Questions tagged [rocket-science]

Colloquially referred to as one of the hardest professions, rocket science is actually a common name for spacecraft/space-systems engineering. However, one can also generalize this to include all forms of rocketry, including rockets that are not capable of space travel.

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How to find the length of a travel between planets using the Hohmann Transfer?

I am trying to figure out how long it would take to get from one planet to another. This is for a worldbuilding project of mine. I would put my question on the Worldbuilding Stack Exchange but I ...
Martamo's user avatar
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What convention, if any, exists regarding the algebraic signs of constants and variables such as in this exercise?

This problem is from the original exercise set to accompany The Feynman Lecture on Physics. I am absolutely not asking how to find the solution. I am asking if there is some convention regarding the ...
Steven Thomas Hatton's user avatar
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Breakthrough Starshot project [closed]

How do I calculate the acceleration and maximum speed of a starship (from the Breakthrough Starshot project) that has a mass of 50 grams and a sail with a cross section of 4 m^2 and is hit by a laser ...
ani's user avatar
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Relativistic Rocket Equation Derivation

Could somebody help me derive this equation? $$\frac{\mathrm{d}M}{M}=-\frac{\mathrm{d}v(1-v_\mathrm{ex}\frac{v}{c^2})}{(1-\frac{v^2}{c^2})(-v_\mathrm{ex}\frac{v^2}{c^2}+(1-a)v+av_\mathrm{ex})} $$ This ...
spencj95's user avatar
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Why are missiles rotating in space?

Watching the Starship launch today I noticed it's actually doing some full rotations. Why isn't it controlled? and why does it happen? I have read that it's the same for military missiles too
Dor's user avatar
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Why are NASA etc so good at hitting tiny targets in tiny time windows?

NASA have a tendency to arrive at targets that are so far away, within seconds of ETA, and statements like " it's like throwing an object from New York and having it hit a particular key on a ...
Rabbi Kaii's user avatar
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3 answers
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How is Newton's 3rd law applied in rocket propulsion?

I'm really wanting to get into physics more and I've had this question for a while. I do know a bit about rocketry as I think it's pretty cool but I'm still struggling to understand how Newton's 3rd ...
StrangeJmaster's user avatar
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Rocket attached to a pendulum. How is energy conserved?

I'm trying to wrap my head around a conceptual problem involving a simple pendulum with a rocket attached to its mass. Imagine the rocket expels gas to provide a tangential thrust force. However, the ...
Eduardo González's user avatar
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Okay, I know the risks. ( Amateur Rocket.) [closed]

I am currently attending a school for electrical science. A small group of students and our instructor are attempting group project to build a liquid fuel rocket. (I know it is a bit out of the scope ...
TylerTheSparky's user avatar
1 vote
3 answers
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Newton's 3rd law, force on a rocket

Please clear up this confusion for me: I just watched the video on khan academy @7:30 where the guy explains newton's 3rd law. He explains that for a box on a table, the forces equal out so it's at ...
skybee's user avatar
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How far can we go in space?

I'm a noob in physics & math, so I'm just looking for a scientific answer for a small fiction project. My question is : How far can we realistically go in space, if we managed to "use" ...
Django's user avatar
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Is it possible to build electrical space engine based on Electromagnetic induction

Electromagnetic induction means magnet convert it momentum to an electrical current. So I wonder if it possible to use this phenomeno for making an enigne which will accelerate a magnet And the ...
daniel's user avatar
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Are there any equations for the mass of fuel (ejected at some velocity) required to propel a rocket of some mass some distance through gravity? [closed]

Either through constant gravity, more simply, or through the changing gravitational field, more accurately. This appears to be a fully determined system, although I found no analytic solutions for ...
WondrousConfusion's user avatar
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6 answers
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Why does my perpetual CMBR rocket ship not work? Why does the CMBR have infinite energy?

Take a spaceship and accelerate it to 99.947% the speed of light, effectively blueshifting the Cosmic Microwave Background (CMB) from 1.9mm to 500nm, turning the CMB to a harvestable source of energy. ...
Travis R's user avatar
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Time taken for a rocket to travel upwards [closed]

My doubt is a rather silly, simple one but i cant seem to understand what's wrong. Let's assume a rocket is moving up with a constant acceleration of a, is moving strictly vertically(no gravity turns, ...
Star Gazer's user avatar
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Time taken for a rocket to reach a height [closed]

My doubt is a rather silly, simple one but i cant seem to understand what's wrong. Let's assume a rocket is moving up with a constant acceleration of $a$, is moving strictly vertically(no gravity ...
Star Gazer's user avatar
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Efficiency Loss of Rocket Engine in a Vacuum Due to Underexpansion

A rocket engine in the vacuum will experience efficiency loss due to under-expansion in which the pressure of the exhaust is greater than the ambient pressure, which in a vacuum is near zero. How ...
Nomadicus's user avatar
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Rocket Exhaust Ground Impact: Exhaust Gas Velocity vs. Pressure

Thanks for anyone that can help. Say we have a rocket engine in the vacuum of space with exhaust velocity of 2,000m/s or more, but low pressure exiting nozzle, say 1-2psi. A wider nozzle engineered ...
Nomadicus's user avatar
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1 answer
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Is it possible to attain (near) light speed in space?

