Large Ship Component Manufacture on Earth

tahanson43206 · 2022-03-19 12:47:49

Large Ship Prime is: Large scale colonization ship by RobertDyck

This topic is offered as a way to consolidate posts about manufacture and testing of components for Large Ship to be done on Earth.

Posts entered into this topic will (hopefully) remain on topic, so that a future Large Ship planner can focus upon the topic.

It should be noted that this topic is intended to cover both the design unique to Large Ship (Prime) and other designs.

In both cases, what I am looking for are contributions that will be useful and hopefully valuable to future builders.

(th)

SpaceNut · 2022-03-19 18:59:32

The large ship has many items that will be brought from earth to be installed into the large ship.

While some items will be standardized with furnishing, I am thinking more in line with the types of medical equipment or the appliances in the kitchen.

Special items such as the computerized navigation controls will be assembled and wired from much small sections.

SpaceNut · 2022-03-23 19:14:57

Many items will attempt to be commercial off the shelf for use in the large ship to keep it from becoming an engineering exercise. It would also be the same for the mars surface we want to provide goods that are low cost but we know that they will function.

What are the components?

tahanson43206 · 2022-03-23 20:14:12

For SpaceNut re #3

Your observation about what a component is (or is not) inspired me to try to understand the term a bit better.

In this context, we are considering an engineering project .... There may be components available off the shelf. We should definitely look for opportunities to use existing components when it makes sense to do so. However, we ** are ** talking about building a structure/system that has never existed before.

I asked Google for help, and it came back with some snippets:

What is component? - Definition from WhatIs.com - TechTarget
whatis.techtarget.com › definition › component
In programming and engineering disciplines, a component is an identifiable part of a larger program or construction. Usually, a component provides a ...
What is Component Engineering? - Learn.org
learn.org › ... › Engineering and Engineering Technology FAQs
Component engineering involves the selection, maintenance, design and construction of smaller parts for larger machines. Component engineers are...
Component engineering - Wikipedia
en.wikipedia.org › wiki › Component_engineering
Component engineering is an engineering discipline primarily used to ensure the availability of suitable components required to manufacture a larger product.
Missing: hardware | Must include:hardware

It seems to me that for the purposes of ** this ** topic, we would not be talking about supplies that might be brought aboard ship to serve passengers or crew.

What I had in mind when opening this topic was such elements as the Habitat module (as you pointed out), the Central Hub (again as you pointed out) and a complex set of parts that would provide for flow of forces between the central hub and the habitat ring, ** and ** the cylindrical passageways that would permit passengers and crew to move between the central hub and the habitat ring.

The passageways should under NO circumstances carry ANY of the load between the habitat ring and the central hub. They are incapable of handing any lateral load whatsoever, and should not be subjected to compression or tensile loads.

Early drawings/renderings of Large Ship (Prime) are artists' drawings only and under NO circumstances should be construed as engineering drawings, or even engineering suggestions.

(th)

SpaceNut · 2022-03-23 21:14:16

Such things then as a heating and cooling would be made from earth testable parts but integrated into the large ships overall ability to control the environment from a central control console. They would make use of zone like sensing assemblies to feed information to they console for user input to make or keep current settings.
The system would also contain ventilation fans and sensors for co2 levels to cause suction to draw off any excess through to a processing assembly that could be a compressor and storage tanks.

Other such components would be in the waste and water dispensing and recovery of the plumbing. The total system would be the remaining purifying and other sanitation aeration of this. Other processes to make some into chemical fertilizer and food for the chloroplast system is another of the component builds that will spread out through out the large ship as well.

tahanson43206 · 2022-03-23 21:21:28

For SpaceNut re #5

Thanks for picking up on the theme!

it seems to me that while Large Ship has never been created before, large aircraft are a pretty good model to consider.

RobertDyck has been using ocean going passenger vessels as the starting point for his vision, but that starting point can only take this project so far.

Your post gives a sense of how to think about the components of a large system such as Large Ship ...

(th)

tahanson43206 · 2022-03-24 06:07:25

For SpaceNut re topic ...

There is a need to precisely identify the components of Large Ship ....

The problem is complicated because we have two major variations already, and more will develop naturally, as participants focus on particular features.

The obvious major split already is between the Unitary Rotation model, advocated by RobertDyck, and the Counter Rotating model advocated by kbd512.

