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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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Nuclear Propulsion

I am watching a video on nuclear rocket engines, specifically the Nerva engine. It has a propulsion efficiency of 750-800 Isp versus chemical rockets which are only 350-400 Isp. The follow on NRX ...
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Model Rocket Stabilisation

I am designing a model rocket and am using 3 B6-4 Engines. Inevitably there will be perturbation of its trajectory by wind and engine/thrust inconsistencies. The way that I currently understand the ...
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Is a rocket engine most efficient when its velocity is equal to the exhaust velocity?

I was reading Dale's answer on this question and from the answer I concluded the following: 1- When the rocket is traveling at a velocity much less than the exhaust speed, most of the chemical energy ...
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Rocket Leaving Earth's Gravitational Field

I stumbled across this seemingly simple question that really stumped me on further thought: A rocket is intended to leave the Earth's gravitational field. The fuel in its main engine is a little ...
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Chemical energy

A physics problem I am solving has a rocket which launches and releases a certain chemical energy $u$. What is chemical energy? How would I incoporate it into the equations of conservation of energy? ...
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Would it be possible to do a “slow” translunar injection, lasting an hour or more

Part of my sci-fi novel takes place on a spaceship with centrifugal pseudogravity (initially at ~1g), designed to make passengers comfortable on a week-long voyage to the moon. With that being said, I ...
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Rocket propulsion equation

The equation $$V_{rel} \frac{dm}{dt} - mg = ma $$ what is the meaning of m in the given equation is it the mass of the rocket and the point with which we are concerned or is it the initial given ...
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Can the pressure term in the general thrust equation be negative?

In the general thrust equation, it looks like the pressure term can be negative if the ambient pressure is greater than the nozzle exit pressure: $$F=\dot m\cdot V_\mathrm e+\left(p_\mathrm e-p_\...
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Is there a minimum range for an Intercontinental Ballistic Missile? [closed]

To be more concrete: Would it be possible to fire a ICBM Minuteman III from Malmstrom Air Force Base in Montana (USA) to hit Helena (the capital of Montana) about a hundred kilometers away? If not, ...
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Lagrangian of Rocket [closed]

While solving equation of rocket motion with Newton's law in 1-d,I pondered to apply Lagrangian method on this. However, I didn't get correct result. Because I can eliminate last 2nd equation using ...
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How do rocket engines work in EMPTY space? [duplicate]

So I just read this and it didn't make any sense It is not necessary for the rocket exhaust to push against anything EXCEPT THE SHIP ITSELF. You see, when the combustion of fuel takes place ...
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Optimal trajectory of rocket with variable specific impulse and constant power

I am trying to derive trajectory of rocket with variable specific impulse and given power of engines $P$ that minimizes the total time. The specific impulse is given as time-variable effective exhaust ...
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How was the equation for a gravitational assist derived?

Im currently writing a paper about a hypothetical probe meant to escape our solar system and I want to analyse how gravitational assists would be beneficial for its mission. I found a website with an ...
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How do ion thrusters create a force against the spacecraft?

I recently saw an old thread, How do reaction engines create a force against the rocket?, get bumped up, and it asks a good question: in a chemical rocket, the fact that the rocket exhaust gets ...
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How do reaction engines create a force against the rocket?

I'm fairly new to physics, so please forgive me if I lack basic understanding. I'm wondering how rocket engines actually work. I know the answer of "actio est reactio", but I feel like this is a ...
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What would happen if I used a jet pack that accelerates at $g$ but always upward?

I'm trying to imagine what would happens if gravity is cancelled. I assume that without air, if the effect of gravity were to disappear I would fly off Earth on a tangential line. But with the air ...
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How does a rocket gimble work?

I'm trying to understand how a rocket Gimble turns a rocket using unbalanced resultant forces . For simplicity lets say a compressed air rocket. If the rocket is straight ahead the escaping gas ...
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Standing waves in raptor rocket engine test

Stopping the video of the recent test of the raptor rocket engine, one can see a standing wave forming in the exhaust gases: https://youtu.be/MAAzbjG_Duc?t=23 I was wondering what might cause a ...
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How this equation happens and what it describes?

I'm having some trouble with Momentum and Impulse, In this equations, Thrust = F = m * a = dp / dt = m * (dv / dt) + v * (dm / dt) How is the, m * (dv / dt) + v * (dm / dt) Happens, and what it ...
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Aerospike Nozzle Geometry

I have searched the site and my search for the results I want yielded 16 results, none of which seemed to be very helpful. I have searched the internet several times but I do not have the knowledge or ...
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I'm travelling near the speed of light. Do I need to brake before using a super-massive black hole to turn around?

I'm taking one of those new fusion drives for a trip to nearby supermassive black hole. At a comfortable 1 G, it'll take me about 7 months of proper time to accelerate to 95% the speed of light. I'm ...
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Does Oberth Effect work in free space or it works only in gravitational field (gravitational well)?

From Wikipedia article about Oberth Effect it is not clear if it works in free space (no gravity, no air, etc). For example, in very far space between 2 galaxies, gravity is almost zero. There are 2 ...
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Why cannot we go in outer space with constant speed?

Sorry if this question is very childish for experts here. This was the question I had in school and years later it has resurfaced. I did some google search but getting the same equations of ...
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Generic Differential Equation for Oberth Effect

In Wikipedia article about Oberth Effect there is an example of calculation in a simple case when the differential equation is not required. In non-English versions of this article (for example, ...
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How can China put artificial moon if they're not in equator?

