Large scale colonization ship

tahanson43206 · 2022-01-06 13:40:23

For RobertDyck re #1050

Thanks for your reply regarding your (to me unfounded) dislike of (and refusal to provide to your passengers) iceberg lettuce.

I believe you have uncritically accepted the opinion of unqualified persons who claim to be "nutritionists".

You are surely not to be blamed for being taken in.

I asked Google for help with this, and confirmed:
1) iceberg lettuce is one of the most popular types of lettuce
2) it has superior shipping qualities.

however, the saving grace in this discussion is your mention of fiber.

Please publish your thinking about how you will provide to meet the fiber requirements for your passengers and crew with items they actually want to eat.

Your personal preferences for specific foods are one thing, and I don't discount their importance in shaping your world view.

However, you are providing for a large group to facilitate good health and psychological enrichment over two years. Your idea of enlisting your experienced friend is a good one and I hope you will be able to win his support.

One more thought ... using iceberg lettuce as a carrier for nourishing liquid flavors is apparently something you had not considered, or been exposed to.

Now you have.

(th)

RobertDyck · 2022-01-06 13:59:54

The ship cannot grow everything. It's a ship, not a planet. We want a variety of nutritious food, but that variety can't be extravagant.

In post #601 I also listed food that can be grown on Mars, preserved and shipped. As well as salad dressing.

Preserved food that could be added to the salad bar
black olives
onions - Spanish, red
chickpeas
black beans
kidney beans
dried cranberries
raisins
sesame seeds
sun-dried tomatoes (Well, greenhouse dried, with a fan?)
Trees will take some time to establish in greenhouses on Mars. Once established, we could add: sliced almonds, dehydrated apple slices, pistachios, pecans.
16 Vegan salad dressing recipes
Trying to avoid dressing with mayonnaise or dairy.
Catalina
Lemon poppy seed
Cherry tomato
Maple mustard
Greek
Olive oil
Balsamic vinegar
If we grow agave on Mars, we could add Carrot Ginger, Tangy Miso, and Balsamic Vinaigrette dressing.
Artificial maple extract can be made with vanilla extract, fenugreek seeds, and vodka. Vanilla extract with real vanilla bean and vodka. Maple syrup with artificial maple extract, brown or yellow sugar, and hot water. The extracts and sugar brought from Mars.
Mushrooms can be grown in compost. White mushrooms require growth medium with high nitrogen; most websites recommend a 50:50 mix of compost with horse manure. The mushroom farm a couple km from my house uses composted chicken manure. When the wind blows the wrong way... Shall we say not on the ship? Button mushrooms are another name for white mushrooms. Portobello mushrooms are white mushrooms simply allowed to grow to maturity. Cremini/crimini is actually also the same species. However, Oyster mushrooms grow on straw, sawdust, coffee grounds, other agricultural waste; we could grow them.

kbd512 · 2022-01-06 16:44:00

Robert,

Will the baconweed be added to the salads? If so, then I'm in. It needs to be crispy, though. It can't be like eating chewing gum.

RobertDyck · 2022-01-08 22:22:08

Met with Michael Paille today. He hadn't responded earlier because he was dealing with medical issues. Had a long discussion about Canadian politics. And a long discussion about Comic Con and how he was screwed. Did bring the discussion back to the Large Ship. He is willing to help.

Interesting that he brought up starchy food. He suggested growing potatoes on the ship. Potatoes require at least 3 months from planting to harvest. And they take a lot of space. Growing potatoes on the ship would require an excessively large greenhouse. On Mars, fine, but not on the ship.

