What ever happened to on-orbit assembly?

In article .net,
Joseph Oberlander wrote:
Not as easy as on the moon. Even the small amount of gravity and the
fact that you can easily pressurize underground hangars and such means
that you can do major fabrication and work instead of just assembly.

Gravity is as much a hindrance as a help for major assembly work. It's
not clear that it's a net win.

You can build pressurized hangars just as easily in open space as on the
Moon, probably more easily in fact.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

On Tue, 11 Nov 2003 17:53:22 GMT, (Henry Spencer)
wrote:

snip
But nobody's doing anything ambitious in space.

Will we ever in our childrens life time, let alone ours?



Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

In article ,
(Henry Spencer) wrote:

There has been experimental work on "hard suits", in which all joints are
rotating joints (doing this for elbows etc. is tricky but possible, with
multiple joints at an angle to the arm axis) and there is no change in
volume with joint motion. This eliminates the single biggest problem, the
balloon effect. The hard suits are mostly okay, although not yet fully
developed, but have two big problems: the gloves are not okay, in fact
they're reportedly awful, and the suits are very heavy.

Thanks for the info. Thinking a little outside the box here, this
suggests a hybrid approach, where most of the suit is rotating joints,
but the suit's hands are actually completely robotic, teleoperated from
six inches away by the wearer's hands, which are completely inside the
arm of the suit. It would look a little odd, with your forearms
apparently half a foot longer than they should be, but I suspect that
with a little practice you'd get used to it pretty quick. A nontrivial
engineering job to be sure, but probably doable with current technology.

The major alternative is to get rid of the air in the suit entirely, by
making the suit (well, except for the helmet) just a layer of stretchy
fabric over the skin, pressurizing the body mechanically and relying on
the skin itself to supply the seal. The basic principle works -- it's
been tested -- but there are some significant remaining engineering
problems in making a practical spacesuit that way.

On the face of it, this sounds like a more reasonable approach, though
it's hard to know if those problems would be show-stoppers.

There basically hasn't been very much funding for advanced suit R&D. What
little there has been has been mostly for high-pressure suits -- mainly,
the hard suits -- in hopes of eliminating prebreathing requirements.

A pity -- this is one of those basic enabling technologies that would be
a good job for NASA.

I'm sure that once we get serious construction crews in orbit (or on the
Moon), whoever's in charge of those crews will develop better suits that
make their people more productive. But it'd be nice to have those suits
already developed, to reduce the chicken-and-egg problem.

,------------------------------------------------------------------.
| Joseph J. Strout Check out the Mac Web Directory: |
| http://www.macwebdir.com |
`------------------------------------------------------------------'

In article ,
Joe Strout wrote:
...suggests a hybrid approach, where most of the suit is rotating joints,
but the suit's hands are actually completely robotic, teleoperated from
six inches away by the wearer's hands, which are completely inside the
arm of the suit...

Two problems:

(1) It's actually quite difficult to even approach the mechanical
capabilities of human hands in a robot hand. People tend to think this
is routine, off-the-shelf engineering, but it's not, although the
situation is slowly improving. Human hands are very complex.

(2) Providing a reasonable level of force feedback, so you can tell how
hard the robot hand is squeezing and feel what it's grasping, is still
pretty completely a research topic.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

On Wed, 12 Nov 2003 14:10:07 GMT, (Henry Spencer)
wrote:

In article ,
Kaido Kert wrote:
Partly, as others have noted, the crude state of spacesuit technology has
been a roadblock.

Hm. The art of designing products for robotic assembly is widely practiced
principle in industrial automation... Why wouldnt that work in space ?

It would, if we were building spaceships in the kind of numbers needed to
make it worthwhile. (You need to debug such processes, so they rarely
save you any effort for a very short production run.)

How big an economy of scale would we be looking at, something like a
747 assembly line?

Arguably, a lesser form of that is practiced already, in designing modules
to be docked together automatically or semi-automatically.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Christopher
+++++++++++++++++++++++++
"Kites rise highest against
the wind - not with it."
Winston Churchill

Henry Spencer wrote:

In article .net,
Joseph Oberlander wrote:

Not as easy as on the moon. Even the small amount of gravity and the
fact that you can easily pressurize underground hangars and such means
that you can do major fabrication and work instead of just assembly.


Gravity is as much a hindrance as a help for major assembly work. It's
not clear that it's a net win.

