Space station design and the need for space walks

I've been watching NASA TV for a few weeks now, more or less keeping
up with the antics of the current station crew. There are four things
that have jumped out at me right away:

1. The interior of the station tends to be a mess. I understand that
in microgravity stuff is going to float aimlessly. Why aren't systems
designed to avoid having tethers and ropes and such? This is just my
organized german heritage sneaking through, but I'm watching the crew
fool around with the russian space suits, and the entire compartment
is a mass of cables, floating suits and various paraphernalia. Why
aren't the suits locked down? Why are there so many flaps and zippers
and such on the thing? Why are there so many things to check? It
seems like it's one checkmark towards the three things that need to
simultaneously go wrong in order to have a disaster on the station.

2. The spacewalk that the crew is planning for and training for is to
replace a module that is mounted on the outside of the station. Why
the heck would people put such equipment on the OUTSIDE of the
station? I can understand why some things need to be outside. Solar
panels need sunlight. Cameras need line of sight to something
interesting. And so on. But why would anything requiring maintenance
be placed in such an inaccessible location? Is there a fear that it's
going to blow up or catch fire?

3. The spacewalk that the crew is planning for and training for is
consuming countless man hours. They're going out in order to replace
one or two pieces of equipment. They've been planning and training
for the spacewalk in bits and pieces for weeks, perhaps months -
including ground training. Then there's all the people who are
working with them from the ground, both in Russia and the United
States. Heck, they even have a step by step plan for how to move from
point A to point B outside the station, including which handholds to
use. Is my thinking that this is extraordinarily excessive a
reflection of consuming too much science fiction? Or is this just a
really complicated spacewalk because of the inclusion of the russian
suits and ground crew?

4. The components that are being replaced appear to involve using a
tool that is the equivalent of a cordless drill. In order to keep the
astronaut from rotating in reaction to the torque of the tool he's
using, there is a tether or some sort to help keep him in place. Why
aren't the tools and fasteners designed to work appropriate to the
environment? Is this just a matter of cost? That it's simpler to
design the tether than to design a tool or fastener appropriate to
space? That we just don't have enough experience with space
construction, so we use stuff that we KNOW will stay attached (i.e.
screws and bolts instead of stuff with simpler ergonomics).

An immediate solution that springs to mind for a lot of this is to
have infalatable bags surrounding the trusses and other 'exterior'
components of the station that need to be reached. It would provide
for a lot more room to move around, and would permit maintenance of
the entire station without any spacewalks. I'm assuming right away
that this idea has major flaws to it, but for the life of me I can't
see what they might be other than issues of cost. I know folks are
already working on invatable living quarters that integrate kevlar and
other materials. Given all the hassles and cost of spacewalks, it
just seems so odd to not address this from the start.

Comments from the better-informed would be appreciated.

JB

In article ,
John Buehler wrote:
4. The components that are being replaced appear to involve using a
tool that is the equivalent of a cordless drill. In order to keep the
astronaut from rotating in reaction to the torque of the tool he's
using, there is a tether or some sort to help keep him in place. Why
aren't the tools and fasteners designed to work appropriate to the
environment? Is this just a matter of cost?

No, it's because restraining astronauts against tool torque has turned out
to be a very minor problem. They need to be restrained *anyway* to work
effectively; it's just not possible to do anything much while floating
loose (that was one of the lessons of the later Gemini spacewalks). So it
simply makes sense to stick with orthodox fasteners that work well rather
than inventing something new.

In the early 60s there was a lot of work on things like torqueless power
screwdrivers. None of it turned out to be at all useful.

An immediate solution that springs to mind for a lot of this is to
have infalatable bags surrounding the trusses and other 'exterior'
components of the station that need to be reached. It would provide
for a lot more room to move around, and would permit maintenance of
the entire station without any spacewalks. I'm assuming right away
that this idea has major flaws to it...

Unfortunately, providing those bags with protection against space debris
and micrometeorites, temperature control, adequate ventilation (which
can't be taken for granted in free fall the way it can be on Earth), etc.,
is not a small job. The idea is not ridiculous but it's not nearly as
simple as it looks.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

Henry Spencer wrote:
In article ,
John Buehler wrote:
An immediate solution that springs to mind for a lot of this is to
have infalatable bags surrounding the trusses and other 'exterior'
components of the station that need to be reached. It would provide
for a lot more room to move around, and would permit maintenance of
the entire station without any spacewalks. I'm assuming right away
that this idea has major flaws to it...

Unfortunately, providing those bags with protection against space debris
and micrometeorites, temperature control, adequate ventilation (which
can't be taken for granted in free fall the way it can be on Earth), etc.,
is not a small job. The idea is not ridiculous but it's not nearly as
simple as it looks.

Neither of you are thinking of the problem correctly.
If you're going to have a pressurized volume in space
that's supposed to be at least a semi-shirt-sleeve
environment then you might as well just go all the way
and make it a permant part of the station's pressurized
volume. Bring the truss inside an inflatable hull.
Of course, this somewhat defeats the purpose, as would
the bags, of having exterior support structures, and
you're going to need the structure to pass through
the pressure hull regardless.

