Orbital Mechanics

SpaceNut · 2023-01-15 12:35:11

The departure and arrival contain the concepts of how we get from point A to B.

Its, going to need more than that to consider trajectory to any place not orbital.

Such things as wet and dry mass for a given payload as well as number of stages must also be considered since that is just the launch equation. The equation changes since we are changing the amount of the rocket/ mass that remains as we continue the flight towards the target.
The next pseudo launch in orbital mechanics is once we do the earth departure launch to escape earth's gravity to which these are the reduced mass numbers remaining.
Landing is a different equation and so is the system to get to orbit of the target location.

tahanson43206 · 2023-01-29 06:50:42

A presentation on flight to the Moon, using a space tug, is available from GW Johnson Postings.

http://newmars.com/forums/viewtopic.php … 84#p198484

The presentation may be helpful to improve understanding of what is required to move from the Earth to the Moon without magic.

Earlier in the GW Johnson Postings topic, there is a similar presentation about a flight to Mars.

No magic is provided. The laws of physics (and orbital mechanics) are available for study.

In order to leave Earth for Mars, expenditure of energy and mass are required.

In order to achieve orbit with Mars, and discounting the fanciful notion of aerobraking, expenditure of energy and mass are required.

(th)

GW Johnson · 2023-01-30 10:27:52

I don't want to be dogmatic about this topic, because I am no expert in orbital mechanics. And I have no way to examine 3-D finite-element computations.

I know the mechanics of elliptical 2-body problems well enough to use the textbook equations in a spreadsheet, and I know an approximation to the 3-body interaction that gets good delta-vee numbers for departures and arrivals.

One can do a lot with those simple models, but it is not everything that can be done. The real experts with the 3+-body computer models are the real authority there.

What I have looked at is transfer orbits from one planet to another. In the case of Earth to Mars, it is easy enough to to place yourself at the distance of Mars's orbit from the sun just as Mars is getting there, too. The difference between your transfer orbit velocity and Mars's orbital velocity about the sun is your relative velocity with respect to Mars, it is directed toward Mars (which is literally trying to run over you), and it is larger than Mars escape velocity by far.

If you encounter Mars dead-center on, you either have a huge delta-vee to land direct, or you crash and make a huge crater. Even with Hohmann min-energy transfer, your speed at entry is near 6 km/s, vs 5 km/s escape. Faster trajectories lead to higher speeds at entry, and are directed non-tangentially to Mars's orbit. It's a vector addition, not a scalar addition.

If you do this as a tangential, grazing encounter, you can enter the atmosphere and aerobrake. But you will need a landing burn at one level of delta-vee or another (and I think SpaceX has been underestimating it, with their Starship simulations at Mars). And you need a heat shield more or less comparable to one that would survive entry from low circular Earth orbit.

Again, for a tangential, grazing encounter, you could also make a burn into orbit about Mars, but you have to pay attention to which side of the planet to encounter. One one side, orbit speed decreases your required delta vee into orbit, on the other, it is increased. And with Mars's rotation, you do not want to orbit the wrong direction, because that makes orbit-surface and surface-orbit operations tougher in terms of delta-vee. You can ignore that at the slow-spinning moon, but not fast-spinning Mars and Earth.

That's as far as my knowledge goes. If there is a way to enter orbit about Mars without making an orbit entry burn, or doing some sort of aerobraking, I do not currently understand it. And I probably won't in the future.

GW

Last edited by GW Johnson (2023-01-30 10:35:39)

Void · 2023-02-01 21:01:22

If I have caused any suffering, I regret it. I will not push any more here.

Done.

GW Johnson · 2023-02-01 22:56:55

Void:

I didn't say it couldn't be done, I just said I couldn't do it. I also said I'm not the expert.

Push all you want! You may well run across an expert that knows how to do those non-elementary things. I hope you do.

GW

tahanson43206 · 2023-02-19 21:16:37

For Void .... I ** just ** asked ChatGPT if it could do trajectory planning. Here is a copy of the session:

tahanson43206
In a chat earlier today, you showed me you can compute the thrust needed to achieve geosynchronous orbit from an initial state. I am emboldened to ask if you can compute a trajectory for an object launched from Earth? I want to find the most efficient flight plan, given constraints.
Yes, I can certainly help with that! To calculate a trajectory for an object launched from Earth, we will need to consider a number of factors, including the object's initial velocity, the gravitational force of the Earth, and atmospheric drag.
To begin, we will need to specify the initial conditions of the object, including its position and velocity at the time of launch. We will also need to define any constraints, such as the maximum amount of fuel that can be used or the desired final destination.
Based on these initial conditions and constraints, we can use mathematical models and numerical simulations to calculate the trajectory of the object. This typically involves solving systems of differential equations that describe the motion of the object in three dimensions, accounting for the gravitational force of the Earth, the effects of atmospheric drag, and any other external forces acting on the object.
To find the most efficient flight plan, we can use optimization techniques to minimize the amount of fuel required or to maximize the final velocity of the object. This may involve adjusting the trajectory of the object at various points along the flight path, using maneuvers such as gravity assists or aerobraking to conserve energy.
There are a variety of tools and software packages available for simulating spacecraft trajectories and optimizing flight plans, such as NASA's General Mission Analysis Tool (GMAT) or the University of Texas at Austin's Trajectory Browser. However, designing an efficient trajectory for a spacecraft is a complex and highly specialized field, so it may be best to consult with an experienced aerospace engineer or mission designer for guidance on the specifics of your project.
tahanson43206
Thank you once again, for your encouragement. And I want to offer thanks once again, to the staff
You're welcome! And thank you for your kind words. Please let me know if you have any more questions or if there's anything else I can help you with.

(th)

tahanson43206 · 2023-02-20 19:54:33

This post is intended to help to prepare for the next session with ChatGPT.

