Orbital Mechanics

tahanson43206 · 2020-06-28 06:25:33

For GW Johnson re 2 year orbit plan and Aldrin Cycler

Your presentation on Blogspot developed the 2 year orbit concept you revealed here in greater detail.

By any chance, have you written up a comparison of your plan to the Aldrin Cycler concept (and it's many variations)? I note that your plan delivers a travel time of 4.26 months, compared to the longer Aldrin Cycler travel time of 4.87 months. Your plan would appear to be faster, with the distinct advantage over most alternatives of a safe return to Earth if stopping at Mars is not possible for some reason.

In another post, I inquired about the feasibility of setting up a return vehicle to pass by Mars a month after the expedition arrives there using your 2 year orbit concept. What I'm not clear on is if your orbit design only works when the planets are aligned in a certain way.

Edit#1: The Starry Night astronomy package comes in four flavors ... The $80 Enthusiast level includes orbit input.

Add & Edit Objects With The Orbit Editor

Presumably a student of orbital concepts for Mars / Earth transits could design an orbit, determine the element set needed, input that into the Starry Night program, and watch the behavior of the object with respect to Mars and the Earth using the speed-up feature.

This might be an inexpensive way to acquire a subset of the capability of the mission planners at NASA or SpaceX.

So! For GW Johnson ... can your 2 year orbit concept be written in Keplerian Orbital Elements?

I asked Google if there is anything available to convert to keplerian Orbital Element sets, and got back a (to me surprising) number of responses.

The search string I used was "orbit elements calculator".

Search Results
Web results
Convert between orbital elements and state vectorsorbitsimulator.com › formulas › OrbitalElements
This calculator converts between orbital elements and state vectors, also known as Cartesian coordinates. It is recommended that you set your prefered units ...
Orbital Elements Calculatorprotean.io
Is the argument of periapsis, meaning the angle from the line of the ascending node to the point at which the satellite is closest to focus of the orbit. It is defined ...
Orbital Mechanics Calculator: Calculator - Elaine Coeelainecoe.github.io › orbital-mechanics-calculator › cal...
Let's get started! Convert Earth-Centered Inertial (ECI) Cartesian Coordinates (State Vectors) to Keplerian Orbital Elements; More Coming ...
Effortlessly convert orbital elements to position and velocity ...janus.astro.umd.edu › orbits › elements › convertframe
Changing the Elements Help File. This program allows you to convert between orbital elements and position and velocity vectors in cartesian coordinates. The one ...
Orbital Elements - Ulysses - Cosmoswww.cosmos.esa.int › web › ulysses › orbital-elements
The Ulysses Orbit: Classical Orbital Elements ... Peter Duffett-Smith's book "Practical Astronomy with your Calculator" (3rd Edition, Cambridge, 1988), or on the ...
Orbit of a satellite Calculator - High accuracy calculation - keisankeisan.casio.com › exec › system
Calculates the orbital radius and period, and flight velocity from the orbital altitude.

Edit#2: I decided to follow up the idea of using Starry Night to evaluate Solar System mission designs. The ancient Backyard version of Starry Night I have included an editor to allow input of Keplerian orbital elements, but considering the time frame of that edition (ca 2000), it is not surprising (to me at least) that it didn't work properly. I am confident that in 20 years, the Starry Night company would have worked out whatever bugs might have existed.

Accordingly, I wrote to their Education division to ask if the current Enthusiast version can support evaluation of mission designs.

This inquiry may reveal a new line of business for the Starry Night corporation, or it may turn out you are already serving it, and I am simply unaware of it. The ** primary ** purpose of this inquiry is to confirm that the edit-add-keplerian-element-sets feature of Starry Night Enthusiast edition can be used to demonstrate the famous Aldrin Cycler plan for Earth-Mars-Earth transportation. The over arching purpose of this inquiry is discover if Starry Night Enthusiast edition is capable of assisting an instructor of orbital mechanics to provide a computer assistant for students to complete assignments.
Thanks for your Backyard version, which I have been using since (about) 2000. (th)

Edit#3: In re-reading the collection of citations for element set calculators, I was reminded that the orbit GW Johnson (and Buzz Aldrin) designed were ** Sun ** centric, so any software that would be useful for planning Solar System navigation would ** have ** to be Sun centric. I'm not at ** ALL ** confident the Starry Night implementation of the Add-Orbit Edit feature supports Sun based element sets.

