Large Ship Assembly and Checkout on Orbit

tahanson43206 · 2022-03-19 12:50:52

Large Ship Prime is: Large scale colonization ship by RobertDyck

This topic is offered as a way to consolidate posts about assembly and testing of components for Large Ship to be done in LEO.

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)

kbd512 · 2022-03-19 19:01:44

tahanson43206,

A tool for precisely fixturing / jigging the hull sections is required for EBW or laser welding.

Strong Points for EBW:
1. Highest quality welds, almost exactly equal to the base metal in most cases, which is good for eliminating stress
2. Smallest heat-affected zone, lowest distortion possible except for in-space vacuum-welding of metals
3. Very deep penetration possible, even at relatively lower power output
4. Machining by vaporizing metal possible, so it could feasibly double as a CNC mill for parts not properly cut
5. Joining of dissimilar metals possible, such as Aluminum and steel or Copper and steel

Weak Points for EBW:
1. Requires a hard vacuum
2. No idea how atomic Oxygen will affect the weld quality, but any Oxygen probably won't help (this will be blasted free of the weld if using lasers)
3. Requires exceptionally precise fixturing, which may accidentally "vacuum-weld" the parts together before they're ready to be joined
4. Produces strong X-rays, directly proportional to beam power, which means personnel would need to be well shielded or well away from the work piece during welding operations, and this would also mess with cameras and electronics attempting to remotely view the process (one of the reasons why it requires special facilities beyond a simple vacuum chamber)
5. EBW machines can be somewhat temperamental / maintenance-intensive

Strong points for laser welding:
1. Very high quality welds, sometimes resulting in greater strength than the base metal (the weld will never "fail before the base metal", but this may not be what you want because it means the temper is different), ductile failure modes for most steels (welds are not brittle)
2. Heat-affected zone almost as small as EBW (for pieces as thin as we're talking about, no real difference)
3. High welding speeds possible with sufficient power
4. Cutting and abrading of metal is possible, if mistakes were made before or during welding (this is a very useful feature to have)
5. Can be done within an atmosphere, if a shielding gas like Argon is supplied (another useful feature to have)

Weak Points for laser welding:
1. Produces metal plasma during welding, which is ejected from the keyhole produced by the laser, and would become another source of on-orbit debris, however benign compared to much larger chunks of material (like having sand in orbit), but more importantly, a source of contamination for surrounding materials (most but not all of this could be "caught" using an appropriate cover during welding)
2. Produces more distortion and changes to the microstructure of the steel as compared to EBW (just because it can be stronger than the base metal doesn't mean that this is what you actually want, and in an ideal world the weld would be exactly equal in YS / UTS to the base metal and has the same failure mode, as if both the weld seam and the joined pieces are one continuous piece of metal)
3. Welding thick pieces or dissimilar pieces is more problematic, because the laser will be reflected off of the weld pool and unevenly heat a thicker and thinner piece (this is less problematic with thinner work pieces, but ever-present)
4. Generally requires more power than EBW for equivalent penetration (the differences would be relatively minor for thinner work pieces)
5. Processes for welding are not nearly as standardized as EBW, which means the people doing the welding need to know exactly what they're doing and how to appropriately adjust beam size / distance, power output, whether to use pulses or a continuous firing, and all of this stuff will also vary by the type of laser being used (CO2, Nd-YAG, fiber channel, etc)

Given the fact that the hull of this ship is so thin and a high quality electron beam weld requires exceptionally precise fixturing / jigging of the hull sections to be joined, it may turn out that a laser welder is more versatile since welding could be done from both sides, as well as in a pressurized compartment, if required. While I think EBW would produce the highest quality welds, it would require keeping the area clear of personnel. There's near-zero atmosphere in LEO, so X-rays can go quite a distance and penetrate deeply.

Penetration Depth in Laser Beam Welding - An analysis resulted in two expressions for depth of penetration, both of which can be used to determine laser beam welding parameters for any steel

From that rather ancient 1993 test on HY130 steel that the Navy uses, we can see that a 12.25kW CO2 laser could penetrate 10mm while welding at a speed of 21mm per second / 50" per minute. If you want to penetrate deeper, then you need more power. If you want to weld faster, then you need more power. If this stuff is as thin as Robert says it will be, then a 5kW fiber channel laser is probably sufficient. That said, EBW certainly would get the job done as well as or better than lasers if you're willing to accept the X-ray shielding requirements.