At the moment, it appears (to me at least) that only the Unitary Rotation model is receiving attention. That could change, but for the time being, it seems safe (again, to me at least) to concentrate on components of Large Ship (Prime).

The Structure would be hierarchical ...

Major component (eg, Habitat Ring)
Sub component A - (eg, pressure wall at circumference of ring)
Sub component A1 - (eg, panel shipped from Earth to be welded in LEO)
Dimensions/measurements/materials/characteristics ** and ** provider details including bid prices
Provider bids - there should be a minimum of three bids, in tried and true US standard practice

The natural structure for organization of information along these lines is a database.

Microsoft (and other major vendors) offer free cloud storage space for experimental projects.

It is well within the capability of ordinary individuals such as those who've become members of NewMars forum to develop applications that run in one or more of these free online services.

The FluxBB forum data structure (as we've noted previously) is not optimized for long term data storage. However, the Free Dropbox facility we've begun using appears to be reliable and worth considering as a residence for a Bill of Materials database.

Open Office is a free software (there are others, such as Libre Office) and these systems run on every (major) operating system.

it ** should ** be possible for anyone currently a member of the forum, or likely to be added in the future, to run this software.

Thanks again for your participation in and support of this new topic.

(th)

SpaceNut · 2022-03-24 20:43:01

Components are the smaller pieces that are used to make up the system in which they are made to make it work as intended.

Managing the systems for use is why we need to come up with what they are first and not the unknown list of parts as to where they could be used.

A system for hull leak detection is required to listen for strikes and then for the hiss of air escaping, Others are pressure sensors in lots of places to detect changes. You need a display console that shows what is happening and where.

tahanson43206 · 2022-03-25 06:47:57

For SpaceNut re #8

SearchTerm:Component Sensor network

This component can be selected from a great profusion of offerings available on Earth today.

Please follow up by posting a list of at least three vendors who produce the kind of sensors (and if possible, a complete solution) you believe we need.

At this point, we know the area to be covered by the exterior ring pressure wall ... 238 x 19 meters (to be increased slightly in length)

Your chosen vendors should be able to offer equipment, wiring, computer software and human interface to cover the needs you've identified.

(th)

tahanson43206 · 2022-03-28 06:35:50

In the Zoom session of 2022/03/27, kbd512 provided support for the concept of building as much of each component (of Large Ship) as possible on Earth.

We already have a topic set up for exactly this procedure, so I'd like to take advantage of it for the hull panel component.

In the Zoom session of 2022/03/27 the decision was reached to set the width of the hull panel to be manufactured on Earth as 2 meters.

This means that 119 panels will be assembled on orbit to create the outer hull surface of the Habitat ring of 238 meters.

kbd512 ** also ** recommended that "former" and "stringer" elements be welded to the panels on Earth, so they can be bolted together on orbit.

While details are yet to be defined, I predict that the structure elements to be added will be steel, so they can be welded to the panels.

kbd512 is committed to bending the panels on Earth to match the required curvature in the lateral dimension. That curvature is 360 degrees / 119 panels, or 3 degrees over the 2 meter width.

Thus, the "former" segments must match the planned 3 degree curvature of the panels, while the stringers will not because they will run the full 19 meter length of the panels.

However, the stringers need to be longer than 19 meters, because they will join with the corresponding wall stringers.

We need visualization tools to prepare for procurement, manufacturing, shipment via Starship freight carriers, and assembly on orbit.

We have Blender and Fusion 360 available now, and we (taken as a group) have some modest experience with these tools.

We also have several members with demonstrated skill in use of 2 dimensional drawing tools.

The necessary key decisions having been made, I expect to see the pace of definition of components and assembly procedures picking up in coming days. There are thousands of components to define, procure, manufacture and assemble. That chain of events follows from the recent simple decision to fix the dimensions of the hull plates.

(th)

SpaceNut · 2022-03-28 19:23:45

I like the even meter width as it makes the pre-cut easier to handle with the welding jig to hold the panels until the weld is finished.

Remember that as you apply a layer inward to form the isogrid and then the inner hull the sheets will shrink in the 2m widths by the thickness of the sheets materials depth or thickness.

The should have welds that fall in between the welds of the other panels to keep the combination of layers stronger.

The angle for the panels will change ever so slightly but its the inner most closes to the hub that will change the most.

