Large scale colonization ship

kbd512 · 2023-09-21 18:29:09

GW,

How about Beryllium Copper alloys?

Those don't become brittle so far as I know, and have much higher yield strengths than 304L, of around 125 to 180ksi. The dust from machining it is toxic, but touching it or getting a cut from a piece of it is not, so far as we know. At 8.25g/cm^3, it's not much heavier than 304L, at 7.93g/cm^3. The C17200 alloy I had in mind costs about $5,000/t, vs 304L at $2,500/t. I dunno. Maybe we just have to deal with using soft 304L.

As that seems pretty expensive, how about this special high-Nickel Austenitic ductile Iron alloys (the patent expired in 1979):

US Patent #US3055755A - Austenitic ductile iron having high notch ductility at low temperature

It was made for use with LH2.

The present invention contemplates austenitic ductile irons containing about 20% to about 24% nickel, about 2% to about 3% carbon, about 1% to about 3% silicon, with the sum of the carbon content plus 0.06 times the nickel content plus 0.2 times the silicon content being not more than 4.4, about 3.25% to about 5% manganese, not more than 0.25% chromium, a small amount, e.g., about 0.04% to about 0.12%, of magnesium eiiective to induce the occurrence of spheroidal graphite in the cast iron, and the balance essentially iron. These cast irons are characterized by freedom from carbides and freedom from martensite even when cooled to temperatures as low as about 423 F. and are further characterized by weldability and good founding characteristics.
The nickel and manganese contents of the alloys are very important and the contents of these elements must be maintained within the foregoing ranges in order to produce the improved results found in alloys Within the invention. Thus, the nickel content of the alloy must be at least about 20% because lower levels lead to austenite instability and martensite formation and must not exceed about 24% because no further gains in properties are evident. In addition, the manganese content must be at least about 3.25% because lower levels lead to austenite instability and martensite formation and must not exceed about 5% because of carbide formation which causes embrittlement.
The alloys produced in accordance with the invention should be substantially devoid of copper, and in any event should not contain more than about 0.25% of copper as an impurity. Since the alloy contains magnesium, which is a sulfur-avid element, sulfur in the alloy is present only in limited amounts, if at all, and usually will not be present in amount exceeding 0.02%. Phosphorus, a common impurity in cast irons, should not be present in amounts exceeding about 0.10%. The carbide-forming elements such as chromium, molybdenum, tungstem and vanadium should be substantially absent from the alloys as their eflFect in the alloys is undesirable. Thus, these elements should not be present in the alloys in amounts exceeding a total of about 0.25 Other impurities such as antimony, cerium, bismuth and lead should be kept below 0.003% total and titanium preferably should be less than 0.02% as these impurities have a deleterious effect upon the spheroidal graphite structure.

RobertDyck · 2023-09-21 20:17:10

First I have to point out we're having an argument like adults. With facts and numbers. We can still respect eachother and result is to actually solve a problem. That is so rare on the internet.

RobertDyck · 2023-09-21 20:59:32

GW Johnson, you asked me to stick to established design due to experience. You also said...

GW Johnson wrote:

Use pressure bulkheads to seal off sections of that pressure shell, exactly like the water tight compartments in ships. You can put whatever cabin shapes and construction you want inside each pressure compartment. That's exactly how they solved the analogous problem in ocean liners. The cabins were not even water tight, much less pressure-tight! But each compartment was sealed off by a bulkhead stout enough to hold the pressure of a depth of water as tall as the hull.

That's what I'm trying to do. Pressure on an internal bulkhead is equivalent to that of a water-tight compartment of a ship. As I said, water pressure at the very bottom of the hull of a modern cruise ship is 1 full atmosphere. Air pressure in this ship is half an atmosphere. Water tight compartments on a ship are not designed to withstand pressure while sinking to the bottom of the sea, they're designed to keep the ship afloat when one compartment is completely flooded. So strain on a bulkhead is directly analogous to a water-tight compartment bulkhead.

If you look at floor plans of a ship, I'm trying to use the same design philosophy. Water-tight compartments are rectangular sections that extend from one side of the hull to the other. Aircraft carriers use even smaller compartments, but that's because the hanger deck has to be one open space without dividers. Surrounding compartments must act as floatation should water get that deep. But cruise ships use rectangular compartments. And bulkheads are flat with deck floor and ceilings acting as reinforcement. That's exactly what I'm trying to do.

You also said cabins are not water-tight much less pressure tight. Again that's what I'm trying to do. Individual cabins will not be pressure-tight.

kbd512 raised the issue of fatigue. Realize an internal bulkhead will normally not have any pressure, hatches will be open to ensure pressure is equal on both sides. And it won't be exposed to the cold of space. The hull will, but internal bulkheads will be within air and temperature controlled for a shirt-sleeve environment. Worst case is a puncture immediately after departure from Earth toward Mars; bulkheads would have to endure vacuum for up to 6 months. Repair crew will try to seal the puncture so the compartment can be repressurized, but worst case is it can't be. In this scenario the vacuum side won't be exposed to the heat/cold of space. Radiant heat will be from cabin furniture and walls.