I had thought of potatoes, and I think posted before. To do potatoes we would need an automated system where we could harvest mature potatoes without killing the plant. But potatoes must not be exposed to sunlight, or they'll develop a toxin. Any part of the potato not buried and exposed to sunlight will turn green, that toxin will make you sick if you eat it. So some kind of artificial growing medium, pebbles that are opaque to whatever colours of light cause potatoes to develop the toxin, but transparent to some colour (frequency) of light that video cameras can see. So the cameras can see potatoes within the medium. Smooth glass beads, opaque to visible light but transparent to IR? Hollow beads to make them lightweight? This would require a cultivar that thrives in full intensity sunlight 24/7, with small leaves and shorter or fewer runners. More energy to growing tubers, less to growing leaves and stalks. The plant won't need as many leaves because it will receive full sun 24/7. A robot to harvest the potatoes without killing the plant, and software to only harvest fully mature tubers. Growing potatoes in a medium like this is hydroponic. This required developing affordable glass beads, harvesting robot, software for the harvesting robot, and a new cultivar of potato.

For now, let's plan to send dehydrated mashed potatoes (potato flakes), and dehydrated scalloped potatoes, and frozen french fries. Since french fries will still have moisture, they will have more mass. So meals will be more common as mashed or scalloped.

RobertDyck · 2022-01-11 00:07:06

Baking powder.

Made with baking soda, acid, and starch as a stabilizer. The acid can be a few things, a simple acid is cream of tartar. When cooking, the acid and baking soda react to produce CO2 gas. That gas causes the bread to rise, or pancakes to become fluffy. I posted earlier how to make baking soda from human urine. A common acid is cream of tartar. That can be made from lees from wine. That's the sludge at the bottom of a fermentation vat. Soak wine lees in hot water, let it sit to dissolve potassium bitartrate (cream of tartar). Draw off the liquid to another vat, then let it evaporate. Crystals of cream of tartar will form.

RobertDyck · 2022-01-12 08:40:45

Attitude control

This can be accomplished by a momentum wheel or Control Moment Gyroscope. The latter is lower mass for a given torque so is used for large structures like a space station. CMG has been used on Skylab, Mir, and ISS. The Large Ship will use CMG for attitude control. The frame holding the CMG must be de-spun, but the CMG need not be within pressurized space. They can be located in depressurized space between the cargo hold and propulsion stage. Whether to use single-gimbal or dual-gimbal is a detail for engineers. The Wikipedia page for CMG is linked above as well as the image below; that page details advantages and disadvantages to single vs dual-gimbal. CMGs operate by electric motors so don't require propellant, however moving the vehicle in one consistent orientation will cause gyros to eventually saturate, requiring propellant to desaturate.

One of the CMGs for ISS.

tahanson43206 · 2022-01-12 09:20:17

For RobertDyck re #1056

Thank you for providing a plausible sounding (to me at least) solution for the obvious instability issues Large Ship will face as people and materials move about in the rotating structure.

No one (no human being at any rate) has every built and operated a rotating structure in Space. I am supporting your initiative, not because it is the best, because I have no way of knowing. I am supporting your initiative because it is plausible (from my perspective) and above all, it is consistent from one day to the next, and you have already received several indications of support from NewMars members.

Your role, as I see it, is to build up your status as a plausible leader, so that those with the skills you lack can fill in the details where they are needed.

Your status as a leader will be enhanced (I am sure) when you give your presentation to the National Space Society on March 12th.

I am available to help you prepare as best I can, but only ** YOU ** can prepare and deliver your Introduction to the World as a space craft designer.

Meanwhile, kbd512 is off (hopefully) working on his concept for a dual-rotating design. kbd512 is two years behind you, and if you just keep a steady pace, making incremental steps, the gap will remain two years.

(th)

RobertDyck · 2022-01-12 12:48:05

Counter rotating rings don't have the issue with gyroscopic stabilization. So it's easier to change orientation. Quicker to turn. Single ring means no pressurized joint that could leak air. And gyroscopic stabilization means orientation is more stable, less likely to drift. A military vessel would want greater agility. A commercial passenger transport, stability is appreciated.

If passengers moving is a concern, we can use water in the water wall tanks as ballast. If all passengers walk to the same side of the ring causing it to wobble, that change of centre of rotation can be detected by accelerometers. Smartphones have solid state accelerometers now. That can be compensated by pumping water from tanks of pressure compartments on one side of the ring to the other.

tahanson43206 · 2022-01-12 13:00:06

Bravo! For RobertDyck re #1058

Good to see your progress in managing momentum in Large Ship.