SpaceNut · 2022-09-25 09:38:40

This video reminded me of the construction techniques for large ship build

https://youtu.be/JmGb2r9XvOs

tahanson43206 · 2024-11-17 11:49:58

http://newmars.com/forums/viewtopic.php … 69#p227869

In the post at the link above, Void presented an idea/suggestion about using Starship's hull for construction in LEO.

I am picking up on the basic idea (as I understand it, which may be different from Void's idea), the engines would be returned to Earth, and the hull would be used to build large structures in space.

I have added the suggestion of welding girders to the outside of the hull to facilitate construction on orbit. The girders would be welded along the length of the Starship hull, so they do not cause drag during launch. There could be as few as two such girders, but having four would be advantageous to the engineering/architecture team that designs large structures, such as space stations or large vessels.

My invitation to our members who have the skills and software suitable for the job (such as Blender or Fusion 360 or many others) is to create drawings of what large structures might look like if they were bolted together using Starship hulls as the LEGO blocks.

The exterior ring of RobertDyck's single hull large ship might be made of a set of Starship hulls bolted together.

The twin hull counter rotating designs of kdb512 and GW Johnson could both be made using such hulls as components.

The intact tanks inside the vessels could be used for storage of liquids or gases as might be needed.

As a reminder for anyone designing for rotation in orbit, it is necessary to maintain balance discipline.

Any mass added or moved anywhere in a rotating structure MUST be matched by an equivalent mass in the location that is exactly opposite to the center of mass of the structure.

(th)

Last edited by tahanson43206 (2024-11-17 11:52:25)

GW Johnson · 2024-11-18 12:34:36

See what I just posted in meta new mars/GW Johnson postings, where the same question was asked, and I answered it there.

GW

Void · 2024-11-18 14:24:29

Dr. Johnson, I appreciate the measurement. I worked in metrology, and I like having best numbers even if they don't tell me the story I want to hear: https://newmars.com/forums/viewtopic.ph … 94#p227894 (See post #454)

But I should have been careful with my language. You have said that the glass is almost certainly not full enough. I am taking the notion of a glass partly filled and perhaps not ever to be filled, and then my question is what other assistance other than the Super Heavy would allow it to go to orbit?

So, at that point I am not talking about SSTO, rather Assisted-Sort-Of-SSTO. Ass.-SSTO, if you like.
-Possibilities are Tug/Skyhook to finish it to orbit.
-Catapult, which I have attempted in a sort of joking way to invent. Probably not enough.
-But we also could strap two Falcon 9 1st Stages to it in the manner of Falcon Heavy.
(Solids might also work, but I understand they shake a lot which would be bad, and they are hard to reuse)

I know that they had a terrible time making Falcon Heavy work, so yes, it is very questionable. But the thing about it is you would not be landing the Starship so you would not need a platform to land it with such as Mechazilla, and the two or more Falcon 9's could land on barges in the sea. Troublesome but not impossible.

So, for me that makes something possible, but good chances not economically viable. But who knows. If SpaceX were to build a Metha-Lox version of Falcon 9 with Raptors, then maybe. Not saying that they want to, but as I see it, the spaceports for Full Stack Starship launch will be likely to be congested.

(th), I also allowed for a shell Starship to be assisted to orbit by Super Heavy. In such a case it might be able to carry as much as 200 Tons, maybe more of propellants to orbit. I prefer the notion of Metals that could be either for structure or for propellants for a Magdrive, or Neumann Drive systems.

So, I feel that your inclusion of the idea to this topic is valid.

Ending Pending

Last edited by Void (2024-11-18 14:38:46)

tahanson43206 · 2024-11-18 15:29:19

For Void and GW Johnson!
Thank you both for significant contributions to this topic.

I would like to see this topic continue to develop, with a lean toward practical solutions.

Void, your creative thinking inspires others to stretch ** their ** thinking. In this case, while I may not have fully grasped your idea, my impression of your idea led me to imagine shipment of girders to LEO bolted (or welded) to the exterior of a ship such as Starship.

I am hoping that if we have someone in the membership with the time, the skills and the software available, this topic might become the home for a vision of a way to build really large structures in LEO.

The central cylinder of Starships could become a Lego-like component of a large structure.

The engines and nose of such a Starship could be bolted together and returned to Earth as a truncated mini-Starship.

I'm hoping this topic will become of interest to those (probably younger) who will actually be doing this work.

