I am using the derivative of momentum (dp/dt) with Newton’s 3rd Law with the gravitational force of Earth.
F - [Force of gravity on rocket] = dp/dt
F - (G * m_e * m_r / r2 ) = v * dm/dt + ma
F = Force created by fuel (at time t)
G = Gravitational Constant
m_e = Mass of Earth
m_r = Mass of...
I have been researching the rocket pendulum fallacy and have gotten into some spirited debate on the subject.
If I understand correctly...
1. if the thrust is perfectly in line with the centerline (and no outside forces act on the craft other than gravity) it does not matter where the source...
1. Homework Statement
Hi, I'm trying to calculate the formula for the position vs. time of a rocket landing from an altitude of 100km. I'm neglecting a lot of forces for simplification but basically, I want to solve ##F_{net} = Drag - mg##.
2. Homework Equations
Drag Force: D = ## \frac...
Hey,
I'm tutor for theoretical physics for first year students and I found a question that I couldn't answer so far. It's about the rocket equation. I tried to derive the acceleration without using infinite small variables, but somehow there is one term left that shouldn't be there. In the...
1. Homework Statement
Find the initial velocity of the boost phase (when water is coming out). Here is everything I know -
Mass of rocket with no water is 0.13kg, mass of rocket with water is 1.1kg. The total length of the rocket is 0.48m.
The time to the maximum point is 3.46 seconds, and...
1. Homework Statement
The total mass of a space shuttle and its launch vehicle is
M=2000t.
a) What must be the minimum size of the thrust force, to make the rocket move?
b) The actual thrust of the rocket is F=30MN. What is its acceleration in the beginning?
c) Assume that a mass of a 1000t...
So if you have a rocket lets say that discards all the structural and engine mass continuously at zero velocity that is relative to the rocket until only the payload is traveling at the final velocity - then what will the equation of motion will look like? we can neglect the drag and...
Hi there,
Recently i was watching some rocket launches and was wondering why they are tethered before takeoff, after some searching i found out that they are used to keep a constant supply of fuel to replace the part that boils off. But is there any other uses for such tethers?
I read that a thrust augmentor can significantly increase the efficiency of a jet engine (http://www.pulse-jets.com/phpbb3/viewtopic.php?t=931). Now from my understanding, the thrust agumentor is sort of like a ramjet. Only, in this case, the cold air is being sucked in along with the hot air...
Hi.
In Newtonian physics, total mass is conserved, but open systems can obviously gain or lose mass, such as a rocket. But how can the term ##\dot{m}v## be Galilean invariant?
Looking at a humble smoke detector - a metal plate with some alpha source on one side. I guess the fission products / apha etc emitted in one direction are absorbed into the metal, and the opposite direction go into space. So there should be a minute net force ? Would that be useful as a "sail"...
In this derivation of the Ideal Rocket Equation (https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation#Most_popular_derivation), they use the fact that ##V_e = V - v_e##, or that the velocity of the exhaust in the observer frame ##V_e## is the velocity of the rocket ##V## minus the speed of...
My 12 year old asked me this question. I have a MS in Mechanical Engineering, so I can usually answer his physics questions, but this one stumped me. When lifting off, why do most rockets turn close to horizontal almost immediately? Of course we know they need mostly horizontal speed to...
NASA decided to stop *WFIRST and concentrate on Mars project (send humans to Mars).
What do you think about it?
In my opinion, since a lot of ventures have begun space developments such as SpaceX and this proves that rockets make money, NASA should tackle WFIRST. Generally, we cannot earn...
Rockets are quite expensive and it takes about 2000 to 10000 dollars to place 1 pound into orbit. So I was wondering: Is the size or the fuel mass of a rocket a big concern or will it be of no help economically if we make smaller rockets with less fuel mass for the same amount of payload...
This is an IB problem from November 2017. Two rockets are separated by 6E8m (2 sec x c, or two light-seconds), w.r.t. Earth, and are approaching Earth from opposite directions. Rocket A approaches from left at 0.6c. Rocket B approaches form right at 0.4c.
According to Earth, when do they...
Greetings All!
I am not sure if this is the correct place to post this, but I think that since rocket fuel is considered a chemical reaction, this sections seems appropriate. Right, to the topic. Me and my team from the spaceflight society are looking forward to building a hybrid rocket fuelled...
1. Homework Statement
We are doing water rockets and I don't know how to calculate the height it went from it's hang time. It's total hang time was 7.35 seconds, and I know it's vertical acceleration was -9.8m/s^2 from gravity, and I'm assuming I need to first find out it's initial velocity...
Hey Guys,
I'm on a rocket team at my university and we are attempting to figure out the force of opening acting on some of our parachutes. Typically this is done using the following equations, in particular, the one in the top right corner.
This is where our trouble begins. In the Recovery...
if you and your friend ride a supersonic rocket , do you can listen to your friend voice ?
I mean if you travel faster than sound will you can hear anything ,It's difficult to imagine.
And thanks so much,
1. Homework Statement
A 300 g rocket is on a cart that is rolling to the right at a speed of 2 m/s. The rocket engine, when it is fired, exerts an 6 N thrust on the rocket. Your goal is to have the rocket pass through a small horizontal hoop that is 18 m above the launch point. At what...
I have a project where I will be launching a rocket from a high altitude weather balloon. I am planning on launching the rocket at around 70Km or even higher. My main concern is the igniter not being able to ignite the engine because of the low amount of oxygen. Is there any way around this...
Well, first thing, I am new to this forum and it looks pretty good and I'm looking forward to reading more from it and post more questions.
Well rocket propeling (or anything that uses some material to propel up when shooting it down) seems pretty straight forward at first, you have some gas...
Hello everybody!
I have been thinking about something for a while now. I would like to make a magnetic nozzle for a rocket engine. Basically, I would like to ionize the hot and high pressure gaz in the combustion chamber and then use a strong magnetic field to adjust the nozzle throat...
I'm going to make a water propelled pop bottle rocket for a competition. The bottle holds 1.5 liters and we are going to fill some amount of it with water and pressurize it to 75 psi. When triggered, water will come out of the hole in the cap and propel the rocket. The rocket is perfectly...
1. Homework Statement
The gravitational potential energy of a certain rocket at the surface of the Earth is -1.9x10^12 J. The gravitational potential energy of the same rocket 300km above the Earth's surface is -1.8x10^12 J. Assume the mass of the rocket is constant for this problem.
A) How...
Hey guys,
I'm new to the forum and I have a question that has stumped several of the professors at my school. My idea is to use an electric motor with a solid rocket engine on a thrust stand to spin the exit cone. The concept would make use of centripetal force to increase the pressure of...
1. Homework Statement
A rocket is fired from from the ground at initial velocity of ##v_0## and at an angle ##\theta##. At its highest height it splits into 2 parts of equal masses. The first part is fired straight up and at velocity ##v_0/2##. Find the angle and intensity of the second part...
1. Homework Statement
Force exerted by the ground on the rocket
Mass of the Rocket = 1500kg
Duration of landing impact = 0.04 s
Velocity at time of impact = 175 m/s
Distance travelled = 30km
Time taken to complete journey = 6 minutes
Acceleration due to gravity = 9.8 m/s^2
2. Homework...
I was wondering if there is an actual definition given by a recognised organisation over what is meant by the word "rocket". In case there is not, I wanted to reflect upon what do we really mean when we say rockets.