As there is no drag in space/vacuum, is it possible to actually send a probe with enough fuel to have it achieve the speed of light or a value very near to it? Since there are not many significant ...
Mel's user avatar
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Rocket-assisted drag cancellation in artillery shell

The main limit on artillery range is drag. Hence for the same muzzle velocity, the WWII 800mm Schwerer supergun had twice the range of the modern 155mm M777 gun, because the super shell had a much ...
Abdullah is not an Amalekite's user avatar
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Physics of Landing a Rocket on a Specific Location [closed]

I have been working on a rocket model for the past year, and I have a question about the landing phase of the rocket flight. How do rockets, such as those from SpaceX, land on a specific location ...
Cheyon Vijayakumar's user avatar
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1 answer
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Fluid dynamics of a balloon

This is a question which might not seem relevant to physics, but I was always curious if the shape of the balloon were to be not the shape that we all know of, when we release the tip will air flow ...
Aurora Borealis's user avatar
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Total energy of a rocket launch

I'm wondering how the total energy of a combined Earth-rocket system is conserved in a rocket launch? Before launch, kinetic and gravitational potential energy of the rocket are 0. It then launches, ...
Steven H's user avatar
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3 answers
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Would the acceleration of a model rocket be constant for a constant thrust or not?

The question is this: I believe the answer is A as the gravitational field strength becomes lower for larger distances of the object from the earth, but the model answer as as below: Are they ...
RedP's user avatar
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What is the exhaust pressure of the Saturn V on the Apollo 11? [closed]

I am trying to write some code to simulate rocket launches, and I am doing a proof of concept using the Apollo 11 as a model, to fill my values. When calculating thrust I am using the equation: $$F = ...
owinius's user avatar
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What is $p_0$ in the rocket thrust equation $F = \dot m * V_e + (p_e - p_0) * A_e $ and how do I calculate it?

I am doing a computer science project on a rocket simulation and i am using the thrust equation $$F = \dot m * V_e + (p_e - p_0) * A_e $$ however I cant find any articles that clearly explain what the ...
owinius's user avatar
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What is the practical speed limit for rail-gun orbital launches due to heat-generating wind resistance?

I was looking into the practicality of rail-gun technology to achieve orbital launches (As promoted by the answers at What is the possibility of a railgun assisted orbital launch? ), but found that ...
Astar Wstar's user avatar
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Does rocket increase power in own reference frame as speed increase? [duplicate]

In reference frame moving with rocket exhaust speed is constant, so what is with power as speed increase? If power is const. in this frame, how is possible that at frame at rest power rise? Shouldn't ...
user707264's user avatar
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Where does Energy get lost in the Rocket Ship propulsion vs "direct acceleration" scenario? [closed]

The scenario is as follows. In a hypothetical future drive I spend energy E to accelerate a mass of propellant m to velocity v (e.g., plasma state propellant in the very powerful circular accelerator),...
J Ho's user avatar
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Why rocket equation? [closed]

while deriving rocket equation we find change in momentum of rocket and this is the result: $$Δp=MΔV+Ve ΔM$$ from here we divide this by time to calculate force and since no external force(freespace) ...
Curious kid's user avatar
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Struggling to find the data of any rocket during a hyperbolic trajectory

I am trying to represent the hyperbolic trajectory of a rocket to mars, but i am slightly struggling to find a few values i need for it: The eccentricity of the hyperbola required to go to mars, the ...
questioner123's user avatar
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1 answer
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Why is the distance negative in a kinematic equations? [closed]

A rocket with zero initial speed takes off at a speed of 100 meters per second, assuming that gravity is 10 meters per second squared, determine the distance travelled: $$ v_f^2 = v_i^2 + 2ay $$ ...
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Propulsion of a spacecraft [closed]

If a craft is positioned at the strongest point of the earth's electromagnetic field being either positive or negative and the craft activates the same field it would repel each other would it create ...
Pravesh Maharaj's user avatar
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1 answer
284 views

How to calculate the energy in a hyperbolic orbit?

