# 16376 byvictoriatangoman on Feb. 21, 2002, 1:13 a.m.
Member since 2022-08-22
Ok. Here's the scenario. Early in the lunar facility development,
we're creating a lot of oxygen as a by-product of steel making.
vapor disposition we create a big tank and attach it to a framework
with an engine attached. We attach the oxygen tank as well. The
power source is a solar powered ion engine using the low ISP oxygen
as the propellent.
This vehicle makes its way to a NEA. Once there is starts melting
ice by using the solar array that powered the engine and storing the
water in the tank. Once full, the tanker electrolysizes the water to
extract the oxygen for the ion engine.
Is it possible to pump the hydrogen gas back into the water tank? Is
there a limit to how much hydrogen can co-exist with the water?
I know we could use the hydrogen for the engine, but I'm assuming
the engine is optimized for oxygen, I'm assuming the hydrogen is
more useful in LEO or on the moon, where it can be combined with the
Lunar oxygen by-product.
So, what's wrong with this scenario? I also know I could be using
nuclear power or solar sails, but for now I'm concerned with the
technical flaws of what I've proposed.
Anyone care to point out the flaws?
# 16377 bySirch Namdig on Feb. 21, 2002, 9:15 a.m.
Member since 2022-08-22
I feel I have to challenge your basic assumption. Maybe it's
irrelevant. Maybe not.
> we're creating a lot of oxygen as a by-product of steel making.
> So, what's wrong with this scenario?
It seems like it would be like this:
"Early in the lunar facility development, we're creating a lot of
steel (slag? iron?) as a by-product of oxygen extracting".
I dunno, somehow this makes more sense to me "Early in the
development"
Chris.
# 16378 byHuebner, Jay on Feb. 21, 2002, 9:24 a.m.
Member since 2022-08-22
RE: " ... creating a lot of oxygen as a by-product of steel making...."
Iron meteors have hit the Moon over the eons and scattered their bits over
the surface, as they have on Earth. Since the Moon has no atmosphere or
photosynthesis (which make the Earth's atmosphere aerobic, and oxidized the
surface iron) there is lots of reduced iron in the regolith. All one has to
do to pick up "Meteorite Stainless" is to drag a magnet across the Moon's
surface. If you want oxygen as a by-product, go after some element which
has been oxidized, like silicon or aluminum.
Sincerely, Jay Huebner
# 16379 byvictoriatangoman on Feb. 21, 2002, 9:48 a.m.
Member since 2022-08-22
First off, I think you guys have missed my point. It had to do with
the chemistry of storing the hydrogen in the water tank. Would that
pose any problems?
Thirdly, the primacy of steelmaking would come before oxygen
extraction in the buildup of a lunar manufacturing facility with the
critical path and economic feasibility study I'm performing, so I
didn't mis-state the order when I made the post. But, I do agree
that the conventional wisdom is that oxygen is the first material to
go for and the minerals would be the by-product.
The initial equipment to land on the moon would include a solar
furnace designed for the more exacting task of making steel. To
extract oxygen would require a less sophisticated physical plant.
So, from my perspective the more complicated plant is designed for
the steel and thus the oxygen is the by-product. Just splitting
hairs here. We've all got different visions of how to go about this.
> RE: " ... creating a lot of oxygen as a by-product of steel
making...."
> Iron meteors have hit the Moon over the eons and scattered their
bits over
> the surface, as they have on Earth. Since the Moon has no
atmosphere or
> photosynthesis (which make the Earth's atmosphere aerobic, and
oxidized the
> surface iron) there is lots of reduced iron in the regolith. All
one has to
> do to pick up "Meteorite Stainless" is to drag a magnet across the
Moon's
> surface. If you want oxygen as a by-product, go after some
element which
# 16380 bycharles radley on Feb. 21, 2002, 9:57 a.m.
Member since 2022-08-22
> Is it possible to pump the hydrogen gas back into the water tank? Is
> there a limit to how much hydrogen can co-exist with the water?
>
period.
It really makes no difference how much H2 you try to pump in, it will
rapidly leak out through the seals.
If you try to store it in gaseous form you will need to raise it to a
high pressure, it therwise occupies many times more volume than the
water from which it was produced. At higher pressure the leak rate
increases.
You can try to store it as a liquid, but that requires very low
cryogenic temperaeutres and you will not be able to sustain it that way,
it will boil off rapidly, then leak out through the seals.
