Orbital Mechanics

SpaceNut · 2019-12-21 21:21:16

SpaceNut wrote:

http://www.spacedaily.com/reports/Scien … m_999.html
Scientists closer to solving Newton's 'three-body problem'
Newton's laws of motion, nor any physical laws, explain the movements of three bodies in orbit.

http://www.spacedaily.com/reports/Hebre … m_999.html

tahanson43206 · 2020-01-30 18:54:57

Here is a web site that appears to date to 2018 ....

The comments published on the site seem favorable.

I'd be interested in any comments that more knowledgeable forum members might have.

https://transfercalculator.com/credits/

(th)

elderflower · 2020-02-11 12:26:17

We rarely need to consider the third body for our Mars or Moon, or even large asteroid expeditions, due to the fact that our space vehicles are very small in comparison with these bodies and with Earth. This means that the ship has a negligible effect on the first and second bodies.

SpaceNut · 2020-06-22 19:37:00

elderflower wrote:

GW Could the Mars performance of Starship be improved with a fly by of the moon?

tahanson43206 wrote:

For elderflower re #24
Bingo! Thanks for this (most definitely) outside-the-box thinking!
I have not read everything written on this subject by a long shot, but I have ** never ** heard this idea mentioned before.
I hope it will turn out to have some potential.
For example ... we have an immediate potential need ... if the Perseverance rover launch should be delayed past the optimum launch window, perhaps the lunar flyby concept could be helpful in making up lost time.
I assume any additional velocity provided by the gravitational assist would have to be dealt with at the Mars end, so there would be trade-offs.
On the other hand, perhaps ** less ** fuel would be needed on the outbound leg if the Moon is able to provide assistance.
I'm looking forward to seeing GW Johnson's evaluation, either way!
(th)

SpaceNut · 2020-06-22 19:38:28

SpaceNut wrote:

The moon allows for a topping off of fuel tanks with lunar oxygen but is a problem for targeting the mars system with additional speed as now you need even more fuel to slow down...

tahanson43206 wrote:

For SpaceNut re elderflower's suggestion ...
The idea of gaining speed by swinging by the Moon on the way to Mars probably would be a better fit in the Orbital Mechanics topic.
As you know, a vehicle swinging by the Moon to gain momentum would not have time to do much refueling.
I am hoping GW Johnson will be willing to take a look at the suggestion.
It is possible the mass of the Moon is insufficient to make much of a difference, but I think it is well worth investigating.
(th)

SpaceNut · 2020-06-22 19:39:00

The earth’s orbital speed is 107200 km/h. If we add a change of dV of 15480 km/h, which is the amount needed to get to a Mars Transfer Orbit, we get 122680 km/h.

The total requirement to land on Mars from the Moon is the sum of the lunar escape velocity and the Mars Insertion Orbit. That is 2.8+0.6 km/s, or 3.4 km/s. The fuel required to hit LEO from the moon is 2.74 km/s Thus, it does take more fuel to get to Mars than it does to get to Earth from the Moon.

1024px-MESSENGER_trajectory.svg_.png

https://www.physicsforums.com/threads/l … rs.425924/

https://www.quora.com/Can-you-slingshot … ars-faster

Part of the issue is orbital alignment but the small amount of payload versus the change in fuel requirement makes it a problem to use for manned flight.

SpaceNut · 2020-06-22 20:44:34

GW Johnson wrote:

I can do more-conventional orbits, but not gravity assists. I am not an expert in orbital mechanics. And I have no software that does orbits. I just do it essentially pencil and paper. Sorry.
GW

https://en.wikipedia.org/wiki/Gravity_assist

tahanson43206 · 2020-06-22 20:55:45

For SpaceNut ... thanks for moving elderflower's interesting idea to the Orbital Mechanics topic!

For GW Johnson ... thanks for clarifying that this question needs to be investigated further afield (literally and figuratively)

Here is an encouraging Google search:

Multiple Gravity Assist from Moon to reach Mars - Space ...space.stackexchange.com › questions › multiple-gravity...
Apr 12, 2016 - Multiple Gravity Assist from Moon to reach Mars · orbital-mechanics mars the-moon orbit gravity-assist. How effective can gravity assists from the ...
Gravity assist for manned travel - Space Exploration Stack ...
Jul 31, 2013
Can we significantly reduce entry velocity with this method by ...
Dec 24, 2017
More results from space.stackexchange.com
1 answer
Orbital Mechanics of Gravitational Slingshots 1 Introduction 2 ...symbolaris.com › course › fcps16 › projects › amoran
PDF
May 1, 2016 - Fig 1: Gravitational Slingshot Speed Changes (Gravity assist, n.d.) ... Utilizing the Moon as a gravitational slingshot to get to Mars will be a key ...

