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Questions tagged [physics]

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

2
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78 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?
-1
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1answer
54 views

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

Let's say a tungsten meteor in orbit melted would it stay in a ball minus the Roche limit of the Sun distrupting the ball? Would liquid metal be stable in space unlike most other liquids like water? ...
2
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3answers
195 views

How fast can an orbit exist in the solar system?

How fast is too fast to stay in orbit around any particular large body in the solar system?
2
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1answer
81 views

What is the order of magnitude forces due to Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare?

What in order of magnitude does pressures vary in LEO due to diamagnetic repulsion of Earth's magnetic field, sunlight, drag, oblateness and tidal forces compare on an ideal satellite? Is there any ...
4
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3answers
345 views

Walking in a rotating spacecraft and Newton's 3rd Law of Motion

I am wondering how Newton's 3rd Law of Motion would apply in the case of a man walking the length of a rotating spacecraft. Please reference the drawing below. Say that there was a spacecraft ...
7
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1answer
155 views

Launching east from a mountain on the equator at midnight during a new moon; ranking of each contribution?

This answer is intriguing and I'm curious if it's correct, and especially which effects are most important. If you want to avoid gravity assists, the most fuel-efficient way out of the Solar System ...
1
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3answers
112 views

Delta-V to accelerate to/decelerate from .5c

I have a reasonably good understanding of delta-V (from playing KSP). However, I don't have a great understanding of how it works once you start running into the limitations of physics. I know that ...
4
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1answer
101 views

Is a kilowatt per square centimeter a typical launch engine's thermal energy flux (density)?

I saw the following image while searching for this answer in Sung Hwan Kim's thesis Germanium-Source Tunnel Field Effect Transistors for Ultra-Low Power Digital Logic It plots power density in Watts ...
1
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1answer
77 views

Heat Shielding Material for Reusable Craft

I'm a bit new to all this and have a quick question about heat shielding. My research tells me that for reusable craft (i.e. Space Shuttles) they used to use a plastic-based shields that would burn ...
1
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1answer
408 views

How to drink water on Mars?

There are craters filled with water on Mars as shown below. If fresh water is found, how would astronauts drink the water? Can the Apollo a spacesuit food/drink port be used to equalize the pressure ...
0
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1answer
84 views

Help with my tensor tension; how to derive and calculate this rigid body gravity gradient torque?

Tensors make me tense. Imagine a long thin rod in a circular orbit. The gravity gradient will produce a net torque on the rod whenever it is not oriented parallel, or perpendicular to the radius ...
3
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1answer
110 views

Help with Scott Manley's rigid body dynamics narration

I've just watched Scott Manley's video SpaceX's Water Landing Reveals Rocket "Secrets" (or, What We Learned from CRS-16) (again) and there's some rigid body dynamics in there where I'm not sure I am ...
5
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1answer
570 views

Would any manned orbital launches to date have been possible (but lower) if they were launched retrograde instead of prograde?

Manned launches have always been launched prograde to take advantage of the Earth's rotation velocity boost, and often in order to match the prograde orbit of another spacecraft for rendez-vous. I ...
3
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1answer
136 views

Could protons in the Sun's solar wind be used to create a photonic laser thruster for a spacecraft?

I have a conceptual idea for a photonic laser thruster for a spacecraft and I am wondering if this particular idea has already been thought of and whether or not it is capable of generating enough ...
1
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0answers
108 views

Backwards time dilation paradox [closed]

We have a pair of atomic clocks. Let's call them clock A and clock B. We switch both of them on at the same time. Clock A will stay on Earth and clock B will go with the astronauts. Astronauts with ...
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0answers
48 views

Could outer system probes detect lasers shone at them from earth (orbit)?

Does the Voyager spacecraft have instruments capable of detecting laser light if shone at them? New Horizons certainly does. Any other probes? Is there any laser capable of accuracy and power enough ...
2
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1answer
148 views

Why would the orbit of a satellite in GEO climb by 21 km in altitude over six months by itself?

This answer mentions several effects that tend to move geostationary satellites out of their "box" over time, but one really surprised me. According to the plot below (from there, but uncredited) the ...
0
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1answer
127 views

Which point in an orbiting body most closely follows its Keplerian trajectory?

