Large scale colonization ship

tahanson43206 · 2020-08-28 13:14:07

For RobertDyck re #200 and topic in general...

Thanks for the details of the passenger experience!! I like the dome effect, which would alleviate the otherwise rectangular box effect that Earthly cruise ship passengers experience.

Related question .... Your design allows for dual pressure ... It is also (potentially) a mirror for what passengers will experience on Mars.

Mars provides the outside atmosphere, and humans will pressurize their living and working quarters to values that they find comfortable, affordable and maintainable (as well as achievable)

It is possible you have already posted the amount of pressure and the mixture of gases you want for the passenger/crew quarters. I'll have to go back to look. However, if you decide to install the passenger/crew quarters inside a torus, then the torus itself could be maintained at Mars pressure, and even at the same gas mixture. That would provide passengers the opportunity to experience Mars conditions by taking excursions into the torus during the flight.

I'll see if I can generate a mockup of what that might look like later today.

(th)

RobertDyck · 2020-08-28 14:18:00

Pressure

First criteria is you must be able to get in a spacesuit, go through the airlock without any oxygen prebreathe time. For some reason, Shuttle used 1 atmosphere pressure. That's the pressure on Earth at sea level. Even locations such as Boulder Colorado has lower pressure. (Where the Mars Society held it's conventions for many years.) ISS also uses 1 atmosphere pressure. There's no reason to do this. Apollo command module started with ambient air at the Cape, but bled pressure during ascent until cabin pressure was 5.0 psi pure oxygen. Suit pressure was 3.6 psi pure oxygen. The reason Apollo used pure oxygen is so they don't require pressure vessels of two gasses, and the complicated equipment to maintain correct gas balance. However, Skylab used 5.0 psi total pressure with 60% O2 and 40% N2. Of course that changed as soon as astronauts got inside; some O2 was consumed and converted to CO2. But still, you get the point. Human metabolism is dependant upon partial pressure of O2. Earth at sea level is 14.69595 psi with 20.946% O2, 78.084% N2, 0.9340% Ar, 0.0407% CO2 (as of April 2019), trace gasses and water vapour. This means partial pressure of O2 at sea level is 3.0782 psi. You could round that to 3.0 psi. Yes, rounding, but remember total pressure and therefor partial pressure drops with altitude. Partial pressure O2 at Boulder Colorado is 2.54 psi.

Initial work by Apollo engineers before they actually flew in space was to use 3.3 psi pure oxygen in spacesuits, and 3.0 psi pure oxygen in the cabin. The justification was if the suit experienced a 10% pressure leak, oxygen would still be the level astronauts were used to. So based on that...

I propose 3.0 psi pure oxygen in Mars spacesuits. An MCP suit is easy to make at that pressure, but very difficult at 4.3 psi. The EMU spacesuit used by Shuttle and ISS uses 4.3 psi. Astronauts require 17 hours of oxygen prebreathe to flush nitrogen out of their blood before decompressing to suit pressure. They use higher suit pressure to reduce that prebreathe time. If they didn't flush nitrogen out, decompression would give them the Bends. Again, Apollo solved that by using lower cabin pressure, so difference between cabin and suit pressure did not require any prebreathe time.

Using the 10% rule, I propose cabin use 2.7 psi partial pressure oxygen. Again, Boulder Colorado has 2.54 psi partial pressure oxygen, so this is not extreme. The rule is maximum partial pressure nitrogen in the higher pressure environment must be no greater than 1.2 times total pressure of the lower pressure environment. So with suit pressure of 3.0 psi, maximum partial pressure nitrogen the cabin is 3.6 psi. I propose using 3.5 psi to stay away from the extreme. Then add argon. Mars atmosphere has argon, Earth has argon. If we make the nitrogen:argon ratio the same as Mars ambient, then extracting it is easier. But on the ship we can use anything we want. Besides, percentage N2 and Ar in Mars atmosphere measured by Viking 2 lander in 1977 is not exactly the same as modern rovers. It appears gasses can vary from location to location, and year to year. I thought only CO2 would vary, but measurements by modern rovers show these two gasses vary a little as well. So if we add 1.148 psi partial pressure argon, that adds up to pressure 1/2 of Earth at sea level.

