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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29 views

Why does this segment seemingly get added twice in the Rocket Equation?

I'm new here, and I'd like to ask a little question about the Tsiolkovsky rocket equation, which I am learning right now. I am a beginner at this and am just starting to grasp the concept, but there's ...
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How to calculate total energy of rocket launch?

I'm trying to simulate a rocket launch and I want to check that the total energy of the system is conserved the rocket and the fuel that was burnt. I know that for the rocket the energy is the kinetic ...
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About rocket propusion

As a rocket expels burned fuel the location of the center of the mass of the rocket (in a frame attached to the rocket) changes. Must one take this into account in an exact solution of the rocket ...
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208 views

Why Rocket entering the atmosphere starts to burn?

Why, the faster I ride my motorcycle, it gets colder and colder - while the rocket entering the atmosphere very quickly, starts to burn? In other words: When cold air particles hit hot surface (e.g. ...
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26 views

How high can aerodynamic drag be during rocket landings? [closed]

Reading about Falcon 9 and Starship landing profiles, I found out that the maximum Gs the rocket can experience during landing is greater than 1g (peaked at 5g for a falcon 9 and around 3 g for ...
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34 views

Tsiolkovsky rocket equation with external force

I think I understand how the equation arises when there is no external force. I'm following the Wikipedia article on this, there is a nice sketch: At time $t$, the total momentum of the system is $...
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2answers
80 views

Two rockets, A and B, are initially close together and on the same axis but facing in opposite directions

Suppose we have two rockets, A and B, and they are initially close together and on the same axis but facing in opposite directions. Their masses are $m_A$ and $m_B$ respectively, excluding fuel. ...
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91 views

Would shooting an atom out the back of a rocket at the speed of light propel the rocket forward at the speed of light? [closed]

Although impossible as far as we know, if we were to somehow shoot even an atom out the back of a rocket at the speed of light, would that propel the rocket forward at the speed of light? If I ...
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1answer
36 views

Trouble showing from first principles the equation describing the motion of a water drop through a cloud

If we had a water drop, initially of mass $m_0$ and speed $v_0$, falling through a cloud for a time T and during this time its mass increases at a constant rate $\alpha m_0$, through accretion of ...
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2answers
108 views

Rocket's momentum

It is well known that to give a liftoff a rocket, we use the momentum principle: The momentum of the gases emitted by a rocket and the rocket's momentum is equal to zero. So why is it not enough to ...
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59 views

1g acceleration, speed and gravity

Let's assume a spaceship is at rest and that it increases the acceleration from 0 to g m/s in 1 second and that it then continues accelerating at 1g for an indefinite length of time. This means that ...
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21 views

Velocity of rocket thrown fuel box less that previous thrown fuel box's velocity?

I have been reading the following paper "Correction to the Traditional Ideal Rocket Thrust Equation" and there's one thing at the end that I don't get to understand. In the footnote of the ...
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36 views

Could Ionised Air be used as Propellant in Ion Thrusters?

NASA's deep space missions have used xenon as a propellant in ion thrusters, however the force they produce has been limited to hundredths of a newton. Is there an alternative fuel which could be used ...
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25 views

Earth to space without using confessional engines [closed]

Let's say we had a source of almost unlimited electric energy comparable to the volume and weight of today's orbital rockets. Is there a known propulsion engine that can take such vehicle from the ...
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1answer
23 views

Location of Compression shock wave in de laval nozzles

Is there a way to compute the location of an compression shock inside de laval nozzles as a function of either the the pressure ratio or the area ratio in the divergent part of the nozzle?
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48 views

Physics 1 course: inertial force in a rocketship [closed]

I am requesting a clarification to the solution of a question posed in my Physics 1 course. Calculate the force acting on an astronaut with mass $m$ in a rocket that is starting on earth's surface ...
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4answers
67 views

How do chemical propulsion systems not break the law of conservation of energy?

Lets say that hypothetically we have a rocket with constant mass, and an engine providing a constant force. I understand that it is unrealistic to have a rocket of constant mass with a rocket engine ...
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22 views

Why did SN10 rest at a slight incline after landing? [closed]

Recently when SpaceX's SN10 landed, before it exploded, it sat still on the ground for a few minutes. It appears to be resting at a slight incline. Why is this?
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Error in Derivation of Tsiolkovsky Rocket Equation?