Fortunately the quantity of hydrogen liberated by electrolyusing the
water si relatively small. The cheapest solution would be to simply
vent it off into space. The amount of hydrogen you lose will be only a
relatively small percentage of the overall payload mass.
However, if the value of the hydrogen is high enough it might be worth
trying to combine it with N2 to make Ammonia, or Carboin to make
methane. That way it will be alot easier to store. Maybe you can
extract the N2 or C from the asteroid itself.
# 16381 byvictoriatangoman on Feb. 21, 2002, 12:21 p.m.
Member since 2022-08-22
>
> > Is it possible to pump the hydrogen gas back into the water
tank? Is
> > there a limit to how much hydrogen can co-exist with the water?
> >
> It is impossible to store pure hydrogen for more than a few days,
> period.
>
> It really makes no difference how much H2 you try to pump in, it
will
> rapidly leak out through the seals.
>
> If you try to store it in gaseous form you will need to raise it
to a
> high pressure, it therwise occupies many times more volume than the
> water from which it was produced. At higher pressure the leak
rate
> increases.
>
Ok, this is what I'm curious about. If the gas is pumped back into
the tank with the millions of liters of water (ice) and we start
increasing the pressure, what effect takes place. Here's a thought.
What if the seal is under water, so the hydrogen is pumped into the
tank and directly into the water. Eventually it'll separate, but
won't the water act as a barrier or seal to prevent the gas from
leaking. Also, what happens to the whole system (water/ice/gas as
the pressure of the hydrogen starts to increase?
> You can try to store it as a liquid, but that requires very low
> cryogenic temperaeutres and you will not be able to sustain it
that way,
> it will boil off rapidly, then leak out through the seals.
I'd prefer to steer clear of a cryogenic solution. Adds more
complexity to the system.
>
> Fortunately the quantity of hydrogen liberated by electrolyusing
the
> water si relatively small. The cheapest solution would be to
simply
> vent it off into space. The amount of hydrogen you lose will be
only a
> relatively small percentage of the overall payload mass.
True, but I haven't gotten around to the rocket equation yet and I
haven't finalized the volume and mass of the system. So I don't
really know yet how much water would have to be split in order to
ferry this package back home to luna/LEO
>
> However, if the value of the hydrogen is high enough it might be
worth
> trying to combine it with N2 to make Ammonia, or Carboin to make
> methane. That way it will be alot easier to store. Maybe you
can
> extract the N2 or C from the asteroid itself.
Thanks for introducing this complication. I haven't thought this
completely through yet. Where to store the N2 and other gases. I was
going to look up data for how common an occurance, and how
pure "Snowball" NEO are. Can they be pure ice? I don't know. I
suspect that you comment may be closer to the truth, and it would be
a dirty "snowball"
So, what would be the simplest way to extract water and the other
gases? Could one furnace do the trick? Could one storage tank do the
trick?
# 16382 bycharles radley on Feb. 21, 2002, 1:34 p.m.
Member since 2022-08-22
> --- In ssi_list@... charles radley
> > It really makes no difference how much H2 you try
> to pump in, it
> will
> > rapidly leak out through the seals.
>
> Is that always the case. No matter how well
> engineered the seals?
>
Hydrogen can diffuse through just about anything,
inlcuding some metals.
As far as I know, nothing has even been invented which
meets your requirements.
> >
> Ok, this is what I'm curious about. If the gas is
> pumped back into
> the tank with the millions of liters of water (ice)
> and we start
> increasing the pressure, what effect takes place.
The diffusion rate of the hydrogen will increase. I
do
not know the numbers, sorry.
> Here's a thought.
> What if the seal is under water, so the hydrogen is
> pumped into the
> tank and directly into the water. Eventually it'll
> separate, but
> won't the water act as a barrier or seal to prevent
> the gas from
I believe hydrogen can diffuse through water quite
rapidly. It would not be an effective barrier.
> leaking. Also, what happens to the whole system
> (water/ice/gas as
> the pressure of the hydrogen starts to increase?
>
For the third time, the rate of hydrogen
diffusion/leakage will increase.
It will also tend increase its reactivity with
anything it is in contact with, e.g. hydrogen
embrittlement of ferrous metals will accelerate.
>
> I'd prefer to steer clear of a cryogenic solution.
> Adds more
> complexity to the system.
> >
Quite true.
>
> True, but I haven't gotten around to the rocket
> equation yet and I
Well, it is central to the propulsion concept.
