# Questions tagged [calculation]

How to calculate things directly related to Space Exploration as defined in the help center, or how the calculations have been done in the past or will be done in the future.

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### How can I calculate the altitude my waterrocket will fly with a certain amount of pressure?

I am trying to calculate how high my waterrocket will fly before launching it at different pressure using the Tsiolkovsky rocket equation. However, I stumbled upon an issue since the altitude that it ...
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### How to calculate the cooling jacket of a liquid propellant engine with an external component? [closed]

When designing a small rocket engine with a thrust of 100 N, questions arose about the cooling of the combustion chamber and the nozzle apparatus. It was decided to ...
538 views

### Why is the value of the Isp of the Rocketdyne J-2 Saturn V engine in my calculation so off?

While calculating the delta V the Saturn V has on its second stage, I wanted to also calculate the Isp of the J2 rockets engines. However, the value difference between my results and the values given ...
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77 views

### Computing Flight Characteristics for Different Propellant Grain Geometries?

Consider the following image: I am interested in mathematically accounting for some of these different geometries but have had little success so far in finding how this can be done. The first thought ...
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159 views

### How I can find the angular orbital velocity of satellite in circle orbit?

I know that we have the angular orbital velocity of a satellite in circle orbit as $w_0=\frac{v}{r}$, but I want another way to find out the angular orbital velocity of a satellite in the circle orbit....
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### GMAT LEO spacecraft simulation

I started using GMAT, I have to design an LEO of an AEOLUS Satellite and I have the TLE of the launching. My question is how do I plug the TLE numbers into the spacecraft section (Keplerian element ...
1 vote
118 views

### How do you find the burn-time of a specific solid rocket fuel?

I read this post about finding the propellant mass needed to reach a specific altitude: How do you find the propellant mass needed to reach an inputted altitude?(altitude at end of burn plus altitude ...
1k views

### How do you find the propellant mass needed to reach an specified altitude? (altitude at end of burn plus altitude during coast)

This question is basically entirely explained in the title, but I'll explain it more so this question doesn't get shut down. Basically, does anyone have an equation to find the propellant mass(solid) ...
1 vote
74 views

### How can I find the predicted approximate altitude of a rocket based on simply the propellant, specific impulse, and propellant mass?(solid propellant) [duplicate]

I am getting all the inputs I outlined above, including burn-time which I could not mention above(character limit), from a small scale motor test. I know there are specific specific impulses for each ...
196 views

### How to calculate the optimal mass ratio for a multistage water rocket?

I do know about the Tsiolkovsky rocket equation for optimising multistage rockets, however the equation requires a fixed exhaust velocity which is something that water rockets don't have, however I ...
50 views

### When sending a ship to mars what is the optimal travel path [duplicate]

its pretty self explanitory but I need to figure it out but not something from the past a ship that could be sent in the next 5-7 years what would be my time frame using the least amount of fuel and ...
359 views

### What am I missing about rocket nozzle isentropic flow?

Playing a bit with Cpropep-Web, something looked wrong to me about how it models isentropic flow through a CD nozzle. I'm taking the RS-25 characteristics as an example. I ask for a frozen equilibrium ...
736 views

### Question Deriving Mass Flow Rates for an Engine

I am trying to follow the calculations made in this blog post for a $50$ lbf. IPA/Nitrous Oxide engine, but cannot seem to get the values the author made for their propellant flow rates. Since the ...
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1 vote
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### Gravity Calculation Inaccurate?

For the past week, I've been working on an Effective Gravitational Acceleration calculator on Desmos. This calculator ignores drag and assumes that a rocket is flying up completely straight. What this ...
282 views

### Using CEA for monopropellants

CEA (Chemical Equilibrium with Applications) calculates chemical equilibrium compositions and properties of complex mixtures and is the industry standard. Applications include assigned thermodynamic ...
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1 vote
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### How to calculate combustion temp? [duplicate]

I was reading about a propellant combination using ethanolamine(19.9% propellant fraction w/ 1% Copper Chloride) and 90% HTP(80.1%). I am trying to design a hypothetical engine around the propellant, ...
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### Which programs are used to calculate delta V and launch dates to get to other objects?

