A Space & astronomy forum. SpaceBanter.com

Go Back   Home » SpaceBanter.com forum » Space Science » History
Site Map Home Authors List Search Today's Posts Mark Forums Read Web Partners

Questions about "The High Frontier"



 
 
Thread Tools Display Modes
  #241  
Old October 19th 07, 06:47 AM posted to rec.arts.sf.science,sci.space.history
Troy
external usenet poster
 
Posts: 27
Default Questions about "The High Frontier"

On Oct 18, 10:44 pm, Pat Flannery wrote:
Troy wrote:

Dock an ion drive to a Bigelow module and you would have a manned
asteroid expedition.


I don't know how radiation proof those synthetic fabric walls are going
to be.

Pat


They'd have to be uprated for interplanetary space, that's for sure. A
5cm layer of water is supposed to be sufficient shielding - and
synthetic fabric's a lot safer than the radiation bath you'd get from
an aluminium hull.

  #242  
Old October 19th 07, 06:59 AM posted to rec.arts.sf.science,sci.space.history
Troy
external usenet poster
 
Posts: 27
Default Questions about "The High Frontier"

On Oct 18, 11:45 pm, Quadibloc wrote:
On Oct 17, 12:56 pm, Hop David wrote:

I agree moon habs will have lower start up costs. But why would Martian
habs be less expensive than NEO based habs? There are NEOs that can be
reached with less delta vee than Mars and with launch windows of
comparable frequency.


The start up cost of a small Martian habitat would be larger, since
initial supplies would be launched from Earth.

But the cost of expanding the habitat, while it would still be larger
than costs of Earth habitats - they would have to be airtight -
doesn't involve gallivanting around the Solar System to pick up
asteroids for metals and comets for volatiles. Surface transport will
do.

John Savard


In zero-g, you could probably use some kind of Venetian glass-blowing
technique to inflate a large pressure vessel from molten steel. A
little axial rotation would get you a disc shape, a little tug on the
ends would get you an ellipsoid. O'Neill suggested a magnetised steel
spray.

Yes, getting materials from other asteroids is trickier than scooping
them up with a rover but it can be done. Raw materials could be
supplied by unmanned solar sail craft scooping it off other asteroids,
if absolutely necessary. However, I believe the idea is to go
prospecting for one with the right mix of materials.

Sure, Mars and NEO are different, but I don't see them as having to
necessarily compete. But somebody, sooner or later will start to
utilise NEOs. NASA can go off and set up Mars colonies (actually the
Russkies are more apt to do that), Japan can build SPS, ESA can
develop the moon and India or China or private companies can go haring
after space rocks.

  #243  
Old October 19th 07, 06:46 PM posted to rec.arts.sf.science,sci.space.history
Mike Combs[_1_]
external usenet poster
 
Posts: 401
Default Questions about "The High Frontier"

"Pat Flannery" wrote in message
...

The winds will help to some extent.


Yeah, but think about putting an electric fan into a bell jar and pumping
out 99% of the air. It wouldn't surprise me if the fan didn't seriously
overheat, even with the added air movement.

You can drill down into the surface, and used a closed-loop system to
cycle something through a heat exchanger that dumps internal eat into the
bedrock where it migrates away via conduction.


Eh, maybe. I'm still concerned that that bedrock is covered by regolith, so
I'm thinking you'd quickly get into diminishing returns. It's not like the
bedrock is like a big slab of iron or aluminum.

On the other hand, radiators might not be that big a problem in orbit. One
thing you could do in weightless which you could never do under gravity is
have a heat radiator 3 inches thick but 3 square miles in area which
moreover can radiate heat away from both sides.

You are probably going to want the base primarily underground, or at least
have soil covering it for radiation protection, and that will be easier to
do with some gravity on your side to keep it in place.


The old space colony studies recommended fusing the slag left over from the
ore refinement process into 6-foot thick slabs which would then be assembled
into a radiation shield surrounding the habitat. I don't see much of a
problem with that approach. Molds could be heated at the focus of a big
solar mirror. That strikes me as uncomplicated and inexpensive.

Transparent inflatable domes might be tough though; there's unfiltered
high-UV sunlight to deal with, as well as radiation degrading of the
dome's material.


I'd agree. I'm more optimistic about glass windows set in steel or aluminum
frames than transparent, inflatable material.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn


  #244  
Old October 19th 07, 06:52 PM posted to rec.arts.sf.science,sci.space.history
Mike Combs[_1_]
external usenet poster
 
Posts: 401
Default Questions about "The High Frontier"

"Hop David" wrote in message
...

We don't know what gravity's needed to stay healthy. This argument also
works against orbital habs. So long as mammoth O'Neill cylinders are
perceived as entry level orbital habs, people will dismiss them as
implausible science fiction.