Edit#4: This reply was received from the Education division of Starry Night:

Your submission was received. We will be in touch soon. Thanks!

(th)

Last edited by tahanson43206 (2020-06-28 12:42:09)

SpaceNut · 2020-06-28 08:37:21

Orbital resonance comes to mind when we say cycler... But part of the issue is control of speed as the loop changes distances. Its similar to free return as well.

The physics principle behind orbital resonance is similar in concept to pushing a child on a swing, where the orbit and the swing both have a natural frequency, and the other body doing the "pushing" will act in periodic repetition to have a cumulative effect on the motion. Orbital resonances greatly enhance the mutual gravitational influence of the bodies, i.e., their ability to alter or constrain each other's orbits.

https://en.wikipedia.org/wiki/Orbital_resonance
https://infogalactic.com/info/Orbital_resonance

http://semi.gurroa.cz/Astro/Orbital_Res … Cycles.pdf

https://starsdestination.blogspot.com/2 … clers.html

Nasa free return
https://ntrs.nasa.gov/archive/nasa/casi … 018049.pdf

GW Johnson · 2020-06-28 09:19:00

I'm no expert in orbital mechanics. I have never understood any of the "cycler" concepts, including Aldrin's, because I cannot see how any of them ever come close to Mars, except at very long-isolated intervals. That assumes orbit perihelion is at Earth's orbit, and the period is exactly 2 years, so that the Earth is always there at perihelion passage. The apohelion is out near the inner edge of the asteroid belt, and Mars's period is 688 days, not any sort of multiple of anything to do with the transfer orbit.

I may or may not have estimated the transit time to Mars correctly at the 4.26 months. I dunno, I am no expert, and this is by-hand stuff, not software. Period is controlled by the semi-major axis length "a", independent of the perihelion distance you select. If you select a perihelion inward of Earth's orbit, then more of your transit path is along the slower portion of your orbit, and you get a longer transit. But, I don't understand how you can make the Earth-orbit rendezvous every two years, unless that is your perihelion at Earth's orbit. Maybe there is a way, I dunno, but I do not understand how that might be done.

As I said, I'm no expert in orbital mechanics. But I do understand the basics.

My computer is on the fritz. I have no access to my data while using my wife's computer to correspond. So, I'm a bit crippled for a while.

GW

tahanson43206 · 2020-06-28 11:01:29

For SpaceNut re #77 .... thanks for links to Resonance topics.

For GW Johnson re #78 ...

First ... best wishes for finding a way to bring your trusty system back online!

Second, thanks for your engaging modesty about your two year orbit suggestion. It would be fun to (somehow) draw younger folks who are closer to the current state of the art into this forum, but I admit chances of that happening seem small. Still, as the recent appearance of LiveForever on the forum makes clear, folks who set up an ID years ago may suddenly decide a topic is of interest.

I am hoping the Starry Night folks decide to consider my mission planning suggestion for their software.

If their software can display object motion based upon Sun-centered Keplerian Orbital Element sets (which is not at all guaranteed) then I'd be interested in upgrading from my (nearly) 20 year old (and very reliable) copy of Backyard Starry Night.

What I can visualize (if the program can perform as described) is inserting various orbit designs (yours is of particular interest of course) and setting them into motion using the animation that Starry Night provides. ** That ** part of their program is one I have used extensively, to discovery when planets such as Mercury will be visible from my location.

From what little I've been able to glean from the Aldrin Cycler write-ups is that the ship's Navigator would ** really ** earn their Galactic Credits by having to perform exceedingly precise maneuvers during object encounters to keep the cycler headed for the next appointment.

