Questions tagged [physics]

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

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2
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0answers
147 views

What's the farthest an ISS astronaut gets from the station's center of mass during routine activities? At 0.5°/s what centrifugal effects are there?

This answer to Are there really “Dead End” signs on the outside of the International Space Station? won't be helpful here since for the purposes of this question spacewalks aren't part of routine ...
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2answers
288 views

Modeling a rocket using Tsiolkovsky's equation and ordinary differential equations

So I have this uni assignment to make a model out of ODEs, and my idea was to use rockets. After some research I found about Tsiolkovsky's equation and tried using it on a Falcon 9 (disconsidering ...
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1answer
106 views

Estimating thrust and kg fuel for a generation ship's journey to Alpha Centauri

Premise: A generation spaceship leaves Earth around the year 2060 on a journey to colonize Alpha Centauri A (ACA). In this fiction, fusion power is achieved in 2040, improved over 20 years, and used ...
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4answers
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If an astronaut threw a cup of coffee into space, would it freeze, or boil off into gas?

If an astronaut threw a cup of coffee into space somehow, would it freeze into a block, or boil off into gas due to the zero pressure?
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2answers
127 views

Would hypothetical aliens from super-earths be larger and stronger then humans? [closed]

I’m curious how physics would affect the size and strength of human like aliens on super-earth worlds with 1 to 2 times the gravity of earth compared to humans. Would they be similar or be larger or ...
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How does Curiosity's X-ray diffractometer work? Does it measure only one angle at a time or does it have an area detector?

Per this answer to Are quasicrystals common on the Moon and Mars?, Curiosity has an X-ray diffractometer. X-ray diffraction from 3D crystals can (begin to) be understood by embracing Bragg's law. A 3D ...
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1answer
3k views

Why can solid rockets be both the skinniest and most spherical launch vehicles while liquid fuel rockets have a more limited range of aspect ratios?

Question: Why can solid rockets be both the skinniest and most spherical launch vehicles while liquid fuel rockets have a more limited range of aspect ratios? Are there fundamental engineering ...
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Is a PhD in space-related technology from a Physics background possible?

I am 24 years old, from Argentina. Next year I will finish my 6-year degree in physics from the University of Buenos Aires (We've been told that it is equivalent to a master's degree, but maybe is ...
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1answer
152 views

If you travelled at exactly the speed of light, what would the stars look like behind you? [closed]

If you were in an Alcubierre drive bubble travelling at exactly 1 c, I wonder what it looks like if you looked back, to the direction you come from. If you went faster-than-light you'd obviously see ...
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1answer
91 views

Simple Ionic Drive Problem

I am having trouble with my calculated values for part B of the problem. In part A I used the formula F=qE, where F is the force, q is the charge = 1.6 * 10^-19 coulombs and E is the electric field = ...
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How much is really known about those liquid metal droplets orbiting the Earth? (e.g. sizes, composition, orbits…) Are any actually tracked?

The question Orbit Guardians - bs, right? mentions a company proposing a smallsat that will capture then give a roughly 200 m/s retrograde "kick" to liquid metal NaK alloy droplets in LEO ...
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2answers
224 views

Why is hydrogen better than helium as remass?

I just watched a very good YouTube video on why nuclear engines might be useful, and it also goes into why Hall Effect thrusters are super good at squeezing obscene ISP out of things. During the video,...
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1answer
135 views

How do grid fins actually work? Which aerodynamic mechanism(s) produce the torque on the spacecraft?

I’m trying to model the steering force that grid fins exert on a falcon 9. I know these things are not just grid-shaped fins but actually grids of fins. And each of those fins will experience drag and ...
2
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1answer
149 views

How difficult to gravity assist brake on entry to Alpha Centauri system? [duplicate]

Say a generation ship arriving at Alpha Centauri A system wants to get into orbit (or land) on an exoplanet there. After decelerating for the 2nd half of the journey, their approach velocity is still ...
4
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1answer
75 views

Kinetic reaction from emission of electromagnetic radiation

If an object is emitting 1 watt of electromagnetic radiation directionally and has negligible black body radiation, how much thrust is produced? How can you calculate this generally?
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1answer
80 views

Since Vesta is rotating, could you dig a habitat into it near the poles?

Would building a crescent shaped habitat work if you didn't want to go all the way? Edit: I'm asking if this would be enough to provide artificial gravity, sorry not not being clear about it.
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1answer
249 views

When does a specific equipment at a certain temperature start to freeze in interstellar space?