Those citations are from four years ago ... The computer I'm on at the moment can't reach them, but I'm posting the citations in case someone else wants to pursue it.

For SpaceNut re #56 .... thanks for the interesting graphic and notes on Deep Space Maneuvers and multiple fly-bys in the inner solar system.

I'm looking forward to seeing if the Moon has any capability to shorten travel time for Mars bound travelers.

My guess is that if there were a substantial benefit, NASA would be using it already.

(th)

SpaceNut · 2020-06-22 21:21:57

Last link in post 56 but here is another question that is answered in this one
https://www.quora.com/Why-not-use-Earth … et-to-Mars

https://www-istp.gsfc.nasa.gov/stargaze/Smars1.htm

tahanson43206 · 2020-06-22 22:32:32

For SpaceNut re #59

The NASA web site is a good reference for explaining why a trip to Mars will (most likely) take 8 and a half months.

The quora site you found has several answers that sort of addressed the question, but (in my opinion) fell short.

The definitive answer to elderflower's question is that it could be done, but the savings are barely worth the trouble.

https://space.stackexchange.com/questio … reach-mars

One aspect of the extended discussion in stackexchange is that if you had lots and lots of time, and very accurate navigation equipment, you might be able to achieve a Mars connection with almost no expenditure of fuel by doing multiple Earth fly-by operations.

(th)

GW Johnson · 2020-06-23 12:05:14

If you look at "2020 Starship/Superheavy Estimates for Mars" dated 21 June, over at "exrocketman", you will see that the trip to Mars can indeed be shorter than 8.5 months, but you will carry much less payload to have the mass ratio to do it, given the same inert and propellant masses. Go look at the article to see the pedigree of the data I used.

In that article, I compared the 8.5 month Hohmann transfer, with the 2-year period "abort orbit" often favored by Zubrin and some others. My best estimate of the one-way trip time is 4.26 months. The delta-vees are higher, so the payload gets cut roughly to 2/3, but it is flyable by my 2020 best estimates with Spacex's Starship, and at payloads high enough to remain attractive and practical.

That orbit must have its perihelion at Earth's orbit, with its aphelion far beyond Mars. That puts the fastest portion of the orbit in the place where you use it for your transits to and from Mars. That aphelion for a 2 year period falls nearly to the main asteroid belt. Its advantage other than a faster transfer is the ability to abort the entry at Mars, and do a free return to Earth. This only works if the transfer orbit period is an exact integer multiple of 1 year, because otherwise the Earth is NOT there when you reach perihelion.

My best 2020 estimate for what the Starship/Superheavy can put into LEO is max 149 metric tons of payload. The Mars estimate article puts max Starship payload from LEO to Mars at 284 metric tons on an 8.5 month Hohmann trajectory (at average Earth and Mars distances from the sun. On the 2-year abort orbit with the 4.26 month faster trip, that max payload calculates at 197 tons.

Both numbers deliverable to Mars are bigger than what Starship/Superheavy can reach LEO with, I must point out! You will note that NO ONE has been talking about transferring payload mass to a Starship in LEO! But, such would have to be done, to send the numbers I found to Mars.

Now I also looked at Starship stopping in low Mars orbit, then deorbiting and landing on Mars. To my surprise, I found it could actually barely accomplish this, from the Hohmann transfer, but with only 78 metric tons max payload on board. That's about half what Starship can reach LEO with, and about a quarter of what it could take to Mars on the slow Hohmann trajectory. This same scenario fell almost 22 tons of propellant short, with zero (!!!) payload, from the faster trajectory option! That would be either a crash upon landing, or being permanently stranded in orbit. Let's just say Starship was not envisioned to operate this way, and handling such a scenario is definitely not included in any of the design concepts we have seen so far.