From what I am able to pick up from your images in the blog, and your text on the 2 year orbit concept, is that the orbit is designed to ** always ** insure a safe return to Earth, but that the expedited travel time to Mars can only occur when Mars is in a specific location with respect to Earth. If that understanding is correct, then the orbit can be used no more frequently than the Hohmann design.

In an earlier post I had inquired about the feasibility of sending a return vehicle on one of your two year orbits ** ahead ** of the mission with astronauts, so that the earlier mission would be passing close to Mars a month after the astronauts arrive at Mars. However, if the mission plan you have designed can ONLY work once a Mars orbit, then sending the return vehicle ahead of the expedition would appear not to make sense.

There ** is ** another possibility ... the Two year orbit design could be launched ** any ** time (a vehicle without passengers) and just stopped in a position slightly above Mars' orbit, so that Mars trundles along and eventually catches up. This would put a return vehicle, fully loaded with supplies and fuel, as a resource available for retrieval by the expedition in case it is needed. If the resource is not needed for a safety return, it could be collected/commandeered for some other purpose.

Edit#1: After re-reading the above, I realized the return vehicle could be sent ** four ** years ahead ... it would complete a full two year cycle and pass by Earth just as the new expedition launches. The two could then travel in tandem, the one as backup for the other. Whether there is any advantage over just sending two vehicles is not clear, but at least it is a possibility.

(th)

Last edited by tahanson43206 (2020-06-28 11:06:31)

tahanson43206 · 2020-06-29 18:37:58

Here is a two part reply from Starry Night ...

Part 2

To follow up from the previous reply, our engineers wanted me to tell you that Starry Night will not perform the exact operation that you are seeking. They want to add it to the list of features for a future update.
Thank you again,
Michael
Simulation Curriculum
1-866-688-4175
mgoodman@simcur.com
Starry Night | SkySafari | Layered Earth | BeyondLabz

Part 1

Starry Night Pro (not Enthusiast) is used by JPL and NASA for purposes such as this but they have not provided all of the details.
Amazing that you are still using SN Backyard!
Thank you
Michael
Simulation Curriculum
1-866-688-4175
mgoodman@simcur.com
Starry Night | SkySafari | Layered Earth | BeyondLabz

(th)

Last edited by tahanson43206 (2020-06-29 18:39:35)

tahanson43206 · 2020-07-07 13:44:12

This very helpful reply just arrived from a representative of the National Archives:

Dear Mr. Hanson:
This is in response to your email to the National Archives regarding Katherine Johnson and Orbital Mechanics.
The records from NASA are part of RG 255; unfortunately, we have few records that identify the works of particular individual persons. You may want to take a look at these mission-specific catalog entries: RG 255 Search for MISSION REPORTS. Or, you can customize your own search in the advanced search feature of the catalog.
It is also possible that something relevant to your research may be with NASA records from the Johnson Space Center at our regional archive in Fort Worth, Texas. You can email them at ftworth.archives@nara.gov to inquire about their holdings.
We recommend searching WorldCat or other repositories to determine if other historians have already written on this subject.
It is important to note that all NARA Research Rooms were closed effective at the end of business on March 13, 2020 as a public health precaution due to the coronavirus, also known as COVID-19. Under standard circumstances, we would welcome you to visit our research room so you or your representative can examine and select documents relevant to your research. You could also hire a researcher to conduct research on your behalf. However, visiting is not an option at this time. For updates on the status of Research Rooms, please visit https://www.archives.gov/coronavirus.