Summary:
2.7 psi O2
3.5 psi N2
1.148 psi Ar
Total: 7.348 psi total

Again, human metabolism will convert some O2 into CO2, and we exhale and sweat moisture so there will be some water vapour.

::Edit:: If we make the ratio of N2:Ar the same as Mars ambient, that makes harvesting on Mars easy and simple. The Viking 2 lander in 1977 measured 2.7% N2, 1.6% Ar by volume. Using that: 3.5 psi N2 (see above) multiply by (1.6 / 2.7) = 2.074 psi partial pressure argon. That would increase total pressure to 8.274 psi. Composition of Mars atmosphere in Wikipedia is 2.6% N2, 1.9% Ar. There are references on the Wikipedia page to justify that. If we use those values we get 3.5 psi * (1.9 / 2.6) = 2.5577 psi partial pressure Ar. That would make total pressure 8.7577 psi. If you add no argon at all, total is 6.2 psi, which is still higher than Skylab. But doing that on Mars requires extra effort to separate nitrogen from argon. So the summary shown above is a simple compromise, resulting in exactly half Earth pressure at sea level.

tahanson43206 · 2020-08-28 17:11:11

For RobertDyck re #202

SearchTerm:AtmosphereSpacecraftAnalysis
SearchTerm:AnalysisAtmosphereSpacecraft
SearchTerm:AtmosphereMarsSuit

http://newmars.com/forums/viewtopic.php … 04#p171604

Follow up ... would you agree (in principle) with the concept of making the interior of the spacecraft atmosphere equal to that of Mars itself?

As I read your post (will read it again later to try to absorb more) It seems (to me at least) that you have covered the needs inside the living quarters, and inside the Mars suit, but I may have missed a confirmation that you like (or at least will consider) the idea of making the atmosphere of the part of the space craft outside the living quarters equal to or as similar as possible to that of Mars. A pure CO2 atmosphere would have a number of logistical advantages for the outbound trip, and if you want to refresh that atmosphere with Mars' own atmosphere while there, you would (should) be able to do that.

An immediate advantage would be that you could vent the CO2 generated inside the living quarters to the middle region, thus avoiding the expense (energy cost) of storing it or otherwise processing it.

Edit#1: I printed the image you posted at imgur.com, and will mark it up later (today most likely) with the dimensions you added to the related post(s).

My intention would then be to see if I can recreate the outline in Fusion 360 2D Sketch mode.

(th)

Last edited by tahanson43206 (2020-08-28 17:13:53)

RobertDyck · 2020-08-28 17:13:27

Yes. My justification is a spacesuit designed for Mars surface, not Earth orbit, and air in a habitat on Mars surface. Since the ship will carry settlers to Mars, make both the gravity and air match what they will encounter in a habitat on Mars.

tahanson43206 · 2020-08-28 17:15:54

For RobertDyck re #204

Bravo!

(th)

RobertDyck · 2020-08-28 18:12:21

We discussed serving passengers meals in 3 shifts. Same could apply to exercise equipment, etc. To make this convenient, passengers could be assigned a time zone. They will probably come from different parts of the world anyway. Passengers time zones: UTC (aka Greenwich Mean Time), Pacific Time (UTC -8 hours), and China Standard Time aka Australian Western Standard Time (UTC +8 hours). This provides 3 shifts exactly 8 hours apart.