Google
what is circumference of geosynchronous orbit in kilometers
264,869 km
Orbit radius 42,155 km (26,194 miles)
Orbit circumference 264,869 km (164,582 miles)
Arc length per degree 736 km (457 miles)

(th)

tahanson43206 · 2023-02-27 11:44:06

https://www.forbes.com/sites/startswith … fba95f5d2e

SCIENCE
EDITORS' PICK
We All Learned Physics' Biggest Myth: That Projectiles Make A Parabola
Ethan Siegel
Senior Contributor
Starts With A Bang
Contributor Group
Mar 12, 2020,02:00am EDT
This article is more than 2 years old.
Italian astronomer and scientist Galileo Galilei (1564 - 1642) performs his legendary experiment,... [+] dropping a cannonball and a wooden ball from the top of the Leaning Tower of Pisa, circa 1620. This was designed to prove to the Aristotelians that objects of different weights fall at the same speed, but wound up demonstrating a number of important physics principles. (Hulton Archive/Getty Images)
Italian astronomer and scientist Galileo Galilei (1564 - 1642) performs his legendary experiment,... [+] GETTY
Anyone who's ever taken a physics course has learned the same myth for centuries now: that any object thrown, shot, or fired in the gravitational field of Earth will trace out a parabola before striking the ground. If you neglect external forces like wind, air resistance, or any other terrestrial objects, this parabolic shape describes how the center-of-mass of your object moves extremely accurately, no matter what it is or what else is at play.
But under the laws of gravity, a parabola is an impossible shape for an object that's gravitationally bound to the Earth. The math simply doesn't work out. If we could design a precise enough experiment, we'd measure that projectiles on Earth make tiny deviations from the predicted parabolic path we all derived in class: microscopic on the scale of a human, but still significant. Instead, objects thrown on Earth trace out an elliptical orbit similar to the Moon. Here's the unexpected reason why.
<snip>
Studying the various effects that are at play, both external to the Earth as well as within our planet's interior, can also teach us when and under what circumstances it's important to make these considerations. For most applications, air resistance is a far larger concern than any effects like the various layers of Earth's interior or dynamical friction, and treating Earth's gravitational field as a constant is totally justified. But for some problem, these differences matter. We are free to make whatever approximations we choose, but when our accuracy suffers beyond a critical threshold, we'll have no one but ourselves to blame.
Photographer Howard Clifford flees the Tacoma Narrows Bridge at approximately 10:45 AM on November... [+] UNIVERSITY OF WASHINGTON TACOMA NARROWS BRIDGE HISTORICAL
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I am a Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges. I have... Read More
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(th)

GW Johnson · 2023-02-27 12:25:07

What's really happening is the effect of the type of model you use. If you model the projectile in 2-D Cartesian coordinates with a constant gravity acceleration, and no air drag, the math for a parabola is what results. For things that only fly a little ways, so that Earth's curvature and the variation of gravity with altitude, are of no significance, then that is an easy and accurate model.

If on the other hand, you model in polar or spherical coordinates with inverse-square law gravity and no drag (or other influences), the you get one of 3 shapes for the path, depending upon its max speed. If max speed never exceeds escape, the path is an ellipse, and motion is periodic. If the max speed is exactly escape, the path models as a parabola, to a one-way escape. If the max speed exceeds escape, the path models as a hyperbola to a one-way escape.

GW

tahanson43206 · 2023-02-28 07:13:41

For GW Johnson re #159 and many examples of orbit calculations...

Thank you (again) for the many contributions of papers, presentations and spreadsheets you have made to this forum, over a number of years.

Until now, I have been content to try to assist by facilitating the publication of your work in the NewMars environment.

Now, the time may be right for me to inquire about the possibility you might be willing to provide coaching for NewMars members who might be interested in running the software (spreadsheets) you have developed on their own computers.

You have shown output from your spreadsheet software that illustrates a wide variety of complex orbits, and in particular, you have shown transitions from one ellipse to another as spacecraft depart from a body or arrive at one.

Is there one of the spreadsheets already published that you would recommend for a NewMars member to download and run on their own computer?

Is there anyone besides me who might be willing to try to run an orbit calculation spreadsheet on their own computer?

If you would like to offer one of your spreadsheets for a class activity, I would be happy to copy it to Dropbox and make it available to NewMars members (and the general public) via link.

(th)

tahanson43206 · 2023-02-28 07:18:40

For GW Johnson...

I do not know but am hoping that your software (spreadsheets) might be able to illustrate the collapse of a solar system ellipse into an Earth centered one.

The situation I am thinking about is a launch failure. If a launch to Mars fails because the third stage falters, the initial orbit would be a solar system (Sun centered) ellipse, but with the failure of the third stage, and inability to reach escape velocity, the orbit would collapse into an Earth centered ellipse.

Can your software deal with that situation?

In this scenario, the initial state at the start of a run would be the vector and location of the spacecraft.

To simplify everything, I would propose staying in the equatorial plane throughout.

To simplify further, I would propose a velocity crossing GEO of 10 km/s, and an inclination towards the East from vertical of 45 degrees.

Can a spreadsheet pick up the spacecraft at that point, and guide it into an Earth centered ellipse?

(th)

GW Johnson · 2023-02-28 09:15:53

Tom:

I didn't download any of these spreadsheet worksheets ready to use, I created them from blank worksheets by just filling the cells with numbers and formulas to do what I wanted to do with the numbers. Once you've done it a couple of times, then becomes apparent that there is a sort of organization to it, which is why they look the way they do.

The closest thing I have to a course in "how to do" this elliptic orbit stuff is that last pair of files I sent, with the little short paper and slide set. The "meat" there was the 6 figures in the paper, which are also the 6 "meat" slides in the slide set. From there, one gains experience "just doing it". Those 6 illustrations are the guide to what one puts into the spreadsheet cells. It is based on finding the ellipse from known apoapsis and periapsis distances from the occupied focus. That's the simplest case.

I don't really think of those spreadsheet layouts as software in and of themselves (although the spreadsheet program itself is software, and I understand that), they are just an automatically-updating form of the kinds of calculations that I used to do pencil and paper long ago. It's just an organized set of calculations. The spreadsheet software just makes it easy to do repetitive or iterative work. And, it can plot data for you, if you can figure out how to tell it what you want, and arrange the data into a format that it recognizes.