Sincerely,
Cate Brennan
Textual Reference Branch (RR2RR)
National Archives at College Park

On Saturday, June 27, 2020 at 3:00:27 PM UTC-4, The National Archives and Records Administration via National Archives wrote:
Submitted on Saturday, June 27, 2020 - 3:00pm
Submitted by user: Anonymous
Submitted values are:
==Your Inquiry==
What is your reason for contacting us? Research
What type of records are you interested in? Federal Civilian
Agency Records (no personnel records after 1900)
Referring URL:
Tell us more.: This is an inquiry on behalf of a forum of the
Mars Society. The discussion topic is Orbital Mechanics, and the
specific focus is the work of Katherine Johnson. By any chance,
were the work papers she created while developing mission plans
for space flights preserved? Are you aware of anyone else having
researched this topic? For example, has anyone written a book
about the mathematics developed by Ms. Johnson? Thanks!
==Would you like us to send you a response?==
Would you like us to send you a response? Yes

(th)

SpaceNut · 2020-07-07 21:01:23

Spaceflight Simulator Wiki Building Mars Rockets

GW Johnson · 2020-07-09 12:19:16

This laptop has the bad habit of turning off its whatever-widget sees the internet from my home wi-fi setup. My rural internet service also has the bad habit of going down for no damned reason at all. I diagnose which is fault by whether my wife's computer sees the internet, and by whether our Roku device can see Netflix. 2 out 3 wins the vote.

Dell has a better reputation than that, but Microsoft hasn't been worth a damn since they invented that Windows 8 trash. And no version of Windows 10 is any better.

Net result: my computer is working, but I do NOT consider it reliable!

My old slide rule didn't do as much, but it NEVER EVER gave me any trouble.

GW

elderflower · 2020-07-12 04:16:14

this windows 10 machine is less effective and more difficult to operate than my wifes old windows 7 machine! Our 'phones are way better except in the matters of keyboards and screen sizes.

kbd512 · 2020-07-12 12:37:45

GW,

From what you describe, it sounds as if you have a power-save feature turned on that you may want to disable if you don't want your laptop to disconnect from your home's wireless router or internet gateway or dial-up modem. Although it's a minor point in the grand scheme of things if your computer doesn't work, your slide rule can't run billions of floating point calculations per second, either. That said, it sounds like you have a network connectivity issue, possibly the result of some factory default setting in the software. Windows 10 is also notorious for system imaging issues that both SpaceNut and I have had with our machines.

GW Johnson · 2020-07-26 10:42:26

Sorry I didn't reply sooner. I got some help over the phone from Geek Squad and luckily-enough got the issue fixed, at least for a while. I never did understand what was wrong, because folks good with this stuff, and I, do not share a dictionary. My poor understanding was some corrupted driver for something in the laptop. Whatever that means. Nothing was ever wrong with the wi-fi network.

GW

tahanson43206 · 2020-07-26 11:08:13

For GW Johnson re #86

Glad to hear you are back to whatever Windows 10 considers "normal" !!!

For kbd512 ... thanks for posting that interesting tip! Hopefully someone will find it useful down the road.

For SpaceNut ... GW Johnson reported calling Geek Squad. I'd like to suggest something like that is going to be needed in the My Hacienda community, and not just for digital infrastructure. The entire enterprise is going to be operating at an elevated level of technology tempo, and there are going to be very few times when (responsible) residents can relax. Children have always enjoyed a lack of awareness of danger, which their parents and guardians are busy trying to ward off. Visitors to Mars may enjoy a certain freedom from worry, due to complete and total lack of understanding of the thin veneer of civilization they'll find on Mars.

(th)

tahanson43206 · 2021-01-26 08:35:30

Inspired by GW Johnson's recent contributions to the Topic on Ballistic Delivery of Supplies to Mars, I offer the following challenge.

For Reference, GW Johnson's blog ExRocketman may contain solutions, or rather the tools capable of delivering solutions ...

For Orbital Mechanics topic ...

Is it possible to design a flight from Earth so that the arriving vessel will achieve orbit around Mars without any course corrections at Mars?

A Hohmann transfer is designed to place a spacecraft at Mars when Mars is there.

A Hohmann transfer orbit has a glaring and obvious deficiency.

The spacecraft that arrives at the location of Mars just when Mars arrives there is moving more slowly than Mars.