None of this involves any gravity assist maneuvers, just plain transfer orbits. It's calculated using the pencil-and-paper-type stuff that I know, just assisted by a spreadsheet. What I have seen of gravity-assist maneuvers with unmanned probes in years past says: you can get the higher speed, but at the cost of greatly increased flight times flying here-and-there trying to get that speed. Whether such applies to lunar flybys, I just dunno.

That's the best I know.

GW

Last edited by GW Johnson (2020-06-23 12:22:32)

tahanson43206 · 2020-06-23 12:31:04

For GW Johnson addition to Orbital Mechanics topic Post #61

SearchTerm:MarsFastEllipse
SearchTerm:HohmannTransferAlternative

Thank you for the reminder of your work on the faster trip design you'd reported earlier.

This is a good time, and a perfect topic, to re-post.

The "free" return in one (Earth) year would surely be attractive to mission planners with human lives at stake.

I'd like to (try to) encourage you to combine this design for flight with your related (but separate) work on design of an expedition with a main "ship" and with multiple landers (or at least multiple landings).

What I am thinking of is an expedition consisting of multiple modules and vehicles, designed to make that one year loop so that the Mars exploration components drop off for a staging base at Phobos while the main vessel continues on its trajectory. The main vessel could perform data collection for the expedition as well as a substantial amount of remote machine operation to support the onsite crew.

There is NO reason that I can see why this has to be considered as one vehicle trying to do everything at once.

It would seem much more reasonable for this to be planned as a global undertaking with multiple vehicles contributed by multiple nations.

I don't see a need for assumptions of a lack of useful material (such as water) to be delivered to LEO for addition to the expedition manifest.

Water can be used for biological purposes, but it can be electrolyzed using solar power and then used for all sorts of things, including propulsion, life support and onboard fuel cell power generation.

You may have already created a table of launch dates for which your one(Earth)year orbit is ideal.

Such a table would make an interesting addition to this topic!

Edit#1: In hopes of stimulating your thinking further along these lines, I'm offering the suggestion of ** two ** main vessels designed from the outset to (a) deliver crew and vehicles to Phobos base using the fast flight trajectory and (b) another designed to swing by Mars on the return home. The expedition crew could have an agreeably short stay in the vicinity of Mars, depending upon what your analysis of ideal flights reveals.

The return vessel/expedition would depart first, so that it is due to arrive at Mars after the outbound vessel/expedition has dropped off the astronauts and vehicles for a short stay. I would think that an Earth month would be about as long as would be needed to complete a comprehensive set of Mars landings.

In that scenario, the longest time anyone would spend away from Earth would be one Earth year. The landing team members would benefit from the planning to clock only 9 Earth months away from Earth.

(th)

Last edited by tahanson43206 (2020-06-23 12:47:03)

GW Johnson · 2020-06-24 09:04:05

I don't have all the data tables you mentioned. I did the fast-transfer//2-yr-period transfer orbit with a perihelion distance of 150 million km (same as average Earth distance), and an aphelion distance of 321 million km. Their sum is 2a for the transfer ellipse, and that a = 235 million km corresponds exactly to 2.00 years period. All I did was solve the period equation for "a" at 2 years. The sum 2a = Rper + Rapo is the width of an elliptical orbit, from min to max distance.

The fast transit orbit to Mars itself and associated velocity math is sketched not-to-scale in figures 5 and 6 of "Interplanetary Trajectories and Requirements" dated 21 November 2019, over at "exrocketman". The mission launches, then gets off to visit Mars on one side, then gets back on on the other side to return to Earth. The sum of the two transits plus the time on Mars MUST sum to 2 years, the period of the orbit being used. There is no table, there is only that reasoning.

I would point out that "a" for Ceres is 414 million km, while Vesta is 353 million km. Those are average distances, but their orbits are significantly eccentric. The 2-year period abort orbit's aphelion is very nearly to the main asteroid belt. That abort orbit is essentially a Hohmann transfer orbit from Earth to very near the inner edge of the asteroid belt. I did look at a 2.5 year ellipse (no abort there) and a 3 year year ellipse (another, longer abort orbit). Those aphelions fall in or at the far edge of the asteroid belt, at 400 million km and 467 million km. Pallas gets as close as 292 million km, while Juno gets as far away as 512 million km.

What that says is your orbit transport that stays on the fast transfer ellipse to Mars might visit some asteroids as well. Especially on that 3-year orbit. It would be difficult to rendezvous, but an unmanned lander probe or two or three might be sent. Just an odd thought.

