Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: lunar resources (was Re: NASA's $3 billion ET Moonbase)
Date: Sun, 7 Jan 1996 21:52:03 GMT

In article <4cnaer$645@lace.colorado.edu> fcrary@rintintin.Colorado.EDU (Frank Crary) writes:
>>> No feasible wall will stop it all; the landing area really has to be paved.
>>> However, the idea of making the paving meters thick is silly...
>
>...But I'm not sure how effective a paved surface
>would be, in avoiding dust problems. _Initially_ it
>would be a dust-free place to land. But people and
>vehicles are going to track dust onto it. It might 
>require a bit of work to keep the surface clean.

Frank, you're assuming that nothing is done about keeping people and
vehicles dust-free.  If you're going to build a landing pad, you're also
going to build gravel (or possibly paved) roads/paths as dust-free routes
for people and vehicles to and from the pad.  Some attention to clearing
dust from the pad may be needed, but prevention should keep the problem
down to a relatively minor level.

>By the way, would landings be a significant source of
>dust, relative to other industrial activities? Digging
>up regolith to process for resources would also 
>raise dust.

However, it wouldn't toss it for kilometers.  Any major surface operation
on unimproved regolith is going to disturb a lot of dust, but it will
mostly be a very local problem; you just don't put your mining area in the
middle of the astronomical observatory.  The problem with landings is the
presence of high-velocity gas jets that can accelerate dust into long-
range ballistic trajectories, sprinkling it over huge areas of the
surrounding surface. 
-- 
Look, look, see Windows 95.  Buy, lemmings, buy!   |       Henry Spencer
Pay no attention to that cliff ahead...            |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: lunar resources (was Re: NASA's $3 billion ET Moonbase)
Date: Sun, 7 Jan 1996 02:37:27 GMT

In article <4cld1a$13e@nntp5.u.washington.edu> doyle@PROBLEM_WITH_INEWS_GATEWAY_FILE () writes:
>> ...the landing area really has to be paved.
>> However, the idea of making the paving meters thick is silly...
>
>The orginal regolith mined will be meters think...

Maybe, but not for the landing pad.  There's no reason to excavate a
landing pad to a depth of several meters, or to replace the regolith
with bricks (or what have you) to that depth.  The landing pad will
be *one* layer of bricks on top of levelled regolith.  The excavation
involved in this won't yield any large amount of regolith for processing.

If you want to excavate large amounts of regolith, fine, do so, but the
landing pad does not provide a reason to do it.

>...Also I am not sure
>how much regolith will compact when it melts and refreezes as
>a solid instead of a powder...

Depends on the process used.  You may want to compress and sinter it
rather than going all the way to melting; sintered materials are still
somewhat porous but can be quite adequately solid for many purposes,
and they may end up being easier to make.

>I think paving bricks would
>probably be easier to make than a solid surface. Extras could
>be used to make roads and paths to control dust.

There's no particular need for actual paving except in areas where large
amounts of gas are being thrown around, e.g. by rocket exhausts.  For
roads and such, where only contact forces could throw dust around, it's
much easier to just screen the regolith for cm-sized rocks and use them
as gravel. 

>I just was trying to solve two problems at once. The main point
>is that you can solve the dust problem and the lack of H,N, and C
>problem with the same equipment if it is designed right.

Only if your solution is vastly overdesigned for the dust problem.
A full solution to the dust problem involves much less excavation than
the provision of substantial amounts of volatiles would.
-- 
Look, look, see Windows 95.  Buy, lemmings, buy!   |       Henry Spencer
Pay no attention to that cliff ahead...            |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: dust control (was Re: lunar resources)
Date: Wed, 10 Jan 1996 00:30:09 GMT

In article <DKw0uG.28p@news.uwindsor.ca> blazek@uwindsor.ca (Robert Blazek) writes:
>A solid landing site sounds good, fewer dust problems.  As an
>alternative would covering a landing site, at least initially,
>in a thick blanket composed of local fiberglass (beta cloth)
>be also a good solution?

