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Trying to keep the topic all together for content:
tahanson43206 wrote:For RobertDyck .... glad to hear you are planning to resume work.
I provided a link to a free PERT chart service, so I hope it looks like a good fit for Large Ship.
Without concrete steps toward a firmly defined goal, everything is just so much hot air.
Looking forward to your concrete plans, and for your specific plans to delegate responsibility.
This project would ultimately require thousands of people.
A leader of a project that size needs to be able to delegate responsibility.
I never said I intended to halt work. Our dispute happened when you insisted we contact manufacturers to fabricate parts. But we have no money, so we can't do that. Furthermore, the part you want fabricated is one of the parts that I said would be fabricated in space. We won't fabricate on Earth. Developing a prototype on Earth for the space-based operation is reasonable, but we can't just fabricate on Earth. And no, fabricating in space does not increase cost. The whole point of fabricating in space is to reduce cost.
Let's take a step back. One idea is a high-efficiency photovoltaic cell. That is the technical term for a solar cell. I read an article in the journal Science from year 2000, and the article includes work done at U.C. Berkeley materials lab which fabricated a prototype. It works. I want to mass-produce these for use on Earth. A house built with a roof that doesn't just have some solar panels attached, the roof *IS* the solar array. With integrated photovoltaic and solar thermal to pre-heat water for the hot water tank. One reason is to ensure photovoltaic cells do not overheat. That's how they fail. With solar roof, helical windmills in the back yard, geothermal heat pump, batteries in the basement, well insulated, and heat exchanger for home ventilation, the result is a house designed for southern Canada or northern US that is 100% energy independent during worst case weather. During the other 51 weeks per year, it produces excess electricity that it sells to the power grid. So the power utility never sends the homeowner a bill, instead a cheque very month. A larger cheque in summer, smaller in winter, medium in spring/fall. Of course it could be paid by direct deposit with emailed statement, so no snail-mail. These houses would be sized so starting with the first month a homeowner moves in, the total of mortgage plus utilities less cheque from the electric utility would be less than a traditional house: mortgage plus utilities. Purchase price would be a little higher, but as I just said, total monthly cost will be less, even if it's only $1 less. The trick to making this work is to ensure the municipality doesn't charge extra property tax. I believe these houses would be very profitable. The profits from these houses would subsidize our Large Ship project.
A few other projects:
kit to convert used cars to battery electric. Specifically target models of car used as host for a body kit. Customers willing to install a body kit will be willing to do other work, such as install our kit.
hearing aid that uses direct nerve induction to allow the completely nerve deaf to hear
thermal depolymerization plant that converts used plastic into oil & natural gas, but do not sell that as fuel, instead convert to new plastic. Sell bulk plastic as nurdles.
recycling carbon anode for aluminum smelting. Only emission is pure O2, no carbon emission. Eliminates coke and pitch that smelters must currently purchase, so saves them money. O2 can be sold as medical gas, so a byproduct to generate a little additional revenue. (Originally developed for Mars, but can be used on Earth.)
mining asteroid for steel, but byproduct is precious metals. Export precious metals to Earth for sale to raise money. Gold/silver alloy can be refined on Earth, but better use would be to sell as "asteroid gold" (10 to 18 carat) for designer jewellery.
aluminum oxynitride manufactured and sold on Earth as storefront windows. Designed to withstand a half-brick or baseball-size chunk of concrete, or baseball-size river stone thrown as hard as a man can throw it. Designed to prevent broken windows from break-and-enter or riots. Expect price to be 3 times that of the best tempered glass storefront windows. Patent on aluminum oxynitride expired more than a decade ago.
Can you think of other ways of earning money?
There must be a cash feeder program if we are to build it otherwise we are doing leg work for others to take the concept that has cash to pull it off.
Maybe its an option to scale a smaller version for a different crew size once we have more numbers to mass and content that are causing issues.
Right now we know that life support greenhouse oxygen and food is 360 people give or take....
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What's wrong with planting the idea in the mind of someone with the resources to build the big ship?
Do we need recognition that badly, or is it enough to know that we provided the idea to someone who could capitalize on it?
Do we think nobody else has ever had the same or substantially similar ideas?
The goal is to create an affordable and reliable mass transport system that some of us, perhaps our children if not us, might one day take to Mars, is it not?
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Here is the Louis funding plans
Maybe something will apply to get started with...
