Questions tagged [physics]

How physics applies to a particular activity in space or to getting to space.

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80 views

Would it be possible to make a bubbleworld in an asteroid?

Would it be possible to drill a bore hole into an asteroid, fill it with water tanks and use sunlight to blow a hole large enough to fit a rotating space station inside, seal it off and fill it with ...
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1answer
75 views

Analytical treatment of relative positions between satellites?

I have been searching the internet for estimation of relative position between two satellites. However, all sources seem to be pointing to methods used for proximity operations, where the math ...
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1answer
101 views

What does S represent in Chris Hadfield's D = ½ ρ v² S?

Retired test pilot, CSA astronaut and ISS Commander Chris Hadfield's new Master Class advertisement video Chris Hadfield Teaches Space Exploration - Official Trailer - MasterClass is heavily edited ...
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1answer
463 views

Does the “Tennis Racket Theorem” apply to the ISS? Does it rotate around its intermediate (unstable) axis?

Wikipedia's Tennis racket theorem begins: The tennis racket theorem or intermediate axis theorem is a result in classical mechanics describing the movement of a rigid body with three distinct ...
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6answers
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When was Newton “not good enough” for spaceflight; first use and first absolute requirement for relativistic corrections?

Concepts in Special Relativity (1905) and of General relativity (first developed between 1907 and 1915) substantially predated spaceflight; they were well known and had been tested well before objects ...
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1answer
126 views

Space and Newton laws

I've read some articles which explain that we can't totally rely on Newtonian gravity concepts for understanding the motion of objects in space. My question is how the use of relativity helps us to ...
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2answers
77 views

Given r/a, what are the limits on the direction that an orbiting body could be moving (e.g. solid angle vs r/a)?

An orbiting object at distance $r$ and semimajor axis $a$ will move at $\sqrt{2 - \displaystyle \frac{r}{a}}$ times the speed of a circular orbit at $r$, no matter what the eccentricity or which ...
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1answer
91 views

When is it okay or at least helpful to use energy arguments in orbital mechanics?

When faced with energy-based questions about spaceflight we often comment something like orbits are about momentum, not energy and use delta-v math in answers. But in this answer to How big a nuke ...
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2answers
172 views

How big a nuke would be needed to break Phobos out of orbit?

Phobos Radius: 11.267 km Orbital period: 8 hours Equatorial rotation velocity: 11.0 km/h (6.8 mph) (at longest axis) With an 8 hour orbit around Mars it must be going at a fair clip already which ...
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1answer
190 views

Explain this light and wavelength graph

Would someone please explain this graph. I am not an expert and with my limited understanding of physics, I am unable to correlate this graph between the light received with its wavelength. I don't ...
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1answer
235 views

Why don't spacecraft get left behind once in deep space?

On earth, I know that if I throw a tennis ball straight up while in a car, it comes straight back down thanks to Newton's first law. The ball, the air in the car, and myself are all moving at a speed, ...
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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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1answer
82 views

How can Earth-Centered Inertial (ECI) coordinates be properly called “inertial” if the Earth's orbit is always accelerating towards the Sun?

I've just realized (again) that I don't understand anything, something that often happens to me after reading a @DavidHammen answer. How can Earth-Centered Inertial (ECI) coordinates be inertial if ...
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2answers
164 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 ...
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2answers
242 views

What information can I get if an elliptical orbit intersecting a circular orbit of radius 𝑟 and velocity of ellipse is equal to velocity of circular?

How can I approach solving the question below? Consider an elliptical orbit intersecting a circular orbit of radius $r$ as shown below. If $v_{ellipse} = v_{circular} = v $, find: True ...
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1answer
139 views

Can sunlight be utilised as a mining “laser drill”?

Can sunlight be used to bore a hole into an asteroid in the belt, so metals with a high enough melting point are left behind, ablated off for easy recovery? Or is the sun too far away?
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1answer
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Could a magnetic scoop work as a means to refuel a tank with hydrogen in orbit?

How effective would this be or would the Earth's magnetic field make it useless? Would it take too long for this to be of any use?
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1answer
124 views

Would air circulate in a rotating station on its own?