For your launch failure scenario, if the vehicle is traveling under escape speed (as evaluated at the local radius from the center of the Earth) when thrust fails, then it will then be traveling along some sort of ellipse with the Earth at one focus. The trick is to find out what it is, since the vehicle is not at its perigee (or apogee) in any general sense. I know that can be done, but I don't know how to do it myself. At least not yet. It would be modeled as an Earth-centered (at one focus, not the actual center of the ellipse) 2-body problem.

Depending upon the speed, that ellipse might be a rather elongated one, with a very high apogee. If this apogee extends far enough, you have to worry about its stability, meaning it may really be a 3-body problem, and the 2-body model for it may not be accurate.

I will have to think about how one would determine the ellipse from a speed and direction at radial distance from a central body at one focus. That would be a useful trick.

GW

Last edited by GW Johnson (2023-02-28 09:22:48)

tahanson43206 · 2023-02-28 11:25:28

For GW Johnson re #162

Thanks for the hint that there might be something useful that comes out of this discussion, to add to your already impressive ability.

I'll follow through on delivery of your latest work today .... I've allowed a couple of local distractions to take up time.

What I'd like to see come out of this topic is a learning system/structure of some kind, based upon spreadsheets, as a kind of familiar environment for folks who might be interested in learning a bit about orbital mechanics, but who are awed/inhibited/daunted by the powerful tools that are available.

GMAT is (apparently) a software that is available to the public under NASA's watchful eye. I am planning to look at it to see if it might run on one of my systems. it is said to run on a variety of operating systems. I'm sure it requires hefty processing power and lots of memory, and high performance display equipment.

If you are interested in building upon your already massive investment in education and experience, I recommend you consider buying a second computer just for GMAT and similar high power programs. You still have a number of years in which your existing skills can be fed into GMAT or similar software. My guess is you will be surprised and delighted to discover how far you can go with modern powerful tools.

Meanwhile, back at block 1, I'd like to see your packaging of knowledge in spreadsheet form propagated outside your currently very small set of followers.

I'll ask again.... is there anyone in the current membership of NewMars who has even the slightest interest in learning how to compute approximations of flight paths for spacecraft. GW Johnson's collection of work is published (via Dropbox links) in the GW Johnson topic.

I would like to see images via imgur.com that show the achievements of individual NewMars members.

There is very likely to be NO other forum on Earth (or anywhere) with an instructor comparable to GW Johnson, who is at the same time willing to work with folks who are not enrolled at MIT or Caltech in Aerospace Engineering.

My expectation is that any NewMars member can run a spreadsheet.

I'd like to see some demonstrations of the ability to install and run GW's software.

I'll be attempting to follow that path as soon as I've delivered the files later today.

(th)

tahanson43206 · 2023-02-28 15:48:54

Here is a link to a set of files created by GW Johnson: Basics of Elliptic Orbits

https://newmars.com/forums/viewtopic.ph … 86#p206786

It might be possible to persuade Dr. Johnson to provide the spreadsheet that generated much (if not all) of this data.

We already have an earlier version of the spreadsheet available for download. You should be able to find it in the GW Johnson Postings topic.

(th)

tahanson43206 · 2023-03-02 11:30:14

GMAT is a software tool sponsored by NASA and (apparently) supported by volunteers as a shareware system

GMAT download | SourceForge.net
SourceForge
https://sourceforge.net › ... › Simulation
Jan 26, 2023 — Download GMAT for free. General Mission Analysis Tool. The General Mission Analysis Tool (GMAT) is an open-source tool for space mission ...
User Interface: Command-line, wxWidgets
Rating: 4.7 · 10 votes · Free
GMAT Files · GMAT Reviews · Support
GMAT - Browse /GMAT/GMAT-R2020a at SourceForge.net
https://sourceforge.net › ... › Simulation › GMAT
Download Latest Version gmat-win-R2022a.zip (376.7 MB) Get Updates ... LINUX There are two precompiled Linux distributions of GMAT, packaged as compressed ...
General Mission Analysis Tool (GMAT) Version R2018a
NASA (.gov)
https://software.nasa.gov › software › GSC-18094-1
The General Mission Analysis Tool (GMAT) is the world's only enterprise, multi-mission, open source software system for space mission design, optimization, ...

I am about to download it to a spare/non-critical Ubuntu system, and will report progress.

(th)

tahanson43206 · 2023-03-02 11:59:44

Here is the Readme after installation:

