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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43
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4answers
13k 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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0answers
40 views

What would happen if the universe suddenly stop moving? [closed]

I know we’re not only rotating on our own axis but around the sun and around the center of the Milky Way. But we’re also moving at incredible speed through the universe. What would happen if that ...
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2answers
171 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?
7
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1answer
94 views

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
1k views

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,...
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2answers
155 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
202 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
132 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 ...
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2answers
97 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
106 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
97 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
153 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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59 views

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
208 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
328 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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0answers
122 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 ...
14
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9answers
11k views

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
3k views

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
147 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
70 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 ...
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2answers
116 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
81 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 ...
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1answer
412 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 ...
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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
68 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
148 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; ...
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0answers
42 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 ...
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2answers
126 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 ...
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0answers
118 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: ...
6
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1answer
124 views

What would a candle flame look like in low gravity?

We know what the flame of a candle looks like on Earth in 1g and what it looks like in weightlessness. But do we have an idea of what it would look like in Lunar (0.166 g) or Martian (0.38 g) gravity? ...
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0answers
137 views

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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2answers
1k views

Supports in 3d printing

Do astronauts print 3D in space with supports? They are needed only because of gravity, which - on a space station - obviously is not a problem.
8
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1answer
305 views

What was Sutton talking about? How to “obtain small accelerations by taking advantage of difference in gravity as a function of altitude”?

Sutton and Biblarz's Rocket Propulsion elements says in Chapter 1, section 1.2 (editions 7, 8, 9, possibly earlier as well) that: Totally different methods of producing thrust are used in ...
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4answers
9k views

If human space travel is limited by the G force vulnerability, is there a way to counter G forces?

I read somewhere that prolonged G forces (even 2 Gs) are not tolerated by human physiology and that this ultimately limits our ability to sustain space travel. Are there any tactics to reduce G force ...
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2answers
161 views

Would a mouse trap snap faster or slower in space than on Earth?

Would a spring loaded mechanism outside a spacecraft activate a lever faster or slower in space with no atmosphere and gravity than on Earth? Basically this is in reference to mechanical instruments ...
8
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1answer
207 views

How far will the debris cloud from Hayabusa-2's touch-and-go sample recovery travel around Ryugu? Will any have escaped to heliocentric orbit?

HAYABUSA2 MOMENT OF TOUCHDOWN This animation, extracted from a longer video, shows the moment of Hayabusa2's 21 February 2019 touchdown on asteroid Ryugu. JAXA Source: Planetary Society's Watch ...
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1answer
111 views

Time to fall into the Sun from Mars orbit

If a body starts to fall freely from Mars orbit towards the Sun, then how can we calculate the time to touch the Sun' surface? I have tried the third equation of motion that says R=(1/2 dg)*dt^2. ...
2
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1answer
141 views

Will people living in 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. Now are there any plans to counter ...
2
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1answer
161 views

Ballistic missile typical trajectory - along which path is it supposed to travel between Russia, China and US?

Today I was puzzled when my son was holding a school globe asking me to show with my finger a trajectory of a (nuclear) ballistic missile flying from US to China and Russia and vice versa (from Russia ...
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1answer
113 views

How much is the difference of gravity attraction between the highest and lowest point on Mars?

Mars has a very high mountain, wich is the Olympus Mons measuring 25 km; while Hellas Planitia is a 9 km deep crater. How much the weight of a man that on Earth is 100kg, change between the highest ...
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3answers
236 views

Do Curiosity's reported measurements of Mars' surface gravity (~3.717 m/s^2) include centrifugal effects?

In this answer I discuss the first results in the 47th Lunar and Planetary Science Conference (2016) conference paper First Gravity Traverse on the Martian Surface from the Curiosity Rover and a more ...
5
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3answers
443 views

Two 1000 kg gold spheres orbit their CM in near-contact, great way to measure G or limited by spaceflight issues?

The hypothetical, non-existent crowdfunding site go-launch-me is so confident, they are offering a two-for-one special. For a limited time, if your project is funded they will foot the bill for a 2nd ...
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1answer
61 views

Using DART to measure G

NASA plans to launch a mission called DART to kinetically impact an asteroid, primarily for the defense of Earth. One thing that I've been thinking about is the same mission could be used potentially ...
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2answers
392 views

How would you move in low gravity without a suit?

Assuming your in a habitable environment, how would you move on a planet or moon with significantly less gravity without the encumbering EVA suit?
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1answer
224 views

How to manage landing on unlandable asteroids?

If asteroid's rotation period provides greater centrifugal force than gravity, having tangential surface velocity greater than escape velocity, and/or if due to an oddly enough shape, it has no fixed ...
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2answers
10k views

Could colonizing Moon dangerously affect its gravity?

If we colonized Moon it would mean we are moving matter from Earth to Moon. Since Moon is much smaller than Earth could these changes somehow affect its trajectory/movement to the point we could ...
3
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1answer
285 views

Time dilation between Mars and Earth due to different mass

I am not sure I understand the Time dilation correctly but if mass has dirrect impact on time...than lets consider cosmological event - one orbit of planet Earth around Sun. This event will person on ...
5
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1answer
88 views

Would a person exposed to zero gravity for a long time have trouble riding a bicycle?

I just watched this video by Drew Feustel showing him having trouble walking upright after 197 days on ISS: https://mobile.twitter.com/Astro_Feustel/status/1075889929119547393 They say once you have ...