New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: This forum is accepting new registrations by emailing newmarsmember * gmail.com become a registered member. Read the Recruiting expertise for NewMars Forum topic in Meta New Mars for other information for this process.

#26 2022-03-26 19:59:03

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,310

Re: Large Ship (Prime) Bill of Material / Mass Allocation

tahanson43206 wrote:

For SpaceNut re new BOM topic ....

This topic is not developing as I had hoped....

There should be NO discussion in the topic.

All discussion should be happening in other topics.

The BOM topic is intended to be the final result posting site.

There should be NO further discussion of hull plate panels, except to finalize the remaining details for a specification.

Hopefully we'll wrap that up at the next Zoom meeting.

If we were designing a ship for use on Earth on water, we might start with the keel, if the ship is large enough to have one.

Smaller craft (apparently) do not have keels, but instead are defined by hull shapes.

In the case of Large Ship, there is no keel to lay.

The equivalent of the keel is where I have decided to start fabrication.  The Habitat Ring is the distinctive feature of the ship. The hull plating decision frees the design committee to proceed to the next critical component set, which is the set of "formers" and "stringers" to which the hull plates are to be welded.

Everything in Large Ship will flow naturally and (hopefully) effortlessly from this foundation element.

There should be no need for concern about unknown  unknowns.

Everything in Large Ship ** should ** flow naturally and easily from the hull plate decision, just as everything in a "real" ship flows naturally and easily from a keel. 

(th)

Offline

#27 2022-03-28 07:03:28

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship (Prime) Bill of Material / Mass Allocation

Per the Zoom meeting of 2022/03/27, the width of the hull plate is defined as 2 meters.

This value is subject to confirmation that the panel will fit inside the Starship freight carrier.

Per recommendation of kbd512, a 3 degree curvature of the panel (in the lateral direction) is to be applied on Earth, as the panel is welded to "former" and "stringer" elements which will be defined (hopefully) next week.

Per recommendation of SpaceNut, the panels will be numbered 1-119 with corresponding points-of-the-compass markings of 3.025 degrees per panel.

The material for the panels is in selection by kbd512, and it will be posted shortly.

As soon as the material is known, it will be possible to secure mass estimates and other useful characteristics for assembly.

(th)

Offline

#28 2022-03-28 19:27:03

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,310

Re: Large Ship (Prime) Bill of Material / Mass Allocation

This still uses the iso-grid panels which can be stamped cut so that we weld them at the half mark of the outer units. These would only be slightly smaller as the width of the material will be removed from one side to make it fit properly.

Offline

#29 2022-03-30 06:30:20

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship (Prime) Bill of Material / Mass Allocation

New detail has just arrived for the 119 pressure Hull plate assemblies...

Per kbd512:

After all that has been done and any distortions mechanically removed (bent back into the desired shape), the annealed steel needs to be aged in a furnace to achieve full strength and hardness.  All C300 martensitic alloys are heated between 480°C to 510°C for 3 to 6 hours and then air cooled.  We'll be a lot closer to 3 hours than 6 hours since our sheet metal is so thin, and probably less than that.  2 hours is probably overkill, given how thin these pieces will be.
I selected the C300 alloy for the combination of its mechanical properties, which include yield, compressive yield strength, hardness, notch strength, fatigue endurance limit, excellent weldability, and good corrosion resistance.
I have selected an ion-bonded Silicon Dioxide coating to protect the base metal from atomic Oxygen, due to its proven performance as a protective coating against atomic Oxygen in LEO, abrasion resistance, excellent resistance to most dilute acids (excluding hydrofluoric acid- we really shouldn't have anything that nasty on the ship), and resistance to corrosion chloride salts dissolved in the water tanks.  SiO2 does not stand up well to strong bases like Sodium Hydroxide, so any interior space where strongly basic chemicals will be used, a different or additional coating is required.  For example, if strong bases or acids are used to adjust the pH of the water in the water tanks, then a PTFE overcoat will be necessary.

Material recommended for panels: C300 martensitic alloy
Material recommended for coating:  ion-bonded Silicon Dioxide coating

I note that this set of 119 panels may be suitable for manufacture by an existing job shop.

We are waiting for details of formers and stringers to be welded to the panels on Earth.