Welcome to the wonderful world of GMAT!
GMAT is a software system for space mission design, navigation, and optimization
applicable to missions anywhere in the solar system ranging from low Earth orbit
to lunar, Libration point, and deep space missions. The system contains
high-fidelity space system models, optimization and targeting, built-in
scripting and programming infrastructure, and customizable plots, reports and
data products that enable flexible analysis and solutions for custom and unique
applications. GMAT can be driven from a fully featured, interactive Graphical
User Interface (GUI) or from a custom script language.
The system is implemented in ANSI standard C++ using an Object Oriented
methodology, with a rich class structure designed to make new features easy to
incorporate. GMAT has been used extensively as a design tool for many missions
including LCROSS, ARTEMIS and LRO and for operational support of TESS, SOHO,
WIND, ACE, and SDO.
-----------------------------------------------------------------------
License and Copyright
-----------------------------------------------------------------------
“NASA Docket No. GSC-19097-1, identified as “General Mission Analysis Tool (GMAT) Version R2022a”
Copyright © 2022 United States Government as represented by the Administrator of the National Aeronautics and Space Administration. All Rights Reserved.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. “
-----------------------------------------------------------------------
Contact Information
-----------------------------------------------------------------------
For general project info see: https://gmat.atlassian.net/wiki/spaces/GW/overview
For source code and application distributions see:
http://sourceforge.net/projects/gmat/
For other comments and questions, email: gmat-developers@lists.sourceforge.net
-----------------------------------------------------------------------
Credits and Acknowledgments
-----------------------------------------------------------------------
GMAT uses:
- wxWidgets 3.0.4 (http://www.wxwidgets.org/)
- TSPlot (http://sourceforge.net/projects/tsplot/)
- SOFA (http://www.iausofa.org/)
- Apache Xerces (http://xerces.apache.org)
- JPL SPICE (https://naif.jpl.nasa.gov/naif/)
- OpenFramesInterface (https://gitlab.com/EmergentSpaceTechnol … sInterface)
- Boost (http://www.boost.org/)
- f2c (http://www.netlib.org/f2c)
- MSISE 1990 Density Model (https://kauai.ccmc.gsfc.nasa.gov/instantrun/msis)
- IRI 2007 Ionosphere Model (https://irimodel.org/)
Planetary images are courtesy of:
- JPL/Caltech/USGS (http://maps.jpl.nasa.gov/)
- Celestia Motherlode (http://www.celestiamotherlode.net/)
- Bjorn Jonsson (https://bjj.mmedia.is/)
- NASA World Wind (http://worldwind.arc.nasa.gov/)
Some icons are courtesy of Mark James (http://www.famfamfam.com/)
-----------------------------------------------------------------------
Installation and Configuration
-----------------------------------------------------------------------
WINDOWS
The GMAT Windows distribution contains a zip file. When unzipped,
locate the bin directory then select GMAT.exe to open GMAT.
LINUX
There are two precompiled Linux distributions of GMAT, packaged as
compressed TAR files, ready for expansion and use. The precompiled
releases were built and tested on Ubuntu 20.04 LTS and on Red Hat
Enterprise Linux 7. Linux users on those platforms can download the
tarball file and uncompress it into place using the command
tar -zxf <TarballPackageName>
where <TarballPackageName> is either gmat-ubuntu-x64-R2022a.tar.gz
or gmat-rhel7-x64-R2022a.tar.gz.
Linux building and testing was performed on the indicated distributions. The
packaged executable files have also been run on Ubuntu 22.04 LTS, and on Red Hat
Enterprise Linux 8.
MACOS
The GMAT macOS distribution is now provided as a NASA-signed and notarized
DMG file, and is compatible with macOS 10.15 (Catalina) and above. This
distribution was built and tested on macOS 11.7 (Big Sur).
After downloading and mounting (i.e. opening) the dmg file, installation
of GMAT is as simple as copying the resulting "GMAT <version>" folder to
one of the following two locations:
- System-wide /Applications folder. This requires admin privileges.
- User's $HOME/Applications folder. Admin privileges are not needed.
Copying GMAT to any other location will result in an error on launch.
BUILDING FROM SOURCE
GMAT is distributed in source form as well, and can be compiled on macOS,
Linux and Windows. Build instructions for GMAT can be found at
https://gmat.atlassian.net/wiki/spaces/ … ild+System.
USING GMAT OPTIMAL CONTROL / CSALT
Using the GMAT Optimal Control capability -- implemented in the
EMTGModels and CsaltInterface plugins -- requires additional
installation steps. See the "Software Organization and Compilation" section
of the GMAT Optimal Control user guide in
gmat/docs/GMAT_OptimalControl_Specification.pdf for complete instructions.
-----------------------------------------------------------------------
Running GMAT
-----------------------------------------------------------------------
WINDOWS
On Windows 10, locate your GMAT directory. From there, open the bin directory,
then double click GMAT.exe to open GMAT.
To use the GMAT Console, open a Command Prompt and change directories to the
GMAT bin folder. The GMAT command line program is executed by running the
GmatConsole application in that folder:
GmatConsole

LINUX
On Linux, open a terminal window and change directories to the GMAT bin
folder. The GMAT command line program is executed by running the
GmatConsole application in that folder:
./GmatConsole
The Beta GUI can be run using the same terminal window by running
Gmat_Beta:
./GMAT_Beta
Linux users can create a launcher for either the command line
application or the GUI application by following the instructions for
that process for their Linux distribution.

MACOS
On macOS, open a Terminal window and navigate to the GMAT bin folder. The
GMAT command line program is executed by running the GmatConsole
application in that folder:
./GmatConsole
The Beta GUI application can be run using the ‘open’ Terminal command,
executed in the bin folder:
open GMAT-R2022a_Beta.app
or by double-clicking the GMAT-R2022a_Beta.app in the Finder.

Please see the GMAT User Guide for important instructions on how to use MATLAB,
Python, SNOPT7, and gfortran for each GMAT distribution.
-----------------------------------------------------------------------
User Information
-----------------------------------------------------------------------
User docs are available in pdf and html format. The pdf documentation
is distributed in letter and A4 size in this package. The files are
located here: /doc/help/help-letter.pdf and /doc/help/ help-a4.pdf
Online documentation is available here: https://gmat.sourceforge.net/docs/.
For new users, see the Getting Started and Tour of GMAT sections first,
then take the tutorials. The tutorials are included in print versions
in the help documents, and are available in video form here:
https://www.youtube.com/channel/UCt-REO … 3t-xH6kbjg
For a list of new functionality, compatibility changes, and known issues,
see the Release Notes section in the User's Guide.
-----------------------------------------------------------------------
Developer Information
----------------------------------------------------------------------
Source code is available here:
https://sourceforge.net/p/gmat/git/
Compilation instructions are available here:
https://gmat.atlassian.net/wiki/spaces/ … ild+System
Design Documentation is available at the links below:
https://gmat.atlassian.net/wiki/spaces/ … +Documents
https://gmat.atlassian.net/wiki/spaces/ … Components
You can sign up for mailing lists here:
https://sourceforge.net/p/gmat/mailman/