Keplerian orbits can describe the motion of a negligible mass around a massive fixed central body, but they can also describe the motion of two bodies around their center of motion... with some ...
1
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1answer
132 views

Could a spacecraft be propelled by a 180 degree deflection of two charged particle beams?

I am wondering if the electrostatic deflection of two charged particle beams could create enough thrust, via the Lorentz Force, to propel a spacecraft. Please reference the picture below. This ...
0
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2answers
137 views

How to get experiments to space?

How would a person get an experiment done in space? What is the chain of command on something like that? I would like to drop some inflated balloons from space to reenter the atmosphere to see which ...
0
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2answers
132 views

Why are exhaust nozzles in space shaped the way they are? [duplicate]

Why are nozzles in space shaped like a cone and not like a tube ensuring all the exhaust is directed strait?
1
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2answers
338 views

How does the speed and volume of particles differ in producing thrust in space?

Does a slower detonation velocity push a ship more the same way explosives with a slower detonation velocity moves dirt better? At the same rate does slower particles produce more thrust from a ...
20
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3answers
4k views

How best to maneuver inside a large room within a space station using only arm and leg motion?

Imagine the following thought experiment: An astronaut is inside an extremely large room within a space station. Suppose that she, for whatever reason, is initially at a zero velocity with respect ...
2
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0answers
87 views

Are 2 satellites joined better than 2 apart?

Could new satellites be designed to intercept other older functioning artificial satellites or space junk already in orbit to add weight to the new satellite in order to last longer in orbit?
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0answers
45 views

Apply forces such that a satellite reaches a given point in space

I'd like to find out a strategy for solving the following simplified problem. A small spherical craft at $t=0$ has a position and velocity vectors $\mathbf{x_0}, \mathbf{v_0}$ in a zero gravity ...
2
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2answers
120 views

Solid hydrogen hybrid motor engine for launch?

Would hydrogen unlike water in a solid state take less space or be more stable? How would a rocket work using a block of melting solid hydrogen instead of liquid hydrogen? Has and could any kind of ...
5
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2answers
226 views

How does the thin gold film in the glass of spacesuit helmets block thermal IR but transmit visible? What's the property?

Comments below this answer suggest that there is a thin gold coating on the glass of spacesuit helmets that blocks thermal IR (say roughly about 10 to 30 microns) but is mostly transparent to visible ...
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0answers
61 views

Are there any advantages to being a smaller spacecraft for reentry?

Could a ship drop its cargo or shed weight before reentry to lessen the strain on the ship during reentry? Would a ship breaking down to smaller parts before reentry have any advantages over being one ...
1
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1answer
133 views

What liquids last the longest in space?

I am trying to find something that is somewhat stable as a liquid in space. What happens to various liquid elements and compounds in a vacuum? Is there a list or table of the effects of local space ...
4
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1answer
200 views

Could a ball of water stay in orbit?

Could a water bubble (spherical occlusion of water in air or vacuum) similar to the one in the picture below remain in Earth orbit without evaporating, dispersing, or disintegrating? Assume the orbit ...
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3answers
245 views

Could a bottle rocket be up scaled to achieve orbit?

Could you construct an orbital stick stabilized rocket, by scaling up a firework?
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1answer
140 views

Would I be able to do a “slosh test” to see if a container is having liquid, in microgravity?

Suppose I had two large containers with 1 cubic meter size. The containers are identical on the outside. The containers are floating in microgravity very close to my space ship. One was empty but ...
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0answers
28 views

Converting Discharge Voltage to Temperature? Hall Effect Thruster Calculation

Trying to follow a Hall Effect Thruster design process given in this video: Hall Effect Thruster Design Video In 25:59, there's a calculation in which the presenter takes discharge voltage and ...
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0answers
102 views

Would a self-winding watch work in space without gravity?

Could a watch that winds itself with a pendulum work in space with no gravity? Could a pendulum or the self winding part be modified to work off the movements of the wrist in a microgravity ...
4
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1answer
284 views

How would gravity/acceleration be perceived by a human orbiting Earth at sea level?