The difference is given by GW Johnson in Post: (to be supplied after lookup)

The velocity of Phobos in orbit around Mars is: 2.138 kms (per Google from Wikipedia)

Asking Google about the Hohmann transfer orbit:

From Wikipedia:

In the smaller circular orbit the speed is 7.73 km/s; in the larger one, 3.07 km/s. In the elliptical orbit in between the speed varies from 10.15 km/s at the perigee to 1.61 km/s at the apogee.
Hohmann transfer orbit - Wikipedia

In the quotation above, there is an illustration showing the orbit of Mars as 3.07 km/s.

Also in the quotation above, the velocity in LEO is given as 7.73 km/s

The vessel is accelerated from 7.73 to 10.15 km/s at departure from Earth, and it coasts to apogee to arrive when Mars is there.

The velocity of the vessel at apogee is given as 1.61 km/s at the moment it arrives at Mars.

However, as GW Johnson has pointed out on multiple occasions, Mars will be pulling on the vessel as it approaches.

If Mars were NOT pulling on the vessel, it would see Mars come up from behind at 3.07 - 1.61 or 1.46 km/s

In order to match orbital velocity with Mars, in the absence of gravitational force from Mars, the vessel would have to accelerate 1.46 km/s.

However, Mars ** is ** pulling on the vessel.

Is there a navigational technique that would cause Mars to pull the vessel into orbit (capture the vessel) without expenditure of energy by the vessel.

The example from Nature is that objects of various sizes are routinely captured by larger objects without expenditure of energy by the smaller one.

(th)

GW Johnson · 2021-01-27 20:43:59

Tahanson43206:

My calculations of Mar's orbital motion about the sun says its orbital velocity varies from a min of 21.964 km/s at its apohelion, through 24.121 km/s at its average distance, to a max of 26.490 km/s at its perihelion distance.

For a Hohmann trajectory figured at average Earth and Mars distances, the perihelion velocity is 33.4 km/s and the apohelion velocity is 22.4 km/s. Subtracting that apohelion velocity from the average Mars velocity gives you 1.72 km/s velocity of the spacecraft with respect to Mars "far" from Mars (meaning Mars hasn't yet pulled on the spacecraft with its gravity), after a 259 day one-way trip. The actual variation is from 1.59 km/s (both planets at min distance from the sun, a 235 day trip) to 1.86 km/s (both planets at max distance from the sun, a 286 day trip).

To figure the relative velocity "near" Mars (after Mars has pulled on it with its gravity), you need the escape velocity from Mars at the altitude you consider "near". For the surface out to low Mars orbit, this is pretty close to 5 km/s, while out at the distance of Phobos, this is only 3 km/s). You add the square of your "far" velocity and the square of appropriate escape velocity. Your "near" velocity is the square root of that sum.

Nowhere among those numbers do I see any of the numbers you quoted in post 88. That concerns me.

I do have calculations for "near" velocity at the orbit distance of Phobos. I put those in the referenced "exrocketman article, not here. You subtract Phobos's orbit velocity from that, for the velocity with respect to Phobos, but only for an intercept on the sunward side of Mars.

That plus the escape speed of Phobos is the estimate of impact velocity, if you just smash into the moon. It's the lower bound on your landing delta-vee requirement otherwise. There are some very stringent timing limitations in order to make that intercept dead center on the sunward side. So, doing this without a midcourse correction, and a final course correction as you draw near, seems unlikely in the extreme.

GW

Last edited by GW Johnson (2021-01-27 20:45:26)

tahanson43206 · 2021-01-27 21:45:56

For GW Johnson re #89

If something I found in Wikipedia concerns you, then it certainly concerns me.

There are at least two possibilities.... The more likely is that I copied something out of context. The less likely possibility (but still viable) is that the author was trying to over simplify a complex subject for a non-technical audience.

The least likely possibility is that the article was wrong, since there is a small army of volunteer editors picking over every article submitted to Wikipedia. I managed to secure a position as a very (very) minor fledgling editor, so I know first hand that anything posted on Wikipedia can be edited by an approved editor.

It's not a good time for me to try to find the original article, but I've made a mental note to try to find it.

This next is up to you (of course) but I'll leave open the possibility that if the article is indeed incorrect, or misleading, then it is possible to change it.