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Our primary goal is to reduce the cost of interplanetary transit. Artificial gravity, spacious cabins, cosmic ray shielding and gourmet menus, can all come later. It would be more useful in the short term to have a ship that uses high ISP Propulsion and space derived propellants to reduce the cost of transportation for the average passenger to something less than six figures. And in the short term, it will need to be compact enough to be assembled from Starship launches in low earth orbit.
For most people, affordability is the biggest driver that will determine whether going to Mars is something they choose to do. Forget about private cabins with their own showers and toilets. Think more along the lines of communal sleeping areas with private sound proofed cubby holes, with doors that slide closed to provide privacy. Each cubby hole with sound proofing, would have a volume of about two cubic metres. They will include television and computer games for private entertainment. They could include a vacuum pipe that the occupant pees into. The ship will be designed so that all of these cubby holes can be grouped together in a compact cubic geometry communal sleeping area. Food, wastes and consumables are packed around the sleeping area to provide shielding. The ship will be cramped. So be it. The cost of luxury conditions in Space is more than most people can afford to pay. The sleeping dormitory, would be located at the centre of the habitable volume. The habitation volume would be a sphere some 50m in diameter, for a ship carrying 1000 people. That is about the same volume per person as an SSN submarine.
Propellant for electric propulsion should be sourced from either Mars or its moons. We could use Argon sourced from the Martian atmosphere. Argon tankers launched from Mars would have much better mass ratio than the equivalent launched from Earth. We should be able to take on enough propellant in Mars orbit to take the ship on a round trip to Earth and back. Or maybe even raw regolith from Phobos, packaged as reaction mass for some kind of mass driver engine. Either way, Mars provides propellant and consumables more cheaply than Earth.
A ship like this should be able transport people from Earth to Mars for $10,000 a head. With star ship flights at both ends, we might get cost down to $100,000 for a family of four or $25,000 for an individual. That is the sort of price that is affordable to most people with the sort of skill sets we are aiming for. If you want to build up cities quickly on Mars, we need transportation to be cheap. The number of potential colonists will be proportional to the inverse of emigration cost, raised to some factor. If the cost is measured in tens of thousands of dollars, you have thousands of times more potential colonists than if cost were measured in hundreds of thousands of dollars. So we need to build ships that provide steerage class accommodation. Forget about luxury cabins. Food will be prepackaged and you will be eating, sleeping and shitting in zero gee, because that is what is cheapest. Achieving minimum cost is all important.
Last edited by Calliban (2022-04-20 03:36:53)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Welcome Calliban. Thank you for joining the discussion. Tom had questioned whether 3rd class cabins, claiming they're too cramped. But they're based on 3rd class cabins of the age of steam ships, including the Titanic. 3rd class was specifically for working people migrating permanently from Europe to North America. It was a bed and a sink, nothing more. Cabins on the Titanic were intended for families, or adult strangers of the same sex. I added a washroom the size of an airline washroom as part of life support, water recycling. Hotel rooms today have an en-suite washroom. And a 6-month journey will require bathing and laundry, so I included a shower stall. The same size as a shower stall you can buy in a home improvement store today, but the smallest.
I had also argued for enclosed bunks, back when the Mars Society was new. FMARS was the first analogue research station, built beside NASA's analogue in the Canadian arctic. FMARS was built with enclosed bunks as you describe. People who stayed there hated them. MDRS was built with small cabins instead. What I described for the Large Ship is a cabin just barely long enough for 2 bunks, each bunk is a "single" meaning 30-inches wide, two bunks high, and bunks on either side of a central isle barely large enough for an adult. That would be 8 bunks per room, except one pair of bunks (up and down) is replaced by the shower and washroom.
Geometry is not spherical or cubic, because humans require gravity. The ship has a single ring, with one deck. The cabins are packed tightly on that ring. A partial upper deck was added for greenhouses and observation rooms. The observation rooms serve the same purpose as a ship's deck. The ship is intended to carry dry and dehydrated food, but greenhouses add fresh vegetables for the salad bar. I examined ways to make some simple foods onboard to reduce cost, and in case free-return is necessary. I could detail them, but this thread is about hull material.
Launching everything from Earth is *NOT* the way to reduce cost. You want to use in-situ materials. I chose an iron asteroid because that's the easiest from which to harvest material. It's already metal, not an oxide mineral ore. Just refine to separate metals, then combine to form alloys.
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One option would be to construct the large ship in low Mars orbit, using Mars manufactured steel lifted into orbit by Starships. Iron is abundant on Mars. Carbon steels and cast irons are things that we could manufacture quite quickly. Maraging steels may be more difficult.