I know air circulation was a tricky problem on the ISS . I think that in a rotating station the air would be moving with the station, but the air against the “floor” would be moving faster or have ...
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162 views

If Planet 9 is indeed a black hole, what kinds of things could we learn from it?

I saw a recent paper speculating that planet 9 might actually be a primordial black hole. I've heard people say that if true, this would be a new era for science. But specifically, what could we learn ...
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1answer
107 views

what happens to particles that escape the atmosphere on planets in the solar system?

What happens to particles that escape the atmosphere of planets? (not just earth). Do they eventually form a uniform distribution of particles overtime? Do they inevitably to fall into the ...
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1answer
129 views

How much less delta-v would it take to reach the Sun using Venus and Earth flyby's compared to direct?

@TomSpilker showed that the minimum delta-v to go from Earth orbit into the Sun is about 20.89 km/s. That's going from 200 km LEO to "perihelion at the sun's photosphere (guaranteed complete entry!)" ...
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2answers
647 views

What's the eccentricity of an orbit (trajectory) falling straight down towards the center?

Discussion below this answer has got me thinking. A circular orbit has eccentricity of $\epsilon = 0$, ellipses $ 0 < \epsilon < 1$ (between but not including 0 and 1), and parabolic and ...
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2answers
3k views

Could a complex system of reaction wheels be used to propel a spacecraft?

I was think about different ways spacecraft could feasibly move around and I came across Reaction Wheels as a way they can rotate. So I was curious if a complex system of them could be used to propel ...
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4answers
144 views

What kind of force is there in exact middle of earth? [closed]

Basically i have one question but this question leads to another. firstly can we dig in earth that from one side we reach other side of earth ? i mean just going through it. Now let's say we can dig ...
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1answer
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Understanding line of sight between two satellite with oblate Earth using “scaling k-component”

I have been doing some reading on accuracy of determining line-of-sight between two satellites give a WGS84 oblate earth. The paper Rapid Determination of Satellite Visibility Periods (Alfano, Negron ...
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1answer
168 views

Magnetic force-driven propulsion system for an interplanetary/interstellar spacecraft

I have come up with a conceptual idea of a magnetic force-driven space propulsion system. What I believe is very unique about this propulsion system concept is that its working principle should not ...
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7answers
4k views

Is it possible to get a spacecraft into earth orbit using Linear Eddy Current Braking on an orbital runway?

The "Space Runway" [I have slightly edited this to clarify some issues that have been raised] Luke Parrish mentioned an unusual and novel space launch method to me. The idea is to get a spacecraft ...
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1answer
226 views

Could a CubeSat be propelled by this low-tech electromagnetic propulsion system?

I have come up with a conceptual idea for a low-tech electromagnetic propulsion system for a CubeSat, and I would like to know if it would create (on a theoretical basis) a net force strong enough to ...
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3answers
230 views

Do spinning space stations slow down without energy input?

One thing I always wondered was if a giant spinning space station that was providing artificial gravity would slow down without any energy input. I would assume that energy is being lost to heat as ...
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7answers
8k views

Could a space colony 1g from the sun work?

Let me break down my thoughts and I have no science background so let me know if this could even be possible. Have the colony on an object like a big asteroid or a similar man made construct. Have ...
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0answers
166 views

Have there been any Foucault pendulum demonstrations in space?

A Foucault pendulum is a pendulum allowed to oscillate in 2 directions, unlike the pendulum in a clock which is restricted to 1 dimensional oscillation. On Earth, (except at the equator) the plane of ...
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1answer
161 views

What might be a viable avenue of propulsion research in aiming for mission delta-V north of 100 km/s?

This question was inspired by some comments of mine I left on an answer here: Is it better to develop more powerful rockets instead of seeking and developing new technologies? and thus in turn both ...
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3answers
230 views

Stability of rocket during flight; why does the lift force change direction when the center of pressure moves?