China plan to put artificial moon. I suppose the moon would have to be geo stationary in orbit. However, a geostationary orbit would be on equator and china is not on equator. So how would it work? ...
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Rocket equation and drag formula

i originally posted this question over at the math section but a guy told me to switch it to here instead. i'm writing an assignment on firework rockets and their trajectory. Now of course im doing ...
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1answer
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Solving the rocket differential equation

I'm trying to derive the rocket equation. I'm pretty sure that the differential equation for the rocket equation is $$v(t)\delta t =\frac{m(t)\delta t }{m(t)} V_e$$ where $v(t)\delta t$ is the ...
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Is it possible to use an accelerator/collider as a space engine? [closed]

I was just trying to get a discussion going about physics that we can already create. I did not realize that I would have to write a paper to ask a simple question. Is it possible to use an ...
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1answer
51 views

Work-Energy Theorem for Non-Constant Mass

"The net work done on an object is equal to its change in kinetic energy." Let's say that a rocket is moving upwards while expelling gas and is thus losing mass. (Non-constant mass) As the object ...
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2answers
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Rocket speed (Is the equation my choose is the correct one and is my (asumption) and calculation is correct with regard to Hawking's sentences

Hawking wrote, Exhaust speed of chemical rockets is 3 kilometer/second. By dropping 30 percent of their mass, they can achieve speed of about 0.5 kilometer per second and then slow down again. ...
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Are there two action-reaction pairs operating in a rocket

I'm confused about the action-reaction pair in a rocket. is it 1 The action of the explosion of gases in the combustion chamber on the rocket, and the reaction of the rocket on the gases, or 2 The ...
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Where does the momentum exchange happen in a rocket? [duplicate]

Where does the momentum exchange happen in a rocket. Is it in the combustion chamber alone?
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How does a rocket obey Newton's third law? [duplicate]

How does a rocket push against its exhaust? Does the reaction come from the rocket nozzle or as a result of the imbalance of forces in the combustion chamber?
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If there is no atmosphere on a planet that is rotating on an axis and a rocket is launched “Straight up” from its surface,

If there is no atmosphere on a planet that is rotating on an axis and a rocket is launched "Straight up" from its surface, won't the rocket still have an angular/orbital velocity because the planet ...
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How is Geo Stationary Rocket placed exactly above the Location after Launch

My Question is bit deeper on the Satellite been put into orbit of GEO . Recently ISRO Launch GSLV Mark 3 to put into GSO . After the Rocket is launched and reached the Perigee ( 190 km ) the ...
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2answers
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Rocket Equation

What formula can be used in order to find the final velocity of a rocket if the time travelled by the rocket, exhaust velocity, initial and final masses of the rocket and the initial acceleration of ...
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Vacuum thrust, and how it is proven

Let’s talk about “Vacuum Thrust”. Simply put, thrust that is exerted in a vacuum. Space is a vaccum correct? So therefore there is no matter is space, it is just empty space. Thrust is measure in ...
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Water rocket height calculations & alculation of the size(diameter) of the nozzle

I'm currently building a water rocket made out of carbon fiber pipes and fabric. Before that I built a simple water rocket made out of plastic bottles with my friend for a science competition. Now I ...
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What is the minimum time required to travel 1 light-year from Earth and turn back? [duplicate]

Suppose I have a very powerful and durable rocket that is able to reach speed of light minus $10^{-1000^{1000^{1000}}}$ in $10^{-1000^{1000^{1000}}}$ milliseconds. Very instant acceleration. I can ...
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Ion optics of a gridded ion thruster

Followup to this question. The holes in the grid of an ion thruster should be thought of as an optical device for ions. As is shown here, ions are focused to the center of the stream. My question is ...
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Hole size in ion thruster's accel-grid v. scoop-grid

In ion thrusters, the scoop grid is charged positively and "scoops" ions from the plasma. The accel grid is charged negatively and placed at some distance to accelerate the ions by the applied voltage....
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Action reaction pair rapidity or time delay

How much rapid is action reaction force ? Suppose i have a rocket of 10kg dry mass and 10kg reactive mass. On launching, 5 kg of reactive mass is burnt. And i get a thrust of 200 N. What will be the ...
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1answer
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Analytic and numerical integration of the rocket equation yield different results [closed]

Background The mass of a rocket as a function of time is: $$ m = m_0 - \dot m t$$ Where $m_0 $ is the initial mass of the rocket and $\dot m$ is the mass flow rate. At a certain time all the fuel has ...
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Need help creating an equation for the time it takes for a rocket to deaccelerate (accounting for fuel mass lost)

I'm doing a Math Internal Assesment for school where I'm trying to create a model for a rocket's suicide burn. I've gotten stuck in one of the equations I need for it. I need to find the time it would ...
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2answers
62 views

Delta-V of Earth to Moon mission using Moon orbit

I have read this article here and it talks about the delta-v cost of travelling to and from the Moon. Importantly it says that getting to an orbit round the Moon, and docking with a space station, and ...
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Why is the work done by a rocket engine greater at higher speeds? [duplicate]

From this comment by orlp: If I strap a rocket booster to a rocket in space and fire it for one second, then the work provided is much higher when the rocket is flying fast compared to when the ...
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2answers
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Sign problem in projectile with drag

So recently, I've been playing around with the variables in projectile motion with drag to see how the trajectory changes. I had my ODE and solved it using separation of variables but the equation ...
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1answer
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With respect to inertial observer standing at the starting point of why is the velocity of ejected mass of rocket $v + v_0$

We derived the equation of motion of a rocket this way: all the velocities are taken with respect to inertial observer standing where the rocket starts. As we take upwards direction to be positive. ...
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107 views

Gravity Turn initial ascent

When executing a gravity turn a rocket will generally first ascend vertically to around 10000m. I need to calculate this initial stretch while knowing the specifics of the rocket and how high I want ...