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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11
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2answers
327 views

Least artificial gravity needed to maintain health on a one year space trip?

What is the least gravity needed for human health on a one year space trip?
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How does a planet's gravity push away smaller bodies that would otherwise intersect its orbit?

I was reading an article about dwarf planets online where I stumbled upon the following definition of a planet: The International Astronomical Union defines a planet as being in orbit around 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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On a Super-Earth 1.5x the volume and mass of Earth, would our rocket technology allow us to reach orbit? [duplicate]

To try and make parameters clear, can we say we are talking about 50% 'more Earth'? As in, Earth, but 1.5 times as big and heavy? And let us include the atmosphere. If there is 50% more of it by ...
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Pluto's satellites other than Charon orbits around Pluto or center of gravity between Pluto and Charon?

As the center of gravity between Pluto and Charon is outside Pluto does Pluto's satellites other than Charon such as Nix, Hydra, Kerberos or Styx orbits around Pluto or the COG?
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Besides retarded gravitation, anything else to worry about when calculating MU69's orbit from scratch?

For fun I'd like to use Hubble Astrometric data for example the observations listed at the bottom here to numerically estimate the orbit of 2014 MU69 as well as its uncertainties. My plan is to use ...
10
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595 views

Back to Earth's gravity, what astronauts do?

After a long period in space and once back to earth, what do astronauts to get again used to the Earth's gravity?
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481 views

Does NASA use Newtonian model of gravity for plotting the course of Juno or general relativity?

With the huge mass of Jupiter and its fast, approximately 10 hours daily rotation, there may be substantial twisting of space-time around it. A distortion of such magnitude that may call for ...
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1answer
599 views

Besides Luna, what celestial bodies exhibit lumpy gravity?

http://www.space.com/21364-moon-gravity-mascons-mystery.html writes to say ...These geologic structures, called mascons (short for mass concentrations), are so dense they alter the moon's ...
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Is is possible to generate centrifugal gravity by doing donuts?

With the correct rocket setup would it be possible to thrust around in a circle, like you would do donuts in a car, to generate centrifugal gravity?
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Can a satellite orbit the ISS?

Is stable orbit of a small satellite around the ISS theoretically possible with minimal station keeping?
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Why do malfunctioning satellites come back to Earth?

In school, I learned that if a satellite moves at a speed $\sqrt{gR}$ (the square root of the product of the acceleration due to gravity and radius of the Earth), then it will remain in Earth's orbit. ...
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How close would the Tesla Roadster with Starman have to get to Earth in order to become attracted and fall on Earth?

In 2091 the Tesla Roadster is said to maybe get closer to Earth than the Moon is. At Starman's current speed, would its location in 2091 be sufficient for the Earth to re-attract the Starman to let it ...
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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.
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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
255 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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Why does lunar gravity decrease?

I was exploring some queries about the moon and came across the question Which artificial satellites in lunar orbit are currently active?. In this, the accepted answer says: The lunar gravity field ...
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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,...
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431 views

Use Pluto's gravitation to reach the next dwarf planet

Why doesn't New Horizons fly by nearer to Pluto so the gravitational pull would slingshot the probe to one of the next dwarf planets in the outer solar system (Eris, Haumea, Makemake,...)? I would ...
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Impact of tidal forces to a liquid in a half-full tank

The german Wikipedia article about tidal forces contains a sentence which mentions, that tidal forces have an impact to an half-full fuel tank: Wo keine mechanisch feste Verbindung besteht, können ...
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810 views

Gravity Assist - Orbiting Satellites & Speed Increases

So, a gravity assist in very simple terms is when an object uses a planet's gravity and rotating momentum to increase the objects speed. If this is true, why doesn't the ISS get further and further ...
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Adapting to Increased Gravity on Alien Planets

What would mankind use in order to adapt or merely cope with the effects of a large increase of gravity on an alien world? Assuming there are no other problems we would face.
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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 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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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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How can an orbiting spacecraft's motions yield the orbitee's deep structure?

I've always been a fan of satellites like GRACE and GRAIL, where two satellites orbit a body, precisely measuring the changing distance between them in order to sense gravitational anomalies caused by ...
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1answer
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What does the Moon's gravity feel like? If you don't move, could you still tell you're on the Moon?