I have noticed that many people here have used different programs to calculate the launch dates and delta V to get to other planets. For example: https://space.stackexchange.com/a/59585/44505 https://...
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### Would this idea of a water rocket to pass the Karman line work?

When I fly my water rockets as a hobby I use this formula to calculate the height of the flight so I get an idea of how high my water rocket will fly. My idea is to make a theoretical water rocket ...
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232 views

### How to calculate catalyst bed geometry (length/radius) for a monopropellant thruster?

Catalyst design is central to the development of monopropellant thrusters and hence, ignoring its importance, as I have realised, is not very good practice. My question is if the mass flow rate, bed ...
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### Relationship between osculating eccentricity and Brouwer-Lyddane short eccentricity

I was under the impression that the mean elements are given by taking the average over an orbital period of the satellite, i.e.: $e_{mean}(t) = \int_{t}^{t+T(t)}e_{osc}(t')dt'[0.367in]$ where $T(t)$ ...
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### I'm trying to create a trajectory to Mars for a low thrust ion thruster engine using astrogator

I'm trying to create an optimize a trajectory to Mars for a number of low thrust high specific impulse engines. I am having trouble with the initial set up. I created a LEO exit spiral using a ...
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628 views

### Inconsistencies in calculating exhaust velocity

I'm quite sure this is either a small or just plain stupid mistake but my anxiety is getting the better of me. when calculating exhaust velocity this is the equation used: however I keep getting ...
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### How to find the hyperbolic angle given the mean anomaly?

I'm modelling a hyperbolic gravity assist trajectory around Jupiter and trying to calculate the coordinates for each hour interval before/after passing periapsis. I've calculated $M_h = 0.0176$ is the ...
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### Do monopropellants have a characteristic length?

I was reading about calculating thrust chamber geometry, and a key tool seems to be the characteristic length, L*. The engine I'm modelling (hypothetically! please don't take down the question) uses ...
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### How do I correctly convert State Vectors to Orbital Elements to State Vectors at t (sec since epoch) in 2D?

I am following Rene Schwarz' formulas and I've verified my calculations work using the converter by Tony Dunn. State Vectors to Orbital Elements Orbital Elements to State Vectors Convert between ...
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### Predicting Satellite Flyover Calculations by Hand

Recently I used transit-finder.com to get a really cool picture of the ISS transiting the sun. The prediction from the website was spot-on. Since then I'm absolutely fascinated by how the prediction ...
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### Optimizing trajectories with GMAT: how to understand the "Vary" parameters, and how to know what values to use for them?

I've been using GMAT in my free time to optimize trajectories, and have varied burn component values and spacecraft states, usually with success. The vary command in GMAT, with the Yukon optimizer ...
569 views

### Could an astronaut with a jump and a "jet pack" "jump" off of the Moon?

The initial naïve question was: "Could an astronaut with a jump and a "jet pack" "jump" off of the Moon?" :) For fun, let's assume the optimal circumstances: Gemini era ...
364 views

### James Webb Space Telescope Velocity Loss Formula or how fast will JWST be going on L+26

I was never great at math but now I wish I would have taken it more seriously. We have an office bet going and I need to come up with a formula to figure out the future velocity the JWST. I was able ...
58 views

### Please explain a way of calculation of Lagrange multiplier in algorithm of low thrust transfer

In David Vallado's book 'Fundamental of Astrodynamics and Applications', chapter 6.7. ("Continuous-Thrust Transfers") there is an algorithm #47: Low Thrust Transfer. In this algorithm a ...
757 views

### GMAT: Finite burn targeting, solving for burn duration and quaternion

I'm trying to using GMAT to design a finite burn with a fixed attitude throughout the burn. I do not know the attitude needed at the start, nor do I know the burn duration needed. I set up six ...
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### How to calculate the Lagrangian points positions?