This is (apparently) Version 2022a

(th)

tahanson43206 · 2023-03-02 12:12:17

Here is a file in the bin folder called gmat.ini

[Help]
; to point to local html files: BaseHelpLink=J:////GMAT//GmatDevelopment//doc//help//html//%s.html
BaseHelpLink=http://gmat.sourceforge.net/docs/R2022a/html/%s.html
PropSetup=http://gmat.sourceforge.net/docs/R2022a/html/Propagator.html
PropSetupKeyword=Propagator.html
ChemicalTank=http://gmat.sourceforge.net/docs/R2022a/html/FuelTank.html
ChemicalTankKeyword=FuelTank.html
ChemicalThruster=http://gmat.sourceforge.net/docs/R2022a/html/Thruster.html
ChemicalThrusterKeyword=Thruster.html
Command Summary for Propagate=http://gmat.sourceforge.net/docs/R2022a/html/CommandSummary.html
Command Summary for PropagateKeyword=CommandSummary.html
Planet=http://gmat.sourceforge.net/docs/R2022a/html/CelestialBody.html
PlanetKeyword=CelestialBody.html
Star=http://gmat.sourceforge.net/docs/R2022a/html/CelestialBody.html
StarKeyword=CelestialBody.html
Asteroid=http://gmat.sourceforge.net/docs/R2022a/html/CelestialBody.html
AsteroidKeyword=CelestialBody.html
Comet=http://gmat.sourceforge.net/docs/R2022a/html/CelestialBody.html
CometKeyword=CelestialBody.html
Moon=http://gmat.sourceforge.net/docs/R2022a/html/CelestialBody.html
MoonKeyword=CelestialBody.html
New Coordinate System=http://gmat.sourceforge.net/docs/R2022a/html/CoordinateSystem.html
New Coordinate SystemKeyword=CoordinateSystem.html
ParameterCreateDialog=http://gmat.sourceforge.net/docs/R2022a/html/Variable.html
ParameterCreateDialogKeyword=Variable.html
Gmat=http://gmat.sourceforge.net/docs/R2022a/html/Assignment.html
GmatKeyword=Assignment.html
ParameterSelectDialog=http://gmat.sourceforge.net/docs/R2022a/html/CalculationParameters.html
ParameterSelectDialogKeyword=CalculationParameters.html
PenDown=http://gmat.sourceforge.net/docs/R2022a/html/PenUpPenDown.html
PenDownKeyword=PenUpPenDown.html
PenUp=http://gmat.sourceforge.net/docs/R2022a/html/PenUpPenDown.html
PenUpKeyword=PenUpPenDown.html
VariableArrayString=http://gmat.sourceforge.net/docs/R2022a/html/Variable.html
VariableArrayStringKeyword=Variable.html
[Fuel Tank]
VolumeHint=
PressureModelHint=
MassHint=
DensityHint=
TemperatureHint=
ReferenceTemperatureHint=
PressureHint=
[Ground Station]
IDHint=
HardwareHint=
CentralBodyHint=
StateTypeHint=
HorizonReferenceHint=
XHint=
YHint=
ZHint=
LatitudeHint=
LongitudeHint=
AltitudeHint=
[Formation]
AvailableSpacecraftListHint=
SelectedSpacecraftListHint=
AddSpacecraftHint=
RemoveSpacecraftHint=
ClearSpacecraftHint=
[Parameter]
VariableNameHint=
VariableValueHint=
ArrayNameHint=
ArrayRowValueHint=
ArrayColumnValueHint=
StringNameHint=
StringValueHint=
CreateVariableHint=
SelectHint=
CreateArrayHint=
EditArrayHint=
CreateStringHint=
VariableListHint=
ArrayListHint=
StringListHint=
ClearVariableHint=Clear
ClearArrayHint=Clear
ClearStringHint=Clear
[Propagator]
IntegratorTypeHint=
IntegratorInitialStepSizeHint=
IntegratorAccuracyHint=
IntegratorMinStepSizeHint=
IntegratorMaxStepSizeHint=
IntegratorMaxStepAttemptsHint=
IntegratorMinIntegrationErrorHint=
IntegratorNominalIntegrationErrorHint=
ForceModelErrorControlHint=
ForceModelCentralBodyHint=
ForceModelPrimaryBodiesComboHint=
ForceModelPrimaryBodiesEditHint=
ForceModelPrimaryBodiesSelectHint=Body to use for gravity and drag model
ForceModelGravityModelHint=Name of gravity model
ForceModelGravityDegreeHint=Maximum degree to use
ForceModelGravityOrderHint=Maximum order to use
ForceModelGravityMaxDegreeHint=Maximum degree allowed by file
ForceModelGravityMaxOrderHint=Maximum order allowed by file
ForceModelGravityStmLimitHint=Cutoff for degree and order used to calculate state transition matrix
ForceModelTideModelHint=Tide model to use
ForceModelTideHint=Tide models contained in current potential or tide file
ForceModelGravityPotentialFileHint=Gravity potential file path
ForceModelGravitySearchHint=Browse for potential file
ForceModelGravitySaveHint=Write current model to temporary.cof file
ForceModelTidePotentialFileHint=Tide model file path
ForceModelTideSearchHint=Browse for tide file
ForceModelTideClearHint=Clear loaded tide file
ForceModelDragAtmosphereModelHint=
ForceModelDragSetupHint=
ForceModelMagneticFieldModelHint=
ForceModelMagneticDegreeHint=
ForceModelMagneticOrderHint=
ForceModelMagneticSearchHint=
ForceModelPointMassesHint=
ForceModelSelectPointMassesHint=
ForceModelUseSolarRadiationPressureHint=
ForceModelUseRelativisticCorrectionHint=
[Celestial Body]
AvailableBodiesHint=
SelectedBodiesHint=
AddBodyHint=
RemoveBodyHint=
ClearBodiesHint=
[Celestial Body Properties]
MuHint=
EquatorialRadiusHint=
FlatteningHint=
TextureMapFileHint=
BrowseTextureMapFileHint=Browse for texture map file
[Celestial Body Orbit]
EphemerisSourceHint=
EphemerisFileHint=
BrowseEphemerisFileHint=Browse for ephemeris file
NAIFIDHint=
SPKFileListHint=
AddSPKFileHint=
RemoveSPKFileHint=
CentralBodyHint=
InitialA1EpochHint=
SMAHint=
ECCHint=
INCHint=
RAANHint=
AOPHint=
TAHint=
[Celestial Body Orientation]
SpinAxisRAConstantHint=
SpinAxisRARateHint=
SpinAxisDECConstantHint=
SpinAxisDECRateHint=
RotationConstantHint=
RotationRateHint=
NutationUpdateIntervalHint=
RotationDataSourceHint=
[Spacecraft Ballistic Mass]
DryMassHint=
DragCoefficientHint=
ReflectivityCoefficientHint=
DragAreaHint=
SRPAreaHint=
[Spacecraft Orbit]
EpochFormatHint=
EpochHint=
CoordinateSystemHint=
StateTypeHint=
AnomalyTypeHint=
ElementsXHint=
ElementsYHint=
ElementsZHint=
ElementsVXHint=
ElementsVYHint=
ElementsVZHint=
ElementsSMAHint=
ElementsECCHint=
ElementsINCHint=