So, like I said elsewhere, I do this pencil-and-paper style. There is no code generating data tables here.

GW

Last edited by GW Johnson (2020-06-24 09:23:33)

tahanson43206 · 2020-06-24 10:18:05

For GW Johnson re #63

For what must be the umpteenth time, I am regretting my inability (so far for sure) to invite a local aerospace engineering prof (and as many students as might be interested) to take part in discussions here. The non-academic environment of an Internet forum is ** way ** too risky for a person in the early stages of a career, which coincides with when that person would be most helpful.

My interests in the subject are not an adequate substitute for what having a cohort of young folks on hand to interact with you would provide.

That said, I will undertake to keep your posts flowing as best I can. Perhaps a breakthrough will occur.

There are plenty of other forum members who can expose these discussions to a wider audience. Heck, there is a daily influx of spammers who might accidentally include someone of substance << grin >> I admit that seems doubtful, but there are 7 billion of us.

Restating my question (which got sidetracked with other important items):

Can you design an expedition concept in which your "fast" delivery of astronauts to Mars is built to coincide with a previously launched vehicle that will swing by Mars one (Earth) month later, to pick them up for a fast flight home?

In my earlier post, I was imagining that the bulk of the human crew would stay with the outbound vehicle in order to provide electronic/digital support for the Mars expedition crew who would be based on Phobos (for psychological reasons in support of an international effort).

The return vehicle need not necessarily have a human crew at all. It could be launched in advance to swing by Mars an (Earth) month after the human crew arrives at Phobos.

Something else I'm trying to discern from your concept, is to what extent it reduces dependence upon the Hohmann transfer timing that is standard thinking today.

As I understand current thinking, the (every two years or so) proximity of Mars and Earth provides a least cost solution to the transfer problem.

Would your concept lend itself to greater flexibility for mission planners?

***
Question ... are any of the folks you've signed up as followers potentially capable of assisting with the massive challenge of planning an international expedition along the lines we've been discussing here?

It bears remembering that the Apollo missions were supported by hundreds of thousands of people over a decade or so. A mission plan to Mars should require a comparable number of participants, with the additional feature of international cooperation and collaboration.

(th)

Last edited by tahanson43206 (2020-06-24 10:18:39)

GW Johnson · 2020-06-24 11:47:02

Tahanson 43206:

To answer your question about followers: I've looked at the identity of those on "exrocketman". Almost none struck as the type who might be Mars mission planners, but I could be wrong. There is one with the handle "qraal" who used to be a correspondent on these NewMars forums. I haven't seen him participating here for a few years, though.

I'm not expert enough in orbital mechanics to answer your question about any flexibility with the fast transfer ellipses. To the best of my knowledge, the Earth departure and Mars arrival (and Mars departure and Earth arrival) events must be "exactly" timed, same as for simple Hohmann transfer. The difference is that with fast transit, you can use both sides of the very same orbit for your transits to and from Mars. You cannot do that with Hohmann, you must wait 26 months from launch to be able to launch again.

There is a "window" for launch when the planets line up. But, I do not know how long it is, or how to estimate it. That's way beyond my skill level and my tools for orbital mechanics.

EDIT UPDATE 6-26-2020: things I have seen in news items about the upcoming Mars 2020 launch indicate the "launch window" to Mars is about 3 weeks long at most.

I have thought about lunar flyby gravity assist. I don't know for sure, and gravity assist is also way beyond my skill level and tools, but I'm beginning to suspect (or hope) that some effect could be had without waiting for years, since the basic flight time to the moon is only about 3 days. As long as you do whatever you do on the outbound leg from Earth, it shouldn't add flight time to your trajectory. But if you wait for looping about a big ellipse returning to the moon for your assist, it will add something like the period of your ellipse.

The only other outfit I can suggest would be the aerospace engineering & engineering mechanics department in the Cockrell School of Engineering at UT Austin. I am an alumnus of theirs from half a century ago. None are left that I knew then, but sometimes an alumni name can get you a hearing.

Y'all keep us in your thoughts. My wife is sick, with the "wrong" symptoms. I had to take her to get tested for coronavirus. We won't get the results back until Friday-ish. But if she has it, I have it. If that proves to be the case, I will be "scarce" for a while. Assuming she and I survive at all.

