Author Topic: Monolithic vs Modular space stations (Read 9359 times)

reeceemmitt · « **on:** 08/08/2021 05:47 pm »

I have been doing a lot of reading on space stations designs recently...one of the benefits I guess of social restrictions in response to Coronavirus!

I was wondering if the experts here on this board had any comments on a question that I can’t decide my own view on: is the choice of modular space stations like Mir and ISS driven by the lack of effective heavy lift launch vehicles? If we had a HLLV - a SLS analogue maybe, in the 1990s, would the ISS still be modular or could we see a smaller number of much larger core modules.

I see the arguments in support of modular being greater flexibility in terms of growth and experimentation - but there’s been very little of that since construction of the ISS was completed - although I guess if we still had a ‘space truck’ like the shuttle that might happen more often.

Blackstar · « **Reply #1 on:** 08/09/2021 05:07 pm »

For decades the designers have concluded that they wanted the biggest modules they could fit in the largest available launch vehicles. Part of that was because of a desire to do as much equipment checkout as possible on the ground, rather than in orbit. It is much easier to fix problems on the ground than in space.

A friend of mine was involved in various human spaceflight programs over the past several decades, including shuttle and ISS. He was very disdainful of Bigelow's inflatable (or expandable) approach because he thought they had completely underestimated the difficulties of readying that spacecraft once it was in orbit. Having to put everything into position and then get all the fluid, data, and electrical systems operational was going to be very difficult, in his estimation. If he felt that way, certainly a lot of other people who looked at Bigelow's design felt that way too.

libra · « **Reply #2 on:** 08/09/2021 06:32 pm »

In a sense, the past and present modular space stations (Mir, ISS) are a mix of Salyut and Shuttle legacies. Before the 70's both NASA and Soviets had ultra large space station projects to be orbited by they lunar superboosters (MKBS and space base).

https://www.nasa.gov/sites/default/files/styles/full_width/public/thumbnails/image/space_base_concept_1969.jpg?itok=0zqvFSdn

https://falsesteps.wordpress.com/2012/08/15/mkbs-mirs-giant-ancestor/

Jim · « **Reply #3 on:** 08/09/2021 06:33 pm »

And wet stations made from a used stage are a fallacy. Not for decades.

libra · « **Reply #4 on:** 08/10/2021 05:34 am »

https://en.wikipedia.org/wiki/Nanoracks#Commercial_Space_Stations

Vahe231991 · « **Reply #5 on:** 08/20/2023 03:06 am »

The Starlab space station currently under development is a monolithic space station, thus rekindling the debate over the advantages and disadvantages of monolithic space stations compared to those of modular space stations.

Michel Van · « **Reply #6 on:** 08/21/2023 03:56 pm »

In early 1970s NASA prefer the Monolithic space station to be launch in one piece and fully installed.
Boeing, Rockwell and McDonnell-Douglas made several studies on them.

but over time rise a problem, lack of Saturn V do budget cuts !
there were Studies to use Shuttle first stage and large upper stage, to launch the Monolithic space station into orbit.
but as the budget cuts increased and the Shuttle first stage was replace by large Solid motors !
became the Modular Space Station popular, since a module would fit into Payload bay of shuttle.

but Capitol Hill show no interest into space station in 1970s...
...until Ronald Reagan in 1980s.

Coastal Ron · « **Reply #7 on:** 08/21/2023 04:12 pm »

Quote from: Vahe231991 on 08/20/2023 03:06 am

The Starlab space station currently under development is a monolithic space station, thus rekindling the debate...

What "debate"?

Look, if a "monolithic" space station is one that is built complete on Earth and then launched, the answer is clear - you are limited by the size of your launch vehicle. So if you built a space station into a SpaceX Starship, the largest amount of mass of that space station will be 100-150mT, depending on what orbit you put it into.

In contrast the current International Space Station, which was built from many modules, is over 450mT in mass, and there is no reason it couldn't be built bigger.

And what is missing from this is that it is not just Monolithic vs Modular, using the definitions above. The third option is to build the station in space not from modules, but from components. Like we build large buildings here on Earth.

So it is clear that "monolithic" space stations that are built on Earth and launched complete have a very limited use case. The future is building space stations from components, but before we get there the present is building stations from modules.

spacenut · « **Reply #8 on:** 08/21/2023 06:45 pm »

Quote from: Blackstar on 08/21/2023 06:37 pm

So you guys wanna discuss Starship, huh? I think there are a few hundred other active threads where you can discuss it.

Well, it has been suggested a Starship could be use as a Space Station, so there is overlap here. I think what Dan was referring to is a once and done Starship Space Station without fins, TPS, which could be stretched and include solar panels, docking port and interior designed as a Space Station. It would weigh probably 250+ tons as a Monolithic space station.

Coastal Ron · « **Reply #9 on:** 08/21/2023 06:55 pm »

Quote from: DanClemmensen on 08/21/2023 04:28 pm

Quote from: Coastal Ron on 08/21/2023 04:12 pm
Look, if a "monolithic" space station is one that is built complete on Earth and then launched, the answer is clear - you are limited by the size of your launch vehicle. So if you built a space station into a SpaceX Starship, the largest amount of mass of that space station will be 100-150mT, depending on what orbit you put it into.

In contrast the current International Space Station, which was built from many modules, is over 450mT in mass, and there is no reason it couldn't be built bigger.
I don't think your math is right. 150 tonne is the payload upmass for a reusable SS. The payload upmass for a non-returning SS will be quite a bit higher because the SS is lighter (no elonerons and no TPS). You also appear to be comparing the payload (i.e., contents) of the SS with the total mass of the ISS. For a valid comparison you need to add the mass of the SS hull. Finally, a modular station inevitably has a lot of mass in its module interfaces.

I don't consider a Starship as a "space station". Sure, it can be used as a temporary crewed platform, but for purposes of what a true "space station" is, where people are living and working for years, no, Starship is not a space station.

So I look at what a Starship could drop off in space as a monolithic "space station" (ala Skylab), while the Starship returns to Earth.

And again, to me a future "space station" is not a temporary outpost that people visit for short periods of time, but a place where people can live and work. The ISS is kind of a hybrid, which is OK because no one plans to replicate it.

But if the goal is to expand humanity out into space, and not just onto planetary bodies, then we'll need space stations. I think early ones will be modular, but as we learn how to do manufacturing in space that will shift to building whole space stations out of components, not modules.

edzieba · « **Reply #10 on:** 08/21/2023 08:34 pm »

You have just launched your large monolithic station, the largest that could fit in the largest launcher availale. You now have the more-space-in-space bug want more usable volume. Do you
a) Design, develop, built, test, and operate an even larger launcher, along with designing, building, testing, and operating an even larger design of station?
b) Build another of the station you just launched, lifted on the launcher that you just used, and attach them together.