It should be possible to model the dynamics with a scale model in orbit.

Computer models would be a reasonable first step in making a case for funding for an orbital test article.

If there is a NewMars forum reader who would like to help with computer modeling of Large Ship, to address stability issues, please read the Recruiting topic and contact the forum.

(th)

tahanson43206 · 2022-01-12 13:17:23

For RobertDyck re kbd512's design ...

Just for clarification ... there is no need for kbd512 to have air seals at the rotating joint.

The habitat is ** way ** out at the end of a strut that extends from the central bearing. The habitat itself will (no doubt) be air tight where it is welded to the strut(s).

How many struts there are is a property of the design that kbd512 has not announced, but I presume where will be at least two, and perhaps more.

Forces must be conveyed from the central shaft to the mass of the rotating habitats via those struts, so I expect they will be sturdy.

No doubt kbd512 will enlist structural engineers to help with modeling the forces that will be at work.

(th)

RobertDyck · 2022-01-15 21:20:04

My girlfriend suggested adding to the salad bar canned beats and alfalfa sprouts. She said she saw canned beats at the salad bar at an old restaurant called Bonanza. Do people eat canned beats?

tahanson43206 · 2022-01-15 22:22:06

For RobertDyck re #1061

The suggestion of your friend for sprouts (alfalfa but could be many) seems like a really good fit for Large Ship. What might take a bit of research is the question of how to replicate the starting stock. Fresh sprouts would seem likely to be quite popular.

If you're thinking of shipping canned foods with the supplies for the trip, that would certainly seem reasonable, but I'm curious about the water tradeoff vs dehydrated foods, and the waste represented by the metal of the packaging. This is an interesting aspect of the planning that you are alone on Earth in facing. Congratulations on continuing to develop your thinking.

Eventually, the trail you are breaking will be trod by many, and the lessons you learn will be of value in years to come.

Update next day after pondering canned foods question: Canning is a reliable way to preserve foods for a long journey. The idea that came to me overnight is that the containers could be used to hold waste for delivery to Mars as source material for greenhouse inputs. Each passenger and crew person could be responsible for waste management (to the extent they are individually capable of handling the responsibility). This would ease the burden on crew.

Related questions arose (in my mind at least) .... humans have achieved an advanced capability to operate underwater for months at a time.

In the modern nuclear powered submarines, most of the issues that face the spacecraft designer have been addressed, with the caveat that mass is not generally an issue in a submarine on Earth. Mass is obviously of great concern in a passenger space craft.

When you (RobertDyck) are ready, I am fairly confident there is a reservoir of human talent and experience available in the human population that can be enlisted to assist with design of the myriad details of Large Ship.

The post #1061 is about food for a two year journey for 1060 people, and that single topic will eventually fill several large books if rendered in physical paper form.

(th)

SpaceNut · 2022-01-16 11:06:36

The term canned can also mean in a glass sealed container as well and the beets do come that way but at a premium for the store shelves.

For the freeze dried you need to add water and heat to bring them back to life. For frozen you would add a taste of water to bring them back to taste with heat and possibly a dash of salt.

The reuse of the waste stream is the critical part to save on energy with its paper, plastic cans or glass. Separate from food waste and keep until you land. The food waste is processed back into the fertilizer for food growth.

RobertDyck · 2022-01-16 12:40:52

Found this website, there are others... How to Grow Alfalfa Sprouts
The key ingredient is seeds. Growing out alfalfa to seed required much more room. You could grow alfalfa in a greenhouse on Mars, but for the ship we could just bring seeds.

SpaceNut is right, canning does not require a metal can. The first invention of canning was for military food supplies at the time of Napoleon Bonaparte. The first canning used champagne bottles. They had difficulty getting peas into and out of the bottles. Glass jars are reusable. But there was another invention around 1989: plastic bags. It requires a heavy plastic that will not melt in boiling water. The technology of canning is to boil food for a certain number of minutes to kill off any bacteria, also boil the container to ensure it's clean, then place the food while still hot into the container and seal air tight. For food safety, foods must be kept at a temperature so high that bacteria cannot grow. (details) As long as the food is still above that temperature (74°C / 165°F for soups, stews, casseroles, stocks, gravy) then you're fine. The advantage to plastic bags was weight. The plastic had to be hot when filled and sealed, so the bag was not printed, it was sold in a sleeve of printed cardboard. This didn't catch on. It's was used for camping, since a plastic bag is lighter than a metal can. But dehydrated food was more popular for hiking.