RobertDyck · 2023-09-21 21:08:29

Weld strength is a very valid point. I envision corrugated steel sandwich with corrugation vertical. Distance from floor to ceiling will be 2.4 metre (7 feet 10.5 inches). Welds of corrugation to sheet steel face will be that long. Welds will not be along the 4 metre (13 feet 1.5 inch) length. Yes, this will be 103.36 square feet. But it's supported along the top and bottom of the bulkhead. Doesn't that count?

RobertDyck · 2023-09-21 21:29:22

https://makeitfrommetal.com/what-grade- … s-and-tips

Railroad track steel is typically 1084 or equivalent hot rolled steel. This is a medium carbon steel with 0.7% to 0.8% carbon and 0.7% to 1% manganese.

kbd512 · 2023-09-21 22:18:33

RobertDyck,

You're trying to rationalize a bad engineering decision to make this vessel look and function a certain way. A PhD in aerospace engineering already told you why square pressure vessels are an engineering no-no. Apart from satisfying aesthetics, there's no upside to this decision. Worst case, you could have successive failures of multiple interior bulkheads. If you reinforce the welds enough or change the bulkhead geometry near the welds, then maybe you can get away with it, but GW already explained the what and why of the minimum mass solution.

As an aside, any debris with enough kinetic energy to compromise the hull could easily compromise relatively thin interior bulkheads at the same time. A "shotgun effect" from penetrating debris should be expected since whipple shields deliberately cause impactors to break apart into smaller pieces.

Why can't the habitation ring be a D-shape like a tokamak?

What's the harm in altering the habitation ring geometry if it makes the entire design stronger and more survivable?

If this is about the water wall, using a tokamak geometry could allow for increasing the shield thickness or coverage area over specific parts of the ring to provide better radiation protection. I think it's entirely reasonable to have the colonists congregate in the mess halls for a few hours to a day or so in the extremely rare instance that the ship flies through a CME or solar flare. That way we can be certain that complete water protection is available to defend against these non-repeatable but otherwise fatal events. Some concession to the seriousness of the event needs to be made by the passenger and crew. It's like being trapped by a hurricane. Everyone meets their neighbors for a few hours in the stadium while nature's fury passes.

RobertDyck · 2023-09-21 23:51:12

kbd512,
Now you're getting insulting. I already explained that this is based on ship design principles that have been used since the 1800s. GW has a lot of knowledge and experience but not in designing ocean ships. And I already explained that to make this ship work requires efficiency. Designing a ship bulkhead based on solid rocket motors is not necessary. And I already explained the waste created by this decision.

Whipple shield works with high velocity but small impactors. An impactor capable of penetrating the hull will not fragment significantly, and fragments will not disperse significantly. If you want to use a shotgun as analogy, think of a close range blast. Very tight grouping.

This is a very large ship. It must be very efficient to minimize size. Too much wasteakes it unworkable. And this is welded, not modules bolted together with rubber O-rings. A loose collection of modules like ISS will never withstand the forces of rotation much less acceleration.

You mentioned the water wall. It's not just that, but that is part of it. A 2.4 metre high wall, just 12cm thick, provides shadow shielding to the entire 19 metre width of the ring. The water is a lot of mass, it has to be minimized. And we don't want to fall back on closet size shelter(s). Operational problems with 1,000 civilian passengers onboard. You keep talking about a navy aircraft carrier, this is a civilian passenger ship. They won't have as much discipline. If you don't like that, I have to point out a couple astronauts who didn't behave as one would expect. ISS has had so many visitors that some have proven to not have the right stuff. Furthermore, a Solar Proton Event (solar flair or CME) could last a couple hours or up to 3 days.

kbd512 · 2023-09-22 02:44:50

RobertDyck,

Pointing out objective reality is not an insult, unless you choose to take it that way. This is an aerospace vehicle, not an 1800s sailing ship, so GW's decades of knowledge from actually designing and building high performance aerospace vehicles is highly relevant. Designing a ship to maintain its structural integrity is a form of efficiency.

An impactor that hits a whipple shield at hypervelocity will fragment, because that's what happens to hypervelocity objects that strike other hard objects. NASA tests have proven as much. IIRC, the general idea is that the multi-layered fabric shield will cause the impactor to fragment and then dissipate its energy over a wider surface area of fabric layers. Bullets caught by plates or layers of kevlar do the same thing. Shotgun pellets also get deflected off of hard objects and then travel along different paths.

Ensuring that a spacecraft is sufficiently strong is the price of admission into the world of high performance commercial aerospace vehicles.

How well would a prospective colonist fare on Mars if they're too undisciplined to stay put for 3 days in a place with food, water, bathrooms, and protection from the environment?

tahanson43206 · 2023-09-22 07:36:56

For kbd512 re floorplan of proposed 1060 person occupancy space vessel.

http://newmars.com/forums/viewtopic.php … 78#p172878

In the post above and several others nearby, I have tried to show what it will look like if the 1060 people are distributed more or less equally throughout the floorplan that is proposed for Large Ship.