Any change made has to be defended when a higher order editor intervenes, so I would certainly not try something like that on my own.

***
Regarding the larger scope of the topic ... I would like to see a tool that can plan a flight to Mars (or Phobos in particular) that an average person (whatever that is) can use. My assumption is that modern computing hardware and software are up to the task of planning a burn to launch a vessel from Earth to a desired target situation at Mars. The assumption seems reasonable because several independent nation states appear to be able to plan and control flights that look as though they are going to be arriving at Mars, in addition to the ones that are already there, such as ones from India and the US, the Soviet Union and the European Union.

RobertDyck recently expressed interest in taking a look at the challenge of bringing such software into operation on behalf of members of this forum.

**** May I test your patience just a bit more?

In post #89, and in previous posts, you have said that the optimum location to intercept Phobos is on the "sunward" side of Mars.

I assume from that statement that Phobos is orbiting Mars roughly in the Solar Plane, and that it is consistently on the sunward side of the planet when it is moving "backward" with respect to the forward progress of Mars.

That situation may not be surprising to a person who knows more than I do. I'll attempt to find an article that describes the orbit of Phobos. It seems clear I have an incorrect mental image of that orbit.

(th)

GW Johnson · 2021-01-27 22:31:28

Phobos orbits Mars posigrade. Mars has axis inclination similar to Earth, so the plane of Phobos's orbit is not the plane of Mars's orbit about the sun. But it is not very far off, either. About 24 degrees off, if memory serves.

Looking down from very far, over Mars's north pole, toward the planet, you see Mars orbiting the sun counterclockwise. You also see Phobos orbiting Mars counterclockwise. Phobos is traveling in the same direction as Mars on the night side of Mars, and in the opposite direction on the sunward (day) side.

The spacecraft motion in its transfer ellipse is also counterclockwise viewed in this way. When the spacecraft reaches the vicinity of Mars, it is moving slower about the sun than Mars is, which is why Mars wants to "run over it from behind".

The "run-over" velocity relative to Phobos is higher on the night side where its velocity more-or-less adds to that of Mars, and lower on the sunward side, where its velocity more-or-less subtracts from that of Mars. Those really ought to be vector additions, but you would need Mars axis direction information to account for that.

I suspect the numbers from the wikipedia article were for something other than Mars, which would explain why they were different.

As for a tool by which to make calculations, you are welcome to a copy of the Excel spreadsheet that I used to support the "exrocketman" article(s). I just need to know where to email the file.

GW

Last edited by GW Johnson (2021-01-27 22:33:10)

tahanson43206 · 2021-01-28 07:47:19

For GW Johnson re #91

Thank you for your explanation of the nature of the orbits of Mars with respect to the Sun, and Phobos with respect to Mars!

SearchTerm:Phobos orbit explained by GW Johnson http://newmars.com/forums/viewtopic.php … 76#p176276

Thanks too, for considering another possibility for the Wikipedia copy-and-paste error.

Please send the spreadsheet to NewMarsMember * gmail.com

That way I'll have something to report there !!!

I am confident there is a trajectory from Earth (LEO) that delivers a spacecraft gently into the gravitational field of Phobos.

It seems clear that a means of making fine tuning adjustments of the trajectory as the vehicle approaches Mars are needed.

For cargo, and especially cargo having a nature above that of bulk materials, such as manufactured equipment, it might even be cost effective to deploy an automated tugboat equivalent to capture the package and guide it to a landing stage on Phobos.

Every day I watch ships making their way through the Panama Canal. That image of current mass cargo operations on Earth is a model for what I am confident will become routine on Mars. The residents of Mars WILL NOT tolerate random arrivals from Earth or anywhere else.

There will certainly be an extended period (such as right now) when anyone with the means can drop a payload anywhere on Mars without hindrance except for the natural forces at work in the Universe.

There will come a time when that freedom will be restricted. At that time, (it seems likely to me), flows of bulk materials and finished goods on the order of the Panama Canal today will occur at Phobos as Port of Entry for Mars.