SpaceNut · 2020-08-28 18:26:39

goal is

Summary:
2.7 psi O2
3.5 psi N2
1.148 psi Ar
Total: 7.348 psi total

The surface pressure is only about 610 pascals (0.088 psi) which makes the partial pressure of 2.7% N2, 1.6% Ar only 0.002376 psi of N2 and 0.001408 psi of Ar...

to achieve we need 1,473.0639 cubic inches of mars N2 and 815.3409 cubic inches of mars Ar to get the pressure for the psi

its about volumes to get the desired pressure

RobertDyck · 2020-08-28 19:39:58

SpaceNut: I gave a presentation at a Mars Society convention several years ago. The goal was to harvest gasses from Mars atmosphere other than CO2. The method: compress Mars atmosphere from ambient to 10 bars. Yes, that's more than 1,000 times compression. Filter out dust at the intake. Freezer coils in the bottom of the pressure bottle would chill to -100°C. This would freeze out dry ice. Most of Mars atmosphere is CO2, this leaves everything else. What little moisture is in Mars atmosphere would freeze out with the dry ice. Removing moisture is not intended, but there's no way to prevent it. Since Mars atmosphere is over 95% CO2, this will drop pressure in the pressure bottle. A pressure sensor will detect this, activate the pumps to draw in more Mars atmosphere to top up to 10 bar pressure. This will concentrate everything other than CO2. Unfortunately Mars atmosphere has carbon monoxide (CO), and removing that much CO2 will concentrate CO to lethal levels. So...

A rhodium based catalyst at the top of the same bottle will be warmed to +24°C. Yes, freezer coils in the bottom and small heater in the top will waste energy. No way around it. The catalyst will combine CO with O2 to form CO2. There's not much O2 in Mars atmosphere, but more than CO. And since one molecule of O2 will convert two molecules of CO into CO2, that means there's more than twice as much O2 as required. There's also a trace amount of ozone (O3). The same rhodium catalyst will break that down into oxygen: 2 O3 -> 3 O2.

Continue operating until pressure is stable, pumps no longer activated. And carbon monoxide reacted so there is no CO what so ever within detection range of the sensor. Once this happens, seal the intake valve, power off the pumps, and turn off power to the heater. Continue to freeze until the entire chamber is stable -100°C. That will drop pressure a little below 10 bar, but that's Ok. Once pressure becomes stable, release gas very quickly into larger holding tanks. The idea is to release quickly so dry ice does not have time to sublimate. Once pressure is stable between holding tanks and the freezing tank, seal valves. Then heat the freezing tank to sublimate dry ice into CO2 gas. That CO2 gas can be used for something else.

Resulting gas is something I call "diluent gas". I calculated an estimate of the result, assuming starting atmosphere measured by Viking 2 lander.
CO2 0.74935%
N2 61.0%
Ar 36.1%
O2 2.1%
Ne 0.0056%
Kr 0.00068%
Xe 0.00018%

Add oxygen to this, and you have air you can breathe in a habitat. CO2 is higher than you would like, it would smell stuffy, but that's the best you can do with a freezer. Removing more CO2 requires a sorbent. But life support has a CO2 sorbent, so just run life support.

SpaceNut · 2020-08-28 19:58:36

Each 10 bar tank full at unknown volume leave 0.5 bar of wanted gasses. It the volume at pressure that need once they fill the habital space and rather than throw the dry ice out we need to let a moxie unit convert it to o2 in between each gas storage cycle as leaving it frozen in the tank would reduce the volume on each in take meaning increased energy cycles.

Need to calculate o2 from unit.

CO2 has a molecular weight of 44 g/mol
1 kg CO2 = 1000 g × (1 mol/44 g) = 22.7 mol CO2

numbers need correction for dry ice change as the below is gaseous
V=nRT/P, V=(22.7)(0.0821)(300)/1 = 559 L CO2 at 27°C (300K), 1 atm

RobertDyck · 2020-08-28 20:34:52

The point of this was to harvest N2 and Ar. Robert Zubrin and his staff produced MACDOF (Mars Atmosphere Carbon DiOxide Freezer). MACDOF is far more energy efficient to harvest CO2. But all it collects is CO2. My design collects N2 and Ar. As I said, you could sublimate the dry ice to produce CO2 gas, and collect that separately. No point in throwing out dry ice, but do not think that dry ice is the primary purpose of this. But yes, you do have to sublimate the dry ice to remove it before the next cycle. Note: This will slowly collect water ice. After several cycles you will have to melt that and drain the water.