ElementsRAANHint=
ElementsAOPHint=
ElementsTAHint=
ElementsRadPerHint=
ElementsRadApoHint=
ElementsRMAGHint=
ElementsRAHint=
ElementsDECHint=
ElementsVMAGHint=
ElementsAZIHint=
ElementsFPAHint=
ElementsRAVHint=
ElementsDECVHint=
ElementsHHint=
ElementsKHint=
ElementsPHint=
ElementsQHint=
ElementsMLONGHint=
[Spacecraft Tanks]
AvailableTanksHint=
SelectedTanksHint=
AddTankHint=
AddAllTanksHint=
RemoveTankHint=
ClearTanksHint=
[Spacecraft Thrusters]
AvailableThrustersHint=
SelectedThrustersHint=
AddThrusterHint=
AddAllThrustersHint=
RemoveThrusterHint=
ClearThrustersHint=
[Spacecraft Attitude]
AttitudeModelHint=
CoordinateSystemHint=
EulerAngleSequenceHint=
StateTypeHint=
RateStateTypeHint=
EulerAngle1Hint=
EulerAngle2Hint=
EulerAngle3Hint=
EulerAngleRate1Hint=
EulerAngleRate2Hint=
EulerAngleRate3Hint=
Quaternion1Hint=
Quaternion2Hint=
Quaternion3Hint=
Quaternion4Hint=
AngularVelocity1Hint=
AngularVelocity2Hint=
AngularVelocity3Hint=
DCM1Hint=
DCM2Hint=
DCM3Hint=
DCM4Hint=
DCM5Hint=
DCM6Hint=
DCM7Hint=
DCM8Hint=
DCM9Hint=
DCM10Hint=
[Spacecraft Spice]
NAIFIDHint=
NAIFIDRefFrameHint=
SPKFileListHint=
AddSPKFileHint=
RemoveSPKFileHint=
CKFileListHint=
AddCKFileHint=
RemoveCKFileHint=
SCLKFileListHint=
AddSCLKFileHint=
RemoveSCLKFileHint=
FKFileListHint=
AddFKFileHint=
RemoveFKFileHint=
[Solar System]
EphemerisUpdateIntervalHint=
EphemerisSourceHint=
EphemerisFilenameHint=
LeapSecondFilenameHint=
BrowseEphemerisFilenameHint=Browse for ephemeris file
BrowseLSKFilenameHint=Browse for leap second kernel
UseTTForEphemerisHint=
[Coordinate System]
NameHint=
OriginHint=
PrimaryHint=
EpochFormatHint=
EpochHint=
SecondaryHint=
XHint=
YHint=
ZHint=
UpdateIntervalHint=
[Finite Burn Setup]
ThrusterHint=
[Burn Thruster]
CoordinateSystemHint=
OriginHint=
AxesHint=
ThrustDirection1Hint=
ThrustDirection2Hint=
ThrustDirection3Hint=
DutyCycleHint=
ThrustScaleFactorHint=
DecrementMassHint=
TankHint=
IspHint=
GravitationalAccelHint=
EditThrusterCoefficientHint=
EditImpulseCoefficientHint=
[Impulsive Burn]
Element1Hint=
Element2Hint=
Element3Hint=
[Begin Finite Burn]
BurnHint=
SpacecraftHint=
SelectSpacecraftHint=
[End Finite Burn]
BurnHint=
SpacecraftHint=
SelectSpacecraftHint=
[Equation]
LeftHandSideHint=
RightHandSideHint=
[Ephemeris File]
SpacecraftHint=
StateTypeHint=
CoordinateSystemHint=
WriteEphemerisHint=
FileFormatHint=
FilenameHint=
BrowseEphemerisFilenameHint=Browse for ephemeris file
InterpolatorHint=
InterpolationOrderHint=
StepSizeHint=
EpochFormatHint=
InitialEpochHint=
FinalEpochHint=
[XY Plot]
ShowPlotHint=
ShowGridHint=
SelectedXHint=
SelectXHint=
SelectedYHint=
SelectYHint=
SolverIterationsHint=
[Parameter Select]
SelectEntireObjectHint=
ObjectTypeListHint=
SpacecraftListHint=
SpacePointListHint=
ImpulsiveBurnListHint=
VariableListHint=
ArrayRowHint=
ArrayColHint=
ObjectPropertiesHint=
CoordinateSystemHint=
OriginHint=
SelectedListHint=
MoveUpHint=
MoveDownHint=
AddSelectedHint=
RemoveSelectedHint=
AddAllHint=
RemoveAllHint=
[Advanced Mode]
NonSavableGUIModeHint=Currently GMAT disallows saving from the GUI if a main script contains #Include statements before the BeginMissionSequence
[Welcome/Links]
; Welcome Links can be either web urls or help topics (windows only)
; For web links, include the http:// to ensure GMAT correctly tries to show
; the web page. Use Welcome/Links/Online to include web links to replace
; help topics on non-windows machines
; For example, "Reference Guide=RefGuide.html" uses the topic from the
; gmat chm file. In Welcome/Links/Online,
; put "Reference Guide=http://http://gmat.sourceforge.net/docs/R2022a/html/RefGuide.html" to
; have a link that works for non-windows machines
Reference Guide=RefGuide.html
Wiki=https://gmat.atlassian.net/wiki/spaces/GW/overview
Source Code at SourceForge=http://sourceforge.net/p/gmat/git/
Online Help=http://gmat.sourceforge.net/docs/R2022a/html
Report an Issue=https://gmat.atlassian.net/browse/GMT/issues/?filter=allissues
[Welcome/Links/Online]
; the inclusion of all of these entries here is necessary because of the
; way the WelcomePanel works - for non-windows platforms, the WelcomePanel
; must be set up to point to Welcome/Links/Online for all selections
Reference Guide=http://gmat.sourceforge.net/docs/R2022a/html/RefGuide.html
Wiki=https://gmat.atlassian.net/wiki/spaces/GW/overview
Source Code at SourceForge=http://sourceforge.net/p/gmat/git/
Online Help=http://gmat.sourceforge.net/docs/R2022a/html
Report an Issue=https://gmat.atlassian.net/browse/GMT/issues/?filter=allissues
[Welcome/Samples]
Sample Missions=../samples
[GettingStarted/Tutorials]
; GettingStarted/Tutorials can be either web urls or help topics (windows only)
; For web links, include the http:// to ensure GMAT correctly tries to show
; the web page. Use GettingStarted/Tutorials/Online to include web links to replace
; help topics on non-windows machines15
; For example, "Reference Guide=RefGuide.html" uses the topic from the
; gmat chm file. In GettingStarted/Tutorials/Online,
; put "Reference Guide=http://http://gmat.sourceforge.net/docs/R2022a/html/RefGuide.html" to
; have a link that works for non-windows machines
Step By Step Text Tutorials=Tutorials.html
Video Tutorials=https://www.youtube.com/channel/UCt-REODJNr2mB3t-xH6kbjg
[GettingStarted/Tutorials/Online]
Step By Step Text Tutorials=http://gmat.sourceforge.net/docs/R2022a/html/Tutorials.html
Video Tutorials=https://www.youtube.com/channel/UCt-REODJNr2mB3t-xH6kbjg
[GettingStarted/Tutorials/Icons]
Step By Step Text Tutorials=StepByStep.png
Video Tutorials=VideoTutorial.png

