Wasted Weight in Space?

Keeping it rigid makes sense, notably accommodating the acceleration to send it into orbit. Heavy mass would also limit movements of the space station when people move around within it. The part about routing electricity and liquid coolants makes little sense; those would not entail heavy structural support.

The various modules all have enough strength to maintain pressure and survive launch forces. What I don't understand is the function of a separate frame, which only gets used under zero G conditions to keep the assembly aligned. Most aerospace construction is monocoque, even for high G loadings. The Atlas rocket can't even support its payload when not pressurized by fuel.

What pressure do they keep the internal atmosphere at in the station?

A little PSI creates a lot of force when applied over large areas.

They maintain the same pressure we enjoy on earth in the ISS, although other space vehicles have gone down to 1l3 of that, and even airliners use reduced pressure.

It might be essential to reduce the effect or contain damage in a small area in the event of hits by other orbiting objects or passing objects.

Essential services like electricity or coolants also need special protection.

The ISS structure would require to be well supported. Despite being in "weightless" space there are many stress that it has to endure. Aside from the thermal ones, whenever a orbit correction is required the whole structure has to deal and absorb the inertial forces of the atitude rockets.

While it may not have "weight" it certainly has mass. Newtonian forces still apply.

There are other better qualified CR4 members who could supply the math for you.

The ISS usually gets its velocity restored with a boost from a shuttle, but the standard rockets provided accelerate it at under .004g, which is appropriate for the interior storage arrangements. Total thrust is under 800 kg, which seems like an easy incidental load to add to such massive pressure vessels. If it did pose any problem, the thrust could be reduced by a couple of orders of magnitude without any problem over the results.

I think that is for thermal mass. I have seen a piece of iron that have passed through several million cycles, lets say from -40deg C to 50 deg C, without or with very small load, and it was like eaten on the surface, in some places missing 1/16, in some places more. On the space station, the cycling can be much deeper in temperature.

The effect of thermal cycling erosion would be more important on the relatively thinner material of the pressure-containing inhabited modules. My question really is about what loads does the frame carry, apart from those it generates itself by being of different thermal characteristics? If some intrepid spacewalker were to disentangle the wiring from it, and unbolt the connections, would it not just fly formation, or slowly drift away if pushed? How would the other astronauts know, if the windows were blocked, etc.? Presumably, the renovations would include some reinforcing at the joints, but much weight would be saved.

I should put in a caveat here that not all of my references are well dated, so various quantities quoted might be out by 50%, but we are talking about much bigger differences. The weight of the frame for the pickup-truck style box-on-frame assembly comes to at least 2% of the finished weight. I wonder if that is 100% wasted. One reference noted that the planning was haphazard, so the frame might be a cost of limited thinking. The shuttle's solid-fuel boosters were added to take care of unplanned weight.

Anyway, the outward air pressure on the end of the Proton module is over 135,000 kg, so it should be able to handle the 8,000 kg inward force due to normal acceleration from a single rocket location on itself. Even if things were loaded in bending, there seems to be plenty in hand. A few lines of rigging could triangulate anything nicely.

if it ever becomes a gas station, refuelling to craft at once, as in the movie "Armageddon"... it might have to experience shocks and rotations...

from a modular point of view, a rigid backbone kind of makes sense, for R and R of components.

If it was just mass they needed, the could use water as mass. the specifiy strength..

I don't know.

Chris

GA and nicely said - saved me typing a diatribe on center of gravity and inertia too

Hi Easyway, Maybe they build like this to withstand the forces that we have on earth, transportation of the modules to the launch site and the launch itself would have incredible stresses on modules. I suppose that they cant afford any stress fractures in the transporting stages, so they build it like a brick shit-house, but I do understand where you are coming from, but i am no expert, but i have been to Cape Canaveral a few years ago, but that makes me no expert.

But now with the development's in nano technology's, they are probably looking at new materials for outer-space modules!

Cheers

Joe

What are the rotational forces on the ISS?

The rotational forces are presumably about nil, to keep the solar panels lined up. They are not using spin for artificial gravity. We have all seen video of ISS crew floating around, and manipulating stuff, and of spacewalks, so why would a frame not also just fly along? The normal maneuvering loads, even if applied at only one point, are far below the loads being handled by the modules as pressure vessels.

You've obviously looked into this in more detail than I have so I'm just throwing brainstorming questions out right now. That being said, the ISS is rotating about the Earth right?

You might be right that the rotational forces are close to zero but these forces seem to add up quick.

We may be missing the most obvious. Could this have been built in for a future expansion to the space station? May be to build a larger structure at a later date. They would have to plan for that possibility in advance.