I didn't even bother calculating how much CO2 would be collected, or how that CO2 could be processed. The goal was N2 and Ar.

SpaceNut · 2020-08-28 21:05:25

That's fine we have the standalone system designed to get what it's designed for.

If we also allow sublimation to generate power during the seperation process and them feed that power into moxie to get the bang for the buck as well just looking at the big picture.

The output from moxie is o2 and co which is vented to the atmosphere unless its proven to be a large enough quantity to save for a subsequence value....

https://cryocarb.com/dry-ice-faqs/

https://dryiceinfo.com/traveling.htm

https://www.dry-ice-machine.com/why-are … r-dry-ice/

https://www.nanocool.com/calculator

https://www.exportersindia.com/indian-s … achine.htm

http://static1.1.sqspcdn.com/static/f/5 … NG5rZC8%3D
ICE HANDBOOK FOR ENGINEERS

http://www.r744.com/files/pdf_088.pdf
Physical Properties of Carbon Dioxide

RobertDyck if you would like post in a separate topic I will do so..

tahanson43206 · 2020-08-29 06:06:42

For RobertDyck re #208

Thanks for re-posting the summary of your paper at the Mars Society Conference!

I've added the specialty to My Hacienda ... Production of breathable atmosphere would be a steady employment for a fair number of folks.

SearchTerm:AtmosphereBreathable
SearchTerm:AirForBreathing
SearchTerm:ProcessToMakeAir

(th)

tahanson43206 · 2020-08-29 08:49:34

For RobertDyck re 3D Model

The image below is a first cut using Sketch. I thought I'd pause to be sure you want to proceed down the torus (enclosure) path.

That shape has a number of advantages for your vessel (it seems to me). As you can see in the sketch, it provides ** all sorts ** of room for supplies, radiation shielding, exercise area (wearing Mars suits of course) and potentially window views of the cosmos outside.

In this plan, the habitat would be inside the enclosure, protected from radiation and debris floating (or speeding) through the vicinity.

The outer shell of the torus would only need to hold Mars level atmosphere (900 pascals or so).

Any leakage from the habitat into the torus would be recoverable. CO2 from the habitat could be vented directly into the torus.

I can try for fine tuning the sketch after you provide feedback.

I started reading up on the "Revolve" command. I've not tried it, but assume it will allow generation of a ring to which spokes could be added.

(th)

RobertDyck · 2020-08-29 10:26:43

No. My plan is a hull with the dimensions previously stated.

tahanson43206 · 2020-08-29 14:13:05

OK ... I'll go back to see what you specified for thickness of the walls. Whatever that thickness is will be carrying the forces from the propulsion unit and transferring them to the parts of the ring that are not directly downstream of a spoke.

In your original sketch, you show the spokes radiating at 90 degrees from the propulsion unit. That means the propulsion unit will be trying to tear the spokes out at the root, and the spokes will be trying to rip free from the habitat ring.

Do you want support members to add strength?

They would be the hypotenuse of a right triangle, if you decide you want to see what they'd look like.

(th)

RobertDyck · 2020-08-29 15:31:41

And I thought my design was big. People keep trying to make it bigger. I started by saying Elon Musk's description of Starship 2 was too big. If you want to build something that big, you can do this. But you want to make it bigger. I haven't worked out mass, or acceleration during thrust. Higher specific impulse engines tend to produce less thrust but over a greater time. That would apply less stress to the structure. Cylindrical spokes have intrinsic structural strength, but is it enough? Do we need diagonal struts? Don't know.

tahanson43206 · 2020-08-29 17:31:00

For RobertDyck re #216

It would make sense for me to give you the ring you specified with the spokes in whatever mode comes most easily, going to the existing propulsion unit.

