavors. For example, in the Wikipedia article Geopotential model it has a value of $1....
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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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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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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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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 ...
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Could a Human reach escape velocity by jumping from the surface of Ceres (a dwarf planet)?

According to this answer the surface gravity of Ceres is estimated to be only $0.27 m/s^2$. With a rotation period of 9 hours. The gravity seems light enough to overcome by leg muscle alone, and if ...
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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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Is it possible to perform the Galileo's Leaning Tower of Pisa experiment on the Moon?

Since the Moon has no atmosphere, is it possible to perform the Galileo's Leaning Tower of Pisa experiment on its surface? Has any astronaut performed anything similar?
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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 ...
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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 ...