response 1 of 54:

Jul 18 00:03 UTC 1997

It sort of annoys me how lots of commentators, especially James
Van Allen, point to Mars Pathfinder as "proof" that people are
superfluous in space and only robots ought to go.
 
Consider the truly pathetic aggregate performance of the last
several Mars probes.  All but this one failed quite spectacularly
and suddenly and returned no data at all.
 
Now look at Pathfinder/Sojourner.  Pathfinder is rooted to one
spot on the planet.  True, it is an interesting spot, bearing
rocks washed from very different places and showing much about
Mars we didn't know... but it is *one* spot.  It can't move
under its own power to look at anything else.  It can't go to
examine the places where these rocks originated, and it could
never have landed in a great many places where the history of
Mars is revealed in greater detail.
 
Now look at Sojourner.  Much has been made of its ability to
move up to rocks and get some data about their composition.  But
really, is this anything to crow about?  It takes all day to get
an aggregate chemical composition on *one* rock.  One geologist 
would take a camera and a rock hammer and have samples of literally
dozens of specimens inside of an hour, and be able to tell far more
about crystal types just by looking.  Sojourner can't go any
farther than about 1600 feet from Pathfinder.  A man in a suit
can stroll 1600 feet in about 10 minutes; they moved quite a bit
faster than that on the Moon.
 
Pathfinder has to be recognized for what it is:  a very timid
first (okay, second) step on the Martian surface.  Yes, it's nice
to have something there, but really... we had the hardware, and
could have sent people there 20 years ago.  If we took advantage
of what we've learned since then, we could do it for relatively
little today.  When are we finally going to go?
 
If you have WWW access, look at the Mars Direct home page.

response 3 of 54:

Jul 19 01:28 UTC 1997

How many members of the robots-only crowd think that humans are needed on the
planet Earth?  

response 5 of 54:

Jul 23 05:47 UTC 1997

s/last/least/

response 7 of 54:

Jul 25 10:32 UTC 1997

Re #4:  There is an *amazing* amount of stuff which can be done in
space, far cheaper than we're doing it now.  Mars Direct is a full-blown
exploration and colonization program which could be done for something
less than what we're spending to maintain an aging fleet of Shuttles,
according to Bob Zubrin.  Look up that URL for the figures, I'm not
willing to go out on a limb and trust my memory on this one.
 
Delta Clipper is one way that we could have done our space program
much cheaper.  However, NASA has sunk the Clipper, first destroying
the sub-scale test vehicle during a flight test (disconnected landing
gear release lines, oversight or sabotage?  You decide) and then
pushing a vehicle concept with a *lower* payload potential, higher
development costs and a much more drawn-out schedule.  (Guess where
the money is?  R&D and Shuttle operations.)
 
Another example of "better, faster, cheaper" was the proposal brought
forth by LLNL a few years ago for an inflatable space station aimed
at support of life-sciences and exploration work.  It would have cost
about a billion bucks from the word go to the whole enchilada on-orbit,
inflated and *spinning* for artificial gravity, including two (if memory
serves) ground test articles.  The whole shebang would have launched on
one Titan V.  Modules could have served on the Moon or Mars.
 
(LLNL used some of their discretionary research funds to come up with this
revolutionary cost-saving concept.  The reaction of Congress was to take
away such discretionary funding.  Apparently, it gored someone's ox.)
 
So, I think there are many ways we could be doing things cheaper and
faster in space.  Unfortunately, pork at home and keeping Russian rocket
scientists employed doing space shots overseas (instead of making missiles
for Iran) are the driving forces behind our spending priorities.

response 9 of 54:

Jul 28 02:20 UTC 1997

The Mars Direct site is indeed http://www.magick.net/mars.
 
I've just stumbled across some other net.resources on Mars.  (All this
stuff on American things, from a British magazine, "New Scientist".  I
recommend this publication *very* highly.  However, it is very expensive
at $140/year.  They are having a half-price sale right now, though.)
 
http://nssdc.gsfc.nasa/gov/planetary/viking.html    Viking landers
http://cmex-www.arc.nasa.gov/                               General Mars
info

And for some of NASA's ideas of what a manned Mars mission would look like,
 
http://www-wn.jsc.nasa.gov/explore/DATA/MImages/MImages.htm
 
The 6/28/1997 issue of "New Scientist" covers some of the concepts for
manufacturing fuel for Mars missions.  It doesn't cover the original
Mars Direct idea very well, though, so read the WWW stuff for more detail.
 
<><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
 
Zubrin's basic idea (and the cornerstone of Mars Direct) is to avoid
having to ship the fuel for the return trip on the outbound leg.  One
really expensive part of a mission is launching it.  The less weight
that has to be launched, the cheaper the mission.  The fuel required
to return a vehicle to Earth from Mars is several times the mass of
the vehicle itself (how much depends on the fuel).  Eliminating the
return fuel from the mass to be launched cuts mission cost dramatically.
 
Zubrin noted something very important:  Mars has an atmosphere which is
composed largely of carbon and oxygen, which are two major constituents
of many rocket fuel compositions.  Hydrogen is in short supply in what
passes for air on the red planet, but it is also the lightest element
and costs relatively little to launch.  So, with the Martian atmosphere
and some hydrogen and energy, you can make rocket fuel on-site.
 