GW

Last edited by GW Johnson (2020-06-26 08:45:08)

SpaceNut · 2020-06-24 17:43:21

Sorry GW, to hear that you wife is ill and that while it might not be its still troubling to not know without a test. Even if the test comes back negative with the error rates a follow up test is advised if you still are not getting any better....
I know that KBD512 is also in a guarding mode for his wife's health as well.

GW Johnson · 2020-06-25 11:43:04

We got the results back today: negative. That is a relief. Now we can chase the other possible causes of her illness, without so much worry about dying.

GW

SpaceNut · 2020-06-25 16:35:45

Stand guard as this virus is sneaky.

Have seen while researching that a 20% payload shift happens with the boost of speed but for the mars end of that equation for mass and acceleration more force must be applied to slow the ship down for orbit or for landing and that means even more fuel that what you needed for the normal speed used to get to mars.

tahanson43206 · 2020-06-26 05:57:52

This topic is capable of holding substantial knowledge, written for an audience which varies in mathematical background.

I'd like to offer NewMars member/contributors an opportunity to follow NASA's lead, by creating posts that follow the historical record of the Apollo program.

NASA Names Headquarters After 'Hidden Figure' Mary W ...www.nasa.gov › press-release › nasa-names-headquarte...
2 days ago - NASA Administrator Jim Bridenstine announced Wednesday the agency's headquarters building in Washington, D.C., will be named after Mary W. Jackson, the first African American female engineer at NASA.

The Apollo Moon flights all included impulse operations which were designed to influence the trajectory of the vehicle to leave Earth, circle the Moon, and return safely to Earth.

While details are what I am hoping to see as an outcome of this initiative, all impulse operations would have been calculated upon:

1) Knowledge of the location of the spacecraft
2) Knowledge of the mass of the spacecraft
3) Knowledge of the capability of the propulsion system to be used at a particular point
4) Knowledge of the direction in which the vehicle should be pointed (ie, guide star or object)
Edit#1:
5) Knowledge of the location of the Sun (sets frame for all other objects)
6) Knowledge of the location and motion of the Earth (primary influence until in field of Moon)
7) Knowledge of the location and motion of the Moon

The decisions arising from consideration of these elements (and no doubt others I'm not aware of) would include timing of the start of the impulse, duration of the impulse, and its strength if that is one of the control elements.

A decision to embark upon an historical review along these lines could lead to an outreach opportunity.

Edit#2:
Wikipedia and other knowledge repositories could be "partners" in this undertaking. The key element that sets this forum apart from Wikipedia is the potential opportunity for interaction with readers. I would envision a primary set of posts that would be managed by the forum (ie, SpaceNut) with input by subject matter experts, supplemented by as many voluntary posts as may arise as the primary material is updated.

Ideally, a serious student of whatever material is assembled in this topic should be able to plan a trip between Earth (LEO) and any Solar System body. I expect software tools to facilitate this capability to be one of the outcomes.

(th)

Last edited by tahanson43206 (2020-06-26 10:43:14)

GW Johnson · 2020-06-26 08:48:34

I updated post 65 above with the length of the launch window to Mars. I still cannot figure this for myself, but the news items about the upcoming Mars 2020 launch revealed the window to be about 3 weeks long at most. I suspect the limits have more to do with the propellant available in the specific vehicle than it does the orbital mechanics. That's out of a 26 month recurrence interval for the planets lining up correctly.

GW

SpaceNut · 2020-06-26 16:21:01

tahanson43206 wrote:

impulse operations would have been calculated upon:
1) Knowledge of the location of the spacecraft
2) Knowledge of the mass of the spacecraft
3) Knowledge of the capability of the propulsion system to be used at a particular point
4) Knowledge of the direction in which the vehicle should be pointed (ie, guide star or object)
Edit#1:
5) Knowledge of the location of the Sun (sets frame for all other objects)
6) Knowledge of the location and motion of the Earth (primary influence until in field of Moon)
7) Knowledge of the location and motion of the Moon

1] The use of triangulation
2] The mass of the ship changes with fuel use, atmospheric loss
3] The location and a table of time measurements are used to track speed
4] The guide star is the fixed point locator which is used separate from triangulation
5] Much like the reference star the sun is used as another fixed point
6] Using radio waves for the same point of reference with respect to the other system which is optics driven
7] The moon is both optical sensed by reflective reference points and as such radio is as well used to establish motion.

