Questions tagged [physics]

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

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How to plot a satellite's orbit around Earth in MATLAB?

Given orbit height, mass and initial velocity how should I plot a satellite's orbit in MATLAB? I was hoping to use verlet integration (I need to implement a solver) possibly the velocity-verlet. I ...
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9 votes
2 answers
436 views

How does Spinlaunch manage the counterweight right after launch?

Spinlaunch has successfully launched a suborbital test vehicle from a 1/3 scale demonstrator, see for instance aviationweek.com or space.com. While spinning up the arm, perfect balance is achieved ...
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How much energy is lost by damping yaw from a SpinLaunch?

SpinLaunch hopes to launch a 200 kg satellite from a ground-based centrifuge, at 5000 mph, and more troublingly, at 450 rpm aka 7 tumbles per second. (The 3000 rpm figure mentioned in its tech sheets ...
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13 votes
1 answer
2k views

Why is the sunny side of JWST's sunshield purple and covered with silicon?

After about 08:52 in Destin's Smarter Every Day's Why Are there Holes in the James Webb Sunshield? (Explained by My Dad) - Smarter Every Day 270 (linked below) ...
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3 votes
1 answer
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Why is the eccentricity vector used to describe near-circular orbits?

When dealing with near-circular orbits I've seen the usage of the eccentricity vector defined as $$(e_x,e_y) = (e\cos\omega, e\sin\omega)$$ I've seen this in Schaubs' "Analytical mechanics of ...
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2 votes
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What do/will "quantum gyroscopes using nitro­gen-vacancy centers in diamond" for space applications actually look like, and how do they work?

The NASA page ELaNa 41 Mission has a section labeled QubeSat - University of California, Berkeley which says: QubeSat is a technology demonstration mission. It will test and character­ize the effects ...
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3 votes
1 answer
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To what percentage of the speed of light you need to accelerate to get artificial gravity at 1g?

Let's say you have a very powerful hypothetical fusion or matter/antimatter drive on a spaceship and you want to travel to a star nearby. Can you get 1g artificial gravity by accelerating? Or close to ...
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2 votes
1 answer
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Questions about orbital ring math from Birch 1982 paper

I have been reading the original Paul Birch paper published in JBIS 1982. I have been using this copy found here. In particular I am wondering about generalizing the ideas, like for a different planet ...
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5 votes
2 answers
467 views

How does gravity change beyond L2?

Why does gravity appear to increase again on the far side of L2 from earth as indicated on the gravitational contour diagram? One would expect gravity to continue to decrease as the distance from sun ...
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Would the ship using the Alcubierre drive need to use conventional propulsion to move during warp? Or would the space-time "wave" push it?

I have found various explanations on how the warp drive works. And right now I'm confused. First I thought warp drive works by expanding space-time behind you, and contracting it in front of you. I ...
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0 votes
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Have artificial quasicrystals ever been intentionally formed in space, or even attempted? If so, which was the first?

After asking Proposing a 2D quasicrystal; what are the necessary and sufficient conditions? (If it looks like a duck and quacks like a duck, or...?) I ran across Efficient design, accurate ...
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6 votes
3 answers
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Could you survive very high G's if your whole body was accelerated uniformly?

Could you survive high g's if your whole body was accelerated uniformly (not just by the seat of a rocket pushing on your back)? Your body is really only affected by gravity if you are touching ...
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4 votes
2 answers
351 views

Understanding g₀ to calculate delta-v

I am trying to calculate the exact delta-v from various existing upper stages with a given payload in a vaccum and in orbit, say LEO. I understand that according to the Tsiolkovsky rocket equation: $$\...
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6 votes
2 answers
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What can be determined about an orbit if it passes through two points

Using a 3D Cartesian coordinate system if we know for certain that a craft will pass through two points in it's orbit (let's call them p1 and p2) and we also know the mass of the central body it is ...
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What is the best place on the internet to learn basic physics needed for rocket engineering? [closed]

Does anyone know a site where everything is in one place and it teaches equations and pricipals from the basics?
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2 votes
1 answer
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Can a space craft realistically eject flares to evade a missile?

I was watching Behind Enemy Lines, and one of my favourite scenes is the jet attempting to evade the missiles. All this got me thinking about the Defiant from Deep Space Nine, and some research shows ...
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3 votes
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Given 10W and a 100 m^2 target to look for from LEO, which can search a larger area; SAR or LIDAR? (back of spherical cow-shaped envelope question)

Background For the project discussed in Space based active optical sensors for maritime surveillance the concern seems to be that SAR is off the table because a low inclination orbit is in eclipse ...
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2 votes
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What is MAHLI's theoretical or expected best optical resolution? How was it defined? Was it verified on Mars?

The block quote in this answer to Has Curiosity ever taken a good hard look at the dirt covering its top surface? Can it? Have individual particles been sized? says that at a focus distance of 2.5 ...
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23 votes
2 answers
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When burns are made during inefficient parts of the orbit, where does the lost energy go?

Any Kerbal Space Program player will know that burns prograde and retrograde to the velocity vector are most efficient closest to the body being orbited, while burns normal and anti-normal are most ...
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3 votes
2 answers
223 views

What is the theoretical smallest size limit for a phased array antenna that can reach LEO?

Now that one provider is operating a phased array ground-to-satellite internet comm system, others will follow. A frequently asked question is "When can we use Starlink with a sat phone?". ...
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2 votes
0 answers
172 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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4 votes
2 answers
412 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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3 votes
1 answer
350 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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36 votes
4 answers
12k views

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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0 votes
2 answers
139 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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12 votes
1 answer
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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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0 votes
0 answers
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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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1 vote
1 answer
157 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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0 votes
1 answer
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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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11 votes
1 answer
287 views

How much is 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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3 votes
5 answers
485 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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2 votes
1 answer
196 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 ...
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2 votes
1 answer
172 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 ...
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4 votes
1 answer
90 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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1 vote
1 answer
86 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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2 votes
1 answer
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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 ...
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3 votes
1 answer
282 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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9 votes
1 answer
446 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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2 votes
1 answer
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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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18 votes
4 answers
5k views

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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4 votes
0 answers
346 views

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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2 votes
2 answers
177 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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1 vote
1 answer
149 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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6 votes
1 answer
756 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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-1 votes
1 answer
107 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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1 vote
0 answers
56 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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1 vote
0 answers
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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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1 vote
0 answers
24 views

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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4 votes
3 answers
790 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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