You really need to take a look at that before
designing
overly complex hydrogen storage systems which probably
will have little value.
> haven't finalized the volume and mass of the system.
> So I don't
> really know yet how much water would have to be
> split in order to
> ferry this package back home to luna/LEO
> >
That is the first thing you need to calculate.
Cheers,
Charles R.
# 16383 byvictoriatangoman on Feb. 21, 2002, 6:29 p.m.
Member since 2022-08-22
>
> > Is it possible to pump the hydrogen gas back into the water
tank? Is
> > there a limit to how much hydrogen can co-exist with the water?
> >
> It is impossible to store pure hydrogen for more than a few days,
> period.
>
> It really makes no difference how much H2 you try to pump in, it
will
> rapidly leak out through the seals.
>
> If you try to store it in gaseous form you will need to raise it
to a
> high pressure, it therwise occupies many times more volume than the
> water from which it was produced. At higher pressure the leak
rate
> increases.
>
Ok, this is what I'm curious about. If the gas is pumped back into
the tank with the millions of liters of water (ice) and we start
increasing the pressure, what effect takes place. Here's a thought.
What if the seal is under water, so the hydrogen is pumped into the
tank and directly into the water. Eventually it'll separate, but
won't the water act as a barrier or seal to prevent the gas from
leaking. Also, what happens to the whole system (water/ice/gas as
the pressure of the hydrogen starts to increase?
> You can try to store it as a liquid, but that requires very low
> cryogenic temperaeutres and you will not be able to sustain it
that way,
> it will boil off rapidly, then leak out through the seals.
I'd prefer to steer clear of a cryogenic solution. Adds more
complexity to the system.
>
> Fortunately the quantity of hydrogen liberated by electrolyusing
the
> water si relatively small. The cheapest solution would be to
simply
> vent it off into space. The amount of hydrogen you lose will be
only a
> relatively small percentage of the overall payload mass.
True, but I haven't gotten around to the rocket equation yet and I
haven't finalized the volume and mass of the system. So I don't
really know yet how much water would have to be split in order to
ferry this package back home to luna/LEO
>
> However, if the value of the hydrogen is high enough it might be
worth
> trying to combine it with N2 to make Ammonia, or Carboin to make
> methane. That way it will be alot easier to store. Maybe you
can
> extract the N2 or C from the asteroid itself.
Thanks for introducing this complication. I haven't thought this
completely through yet. Where to store the N2 and other gases. I was
going to look up data for how common an occurance, and how
pure "Snowball" NEO are. Can they be pure ice? I don't know. I
suspect that you comment may be closer to the truth, and it would be
a dirty "snowball"
So, what would be the simplest way to extract water and the other
gases? Could one furnace do the trick? Could one storage tank do the
trick?
# 16384 byArthur Smith on Feb. 22, 2002, 10:05 a.m.
Member since 2022-08-22
Uh, it's not that hard to store hydrogen...
-- the best way to do it is as a metal hydride. Sure it leaks
into the metal, but it also stays there in relatively high
density if you coat the thing with plastic (hydrogen doesn't diffuse
very
well through plastics or ceramics). Ever used a NiMH battery???
Arthur
>
> > --- In ssi_list@... charles radley
> > > It really makes no difference how much H2 you try
> > to pump in, it
> > will
> > > rapidly leak out through the seals.
> >
> > Is that always the case. No matter how well
> > engineered the seals?
> >
> It is not a matter of engineering.
> Hydrogen can diffuse through just about anything,
> inlcuding some metals.
> As far as I know, nothing has even been invented which
> meets your requirements.
>
> > Ok, this is what I'm curious about. If the gas is
> > pumped back into
> > the tank with the millions of liters of water (ice)
> > and we start
> > increasing the pressure, what effect takes place.
>
> The diffusion rate of the hydrogen will increase. I
> do
> not know the numbers, sorry.
>
> > Here's a thought.
> > What if the seal is under water, so the hydrogen is
> > pumped into the
> > tank and directly into the water. Eventually it'll
> > separate, but
> > won't the water act as a barrier or seal to prevent
> > the gas from
>
> I believe hydrogen can diffuse through water quite
> rapidly. It would not be an effective barrier.
>
> > leaking. Also, what happens to the whole system
> > (water/ice/gas as
> > the pressure of the hydrogen starts to increase?
> >
> For the third time, the rate of hydrogen
> diffusion/leakage will increase.