(th)

kbd512 · 2024-11-18 23:44:30

This is the basic shape for the large ship habitation ring:

32407-jpg

Whether this "habitation wheel" depicted above uses 3, 4, 5, 6, or even more spokes to support the forces acting upon it is less relevant than the fact that you have two of these habitation wheels rotating in opposite directions so that the forces exerted on the vehicle cancel each other out, and thus a gyroscopically stable vehicle design is achieved. A "stable vehicle" is one that does not precess perpendicular to the axis of rotation and travel, the way a rifle bullet does. This is very important for both trajectory computation and thrusting in the direction of intended travel. Not having to compensate for the vehicle's rotation in one plane causing it to slowly yaw in another plane, and thus "drift" off-course, is very important. If the axis of rotation and the direction of intended travel is in the X-plane, similarly to a rifle bullet, then the vehicle is affected by a yaw in the Y-plane. As it pertains to actual bullets, the slang term for this unwanted behavior is "spin drift". This is a very real phenomenon, and over great distances it has a very substantial effect on trajectory. If bullets had two parts with equal mass rotating in opposite directions, then this would not need to be accounted for in ballistics computations.

Over 193.75 million miles, spin drift would affect the vehicle's trajectory by about 64,583 statute miles. That is a very significant deviation, considering the fact that Mars has a diameter of 4,212 miles. You would "miss" the planet Mars entirely if you failed to account for a deviation of that magnitude. You obviously could compensate, but this seems like a needless complication since it's affecting the vehicle at all times while it's rotating, and will in fact affect where the "nose" is pointing, thus the direction of thrusting. Using counter-rotation to stabilize the trajectory of a vehicle providing artificial gravity for its crew means whatever direction you point the vehicle in, you need only account for gravitational fields from large bodies and the fundamentals of orbital mechanics when plotting intercepts to distant planets.

Edit:

The following link goes to a Physics Forums discussion where using counter-rotation to side-step this problem is being discussed. On that forum, just as we already did during one of our Zoom sessions, and I actually wrote some simplistic software to do, the people posting in the topic are telling the OP to make sure he / she accounts for Mass Moment of Inertia. I believe we did that to determine that magnitude of the force applied to the vehicle, but in the OP's application it matters to the accuracy of the gyro-stabilized flight control computer.

Counter-rotating mass to counteract inertial spin

Last edited by kbd512 (2024-11-18 23:57:39)

kbd512 · 2024-11-19 04:27:41

High-Manganese steel is an acceptable substitute for 316L stainless when the atmosphere of the interior of the ship, and thus the metal hull, will be kept relatively warm.

Weldable 316L austenitic stainless yields at 25ksi. Non-weldable 316 stainless yields at 30ksi.

Weldable austenitic Mangalloy yields between 50ksi to 75ksi.

At least doubling both yield strength and hardness over 316, as well as substantially increased abrasion resistance if objects ever impact the interior of the hull by accident, is very important. At room temperatures, Mangalloy steels will have ductility comparable to austenitic stainless steels, but at a minor fraction of the cost. 316 will have better ductility at deeply cryogenic temperatures, but I don't think a crewed vehicle with a cryogenically cold hull is compatible with human survival. Thermal conduction, in conjunction with a multi-layered insulation and ballistic protection overwrap applied to the hull's exterior, should ensure that no part of the hull is subjected to the greatest extremes of hot or cold.

This is a very lengthy but very expressive missive on all aspects of high-Managanese steel production and fabrication processes, with comparisons made with austenitic stainless steels as well as other kinds of steels and some insight as to why to choose one over the other:
Austenitic Manganese Steel

I would fabricate the hull from Mangalloy, with a keen eye towards the weldability of the alloy without cracking or stress concentration, then I would coat the entire hull, inside and out, with a plasma spray deposited ceramic coating to resist corrosion damage, and then I would apply a CNT fabric overwrap that provides both ballistic protection and acts as a "heat spreader" to maintain temperature uniformity over the entire hull. Very large rolls of CNT fabric "matting", similar to unidirectional Carbon Fiber tapes, are now available. On the interior, I would apply BNNT fabric to the hull, to absorb secondary radiation, act as a thermal blanket, and prevent an interior fire from weakening the steel or otherwise threatening the airtight integrity of the hull.

