Questions tagged [physics]
How physics applies to a particular activity in space or to getting to space.
238
questions
2
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1answer
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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:
(...
5
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1answer
287 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 ...
3
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0answers
67 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 ...
2
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0answers
110 views
What is electron precipitation? Why would STEVE care?
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 which ...
13
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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 ...
3
votes
1answer
204 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 ...
1
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0answers
71 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 ...
2
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0answers
38 views
Have there been any square 4U (2x2) cubesats?
How much did each MarCO 6U cubesat weigh? suggests that the density of a MarCO 6U cubesat might be as low as 0.75 g/cm^3 whereas I think they are usually about twice that.
That led me to speculate ...
0
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1answer
165 views
Did the Perseverance rover's Atlas 5 really “leap off the pad”? If so, was it because the payload is tiny, or because it's going to Mars?
Spaceflight Now's ULA’s Atlas 5 is NASA’s go-to rocket for nuclear-powered space probes quotes Tory Bruno, president and CEO of United Launch Alliance:
“This rocket is going to leap off the pad with ...
11
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1answer
1k views
Now that Perseverance is “hot” (RTG in place) and before it gets to deep space, how will it stay cool?
As soon as they are assembled MMRTGs continuously produce about 2,000 watts of heat energy. That dips only slightly when they are connected to a load and producing electrical power (about 125 watts ...
5
votes
1answer
115 views
Is there any possible reason to direct the electron gun specifically towards the ion trail behind an ion thruster?
This answer to Neutralization of ions in the ion thruster quotes the introduction to Wikipedia's Ion thruster:
Temporarily stored electrons are finally reinjected by a neutralizer in the cloud of ...
1
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0answers
57 views
Can Chemical Engineer work on something related to space?
I am an undergraduate student (scientific section) living in Qatar. I have a big interest in astronomy and astrophysics and have participated in the IOAA (International Olympiad on Astronomy and ...
0
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0answers
97 views
Roughly express how much of our Moon's apparent libration amplitude seen from the Geocenter is due to different effects?
My understanding is that when tidal locking of a body first happens it transitions from a state where the average rotation period is faster than the orbital period to a state where they are the same ...
4
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3answers
1k views
If a car or train freely drove on flat terrain on the Moon, would it eventually be stopped by something?
If you start an Apollo LRV on the Moon and let it go on flat terrain (with motor off), would it be stopped by ground friction eventually, or doesn't that stop a car? Same question for a train on rails ...
5
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1answer
775 views
Would a sniper bullet fired on Ceres reach orbital or even escape velocity?
What would happen if you fired a sniper bullet horizontally from the top of Ahuna Mons, the highest mountain of Ceres? Once I read somewhere that if you fired a bullet on the Moon in the correct angle,...
4
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0answers
134 views
Can an electrostatic shield provide protection from the Van Allen belt?
Would an electrostatic shield provide enough protection for a crewed space craft to survive in the Van Allen belt for more then an hour?
5
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1answer
105 views
Would there be snow, rain, fog or clouds in a deep, sealed, subsurface cavern on the Moon if water were present?
The question Most efficient method of storing energy with water on the moon? proposes a several hundred meeter tall subsurface cavern on the Moon. I added the following comment to an answer:
I keep ...
1
vote
1answer
84 views
Interactions between rocket exhaust and radio communications?
Rocket exhaust is bright in visible light, we can still see through it but when there's hot, glowing soot it's so bright that we think it's opaque, but it's not. See answers to How does the camera ...
2
votes
1answer
64 views
Where can I learn to calculate the physics of an ion thruster?
I am trying to build an ion thruster, but I don’t know where to start learning the actual numbers behind one. I know how they work on a basic level, but not much more.
Basically I want to be able to ...
1
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0answers
110 views
Kepler prediction problem, fundamentals of astrodynamics
I needed help with problem 4.3 of Fundamentals of Astrodynamics by Roger R. Bate, Donald D. Mueller, Jerry E. White (dover, archive.org)
Given that $r_0 = (I+j)$ and $v_0 = 2k$ find $r$ and $v$ for ...
7
votes
1answer
181 views
With a 10% increase in Earth's mass, would the Karman line move up or down, and by how much?
This is an exercise to better understand the basic physics and math behind scale height and the Karman line. It was inspired by this answer to Why is FAI considering lowering the Karman Line to 80km? (...
3
votes
3answers
202 views
What (if anything) limits the efficiency of a rocket engine?
Humans have developed lots of rockets. I observe that in most cases to increase the payload capacity we just increase the amount of fuel.
Is it not possible to exponentially increase the efficiency ...
1
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0answers
35 views
Would the Yarkovsky effect ever be faster than a solar sail from a 1 AU orbit to the Sun?
Previously I'd mistakenly asked Would the Poynting–Robertson effect ever be faster than a solar sail from a 1 AU orbit to the Sun? when I'd meant to ask about the Yarkovsky effect which can be much ...