I have two bodies, one rotates around another on orbit. For i.e. Earth and Sun or Moon and Earth. If we know masses, velocity, distance and keplerian elements of orbit, how can we find the positions ...
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### Wrong position during orbit propagation in Unity

I've been working on an orbital physics module for months now, and have reached a barrier. I have two methods, one to convert from Kepler elements to planet-centric coordinates, and the other to ...
222 views

### When was Lucy's mission first scripted in Excel and why is that what Lockheed Martin chose to do it with?

CNBC's NASA spacecraft launches toward Jupiter asteroids on an intricate path charted by Excel Years before Lucy took off, Lockheed Martin mission architect Brian Sutter used Excel to chart the ...
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### Calculating rocket nozzle throat area

I'm trying to calculate a rocket nozzle throat area, $A_t$. My propellant is KNDX. I am trying to do this according to the following equations, taken from this reference: where $P_t$ is and $T_t$ ...
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### How to calculate the time to reach a given true anomaly? [closed]

I'm looking for a general formula or procedure calculate time to reach any given true anomaly.
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### What are the energy requirements to reach Earth orbit and Mars orbit assuming no efficiency losses?

Suppose some magic propulsion method exists which directly converts electricity into kinetic energy. And its efficiency is 100%. And its weight is 0. What is a way to calculate the energy requirements ...
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1 vote
574 views

### What exactly the orbit accuracy requirement in KSP missions and contracts, and how is it mathematically defined and implemented? [closed]

When playing e.g. the Rosetta mission in Kerbal Space Program (KSP), one of the things one can achieve is called Orbit Accuracy. Unfortunately, after searching KSP's forums and Wiki I still can not ...
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### Making sense of rocket engine thrust calculation [closed]

Recently I've been trying to design a hypothetical rocket engine using the mass flow rate, exit mach, temperature, and pressure calculations provided by NASA's own website. I've come to know quite ...
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### How to calculate degrees above/below horizon? (For KiNET-X rocket getting to an altitude of over 200 miles.)

I live near Detroit, Michigan, USA. Let's say I'm viewing from 42.34768° N, 83.47610° W, altitude 718 feet (219 meters) above MSL (mean sea level.) (No, these are not my exact coordinates.) I've ...
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1 vote
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### Apogee estimate starting from simplified one-dimensional numerical simulations

I asked a question on pen and paper apogee estimation and got an answer from @tom-spilker that called my attention: He said that he quickly estimated an inclined launch apogee from the results of a 1-...
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### Calculating mass expelled from cold gas thrusters

Consider a cold gas thruster rated at 1 lbf per firing. The thruster is on-off: there is no throttling, so when it fires it's at a constant full thrust. Assume the gas is nitrogen, and that it has a ...
1 vote
3k views

### What is the relation between chamber pressure and expansion ratio?

I've always assumed that the expansion ratio of an engine equaled the pressure inside the engine over the atmospheric pressure, but I'm not sure this is right, could someone check me on this?
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### What is the EXACT time that the sun will rise, at the Apollo 11 landing site, in Feb 2173

So this was only supposed to be a fun little easter egg in my sci-fi novel for any eagle-eyed reader who decided to run the numbers, but I've driven myself quite literally - to distraction for the ...
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### Finding the mass flow rate of a blowdown system?

This is a rather amateur question I will admit but how does one find the mass flow rate of an engine with a given tank pressure? Is it really as simple as calculating the cross-section of all plumbing,...
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### Pointing accuracy and relevant manoeuvers CUBESAT

How do you calculate or determine the pointng accuracy of your CUBESAT in sunlit-part and eclipse-part modes? Also how do you determine the maximum roll/pitch/yaw angles and slew rate required in ...
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### Accuracy of converting from TLE/Orbital Elements to Cartesian if used for other propagator?

Say that I wanted to propagate a real-life satellite based on an initial position in space. However, the only source of data I can get is from a tracking website like CelesTrak or Space-Track, where ...
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### Where can I learn to calculate the physics of an ion thruster?

I am trying to build an ion thruster, but I don’t know where to start learning the actual numbers behind one. I know how they work on a basic level, but not much more. Basically I want to be able to ...