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tahanson43206 · 2023-03-02 12:15:30

And here is the table of contents for the tutorials web site:

Tutorials
The Tutorials section contains in-depth tutorials that show you how to use GMAT for end-to-end analysis. The tutorials are designed to teach you how to use GMAT in the context of performing real-world analysis and are intended to take between 30 minutes and several hours to complete. Each tutorial has a difficulty level and an approximate duration listed with any prerequisites in its introduction, and are arranged in a general order of difficulty.
Here is a summary of selected Tutorials. For a complete list of tutorials see the Tutorials chapter.
The Simulating an Orbit tutorial is the first tutorial you should take to learn how to use GMAT to solve mission design problems. You will learn how to specify an orbit and propagate to orbit periapsis.
The Mars B-Plane Targeting tutorial shows how to use GMAT to design a Mars transfer trajectory by targeting desired B-plane conditions at Mars.
The Target Finite Burn to Raise Apogee tutorial shows how to raise orbit apogee using finite maneuver targeting.
Table of Contents << Could not print due to Apache Server Internal error

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tahanson43206 · 2023-03-02 20:48:40

For quick reference:

Geosynchronous Earth Orbit radius:

radius of geostationary orbit
AllImagesVideos
MoreAnytime
About 96,000 search results
Ad related to: radius of geostationary orbit
www.generationgenius.com
Earths Orbit & Rotation Lesson - Standards-Based for Grades 3-5
Includes Earths Orbit & Rotation lesson plan, activity, worksheet, video, reading & more. Made in partnership with the National Science Teaching Association. Try it free.
Geosynchronous orbit - Wikipedia
A geostationary equatorial orbit (GEO) is a circular geosynchronous orbit in the plane of the Earth's equator with a radius of approximately 42,164 km (26,199 mi) (measured from the center of the Earth). A satellite in such an orbit is at an altitude of approximately 35,786 km (22,236 mi) above mean sea level.
en.wikipedia.org/wiki/Geosynchronous_orbit
Geosynchronous orbit - Wikipedia

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tahanson43206 · 2023-03-03 11:41:43

Google search:

what are the properties of an object in space for orbital mechanics computations?

About 11,000,000 search results
Basics of Space Flight: Orbital Mechanics - braeunig.us
In general, three observations of an object in orbit are required to calculate the six orbital elements. Two other quantities often used to describe orbits are period and true anomaly. Period, P, is the length of time required for a satellite to complete one orbit.
www.braeunig.us/space/orbmech.htm
Basics of Space Flight: Orbital Mechanics - braeunig.us
People also ask
How do you calculate an orbit?
What is the difference between osculating elements and computed orbits?
What is orbital dynamics?
What is orbital mechanics?
phys.libretexts.org › Bookshelves › Astronomy13.1: Introduction to Calculating Orbital Elements
Mar 5, 2022 · To determine an orbit, we have to determine a set of six orbital elements. These are, as previously described, a, e, i, Ω, ω and T for a sensibly elliptic orbit; for an orbit of low eccentricity one generally substitutes an angle such as M 0, the mean anomaly at the epoch, for T. Thus we can calculate the orbit from six pieces of information.
oer.pressbooks.pub › lynnanegeorge › chapterChapter 1 – Orbital Basics – Introduction to Orbital Mechanics
The square of the orbital period, or the time it takes for a planet to complete one orbit, is directly proportional to the cube of the mean or average distance between the Sun and the planet. Kepler’s Third Law allows us to predict the orbit of any object in space travelling around a central body.
www.mathworks.com › content › damChapter 17 Orbits - MathWorks
Many mathematical models involve the dynamics of objects under the inﬂu-ence of both their mutual interaction and the surrounding environment. The objects might be planets, molecules, vehicles, or people. The ultimate goal of this chapter is to investigate the n-body problem in celestial mechanics, which models the dynamics
File Size: 405KB
Page Count: 19
geo.libretexts.org › Courses › University_of3.1: Orbital Mechanics - Geosciences LibreTexts
Feb 6, 2021 · For an object orbiting another object, Newton also observed that the orbiting object must be experiencing an acceleration because the velocity of the object is constantly changing (change direction, not speed, but this is still an acceleration).

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tahanson43206 · 2023-03-07 13:05:55

Update ....

GW Johnson has completed work on a course in elementary Orbital Mechanics, based upon his Orbital Mechanics Spreadsheet.

I have the documents in a folder, and have permission to share them with anyone who might have a serious interest in the subject. I am most definitely looking for persons who ware interested in learning a bit about Orbital Mechanics, and are willing to play the role of a test audience.