You can look at it and make changes as needed.

Just FYI ... your choice of dimensions is a (small) problem ... I'm going to restart with centimetres so I have a more accurate grid to work with.

That will mean the height will be 240 cm (not counting arches) and width of 1900 cm. It won't make any difference in what you see.

I could change back after trying the cm scale. I'm not sure what the effect will be on the monitor.

I'll try to have something for you to look at tomorrow (Sunday Earth Calendar).

Edit #1: Something to keep in mind is that the walls between rows of the cabins will have a slight angle away from 90 degrees to the floor, because they are rays emanating from the hub. At the scale of this vehicle, the departure from vertical may not be noticeable in only 2.4 meters of height.

Edit #2: The walls between cabins along the rows will be parallel.

In any case, those walls will help to provide whatever strength this vehicle is going to have.

Walls of zero thickness is the current design.

When you do get around to deciding on wall thickness, sound proofing would seem to be worth considering, in addition to structural strength.

Edit #3: Design of cruise ships would be a starting point for thinking about the Circle Y concept.
(th)

Last edited by tahanson43206 (2020-08-30 05:38:19)

RobertDyck · 2020-08-30 10:29:27

tahanson43206 wrote:

Just FYI ... your choice of dimensions is a (small) problem ... I'm going to restart with centimetres so I have a more accurate grid to work with.

I chose 1:100 because it made sense for the drawing on paper of a few cabins. You can use whatever scale works for your software.

tahanson43206 wrote:

Something to keep in mind is that the walls between rows of the cabins will have a slight angle away from 90 degrees to the floor, because they are rays emanating from the hub. At the scale of this vehicle, the departure from vertical may not be noticeable in only 2.4 meters of height.

That's true for walls between cabins, but corridor walls are parallel to the hull walls so 90° to the floor.

tahanson43206 wrote:

The walls between cabins along the rows will be parallel.

Exactly

tahanson43206 wrote:

Walls of zero thickness is the current design.
When you do get around to deciding on wall thickness, sound proofing would seem to be worth considering, in addition to structural strength.

Laziness. ISS module harmony has a 5.1cm (2") thick aluminum alloy pressure hull. But it also has a goldised Kapton blanket, and panels for protection from micrometeoroids made from a composite sandwich of stainless steel and 6061-T6 aluminum alloy, and a secondary barrier of Kevlar/resin. What's the total thickness?

Interior walls? Office walls on Earth are 3.5" galvanized steel studs with 1/4" drywall on both sides. We don't need flimsy sheet metal studs, they could be composite like corrugated cardboard but made of steel sheet. That could make them thinner. And houses in the north have wall panels with decorative strips covering the cracks rather than plaster. Something like wallpaper surface, but the walls feel more firm than drywall. What are those? Could we make interior walls also 5.1cm thick?

Yea, I again mention steel. I heard a few engineers talk about service life of aluminum. A military technician mentioned after aircraft have flown a certain number of hours, their spine is cut with a torch to ensure no one tries to fly. I found that shocking! I also argue the service life of DC-3 aircraft, but it has me worried.

Ps. I said cabin size is measured from centre-of-wall to centre-of-wall. A construction trick that my grandfather used when he built houses. Makes measurements easier. So I didn't have to specify wall thickness.

tahanson43206 · 2020-08-30 11:16:35

For RobertDyck re #218

Thanks for the 3.5" studs plus dry wall suggestion.

In homes with walls of that type, and without any sound deadening (which is the case with most homes I've lived in or visited) sound travels easily between rooms. The practice of the cruise ship industry would seem (to me at least) a good place to start if you are thinking about providing an enjoyable experience for people who are going to be cooped up for six to eight months.

In the mean time, I think that a 10 centimetre thick wall is a good place to start. Such a wall can carry conduit for movement of liquids and electric currents.

So far you've left HVAC as a pending requirement, but (as with everything else) that can be added.