To keep weight reasonable, we're talking about using rather thin pieces of sheet steel, hence the use of a stronger base metal and the elaborate protection scheme afforded to the ship's crew and passengers.

Wiring for shipboard electrical systems would consist of CNT conductors with BNNT fabric insulators (not plastic). This will drastically reduce weight over shielded Copper conductors and plastic insulation, by about 80%, increase the resistance of the wiring strands to cutting or abrasion, provide extreme resistance to fire, and reduce the possibility of a fire generating toxic smoke in the cabin air supply. The electrical connectors will use BNNT-reinforced sintered ceramics for fire resistance and weight reduction. Here again, the elaborate protection scheme is centered around preventing fires, fire resistance, and general durability. The reduction in interior metal content is also driven by a desire to limit secondary radiation emission associated with high energy particles (galactic cosmic rays) striking the hull.

I think the most economic way to produce the ship's hull will be using a series of precision castings that have been ground to final size. The reason for this has to do with achieving near-perfect balance of all parts of the rotating assemblies.

Whereas modern gas turbine blades are hollow to circulate cooling air through the internal channels depicted above, we require an active stabilization system that keeps the rotating components balanced as weight shifts around inside the ship. Apart from preventing unwanted changes to the ship's trajectory, the primary reason for doing this is preventing uneven wear on bearings or distribution of force on highly loaded thin-walled components.

This vessel is an aerospace vehicle, not an ocean-going ship in the conventional sense. Weight matters quite a lot, as does the quality of the materials used and workmanship. We need to be very deliberate about how we go about approaching its design, not fixating on any single aspect of the vehicle to the detriment of all others, and we must remain pragmatic about what the vehicle is optimized to do.

After reviewing state-of-the-art PEMFC and ion engine technology, with PEMFCs fast approaching 40kW/kg, I no longer think we need nuclear propulsion. This moves the large ship concept solidly into the realm of feasibility, because there are now water propellant ion engines generating sufficient thrust and Isp. We still need about 500MWe, meaning a 12,500kg fuel cell, but we're going to use a novel application of the steam being generated by the fuel cell. We're going to push the fuel byproduct (steam) required to power the fuel cell, through the ion engines. To my knowledge, this has never been done before, but we're going to do it, because we need to repurpose that which powers the fuel cell to also supply reaction mass to the ion engines.

We may still require nuclear power to provide sufficient life support electrical power for 500 colonists, but that which powers the propulsion energy generating system and the propellant itself can now be the same materials. Rather than using cryogens, we now have high pressure CFRP storage tanks that can store sufficient Oxygen and Hydrogen. From my reading of the literature on Mangalloy steel, special formulations of that material do not appear to suffer from Hydrogen permeation and embrittlement to nearly the same degree as other metals such as stainless steel, which means we can use steel liners for the Hydrogen storage tanks. Oxygen presents a real challenge for Mangalloy, which means the CFRP Oxygen tanks will require stainless liners or Mangalloy with an appropriate coating. We may still use cryogens and light metal tanks for achieving escape velocity from Earth, but the return trip will rely upon a lesser volume of highly compressed gas.

The greater use we make of non-nuclear COTS technology, the greater our chances of convincing an organization such as SpaceX to build purpose-built interplanetary transport ships and landers, keeping those valuable Starships here at Earth, for economic delivery of payloads to LEO. We may be able to achieve better results using nuclear technologies, but the licensing and economic hurdles to implementation are extreme. We will certainly need fission surface power systems for colonization, so perhaps that's where political and monetary capital should be expended to bring this dream to fruition.

tahanson43206 · 2024-11-19 07:47:34

For kbd512 ... first, thanks for #17 and #18.

I have a question that flows from this sentence:

I think the most economic way to produce the ship's hull will be using a series of precision castings that have been ground to final size. The reason for this has to do with achieving near-perfect balance of all parts of the rotating assemblies.

Can you (would you) be able/willing to show what shape the castings might take?

In following up on Void's idea about using Starship hulls to make large structures in LEO, I proposed welding girders to the exterior of the Starships to be incorporated into a large structrure. These would facilitate bolting the Starship cylinders together on orbit.

I am interested in the possibility of separating the nose and engine compartment from the delivered package, joining the nose and tail together, and returning them to Earth.

Could the components you are thinking about be delivered to LEO on the outside of Starships? If they can, then the Starships can be re-used without having to change the existing configuration. How large would the components you are thinking about be?

