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 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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5 votes
2 answers
69 views

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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4 votes
0 answers
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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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4 votes
1 answer
396 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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5 votes
1 answer
351 views

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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161 views

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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1 vote
1 answer
100 views

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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2 votes
1 answer
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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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2 answers
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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 ...
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7 votes
3 answers
320 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 ...
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0 answers
181 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 ...
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2 votes
0 answers
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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 ...
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3 votes
1 answer
149 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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3 votes
1 answer
191 views

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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2 votes
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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 ...
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5 votes
0 answers
187 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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1 answer
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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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1 vote
0 answers
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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
1 answer
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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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3 votes
0 answers
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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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2 votes
1 answer
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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
0 answers
27 views

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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4 votes
2 answers
740 views

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 ...
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1 vote
1 answer
307 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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15 votes
3 answers
231 views

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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3 votes
1 answer
131 views

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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1 vote
1 answer
89 views

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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6 votes
2 answers
1k views

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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5 votes
1 answer
243 views

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 ...
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0 votes
0 answers
90 views

Ion Lifter Thrust Calculation Problem

I've recently started building an ion lifter. I tried calculating the thrust the lifter produces but I came to a value that is way to high for such a small lifter. I'm using a 40kV at 1800mA AC ...
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3 votes
1 answer
213 views

How do you calculate the percentage of light-speed a ship with a certain delta-v can achieve, accounting for relativistic effects?

I was doing some back-of-a-postage-stamp calculations on high-isp interstellar spacecraft earlier and realised something. If I design a spaceship which according to the rocket equation has a very high ...
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4 votes
1 answer
2k views

Moment of Inertia of rocket

I am trying to model a rocket launch, and am trying to calculate its moment of inertia at each instant. I am assuming a two-stage rocket with a liquid fuel tank, plus a payload (nosecone-shaped for ...
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4 votes
1 answer
199 views

Orbit Elliptical Fitting

Question: Given a set of XYZ (3D) coordinates in the Earth-fixed frame, after converting them to the inertial frame, how do I perform orbit fitting in the least-squares sense (meaning minimising all ...
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3 votes
1 answer
344 views

Are hyperbolic trigonometric functions used to calculate hyperbolic orbits?

The following comment is really intriguing! I would say, "Yes, The equations for going from Mean Anomaly to Eccentric Anomaly to True Anomaly are indeed different for hyperbolic orbits than for ...
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0 votes
0 answers
48 views

How to calculate the amount of lunar regolith needed to reduce solar radiation in an area on earth by 0.2% or 0.5%

I am working on a climate change that doubles as a lunar infrastructure project. I am wondering if anyone could direct me to resources or help me answer the question of how much regolith scattered ...
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3 votes
2 answers
237 views

How fast would one have to move to achieve permanent lunar day by perpetually moving along with the solar terminator?

This comment got posted and I did not understand it. for those interested, one rod per moonhour is about a quarter furlong per fortnight. If I googled correctly and jumped to the right conclusions.....
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4 votes
2 answers
2k views

How to calculate position of GPS Satellite with transmitted ephemeris data?

How can I calculate the position of a satellite using the ephemeris data transmitted by each satellite? I will then use positions generated from each GPS satellite's self-reported ephemeris to ...
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3 votes
0 answers
303 views

How to satellite-to-site range given site coordinates and satellite ephemeris?

How can I calculate the distance of a position on earth to a satellite (for example a GPS satellite)? The satellites position is exactly known by its ephemeris data. In a related question I've asked ...
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3 votes
1 answer
110 views

Are there any equations out there that can calculate the burnup of an asteroid depending on angle?

Are there any equations that can calculate the burnup of an asteroid depending on the angle? I want to be able to calculate the magnitude of an asteroid impact with the angle being the changeable ...
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6 votes
1 answer
189 views

Calculate Date of Spring Equinox, possibly using JPL's Horizons website?

I'm familiar with orbit ephemerides and the ways to use those to plot orbits and positions. However, in all the charts I find, I can't seem to find a way to determine when an equinox on another planet ...
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6 votes
1 answer
193 views

Calculation of V1 (orbital speed) during ascent

I am studying instrumentation of NASA's Orion spacecraft, and there is a readout for V1 (I am assuming this is the "first orbital velocity", for circular orbit), and it seems to be in small decimals. ...
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3 votes
1 answer
341 views

How to calculate angle in elliptic orbit?

I would like calculate angle in elliptic orbit ZCP at any time, where: Z (position of periapsis), C (center of ellipse), P (current position of planet). I find topic, where is picture (in accepted ...
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4 votes
1 answer
892 views

Why doesn't the Merlin 1-D use higher LOX to RP-1 mixture ratios?

So I've been screwing around with CEARUN, which is the chemical equilibrium with applications program created by NASA. I've been using it to calculate theoretical Isps for rocket engines using RP-1 ...
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5 votes
1 answer
5k views

What is the time dilation between Mars and Earth resulting from the mass difference?

I am not sure I understand the time dilation correctly, but if mass has direct impact on time, then let's consider cosmological event - one orbit of planet Earth around the Sun. This event will person ...
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1 vote
1 answer
134 views

Can a solar mirror increase an ion engine 's output?

Could an ideal size solar sail work as a parabolic mirror to increase the out put of an ion engine? Would the extra weight encumber the ion engine nullifying the increases sunlight on the ion engine? ...
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7 votes
1 answer
2k views

Calculations Apollo astronauts were trained to do by hand if loss of guidance computer and/or data & coms link to Earth?

This answer to the question is it possible to navigate space travel with no computer? currently contains the line Yes, as long as you don't care where you end up but I am not so sure this is true. ...
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3 votes
1 answer
329 views

What was NASA's “LUROVA” Operational Thermal Computer Model analog or digital? How were capacitors used?

@GremlinWrangler's answer links to Apollo Rover Lessons Learned Applying Experiences on the Apollo Lunar Rover Project to Rovers for Future Space Exploration by Ronald A. Creel, Space and Thermal ...
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1 vote
0 answers
438 views

How to make satellite ground track on map?

I want to make satellite ground track using matlab. I already had a position of satellite(ECI) by solving Kepler equation. And I know convert ECI to ECEF using rotation determinant. Then I convert ...
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9 votes
1 answer
1k views

How can I calculate the orbital elements from two position vectors and a time difference?

I have two position vectors for my satellite, and I know that the satellite reaches these two positions 15 minutes apart. I know I can find the inclination using linear algebra and my position ...
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