I am currently learning about fins and the role they play in the stability of a rocket during flight. I came across a relatively minor problem. Here is one of the resources I'm looking at: http://www....
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1answer
105 views

Is it better to develop more powerful rockets instead of seeking and developing new technologies? [closed]

I have question about Space Industry and Era. I'm aiming to being Rocket Scientist but I think it looks like will be so hard to reach far planets with these rocket technology that uses Newton's Laws ...
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1answer
157 views

Some exercise questions about Tsiolkovsky's Rocket Equation and Thrust Equation

I have found 6 of the question's answers, but I don't know they are correct. The last question about time of the burn I get negative result -0.42 seconds. Time could not be a negative value, so I ...
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1answer
151 views

What are Mass Rate(∆v)/∆v, Mass Rate(Isp)/Isp and time of burn(MR)/MR graphs?

I have some problems about Tsiolkovsky's Rocket Equation and some graphs. Firstly, I didn't get what I can do with Rocket Equation formulas as seen below, Also, what these three graphs try to mean? ...
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2answers
153 views

Average acceleration of a rocket

Given a rocket has a minimum acceleration with full tanks of say 1 g and a max acceleration with empty tanks of 3g, what's the average acceleration? Is it just 2
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2answers
171 views

Could electricity be generated from a Martian dust storm?

This helicopter is producing static electricity from the blades moving through the dusty air. Along with the electricity provided by wind generators could additional power be created this way from ...
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2answers
138 views

Flat-spin transition manoeuvre: why is the angular momentum not constant?

In an article by Rahn and Barba, in which a flat-spin transition manoeuvre is investigated, the following figure is presented: I'm trying to reproduce this figure by integrating the following coupled ...
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59 views

How does temperature affect a solar sail?

Is there an ideal temperature which solar sail material operates at? Does a colder reflective surface create more thrust? Related: How will JWST manage solar pressure effects to maintain attitude and ...
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3answers
324 views

How will JWST manage solar pressure effects to maintain attitude and station keep it's unstable orbit?

The James Webb Space Telescope presents a huge reflective cross-section to the Sun's photons, and this can generate both torque and thrust. How will JWST manage solar pressure effects to maintain ...
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1answer
139 views

Can a reaction wheel decelerate to add momentum in the same direction? [closed]

Can a reaction wheel shed weight to gain speed? Could a reaction wheel at its max spin be flipped or rearranged around 180 degrees then slowed to add to its velocity?
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1answer
194 views

Could this satellite wobble in orbit creating additional orbital angular momentum?

This question asks if this type of steam engine would work: Could a steam Engine outperform other electric producing devices in space? this not a sterling engine since it has far less moving parts. ...
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1answer
107 views

What is the point in which metal turns white hot during launch or reentry called?

This is a slow motion film of the Sprint missle. There is a point where to skin goes white hot like a light switch. What is that called? What metal gets white hot while keeping its shape?
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9answers
6k views

Would a grinding machine be a simple and workable propulsion system for an interplanetary spacecraft?

I am wondering if any space agency has ever considered using a grinding machine as a propulsion system for an interplanetary spacecraft. This system would not be used to lift the spacecraft off of a ...
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1answer
192 views

Could escape velocity be achieved in the atmosphere?

When rockets launch for orbit they travel up and the air thins respectively to the speed increasing. How fast can a rocket for travel at sea level before it would fail or the elevation would have to ...
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0answers
214 views

Could a steam Engine outperform other electric producing devices in space? [closed]

What would be the Specific Impulse of a steam-based propulsion system like this model in space? Are there any types of engine that works this way? Could 2 tanks be designed to rotate slowly in space ...
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2answers
2k views

What is the smallest body in which a sling shot maneuver can be performed?

This question asks about the smallest sling shot maneuver performed. What was the smallest intentional, acknowledged slingshot maneuver? I'm asking how small of an object be to perform a sling shot ...
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2answers
293 views

Could a fat rocket be used on Mars?

Since Mars' atmosphere is around 2% the density of Earth's then could a much wider rocket achieve orbit? Could the rocket be in the shape of a capsule or an optimal shape for reentry on Earth?
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1answer
94 views

What is the vapor pressure limit of liquid metals in space?

Would liquid metal be stable in space unlike most other liquids like water? Are there any metals that has a high vapor pressure limit? Side question: Can liquid metal be given an electromagnetic ...