Every hotel or motel room I've visited in the US is equipped with private bath. I've not been on a cruise ship, but I'd be astonished if even the least cost cabins did not include those amenities.

I sympathize with the mental stretching you are going through, as you move from vision to architectural drawings to present to a funder.

There may well be others who are thinking along similar lines, but (at this point) I am not aware of them.

One option that (hopefully) ** someone ** will pursue is offering Mr. Musk a ready-to-go solution for give his Starship passengers a simulated Mars gravity without his having to do anything. All he would have to do is to park his Starship in the docking cradle of such a ship, and use the Starship itself as the propulsion unit.

Meanwhile, as I understand your initiative, you're going for a larger vessel with more amenities, suitable for up to ten Starships worth of passengers.

(th)

kbd512 · 2020-08-30 12:19:24

Robert,

Repairing a crack in an Aluminum alloy structure is easier than steel (done correctly, it doesn't change the temper of Aluminum, but will locally change the temper of steel and requires gradual "air cooling" here on Earth for 4130 to prevent cracking; I have no idea about stainless so you'll have to ask a metallurgist, which I've already done for 2019 / 2024 / 6061 and normalized SAE 4130 tubing) and there are multiple forces to take into account for a spinning gravity wheel (primarily tension from spinning for the torus, hoop stress from pressurization, but also shear and we're talking about a very large structure of significant mass). The steel may ultimately last longer, at the expensive of considerably increased weight and thinner hull sections that make protection against radiation and MMOD more difficult. It's worth noting that most of the MMOD shielding is Aluminum. Either way, orbital assembly that includes welding will be required, so how much of a PITA do you want construction to be?

For aircraft like fighter jets, the parts that get torch-cut to prevent re-use are typically wing boxes and those are made from Titanium, not Aluminum. I don't know what the "aircraft spine" is that you're referring to is, but I presume you're talking about the center body section where the engines are mounted and wing spar attachment points. That is made of Titanium, not Aluminum, in the Hornet and Super Hornet jets that Canada and the US Navy flies. The wing spars are primarily made from Aluminum alloys, rarely Titanium, but I've never heard of steel of any kind being used for these parts in a western-designed fighter jet. Modern airliners also have Titanium wing boxes and Aluminum or composite spars, but no steel.

The latest airliners use carbon fiber tape in their fuselage pressure hulls wrapped around male or female molds. Boeing uses male molds so the inner part dimensions are consistent, whereas Airbus uses female molds so the exterior dimensions are consistent. There are benefits and complications associated with using both methods. The Boeing method assures that all attachment points inside the vehicle are dimensionally consistent such that identical interior parts can be fabricated, but can't assure the exact flying qualities on account of exterior dimension deltas between different airframes. The Airbus method has issues with attachment points being inconsistent and requires a minor degree of parts customization, but the exterior dimension are identical for all vehicles produced on a given mold. The Boeing airframes are cheaper to fabricate since every station is identical between different parts produced on the same mold, if that's at all important to you. The new "carbon forging" method from Lamborghini assures that both dimensions are identical and less expensive chopped carbon fiber can be used, rather than more expensive roving or tape or woven fabric.

Despite the fact that all of our fighters have highly stressed-skins, the maintainers keep track of flight hours on the Titanium wing boxes and shear bolts that connect the box with the spars or flying surfaces or the engines or landing gear, not Aluminum skins. There must be some reason for that. The newer stealth jets have composite skins, which require another level of testing to determine serviceability. In any event, fighters from the F-4 onwards used Titanium wing boxes and there are fatigue life limitations for those structures and most of those are machined from blocks or plates of Titanium alloy that are electron beam welded into a wing box.

We also torch cut ordnance steel gun barrels used in lightweight automatic cannons installed in aircraft. Those steel parts are also so highly stressed that they are more or less guaranteed to fail within so many thousands of rounds fired through them and therefore require routine replacement with use. As GW pointed out, these ferrous alloys have stress-strain curves where part life is theoretically infinite if the part doesn't oxidize, but the tradeoff in aerospace applications is weight and so even the steel parts have fatigue life limitations.