>
> It will also tend increase its reactivity with
> anything it is in contact with, e.g. hydrogen
> embrittlement of ferrous metals will accelerate.
>
> > I'd prefer to steer clear of a cryogenic solution.
> > Adds more
> > complexity to the system.
> > >
> Quite true.
>
> > True, but I haven't gotten around to the rocket
> > equation yet and I
>
> Well, it is central to the propulsion concept.
> You really need to take a look at that before
> designing
> overly complex hydrogen storage systems which probably
> will have little value.
>
> > haven't finalized the volume and mass of the system.
> > So I don't
> > really know yet how much water would have to be
> > split in order to
> > ferry this package back home to luna/LEO
> > >
> That is the first thing you need to calculate.
>
> Cheers,
>
> Charles R.
>
Arthur P. Smith email: apsmith@...
Manager, Database Group The American Physical Society
1 Research Rd. Box 9000, Ridge, NY 11961-9000 phone: +1-631-591-4072
# 16385 bycharles radley on Feb. 22, 2002, 11:34 a.m.
Member since 2022-08-22
Arthus,
space.
The weight of the metal is orders of magnitude greater
than the mass of hydrogen being stored.
In space operations, payload mass fraction is
everything.
The best metal hydride in the link you gave is MgH2
which is 92.4 % Mg by weight, a terribly inefficient
system, not useful at all for spacecraft applications.
It means you would have to haul 92.4 kilograms of Mg
for every 7.6 kilograms of Hydrogen you wish to store.
Like I said before, it would be a lot cheaper simply
to vent the hydrogen to space.
> Uh, it's not that hard to store hydrogen...
>
> http://www.csa.com/hottopics/hydrogen/overview.html
>
> density if you coat the thing with plastic (hydrogen
> doesn't diffuse
> very
> well through plastics or ceramics). Ever used a NiMH
> battery???
>
That is true for minimal pressure differential,
airships used to hold large volumes of hydrogen for
weeks and months.
At higher pressures containment gets much more
difficult.
Cheers,
Charles R.
# 16386 byArthur Smith on Feb. 22, 2002, 1:37 p.m.
Member since 2022-08-22
> The best metal hydride in the link you gave is MgH2
> which is 92.4 % Mg by weight, a terribly inefficient
> system, not useful at all for spacecraft applications.
Any of your other chemical combinations would also require
transportation of a large quantity of extra stuff: methane would be 75%
carbon by weight, ammonia 82% nitrogen, water 89% oxygen and each of
those as gases or liquids would require significantly stronger
containment than a metal-hydride.
Anyway, the point was hydrogen really isn't that hard to store. For
transport yes you'd probably save net energy by chemically converting it
to something else and then converting it back at the destination, rather
than transporting as H2 - though cryogenics and liquid H2 would probably
be the most energy-efficient option for intermediate transport
distances.
Or maybe the H2 isn't that valuable and the best option is to just vent
it rather than tie up other materials to store it. It would all depend
on the economics of the situation; hard to judge at this point.
Arthur Smith (apsmith@...
# 16387 byvictoriatangoman on Feb. 22, 2002, 4:07 p.m.
Member since 2022-08-22
> Arthus,
>
> Metal hydrides are a very poor way to store H2 in
> space.
>
> The weight of the metal is orders of magnitude greater
> than the mass of hydrogen being stored.
of this metal, then on the return voyage, the tank is full of water,
the spacecraft draws some water, electrolysizes it, pumps the
hydrogen back into the tank. Sounds easy, but I question I have is
how does the metal combine with the hydrogen. Will it simply absorb
hydrogen that comes in contact with it? Or is machinary required?
# 16388 bycharles radley on Feb. 22, 2002, 6:18 p.m.
Member since 2022-08-22
> --- In ssi_list@... charles radley
> > Arthus,
> >
> > Metal hydrides are a very poor way to store H2 in
> > space.
> >
> > The weight of the metal is orders of magnitude
> greater
> > than the mass of hydrogen being stored.
>
> But the water storage tank must be made of
> something. So make it out
> of this metal, then on the return voyage, the tank
hydride and disintegrate.
Chemical reactions between hydrogen and tank metal are
a tank designers worst nightmare.
You really do not want to do this.
# 16389 byvictoriatangoman on Feb. 22, 2002, 7:03 p.m.
Member since 2022-08-22
Good to know. Cross that scenario off the list.