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#1 2022-02-26 08:15:38

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Large Ship Orientation Navigation Pointing

Large Ship Prime is: Large scale colonization ship by RobertDyck

This topic is offered to collect knowledge, insights and best practices for maintaining orientation with respect to the Sun during flight

"Large Ship" is (arbitrarily) defined as 5,000 metric tons, for the purposes of calculations to be posted in this topic.

In response to a question from SpaceNut, RobertDyck published this specification:


RobertDyck wrote:

This is why we've spoken a lot about the need to orient the ship. The aft end must be precisely aligned with the Sun, not angled at all. The axis of rotation is a line perfectly pointed to the Sun. So as the ship rotates, the aft end is always perfectly toward the Sun. Yes, that means the bow is not pointed in the direction of travel, but when ship is coasting does it matter?

If the bladder of the water wall extends down to the hull, but hull isogrid stiffener depth is 0.5" (12.7mm), and flooring thickness is 1/2" (12.7mm). That means the water wall extends 25.4mm below the walking surface. Over 19 metres that allows an angle of 0.0766° without exposing passengers to radiation.

With the aft side of the face of the ring perfectly perpendicular to the Sun, that provides full Sun so full solar power.

A diagram showing Large Ship (Prime) in flight would be a worth while addition to this topic.

(th)

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#2 2022-02-26 12:33:33

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,310

Re: Large Ship Orientation Navigation Pointing

RobertDyck wrote:

This is why we've spoken a lot about the need to orient the ship. The aft end must be precisely aligned with the Sun, not angled at all. The axis of rotation is a line perfectly pointed to the Sun. So as the ship rotates, the aft end is always perfectly toward the Sun. Yes, that means the bow is not pointed in the direction of travel, but when ship is coasting does it matter?

If the bladder of the water wall extends down to the hull, but hull isogrid stiffener depth is 0.5" (12.7mm), and flooring thickness is 1/2" (12.7mm). That means the water wall extends 25.4mm below the walking surface. Over 19 metres that allows an angle of 0.0766° without exposing passengers to radiation.

With the aft side of the face of the ring perfectly perpendicular to the Sun, that provides full Sun so full solar power.


Uq9F6Sb.png

conjunction-class-mission.png

So lay the end of the hub on the sun and roll along the line keeping the end pinned at the sun.

Normally we use a siting star to hold course as true but sin we are rotating that may prove much harder to do.

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#3 2022-02-26 17:59:31

Quaoar
Member
Registered: 2013-12-13
Posts: 652

Re: Large Ship Orientation Navigation Pointing

SpaceNut wrote:
RobertDyck wrote:

This is why we've spoken a lot about the need to orient the ship. The aft end must be precisely aligned with the Sun, not angled at all. The axis of rotation is a line perfectly pointed to the Sun. So as the ship rotates, the aft end is always perfectly toward the Sun. Yes, that means the bow is not pointed in the direction of travel, but when ship is coasting does it matter?

If the bladder of the water wall extends down to the hull, but hull isogrid stiffener depth is 0.5" (12.7mm), and flooring thickness is 1/2" (12.7mm). That means the water wall extends 25.4mm below the walking surface. Over 19 metres that allows an angle of 0.0766° without exposing passengers to radiation.

With the aft side of the face of the ring perfectly perpendicular to the Sun, that provides full Sun so full solar power.


https://i.imgur.com/Uq9F6Sb.png

https://marsbase.org/sites/default/medi … ission.png

So lay the end of the hub on the sun and roll along the line keeping the end pinned at the sun.

Normally we use a siting star to hold course as true but sin we are rotating that may prove much harder to do.


The gyroscopic effect forces the rotation axis to maintain the same inclination during the travel, so it may be very difficult to keep the aft end aligned with the Sun while the ship move along her orbit: if you use the RCS it will generate a precession movement.
Why not to keep the rotation axis perpendicular to the orbital plane? In this case we can have a communication antenna mounted on a controrotating axis that remains aligned with Earth, a controrotating solar panel always perpendicular to the Sun (or as an alternative a circular solar panel mounted on the hull of the ring) and a circular corona radiator mounted at the equator of the ring (like the one of the habitat Kalpana One) parallel to the orbital plane.

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#4 2022-02-26 18:11:17

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship Orientation Navigation Pointing

For Quaoar re question in post #3

If you ever get a chance to read the Large Ship topic from the beginning, you will find answers to many questions.

In a recent post, RobertDyck just reminded SpaceNut that the Sun point is to keep the radiation shielding for the passenger ring between the Sun and the passengers.

Regarding pointing during rotation...