Can someone point out where the error is in the following derivation of the Tsiolkovsky rocket equation? According to the Newton's second law combined with his third law, we know that the net external ...
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1answer
18 views

Rocket Engine Throat Condition

We know from 1-dimensional theory that at the throat of the C-D nozzle the local Mach number should be exactly $1$, with a matching throat area $A_t$ specific to nozzle inlet $A_0$. However, in real-...
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87 views

Are chemical rockets really beyond 60% efficient?

Are chemical rockets really beyond 60% efficient? https://en.wikipedia.org/wiki/Rocket_engine “Rocket engine nozzles are surprisingly efficient heat engines for generating a high speed jet, as a ...
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136 views

3DOF Rocket Dynamics for an LQR controller

I'm trying to define a simplified model of a rocket to implement an LQ regulator. What I need is the translational dynamics on the earth's inertial frame and the rotational dynamics in the body frame. ...
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2answers
60 views

What is the net force on a rocket immediately upon ignition?

While recently watching a rocket launch, I had a thought that I was a little bit confused about, involving the basic physics of a rocket launch. Before ignition, the rocket experiences no net force: ...
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4answers
74 views

Gravitational acceleration of an object towards earth which is not in freefall

This is a hypothetical question, a brain experiment, thought someone might be able to answer it for me, someone who has a good understanding of general relativity etc. Assume I take an object and ...
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2answers
242 views

A simple doubt on classical mechanics problem [closed]

Question: "At a certain instant of time, the mass of a rocket going up vertically is $100 kg$. If it is ejecting $5 kg$ of gas per second at a speed of $400 m/s$, the acceleration of the rocket ...
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79 views

Infinitesimals meaning in this context

I was solving this rocket propulsion's classic mechanics exercise: M is the instantaneous rocket's mass, and v its velocity. The exhaust gases are ejected with speed 𝑢 relative to the speed 𝑣 of the ...
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72 views

Can we connect several Nano Spacecraft moving at 20% speed of light? [closed]

Nano spacecrafts are one gram silicon chips that will be accelerated to 20% of the speed of light to reach Alpha Centauri in 20 years. I wonder could we connect several spacecraft after they were ...
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28 views

How much work could be got from temperature differences during a rocket's descent from low earth orbit?

It strikes me that there is a lot of energy dissipated during a typical rocket's descent from Low Earth Orbit. How could that energy be captured and used? I wonder whether it might be possible to ...
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1answer
38 views

Is it easier to apply angular momentum to a rocket with the engine off?

Let's say I've got a rocket that I need to rotate for my next maneuver. Assuming it's flying through full vacuum, I can turn off my engine first, and then use reaction control thrusters to rotate, or ...
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1answer
64 views

Solving global warming by moving Earth closer to Mars

One way to reduce global warming is to get our planet farther away from the Sun. If we placed a couple of thousands of SpaceX's Merlin rockets upside down in the tropics or Sahara i.e. somewhere where ...
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1answer
126 views

Expanding Newton's Second Law and changing $v$ to $V_e$ gives you the rocket equation. Where does this change of $v\to V_e$ come from?

I've noticed that from Newton's Second Law, if you expand the right side using the product rule and change the v to Ve, the rocket equation appears very easily... Why is this second term of velocity ...
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34 views

Rocket Trajectory (launching it vertically) [closed]

I don't have a camera that can produce a video at 240fps and i my physics experiment i am trying to find the maximum height reached by a water rocket. My question:- Can i use my iphone 11, that has ...
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90 views

Is momentum conserved in the rocket equation? If so, why is there force? [closed]

I'm studying the rocket equation and from what I get from it the momentum between the fuel and the rocket is conserved. But if that happens, how come the calculated force is not zero? The rocket ...
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“To come back to Earth…it can be five times the force of gravity” - video editor's mistake?