For SpaceNut ... the text in this post departed from the topic ... please recommend a better place for it .... I'm like to keep this topic tightly focused on Orbital Mechanics, and I find I have drifted into trying to visualize human port operations on Phobos.

(th)

Calliban · 2021-01-28 12:05:06

The Wiki page on Cyclers shows some calculated Cycler orbits.
https://en.m.wikipedia.org/wiki/Mars_cycler

The idea is to have a space station on a fixed orbit that makes regular close approaches to both Earth and Mars. Relatively small taxi vehicles would be used to make the trip between each planet and the cycler. So in theory, at least for missikns carrying people, a cycler could save a great deal of propellant and a spaciohs, radiation shielded environment for the passengers. The downside is, that you may have to wait years for orbits of the Earth, Mars and cycler to line up in such a way that you can get on the cycler at one planet and depart at another, without being on the cycler for multiple orbits.

The Aldrin cycler is shown crossing both Earth and Mars orbits, with aphelion greater than 2AU and perihelion <1AU. This results in regular close approaches with both Earth and Mars. The downside is that substantial velocity change is needed by the taxi to match the orbit of the target planet. We could get around this problem by having a cycler with aphelion just inside Mars orbit and perihelion just outside Earth orbit. The problem then is that the cycler may only be in position for one trip every dozen or more years.

I believe that the solution is to use natural bodies with orbits already between Earth and Mars. We could use solar power and reaction mass from the bodies to adjust their orbits so that they are Earth and Mars grazing. We would need several such bodies if we were to be assured of the ability to journey between Earth and Mars in either direction every two years or so. I can think of a number of ways of making this economically attractive:

1) The cycler is composed of metal and silicate oxides. It could provide the oxygen needed for a breathable atmosphere.
2) The cycler could be a target for asteroid mining. Precious metals could be transported back to Earth and other materials transported to Earth or Mars orbit to support space manufacturing.
3) The cycler could employ greenhouses or algae tubes and would be a closed (or semi closed) life support system. Humans would need minimal supplies for the bulk of the trip.
4) The cycler could be used to visit multiple destinations. In the years between Earth - Mars transits, transits may be available to other Near Earth Asteroids. Hence the cycler could be a useful tool for colonisation of NEAs. Likewise, a Mars crossing cycler would make regular passes of main belt asteroids.

Last edited by Calliban (2021-01-28 12:16:23)

tahanson43206 · 2021-01-29 09:52:11

For Calliban re #93

Thank you for bringing Cyclers into this topic. I've inquired of SpaceNut if a topic dedicated to Cyclers might be appropriate for this forum. The Large Ship topic is constrained to a point-to-point flight plan.

It seems to me that a hybrid of SpaceX Starships for planetary activity, and the Cycler for human safety and comfort in transit is a way to gain the advantages of each and avoid the disadvantages.

Starships can certain perform the maneuvers needed to match orbits with Cyclers.

I am imagining Starships delivering passengers to Cyclers at Earth by matching velocity, and then riding along with the Cyclers to Mars, where they would reboard their passengers and descend to Mars.

I am definitely interested in finding out how viable the Cycler concept is for times away from the minimum distance orbit.

If a Cycler passed Earth on a voyage to Mars every Earth month, then the trip would be longer or shorter depending upon the position of Mars and Earth in their orbits.

Another question I have (in the absence of study of the proposed Cycler orbits) is where the Cyclers would be in the range of orbits between LEO and GEO. There is a risk of collision as the people of Earth add more and more satellites to the collection already in space around Earth.

(th)

tahanson43206 · 2021-01-29 09:53:49

Here is a new item about the UAE probe which will be first to reach Mars, of the set of three who set out from Earth last year.

https://www.msn.com/en-us/news/technolo … -ntp-feeds

Almost half of the spacecraft's fuel will be used to slow it down enough for the spacecraft to be captured by Mars' gravity and go into orbit.
By firing its thrusters for 30 minutes before reaching Mars, it will slow down from a speed of more than 75,185 miles per hour to 11,184 miles per hour.