(th)

tahanson43206 · 2024-11-19 07:53:59

At present (to the best of my knowledge) all (except one category) items intended for delivery to orbit around Earth are boosted while mounted on top of the final stage of a multi-stage rocket, and while enclosed in a shroud that is discarded. The ** one ** exception was the Space Shuttle, which delivered objects to LEO and then released them from the payload bay after opening the payload bay doors.

It appears that SpaceX may be considering a design that allows the nose of the Starship to open to allow release of payload, and to close afterward. That will be an impressive bit of engineering if it happens.

(th)

kbd512 · 2024-11-19 10:32:53

tahanson43206,

If you're thinking that certain parts of a Starship can be treated like "Legos", then I would say that's probably not going to happen. Starship is the upper stage of a launch vehicle, so that's what it was optimized to be. Skylab was an extensively modified upper stage that was built on the ground in a fab facility. Redesign of the existing hull structure is likely required to ensure it's structurally sound for the intended use as an orbital habitation module providing artificial gravity over long periods of time.

What parts of a Starship crew compartment will require structural reinforcement as part of a new artificial gravity orbital habitation module design?

Those changes could be relatively minor, yet will likely be significant, in much the same way that strapping two boosters to the side of a Falcon 9 first stage amounted to a complete redesign of the core stage, such that it shared virtually nothing in common, structurally speaking, with an actual Falcon 9 booster stage. The forces exerted won't be nearly as extreme as a pair of strap-on booster stages, but the load path and reinforcement wlll change from how Starship was previously designed. If doing that proves relatively simple and easy, then it's a happy accident.

Why not just start from scratch with a vehicle design optimized for the intended use case?

Starship uses very weak and therefore heavy (for the strength provided) stainless steel. I'm talking about working with a material that's 2X to 3X stronger, because this vehicle will be at least as heavy as a fully fueled Starship while providing far more pressurized volume to make it both comfortable and well-protected for long duration missions.

Assume for a moment that since you no longer have any support structure beneath that pressurized compartment, that you'll require significant alterations. If you're doing that on the ground, then that portion of the vehicle is flying to orbit in that configuration. We've changed the outer mold line of a hypersonic vehicle, and then we're going to detach it from the propellant tanks on-orbit unless we're doing the "spinning baton" design with a complete Starship. If we don't detach the propellant tanks and engines, then we're hauling around 100t of dead mass which must be resisted by the structure connecting the pair of Starships.

Could that be done relatively easily on-orbit?

I honestly don't know, but I suspect we're looking at a significant vehicle redesign of Starship.

If we're going to go to that trouble to repurpose a portion of the existing flight vehicle design, then why not design a new vehicle from scratch to get all of the features we really want?

kbd512 · 2024-11-19 10:49:37

tahanson43206,

My final thoughts on Void's proposal is that if the required changes prove to be relatively minor, then it could be a faster / cheaper pathway towards initial human Mars exploration missions. By its very nature, it will never be a like-kind substitute for a purpose-built highly compartmentalized ship intended for transporting hundreds of colonists vs a dozen astronauts.

I would place Void's proposal in its own AG-enabled Large Ship Prototype category. It could be used to prove the feasibility of AG and counter-rotation, evaluate the effectiveness of the various protection schemes afforded to a large interplanetary transport ship, and function as a testbed for the life support / power / propulsion systems, as well as the first operational use of an interplanetary transport ship worthy of that title.

kbd512 · Yesterday 12:37:17

For the 500 colonist ship, I'm allocating the following masses:

350t - ship's hull
50t - ship's complement
155t - food for 180 days
100t - water reserves
45t - furnishings, clothing, toiletries, and misc consumables

Mangalloy is 7,800kg/m^3, which only provides 44.872m^3 of hull material to work with
Sylramic fiber C/SiC Ceramic Matrix Composite is 3,210kg/m^3, providing 109.034m^3 of hull material

Both materials provide comparable tensile strengths in finished form. CMCs are stiffer than steel, so less deformation under load. The CMC would not lose much strength in the event of a fire aboard ship, as Sylramic fiber was intended to out-perform Nickel-based superalloys. The proposed Mangalloy cannot operate above 260C without losing its ductility over time.