I've watched The Truth About Gravity With Professor Jim Al-Khalili | Gravity And Me | Spark where astronaut Chris Hadfield says at 3:55: To come back to Earth is violent Then after several seconds ...
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1answer
38 views

Are there real-world devices similar to the thrust reversers in this scene in Star Wars? [closed]

In Star Wars 3 in the initial crash scene where a spaceship enters the atmosphere for an emergency landing the thrust engine is blocked by a part of the ship and absorbs a part of the thrust which ...
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1answer
154 views

How do Roll, Pitch, and Yaw Interact?

I'm making a spaceship piloting game, and I'm trying to make the movement follow the laws of physics. The ship is able to control it's angular acceleration in pitch, yaw, and roll. The way I've ...
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58 views

Center of mass of a rocket

Is it correct to say that the center of mass of any space rocket is stationary here on earth? roughly speaking, without external forces the motion of the center of mass is preserved, so since the ...
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1answer
30 views

How to calculate Mars and Lunar payload if I have LEO payload? [closed]

I am working on a project and i need the payload capabilities of different rockets to LEO, mars and lunar orbit. Usually the LEO payload along with all other relevant data is given for all rockets. is ...
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20 views

Spacecraft propulsion, thrust and delta V relation

For a spacecraft which has interplanetary mission(eg mars) After deciding the propellant ISP value and Delta V required, how to calculate the thrust required? F = m dot * Ve + (pe - p0) * Ae According ...
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51 views

How does a rocket travel in a vacuum space? [duplicate]

OK.. let us consider a rocket initially at rest in outer space. Space is considered as vacuum so there is hardly something that rocket can insert a force on. So if the rocket fires up its engines will ...
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1answer
153 views

How do I calculate where a solid fuel rocket will land if the rocket is launched at a 45 degree angle?

Let's say I was launching a model rocket at a 45 degree angle to find the distance between the rocket's landing site and the rocket's launching site, but before launch I wanted to try and calculate ...
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45 views

How to calculate the positioning angle of a rocket for launch

I am building a model rocket. I want it to end up in a specific position. If I am taking into account the acceleration, starting position, end position, mass, and wind speed, how do I find the angle I ...
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38 views

In the rocket equation, does lowering the acceleration due to gravity increase decrease exhaust velocity? [closed]

I'm doing work for an intro space flight class, and I have to calculate the amount of fuel I need to get sizable a space craft, around 200 thousand kg in dry mass, into a transfer orbit from the ...
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2answers
421 views

Can a radially launched projectile orbit a planet?

Imagine a spherical planet with no atmosphere. A ball is launched radially with a velocity $v$, maintaining $\frac{v_e}{\sqrt2}<v<v_e $ and there is no other objects in the universe (Ideal two ...
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1answer
53 views

What is mercury-like liquid on 2nd stage SpaceX engine [closed]

I was watching this: https://m.youtube.com/watch?v=UM8CDDAmp98 At around 22:33 It showed one side of the engine with what looked like some sort of liquid running on it. The liquid was at the top of ...
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Equation of Forces for Rocket - The Rocket Equation and Newton's Third Law

Assume a rocket is being vertically accelerated in a homogeneous gravitational field. In the reference frame of the rocket, the burnt fuel is being exhausted downwards with a velocity of $\Delta u$. ...
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58 views

Throwing darts in a rocket ship

Far from major gravitational sources... A man is standing throwing darts at a dartboard in a rocket ship. The thrust is upwards so he feels almost like he would on Earth but the G-force is slightly ...
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207 views

What can “action” mean in “All the action takes place inside the rocket”?

This answer to "How fast is fuel escaping a rocket for it to reach escape velocity 11km/s?" includes the following: From Rocket and Spacecraft Propulsion: Principles, Practice and New ...
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1answer
34 views

Relationship between payload weight to the range of a ballistic missile

is it possible to talk about how much extra range a ballistic missile gets if its warhead were to shrink by say 10x?? that is without knowing other details about the missile. For example: Iran claims ...
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1answer
52 views

How can I simulate a path for my model rocket?

I made a model rocket. Specifications: Total weight - 1.635 N (wet). It has a custom solid rocket motor with black powder producing 5 N for 15 sec. So how can I calculate how high will it travel? Some ...

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