It's a workable way to hold down the dust.  The question would be whether
it's actually easier to do.  Making fiberglass cloth is considerably more
complicated than just melting or sintering regolith into bricks.

>Such use of fiberglass landing pad and walls could be especially
>helpful for future missions that involve temporary landing sites...

Well, there's the question of whether temporary sites really need dust
control, but that depends on what you're doing in the vicinity.  This
*is* the sort of case where fiberglass cloth would be better than bricks,
though, because it's a lot lighter to transport.

>Additionally aluminized fiberglass cloth on light aluminum frames
>may prove a quick and dirty method of sunlight concentration for
>solar panels and lunar mining...

If you've got aluminum, it's simpler to just use aluminum foil.  On
Earth, such a structure needs mechanical strength against wind, but
on the Moon, thin foil should do just fine.
-- 
The Earth is our mother.                           |       Henry Spencer
Our nine months are up...                          |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: lunar resources (was Re: NASA's $3 billion ET Moonbase)
Date: Fri, 12 Jan 1996 17:45:25 GMT

In article <4d3gmu$oar@nntp5.u.washington.edu> doyle@PROBLEM_WITH_INEWS_GATEWAY_FILE () writes:
>It does not matter to me if you excavate the landing area or 
>some area for regolith to make bricks.

It should.  You don't *want* the landing pad sunk in a hole.  That will
just worsen the problem of dust getting blown up in ballistic trajectories.
The landing area and excavation area need to be separate.

>> >[sintered bricks]
>> >To get all the volitiles out you need to get the regolith to 1200C
>> >which is slightly below the melting point.
>> Why do we want to get all the volatiles out of the bricks? ...
>
>You do not seem to understand the extraction process. If you dig up the 
>regolith and then heat it to make bricks, all you need to do is catch 
>the volitiles.

"All you need to do" to accomplish *what*?  To extract small amounts of
volatiles?  Sure.  To extract the amounts your plan envisions?  No --
no reasonable amount of brick-making will yield that much.

My point is, you're taking a perfectly reasonable idea -- making enough
paving bricks to pave the landing pad -- and then warping it badly, at
considerable extra cost, in hopes of using it as your main source of
volatiles.

You will be better off if you separate the two objectives, and admit that
no reasonable method of landing-pad construction will yield large amounts
of volatiles.  Then the brick-making process can be optimized to make
bricks, and the volatile-extraction process can be optimized to extract
volatiles.

If brick-making happens to yield *some* volatiles, great.  If volatile
extraction happens to produce bricks, great.  But it's silly to, for
example, dismiss sintering as a brick-making process just because it
doesn't yield all the volatiles you want! 
-- 
The Earth is our mother.                           |       Henry Spencer
Our nine months are up...                          |   henry@zoo.toronto.edu

Newsgroups: sci.space.policy
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: lunar paving (was Re: lunar resources)
Date: Mon, 15 Jan 1996 18:02:07 GMT

In article <4d4j7l$ljh@lace.colorado.edu> fcrary@rintintin.Colorado.EDU (Frank Crary) writes:
>>...In particular, if you're planning on using something like
>>Al/LOX engines, the exhaust will be very abrasive and the surface had
>>better be tough.  If it's just gas, though, sintered brick should be
>>enough -- that's how most Earthly brick is made.
>
>Abrasion wouldn't be the only concern. No matter what
>sort of rocket you are using, the heat from the landing
>will melt some of the bricks. Perhaps only the top 
>millimeter of the bricks directly under the lander,
>but each subsequent landing in the same spot will
>melt a little farther...

Actually, whether there would be any melting depends on the balance
between heating from the exhaust and cooling from radiation and
conduction.  It will help that high-expansion nozzles will spread the
exhaust out over a considerable area of the brick.  Cutting the engines
off a meter or two up would also help.  There was no obvious surface
melting under the Apollo LM descent engines, and that was with very
little conductive cooling -- paving bricks would do better.

