Questions tagged [physics]

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

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12 votes
4 answers
1k 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 ...
1 vote
1 answer
299 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 ...
3 votes
1 answer
129 views

Satellite’s Position and Path on 2D Map

When the ISS orbit the Earth, its path traced on a 2D Mercator Earth Map is similar to a sinusoidal wave. I am wondering is there any way to determine the trig function of the wave, knowing the ...
1 vote
0 answers
123 views

Ion propulsion system

Good evening. Is there a formulae to calculate how much lift an ion propulsion system would create on earth, given factors like voltage, load, etcetera? Just a mathematical formulae. That is all I ask ...
2 votes
1 answer
125 views

How to calculate catalyst bed geometry (length/radius) for a monopropellant thruster?

Catalyst design is central to the development of monopropellant thrusters and hence, ignoring its importance, as I have realised, is not very good practice. My question is if the mass flow rate, bed ...
3 votes
2 answers
124 views

How much solar radiation hits a spacecraft in transit to Mars?

How can I solve for the amount of radiation that hits a Mars transit vehicle, in transit? What formulas should I use? I am mostly focused on solar radiation.
18 votes
7 answers
4k views

What is measured with g-forces?

When sitting at rest, a typical "g-meter" shows a value of one, however the meter is not accelerating. In orbit, it shows zero, but is under constant acceleration. The actual force of ...
9 votes
4 answers
784 views

Vehicle liquids freeze on the Moon -- how has this problem been solved?

What methods keep the internal liquids on lunar rovers from freezing? I understand that temperatures on the Moon are extremely low, way past freezing, especially in places where the Sun does not shine,...
48 votes
6 answers
10k views

Can/should you swim in zero G?

Inspired by Are there types of animals that can't make the trip to space? (physiologically) and related to but not a duplicate of Can you swim in space? Swimming on the Moon / in low gravity looks ...
12 votes
4 answers
6k views

Accelerometer in space

If my understanding of the General Theory of Relativity is correct, according to the Equivalence Principle, forces due to gravity and acceleration are indistinguishable. If that's the case, then an ...
9 votes
1 answer
471 views

Propagation of pressure waves in low Earth orbit

So in a Wikipedia article about space debris I read that: At higher altitudes, where air drag is less significant, orbital decay takes longer. Slight atmospheric drag, lunar perturbations, Earth's ...
6 votes
2 answers
249 views

Does knocking on walls produce a different sound when adjacent to a vacuum?

If I was to knock on a wall or door between a pressurised room and a vacuum, would that sound different from knocking on a wall or door of the same material between two pressurised rooms? If not, ...
7 votes
6 answers
5k views

Could a spacecraft theoretically fly a smooth, curved arc of a turn in space like an aircraft?

I understand there in no air is space which is what allows an aircraft to fly a curved flight path. This is strictly a theoretical question given today's technology. Here are the conditions: There ...
8 votes
2 answers
466 views

Using asteroids as propellant source

If we could capture an asteroid or meteor, can we use it as a vehicle for space travel? From what I understand, propulsion is a result of mass flow, so we could use a rail gun configuration to propel ...
5 votes
1 answer
5k views

What is the time dilation between Mars and Earth resulting from the mass difference?

I am not sure I understand the time dilation correctly, but if mass has direct impact on time, then let's consider cosmological event - one orbit of planet Earth around the Sun. This event will person ...
0 votes
3 answers
888 views

Why don't ion thrusters use exothermic reactions directly to ionize the gas and heat up the plasma?

Ion thrusters require a lot of energy because of their high exhaust velocities. But why can't they just pump a mixture of hydrogen and xenon into the chamber, mix it with oxygen and burn it? Doesn't ...
4 votes
1 answer
408 views

Inconsistencies in calculating exhaust velocity

I'm quite sure this is either a small or just plain stupid mistake but my anxiety is getting the better of me. when calculating exhaust velocity this is the equation used: however I keep getting ...
8 votes
0 answers
205 views

Roughly, 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 ...
7 votes
5 answers
2k views

Gravitational field of the Moon and Earth

Is there any method to find a point or plane in space where the gravitational field of the Moon and Earth are the same? And if so, what happens to a spacecraft if it passes through that point or ...
4 votes
1 answer
259 views

H2 and CO2 ventilated outboard of the ISS, could become ice flakes in the extreme temperatures outside the ISS?

Outside the ISS in the orbital night, the temperature can reach -250 degrees Fahrenheit (-157 degrees Celsius). The ECLSS (Environmental Control System and Life Support System), more specifically the ...
1 vote
3 answers
352 views

What is the maximum orbital speed beyond which the orbit around any large object in the Solar System becomes unstable?

How fast is too fast to stay in orbit around any particular large body in the Solar System?
8 votes
2 answers
607 views

Is engine thrust noticeably increased near the ground?

I know next to nothing about rocketry and space flight. I assume that the majority of the force generated by a rocket's engine is simply the result of throwing gasses out of the bottom very fast, and ...
1 vote
1 answer
261 views

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 ...
4 votes
1 answer
201 views

Could a laser ablation-based propulsion system really accelerate an object to 0.001 c?

Comments below this answer suggest that a laser ablation-based propulsion system, where the laser is separate from the object to be accelerated, could accelerate an object to about $\frac{1}{1000}$ of ...
2 votes
1 answer
309 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 ...
3 votes
5 answers
611 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,...
2 votes
0 answers
52 views

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 ...
12 votes
1 answer
315 views

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 ...
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) ...
3 votes
1 answer
407 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 ...
3 votes
1 answer
219 views

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 ...
2 votes
1 answer
230 views

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 ...
3 votes
1 answer
192 views

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 ...
2 votes
1 answer
87 views

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 ...
18 votes
2 answers
2k views

Is the Flyby Anomaly still a thing?

The Flyby Anomaly is a name given to an unexplained, unexpected difference between the best theoretical calculation of a change in several different spacecraft's velocities due to flyby (Gravity ...
0 votes
0 answers
77 views

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 ...
5 votes
2 answers
536 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 ...
2 votes
1 answer
91 views

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 ...
-1 votes
1 answer
112 views

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 ...
4 votes
1 answer
202 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 ...
3 votes
0 answers
82 views

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 ...
4 votes
4 answers
8k views

How do jetpacks work in space?

I've seen in some videos of astronauts that they used to use a jetpack type system to maneuver in the vacuum of space around the ISS and other satellites using pressurized gas. From Wikipedia ...
3 votes
0 answers
322 views

Have there been any Foucault pendulum demonstrations beyond Earth?

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 ...
3 votes
0 answers
116 views

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 ...
6 votes
3 answers
334 views

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 ...
2 votes
2 answers
244 views

How, and How Well will Juno measure the effects of frame dragging? (GR effect due to Jupiter's mass & rotation)

This answer links to Spaceflight 101's One Week to Jupiter – NASA’s Juno Spacecraft en-route to Gas Giant after five-year Journey which says Also, Juno will put Einstein’s General Theory of ...
4 votes
2 answers
406 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: $$\...
11 votes
1 answer
292 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 ...
6 votes
2 answers
851 views

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 ...
1 vote
0 answers
68 views

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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