This is my first post here. I'm working on a project which involves a number of problems and some parts of that are related to empty space and space exploration. I try to be focused and reflect one of ...
3
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1answer
198 views

Pendulum rocket fallacy - so why *do* skyrockets have sticks?

This question is inspired by two, linked questions. Skyrockets (of the pyrotechnic/firework kind) have guide sticks, which are (according to internet sources) to enhance stability: "The guide ...
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1answer
294 views

Star-shaped artifacts in SAR images of the “Suez Canal traffic jam seen from space”

Wikipedia's 2021 Suez Canal obstruction links to the Sentinel-1 synthetic aperture radar (SAR) image of the Traffic jam in the Gulf of Suez caused by the obstruction as seen by the Sentinel-1 ...
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Help understanding vectors in diagram from “Magnetohydrodynamic flow control during reentry” and the actual goal of this research

A link to the ESA Advanced Concepts Team page Magnetohydrodynamic flow control during reentry was recently shared under Re-entry Heat Shield Alternative. It says: During the reentry phase, spacecraft ...
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4answers
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What is the “pendulum rocket fallacy” as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

I've received comments that explain to me that the analogy between rocket attitude control during a hovering maneuver and the act of balancing pencil on the end of a finger is a helpful and good one; ...
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How do you “make” a soliton? (recent peer-reviewed theoretical work in FTL travel)

I've just read an Article on the new approach on Warp Drives Dr. Erik Lentz describes. Instead of creating a bubble with negative energy density, he describes a Soliton in spacetime, which he ...
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2answers
69 views

Oberth Effect in Solar Sails: Where does the extra energy comes from?

Suppose, the reflectors of Solar Sails are opened for same amount of time at both periapsis and apoapsis. How does Oberth effect work in this case? Will Delta-V be same and hence change in Kinetic ...
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1answer
132 views

When they shoot lasers at the Moon for ranging, what is the shape of the beam?

Laser ranging of the Moon is usually done with a Q-switched pulsed laser fed into a big (1 or 2 meter diameter) telescope as a collimator in order to get a tight beam all the way to the Moon in hopes ...
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1answer
475 views

Understanding the rocket equation - calculating Starship delta v

I am trying to calculate delta v of Starship - both as separate stages (Starship [SS], Super Heavy [SH]) and as a fully stacked rocket including 100t payload. I know that I have to calculate 2 ...
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1answer
99 views

what would happen if there were windmills in space? [closed]

If there was a windmill in space and you spun it, would it spin forever creating infinite energy? or would it somehow slow down or not create energy? if instead of wind you used magnets to spin the ...
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52 views

Sources for values for realistic thrust calculation exercise?

I want to use this simplified equation to calculate the thrust of multiple different real engines: $$F = \dot{m} V_e + (p_e - p_0) A_e$$ Source: https://www.grc.nasa.gov/www/k-12/airplane/rockth....
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How to find/extract the semi-major axis from a TLE with Skyfield?

I have a TLE: 1 33591U 09005A 21024.46740879 .00000049 00000-0 52095-4 0 9997 2 33591 99.1927 41.5349 0014084 172.6670 187.4709 14.12449679616592 And I would like ...
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Masters in Space sciences after Aerospace Engineering [closed]

I'm currently in my first year of Aerospace Engineering and wish to pursue space sciences after graduation. Will I need some extra study in Physics other than my course to be able to successfully ...
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3answers
341 views

What happens if you jump on a “spin ship”?

If you're on a spin ship, or rotating wheel space station, and you jump, then you're no longer being accelerated by the rotation. What would happen? First, I'll establish some terms to make discussing ...
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1answer
96 views

Are solar sail spirals logarithmic? Can this be shown analytically or by dimensional analysis alone?

There are several questions and answers here about spiraling towards or away from the Sun using solar sails tilted by roughly 45 degrees to convert the sunlight's incoming radial momentum into ...
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1answer
964 views

What is the terminal velocity of SpaceX Starship?

What is the terminal velocity of starship on earth and mars during descent? Has SpaceX revealed or hinted the values of projected surface area and drag coefficient of the vehicle?
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2answers
352 views

Design of starship fins

How much can the falling speed of starship approximately be reduced by the bellyflop fall with fins? Are we talking about numbers around 5% or 50% here? Wouldn't it make sense to put holes where the ...
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3answers
6k views

Does it make any scientific sense that a comet coming to crush Earth would appear “sideways” from a telescope and on the sky (from Earth)? [closed]

In multiple different movies and fiction, there's the threat of a burning space comet heading for Earth, threatening to kill everyone and destroy the planet. One example is the animated Comet in ...
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1answer
83 views

Can I “tack” towards a laser beam from which I am powering my 100% efficient & massless ion engine?