However, Frank's got a point -- it will almost certainly be necessary
to repave the pad occasionally.
-- 
The Earth is our mother.                           |       Henry Spencer
Our nine months are up...                          |   henry@zoo.toronto.edu

Subject: Re: Apollo 12 dust
From: Henry Spencer <henry@zoo.toronto.edu>
Date: Jan 26 1997
Newsgroups: sci.space.history

In article <32e94f8a.92538700@nntp.ix.netcom.com>, om <om@ix.netcom.com> wrote:
>>   The later misions had a brush that was used to brush off the dust prior
>>to Lm ingress following the EVAs
>
>....On some flights, the brush didn't perform as well as it did on
>others...

In general, it's hard to get lunar dust off a porous surface with a brush.
Apart from the static charge, the dust particles are quite sharp-edged and
tend to get hooked in cloth surfaces.  Brushing tends to embed them more 
solidly rather than dislodging them.

Actually, the brush isn't an ideal answer even on smooth hard surfaces,
like the faceplates.  The dust is also very abrasive, and cleaning it off
the faceplates scratched them, fairly badly in the case of the long-stay
missions.

(People who blithely assume that the Apollo spacesuit design would be
suitable for a lunar base haven't looked at the kind of shape the Apollo
17 suits were in at liftoff, after only a couple of days of vigorous
surface activity.  Apart from his Apollo Lunar Surface Journal work,
Eric Jones has published a couple of papers on this, which make quite
interesting reading.)
-- 
"We don't care.  We don't have to.  You'll buy     |       Henry Spencer
whatever we ship, so why bother?  We're Microsoft."|   henry@zoo.toronto.edu

From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: ballistic ground-to-ground times
Date: Thu, 11 Feb 1999 03:07:01 GMT

In article <79n5tj$6ja$1@news-2.news.gte.net>,
Jerry Irvine <01rocket@gte.net> wrote:
>Offroad vehicles have sealed bearings so the "dust problem" would be no
>worse on mars than in the Mojave desert.  Even if it were "twice as bad"
>the bearings would last for years.

This is not to be taken for granted, alas.  The properties of Martian dust
are largely speculative.  The properties of lunar dust are not, and they
are *much* worse than those of typical Earth dust.  The stuff is extremely
abrasive and has a static-cling problem like nothing ever encountered
here.

On the later Apollo flights, with stays of only a few days and a total
(for each flight) of less than 24 hours outside in three moonwalks, gloves
and other heavily-used surfaces showed serious abrasion, minor mechanisms
(e.g., Jack Schmitt's visor) became clogged with dust and stopped working,
and despite substantial efforts at cleaning and lubrication, suit joint
rings, zippers, and hose fittings became stiff and difficult to operate.
Crew consensus was that the Apollo suit design was good for at most a
dozen moonwalks, and even that would require work space and substantial
amounts of time for cleaning crucial surfaces and assemblies.

Sealing a bearing against lunar dust is not the same as sealing it
against Earth dust.  Indeed, it's an unsolved problem.
--
The good old days                   |  Henry Spencer   henry@spsystems.net
weren't.                            |      (aka henry@zoo.toronto.edu)

From: gherbert@crl3.crl.com (George Herbert)
Newsgroups: sci.space.policy
Subject: Re: Space "Capsule" Space Suits
Date: 8 Jan 2000 17:44:54 -0800

Tom Durrant  <tom.durrantNOtoSPAM@lmco.com.invalid> wrote:
>Mars with its ever present dust will probably be an awful place for
>spacesuits-- particularly if you want to use that suit for two years.
>At this point I expect more virtual-EVAs than actual-EVAs on Mars, even
>if the astronauts are there for two full years.

Keep in mind that Mars dust probably (though we haven't seen it up
close yet) is more like Earth dust than Lunar dust.... since it's
windblown, it's probably been weathered and has got few rough edges.

Not that earth dust isn't a terror on certain mechanisms found in
spacesuits, for example, but Lunar dust is a terror squared if you
want to go qualatatively.  This is one of the areas where the Moon
is actually a harder problem than Mars is.