For Mars we would want to use mason jars or equivalent, because they're reusable.

For our ship, dehydrated is preferred due to weight. However, some foods don't taste very good when dehydrated. Canning is an alternative. For the ship we would probably want to use plastic bags to reduce weight, although printing directly on the plastic would eliminate the cardboard, so reduce waste and weight.

What I'm struggling with right now is the salad bar. Exactly what mix of foods should be in the salad bar, and how much (mass) consumed per day. This is important to size the greenhouse. In post #1052 I quoted post #601 with salad bar foods that are not grown in the greenhouse. I would like to make a change: onions - Spanish, red. What I read on the internet said onions can be kept up to 3 months if kept chilled. The trip will be 6 months, so we should grow them in the greenhouse (hydroponics).

I have read that for a side salad plan 1.5 ounces of lettuce, 2.5 ounces if it's a main dish. Another website said 2 ounces of lettuce, not differentiating between side or main dish. But that doesn't answer the question about other vegetables included in the salad bar. I listed a lot. That's on purpose, to make it interesting because passengers will be on the ship for 6 months, and this is the only fresh food. Entrees will be stored food: dry, dehydrated, canned, or frozen. Bread will be baked from flour. If we can produce flour on the ship using microbial wheat protein, pasta will be made on the ship, otherwise dry pasta will be shipped. Etc.

I haven't heard from my chef friend, so help quantifying the salad bar would be appreciated.

tahanson43206 · 2022-01-17 12:36:17

For RobertDyck re salad bar ....

In this post, I am combining thinking from 1064 and other posts, and from the work of kbd512 in his "Practical" topic.

kbd512 is NOT going to be providing a salad bar to any of his customers (subject to correction of my impression of his plans).

This leaves ** that ** aspect of passenger transport entirely to you.

Your famous and historic obstinance precludes what I am about to suggest, but I'm adding it to this topic for the record.

While the dimensions and features of the habitat ring are fixed in dimension, rotation and other characteristics, the greenhouse does not need to be limited to the top (inside) of the habitat ring. I think you put it there as an afterthought, but (hopefully) your thinking on the location, size and features of the greenhouse has not yet ossified. If it has, what I am about to suggest will remain a twinkle of might-a-been in the record of the topic.

If you allow your concept of the greenhouse to extend beyond the limited area of the habitat roof, you have a huge volume of space available to exploit. While the habitat is fixed at Mars Gravity, the plants don't need that prescription, and ones in water (like sprouts) don't even need that.

Calliban is hard at work on propulsion to serve Large Ship, and GW Johnson has already published notes on how to give Large Ship most of the acceleration it needs to leave Earth and to "dock" in Mars orbit using space tugs, so my recommendation is to work out what you need to care for your passengers and crew, and let others take care of the propulsion and navigation of the ship.

(th)

RobertDyck · 2022-01-17 16:22:45

From one company... Growing Lettuce in a Vertical Farm: All You Need to Know
This is an article by Vertical Farming Planet about a Minnesota company called Lettuce Abound Farms. Video from September 2019, but the website for the farm says they no longer grow lettuce, now they grow hemp seed, but the technology is valid. This is vertical farming, and aeroponics. The video in the article is also available directly on YouTube here... (click image) 2:32 running time

The article talks about fluorescent lighting. Again, I want to use ambient light. But the ship is in space, so it's a little different. Lettuce doesn't require full sun, so we can diffuse the light. A Fresnel in the ceiling over the lettuce farm can focus light on the walkway between vertical panels, and a diffuser between the walls of lettuce can spread the light out. Each panel is slightly angled, not perfectly vertical. Behind the wall is a sprayer that sprays nutrient solution on the roots. Water that drips down is caught in a tray/tub at the bottom, the spray head re-sprays it. Sunlight in space is brighter than the brightest day on Earth. Light in Mars orbit is 47% as intense as Earth orbit, but Earth orbit is roughly twice as bright as "full sun" on Earth's surface. Depending what you call "full sun". Oxygen, nitrogen, and water (humidity) in Earth's atmosphere blocks a lot, even on a bright sunny day with no clouds or haze. So this works even in Mars orbit. Note the vertical wall is not too high, a man can pick the top leaves with his hands when standing on the floor.

