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Engineer said:

Not really. All you said is that smaller volume offers smaller cross-sectional area for collision. By that same argument, don't build manned spacecraft or just don't build a spacecraft at all — zero chance of decompression! Nothing in that argument says modular architecture is superior to a monolithic one.

Given identical internal volume as requirement, modules have to be clustered together to minimize the exposed area to open space, and the end result is just similar to a monolithic structure. There is no advantage there. Splitting them up is actually disadvantageous because of increased surface area without any added internal volume.

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FairAndUnbiased said:

none of this changes the fact that an open, modular structure is less likely to experience decompression events due to debris collision than a totally pressurized structure. This is common sense - an open, modular structure has lower collision cross section. The sole increase in cost will be an elevator mechanism. But that's still cheaper than a totally pressurized section.

With assembly in orbit, many components that are not immediately life critical can be placed in a non-pressurized section and connected to the main section with vacuum tight feedthroughs, saving space.

Anything you can do to a totally pressurized structure, you can do to a modular structure for less money.

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Engineer said:

Assembly and maintenance in the vacuum of space is actually very expensive, not to mention hazardous. It's better to put as many components into pressurized section if possible, accessible to the astronauts without having to put on bulky EVA suits. No need to spend 7 hours doing a task out in space when it could be finish inside the spacecraft within half an hour.

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FairAndUnbiased said:

interesting part to note about collisions: the bigger the spacecraft, the more efficient it is against collisions, not less.

this is an interesting thought experiment:

The ISS has pressurized sections equal to roughly a 109 length x 4.2 m diameter cylinder going by total length and diameter of the Destiny module. The volume would then be 1510 m3 (bigger than reality of 910 m3, since not all modules are that size). It has 109x4.2 = 458 m2 collision cross section. For a maximal comparison, we take t

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The volume of Nauka is 180 m3.

For a hypothetical km scale Chinese spacecraft, let's say that for it to qualify as km scale, it has to have at least 501 m length. Let's have it be assembled using modules launched by the

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Using equivalent form factor (3 meters lower than maximum rocket diameter) we have a 6.5 m diameter x 24 m length module with volume 800 m3 each or almost as big as the entire ISS volume.

Let's assume 25 launches: 10 pressurized modules, 15 for nonpressurized components (solar panels, backup power, radiators, instruments, maybe a laser CIWS... for debris only, of course). 10 modules would be 8000 m3 volume and can be used for living space, space farming, etc. End to end, the pressurized modules would be 240 m in length.

Let's estimate power consumption.

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in direct sun with panel sizes 35x12 m. There are 8 panels for a total area of 2400 m2. Power generation is 0.07 kW / m2, power density is 0.16 kW/m3. Let's assume that due to efficiency increases in the next 20 years, the power generation increases to 0.1 kW / m2, power density required is 0.1 kW/m3. Then the requirements will be 800 kW for 10 modules, which requires 8000 m2 of solar panels. Let's say that we want some power headspace. 10000 m2 of solar panels required. Deploy that as 10x panels in 20x50 m form factors.

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Stacked end to end, that'd be 500 m for panels + 240 m for modules. Thus fulfilling the km scale requirements. This seems doable once LM-9 is out.

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krautmeister said:

The problem isn't this, it's that a kilometer scale spacecraft is so much bigger than everything else ever sent into space that it will be exponentially more likely to be impacted by debris large enough to cause catastrophic failure. That sort of catastrophic impact has never happened in the history of spaceflight only because spacecraft to date haven't been large enough for such an event to occur given the short span of the space age. However, with kilometer scale spacecraft, this will happen, and it won't take anything like 100 years. We're talking about an entire module being destroyed and killing everybody within its vicinity. This can't be a question of cost-benefit, the risk is just too great.

Both the CZ-9 and CZ-5DY are both going to have the payload capacity to loft whatever is needed to build this including extra shielding. I don't think this should be constrained by budget. Plus, any such accident would be a huge propaganda win by the Anglo-Americans, who would use it to attack China's tech reputation for decades, just as they use the CZ-3B failed rocket launch accident from the 1990s, that landed nearby killing a bunch of villagers. That was over 25 years ago and even to this day, it is still prominently used to attack and degrade China's tech.

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FairAndUnbiased said:

I think the best way to go about it might be to do an unmanned or optionally manned, lower risk project first (solar station with rolled out panels). see how it fares.

Then use the lessons learned from that to work on something manned.

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FairAndUnbiased said:

That just reduces the pressurized volume required. Is it worth it? ISS for instance places the batteries and many electrical systems outside.

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FairAndUnbiased said:

For a hypothetical km scale Chinese spacecraft, let's say that for it to qualify as km scale, it has to have at least 501 m length. Let's have it be assembled using modules launched by the

Please, Log in or Register to view URLs content!

Using equivalent form factor (3 meters lower than maximum rocket diameter) we have a 6.5 m diameter x 24 m length module with volume 800 m3 each or almost as big as the entire ISS volume.

Let's assume 25 launches: 10 pressurized modules, 15 for nonpressurized components (solar panels, backup power, radiators, instruments, maybe a laser CIWS... for debris only, of course). 10 modules would be 8000 m3 volume and can be used for living space, space farming, etc. End to end, the pressurized modules would be 240 m in length.

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krautmeister said:

There are now rumors that there might be a CZ-9 variant that will use the core stage as strap on boosters, increasing LEO payload to several hundred tonnes.

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