I think that given 10+ years to work on it, we'll be able to build
suits which are adequately mobile and long-lived for long Mars missions.


-george william herbert
gherbert@crl.com

From: gherbert@crl3.crl.com (George Herbert)
Newsgroups: sci.space.policy
Subject: Re: Space "Capsule" Space Suits
Date: 8 Jan 2000 22:28:29 -0800

Jonathan A Goff  <jongoff@et.byu.edu> wrote:
>On 8 Jan 2000, George Herbert wrote:
>> Not that earth dust isn't a terror on certain mechanisms found in
>> spacesuits, for example, but Lunar dust is a terror squared if you
>> want to go qualatatively.  This is one of the areas where the Moon
>> is actually a harder problem than Mars is.
>
>What does moondust effect the worst?  I imagine it plays havoc
>on almost everything, but which areas does it screw up the most?

Moving parts and fabrics; it's made up of unweathered sharp grains
which have been politely described as the anti-lubricant.  They will
just eat fabric if you get it in the weave, and if you get it into
joints it will gum them up amazingly quickly.

Earth and presumably Mars dust are mildly as opposed to aggressively
abrasive and not nearly as hard on joints.

>> I think that given 10+ years to work on it, we'll be able to build
>> suits which are adequately mobile and long-lived for long Mars missions.
>
>Ouch, that is a long time.  How long do you think it would be
>before we could get a long-lived moonsuit?  Or what about a suit
>whose most damaged parts were designed to be expendable, and
>were scrapped after use....I dunno, I just would like to find
>some solution to the problem.  In my strange view of the universe,
>that is actually one of the toughest problems that need to be met
>before a Moon base or Mars base gets setup.

It's not all that strange a view.  EVA experts generally believe that
EVA is one of the tougher nuts to crack on good planetary exploration.

A lot of the problem can be avoided with careful detail design.
Suits already consist of multiple layers.  For a lunar suit, a multi-layer
suit which had say an inner layer with the pressure bladder and joints,
a protective layer of plastic taped over the joints, a seperate inner layer
of insulation which is sealed for dust protection, an outer layer of dust
protection (similarly sealed), and some strap-on abraision pads at elbow
and knee and butt (unpressurized rover driving).

The design intent is to seal off the sensitive parts from the dust,
and throw away the outer parts as they get irreperably dust saturated
and damaged.  The middle insulation layer would get some dust exposure
but not much and would have a long life.  Hopefully the inner suit proper
would avoid any significant dust exposure over time.  The outer layers
don't weigh much, so replacing them every few days isn't a mission
breaking mass issue.  The inner layers are heavier and more sensitive,
so you need to protect them better...


-george william herbert
gherbert@crl.com

Date: Sun, 09 Jan 2000 08:50:10 -0800
From: Doug Jones <random@qnet.com>
Newsgroups: sci.space.policy
Subject: Re: Space "Capsule" Space Suits

Jonathan A Goff wrote:
>
> On 8 Jan 2000, George Herbert wrote:
>
> > Not that earth dust isn't a terror on certain mechanisms found in
> > spacesuits, for example, but Lunar dust is a terror squared if you
> > want to go qualatatively.  This is one of the areas where the Moon
> > is actually a harder problem than Mars is.
>
> What does moondust effect the worst?  I imagine it plays havoc
> on almost everything, but which areas does it screw up the most?

I'll hazard a guess that it is similar to a problem that cropped up in
sport parachuting about 15 years ago.  Kevlar suspension lines became
popular because they were much thinner that the comparable nylon lines
(allowing smaller pack volumes), but they weren't very durable.  It turns
out dust would get between the fibers of the braided cord, then when
tension was placed on the lines and the braid compressed, the sharp edges
would slice through the fibers.  Aramid fibers are much harder than nylon,
so the dust acted like tiny knives instead of being caught in the soft
surface of the fibers.

IIRC, nylon-coated kevlar solved the problem.

--
Doug Jones
Rocket Plumber, XCOR Aerospace
http://www.xcor-aerospace.com