0
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1answer
58 views
Could a skyhook be used to change a satelites orbit from polar to equitorial?
Could this work if the skyhook also had ion engines to maintain its orbit or would the cable just snap?
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1answer
152 views
Can I do “car surfing” on empty space? [closed]
Suppose a Car/Van is launched into space with you. Suppose you would like to do 'Surf' on the car roof like Marty in "Teen Wolf". On the earth, if car accelerate up to 30-50 or 100 mph will make Marty ...
3
votes
1answer
85 views
Why might krypton have a lower utilization fraction than xenon for ion propulsion, and what can be done to improve it?
A comment below Why will Starlink satellites use krypton instead of xenon for electric propulsion? links to the 2011 preprint A Performance Comparison of Xenon and KryptonPropellant on an SPT-100 Hall ...
5
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0answers
168 views
What exactly is a solar gravity well manouver and in what cases would it be helpful?
In this answer to the gedankenexperiment question With current state of technology if we wanted how long would it take for newly launched probe to overtake Voyagers? I've seen the term "solar gravity ...
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0answers
71 views
Is centripetal acceleration around an ellipse with constant tangential velocity always pointed towards the center of the ellipse? [closed]
I've tried to find answers online but surprisingly couldn't find any.
8
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1answer
428 views
What do the shaded vertical lines in the animation of Gravity assists of space probes, mean?
Example Animations from Wikipedia —
https://en.wikipedia.org/wiki/Gravity_assist#/media/File:Animation_of_Voyager_1_trajectory.gif
https://en.wikipedia.org/wiki/File:...
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3answers
135 views
Would the trajectory of a comet be altered by attaching a parachute to it?
I am curious to know if the trajectory of a comet that is on a collision course for Earth could be altered by simply attaching a parachute to it. The parachute interacting with the comet's tail should ...
0
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1answer
120 views
Would the Poynting–Robertson effect ever be faster than a solar sail from a 1 AU orbit to the Sun?
In this answer to Do you need 0 km/s velocity to crash into the sun? I mention solar sails for retrograde thrust and the Poynting–Robertson as two ways an object could ever-so-slowly spiral into the ...
21
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7answers
8k views
Do you need 0 km/s velocity to crash into the sun?
I was reading a popular thread about the delta-v required to escape the solar system compared to the delta-v required to crash into the sun. I get it: the earth itself already has a high speed (29.7km/...
2
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2answers
143 views
Are there some three-body orbits that can't be escaped? Can we know without propagating forever?
update: Searching for "choreographies" I found this Physics SE question which is related but different because it asks only if periodic solutions can be proven to be periodic numerically and my ...
7
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3answers
641 views
Why does this formula say rocket efficiency depends on velocity?
Wikipedia gives the following equation for the efficiency $\eta_p$ of an engine here:
$$\eta_p= \frac {2\, (\frac {v} {v_e})} {1 + ( \frac {v} {v_e} )^2 }$$
where $v$ is the rocket speed and $v_e$ ...
2
votes
0answers
88 views
What was Steve? Is it called something else now?
"Steve" was a temporary name for a space phenomenon above the Earth. Since then it's likely much work as been done and a more permanent name chosen. So I'd like to ask what Steve really was/is, and if ...
4
votes
1answer
98 views
How to find the moment of inertia of the Viking capsule?
I have an assignment where I have to simulate a Mars re-entry using the Viking capsule. I have finished it but now I want to go further and try to make my capsule glide. For this I need to enslave the ...
9
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5answers
1k views
Why do space rockets not start from an angle? Why go straight up? [duplicate]
I know that they used to have this idea, back in the day, of a "space gun" to fire somebody into space, and I understand why that was not safe or practical/feasible.
However, once they had come up ...
1
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1answer
56 views
Can anyone recommend a good online calculator for travel time within the solar system?
I'm trying to figure out how long it would take to travel to saturn with a skyhook launch from moon orbit.
1
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1answer
44 views
What exactly is eLISA, how will it benefit from LISA Pathfinder and how large will it be?
This answer to What do the gravitational wave findings mean for Evolved Laser Interferometer Space Antenna satellite says:
Given that the LPF is already launched, I doubt that it will be cancelled. ...
0
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1answer
148 views
For a DAWN-like solar-electric deep space mission, would using propellant particles much heavier than xenon atoms be beneficial?
For deep space missions using ion propulsion that are power-limited, this answer explains that a large mass/charge ratio ($m/q$) species is desirable. The solar-electric propulsion system used by the ...
6
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2answers
181 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 could ...
2
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0answers
48 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 ...
0
votes
1answer
74 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 ...
1
vote
1answer
280 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
votes
1answer
276 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, ...
3
votes
1answer
97 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
votes
1answer
299 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
209 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.
0
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3answers
334 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 ...
1
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1answer
178 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 ...