How to Grow Hydroponic Lettuce: Instructions and Plant Care Tips

Sizing: assume 2 ounces of lettuce consumed per person per day. Salad offered lunch and supper, but not everyone will consume salad every meal. Design for 1200 people onboard, so we have a little extra in case of trouble. So 2400 ounces lettuce per day. Weight of a head of romaine lettuce varies, 1 to 1.5 pounds. Let's use 1.25 pounds or 20oz. So we need 120 heads per day. There are two steps. First plant seeds in a plug, with plugs closely placed in a plug tray. After 2 to 3 weeks, transplant (move the plugs) to the growing system. Only 75% of the plugs will develop. Romaine lettuce is ready to harvest in 3 to 4 weeks. So 6 weeks from planting seed to harvest. To harvest 120 heads to per day, with 28 days in the system, we'll need 3360 slots. With 14 days in plug trays and only 75% viable, we'll need 2240 plugs. Looking at the video, rows are 7" apart so 8 rows high are 5' 1.6". With a hexagonal pattern, slots are 8" apart horizontally. So the growing system sheet is 32" wide (2' 8"). With 8 x 4 = 32 slots per sheet, the we need 105 sheets. Not all heads will develop, so 112 sheets? With 2 sides to a growing system, and 4 rows of growing systems, that's 14 sections long. They have two sheets high, but the ship will use diffused sunlight, not fluorescent. We could do 2 sheets high in Earth orbit, or 1 in Mars orbit. Eh, just design for 1 sheet high. The video looks like each row is only 3 feet wide, total. Very narrow gap between vertical growing sheets. They must use a crane of some sort to pull a sheet out for harvest. If we give enough room to walk, say 2' wide including plant leaves, and 30" wide corridor (2.5 feet, width of a door) so a worker can walk. Just harvest with the sheets in place. So 4.5' x 4 = 18' wide, plus walking space on other side so 20.5' wide. With 14 sections @ 32" width = 448" = 37' 4". In metric that's 6.25 metres wide x 11.38 metres long.

Light diffuser in the corridor between green walls would have to be lifted up out of the way when a worker is working.

Plug trays: the plugs in the video appear to be 1.5" x 1.5". The tray would have to be a bit bigger. Say 1.968" square, which is 5cm x 5cm. If trays hold 10 plugs deep by 16 wide, then each tray is 50cm x 80cm. For 2240 plugs we would need 14 trays. With 2 trays high we would need 7 long, so 5.6 metres. Trays could be along the growing system, and angled so light from the outside diffuser on one side would illuminate the trays. That's roughly half the length of the growing system. The remaining length could be a work table. Add 0.5 metre width for the trays, so we're now talking 6.75m x 11.38m. That's quite compact.

RobertDyck · 2022-01-17 16:32:09

The upper level will require greenhouse space for all crops. Plus fish tank. Plus compost bins. Plus mushroom farm. Plus work tables. Plus vat to break down starch into sugar. Plus vat to grow mould to produce amylase enzyme. Plus vat to grow oil for cooking. Plus processing for urine. Plus plus plus.

The question is whether the upper level will require full width, or whether it can fit within 8 metre width (26' 3"). If it's 8 metres, then corridors between standard cabins can have arched ceiling, and outside cabin can also have vaulted ceilings.