But they most certainly should NOT view the O'Neill Cylinder as the entry
level orbital hab (though Zubrin, in trying to bias the argument, may
frequently pretend to think this is the case). An O'Neill Cylinder might
mass 1 billion tons. A Stanford Torus would mass 10 million tons, a Bernal
Sphere would come in at under 4 million tons, and a simple Space
Manufacturing Facility (even one with a rotating, radiation-shielded section
for housing) would mass much less still.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn


  #245  
Old October 19th 07, 06:58 PM posted to rec.arts.sf.science,sci.space.history
Mike Combs[_1_]
external usenet poster
 
Posts: 401
Default Questions about "The High Frontier"

"Hop David" wrote in message
...
Pat Flannery wrote:

We don't know what gravity's needed to stay healthy.


A question which the centrifuge module on the ISS might have answered, so
of course we canceled that.


ISTR that a centrifuge module would cost nearly as much as the ISS itself.


I think Pat was refering to a small centrifuge (fitting inside a work area)
which might have been good for white-mice type experiments.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn


  #246  
Old October 19th 07, 07:10 PM posted to rec.arts.sf.science,sci.space.history
Mike Combs[_1_]
external usenet poster
 
Posts: 401
Default Questions about "The High Frontier"

"John Schilling" wrote in message
...

But it's probably going to be a *lot* less expensive if you allow for
the inhabitants to build, provision, and resupply their habitat using
local resources.


And there's every reason in the world to expect an asteroidal settlement to
be doing this.

And Mars has a much broader range of useful resources
than any NEO. Than all NEOs combined, probably.


I'm not sure why you would say this. What resources would be available on
the surface of Mars that you couldn't find in a well-selected CC-type
asteroid?

Mars also has gravity, which is quite useful if you want your inhabitants
to remain, like, alive and stuff. Providing gravity on or near an NEO is
rather hard, especially at small scales.


I wouldn't so much say "hard" as "requiring a certain minimal scale". If
one has two counter-rotating structures of equal mass, nothing is required
to spin them up and keep them spinning other than an electric motor between
them.

On the other hand, 1/3 G may turn out to be too little gravity to remain
healthy. If so, a rotating structure in close orbit of an asteroid could
provide a full 1-G.

Right, so, settling Greenland is likely to be less expensive for
hypothetical European explorers than settling North America or the
Carribean?


I think you would find the magnitude of the relative energy differences to
be very large.


--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn


  #247  
Old October 20th 07, 06:49 AM posted to rec.arts.sf.science,sci.space.history
Hop David
external usenet poster
 
Posts: 656
Default Questions about "The High Frontier"

John Schilling wrote:
On Wed, 17 Oct 2007 11:56:44 -0700, Hop David wrote:


Quadibloc wrote:

Mike Combs wrote:


We won't build orbital habitats because someone has forbidden the moon or
Mars. We'll build orbital habitats because there are significant advantages
to them over same-scale habitats built on either the moon or Mars. People
who insist on living on other planetary bodies will find themselves unable
to economically compete with those located in free orbit.



Yes, asteroids are good sources of mineral resources, and not being in
a gravity well is an advantage.



I think, though, that the Moon and Mars still have a place, because
start-up costs are going to be way lower.



I agree moon habs will have lower start up costs. But why would Martian
habs be less expensive than NEO based habs? There are NEOs that can be
reached with less delta vee than Mars and with launch windows of
comparable frequency.



That's fine if all you're planning to do is send prefabricated habs by
rocket from Earth, with periodic resupply shipments.

But it's probably going to be a *lot* less expensive if you allow for
the inhabitants to build, provision, and resupply their habitat using
local resources. And Mars has a much broader range of useful resources
than any NEO. Than all NEOs combined, probably.


http://clowder.net/hop/railroad/asteroidresources.html


Mars also has gravity, which is quite useful if you want your inhabitants
to remain, like, alive and stuff.


Is Mars gravity sufficient to maintain health? Moon gravity? This is an
open question so far as I know.


Providing gravity on or near an NEO is
rather hard, especially at small scales.


If Lunar gravity is sufficient, that substantially changes the mission
requirements and constraints. Nyrath has said recent research suggests
workers can tolerate higher angular velocity if they're gradually
acclimated. If this is true that also reduces the mission requirements.

The difficulty of providing sufficient gravity at small scales is still
unknown.




Here's a graphic I made showing relative delta vee distances for
assorted "low hanging fruit":
http://clowder.net/hop/railroad/deltaveemap.html



Right, so, settling Greenland is likely to be less expensive for
hypothetical European explorers than settling North America or the
Carribean?


See the asteroid resources page I gave above. When you demonstrate the
relative poverty of NEOs vs Mars, I'll buy the Greenland vs North
America analogy.

Myself, I'd like the the Moon, NEOS _and_ Mars-Deimos-Phobos developed.

Hop
  #248  
Old October 20th 07, 10:15 AM posted to rec.arts.sf.science,sci.space.history
Pat Flannery
external usenet poster
 
Posts: 18,465
Default Questions about "The High Frontier"



Mike Combs wrote:.

I think Pat was refering to a small centrifuge (fitting inside a work area)
which might have been good for white-mice type experiments.