In your opinion, what is a reasonable service life limitation and are you willing to consider on-orbit repair to weld cracks?

If you have to inspect for and repair cracks every 20 years or so, is that an acceptable operational constraint?

If we had a robot that moves around the pressure hull, checking for cracks using NDT, would that change your opinion of using lighter weight materials and living with the fatigue life limitations?

RobertDyck · 2020-08-30 13:41:38

Cruise ship composite cabins...

Walls appear to be some sort of thin facing over yellow fibre core. I noticed mineral wool is more stiff than fibreglass, and flame resistant, so perhaps they use that. This design shows cabin walls not weight bearing, our ship would require walls to hold the roof to the floor against air pressure, so stronger.

I suggested a covered raceway along the ceiling against the wall with bathrooms. This would carry all pipes and cables. That's why all bathrooms/restrooms are along the wall with the corridor.

tahanson43206 · 2020-08-30 13:42:00

For topic update ...

The constraints I am experiencing are (no doubt) novice related. The Fusion 360 program seems resistant to doing some maneuvers at an angle. The gear program is (obviously) able to manage angles, but in my attempts so far I'm seeing resistance.

The spoke you see installed between the habitat ring and the center hub is there because it is laid out on an X axis.

It is 10 meters thick and 19 meters wide, and long enough to join the hub and the ring.

All attempts so far to try to create spokes laid out at 120 degree intervals have yielded distorted shapes.

I'll try again soon.

If you were willing to go for 90 degree spokes that would solve that particular problem, but let's wait to see if the three spoke configuration will work.

As reported earlier (in another post) the main body cannot be rotated once it is defined.

One helpful feature of the design tool is that it tells the operator at drawing time what the angle is between one line and another, and how long the new line being drawn is. The complication is that due to the Snap-To feature, the angle cannot be exactly 30 degrees (for example) and the length cannot be exactly 10 meters (for example). That makes sense ... a component drawn at an angle cannot be rendered in integers. The Snap-To feature can be disabled, but I'm not quite ready to try that.

(th)

Last edited by tahanson43206 (2020-08-30 13:47:55)

RobertDyck · 2020-08-30 17:25:45

kbd512 wrote:

I don't know what the "aircraft spine" is that you're referring to

Individual I spoke with didn't specify further. We were talking about C-130 Hercules.

kbd512 · 2020-08-30 17:48:19

Robert,

IIRC, the C-130 center wing boxes were made from 7075-T6. All of the C-130s that had failures had more than 40,000 hours on the clock. The 7075-T6 material was replaced with 7075-T73 alloy and beefed up in certain areas to deal with stress corrosion cracking. Some stringers were 7075-T73 and replaced with 7075-T6. The alloy switcheroos were to either increase fatigue life or increase corrosion resistance.

The operators were also routinely overloading them, thus not flying them within design specifications, so fatigue failures occurred sooner than expected. The military does this from time to time because they know that all airframes are designed with extra margin for fatigue resistance and failure. Still, the airframes with cracks had 40,000+ flight hours on them and were only grounded at 50,000 hours.

If we rack up 50,000 flight hours, that's 5.7 years of continuous service. How about we use stainless steel for structural support members for the center section and spokes of the wheel and use Aluminum alloy for the torus sections?

Here's a pamphlet on the service bulletin from Lockheed-Martin:

Lockheed-Martin Service News - Volume 30, No. 2, 2005

We have to economize on mass somewhere, so if we make the most highly stressed members from stainless, then we should have enough mass margin for the pressurized living quarters in the torus and a reasonably good fatigue life. The ISS modules have been up there for two decades and still going strong. Eventually they'll fail, but 20+ years between refurbishment or replacement seems acceptable for a high performance aerospace vehicle.