As a reminder, the panels are intended to be lifted to orbit in a Starship freight carrier, so physical dimensions as well as mass will determine how many can be shipped at one time.  It would be ideal to ship all 119 panels in a single shipment, and if the panels were flat without formers or stringers that would be possible, if the mass is under 100 tons, which seems (to me at this point) highly likely. 

I am imagining the formers and stringers will be made of perforated metal that can be welded to the flat panels, to provide the optimum strength vs mass combination.

I am looking for the formers and stringers to be firmed up coming out of the next Zoom meeting.

(th)

Offline

#30 2022-03-30 08:47:47

kbd512
Administrator
Registered: 2015-01-02
Posts: 7,607

Re: Large Ship (Prime) Bill of Material / Mass Allocation

If we put the stiffening ribs inside the hull, then they could be used to keep the foam matting / impact cushion or spreader / insulation that you walk on in place, so maybe it won't be such a trip hazard problem after all.

Here's a thought to reduce the jigging / tooling cost.  Use a forming die to produce sheet metal with bent corners (10mm to 15mm rib stick up from the "floor" or "wall"), same concept as bending the Aluminum over a forming die to make ribs for a wing.  Spot weld that metal into place on a jig, next run a laser welder over the internal seam. and finally run the localized vacuum EBW machine over the smooth exterior because now the EBW machine can easily pull a vacuum on the smoother surface to give us a near-perfect exterior weld.  This could be done fairly rapidly, like making a car chassis.  It would do away with the expensive Invar / Kovar forming dies, because we could bend the metal into the precise shape after it's been spot welded together.  We could also make up for precise dimensional tolerance issues this way by making some panels slightly shorter or longer.  The foam flooring panels will be cut-to-fit, so slight imperfections are not a big deal.  Maybe we should forget about sub-millimeter precision fitment and just make it fast and easy to weld or repair instead.

So long as it's as strong as it needs to be and cheap to make, does it matter how pretty it is?

This thing could either be very cheap or very expensive to make, but it won't make it function any better or worse as a giant tin can.

Offline

#31 2022-03-30 10:39:50

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 18,142

Re: Large Ship (Prime) Bill of Material / Mass Allocation

For kbd512 re #30

First, thank you for continuing to contribute to the Bill of Material topic.

However, as often happens, a line of thought leads to a related line of thought that would fit well in another topic.

That has happened here.  it seems to me that your paragraph about manufacture on Earth (and some assembly in orbit) would fit well (?better) in the topic set up for that discussion.

Regarding where to put the ribs/formers/stringers ...

This seems to be a difficult issue to settle ...

I ** thought ** we had all agreed to accept the guidance of GW Johnson to keep the interior surface of the hull free of obstructions.

Placing ribs ** inside ** the hull would introduce obstructions.

I have not yet won the battle to keep the pressure hull far away from the passengers, crew, footlockers, storage racks and assorted other miscellaneous equipment that keeps showing up on the interior surface of the pressure hull.

I have asked SpaceNut to calculate the mass of the atmosphere of the Habitat.  I am hoping the amount of mass required to support an atmosphere is minuscule, compared to the mass of the ship as a whole.

This topic is waiting for resolution of issues relating to the hull panels.

Suitable inputs to ** this ** topic would be specification of the material and form needed for the stiffeners (ribs/formers/stringers).

Location of the welds can go into the manufacturing topic., with input from the Safety Department.

(th)

Offline

#32 2022-03-30 16:55:28

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 29,310

Re: Large Ship (Prime) Bill of Material / Mass Allocation

repost for inside the hull
form needed for the stiffeners (ribs/formers/stringers).

I believe you are thinking about a warehouse pallet shelving system to be used inside of the hull and I think that it would start the shape so that we get the support that we are looking for internally.

Of course rather than rectangular we would be making them into 119 pie shapes.

Industrial-Shelving-Phoenix.jpg

The cross supports would go against the hull and be welded to it with the end doing the same.

We will need to attach one to the center line of the panel with an attachment end for the other 3 connections for top and bottom of the panels. The orange rail is half of a T shaped that has a ledge to seat a panel against so modify the basic shape to have a ledge on both sides. The green upright also can be altered to make a lock tab system possible. Of course once put together weld the final joint so it can become solid.
The panel that rests on the shelf would be the floor or wall that could be removal able.

Offline

Board footer

Powered by FluxBB