It seems to me that the ship must be protected from radiation throughout the space, because there is NO place for anyone to go. Elsewhere I looked up the density of population of large cities on Earth, such as a few in Asia where density is high. The results were posted elsewhere in the forum. My recollection is that the density of packed humanity proposed for Large Ship is not too different from the density you might see at a rock concert.

A better example might be a field of 1060 soldiers/sailors lined up to do calisthenics. That density is what you (as a passenger) must contend with for eight months.

(th)

GW Johnson · 2023-09-22 08:41:38

The flat bulkheads in ships are thick and heavy, and reinforced with beam-type ribs, to stand about 1 atm pressure difference. Ships can carry that weight, flight vehicles usually cannot.

By the way, the breaking-up noises heard as a ship sinks are usually bulkheads collapsing into compartments still full of air but under the surface. That of course weakens the hull strength, which is why wrecks on the bottom are often distorted in shape, or even broken apart.

They usually strike bottom in the vicinity of 10-40 mph, heavier warships faster due to the weight of armor. Submarines, being heavier still to be submersible, hit nearer 100 mph. Some bulkheads in submarines are built curved, to hold pressure if submerged.

(See, I actually know about more than just aerospace.)

In airliners, the aft fuselage bulkhead is usually built almost hemispherical. They usually have the tail cone space to do that, with the attach ring not needing to do much more than cover the strain mismatch between the cylindrical and spherical shapes. If instead you go to a spherical segment dome, you have at least an approximation of bulkhead flatness, at the cost of a bigger and heavier attach ring. Yet it is still only a ring out of quite a bit of otherwise lightweight-membrane construction, so weight is not that badly impacted.

Some airliner aft fuselage bulkheads are built that way with spherical segment domes and slightly-heavier attach rings (if more space is needed in the unpressurized tail cone for APU's and similar equipment). It really is a proven flightweight option. It is the option I would recommend for your big ship, so that your space loss is minimized.

Solid rocket motors have forward closure domes that are spherical segments, at extreme pressure. These are membranes with a big attach ring that doubles as the load takeout for the skirt connecting the motor to the rest of the missile. There is quite often (but not always) a similar aft structure attaching the blast tube nozzle assembly, with a skirt that attaches a piece of aft shell where the tail fins go. Actuators for the fins fit in the space between the nozzle blast tube and that outer shell piece. All these items carry considerable flight loads, literally being the aft missile airframe. I think the highest pressure rocket motor I dealt with was 4000 psig. Most were nearer 2000 psig, all tactical sizes. Shuttle SRB's were about 900 psig. Size matters, because steel is only so strong. Square-cube scaling thing.

Railroad tank cars are the exception here. Most of them are either unpressurized or very low pressure (like 5-10 psig). Weight is the bigger driver. They are made with elliptical ends to maximize the volume that can be carried within the allowable space between the couplers. These are usually shear-spun out of flat steel plate. (Again, not aerospace, but I do know about it!)

Bear in mind that crash loads more than anything else dictate the use of half-inch to one-inch steel plate. Being unpressurized, they can get away with elliptical domes, but the crash failure is almost always at the dome joint. There are high-pressure tank cars, but these have true hemisphere domes! They usually do not have the local thickening at the dome joint, and that is where the crash failure always occurs. (Although, another common failure is dome puncture by the coupler of another car. That is why many tankers have a piece of steel plate mounted on the chassis at each end, to ward off threatening couplers in a derailment.)

There is going to be a lot of equipment supporting human survival and comfort needs located within each compartment of your big ship, just like an ocean liner. If you end up using curved-membrane compartment bulkheads, package that equipment in the odd curved spaces at the bulkheads.

As for radiation protection, it does not have to be water, although water does serve very well. It only has to be made of low molecular weight atoms, to limit the "atomic spallation" that is induced secondary radiation. Solar flares don't cause that, but cosmic rays do. Yet solar flares are the real lethal risk, because there is such a gigantic flood of that kind of lower-energy particulate radiation. The higher-energy cosmic ray particles are so dilute, there is little risk here in this part of the solar system from cosmic ray exposures, other than an increased risk of cancer later in life. A few, not several, percent increased risk.

All you need is about 20 g/cm2 of low-molecular weight atoms to stop most such solar flare events, but that is probably not quite adequate for huge things like the 1972 event. That can be about half a meter to a meter-thick layer of polymer fabric layers, which can also serve as thermal insulation, and as part(but not all) of the meteor shield. Put it on the outside of the pressure shell, and the cryogenic temperature exposure risk for you pressure shell goes away. That way, at least in principle, you can get to the pressure shell from the inside, to repair any punctures.

The experimental inflatable module at ISS has already proven the effectiveness of half a meter of outside fabric wraps, as a radiation shield and as thermal insulation. Outside of LEO, you need more shielding, which would be about a meter thick instead of half a meter thick. Bigelow is no more, but their B-330 design had a full meter of these fabric wraps, guess why? For a huge event, you might want to temporarily evacuate to an area additionally shadow-shielded by water tanks or similar. Rocket propellant tanks can also serve as shadow shields. Anything made of low molecular weight atoms can serve.