All are obtainable with accurate timing mechanisms, and computers through geometry...
Sure motion is not always a straight line or circular but we can create very multiple measurements the math to which calculates all..

tahanson43206 · 2020-06-26 22:01:43

This is an addition to (or follow up on) Post #69

For GW Johnson re #70 ... thanks for your update that the launch window for the Mars 2020 lander launch is 3 weeks long.

For SpaceNut re #71 ... thanks for your addition of ideas for planning a celestial navigation sequence. Your point about using radar for distance measurement is important. The Soviet moon landing system (as I remember the story) was planned to employ optical focus instead of radar. The astronaut would have employed a set of telescopes designed to converge as the surface of the Moon approached, so the astronaut could know how much thrust to demand from his engines. My understanding (at this point and in the absence of refreshers) is that the US landing system included radar distance and velocity measurement, as well as the fine tuning capability of optical viewing through the lander windows.

I asked Google for information about records that might exist for navigation planning for the Apollo 11 landing.

Search Results
Web results
Apollo 11 Flight Planwww.hq.nasa.gov › alsj
PDF
from the document, “Views from the CM and LM During the Flight of Apollo 11” ... (d) Two series of P23 cislunar navigation sightings, star/earth horizon, ... (b) Docked landing site landmark sighting (one set of sightings) ... During lunar orbit LM operations, the DSE will be used to record ... (FOR CSI CALCULATION ONLY).
People also ask
Who did the math for the moon landing?
Mathematician Katherine Johnson worked out how Apollo 11 astronauts would get to the moon by calculating the spacecraft's trajectory. Johnson, who is now 100 years old, was featured in the movie "Hidden Figures."Jul 20, 2019
Apollo 11: Women who made NASA's moon landing possible ...www.businessinsider.com › apollo-11-women-made-moo...
Search for: Who did the math for the moon landing?

***
Edit#1: Per Google ... Katherine Johnson (American mathematician) Date of death: February 24, 2000

Katherine Johnson - Wikipediaen.wikipedia.org › wiki › Katherine_Johnson
Jump to Personal life and death - Johnson died at a retirement home in Newport News on February 24, 2020, at age 101. Following her death, Jim Bridenstine, NASA's administrator, described her as "an American hero" and stated that "her pioneering legacy will never be forgotten."

***

Here is a link to a document dated April, 1969
https://web.mit.edu/digitalapollo/Docum … report.pdf

Apollo Guidance, Navigation and Control
A progress report
by David G. Hoag
MIT Instrumentation Laboratory
Cambridge 39, Massachusetts

This report appears to be 30 pages long. The distribution list is two pages long.

The report includes mention of inertial navigation systems onboard the Apollo spacecraft.

Such systems are cited in this listing from Google:

Search Results
Web results
Inertial Measurement Units : The hidden key to Apollo successwww.microcontrollertips.com › inertial-measurement-u...
Jul 9, 2019 - With the 50th anniversary of the Apollo manned lunar landing on July 16, 1969, ... is the role of precision guidance and navigation via a gyroscope-based inertial ... Draper designed and built the Space Inertial Reference Equipment ... As soon as the Apollo moon-mission goals were announced, Draper ...
Apollo Navigation, Guidance, and Control Systems - MITweb.mit.edu › Documents › Chapter6 › hoagprogreport
PDF
At the time this paper is written the Apollo program stands on the threshold of completing ... inertial measurement unit, the TMU, provides a measure of spacecraft attitude with ... space flight including 22.5 hours of equipment flight operation in the. LM. ... A number of aspects of significance of the Apollo navigation, I guidance ...
by DG Hoag - 1969 - Cited by 6 - Related articles
des ign survey of the apollo inertial subsystem - NTRS - NASAntrs.nasa.gov › archive › nasa › casi.ntrs.nasa.gov
PDF
In Apollo, the crew can also make navigation measurements for onboard determination of the ephemeris by making landmark or horizon direction sightings using a special optical system. The Apollo inertial equipment alignment is updated by star sightings with the same optical system.
by PF Jopling - 1970
Apollo Astronaut's Guidance and Navigation Course Notesklabs.org › history › history_docs › mit_docs
PDF
tion an.d IMU alignment purposes, The equipment for control of propu.lsion-rocket ... during several of the important phases of the Apollo mission will be explained. This will be ... The inertial guidance of space vehicles may be regarded as a.