An option is to apply thrust when the ship is aligned with the center of the Sun, and the thrust vector to Mars coincides with that direction.  Whether this ever happens in real Universe orbital mechanics is for someone else to determine.

RobertDyck has proposed to apply pointing thrust at 90 degrees from the desired direction.  This subject is covered in detail in the Large Ship topic, if you ever find time to read it.

With recent questions, we are covering old ground.

(th)

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#5 2022-02-27 04:30:40

Quaoar
Member
Registered: 2013-12-13
Posts: 652

Re: Large Ship Orientation Navigation Pointing

tahanson43206 wrote:

For Quaoar re question in post #3

If you ever get a chance to read the Large Ship topic from the beginning, you will find answers to many questions.

In a recent post, RobertDyck just reminded SpaceNut that the Sun point is to keep the radiation shielding for the passenger ring between the Sun and the passengers. (th)


I read it, but I still have some doubt about the effectiveness of a shadow shield in the aft end of the ship pointed toward the Sun. It may be OK with solar X-rays, but solar protons doesn't go perfectly straight radially: they spirals outward in the Sun magnetic field, so they can get around the shadow shield and reach the habitat from the side wall.

https://www.researchgate.net/figure/Sch … _331978260

That's the reason for why I prefer to keep the rotation axis perpendicular to the orbit plane.

tahanson43206 wrote:

Regarding pointing during rotation...

An option is to apply thrust when the ship is aligned with the center of the Sun, and the thrust vector to Mars coincides with that direction.  Whether this ever happens in real Universe orbital mechanics is for someone else to determine.

RobertDyck has proposed to apply pointing thrust at 90 degrees from the desired direction.  This subject is covered in detail in the Large Ship topic, if you ever find time to read it.

With recent questions, we are covering old ground.

(th)


Robert's proposal may work well  with a good RCS managment software, that starts a precession movement with a puff and cancels it with a second puff in the opposite direction when the ship has the right orientation.

Last edited by Quaoar (2022-02-27 05:16:58)

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#6 2022-02-27 06:21:54

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship Orientation Navigation Pointing

For Quaoar re 5

Thank you for your helpful addition to the topic.

I agree that the proposal of RobertDyck to position mass along the sun-facing side wall of the habitat, addresses part of the problem.

Your observation about particles arriving from directions not aligned perfectly with the center of the Sun seems right, and you've provided a reference to study.

The current work of SpaceNut in one of the Radiation topics (with your guidance for which we thank you) may help to address that problem.

Since ** this ** topic is about navigation and pointing, please keep an eye out for the kind of RCS management software needed for this application.

I am confident RobertDyck will pinch every penny he can, so avoiding brand new development of software to manage the flight of the ship will keep costs down.

While buying/leasing software is not ** always ** the cheapest/best solution, exceptions are (in my experience) very rare.

It is ** good ** to have your support of the Large Ship endeavor!  We (I'm speaking now of the Mars Society) will be representing our best efforts to the National Space Society on March 12th, so the more details we can have readily at hand for RobertDyck to handle questions, the better.

The audience will understand that the work of RobertDyck is published in a facility of the Mars Society, and with support and occasional contributions by members of the Society, as well as by non-member friends of the Society.

Edit a bit later: Quaoar, this topic is about navigation as well as pointing.  In GW Johnson, this forum is fortunate to have expertise in flight management (propulsion, ellipse planning, propellant requirements) but we do not currently have a member who is familiar with celestial navigation. 

If your circle of friends includes someone able to provide advice on where to point Large Ship when it makes one of GW Johnson's prescribed burns, that person would be most welcome to join the Large Ship team.

We know from experience with Apollo, that even lay people can perform celestial navigation when they are supported by a cast of thousands on Earth.  The Apollo astronaut navigator was able to point the vessel at a prescribed star, and to set up the automation to perform a burn for a prescribed period.  These skills, limited as they may have been, were sufficient to bring all the crews home safely, because the selection of the target star was worked out by the support team on Earth.

The large Ship navigator needs to be able to perform all those computations while in flight, without a support team on Earth, much as an airline pilot today plans the details of a flight from one airport to another without a ground support team.  The task of celestial navigation is far more difficult, of course, but modern computer systems are available to assist the celestial navigator.

If your (hypothetical) friend is willing to provide advice on how to acquire skills our (hypothetical) navigator will need, that advice could fit smoothly into this topic.

(th)

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#7 2022-02-27 08:26:03

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,852
Website

Re: Large Ship Orientation Navigation Pointing

tahanson43206 wrote:

I am confident RobertDyck will pinch every penny he can, so avoiding brand new development of software to manage the flight of the ship will keep costs down.

Some things you can't skip on. Navigation software will be custom. Based on everything we can find, but still custom.