Water, gray water, and wastewater tanks you will have in abundance for 1000+ people. They don't all have to be inside the pressure shell, you know. Just use plumbing that is sealed up tight, and they can be outside it. But I still recommend that such plumbing and tankage inside the thermal insulation/meteor shielding.

I'm just trying to help.

GW

Last edited by GW Johnson (2023-09-22 09:20:19)

kbd512 · 2023-09-22 09:18:29

tahanson43206,

I took the average volume of a person and then multiplied that by 6, which worked out to 0.17m^3. I took the volume of a torus with a 238m outer diameter and 9.5m tube radius, which yielded 195,070m^3 of internal volume. All 1,060 people occupy 180.2 cubic meters, bearing in mind that I multiplied average actual body volume by 6. The interior volume of an aircraft carrier is about 1.04 million cubic meters, which normally contains about 6,000 people. Divide by 6 and you get 173,333 cubic meters. Relatively speaking, these people have more space. Cramming a large number of the crew into 3 galleys, for up to 3 days at most, but probably hours, does not seem particularly problematic, since it was done every day aboard aircraft carriers during a process we called "serving chow". Let's say that each galley occupies 6 times the volume of the people who must jam-pack the place during a rare solar storm emergency. That's 1,081.2m^3.

The actual average volume of a person is about 0.0283m^3, so the 3 galleys occupy roughly the same physical volume as 38,205 people. I think the galleys have enough physical space for this emergency storm shelter function. Will it be crowded? Yes. Unbearable? Hardly. Whenever we gathered together on the messdecks, after listening to the Captain or other officers give their speeches or present awards and information, we talked, joked, and generally had a good time being able to sit down and stop working for a little while.

For about 800 of my first ship's company, we gathered together in a space about the same size as the first floor of my house. We all lived, nobody died, there were no fights, and we shared Thanksgiving and Christmas meals together (everyone not on watch). It's not a punishment. For this ship, it's like the crew of a destroyer gathering together in a space much larger than their main spaces.

During normal course of business, this will never happen. If it ever does, then we already contemplated the problem and how to solve it without making excessive design compromises elsewhere to save weight. We heavily shield selected areas of the ship so that the crew are very well protected in the exceedingly rare event that it's needed.

tahanson43206 · 2023-09-22 10:51:32

For kbd512 re Post #1386

This is Rob's topic, so it's for him to say one way or the other, but ** I ** appreciated the analysis and comparisons and real-life experiences you added to the topic.

GW Johnson is working on more ideas to offer to Rob. I've asked GW to have another go at one of his idea sets, because I know that Rob is going to want a feature that GW left out.

(th)

kbd512 · 2023-09-22 11:14:50

Providing 300mm of water shielding around a 9.5m diameter torus, for 90m of total length between 3 galleys, will require 169.2t of water. This works out to 45 gallons of water per person for the entire trip. There's more than enough room for both the galley and a male / female emergency berthing compartment at either end of the galley. The rest of the time, they can all bunk in staterooms. This seems like a very reasonable compromise that provides both superb physical protection in an emergency, and lots of space at all other times. If the galleys will also be positioned at the "spokes" connected to the hub, then reinforcement of this area is already required, so it makes even more sense. I get that it may not satisfy every aspect of the "cruise ship" concept, but even cruise ships have required numbers of lifeboats cluttering the deck. Think of these areas as "lifeboats". Most of the time you don't need them, but when you do, you really need them.

kbd512 · 2023-09-22 14:24:10

I've been looking into various Titanium alloys and I think Titanium is a material that can meet strength, cryogenic toughness, and mass constraints. Now, Titanium is not cheap and it's a royal pain to machine, it costs around $9,500/t, but since it allows you to make a ship less than half the weight of 304L for a given yield strength requirement, it looks like a serious contender. 304L stainless yields at 30 to 31ksi. The cryogenic compatible Titanium alloys I've been reading about yield around 150ksi, with some having even higher YS values. That is literally 5X stronger than 304L, pound-for-pound.

If this ship's hull had to weigh 5,000t to meet the strength requirements for a given geometry, then you only need 1,000t of Titanium. 304L is not all that cheap, at $2,500/t, implying $12.5M in base metal cost, plus the cost to put that metal into orbit. Titanium would cost $9.5M, and be 5X cheaper to launch into orbit. There are foundries in the US and Canada that now have extensive experience producing Titanium forgings and castings. We would need 34 Starship flights, at $1M per flight, to put that much 304L into orbit, as compared to 7 flights to deliver the Titanium. In reality, we'll probably need more flights to deliver all the major components.

This makes a Titanium hull ship almost 3X cheaper than 304L, by virtue of base metal plus launch costs alone. Whatever price premiums the machinists charge for working with Titanium, it will pale in comparison to launch costs. If the ship is constructed from all-welded near-net-shape forgings and castings, then machining costs might not matter much at all.