Using CMCs for primary structure would necessitate sealants between the individual "donuts" / "wedges" comprising the toroidal habitation ring structures. This implies use of air-tight gaskets between sections, so perhaps thin stainless steel gas-tight crush seals can be fabricated since these work pretty well in high pressure applications, such as air conditioning systems. Multiple sections would be bolted together and uniformly "crush down" on the sealing gaskets. Silicone seals could also be used, which are standard for US Navy ships, but nowhere near as heat resistant as multi-layer metal gaskets. CMCs may not benefit as much as metals do from ceramic thermal barrier coatings to protect the material from corrosion damage or weakening due to fire, and thermal expansion is markedly lower than it is for metals, but C/SiC's thermal transfer coefficient is or can be at least 2X higher than Mangalloy, so additional thermal insulation is required. The cost issue at play is that for near-zero porosity, as achieved by CMC components like gas turbine blades or hot section casings, some kind of vapor infiltration processing method is required to fully densify the ceramic matrix around the fiber reinforcement, and that process is expensive.

The net benefits of CMCs of the variety considered here are equal strength to austenitic steels (on par or stronger than Mangalloy and meaningfully stronger than stainless), comparable or greater stiffness, much lower CTE, much greater temperature tolerance range from deeply cryogenic to 1,200C, thermal shock resistance, much greater achievable section thicknesses for a given weight, and the potential to either reduce weight or add strength to critical areas. There would be no on-orbit fixturing and welding of the hull structure, merely bolting it together. That would greatly reduce the complexity and cost associated with assembly. We have extensive experience with on-orbit assembly, but very little with on-orbit fabrication. There would be no post-fabrication grinding / machining of the CMCs, either, because they're created using high precision molds. Metal expands and contracts quite a bit after sintering or casting, which implies cleanup machining of some very large individual parts, though not terribly heavy.

There would be a modest radiation dose reduction over steels, but ceramics are still oxidized or nitrided metals at the end of the day, albeit thicker and combined with Oxygen or Nitrogen which promotes more elastic collisions to help absorb ionizing radiation, very strong microwave radiation absorption, decent X-ray radiation absorption. It won't do much of anything against gamma rays or heavy relativistic ions, but neither will thinner sections of steel, which will promote showering of the crew with secondaries. The interior and exterior BNNT fabric overwraps will do a much better job against secondary radiation, but are still basically sheets of typing paper being pitted against armor piercing bullets. Only a large volume of water or other Hydrogen-rich materials have much chance against GCRs. For a 6 month trip, apart from shielding against solar flares and CMEs, I think the rest of the radiation dose has to be "taken on the chin" until active systems are devised to protect ships.

300t of reserve mass will be allocated to:
ship's amenities such as the cafeteria, food cooking and storage, toilets, showers, etc
interior airtight bulkheads and hatches
interior thermal protection fabrics
exterior hull ballistic and thermal protection fabrics
sCO2 gas turbine RTG electrical power supplies
LCO2 storage for RTGs and shipboard firefighting
thin film photovoltaics for supplemental electrical power
radiator arrays for thermal regulation
electrical wiring and air ducts for interior air circulation
docking hatches, fittings and electric motors for counter-rotation
PEMFC main propulsion system power supply
H2O propellant ion engines
compressed H2 / O2 storage tanks to power the main propulsion fuel cell
supplemental water propellant storage tanks

Total dry mass target, less propellant, is 1,000t.
Total wet mass target is 1,500t to 1,700t.

tahanson43206 · Yesterday 13:29:26

For kbd512 re #23

This post is offered to try to encourage you to keep developing your thoughts on materials.

At the same time, ** this ** topic is focused upon manufacture of components, and with Void's idea in the wings, I am hoping the topic will include delivery of the components to LEO.

The essence of Void's idea (as I interpret it) is to deliver needed components on the exterior of Starships (or equivalent vessels).

I proposed welding girders to the exterior, which would provide significant length capability. Any components that would be shipped in the nose of a vessel would be constrained by the dimensions of the interior of the vessel.

If you can design components for your vessel that would be assembled on orbit, AND design them so they can be delivered as external cargo, then the delivery vessel can be simpler to build and to operate.

(th)

Void · Yesterday 16:20:30

(th) my intention is to project a simplified Starship to orbit and repurpose it to whatever it might work for. This could be structures or to use the Metal as propellants.

Ending Pending

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#1 2022-03-19 12:47:49

Large Ship Component Manufacture on Earth

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