Spare no expense! wink Just don't hire a relative with issues.
jpcast-johnhammond.jpg

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#8 2022-02-27 08:27:14

Quaoar
Member
Registered: 2013-12-13
Posts: 652

Re: Large Ship Orientation Navigation Pointing

tahanson43206 wrote:

For Quaoar re 5

Thank you for your helpful addition to the topic.

I agree that the proposal of RobertDyck to position mass along the sun-facing side wall of the habitat, addresses part of the problem.

Your observation about particles arriving from directions not aligned perfectly with the center of the Sun seems right, and you've provided a reference to study.

The current work of SpaceNut in one of the Radiation topics (with your guidance for which we thank you) may help to address that problem.

Since ** this ** topic is about navigation and pointing, please keep an eye out for the kind of RCS management software needed for this application.

I am confident RobertDyck will pinch every penny he can, so avoiding brand new development of software to manage the flight of the ship will keep costs down.

While buying/leasing software is not ** always ** the cheapest/best solution, exceptions are (in my experience) very rare.

It is ** good ** to have your support of the Large Ship endeavor!  We (I'm speaking now of the Mars Society) will be representing our best efforts to the National Space Society on March 12th, so the more details we can have readily at hand for RobertDyck to handle questions, the better.

The audience will understand that the work of RobertDyck is published in a facility of the Mars Society, and with support and occasional contributions by members of the Society, as well as by non-member friends of the Society.

Edit a bit later: Quaoar, this topic is about navigation as well as pointing.  In GW Johnson, this forum is fortunate to have expertise in flight management (propulsion, ellipse planning, propellant requirements) but we do not currently have a member who is familiar with celestial navigation. 

If your circle of friends includes someone able to provide advice on where to point Large Ship when it makes one of GW Johnson's prescribed burns, that person would be most welcome to join the Large Ship team.

We know from experience with Apollo, that even lay people can perform celestial navigation when they are supported by a cast of thousands on Earth.  The Apollo astronaut navigator was able to point the vessel at a prescribed star, and to set up the automation to perform a burn for a prescribed period.  These skills, limited as they may have been, were sufficient to bring all the crews home safely, because the selection of the target star was worked out by the support team on Earth.

The large Ship navigator needs to be able to perform all those computations while in flight, without a support team on Earth, much as an airline pilot today plans the details of a flight from one airport to another without a ground support team.  The task of celestial navigation is far more difficult, of course, but modern computer systems are available to assist the celestial navigator.

If your (hypothetical) friend is willing to provide advice on how to acquire skills our (hypothetical) navigator will need, that advice could fit smoothly into this topic.

(th)

At the Apollo times there was a little army of engineers who made the calculation with slide rules, but now it wouldn't be difficult to put in the spaceship a PC with a good three body software for accurate celestial navigation. I will ask to a friend which kind of software may be more fitted for this task.

For RCS management I think the best solution is a self learning neural network software.

Last edited by Quaoar (2022-02-27 08:35:26)

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#9 2022-02-27 08:44:27

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship Orientation Navigation Pointing

For Quaoar re #8

I like your suggestion of using a modern neural network to manage the ship orientation and stability issues.

Regarding your view in Post #7, that all navigation software must be custom, I am disappointed if that is the case.

Humans have known how to perform celestial navigation for many decades now.

Your memory of the Apollo period is slightly dated ... the women who performed the celestial navigation for the first US space flights used hand calculators.  Eventually computers were brought in, but John Glenn famously requested flight plans by the women who'd proven so reliable.  I have made a mental note to add the name of the woman who led the "computing" team for NASA.  Her name deserves to be remembered by members of NewMars forum, and such non-member readers as we may have.

There is absolutely NO reason whatsoever that celestial navigation cannot be commoditized and delivered on a smart phone. The equations have been known for MANY years, and computational techniques to deliver precise pointing are well known to practitioners in (by now) many countries.

The development of such an app could be (and i hope soon WILL be) turned into an exercise in a computing text book.

(th)

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#10 2022-02-27 08:45:40

RobertDyck
Moderator
From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,852
Website

Re: Large Ship Orientation Navigation Pointing

Remember I said the ship would have control moment gyros. They're more energy efficient than momentum wheels, important for a ship this size. That means small changes of orientation can be done without RCS propellant.

The spinning ship acts as a top or very large gyro. When turning a gyro like that, you apply thrust 90° to the direction of rotation desired. I posted about the theory about that, the math to explain why it works. I believe this can be done with procedural software, neural net software is not necessary. Yes, you absolutely would want computer software, this ship will require fly-by-wire computer software to make it understandable to a pilot. But it won't require neural nets.

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