Besides which, with any station there will always be
an outside and there will always be parts there that
need servicing. The only way to build a habitat
without any outside parts is to have the outside be
the "border" of an atmosphere held in place by some
force or other, such as gravity. But, barring new
developments in force fields and whatnot, this
solution rather defeats the purpose of having a space
station.

"Christopher M. Jones" wrote in message ...

Neither of you are thinking of the problem correctly.

I hate it when I do that.

If you're going to have a pressurized volume in space
that's supposed to be at least a semi-shirt-sleeve
environment then you might as well just go all the way
and make it a permant part of the station's pressurized
volume. Bring the truss inside an inflatable hull.
Of course, this somewhat defeats the purpose, as would
the bags, of having exterior support structures, and
you're going to need the structure to pass through
the pressure hull regardless.

This was the intent of my post. I used the term 'bag' to denote a
flexible enclosure around the trusses and was limiting myself to some
kind of 'next step' beyond having the station itself be the true
living space and then have a shirtsleeve environment (perhaps
on-demand, inflatable) around sections of the exterior structures.

In the past week, I've just dumped the whole middle-of-the-road
approach and decided that what I want (with my copious funds) is a
geodesic sphere perhaps a hundred meters in diameter(arbitrarily
impressive number) which is entirely filled with a shirtsleeve
environment. Perhaps concentric spheres, for safety against fire,
impact and so on.

Place docking ports at junctions of the geodesic support structure -
or go with triangular docking ports between the junctions. Mount
triangular solar panels on the outside of the sphere, again relying on
the rigid structure of the geodesic. That uniform exterior can
probably be leveraged in many ways that the non-uniform exterior of
the ISS cannot.

In the case of a ship-to-station collision, the damage might be
lessened if fragile structures weren't sticking out, waiting to get
knocked off.

Besides which, with any station there will always be
an outside and there will always be parts there that
need servicing.

Very true. As I see it, it is tremendously more complex, expensive
and dangerous to perform human maintenance in space than it is in a
microgravity shirtsleeve environment. Every effort should be made to
keep all human activities in that shirtsleeve environment.

All the bits and pieces seem to be in place or under development.
Personal assistant thingamabobs in the shirtsleeve environment.
Walking arms to move around the exterior of the station. People on the
ground should be able to remotely operate those things just as easily
as the crewmembers can, eliminating routine maintenance from the
extremely scarce commodity of astronaut labor.

The geodesic sphere is there to give a huge working and living space,
and also to give a uniform surface on the exterior for the walking
arm, solar panels, antennae, materials experiments, and so on.

Ah, it's fun to design things when you don't know what you're talking
about in much depth, don't have to actually build them and definitely
don't have to get funding for.

JB

(Henry Spencer) wrote in message ...
In article ,
John Buehler wrote:
4. The components that are being replaced appear to involve using a
tool that is the equivalent of a cordless drill. In order to keep the
astronaut from rotating in reaction to the torque of the tool he's
using, there is a tether or some sort to help keep him in place. Why
aren't the tools and fasteners designed to work appropriate to the
environment? Is this just a matter of cost?

No, it's because restraining astronauts against tool torque has turned out
to be a very minor problem. They need to be restrained *anyway* to work
effectively; it's just not possible to do anything much while floating
loose (that was one of the lessons of the later Gemini spacewalks). So it
simply makes sense to stick with orthodox fasteners that work well rather
than inventing something new.

In the early 60s there was a lot of work on things like torqueless power
screwdrivers. None of it turned out to be at all useful.

I was thinking more of isometric ergonomics. Squeeze things from both
sides to open or close them, etc. The action of operating the
fastener is more consistent with the environment.

I suppose the apparent hack of the torque strap is what really bothers
me. I'd prefer to see something that permits an astronaut to fix
himself to the work site and move about and work more naturally. The
energy output by astronauts is apparently extremely high. They're
working hard out there. I'm sure that part of that is because they're
constantly floating around.

I just had a strange thought that dovetails with Chris Jones' post
about atmosphere on the outside of a structure. Perhaps not
atmosphere, but if the exterior of the station was a geodesic sphere,
a system that gives the astronauts the impression of light gravity
could be implemented (no pun intended). If a rig that pushed down on
the astronaut existed, then could rely on 'up' being 'away from the
center of the station'. Just something to hold them in place on
demand. Attached at the small of the back, perhaps.

Of course, I don't want astronauts doing work in space suits anyway,
so hopefully that can be turned into a moot point eventually.

JB

David Given wrote in message . ..
On Wed, 07 Jul 2004 07:58:32 -0700, John Buehler wrote:
[...]
In the past week, I've just dumped the whole middle-of-the-road approach
and decided that what I want (with my copious funds) is a geodesic sphere
perhaps a hundred meters in diameter(arbitrarily impressive number) which
is entirely filled with a shirtsleeve environment. Perhaps concentric
spheres, for safety against fire, impact and so on.

Would you actually need a true geodesic sphere? Could you make do with an
inflatable balloon? That would make it considerably easier to deploy, as
well as being a generically simpler structure.