Acceleron Inc - Specialists in Electron Beam and Laser Welding Technology

About Acceleron
Acceleron, Inc. has been a major provider of precision-welded parts and component assemblies since 1974, and currently operates the largest privately-owned electron beam and laser production facility in North America. As a manufacturer specializing in electron beam and laser technology, Acceleron currently meets the needs of customers worldwide whose products vary in size and category. We are continually expanding to meet the growing needs of the industries we serve. Other services include sheet metal rolling, plasma cutting and CNC milling, CNC turning and CNC grinding in our state-of-the-art production machine shop.
We are now offering educational seminars – at our facility or yours – to give engineers and technicians a better understanding of our various technologies and how they work. Our goal is to assist you in determining the most cost-effective, efficient method for processing your parts.

These people probably know enough about both to tell us when to use and when not to use either technique.

Anyway, I would count on at least one full work day for the fixturing and welding operation per major joint, possibly two days.

tahanson43206 · 2022-03-19 20:07:18

For kbd512 re #2

Thank you for providing such a significant boost to this new topic!

***
For SpaceNut ... kbd512 is showing up a direction to look for new members who might wish to participate in bringing the fantasy of RobertDyck into the Real Universe!

***
For kbd512 ... please do not take this as a criticism ... it is not so intended .... I am running into the same situation with GW Johnson ... The mindset of planning to use humans for assembly or operation of equipment in space is of long standing .... I am (hopefully gently) trying to help us all to move toward teleoperation as the preferred mode of operation for assembly of Large Ship (whichever version gets funding first).

My expectation is that when humans are needed (and they most certainly ** will ** be needed), they will be deployed to clean up the mess that machines have made, or to replace ones that have gotten themselves into a pickle they can't get out of.

(th)

kbd512 · 2022-03-19 20:57:17

tahanson43206,

The purpose of construction is not to satisfy anyone's complexity cravings. We serviced Hubble using humans, despite the fact that they were only unscrewing things and plugging in new equipment modules.

A human will not directly weld on the hull of the ship. That part of the operation will be done with a welding robot because only a robot is capable of the precision required. However, a human will be required to command that robot, to confirm that all fixturing of the work pieces is as perfect as he or she can make it, and to connect / disconnect power cables to a hand-transportable generator to power the welding robot. This task may and probably will only involve a crew of six people, working in pairs 24/7/365, and using lots of prefabricated parts that require complex assembly.

All of the construction robots used here on Earth are commanded by human operators. Even the robots that simply pick up and move computers around in Dell's computer factory require constant human oversight. We don't have the level of automation required to remotely operate robots the way you envision. Maybe one day we will, but that is a long, long ways off. Rovers creeping along on the surface of Mars at mere inches per minute is one thing, performing a wide variety of construction tasks is another thing entirely. Each one of those semi-autonomous rovers cost the tax payers a billion dollars a pop. We're willing to front that kind of money to do true exploration some place that humans simply cannot go using available technology, but not for construction tasks.

The instant a human is required to fix a problem, all that money spent on teleoperated robots may as well have been flushed down the toilet.

tahanson43206 · 2022-03-20 06:18:53

For kbd512 re #4

The funder will decide how construction will be done.

The contributions of members of this forum to this topic will (hopefully) provide guidance.

Personal preferences of individuals will be considered, and the best solution selected.

Thus, a preference for humans on orbit will be blended into a preference for remote construction tools, and the optimum solution selected for each case.

The advantage of assembly of major components on Earth is the convenience for human participation in the process.

(th)

SpaceNut · 2022-03-20 11:55:29

second time with this post...

The space industry has changed from the initial circa 1960 to current and that is a time span of that only happened after seed money was used to foster a commercial industry and deep pockets to make it happen by 2015.

If we are waiting for industry we will not be going before the end of the century by that model as its that investment dollars that need to come from deep pockets to make it happen.

The old guard and Nasa are not heading in our direction of providing for a product that moves people in large quantity safely and the same holds true for the current space commercial industry.

Now back to construction are we building from the central hub outward and if so what is that first set of corridors going to be leveraged from?

What is the transport of the massive tonnage provider going to be?

tahanson43206 · 2022-03-20 14:27:02

For SpaceNut re #6

This topic is NOT about how items to be assembled get to orbit.

It is assumed (for the purpose of this topic) that the items are in orbit.

However, as you (in particular) think about how a project of this magnitude will be organized, please consider if you want a topic devoted to delivery of subassemblies from Earth to LEO.

I don't see that specific conern as deserving it's own topic, but if you think one is needed, it may prove helpful.

My hope is that ** this ** topic will invite proposals for subassemblies that can be lifted to LEO with existing or highly likely launch systems.

The ball park tonnage appears to be on the order of 100 metric tons, and dimensions are hinted at in Starship specifications, but those are in a state of flux.

Firm dimensions are available for Falcon 9 and Falcon Heavy.

That said, thanks for helping to keep the ball rolling for this new topic.