RobertDyck · 2022-01-19 19:15:03

My girlfriend sent a list of ideas for a salad bar. Mostly the same as the one I found. A few differences.
cauliflower
radish
celery
blueberry
canned sweet corn
sunflower seeds
corn nuts

When I was a child, people put radishes in salad. Do people still eat radishes? Cauliflower is Ok, but broccoli is more nutritious. Some people don't like celery. Blueberry tastes great, but how nutritious and what does it take to grow? Growing fresh strawberries on a ship is enough. Canned corn? Not exactly fresh, it's canned, and corn? You want corn on a salad? sunflower seeds would be dry and carried from Earth, but do we need them? And corn nuts? I tried eating a bag of corn nuts when they first came out in my city... never again. My girlfriend says she loves them. They're so hard they hurt my teeth, and now much nutrition? The idea is to make food selection appear broad and indulgent, but we need to reduce what we carry.

It also had egg, grated cheese, and meat: chicken, ham, turkey.
These require livestock. The ship will travel to Mars, so the emphasis should be things we can grow on Mars. And once a settlement is large enough, greenhouses on Mars will provide food. The ship will depart Mars with enough food for the trip back to Earth, for passengers are crew that are returning, and for the next trip to Mars will a full complement.

Bacon: yea, bacon weed. The article on bacon weeds showed an image of it formed into strips that look like bacon. So we could provide bacon weed strips for breakfast, and bacon weed bits in the salad bar.

SpaceNut · 2022-01-19 20:48:57

Some people like the fruit salads
https://en.wikipedia.org/wiki/Fruit_salad
There are so many varieties to picture and then you can add cream, or whip topping, or yogurt to the mix as well as pudding.

Original recipe yields 10 servings
Ingredient Checklist
⅔ cup fresh orange juice
⅓ cup fresh lemon juice
⅓ cup packed brown sugar
½ teaspoon grated orange zest
½ teaspoon grated lemon zest
1 teaspoon vanilla extract
2 cups cubed fresh pineapple
2 cups strawberries, hulled and sliced
3 kiwi fruit, peeled and sliced
3 bananas, sliced
2 oranges, peeled and sectioned
1 cup seedless grapes
2 cups blueberries

RobertDyck · 2022-01-19 22:35:15

Looks delicious. Some practicalities for the ship:
I suggested sliced nuts, stored and transported from Earth or Mars. Whether they're sliced on the ship or planet, I'll leave to a chef. But canned nuts can be transported, sealed.
How long Do Unopened Canned or Bottled Mixed Nuts Last?

How long does an unopened can or bottle of mixed nuts last at room temperature? Properly stored, an unopened canned or bottle of mixed nuts will generally stay at best quality for about 12 months, although it will usually remain safe to use after that.

Nuts - How Long Do Nuts Last? Shelf Life Expiration Date
A table. Past printed date, if stored in a freezer, pine nuts 5-6 months, others 1-2 years.

It may be a while before Mars has trees. Trees are large, requiring a large greenhouse, and take years from planting to first harvest. So for years they will be transported from Earth only. Almond trees 5-12 years depending on cultivar. When I bought a Goodland apple tree, I asked the nursery how long before it produces fruit. He said 3 years, so I asked how much for a 3-year-old tree? He looked stunned, and replied "Uh... we actually have one." Nothing like buying an 8-foot tree in a pot. It's big now. But the point is years.

So I have been thinking of dwarf orange trees grown in pots as ornaments in one observation room. There are now trees that produce full-size oranges, but the tree is dwarf. Passengers would be allowed to harvest oranges, and crew would harvest for the dining rooms. The other room would have juniper and other botanicals for gin. For greenhouses, we have to be concerned about space and time to harvest, as well as compatibility with the hydroponic system. Only crew or trained and designated agricultural workers allowed in the greenhouses.

If we start producing fresh fruit salad, how many trees will we need? How many orange trees, how many lemon, how many banana? There are high bush blueberries, and low bush blueberries. How quickly do they produce? Kiwifruit is actually a woody vine, it only produces the second year, and yield declines when the vines get old. Vanilla bean is also a vine. we can grow all these things on Mars, but is it practical to grow on the ship? The image shows grapes and blackberries. Of course grapes grow on a vine. Blackberries grow on a perennial plant very similar to raspberries. We could send canned fruit salad.