(th)

Last edited by tahanson43206 (2020-06-27 07:05:42)

tahanson43206 · 2020-06-27 07:17:02

This is for GW Johnson ....

Item#1:

By any chance, would you be interested in supervising a series of posts that would focus upon the celestial navigation computations performed by the NASA team during Apollo 11?

What I have in mind is creating a framework based upon the impulse events that occurred on that flight, and then inviting persons who may have the required education, experience and spirit of generosity to re-create the thought process that led to the timing, orientation and duration of the impulse.

Your role, if you are willing to consider it, would be to keep an eye on the proceedings, and to pitch in to clarify things occasionally, when you feel comfortable doing so.

I trust that NASA (and other historians) have kept all the relevant documents, but whether they are available at this point is a question.

Item #2: We have an impulse event coming up in July, when the Mars 2020 rover sets "sail" for Mars

We (NewMars forum) have an opportunity (in conjunction with the study of the historical record of Apollo 11) to work out what the navigation team is facing as they plan the departure from LEO.

The first step (I imagine) is to plan the launch to LEO. While I would expect the launch to be due East to gain maximum benefit of the Earth's rotation, it might be adjusted North or South to set an orbital plane that would be advantageous when the time comes for the departure impulse.

Mars 2020 Perseverance Rover
The mission has a current launch date of 22 July 2020 at 13:35 UTC, where the positions of Earth and Mars are optimal for traveling to Mars. The rover is scheduled to land on Mars on 18 February 2021, with a planned surface mission of at least 1 Mars year (668 sols or 687 Earth days).
Space program: Mars Exploration Program
End date: 4 December 2012
Mars 2020 - Wikipedia

(th)

Last edited by tahanson43206 (2020-06-27 07:19:07)

SpaceNut · 2020-06-27 08:11:19

There is not only a duration of how long its open but time for window of daily launch attempt or the rocket to go in.
For the Perseverance rover, the launch windows will last approximately between 30 minutes and two hours, with a unique launch opportunity every five minutes. Of which there is the timing of west coast versus east as well for timing.

https://mars.nasa.gov/mars2020/timeline … h-windows/

https://www.space.com/4-mars-missions-o … aunch.html

Launch Window Analysis for Round Trip Mars Missions

tahanson43206 · 2020-06-27 08:54:50

For SpaceNut re #74

Impressive finds! The Launch Window Analysis was particularly detailed. While it was for the 1980's, I expect the overall appearance of the analysis would be similar for any time period.

Edit#1: The link below showed up when I asked Google about planning for the Apollo 11 flight.

https://catalog.archives.gov/id/6734365

The page that (should) shows up is from the hour of the Moon landing. The entire plan is available for viewing.

However, ** that ** plan would NOT contain the calculations and measurements that were used to decide when to make individual impulse actions.

Edit #2: Here is a link to an article written shortly after the death of Katherine Johnson. It provides perspective on the lasting value of her work, and it introduces a female mission planner who is (or was at the time of the article) working on Artemis. The current mission planner explained that modern complex mission plans are dependent upon powerful computer support. The problem of trying to land at the South Pole of the Moon was given as an example of such a complex mission.

https://www.wired.com/story/katherine-j … -the-moon/

Edit#3: I decided to ask the National Archives web site if there might be records of the work of Katherine Johnson. In all probability they were discarded as ephemera, but perhaps some of it might have been saved.

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!

Edit#4: Reply from National Archives

This message was automatically generated by the Inquire Form on our website
(https://www.archives.gov). If you wish to contact us again, please use our
Inquire Form at https://www.archives.gov/contact/.
Thank you for contacting the National Archives and Records Administration.
This message confirms that your inquiry (or inquiries) was received by the
National Archives on Saturday, June 27, 2020 - 3:00pm. We look forward to
serving your needs as soon as possible.
Please note that under certain circumstances, we may respond to different
portions of your inquiry with separate replies.
For more information on how we respond to customer inquiries, please visit
the National Archives website at
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Thank you for your submission.

(th)

Last edited by tahanson43206 (2020-06-27 13:42:25)

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