If we have a UAE topic, a copy of the article could certainly go their.

The article is written for a general audience, but there are tiny hints of technical details here and there.

(th)

SpaceNut · 2021-01-29 18:54:42

Yes Hope is in Feb along with one from china and another is from the US.
The trouble with a cycler is we need to get fuel to it on every circling of the end points so as to be able to do the course as well as the angular changes to keep it in resonance. The ship that takes off from earth needs to be fast and will not orbit earth so as to catch up to the ship as it swings by as its going to be somewhat fast moving as it plunges back towards earth due to the suns pull.

GW Johnson · 2021-01-30 10:38:00

Tahanson43206:

In post 92, did you mean NewMarsMember@gmail.com? You typed NewMarsMember*gmail.com, and that is not an email address.

I am still writing up the user's manual for the orbital mechanics spreadsheet estimator. When that is done, I will send the Excel spreadsheet file and the word.doc user's manual.

GW

tahanson43206 · 2021-01-30 12:14:55

For GW Johnson re #97

Thank you for your reply, and for the update on your plans! This time (hopefully) I'm in a better situation to be able to focus on your work in this specialty.

Regarding the format of an email address in a post ... I am following the lead of SpaceNut, who is careful NEVER to write an email address out in full inside a post.

You appear to have gotten away with it, so for that, I tip my hat !!!

For SpaceNut ... can you add anything to this?

(th)

tahanson43206 · 2021-02-05 09:55:33

For GW Johnson ...

Thank you again for sending a copy of your orbits spreadsheet, and what appears (to my eye) to be a comprehensive guide to the spreadsheet, and for its use.

SpaceNut ... I'd like to suggest we think about how this gift can be turned into a tutorial that would have lasting value in the (somewhat unique) constraints of the forum environment.

An option for your consideration is to make two new topics:

1) Orbital Mechanics Tutorial
2) Orbital Mechanics Tutorial Peanut Gallery

The first would be a managed topic. Contents would be either directly from GW Johnson, or supervised by him.

The second would be where everyone else is encouraged to ask questions, make comments or suggestions, or go off into free association, as often happens in this forum.

Here is a sample of what might go into the Tutorial, in small packages:

From the Orbits spreadsheet prepared by GW Johnson
Cell A1
rough estimates of Spacex "Starship" performance on missions to Mars
From the documentation for the Orbits spreadsheet:
User Manual for Excel Spreadsheet Orbits.xlsx by G. W. Johnson 1-28-2021/2-3-2021
This spreadsheet is for making certain very useful estimates regarding orbital mechanics. It is not a trajectory simulator. It for making estimates and approximations. In general (with a few exceptions), cells have been highlighted yellow for required user inputs. Significant results are often (but not always) highlighted light blue or light green.

From a first glance, if a small part of the total body of work is delivered each day, it will take upwards of a year to complete the first draft of the tutorial.

Upon completion, it should be possible for a student to proceed from top to bottom of the tutorial, to recreate the spreadsheet on their own computer, and to make useful predictions by following the documentation and the examples.

(th)

GW Johnson · 2021-02-05 16:57:58

Tahanson43206:

Another thing I have that might be useful to others is my ballistic entry analysis. It's a spreadsheet that does the old 1955-vintage warhead re-entry motion analysis in an oversimplified 2-D Cartesian model, with an oversimplified "scale height" model of density versus altitude. I got my versus of it straight out of the Justus and Braun tome (who reported it as historical), and corrected a units conversion error they made in their version of the closed-form heat transfer correlations, going to metric from the original SAE units. (I corrected it by integrating the heating rates along the trajectory by numerical integration.) I got the stagnation heating rate correlation from an old reference in SAE units, and converted it to metric myself.

I have the spreadsheet file, and also a user's manual for it. While the model is oversimplified, it is amazing close, even when used for shallow trajectories instead of steep warhead trajectories. You just wrap the range coordinate around the Earth for its predictions. It's not "right", but it is "well in the ballpark". If you'd like, I can send you those, too.

And I have a whole lot of other stuff.

GW

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