Plain carbon (0.5%) steels have yield strength up to 600MPa.
https://www.azom.com/article.aspx?ArticleID=400
The low gravity and thin atmosphere of Mars affords other opportunities. If the large ship is equipped with a minimal chemical propulsion system, we could build it on Mars surface and launch it using a rocket sled. The chemical propulsion system can then provide additional dV needed to build up orbital velocity. Rocket sleds have reached 2.8km/s on Earth. We need 4km/s dV to reach Mars orbit. The sled could use a simple pressure fed engine system, burning LOX/CH4 or LOX/H2. It should be quite easy to build.
Last edited by Calliban (2022-04-20 05:27:57)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #66
Thank you for the (to me surprising) vision of a space craft manufacturing facility at Mars.
I am hoping this idea receives attention in this forum and (hopefully) elsewhere.
(th)
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I could joke about science fiction. Starfleet shipyard was at Utopia Planitia, birth place of Galaxy class starships. But my preference is Elysium Planitia, specifically the frozen pack ice.
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The starship and mars is the issue due to how many loads of fuel on orbit are required to get a single ship to mars whether its full of people or cargo makes little difference since once it lands its not coming back for a long period of time since mars has to have a refuel processing plant before we can even get to that next step.
No amount of wishing will make it happen as we need funds to be able to even think about it being possible to set up shop with a starship system.
We must do something different to kick start mars....
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If lattice fusion does work as well as it now appears, we can power the sled using a fast fission nuclear thermal engine, which is fed with liquid CO2 propellant. This can be stored as liquid in a carbon steel tank. It will be self pressurising, with vapour pressure forcing propellant through the core. The fuel will be in the form of liquid uranium metal, with tungsten tubes running through it.
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Calliban,
What happens if other parts of the core get melted from the heat and you no longer have the correct core geometry or neutron absorbers to moderate the fission rate? Does that large mass of unmoderated liquid Uranium become the world's largest atomic bomb? I'm not trying to throw cold water on the idea, I just want to know what happens if something inside the core gets damaged or destroyed. Are there rods of something that absorb neutrons inside the core to control the reaction rate? What are those made of? Boron Carbide, or Tungsten-clad Boron Carbide? Pretty much any type of steel that I'm aware of melts at about 300C to 400C greater temperatures than molten Uranium, so what will the reactor pressure vessel be made from? It sure as heck won't be steel.
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Calliban,
What happens if other parts of the core get melted from the heat and you no longer have the correct core geometry or neutron absorbers to moderate the fission rate? Does that large mass of unmoderated liquid Uranium become the world's largest atomic bomb? I'm not trying to throw cold water on the idea, I just want to know what happens if something inside the core gets damaged or destroyed. Are there rods of something that absorb neutrons inside the core to control the reaction rate? What are those made of? Boron Carbide, or Tungsten-clad Boron Carbide? Pretty much any type of steel that I'm aware of melts at about 300C to 400C greater temperatures than molten Uranium, so what will the reactor pressure vessel be made from? It sure as heck won't be steel.
A very good question I think. One of the problems with the old designs for gas cooled fast reactors was that a coolant leak would lead to loss of moderation and spectrum hardening. In a fast reactor, a hardening of spectrum can increase reactivity because the number of neutrons yielded by fission increases as average neutron energy increases. This happens exactly as coolant density (and heat removal capability) reduces due to primary circuit depressurisation. Using lattice fusion modules would appear to introduce a similar problem, as rising neutron energy would increase Fusion rate.
In my design for a gas cooled fast reactor, I dealt with the problem in two ways. Firstly, I used four power generation loops per reactor, which limited the maximum depressurisation rate from a single loop and thus the rate of pressure drop. Secondly, if unplanned pressure drop did occur, high cross section liquid metals would be drawn into tubes within the core as pressure declined, absorbing excess neutrons and softening the spectrum. Maybe something similar will be needed in hybrid lattice Fusion fast-fission reactors.
Could lattice confinement Fusion neutron multiplier modules turn a nuclear reactor into a bomb? I think it is possible because we are dealing with fast neutron systems in which reactivity increases as neutron energy rises. In a light water reactor, declines in moderator density would be very effective at counteracting this effect. But in a fast reactor thermal expansion of the fuel is a much weaker negative feedback. There is potential for a thermal runaway effect to explosively dissociate the core. It is hard to imagine DU or low enriched uranium actually exploding in this way. But as we have coupled it to a device that is designed to amplify neutron flux, I think it could happen.