Pineapple grows on a plant. Definitely possible for a greenhouse on Mars, but consumes a lot of space so doesn't sound practical for the ship.
524dd94b86418.image.jpg

If you like, we could do a study of fruit yield per unit area of greenhouse, hydroponic nutrients required, and nutrition in the fruit. Which one(s) are practical for the ship. I was thinking strawberries, but we could study that.

kbd512 · 2022-01-21 21:08:43

Robert,

I'm putting this here so you can solve for how much torque has to be counteracted by your control gyros.

Precession - (Torque-induced - Classical Newtonian)

Torque-induced precession (gyroscopic precession) is the phenomenon in which the axis of a spinning object (e.g.,a gyroscope) describes a cone in space when an external torque is applied to it. The phenomenon is commonly seen in a spinning toy top, but all rotating objects can undergo precession. If the speed of the rotation and the magnitude of the external torque are constant, the spin axis will move at right angles to the direction that would intuitively result from the external torque. In the case of a toy top, its weight is acting downwards from its center of mass and the normal force (reaction) of the ground is pushing up on it at the point of contact with the support. These two opposite forces produce a torque which causes the top to precess.

ωp = ( m · g · r ) / ( Is · ωs )

ωp = angular velocity of precession (deg/s) (1/s)
m = mass (kg)
g = Standard gravity (you need to change this value from 9.8m/s^2)
r = perpendicular distance of the spin axis about the axis of precession (m)
Is = moment of inertia (kg*m2)
ωs = angular velocity of spin about the spin axis (deg/s) (1/s)

Precession (Torque-free)

Torque-free precession implies that no external moment (torque) is applied to the body. In torque-free precession, the angular momentum is a constant, but the angular velocity vector changes orientation with time. What makes this possible is a time-varying moment of inertia, or more precisely, a time-varying inertia matrix. The inertia matrix is composed of the moments of inertia of a body calculated with respect to separate coordinate axes (e.g. x, y, z). If an object is asymmetric about its principal axis of rotation, the moment of inertia with respect to each coordinate direction will change with time, while preserving angular momentum. The result is that the component of the angular velocities of the body about each axis will vary inversely with each axis’ moment of inertia.

ωp = ( Is · ωs ) / ( Ip · cos a )

ωp = precession rate (°/s)
Is = moment of inertia about the axis of symmetry (km*m2)
ωs = spin rate about the axis of symmetry (°/s)
Ip = moment of inertia about either of the other two equal perpendicular principal axes (km*m2)
a = angle between the moment of inertia direction and the symmetry axis (deg)

Edit #1:

VEEM Ltd makes an anti-roll gyro, their VG1000SD model, for small ships weighing between 300t and 900t.

That unit weighs 20,100kg, it requires 70kWe of input power during normal run / 110kWe during startup. It's rated to provide a counteracting force of 1,000kN / 334.5t of force.

Edit: #2:

Maybe you already know all about this, but just in case you need a handy reference...

List of moments of inertia

FYI, I'm learning or re-learning here, so if this of any use to you for your calculations, let me know. If you're not interested, then I'll stop posting, but I posted it just in case you find it useful for computing how much torque you need to counteract precession from the spin.

Last edited by kbd512 (2022-01-21 21:32:26)

kbd512 · 2022-01-21 21:51:17

Robert,

I'm thinking about contacting EPI Engineering Inc, to see if that company's CEO would be willing to quote us on how much it would cost for him or his employees to devote some of their considerable practical aerospace engineering experience towards developing force models for these two ship designs. He's developed a good number of real support structures like engine mounts and complex moving mechanisms like gearboxes for aircraft power plants (piston engines and gas turbines). Until I hear back from him, I'm going to continue to try to work this problem myself to see what I can come up with. I've spoken to him before about aircraft gearboxes and torsional vibration issues. He's a practical old-timer like GW who has decades of applied knowledge. I kinda want him to simply point us in the right direction (tell us what formulas apply and how to apply them) and then force us to do the work ourselves so we learn about how to do it. Once we understand all the basics, we can iterate these designs to our heart's content.