We would first forge the habitation ring sections as donut slices, machine the sides of the raw forgings to precise specs, WPC treat the parts to relieve stress and reduce surface porosity, test assemble all of the slices of the ring or torus first, and then send them to orbit to be EBW welded into place using fixturing jigs and robotic welding. All hull parts would receive a plasma spray ceramic thermal barrier coating to reduce heat transfer in the event of a fire, similar to the components in the hot section of modern jet engines. If we need to control the part temperatures on-orbit to keep distortion consistent during welding operations, we would use carbon-fiber heater pads to heat the parts to a consistent temperature to assure dimensional accuracy during welding. As soon as the parts are welded, we wrap the structure with whipple shield material (Nextel fabric) to protect them from orbital debris.

RobertDyck · 2023-09-22 14:40:12

kbd512, you are insulting. You have done this many times and don't understand how agressive and offensive you can be. You said...

"kbd512 wrote:

A PhD in aerospace engineering already told you

I attended the only university in my province that offers computer science or engineering. It's still the only one with engineering. My parents couldn't afford to send me out of province. And student loans were not available. I did ask about a student loan at the time. University staff were condescending, wouldn't even allow me to get an application form. Administration at that university was arrogant. They would not allow any student to graduate unless he/she came from an upper class family. That sort of class distinction is not supposed to exist in this country, but the rich think think it does. Students from working class families were treated as cash cows. They were allowed to enroll, but not allowed to graduate. In my case they just didn't allow me to enroll in 4th year.

I've suffered individuals arrogant condescension my whole life. Just because I grew up in the blue collar side of a railroad town. Elementary school tried to recruit us to work in the sewage processing plant. Or drawn cartoons. Or track and field. Anything but success. When I tried to get ahead in math, giving answers that were a grade or two ahead of the class, they makes my answers wrong,. They dropped my grades as punishment for trying to succeed. They transferred me into remedial class for grade 6. The remedial teacher tried to get me transferred to a special school for the mentally retarded. So my mother has me tested. My IQ was 132 overall, but 155 in STEM. So the principal transferrede back into normal class.

Stop treating people with higher education as better than me. They didn't get a Ph. D. due to intelligence or hard work, they got it because they were given opportunities that the rest of us were denied.

At Mars Society conventions I got to meet individuals who work for NASA. I often tried to prepare. If I knew I would meet an individual, I would look up their current research project, look their educational background, then find something that would impact their research that comes from a field outside their education. I hoped to contribute that to a conversation to demonstrate that I'm one of them, to be accepted. But usually the individual just acted threatened. How dare a peasant know something they didn't? That was very disappointing. No matter what I can't win.

I thought Gary was different. He participates here. He has a degree in aerospace engineering, and a career. Something I very much wanted as a child. There was no work in aerospace when I was young, and the only university with engineering did not teach aerospace

I found individuals with a Ph. D. generally expect they know more about everything than those who don't. I could name one man from Ames in particular. But talking to these people revealed they have very deep knowledge in a very narrow subject. The price of a Ph. D. has been focus on their chosen field to such an extent that they're ignorant in most other fields. They don't have the broad knowledge of someone like me.

I've been told many times that a manager must have a broad knowledge. A specialist with a Ph. D. brings necessary knowledge, but that knowledge is too narrow and specialized to make management decisions for a large project. So lead or manager cannot be someone with a Ph. D. My knowledge appears to fit that.

I am disappointed that Gary chose to obsess over one aspect. I asked his help because the math formulae were not something I recognized, and I didn't know how to read. But Gary insisted instead on making a fundamental change that would kill the project. His suggestion is based on experience with solid rocket motors, not ship engineering. My designs based on established ship design that has been used since the 1800s. Since the early days of steam powered steel ships. And it's still in use today. So I'm very disappointed he won't even start.

So don't ever tell me to shut up, to blindly accept what someone else says just because they have a "Piled High and Deeper".

tahanson43206 · 2023-09-22 15:33:45

For all .... it seems to me it will be difficult to smooth things over, at this point.

I'm open to suggestions, but for now, I'll recommend that Dr. Johnson not offer his latest proposals for Large Ship.

We have a Zoom coming up ... it might be a good idea to take advantage of that opportunity.

(th)

kbd512 · 2023-09-22 17:19:00

RobertDyck,

Nobody is calling you dumb. If that's how you took what I said, then you took it the wrong way. I know damn good and well that you're plenty smart. People who show up here tend to be that way. Pretty much nobody who isn't above-average intelligence would take any real interest in living on another planet that is thoroughly inhospitable and unforgiving of any mistakes. The very fact that you do tells me all I need to know about how smart you are.

Offending you was pretty much the furthest thing from my mind when I wrote what I posted. My mind was wrapped-up in the details of how to get what you wanted to do to work, before it hit me that the only way to make that happen was to make the components heavier and more complicated to assemble, which seemed like the exact opposite of what I'd do if the general idea was to make the parts lighter and simpler.