I'm recently reading a book about rocket science which involved orbital mechanics. I know that in an elliptical orbit, the energy $ E=-\frac{GMm}{2a}$, and therefore can get the vis-viva equation: $ ...
Jason Jia's user avatar
2 votes
1 answer
109 views

Why is $F = ma$ at an instant, in variable mass systems? [duplicate]

While studying systems with varying mass, I have come across examples using thrust, and summing all the forces on the system including thrust, as being equal to $F_{net} = M\bar{a}$. (My system's ...
Science done right's user avatar
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2 answers
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Can one build a nuclear jet engine based on alpha emitter for small space satellite?

Let assume a metal tube open on one side having alpha emitter material on the other blocked side. Since alpha particles are blocked by the metal they will be emitted only through the open side and ...
Amos Fenigstein's user avatar
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1 answer
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Why are the trajectories velocity specific? [duplicate]

Consider projecting a particle from or above the earth surface (at a distance $r$ from center of earth) with velocity $v$. My teacher told me that if $v<v_0$ particle will follow elliptical path, $...
Chesx's user avatar
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Could a cylinder spacecraft (similar to an O'Neill cylinder) rotate indefinitely in the vacuum of space? [closed]

As oppose to a cylinder in two pieces rotating against each other, as in O'Neill's cylinder, what if the cylinder were all one piece and an external thrust, like rockets, set the cylinder in motion, ...
Ben Warner's user avatar
4 votes
7 answers
2k views

Are all conservation of momentum scenarios simply particles bouncing on walls? [duplicate]

All explanations of jet propulsion that I've seen are formulated as "due to conservation of momentum, air with momentum coming out of one end means the rocket must gain momentum in the opposing ...
one two's user avatar
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Rocket propulsion energy efficiency

What ratio of final to initial mass of a rocket to achieves the highest energy efficiency - the highest ratio of final mass kinetic energy to chemical energy expended? And more generally the relation ...
Dylan Menzies's user avatar
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0 answers
20 views

How is the specific impulse of a gridded ion thruster derived?

How is the specific impulse of a gridded ion thruster derived? I've searched and got a variety of answers and Bard gives a different answer each time I ask it. Too the best that I can reckon it's: 1/9....
Richard's user avatar
1 vote
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What are the light emissions from an ion engine?

Consider an ion thruster like a DS4G (Dual-Stage 4 Grid) thruster. Gas is released, ionized, and accelerated. Assume it's in a vacuum, be it a chamber or space. Also assume the propellant is Xenon. ...
cthon's user avatar
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Can an ion thruster work without applied voltage?

In this image, power is used to apply voltage to the charged grids. But if no voltage is applied, would ions still be accelerated by Coulomb forces to create thrust? If not, why?
Beom's user avatar
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Why is hydrogen considered the most efficient rocket fuel and how it relates to the concept of specific impulse (ISP)?

Why is hydrogen considered the most efficient fuel? I mean I know it is very light and can be accelerated very fast, but can’t you use a denser fuel but throw it at a slower speed bunch, and it’ll ...
acornator's user avatar
-3 votes
2 answers
98 views

What happens to the velocity of a photonic rocket as it approaches $c$? [closed]

Imagine you have a photonic rocket (powered by something like antimatter). If it accelerates at a constant $9.8m/s^2$, it'll reach a velocity of $c$, the speed of light, in around 350 days. What ...
xyz's user avatar
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Do EM waves carry momentum and if they do can it be used to generate thrust? [duplicate]

I read EM waves carry momentum and can exert pressure, if this is the case can ejecting them be used to generate thrust? Radiation pressure is cited as a real thing but I read about the EM drive and ...
FourierFlux's user avatar
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3 answers
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How does a spaceship respond to a sling?

If you are in a spaceship and you spin a sling with a rock in it, does the spaceship rotate in the opposite direction as the sling with the same angular, kinetic energy as the sling? If the sling is ...
Dale's user avatar
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Is the force of a gas exiting through a rocket equal to the force of the rocket?

While I was watching some videos about rocket and its engines, I saw that the principle behind it is Newton's Third Law, because while the gas is exhausted from the rocket it has a reaction force ...
Marcos Victor's user avatar
1 vote
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Thrust of accelerating vs stationary water bottle rocket

When a water bottle rocket accelerates it might leave some water behind, as is (exaggeratedly) shown in Fig 2. The smaller the nozzle the less water is left behind, but let's say the nozzle is rather ...
HolmanDev's user avatar
3 votes
3 answers
498 views

Relationship between fuel consumption and kinetic energy increase

The spacecraft with the same physical properties is moving in space. Let's assume that there are no resistance in space. A stationary observer observes a spacecraft whose speed varies from 100 m/s to ...
NOH WHIREA's user avatar

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