As far as I know, for light and particles taking special relativity into account: \begin{align} E^2 &= (T + m_0c^2)^2\\ &= p^2 c^2 + m_0^2 c^4 &\text{ (particles)}\\[1.5em] E &= p ...
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108 views

How should mass specific impulse calculated for relativistic exhaust?

This answer says: Optimising for Isp only is problematic, as it's simply: $$I_{sp} = \frac{v_e}{g}$$ Which is the same as optimising for exhaust velocity. With no constraints on thrust, particle ...
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50 views

Why does Gravity Simulator's rendering of TESS' orbit look like a pretzel? How can I unpretzefy it?

Below is a screen shot from the amazing Gravity Simulator driven by our own @HappyKoala. If you haven't seen it recently go check it out now, then come back in 30 minutes and read the rest of my ...
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1answer
118 views

Could the crew of a spaceship with an Alcubierre warp drive survive if it only performs small “jumps”?

Could the crew of an Alcubierre drive-equipped spaceship avoid getting cooked alive by hawking radiation if their spaceship engaged and disengaged warp speed periodically over short distances?
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1answer
3k views

How hard is the hardest ice in the solar system? Is it in Pluto's ice mountains?

NPR's Pluto Has White-Capped Mountains, But Not Because There's Snow includes the following: "Initially, it seemed logical that this high-altitude frost could form like on the Earth," says ...
4
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1answer
179 views

Did the Space Shuttle crew have to worry about the ionosphere? What relevant training or specific briefings did they receive?

Comments below this answer tell us that the Space Shuttle always remained in Earth's atmosphere. When it visited the Hubble Space Telescope or the ISS or Mir it was still in the thermosphere and ...
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2answers
270 views

How to determine heat transfer for survival on Venus?

I'm trying to determine how long a probe could survive on Venus' surface. Assuming its just a sphere of titanium with room temperature air inside, what would be the best method for determining the ...
4
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1answer
539 views

How efficient and fast would seven Caplan thrusters be at pushing the Sun and would it be worth building more than one?

I was thinking about stellar engines. One type of stellar engine is the Caplan thruster, which concentrates the star's light onto the star's surface to create beams of solar wind, which are collected ...
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0answers
113 views

Which deorbit trajectory minimizes reentry heating?

Atmospheric reentry, as I understand it, is a balancing act between minimizing delta-v needed and not burning up or breaking up in the atmosphere. The higher the velocity on reentry, the greater the ...
2
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1answer
51 views

Specific Heat Ratio for a perfect gas mixture

I am reading Rocket Propulsion Elements by George P. Sutton & Oscar Biblarz, 9th Edition. In the fifth chapter, I was introduce to the specific heat ratio k for the perfect gas mixture, Eq. 5-7: (...
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1answer
402 views

Contracting rocket engine nozzles

The efficiency of rocket engine nozzles depends greatly on their expansion ratio an how well the ambient pressure matches the rocket nozzles exit pressure. An optimal expansion ratio means that there ...
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0answers
73 views

What is the maximum voltage of an Electric Sail?

Suppose we have an electric sail in LEO, how could one calculate the maximum voltage that could be sustained? It can't be infinite, there must be some limiting factors. Is there any ionization voltage ...
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0answers
135 views

What exactly is electron precipitation in Earth's ionosphere and how does it relate to the STEVE phenomenon? [closed]

Source Trying to decide if the unanswered question What was Steve? Is it called something else now? is in need of attention I checked Wikipedia's Steve (atmospheric phenomenon); Occurrence and cause ...
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2answers
2k views

Till what altitude above earth sounds can be heard?

In the new video of SpaceX SAOCOM 1B launch and landing RCS thrusters and other sounds can be heard during boostback burn. Falcon 9 boostback happens at nearly 100 Km altitude. Does the air density at ...
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1answer
228 views

What exactly gives a larger field of view to the donated “spy” telescopes that NASA may send to Mars? How much larger?

This answer links to Space.com's NASA May Launch Donated Spy Satellite Telescope to Mars which emphasized textsays: An unexpected gift The two donated telescopes were apparently built for a National ...
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75 views

I've looked at the Science involved but have doubts this would work, how can you generate momentum with-in a sealed system to produce propulsion? [closed]

Could you use a magnetic super-capacitor compound which is charged so it gains the maximum amount of weight\mass then is pushed away from the main object down a chamber using a magnetic field. As the ...

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