Last edited by Calliban (2022-05-03 02:43:40)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Post #29 includes images and a link to a PDF document with engineering details about corrugated steel sandwich. I look at the document and my brain stalls. I am hoping a certain engineer (hint hint hint) would look at this. I asked before. The constraint is the face yielding is acceptable. Core yielding or buckling is not. As long as face yield does not rupture the material creating a leak. A side wall of a cabin will be 2.4 metres tall by 4 metres long. It will be reinforced / held by all edges. Catastrophic decompression will result in even pressure of 1/2 atmosphere across the entire surface, against hard vacuum on the other side. Experiment described in the document used 304 stainless steel. kbd512 suggested maraging steel.
Seriously! Is there no way to use these formuli (formulas) to calculate what would be required?
Anyone still not comfortable with a flat wall holding pressure, don't think of it as flat. Think of it as an air mattress shape with vertical tubes, but made of steel, they're triangular instead of cylindrical tubes, and covered an a sheet of steel on either side. Of course it's not quite that simple. The corrugations are welded to the face sheet (not brazed) creating a truss. But it's a 3D truss forming a thick wall, not just a 2D truss forming a beam.
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RobertDyck,
I know I'm not the one you want an answer from, so just think of this as "interesting to know" info.
You have 9.6m^2 of surface area exposed to vacuum, with 7.35psi of force pressing outward on the pressurized side, trying to overcome the strength of the welds along the edges of the corrugated panel. Even if the panel is so stiff that it doesn't appreciably deform (and frankly this will not be a problem at all for any reasonable thickness of corrugated sheet steel- it'll be plenty stiff, trust me), that is not your primary concern.
1m^2 = 1,550in^2
9.6 * 1,550 = 14,880in^2
14,880in^2 * 7.35psi = 109,368 pounds of force trying to shear the panel's welds along the edges of the panels
Roughly speaking, you have a 504in long perimeter weld.
109,368 / 504 = 217lbs of shear load (if I understand the parts geometry correctly) per inch of welded seam
RoyMech - Weld Strength Calculations
The problem is not so much the face or even the core yielding slightly, unless it's so thin that it progressively yields to failure, it's the welds at the edges of the compartment. Those welds are the only thing preventing a catastrophic depressurization of the rest of the ship. That is why it's easier to sufficiently reinforce smaller compartments. A much lower total force is acting over a weld perimeter that hasn't substantially decreased. Neither the base metal nor the welds get any stronger as the size of the compartment increases, so you either require serious reinforcement of the weld seams, thicker metal and therefore heavier gauges of sheet steel, or you need smaller areas for the forces involved to act upon. When less force is concentrated over a given area, a lighter structure with sufficient tensile strength can be designed. The stiffness of the corrugated steel structure is also much greater over that reduced surface area.
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It is also why welds are x-rayed to show how well the bond has been created.
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Well, it looks like the math formatting isn't going to cooperate, but here's a formula for buckling curve approximations for orthotropic homogeneous core materials, such as honeycomb core sandwich panels made from Aluminum / Titanium / Stainless. Every "x" and "y" you see in there is supposed to be a subscript.
qb^2/(π^2B) = [λsxsy+a(sx+λsy)]*(1+λ)^2 / (λsy+λ^2sx+λ^2sxsy+ aλ(sx+λsy)+a(1+λ)^2)
Here's the paper that goes with it, from an Air Force project, from the Rand Corporation:
Minimum-Weight Design of Sandwich Panels by L. E. Kaechele - 22 March 1957
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Bending Stiffness formula (it's late, and I've no idea if I did this correctly or not):
B = Ef * f(f+c)^2 / (2*(1-nu^2))
Ef = Young's Modulus of face material
f = face thickness
c = core thickness
nu = Poisson's ratio of face material
So for 17-7 PH stainless, 1/8in thick face sheet and 1in thick core...
Ef = 29,600ksi
f = 0.125in
c = 1in
nu = 0.3 (approximation for steel that hasn't yielded / plastically deformed)
B = (29,600 * 0.125((0.125 + 1)^2) / (2*1-(0.3^2))
B = (29,600 * 0.125((1.125)^2)) / (2*(1-0.3^2))
B = (29,600 * 0.125((1.125)^2)) / (2*(1-0.09))
B = (29,600 * 0.125(1.265625)) / (2*0.91)
B = (29,600 * 0.125(1.265625)) / (1.82)
B = (29,600 * 0.158203125) / 1.82
B = 4,682.8125 / 1.82
B = 2,572.9739ksi
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