I had no earthly idea about your childhood or life experiences, because I wasn't there, and have nothing to do with what others have done to you, good or bad or indifferent. If you've been treated poorly by others, that's a shame, but nobody here is deliberately trying to treat you poorly or insult your intelligence, least of all me. If you have to post a detailed explanation of how what I've done has offended you and go back to your childhood for context, isn't that a better than average indicator that there was no conscious effort on my part to offend you?

This was the one and only point made here:
A guy who has made a career out of designing high performance aerospace vehicles, and then taught aerospace engineering courses at university, said to us, "Well, I'm sorry fellas, but square pressure vessels won't work the way y'all want them to, cause the edges get blown out by the pressure." He was both formally trained to do what he does, which is aerospace engineering, then practiced doing what he was trained to do, and then taught others how to do what he does, for about as long as I've been alive. That seems like someone I'd want on my team if we were designing a gigantic pressure vessel, because that's what this ship is.

Having that hard-won knowledge allows us to move on to solving the next problem. There's a seemingly endless list of them that need solving. In the real world, no single person designs every part of a ship. It takes a team effort, generally a very large team, because it's a very complex task. This seems like a simple judgement call on sticking with tried-and-true structural engineering principles.

If we were designing a software program, and GW started talking about how the program needed to be written, I'm pretty sure that your lifetime of writing software would far outweigh his limited expertise on the subject. This is why you hire specialists when you have a highly specialized problem to solve. This is a structural engineering problem involving pressure vessel design for an aerospace vehicle. In other words, something neither you nor I have any real depth of knowledge about.

Engineers obsess over structural design details, because that's what engineers do. When it comes to pressure vessel design, that's a good thing!

Did you ever read how many different ideas I went through and then scrapped in the thread I created after the last dust-up over this?

Nothing I contemplated doing was because I wanted to do it "my way", or that it was "my design", because to me, the design was incidental to required function with concessions made to practicality. If the best design for a ball game happens to be a sphere, then so what? The end goal is to play a fun ball game, not get wrapped up in what the ball looks like to do that.

That's my entire line of thinking on this subject. I want to play an interplanetary colonization game, so what does the giant spaceship have to look like and do to accomplish that objective. If someone takes an idea I had that happened to be a good one, and calls it their own, but actually builds the thing I want built, I really couldn't care less. I'm not trying to prove anything to anyone. I just want the possibility of my children's generation being able to go and live on other planets. Whatever it takes to get there is purely the mechanics of making that happen.

Do you want a real working interplanetary spaceship, or your conception of what it should look like and how it should work?

tahanson43206 · 2023-09-23 06:52:22

A General Manager is a person who can lead a very large group to accomplish a complex project over an extended period of time.

Such a person will have advanced human relations skills, as well as a deep understanding of the overall interactions of the many parts that together make up the completed work.

Such a person is able to work with human beings of every possible background, by enlisting their talents to solve specific problems that the General Manager could not possibly solve.

General Dwight David Eisenhower is an example of such a General Manager. He was able to persuade multiple impossible personalities to work together, over an extended period of time, to accomplish one of the most complex tasks undertaken by humanity up to that time.

General Eisenhower was the son of a man who had a terrible temper, and a mother who was angelic in her kindness and even temper. General Eisenhower struggled with the temper he inherited all his life, but he succeeded in controlling his temper by finding safe opportunities to give vent to his frustration with the aforementioned impossible personalities. One technique used by General Eisenhower, and later President Eisenhower, was to hire subordinates who were willing to let him vent in private. According to a biographer of a recent book about the General, it was routine for an apology to follow the explosion.

In the present case, the Large Ship will require the participation of great numbers of specialists who have knowledge no General Manager can ever hope to acquire, because it takes decades of study and actual on-the-job experience to build up.

A person who might wish to become a General Manager might do well to learn how to manage frustration and anger, if such a person is unfortunate enough to have inherited susceptibility to an uneven temperament.

(th)

tahanson43206 · 2023-09-23 07:30:39

Here is ChatGPT's take on the qualities of a success General Manager...

