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Questions tagged [gravity-fields]

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3answers
158 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 ...
6
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0answers
446 views

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....
2
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1answer
123 views

Which perturbs LEO satellites more, the Moon's gravity directly, or the changes in Earth's gravity field due to the Moon?

Reading this tutorial answer on models of Earth's gravity field I was realized that I'd never thought of it as time dependent. According to it, the biggest short term changes in the shape of Earth's ...
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2answers
514 views

What formulas do I use to calculate the gravity and drag forces on an object ascending from Earth's surface?

I'm trying to model a slingshot launch to space, literally, and I'm using 2 basic formulas. Simplifying my model, a object with a (really big) initial velocity is launched from Earth's surface on the ...
3
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1answer
73 views

What kinds of objects could we potentially observe through gravitational waves? [closed]

With the discovery of gravitational waves, I keep hearing that we now have a "totally new way to explore the universe." But as I understand it, gravitational waves are only detectable when they come ...
7
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2answers
194 views

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 ...
8
votes
1answer
416 views

How to calculate libration amplitude of objects orbiting the $L_4$, $L_5$?

Is there a way to calculate the libration amplitude of a test object that orbits the $L_4$ or $L_5$ Lagrange points? By amplitude I mean the distance along the orbit between the two extremes of ...
16
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1answer
972 views

How does orbital eccentricity affect positions of Lagrange points $L_4$ and $L_5$?

It is often said that the $L_4$ and $L_5$ points are "60 degrees ahead and behind" a planet like Jupiter. Clearly this is true only in the case of circular orbits. In more elliptical orbits, I assume ...
15
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2answers
976 views

What was the mascon “fix” used by Apollo 12?

According to the mascon entry on wikipedia: At that time, one of NASA's highest priority "tiger team" projects was to explain why the Lunar Orbiter spacecraft being used to test the accuracy of ...
9
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1answer
1k views

Alternatives to centripetal force and constant acceleration to simulate Earth-like gravity

This is follow-up to @Erik's answer to the question Is artificial gravity feasible in manned long-term space exploration? I'm curious, whether there's any alternative methods to simulating effects of ...