Much simpler structure, but too many limitations for my taste.

1. Hard docking of vehicles would shake the bubble structure.

2. You probably don't want everything inside to be floating around, so
you'll either want to secure structures to the interior surface or
just kinda brace against the interior surface.

3. The largest thing that you can stuff inside the bubble is
restricted by the size of your port - unless you rely on deployable or
composable structures on the interior.

4. Damage to the bubble means that the entire surface is damaged (it's
one piece.) If repair of a puncture is not possible, the entire
bubble must be replaced. I think you'd also have to do some funky
'guarding' of the docking port area because it serves as a
discontinuity in the surface of the bubble.

5. Changes are problematic. Additional ports, expansion, etc. If you
want a larger station, you've gotta move everything from the old to
the new.

6. I don't know if you could apply much of any kind of a surfacing to
the bubble (such as solar collectors) given that it would impair the
flexibility of the bubble. That would certainly be a nice-to-have,
given the 'inflate and use' quality desired.

Other advantages: flexible! Minor collisions would be much less of an
issue. Depending on how much the envelope gets deformed, you may get
internal structural damage, but provided the envelope remains airtight,
that can be dealt with. You do end up with weak points where the thing is
bonded to the anchor --- a tear here could be disastrous --- but there's
probably easy enough engineering solutions to that.

The flexibility of the surface can be accomplished to a degree with
the geodesic sphere approach. Consider the Mars landers and their
airbag system. That was mounted to a pyramid shape with triangular
facets. The same could be done with the triangular facets of a
geodesic sphere in order to control various qualities of the surface.
Only you wouldn't need to deploy and collapse on remote command.

Fill the kevlar/unobtainium bags with useable liquid or gas and you've
got a flexible surface that can be altered locally by deflating bags
and/or removing them, to be replaced by docking ports, hangar doors,
experiment modules, etc. The surface is essentially uniform, so
everything would be designed to a simple standard.

Alternately, tack on chunks of aerogel to the exterior for shielding.
They're extraordinarily lightweight and I believe aerogel was used to
collect high-velocity particles on a comet mission. Manufacture the
aerogel in space and you only need to transport the raw materials up
(transporting aerogel itself - bleh). It would seem to be simple
enough to attach to the surface so that it would slow any incoming
debris. It might even serve as a dust-mop to help clean up space.
That's assuming that it doesn't throw off even more debris when hit.
I know that the stuff can cleave if you drop a chunk on the floor.

One issue is that any material thin enough to be a good candidate for your
envelope is probably not going to supply much of a radiation shield.

Stuff radiation-deflecting substances into the airbags and you're all
set.

Fabrics and plastics are mostly made of light elements. This is only going
to be suitable for LEO, unless you go for more exotic solutions (the
multiple layers you suggest, perhaps with water or sealing gel in the
intermediate layers). You might end up having to have metal enclosures
inside the envelope for, say, sleeping quarters.

In thinking about the interior, I might go with a similar
triangle-deconstruction approach for building stuff inside the
station.

Consider that models in computer graphics are deconstructions to
triangles (guaranteed to be planar, which simplifies the
computations). Triangles permit a lot of shapes to be composed.
Equilateral triangles would be a restriction on the shapes that you
could build, but that's life.

How about a LEGO-style construction system available in space where
each triangle has a tubular metal frame with various interiors. Power
and communications could be channeled through the frame, and different
interiors could probide a number of functions, including privacy,
lighting, cooling, heating, etc.

And triangles are great for lightweight, strong structures.

I'm envisioning launching something that's basically just an airlock with
a folded up balloon attached to it. After being placed in orbit, you
simply inflate the balloon and dock a standard spacecraft to it... hah! In
an earlier post I suggested using disposable habitats as a space shuttle
replacement. These would be ideal.

As a software engineer, I dislike solutions that lock me into my one
choice, which is why I went with the geodesic sphere. I like being
able to deconstruct and reconstruct stuff as conditions change.

Given the triangular components that form the geodesic sphere, other
shapes can be created (sphere-capped tube, cube, toroid, etc.), and
the diameter of the station can be increased simply by adding more
triangular panels. Or spheres can be mated, creating a 'cluster of
bubbles' effect. Also, the triangular panels are very compact for
transport or storage. The thinner the better.

In the interior, the astronauts could be reconfiguring and redesigning
their spaces for different needs. Space is at a premium, and being
able to reconfigure it for various purposes would seem to be an aid
not only to efficiency, but to the psychological well-being of the
crew. Efficiency would be eroded if too much reliance is placed on
being able to reconfigure the interior - they'd be spending all their
time resetting the interior.

As a novelist, I'm starting to get some ideas here

JB

Jan Vorbrüggen wrote in message ...
The energy output by astronauts is apparently extremely high. They're
working hard out there. I'm sure that part of that is because they're
constantly floating around.

I thought most of that was because they are fighting against the stiffness
of the suit.

Sure. Unfortunately that doesn't nail down what they're doing while
fighting against the stiffness of the suit. Are they doing the tasks
in the mission profile or are they overworking because of issues
related to free fall?

JB