Edit:

Before I forget, your "model" is the "Thick-walled cylindrical tube with open ends" from the Wikipedia page. You can calculate MMOI for all the major components individually. Don't forget to include the atmospheric mass. I think Autodesk Fusion 360 can do this for you. I looked at ANSYS Mechanical pricing, then laughed my rear end off. It's about $50K per user license for all the modules we need. Fusion 360 is supposedly free for non-commercial use. Beyond that, I discovered SimScale online CFD / FEA software.

Last edited by kbd512 (2022-01-21 23:25:17)

tahanson43206 · 2022-01-22 08:01:25

For kbd512 re Fusion 360

The Fusion 360 software is available free for a year. It is reported in some detail earlier in this topic.

One disappointment (to me for sure) is that the cutoff after one year included denial of access to the models built online using the program.

As reported in this topic, Fusion 360 is a capable package that does require a video card able to support the graphics engine. RobertDyck recently upgraded his graphics card, as I had done in order to run Fusion 360.

Something to consider is that the IRS provides a way for companies to recover their investment if they make a donation to a non-profit such as Mars Society.

If your acquaintance is interested in reimbursement via tax adjustment, I would recommend you ask SpaceNut to contact Executive Director James Burk.

If done this way, the work would become public domain within the context of the Mars Society mission.

If you do not have a video card able to support Fusion 360, hopefully you can budget for one this year. I think you will find Fusion 360 a bit easier to work with than Blender, and the online support community is both active and well supported by the parent company, Autodesk.

(th)

RobertDyck · 2022-01-22 13:36:34

I'll post a couple more points about life support before we move to physics. I said urine would be concentrated to remove most, but not all water. That filtration would be done in the life support wall of cabins. Concentrated urine would be piped to central life support where it would be put in an electrolysis tank to remove sodium and potassium, and bubble off chlorine and hydrogen gas. That would be further processed to produce salt, potassium salt (salt substitute), baking soda, and lye which can be reacted with vegetable oil to produce soap. The next step to process urine is to bubble oxygen through it. This will react with urea to produce ammonia. Ironically, this does not consume oxygen, it consumes water, but the reaction only happens if water has elevated oxygen dissolve in solution.

urea is two molecules of ammonia bonded to carboxyl. The overall reaction is:
CO(NH2)2 + H2O → CO2 + 2 NH3

When dissolved in water, ammonia forms ammonium: NH4+. But when that evaporates it becomes ammonia: NH3.

Ammonia gas must be filtered to keep bad urine smell out. The smell is proteins in water, so smaller ammonia molecules can be filtered out. Ammonia can be separated from oxygen by refrigeration. Ammonia precipitates as a liquid at -33.34°C (-28.01°F) and freezes solid at -77.73°C (-107.91°F), both at 1 atmosphere pressure.

Phosphate can be isolated from urine: Technique to recover phosphorus from urine

Ammonia and phosphorus will both dissolve in water, forming a salt. That can be evaporated to produce diammonium phosphate crystals. That's yeast nutrient used for alcohol production, or various microbial processes.

Remainder of urine will decomposed by bacteria, then used as fertilizer in hydroponics. Note we don't have to remove all urea, because remaining urea is nitrate fertilizer. Or decompose it all to ammonia, and leave some of the ammonia in solution as nitrogen fertilizer. The usual process is one type of bacteria breaks down urea to ammonia, another breaks ammonia to nitrite (NO2), and another breaks it down to nitrate (NO3). Most plants require nitrate. If we react all urea to ammonia, then we've done the first step.

RobertDyck · 2022-01-22 13:57:00

Growing crops in a greenhouse on the ship requires a large portion of the plant be edible, rapid growth from planting to harvest, and compatibility with hydroponics. Celery certainly satisfies all these. The only question is whether people want celery. Radishes and cauliflower as well, same question.

Growing Hydroponic Blueberries - a Full Guide
This website points out blueberries require more sulphur than other crops. So ensuring enough sulphur could be an issue.

And from the same site: Growing Mushrooms in Greenhouse - A Full Guide

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