ChatGPT
Thank you for sharing the report! It’s rewarding to know that I’ve been able to aid students in their language learning journeys.
As for your question about the personality traits of a successful General Manager (GM) in a large and technically sophisticated project with many unknowns, it is indeed a challenging role, requiring a balance between vision and adaptability, leadership and learning. Below are the crucial personality traits and skills required for such a role:
1. Visionary Leadership:
Clear Vision & Goals:
Able to articulate a clear and compelling vision and set attainable goals for the team to follow, even when not having a full understanding of the technical details.
Inspirational:
Can inspire and motivate team members by creating a positive and inclusive environment and aligning team efforts with organizational goals.
2. Effective Communication:
Active Listener:
Must listen intently to specialists and value their input, being open to feedback and new ideas.
Clear Communicator:
Able to clearly convey expectations, timelines, and objectives to individuals with varying expertise.
3. Strategic Decision-Making:
Balanced Judgment:
Weighing advice and data from different sources to make informed and timely decisions, and being willing to modify plans when proven incorrect.
Risk Management:
Assessing and managing risks effectively, taking necessary precautions and making strategic adjustments when required.
4. People Management:
Empathetic:
Demonstrating understanding and concern for team members' needs and feelings.
Conflict Resolution:
Able to mediate disputes and facilitate resolutions, maintaining a harmonious working environment.
Empowering:
Enabling team members to take initiative, encouraging innovation, and providing opportunities for growth.
Talent Identification & Development:
Can identify and enlist skilled specialists and help them grow and contribute effectively to the project.
5. Adaptability & Learning Agility:
Flexible:
Adapting plans and strategies as needed, being responsive to changing circumstances and new information.
Continuous Learner:
Eager to acquire new knowledge and skills, willing to learn from others and adjust preconceptions when necessary.
6. Focus & Discipline:
Prioritization:
Managing competing demands and ensuring that resources are allocated effectively towards the attainment of the goals.
Scope Management:
Maintaining focus on the project’s objectives and preventing scope creep by respectfully pushing back on ideas that don’t align with the project’s goals.
7. Customer & Result-Oriented:
Customer Focus:
Attentive to the needs and expectations of the end-users or clients, aiming to deliver value and exceed expectations.
Result-Driven:
Persistent in pursuing the project’s objectives and committed to achieving high-quality outcomes.
Conclusion:
The GM in such a scenario must create an environment where skilled specialists feel valued and are willing to align their efforts with the project’s goals. They should maintain a balance between holding the vision and being open to learning and adjusting their preconceptions based on specialists’ insights. The overall aim is to harmonize diverse talents and ideas to navigate complexities and achieve the intended goals successfully.

(th)

kbd512 · 2023-09-23 13:20:03

tahanson43206,

I didn't come up with this idea. Only RobertDyck had that level of vision.

I had three basic ideas to contribute to his design concept, all of which were purely about practicality and accepting basic physics, not what I wanted or what I preferred. It was not born out of a desire to change RobertDyck's design, either.

1. The forces involved in spinning an object this large and heavy are absolutely enormous. All gyro-stabilized objects, whether aircraft propellers or artillery shells, produce very large torque values that cause them to drift perpendicular to the direction of rotation. This is a well-known and well-understood effect. It doesn't depend upon having an atmosphere, because it's fundamental to how a gyroscope works. If you spun a propeller outside of an atmosphere with an electric motor, it would exhibit the same effect. Moreover, aboard ISS we are absolutely counting on this effect to control the attitude of the space station.

After examining how much electricity and gyro weight would be required for additional gyros to counteract the applied torque, I came to the conclusion that counter-rotation was a better option, because then the mass and power of the stabilization equipment comes in the form of a second habitation module, rather than additional purpose-built gyros.

I also proposed a second "fix", but it still involved counter-rotation on an outrigger gyro mounted to a boom on the hub section / central hull of the ship.

2. I proposed a torus rather than a ring, because it's the minimum weight option. A torus shape is better than a long slender ring shape for containing pressure. I didn't come to that determination to throw any shade on this idea. That was all physics / geometry / engineering. In other words, nothing to do with what I want, nor a desire to change RobertDyck's original design.

3. I proposed a greater level of interior compartmentalization, which was entirely about strength and crew survival. I like the fact that on the Russian Moskva cruiser, you can see from one end of the ship to the other. It think it looks pretty cool. Unfortunately, it also means that a fire started at one end can travel all the way to the other end of the ship. After a fire did start, that's exactly what happened. The ship was abandoned and lost. What happens in deep space if a ship is abandoned and lost? The entire crew and all passengers perish.

If a compartmentalized ship design is inconvenient, then how inconvenient is losing the entire ship and all aboard her?

Every design concession was a nod to practicality and survivability. That was it. There were no other reasons for my proposals. I wanted to see a practical design that could actually be built, that was a robust and survivable ship design intended to address the potential calamities that could befall her on a long voyage through deep space.

I went through an endless series of material trades for the hull and habitation ring. I initially thought aramid fabrics would be the bee's knees before considering the fire hazards and the creep characteristics of these fabrics. Over time, when highly loaded, said fabrics appear to permanently deform or stretch, like plastic, which is bad news bears for a long-lasting durable ship design of the sort that RobertDyck wanted. I eventually gave up on that.

I initially considered maraging steels because they have very high yield strengths (YS) of 250 to 350ksi, are very tough and hard, good notch performance at modestly cryogenic temperatures, and good corrosion resistance in general, by sharing many of the alloying elements of 300 series stainless. They're not cheap, but not as expensive as stainless. These ultra-high strength alloys are characterized by material processing costs, but they have remarkable performance. Aermet 100 and Aermet 350 are good examples of ridiculously tough steels that aircraft landing gear and high pressure gun barrels increasingly use. There are also products like Eglin ES-1, developed by the USAF, that only has a small Tungsten alloy content and no other strategic materials, and it retains most of its room-temp strength up to 950F. If we're talking about toughness, hardness, YS, and impact resistance down to modestly cryogenic temperatures, then nothing beats these UHS alloys.