I understand the impracticalities of this concept, but humor the 'what-ifs.' Ignoring physical obstacles and the effects of atmospheric fluctuations affecting the trajectory. Say it is possible to ...
1
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1answer
97 views

Ideal shape for a long, skinny reaction mass for LEO to cis-lunar and beyond? (a “space rail gun”)

@Ingolifs' answer got me procrastinating thinking further. What you're asking about is a mass driver space station in low earth orbit that a payload or ship launched from earth can dock with, and ...
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2answers
241 views

Can it be calculated that near the Kármán line the lifting force equals the centrifugal force?

According to Wikipedia about the Kármán line: In the final chapter of his autobiography Kármán adresses the issue of the edge of outer space: ...or 24 miles up. At this altitude and speed, ...
13
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1answer
2k views

Largest radius sphere with Earth's surface gravity on which you could jump at escape velocity? Bigger than B612?

In the book Le Petit Prince by "French aristocrat, writer, poet, and pioneering aviator Antoine de Saint-Exupéry" the main character lives on an extremely tiny asteroid with the name B612. It is this "...
11
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2answers
4k views

Could a human jump off Mimas without return?

A similar question has already been asked on dwarf planet Ceres: Could a Human reach escape velocity by jumping from the surface of Ceres (a dwarf planet)? Ceres has 2.9% of Earth's gravity. Saturn's ...
3
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0answers
196 views

Chinese find material to make space elevator. How much will the cable weigh?

The article China has strongest fibre that can haul 160 elephants – and a space elevator? came out today in the SCMP, and I would like to find out how much the cable would weigh. But I'm not sure if ...
4
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2answers
628 views

Could a satellite in LEO “pump” or change mass distribution to gain forward momentum?

Similar to pumping your feet on a child's swing can a satellite run up and down a pole to produce a forward momentum? Red dots is the satellite's position running up and down the pole on an ...
5
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2answers
469 views

From the General Thrust Equation towards Tsiolkovsky, how to explain dropping these terms along the way?

The NASA Glen Research Center tutorial page Rocket Thrust Equation links to the General Thrust Equation page which starts with: Which transcribes into MathJax as: $ \ \ \ F = \dot{m}_\mathrm e ...
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2answers
484 views

Is the definition of the Kármán line from Wikipedia right? [closed]

Edit: this question is about making clear that the Wikipedia's article about the Kármán line is an interpretation, not the definition ! Why not consider the Kármán line as a curved boundary that ...
0
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1answer
180 views

Analytical approximations for the shapes of these plots of ISP vs nozzle diameter? (Raptor engine)

A comment on the currently unanswered question Is there an authoritative catalog for rocket launch identifiers? led me to this Github page which links to r/spacexlounge on which currently appears a ...
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0answers
57 views

How to make a orbital launch tube work?

Normal rockets would not work in a pressurized tube, but could a stage be made for the diagonal launch tube to save fuel and weight? Can the bottom stage be nuclear powered? Unlike the piston launch ...
6
votes
1answer
427 views

Could I use a satellite as a vehicle for delivering airborne leaflets?

Assuming I have a satellite in a decaying orbit, could I gently release leaflets from my satellite so they were on a near-identical sub-orbital trajectory and have them touch-down safely on the ground ...
4
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2answers
209 views

What exactly means universal variable x and z?

I have been studying by myself Orbital Mechanics, and when solving the Lambert Problem, it's common to use the universal variable approach. I understand the algorithm, but I haven't found any book ...
3
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1answer
163 views

When a Saturn V reaches max Q, what fraction of the lengthwise structural load is due to drag rather than acceleration?

Ignoring all other structural loads besides the lengthwise compression of the rocket. This is useful to know when theorizing about whether high altitude launches (e.g. from airplanes) could ...
3
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1answer
164 views

What causes Hyabusa-2's close-up images of Ryugu to be dark in the corners?

The NYTimes' article Hayabusa2 Prepares to Drop Rovers on Asteroid Ryugu says Sept. 19 Rock Hoppers Hayabusa2 is preparing to deploy two small rovers this week, each about 7 inches wide. Ryugu’...
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1answer
131 views

How can articulated spacecraft components increase the risk of gimbal lock?

This answer has got me baffled. In theory, yes. In practice, no. The problem is gimbal lock... There seems to be some risk of inducing gimbal lock if a spacecraft component of sufficient mass is ...