# Questions tagged [rocket-equation]

Equation stating that the change in velocity (delta-v) of a single stage rocket is equal to the exhaust velocity times the natural log of the ratio of final to initial mass, named after Russian scientist Konstantin Tsiolkovsky.

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### What does “m Δv” stand for in the rocket equation?

I'm currently trying to understand how the Rocket Equation works. I've gotten this far: mv = (m+Δm)(v+Δv) − Δm(v−ve) Left side is the momentum of the rocket+fuel BEFORE, and right side is the momentum ...
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### How could I find the pressure and/or the Isp at the exit of a rocket nozzle if I have data for the throat and comb. chamber?

I've been looking at this for some time and working with CEA which will only give me data points for the pressure, temperature, Isp, etc. for the Injection, Combustion Chamber End, and the Throat; but ...
224 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,...
142 views

### Specific impulse and delta-v in Tsiolkovsky's rocket equation

According to Tsiolkovsky's rocket equation, it is possible to calculate the delta-v of a multistage rocket if you know the characteristics of each stage of the rocket. In my case, the only ...
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### Is a cheap English translation available of Tsiolkovsky's “Outside the Earth”?

Anyone know where to pick up a copy of Konstantin Tsiolkovsky's science fiction book titled "Outside the Earth" (alternately titled: "Beyond the Planet Earth" and "Beyond ...
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### Sources for values for realistic thrust calculation exercise?

I want to use this simplified equation to calculate the thrust of multiple different real engines: $$F = \dot{m} V_e + (p_e - p_0) A_e$$ Source: https://www.grc.nasa.gov/www/k-12/airplane/rockth....
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### How can I use the Rocket Equation and Staging for a ballistic flight?

I want to calculate the a) thrust b) mass of fuel c) optimal staging of a rocket, which shall fly up to for example an altitude of 50 km in a ballistic flight trajectory. In school I learned the ...
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### Design impact on Chamber pressure

What is forming the amount of chamber pressure which is produced in a rocket engine and why would you like to have an higher chamber pressure? I was calculating the SpaceX Raptor engine for myself, ...
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### How much lower is max q if launching from high altitude (i.e. mountain top)?

I looked at very simple max q formula: q=1/2 ρv^2 (https://en.wikipedia.org/wiki/Max_q). As air density is lower with altitude, the max q should be lower as well, and also should occur at higher ...
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### Would major changes since “Equations of powered rocket ascent and orbit trajectory” was written reduce its applicability?

I was wondering where I can learn how to calculate the trajectory of present day launch vehicles. I've stumbled upon this book, called Equations of powered rocket ascent and orbit trajectory. ...
2k views

### Payload capacity of a rocket

Why does a rocket have far more payload capacity when placing an object in LEO compared to when it's placing the object in farther orbits, like on the Moon? If a rocket has sufficient thrust to take ...
86 views

### Spacecraft propulsion, Thrust, Delta V

For a spacecraft on an interplanetary mission (e.g. Mars), after deciding the propellant ISP value and Delta V required, how do you calculate the thrust required? $$F = \dot{m} V_e + (p_e - p_0) A_e$$ ...
264 views

### Why can I not use stoichiometry to calculate the O/F ratio of my rocket? [duplicate]

I am attempting to calculate the oxygen to fuel ratio (O/F) for my hybrid rocket engine (paraffin wax and gaseous oxygen). I know I can use the oxidizer to fuel equation to calculate this, but my ...
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### Specific Heat Ratio for a perfect gas mixture

I am reading Rocket Propulsion Elements by George P. Sutton & Oscar Biblarz, 9th Edition. In the fifth chapter, I was introduce to the specific heat ratio k for the perfect gas mixture, Eq. 5-7: (...
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### Do lower pressure pressure-fed rockets get more Delta-V?

I was playing around with the math for getting a pressure-fed rocket to orbit and came across something that I haven't seen addressed anywhere. In a pressure-fed rocket, the chamber pressure of the ...
182 views

### Convert the impulsive solution to a low-thrust

The spacecraft transfers from an orbit with the following parameters: Perigee - 700 km Apogee - 6000 km Inclination - 64 deg Argument of perigee - 250 deg to and orbit with the parameters: Perigee -...
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### I don't know where to start with the calculations - rocket engine

Last year I stumbled upon the "How to design, build and test a rocket engine" pdf and since then I have been intrigued by making one (or at least calculating it). So I've been doing some ...
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### Need help finding a clean expression for exit velocity [duplicate]

I'm trying to calculate a engine burning LOX and ethanol (96%) and for that I am using both CEAgui, a GUI for NASA's CEA (Chemical Equilibrium with Applications) code Sutton's Rocket Propulsion ...
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### Delta-v difference between Mars and Moon

Considering a simple Hohmann transfer, does it take less Delta-v and propellant to go to Mars than to the Moon
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### What is the maximum practical deltaV obtainable from a chemical rocket launched from earths surface?

What is the maximum practical deltaV obtainable from a chemical rocket launched from earths surface? Not an exact number as there are too many variables but an approximate maximum assuming a 10,000kg,...
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### How to calculate these engine parameters on my own?