It is for the crew and people who live there. One of the biggest problems,
though, is lack of a solid footing in space. With enough force, the entire
dock would move. Another bonus is that people could live on the moon and
be fairly healthy as even a little gravity is better than none for long periods

You can build pressurized hangars just as easily in open space as on the
Moon, probably more easily in fact.

Underground facilities not only protect you from radiation, but also are
MUCH simpler to make air-tight. Just spray some form or simmilar on the
interior walls and make an airlock or two. No micrometiroites, no docking
mishaps. Dug deep enough, it would also be room temperature.

(Henry Spencer) writes:

In article ,
Joe Strout wrote:
Partly, as others have noted, the crude state of spacesuit technology has
been a roadblock.

...Is there anything else that would help, in the design of the suit itself?
Would a rigid suit, similar to those used for deep-sea diving, make it
easier to work in?

There has been experimental work on "hard suits", in which all joints are
rotating joints (doing this for elbows etc. is tricky but possible, with
multiple joints at an angle to the arm axis) and there is no change in
volume with joint motion. This eliminates the single biggest problem, the
balloon effect. The hard suits are mostly okay, although not yet fully
developed, but have two big problems: the gloves are not okay, in fact
they're reportedly awful, and the suits are very heavy.

The major alternative is to get rid of the air in the suit entirely, by
making the suit (well, except for the helmet) just a layer of stretchy
fabric over the skin, pressurizing the body mechanically and relying on
the skin itself to supply the seal. The basic principle works -- it's
been tested -- but there are some significant remaining engineering
problems in making a practical spacesuit that way. Whether they can be
solved easily, with difficulty, or not at all is unclear -- funding has
been inadequate for a thorough investigation.

I wonder if the idea of the suit itself for major work is
missing a point. How about a vehicle that allowed manipulation
like a suit. I'm thinking about a 2001-style pod that has the
equivalent of a glovebox tools on the outside. This lets the
astro work essentially shirtsleeve and have reasonable access
to a richer environment to work in than provided by a traditional
suit. Why do legs need to be encasulated as "legs" all? Maybe
the right astronaut body is Jabba the Hut, and the right suit form
factor is one that would fit him.

-dB



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"The statements and opinions expressed here are my own and do not necessarily
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Joseph Oberlander wrote:

Henry Spencer wrote:

Gravity is as much a hindrance as a help for major assembly work. It's
not clear that it's a net win.

It is for the crew and people who live there.

I'll have to side with Henry on this.

One of the biggest problems,
though, is lack of a solid footing in space. With enough force, the entire
dock would move.

Build the dock in the shape of a ring, with the object under assembly locked
down in the center.

Another bonus is that people could live on the moon and
be fairly healthy as even a little gravity is better than none for long periods

But the best solution of all would be an orbital dock with a rotating section
which could keep the crew under 1-G of centrifugal force while off duty.

Underground facilities not only protect you from radiation, but also are
MUCH simpler to make air-tight. Just spray some form or simmilar on the
interior walls and make an airlock or two. No micrometiroites, no docking
mishaps. Dug deep enough, it would also be room temperature.

These might be better points.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

(Henry Spencer) wrote:

The weight is not that big an issue in orbit, although it would be a grave
problem for planetary operations. (Even the shuttle suits are too heavy
for Mars.)

Would not gross mobility be affected by mass? All else being equal it
seems it would be easier to move in an arm/hand assembly weighing x
than one weighing 2x.

D.
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Corrections, comments, and additions should be
e-mailed to , as well as posted to
sci.space.history and sci.space.shuttle for
discussion.

Mike Combs writes:

Joseph Oberlander wrote:

Underground facilities not only protect you from radiation, but also are
MUCH simpler to make air-tight. Just spray some form or simmilar on the
interior walls and make an airlock or two. No micrometiroites, no docking
mishaps. Dug deep enough, it would also be room temperature.

These might be better points.

Might. It depends on how hard it is to dig such facilities, how easy
it is to make them airtight, etc. The devil's in the details.

You wouldn't have micrometeorites, but instead of docking mishaps,
landing mishaps are certainly possible. In general, I would think
that it would take far less delta-V to abort a docking with a zero-g
space station than it would take to abort a moon landing and head back
into lunar orbit.

In general, gravity wells are a P.I.T.A. if you're doing large
assembly projects, unless you're using a very high percentage of
indigenous materials at the assembly site.

Jeff
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