I am interested in descriptions and discussion from the Apollo astronauts. Almost all animals and many plants are sensitive to the earth's gravitational field. This is important for large mammals and ...
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1answer
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Sensitivity of Space Telescopes and Instruments

I have been doing a bit of light reading on space telescopes and have been amazed by the reported sensitivity of some of the instruments. In particular, the Laser Interferometer Space Antenna (LISA) ...
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110 views

To what celestial bodies are GRAIL-like missions planned?

GRAIL recently constructed a complete gravity map of Luna's irregular gravity field. Are similar GRAIL missions on the anvil to any other Celestial bodies as yet? As a corollary (probably opinion-...
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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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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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1answer
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Is there a profile of atmospheric pressure and gravity of Uranus?

One of the intriguing facts about Uranus is that somewhere within the gravity is about 0.9g. Now, if one wants to daydream about living on Uranus in slightly chilly balloons, it would be interesting ...
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542 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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How does gravitational stability change with the distance from special places such as geostationary orbit and lagrange points?

How rapid do the attractive properties of GEO and lagrange points deteriorate with the distance from optimum? How "large" are such locations? At what distance would station keeping require, say, twice ...
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4answers
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Can Oberth bike? Is biking up and down a series of hills a good real-world analogy for understanding either the Oberth effect and/or gravity drag?

When faced with a series of ups and downs while riding a bicycle, I try to pedal like mad near the bottoms to gain as much speed as possible. I do this due to some vague, ill-formed notion that either ...
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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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How to simulate Earth's gravity in future colonies on other planets?

What would be a viable means to simulate and maintain Earth's gravitational acceleration in a future colony built on another planet? I am mainly focusing on terrestrial planets, where a colony could ...
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2answers
349 views

Is there a term for the distance from an object at which it's gravitational pull is negligible?

I used to think that there was a point at which you escaped the Earth's gravitational pull. This is technically false, since every object in the universe is attracted towards every other object. Is ...
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1answer
2k views

How strong is the Sun's gravity at the distance of Jupiter's orbit?

I had read that the Sun's gravity at the distance of the Earth's orbit was 0.0006 times that of Earth's gravity. So, I was wondering what it would be further out, at the distance of Jupiter's orbit.
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682 views

If there was a probe orbiting at the edge of Earth's Sphere of influence, how slow would it orbit?

Would it orbit very slowly? It's kinda been stuck in my head lately...
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1answer
323 views

What would it be like to walk on the Asteroid 216 Kleopatra?

Here is some renditions of 216 Kleopatra. Kleopatra is a relatively large asteroid, measuring 217 × 94 × 81 km.Calculations from its radar albedo and the orbits of its moons show it to be a ...
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793 views

Shear forces between Shuttle, tank, and boosters - what pushes what?

This is the question that I should have asked here. The space shuttle and the two solid rocket boosters (SRBs) are mechanically attached to the giant tank. SRB's, shuttle, and tank all experience ...
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872 views

Source for up-to-date values of Mars' standard gravitational parameter

Wikipedia currently gives the standard gravitational parameter of Mars as: $$ GM_{Mars} = 4.2828(9) *10^{13} (m^3/s^2)$$ The (9) is the uncertainty of the last digit, so it works out to about ...
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How does gravity vary in a gas giant's interior?

The Earth's gravitational pull in its interior looks like this: The pull remains about the same and increases even a bit till the outer core from where on it starts getting weaker till 0g in the core'...
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1answer
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Does a gravity assist increase the g force on the ship?

In my mind, I picture a gravity assist sling shot boost like a ball on the end of string being swung until the centrifugal force grows strong and then is released. Where gravity is the string, the ...
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1answer
209 views

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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1answer
329 views

With so little gravity, would swimming on Enceladus be feasible for humans?

I'm working on a science fiction piece set on Enceladus, and I'd like the characters (human) to do a fair amount of swimming (they've managed to terraform a small bit of ocean for themselves). However,...
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1answer
942 views

How do I calculate lowest possible mission delta V from Escape velocities?

The gravitational potential of an object around the sun, relative to some point far far away (from the sun), should be smaller zero and proportional to $V_{escape}^2$. Hence the speed one needs should ...
6
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1answer
258 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, ...
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1answer
192 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 ...