I am a space enthusiast and am intrigued mostly by rockets. I recently found a book HOW to DESIGN, BUILD and TEST SMALL LIQUID-FUEL ROCKET ENGINES and have been fiddling around with rocket engine ...
217 views

### mass of propellant required + rocket equation

I'm doing some research for a class project and I have a questions about the use of the rocket equation to get the propellant mass required. If $m_1$ is the final mass, and $m_0$ is the initial mass, ...
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### Calculations needed to full-design a rocket

Suppose I want to put a cubesat in Titan's orbit (saturn's moon). and I want to calculate what rocket power I need, how do I calculate it? Where do I begin? total mass of the probe or delta-v needed? ...
733 views

### What would the rocket equation look like for 4 ion thrusters?

If i have 4 ion thrusters(IFM Nano Thrusters), how would the rocket equation have to be done to calculate the total delta-v?
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### What would a human rocket be like to launch a human off Mimas?

In a comment on Is there a self-rounding celestial body from which an Olympian could jump into space? @jpa made a modest proposal. What if we stacked a bunch of athletes on top of each other and ...
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### Need help with 'Tsiolkovsky's Rocket Equation': What's the maximum weight of my rockets command module?

A civilization wants to transport a command module towards another planet that is passing by. Their planet has a radius of 6'800 kilometers and weighs about 9 × 10^24 kg. They have no stronger engines ...
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### Can I exclude coriolis effects if I express a rocket launch in an inertial reference frame for a rotating earth?

I am wondering if I can exclude coriolis effects and centrifugal forces if I calculate my position relative to an inertial reference frame with as origin the launch site at the moment of lift off. ...
176 views

### In principle, could the oxygen tanks of an 'air breathing' rocket, be filled during ascent?

(Thinking of SABRE and it's heat exchanger). As I understand it, Skylon would take off with full oxygen tanks. Putting aside engineering difficulties, is there a thermodynamic reason why a hybrid ...
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### How much higher could g be before we couldn't launch rockets? [duplicate]

Obviously having a higher gravitational acceleration makes it harder to get rockets into orbit / escape. How much stronger could earths gravity be before we would no longer be able to do the sort of ...
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### Is there a general relativistic relativistic rocket equation?

I am not to familiar with rocket equations but I know that if you combine special relativity with classical mechanics you get "c" as a speed limit. Basically the closer you get to "c" the more you ...
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### Some exercise questions about Tsiolkovsky's Rocket Equation and Thrust Equation

I have found 6 of the question's answers, but I don't know they are correct. The last question about time of the burn I get negative result -0.42 seconds. Time could not be a negative value, so I ...
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### What are Mass Rate(∆v)/∆v, Mass Rate(Isp)/Isp and time of burn(MR)/MR graphs?

I have some problems about Tsiolkovsky's Rocket Equation and some graphs. Firstly, I didn't get what I can do with Rocket Equation formulas as seen below, Also, what these three graphs try to mean? ...
134 views

### Lightest possible orbital rocket - being launched from high altitude

Iv'e been looking into micro-satellites launches on small rockets - from what I could find the lightest rocket to deploy a satellite into LEO is the SS-520-4 which had a weight of 2600kg. If ...
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### What do the axis labels mean in this plot (apparently from Sutton 8th edition)?

In the Analytical Graphics Inc. video Low-Thrust Space Trajectory Design and Optimization the speaker Pradipto Ghosh of AGI shows a slide at around 07:00 shown ...
645 views

### Does a high staging number have diminishing returns? Is there a way to address that mathematically?

I was reading this question: Help me understand what Farside, a ten "stage" rockoon looked like? How was it configured? Comments link to Highest stage counts in actual launchers? but here ...
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### Cooling jacket calculation issue [duplicate]

I'm going through How to Design, Build, and Test Small Liquid-Fuel Rocket Engines. The reference explains how to calculate the water flow gap for the cooling jacket that surrounds the combustion ...
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### Saturn S-IVB math

https://en.m.wikipedia.org/wiki/Saturn_V https://physics.stackexchange.com/questions/88145/why-are-rockets-so-big/88163#88163 User Asad posted a graph based on rocket science. https://i.stack.imgur....
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### How much fuel is necessary to cause delta-v?

For a project, I need to calculate how much thrust and how much fuel I need for getting into LEO. What I know: Delta-V necessary ($\approx 9.4$ km/s) Dry (empty spacecraft mass) What I don't know: ...
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### Problem in finding Propellant Mass using Rocket equation where total mass includes components dependant on Propellant Mass

Formulation - $$e^{\Delta v/v_{exhaust}} - 1=mass_{fuel}/mass_{structure}$$ $\text{let } k=e^{\Delta v/v_{exhaust}} - 1$ $$\implies mass_{fuel}= k \times mass_{structure}$$ According to SMAD (...
For simple rockets, using the rocket equation is simple enough. $$\Delta v = v_e ln\left(\frac{m_i}{m_f}\right) = I_{sp} \ g \ ln\left(\frac{m_i}{m_f}\right)$$ plug in full and empty weights and ...