While I am able to catch spelling errors (of which there are very few) I have no idea how to evaluate the course material.

The long term goal (at least on MY part) is to find an audience for GW's work, and to establish a distribution channel of some kind.

There is a ** lot ** of free instructional material **out there** on the Internet, so I'm not sure where Dr. Johnson's work fits into that pantheon, but I'd hoping there ** is ** an opportunity.

(th)

tahanson43206 · 2023-03-07 15:52:18

This post is to record a first "best guess" estimate of a bearing for an orbital plane for a Refueling Station: 115 degrees SW from a point midway between Cuba and the Yucatan Peninsula in the Gulf of Mexico.

Using waypoints in Google Earth:

Midway 22 degrees 5 minutes 48 seconds North and 85 degrees 33 minutes 51 seconds West

SW point: 18 degrees 50 minutes 50 seconds North and 83 degrees 16 minutes 53 seconds West

A northern bearing of 145 degrees would correspond to a South facing bearing of 215 degrees

Update: ISS Keplerian Element set
ChatGPT: Certainly! Here is the Keplerian element set for the International Space Station as of March 8, 2023:

1 25544U 98067A 23067.85956405 .00003948 00000-0 90210-4 0 9995
2 25544 51.6428 75.2156 0006137 122.0916 238.3793 15.48950287305761

The elements are presented in the following order:

(th)

tahanson43206 · 2023-03-07 21:24:27

This web site provides animation showing both an orbit in blue, and a ground track in red.

https://observablehq.com/@jake-low/sate … visualizer

When I set the inclination to -35 degrees, the orbit laid down a ground track that seemed close to the 215 degrees that appears to be optimum for a flight between Cuba and the Yucatan Peninsula from the Gulf of Mexico.

Inclinations beween -51 degrees and -35 degrees all seem to work.

Update 2023/03/12 ... Further refinement of the Inclination for a Space Refueling Station seems to lean toward -29 degrees as better because that track lies North of South American, while preserving origin in the Gulf of Mexico, and passing through the strait between Cuba and the Yucatan Peninsula.

SearchTerm:Inclination of Orbital Plane for On Orbit Refueling Station

(th)

Mars_B4_Moon · 2023-03-12 06:33:59

Might also be relevant to the Ballistic Delivery thread

NASA Armstrong’s FOSS aces space test
https://www.aerotechnews.com/blog/2023/ … pace-test/
The FOSS team plans to take advantage of new technology and make the system smaller, simpler, and more robust. The researchers are also developing a new laser for the system and working towards making FOSS able to measure temperature and the levels of cryogenic fluids, such as those found in fuel tanks of space vehicles.

'LOFTID is an EDL demonstrator for large Mars surface payloads'

https://twitter.com/torybruno/status/15 … 0229395456

NASA tech twitter page LOFTID tech demonstration of an innovative inflatable heat shield

tahanson43206 · 2023-03-17 20:57:04

This is a follow up to post #168 about the NASA GMAT package...

SearchTerm:GMAT

I am attempting to set up this program on a Linux box.... the installation went seamlessly, but the installation package does not set up an icon on the desktop.

I learned how to start the program using the (relatively new) Application Start menu that is a feature of Ubuntu 22.04.

The program started, and immediately pointed out that I do not have MATLAB installed. I'm not likely to have MATLAB. It costs $149 per year for a home edition.

I commented out the configuration startup line for MATLAB and then the startup process complained about Python. I have version 3.10 of Python, and the GMAT startup procedure wants Python 3.9. I decided to stop work at that point, after downloading instructions to try to change GMAT configuration to look for 3.10.

***
Meanwhile, I finished careful study of Lesson 2 of the 3 lesson series offered by GW Johnson in the GW Johnson Postings topic. We don't seem to have anyone in the active forum community who is interested in learning how plan spacecraft flights, but I remain hopeful that there is someone "out there" who is interested, even if they are not a member of the forum. If there ** is ** such a person, see the Recruiting topic for procedure to become a member if that would be of interest to you.

Tomorrow I'll tackle Lesson 3, which is the introduction to Dr. Johnson's Texas Style Orbital Planning spreadsheet.

Update 20230419 ... libPythonInterface_py39 ... I have Python 3.10 The startup file may need to be adjusted to point to 310

(th)

New Mars Forums

Announcement

#151 2023-01-15 12:35:11

Re: Orbital Mechanics

#152 2023-01-29 06:50:42

Re: Orbital Mechanics

#153 2023-01-30 10:27:52

Re: Orbital Mechanics

#154 2023-02-01 21:01:22

Re: Orbital Mechanics

#155 2023-02-01 22:56:55

Re: Orbital Mechanics

#156 2023-02-19 21:16:37

Re: Orbital Mechanics

#157 2023-02-20 19:54:33

Re: Orbital Mechanics

#158 2023-02-27 11:44:06

Re: Orbital Mechanics

#159 2023-02-27 12:25:07

Re: Orbital Mechanics

#160 2023-02-28 07:13:41

Re: Orbital Mechanics

#161 2023-02-28 07:18:40

Re: Orbital Mechanics

#162 2023-02-28 09:15:53

Re: Orbital Mechanics

#163 2023-02-28 11:25:28

Re: Orbital Mechanics

#164 2023-02-28 15:48:54

Re: Orbital Mechanics

#165 2023-03-02 11:30:14

Re: Orbital Mechanics

#166 2023-03-02 11:59:44

Re: Orbital Mechanics

#167 2023-03-02 12:12:17

Re: Orbital Mechanics

#168 2023-03-02 12:15:30

Re: Orbital Mechanics

#169 2023-03-02 20:48:40

Re: Orbital Mechanics

#170 2023-03-03 11:41:43

Re: Orbital Mechanics

#171 2023-03-07 13:05:55

Re: Orbital Mechanics

#172 2023-03-07 15:52:18

Re: Orbital Mechanics

#173 2023-03-07 21:24:27

Re: Orbital Mechanics

#174 2023-03-12 06:33:59

Re: Orbital Mechanics

#175 2023-03-17 20:57:04

Re: Orbital Mechanics

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