I looked into 300 series stainless, but it's YS is only 30ksi. The only way you make stainless much stronger is by also making it more brittle, especially at cryogenic temps, where it does indeed become "stronger", in the same way that ordinary steels become stronger, at the expense of brittle behavior. Everything's a trade-off. For the strength levels 304L provides, there are high-Nickel Austenitic Ductile Irons that offer more YS than 304L, are weldable thanks to their high Nickel content, and were originally created to store LH2. ADI is not all that cheap thanks to the Nickel (roughly 1/4 of the alloy by weight), but still far less expensive than 304L. For 5 to 6ksi of additional yield strength over 304L, 1/4th to 1/3rd the material cost, and modestly lower mass per unit volume, you may as well have an "Iron ship" if 304L is your other option. Compressive YS is also better than 304L.

I then looked at more exotic stuff like Beryllium Copper, which remains ductile at cryogenic temps. This material is $5,000/t, has a YS approaching that of Titanium alloys, with the caveat that it's toxic to machine. It's not toxic to touch the finished product, but the metal is a specialty alloy that's even heavier than 304L, so the only advantage is 4X greater YS for 2X the cost of 304L. Very few machine shops will touch Beryllium anything, because you must take special precautions to machine it.

I wound up looking at Titanium alloys and found that they have the best mix of weight / strength / ductility at cryogenic temperatures, at the expense of increased cost for the base metal, difficulty welding in an O2 or N2 atmosphere (requires Argon or vacuum), and sensitivity to certain kinds of chemical attack that seem unlikely aboard a ship in deep space. I checked current Titanium metal prices, and it's currently selling for around $3,750/t. This is 2.5X what I thought it was based upon out-of-date pricing. Most metal alloys have become more expensive over time, whereas Titanium has become considerably cheaper as more is produced. 20 years ago, Titanium was $21,000/t.

Now I've started looking into metal foams based upon their ability to provide additional ballistic and radiation protection (X-ray, gamma, neutron) with about 20% to 30% of the weight of the base metal, plus their ability to increase the stiffness of a thin-wall pressure vessel made from sheet metal. This seems like a good compromise to address strength and weight concerns, and might allow us to use cheaper sheet metals in conjunction with metal foams to create strong but light habitation ring sections.

Here's an image of a what an 18m wide ITER tokamak pressure vessel looks like for comparison purposes (obviously not small):

For us to engineer something of similar size, given a 238m outer diameter, will require creative weight control measures and a highly disciplined approach to load distribution. The ITER pressure vessel section in the picture shown above weighs 450t.

GW Johnson · 2023-09-23 15:32:00

I meant to offend no one. I have tried to come up with ways to build a flight-weight pressure shell about the habitation concept Rob has come up with. The best I have come up with is based on concepts from air mattress manufacture, but adapted to sheet steels and welding technology.

Rob, I haven't said much about sandwich panels and those arcane formulas in that report, because I know little about that topic. Metal pressure vessels I understand, from aircraft fuselages, to solid rocket motors, to storage tanks, to aircraft and automotive fuel tanks, to railroad tank cars, to submarine pressure hulls. I'm not the narrow specialist you seem to think I am. Although perhaps 99% of PhD holders are, I am in the 1%.

Other than that, I will say nothing further until everything cools off.

GW

kbd512 · 2023-09-23 16:24:12

If the metal foams prove too heavy for the ballistic and radiation protection provided, it appears we have kevlar-based aerogels:
Researchers develop ultra-strong aerogels with materials used in bullet-proof vests

Steve Stewart · 2023-09-23 18:58:10

Rob,
Is this drawing of any value to you? If so you can have it. I drew this in AutoCAD (QuickCAD) based on a drawing you posted on this thread. Hope you don't mind. I don't have a whole lot of time, but I'd be glad to make changes to it if you'd like. I still need to fill in some of the other rooms with beds/bath. I can make the image bigger too if you'd like. The image shown is 625 x 722 pixels. I know you've got a presentation coming up and I don't mind lending a hand.

I could make two drawings. One from zooming in on the one room, so that the text is easier to read, and another zoomed out to show more of the rooms/ship.

Here is the url to the image:
https://i.imgur.com/Zq82XhW.jpg

Steve Stewart · 2023-09-24 12:48:29

Rob, Here is a closeup view with the detail added to more rooms. I also added english units to the metric units. I can take those out if you'd like.

Link to image:
1020 x 750 166K
https://i.imgur.com/WwOmF7r.jpg

Steve Stewart · 2023-09-24 12:49:43

Here is the same image shown above without detail in some of the rooms. I put the rooms in their own "layer". In AutoCAD I can turn "layers" off and on. In this image I turned off the layer with detail of the other rooms. I thought the image had less clutter this way. (I'm doing a screen capture and then pasting it into Paintbrush).

This image is a bit smaller since it has less detail. If this image is used in power point instead of the one above, it will help keep the power point file small.

Link to image:
1020 x 750 102K
https://i.imgur.com/x4KakKt.jpg

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