This thing: http://en.wikipedia.org/wiki/Centrif...dations_Module

Pat
  #249  
Old October 20th 07, 05:12 PM posted to rec.arts.sf.science,sci.space.history
Hop David
external usenet poster
 
Posts: 656
Default Questions about "The High Frontier"

Mike Combs wrote:

"Troy" wrote in message
oups.com...

Try telling that to politicians and hysterical anti-asteroid campaign
groups!



I'd have to allow that public education would be a hurtle to overcome.
Similarly, I think SBSP is the best long-term energy solution (and might
lead to space settlement), but that will require extensive public education
that no, there's no cause for concern from the microwave beams.

I think what we might call "Deep Impact hysteria" might rule out aerobraking
asteroids through Earth's atmosphere, but I would hope we won't be prevented
from depositing a fragment of an asteroid perhaps the size of an apartment
building into either L-4 or L-5.


It's desirable to have a near earth perigee not only for aerobraking but
to exploit the Oberth effect.

I don't think hysteria is the right word. Large payloads would be harder
to control and a tiny error could change aerobraking to lithobraking. I
would call it "Deep Impact sensible fear". Again, I advocate payload
mass ceilings well below Tunguska size.

Given plausible methods of delivering payloads, we won't be bumping into
that ceiling for some time to come anyway.


Isn't there a big fight between the L5 crowd and the Zubrinites?



Yeah, and I find it significant that we L5'ers tend to emphasize things like
servable markets, exports, balance of trade, and return on investment, while
the Zubrinites say things like "those who colonize Mars will go for hope,
not for cash". But I think they say that because they have to.


You'll probably wind up with both.



Yeah. I've decided it would be wrongfully dogmatic for me to say that Mars
will never be settled by anybody. Some will do it out of nothing other than
a stubborn love of the planet.


I believe colonization of Mars will come as naturally from the
development of Phobos and Deimos. The Martian moon colonies will
probably need resources that are more easily supplied by Mars than other
sources. The inhabitants of the Martian moons will want to explore and
enjoy their neighbor.

Phobos and Deimos enjoy substantial advantages over most other small
objects. Their proximity to Mars reduces the delta vee budget -
aerobraking and the Oberth effect can be used.

There's a nice launch window to Phobos and Deimos every 2+ years.

Given an eccentric elliptic orbit (as most NEOs have), a nice, low delta
vee Hohmann transfer launch window only opens up when the NEO has a near
earth perihelion. If the NEO's orbital period isn't resonant with the
earth, such launch windows will occur very rarely.

Some examples: Given an asteroid with a 3/2 year period, it's possible
to have a near earth perihelion every 3 years. An asteroid with a 5/4
year period can have a near earth perihelion every 5 years.

Given an earth resonant asteroid with periodic near earth perihelions,
high delta vee but very short duration sprint trajectories between the
earth and the asteroid are also possible.

http://clowder.net/hop/railroad/HohmSprin.jpg

These considerations make earth resonant asteroids much more amenable to
human bases, in my opinion.

But, sadly, resonant NEOs with near earth perihelions are a small
fraction of the total population.

Non resonant asteroids may be exploited by one shot missions (possibly
Kuck mosquitos) but they don't lend themselves to human settlement.

So, after the Moon and the Earth-Moon Lagrange points, Phobos and Deimos
hold spots near the top of my list.

Hop


  #250  
Old October 20th 07, 06:40 PM posted to rec.arts.sf.science,sci.space.history
Damien Valentine
external usenet poster
 
Posts: 273
Default Questions about "The High Frontier"

On Oct 19, 10:52 am, "Mike Combs"
wrote:

But they most certainly should NOT view the O'Neill Cylinder as the entry
level orbital hab (though Zubrin, in trying to bias the argument, may
frequently pretend to think this is the case). An O'Neill Cylinder might
mass 1 billion tons. A Stanford Torus would mass 10 million tons, a Bernal
Sphere would come in at under 4 million tons, and a simple Space
Manufacturing Facility (even one with a rotating, radiation-shielded section
for housing) would mass much less still.


OK. Then why bother with the O'Neill Cylinder? Or, for that matter,
the Stanford Torus or the Bernal Sphere? If they all produce the same
product (whatever that product may be), and the Space Manufacturing
Facility is orders of magnitude cheaper, then there's no point in
building million-plus-ton behemoths in space.

 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
The "experts" strike again... :) :) :) "Direct" version of my "open Service Module" on NSF gaetanomarano Policy 0 August 17th 07 02:19 PM
Great News! Boulder High School CWA "panelists" could be infor it! Starlord Amateur Astronomy 0 June 2nd 07 09:43 PM
"VideO Madness" "Pulp FictiOn!!!," ...., and "Kill Bill!!!..." Colonel Jake TM Misc 0 August 26th 06 09:24 PM
why no true high resolution systems for "jetstream" seeing? Frank Johnson Amateur Astronomy 11 January 9th 06 06:21 PM


All times are GMT +1. The time now is 03:01 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 SpaceBanter.com.
The comments are property of their posters.