RobertDyck · 2020-08-30 18:05:11

Found a PDF document with a lot more details about composite cabins. Uploaded images for wall panels...
LiteCab™ Lightweight Composite Cruise Ship Cabins

CURRENT CABIN CONSTRUCTION
Typically:
Panels manufactured from zinc coated mild steel
Filled with mineral wool typically 20-25mm thickness
Internal surface finish of approved vinyl film
Sometimes Steel or Aluminium Foil on the outside surfaces of the cabin
Modular construction – assembled in situ or pre-assembled
Wet units are attached as a separate bolt-on unit
WHY CHANGE IT?
Reduction in topsides weight
Improved fuel efficiency = lower emissions
Improved stability
Increased payload of vessel = more cabins = increased revenue
Reduced transportation costs, easier handling
More sustainable / less embodied energy
Lower carbon footprint
Easier maintenance
Quicker repairs
PROJECT AIMS
The project would design, engineer, manufacture and fit-out a prefabricated accommodation module typical of cabins currently installed on cruise and other passenger carrying vessels.
The cabin would be manufactured from non metallic composite* materials.
The project aimed to reduce weight and reduce the carbon footprint whilst also meeting current prescriptive requirements for incombustibility, thermal boundary, smoke and toxicity & flame spread requirements, etc. as required by IMO SOLAS regulation.
Reducing vessel weight improves vessel efficiency and falls within the scope of the TSB grant competition under which the project sits.
* composite = entirely non metallic polymer composite materials
IMO / SOLAS REQUIREMENTS
Strict requirements for materials forming Fire Boundaries (cabin walls & deckheads)
Satisfy the prescriptive requirements of the IMO FTP Code (Fire Test Procedures Code)
Fire barriers shall be manufactured from Non-Combustible materials** (IMO FTP Code Annex 1 Part 1)
Thermal boundary classes are also determined by SOLAS II-2
**Polymer composites: Conventional polymer resin systems and some reinforcements are combustible (ISO 1182) even though they can be made with Class 0, fire retardant, low flammability, etc. characteristics. Thus they fail at the first hurdle.
ALL-UP WEIGHT DATA
Typical present day fitted-out cabin weight: (project base case) 1,935kg
Project cabin all-up weight: (shell, wet unit, fitted-out) 972kg ~49% reduction

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#201 2020-08-28 13:14:07

Re: Large scale colonization ship

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Re: Large scale colonization ship

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Re: Large scale colonization ship

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Re: Large scale colonization ship

#205 2020-08-28 17:15:54

Re: Large scale colonization ship

#206 2020-08-28 18:12:21

Re: Large scale colonization ship

#207 2020-08-28 18:26:39

Re: Large scale colonization ship

#208 2020-08-28 19:39:58

Re: Large scale colonization ship

#209 2020-08-28 19:58:36

Re: Large scale colonization ship

#210 2020-08-28 20:34:52

Re: Large scale colonization ship

#211 2020-08-28 21:05:25

Re: Large scale colonization ship

#212 2020-08-29 06:06:42

Re: Large scale colonization ship

#213 2020-08-29 08:49:34

Re: Large scale colonization ship

#214 2020-08-29 10:26:43

Re: Large scale colonization ship

#215 2020-08-29 14:13:05

Re: Large scale colonization ship

#216 2020-08-29 15:31:41

Re: Large scale colonization ship

#217 2020-08-29 17:31:00

Re: Large scale colonization ship

#218 2020-08-30 10:29:27

Re: Large scale colonization ship

#219 2020-08-30 11:16:35

Re: Large scale colonization ship

#220 2020-08-30 12:19:24

Re: Large scale colonization ship

#221 2020-08-30 13:41:38

Re: Large scale colonization ship

#222 2020-08-30 13:42:00

Re: Large scale colonization ship

#223 2020-08-30 17:25:45

Re: Large scale colonization ship

#224 2020-08-30 17:48:19

Re: Large scale colonization ship

#225 2020-08-30 18:05:11

Re: Large scale colonization ship

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