Questions tagged [physics]

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

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3
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1answer
100 views

How can a meteor gain energy in an encounter with the Earth even though these answers say it can't?

The question Did a spacecraft ever use an atmosphere to accelerate away from a planet? was unfortunately given five down votes and answered with: Entering the atmosphere introduces drag, which ...
2
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0answers
29 views

Cartesian vectors to keplerian orbital elements of binary system

I am looking to code a a function that converts my 3d position and 3d velocity of a binary system into keplerian orbital elements of the system. I have seen a few other posts on this but they always ...
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1answer
68 views

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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1answer
160 views

How did NASA calculate 22 million “rocket horsepower” for the SLS Booster?

This answer to Does NASA really report the power of rockets in horsepower? cites NASA news item Space Launch System Booster Aimed and Ready to Fire which says "What's impressive about this test is ...
5
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1answer
255 views

Is there some fundamental limitation that would prevent steam-powered rockets from reaching space?

According to the Discovery Channel (see CNN article below) the latest attempt to use compressed steam propulsion to get to 5000 feet ended in tragedy. It's not yet clear the altitude it reached, ...
2
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1answer
61 views

Would a small electron microscope in a cubesat work well in space at 400 km?

There is now an electron microscope in space! Suppose that once I win a lottery I can build a small, modest SEM column and put it in a 6U cubesat that opens one side to allow the electron optics to ...
4
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1answer
198 views

In layman's terms, how hot will the skin of a spacecraft become, 144 million miles from the Sun?

Ok, last week I asked how hot would a piece of metal become at a distance from Earth to Mars facing the Sun. Thank you for all the nice replies, but I do not have much math knowledge. So let me ...
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1answer
197 views

temperatures of metal facing the sun in space

If a piece of metal were orbiting the Sun at the distance from earth to Mars, always facing the sun, what would it's temperature be.
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3answers
315 views

How to solve this exercise in orbital mechanics; the moon stops in its orbit, what happens next?

As an exercise in orbital mechanics, suppose the moon were to suddenly stop orbiting Earth, and instead at time $t=0$ begin moving in the same direction as Earth so that their relative velocity were ...
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1answer
166 views

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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0answers
65 views

How much energy would be needed to liquify 1 gram of atmospheric oxygen on Mars?

I've been told I have no Moxie but I still need oxygen to live on Mars. I see that Mars' atmosphere is 0.14% oxygen and my sad moxiless self wants some. I want to make a low power refrigerator to ...
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2answers
205 views

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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1answer
137 views

What is a lithium fed GIT? How does it work?

This answer to What is the maximum speed an ion engine can propel a spacecraft at? mentions the following: Lithium fed GIT (gridded ion thrusters) have demonstrated 50,000 - 80,000 seconds of ISP (...
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0answers
96 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 ...
4
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1answer
86 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 ...
4
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1answer
109 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 ...
12
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1answer
548 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 ...
59
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6answers
10k views

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
133 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
83 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
96 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
183 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
202 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 ...
4
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1answer
251 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
131 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
185 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
297 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
140 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
80 views

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
139 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 ...
4
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0answers
167 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 ...
8
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1answer
141 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 ...
3
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1answer
143 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
702 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 ...
14
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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
145 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
96 views

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
187 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 ...
1
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1answer
236 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
276 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 ...
12
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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 ...
3
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0answers
174 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
176 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 ...
2
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3answers
282 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
114 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 ...
3
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1answer
182 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 ...
2
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1answer
194 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
183 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