I'll give people a chance to read the Mars Direct stuff themselves before 
going much further with this.

response 11 of 54:

Jul 30 05:01 UTC 1997

The Mars atmosphere has lots of carbon dioxide - not free carbon and free
oxygen (just to keep the facts clear). Carbon dioxide makes great - burnt
fuel. The trouble with Mars is, no signs of reducing agents, such as free
carbon. I agree that the most economical reducing agent to send to Mars is
hydrogen - but then, you need an oxidizing agent too. There isn't much of
that on Mars either. Oxygen is mostly locked up in carbon dioxide or
iron oxides, which makes it pretty unavailable. What fuel mixture is being
proposed to be made on Mars?

response 13 of 54:

Jul 31 07:11 UTC 1997

Getting oxygen from CO2 is pretty difficult. However with H2 and CO2 (and
energy) you can make H2O, which you can electrolyze to recover your H2 and
make O2. Hmmm... H2 + CO2 = H20 + CO. Reject the CO and split the water
as H2O = H2 + 0.5O2. OK. In principle....except for inefficiencies.

response 15 of 54:

Jul 31 23:04 UTC 1997

Re# 13:  Your scheme falls within the +/- details of my knowledge of the
plan.  Similarly, dry ice is a poor form of CO2 for the next step, etc.

Both gravity and wind loads are much lower on Mars.  Even if the atmosphere
is calm as usual (little dust), the solar flux will be poor due to the 
greater distance from the sun.  (Yea, SPF of your skin lotion ain't so
important when you're wearing a space suit.)  Given the problems (night,
unpredictable dust storms, etc.) with solar, I'd rather take a RELIABLE
(preferably no moving parts, etc.) nuclear power source if it was my 
return ticket on the line.  I'd also be inclined to look real seriously
at an ion drive for the interplanetary legs.

response 17 of 54:

Aug 1 18:28 UTC 1997

I've been following the Pathfinder mission on
http://mpfwww.jpl.nasa.gov/default1.html
which I haven't seen mentioned here yet. All of the scientific mineralogical
data, and tentative interpretations, are available there. All of the images
are also. They have also put together a Quicktime VR movie, by which you
can scan 360 degrees around the lander at the speed you wish.

Twin Peaks is about 0.86 km away, and 90 degrees counter clockwise
from that, at a distance of 2 km, is a 1 km diameter impact crater
that looks quite fresh. I would think that a lot of rocks found at
the lander site are ejecta from that crater. The tilt of the rocks, which
in some places has been identified as due to water flow, is also
consistent with having been blown out of the crater. 

I have looked at the Zubin site, and scanned the fuel production proposal.
It is feasible (and was feasible even before they spent $47,000 to run
a demo). It does require transporting H2 from earth, and they propose to
synthesize methane (CH4) as fuel, from the H2 and CO2. It was not stated
in the fuel synthesis document why they want to make methane: H2 itself
if a fine fuel, and converting it to methane would seem to be an unncessary
step (especially considering all the additional equipment required, which
has to be transported to Mars. 

response 19 of 54:

Aug 2 05:04 UTC 1997

What you wrote is the overall result of the use of the Sabatier reaction,
CO2 + 4H2 = CH4 + 2H2O followed (electrolytically) 2H2O = 2H2 + O2. 
However the mix they get of their fuel mixture of CH4/O2 =1, does not
provide complete combustion. They would have to discard CH4. Is that what
you meant? 

Since the plan is to *take* loads of hydrogen to Mars, they are not going
to get any additional specific impulse from converting that to CH4. In
fact, they have to take with them enough H2 to get back *and* enough to
make oxygen. Therefore the most economic way to make oxygen is the key.
The reaction H2 + CO2 = H2O + CO --> 1/2 O2 is just as good as the methane
route (1/2 O2 per H2) and, as you said, they would not have to throw away
H2 in excess CH4, or carry the equipment to make and store CH4. (The
higher boiling point of CH4 can't be important as they would already have
the H2 technology with them.)

response 21 of 54:

Aug 3 01:54 UTC 1997

Re #18:  The higher boiling point of CH4 is essential, because
ultra-cryogens like LH2 cannot be stored for long without active
cooling and heavy insulation.  In space, vacuum and shade make it
reasonably easy to hold hydrogen for a while.  In an atmosphere....
 
Oxygen can be made from CO2 using either thermal cracking with
zirconia cells to separate the oxygen, or the reverse-water-gas-shift
reaction and electrolysis (CO2 + H2 -> CO + H2O, H2O + e -> H2 + 1/2 O2).
All hydrogen converted to water during fuel synthesis is at least
potentially recyclable.

response 23 of 54:

Aug 3 05:14 UTC 1997

Are those ratios in mass units? If so - why would you want to run below
stoichiometric O2? You are using H2 as a diluent, reducing the temperature
and velocity. Note the improved performance as you approach
stoichiometric. 

You cannot split CO2 to produce O2, except by the laborious chemical paths
being discussed. Assuming O2 can be made without consuming H2 is not
realistic. The problem remains that producing CH4 does not also yield
enough O2 to burn it completely, and in addition produces only 1 O2 per 4
H2 consumed. The reaction in #19 (which is the water gas shift)  requires
only 2 H2 per O2 produced - assuming 100% efficiencies in either case, of
course. 

I acknowledge that storing H2 is a little more difficult than storing CH4.
However you still have to store all the H2 you took with you, until you
can convert it to CH4, which will not be fast, during which time you have
to store both. 

My impression is that Zubrin (nor anyone else) has done all the tradeoffs
properly. Their "demonstration" of producing CH4 from H2 was such a
ham-fisted operation (I do give them credit for admitting their stupid
mistakes). Is the whole proposed chemical scenario avialable somewhere on
the web?

CO is not a good fuel (and does not burn "very hot", compared to H2 or
CH4).

All in all, my initial impression is that both components for a return
flight need to be taken, at least for early trips and until colonization
and Martian industry is established.