(th)

SpaceNut · 2022-03-20 15:47:30

The panels delivered to space each are numbered for location of use and for its general shape inside, sandwich (iso grid), or outer of which the materials are stainless steel, aluminum, and possibly more of either. These are all non magnetic for a stable attachment to them for robotic or telerobotic to use which means you need a special device to hold the panels while the welds and some assembly is done. It then must release and advance to the next panel repeating until ring, tunnels and decks are in place leaving the hub and glass to be delivered and installed.

tahanson43206 · 2022-03-28 06:45:08

For SpaceNut re #8

Your recommendation for precision manufacture for flawless assembly on orbit is welcome.

Numbering of each component will depend upon the situation, but since it has been decided (Zoom session of 2022/03/27) to go with hull panels of 2 meters width, we have a firm number of panels, so your numbering recommendation would suggest the panels be numbered 1-119, with a corresponding Compass heading of 3.025 degrees per panel. We need a reference for zero, and I would suggest the Earth Center line as worth considering for orientation.

The structure to be assembled will be in orbit, and the center of the Earth is a reasonable point for orientation, while the East-West line would seem appropriate for the alignment of the assembly for center-true.

For those who are picking up this line of discussion for the first time, the Large Ship (Prime) is intended to rotate at 3 RPM as a Unitary Body. This means that every gram must be matched with a corresponding gram on the opposite side of the center line (a) and (b) on the opposite side of the center of mass.

This structure would be the largest precision rotating machine ever assembled by humans, if the Rotating Space Station proponents do not achieve their objectives first.

(th)

SpaceNut · 2022-03-28 19:17:37

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 inner curve facing the central hub is if you use 2 decks that are 3 m each will have a sharper degree of arc due to the reduced radius for the 2 m width of which we should look for another change to sheet design to make the count equal. Also these are the one's with the glass interface as well so these are shorter than the 19 m length.

I would also pre-cut the inner deck floor pie shape as well to be able to weld it into the outer wall as we build so that when we apply the inside wall that we have it attached to close the ring surfaces. Add the internal section pressure dividers and we are getting a near finished shell.

tahanson43206 · 2022-03-29 11:51:50

For SpaceNut ... thank you for your forward looking insights in Post #10!

This post is offered to focus upon a detail of assembly of the hull panels on orbit. In next week's Zoom, I'm hoping we can finish scoping out the "formers" and "stringers" to be welded onto the flat-then-curved panels of the space facing hull sections.

In the process of designing those components, I'd like to suggest we consider making the pieces so they "snap" together on orbit. What I have in mind is assembling all 119 segments loosely (using mechanical snaps) so that the entire assembly of 119 panels can be jiggled so as to insure it is a perfect ring. I'm talking about "perfect" as to the nearest millimeter.

Only AFTER the perfect ring is achieved, would remotely operated welders go to work on the panels.

At the same time, the snap fittings of the formers and stringers would be welded.

Flexing of metal due to thermal stress is a concern.

How the process is handled is (to me for sure) unclear, but I would ** think ** that the assembly/welding process might best be carried out in the shade.

It might turn out to be a good idea to have the thermal protection devices (whatever they turn out to be) ready to mount on the exterior of the Hull, so that when the work shade is removed, the hull can handle the Sun's vigorous warmth.

It might turn out that having the side formers and stringers ready for assembly immediately after the space facing hull is finished would be a good idea, because heat fluctuations might distort the ring before those side pieces are installed.

Perhaps everything should be done in a shaded area.

That "shaded area" might be under a region of solar panels, which are going to be needed to provide power for the multiple assembly operations.

(th)

SpaceNut · 2022-03-29 17:30:37

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.

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

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#1 2022-03-19 12:50:52

Large Ship Assembly and Checkout on Orbit

#2 2022-03-19 19:01:44

Re: Large Ship Assembly and Checkout on Orbit

#3 2022-03-19 20:07:18

Re: Large Ship Assembly and Checkout on Orbit

#4 2022-03-19 20:57:17

Re: Large Ship Assembly and Checkout on Orbit

#5 2022-03-20 06:18:53

Re: Large Ship Assembly and Checkout on Orbit

#6 2022-03-20 11:55:29

Re: Large Ship Assembly and Checkout on Orbit

#7 2022-03-20 14:27:02

Re: Large Ship Assembly and Checkout on Orbit

#8 2022-03-20 15:47:30

Re: Large Ship Assembly and Checkout on Orbit

#9 2022-03-28 06:45:08

Re: Large Ship Assembly and Checkout on Orbit

#10 2022-03-28 19:17:37

Re: Large Ship Assembly and Checkout on Orbit

#11 2022-03-29 11:51:50

Re: Large Ship Assembly and Checkout on Orbit

#12 2022-03-29 17:30:37

Re: Large Ship Assembly and Checkout on Orbit

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