On Hydrogen Fuel

I am beginning to wonder whether hydrogen is being used to full
advantage in our space program.

Here is my understanding of the aerospace use of LH2.


It is stored in a glass lined slosh baffled tank in it's liquid state
(typical rocket tank). These tanks are vented so that evaporation can
be expelled from the tank thus eliminating pressure build up.

It is extremely cold in the liquid state. Cryogenic and close to
absolute zero.

When chilled even further by inducing increased evaporation by vacuum
or injecting liquid helium which is a colder liquid it reaches what is
called a 'slush' state which is partly hydrogen 'ice' mixed with liquid
hydrogen.

Slush tanks make hydrogen 16% more dense than it's pure liquid state.
It also increases the fuel's ISP somewhat.


Now I have learned that liquid hydrogen is transported, both by rail
and truck, in carbon fiber composite tanks which hold the fuel in a
liquid state without evaporation at 250 atmospheres pressure. This
works out to be a little less than 4000 psi.

Several ideas have come to mind. First, why not use these tanks in
place of the evaporation tanks on rockets? Second, why not build even
stronger tanks and super compress the hydrogen into slush, or even into
a pure solid state?

Titanium tanks can easily take 100,000 psi. Why not use titanium, add
a little helium, take hydrogen to a solid state and use that to fuel
SSMEs (Space shuttle Main Engines)? This would produce 'atomic'
hydrogen with an ISP around 750+, not the ~450 ISP of standard liquid
hydrogen.

The real question is whether or not the SSME can stand up to 'atomic'
hydrogen with it's higher ISP. This, I believe, needs to be tested by
NASA.

A significantly denser hydrogen, perferably solid, combined with a
substantially higher ISP should result in spectacular performance.

Atomic hydrogen is being experimented on by NASA. I wonder, however,
why it's application with real live equipment is taking so long to come
about. It is really just a solid form of the fuel that is currently
being used by hydrogen burning engines. Extra ISP is just extra ISP,
requiring at most some beefing up of the combustion chamber, throat,
bell and maybe the lines running from the tanks to the throat.


I welcome any comments on liquid hydrogen. It seems to me to be the
fuel of the future, not just the 'old' Shuttle.


tomcat

tomcat wrote:
I am beginning to wonder whether hydrogen is being used to full
advantage in our space program.

Here is my understanding of the aerospace use of LH2.


It is stored in a glass lined slosh baffled tank in it's liquid state
(typical rocket tank). These tanks are vented so that evaporation can
be expelled from the tank thus eliminating pressure build up.

Probably has to do with the glass lining, don't you think? If it wasn't
a vacuum seperated bottle in a bottle, then convesctive and conductive
heat gain would be high. The coldness of the LOX would promote thick
frost/ice accumulation on the tank outer surfaces leading to both
aerodynamic drag and ice chunk falling hazards.


It is extremely cold in the liquid state. Cryogenic and close to
absolute zero.

When chilled even further by inducing increased evaporation by vacuum
or injecting liquid helium which is a colder liquid it reaches what is
called a 'slush' state which is partly hydrogen 'ice' mixed with liquid
hydrogen.

Slush tanks make hydrogen 16% more dense than it's pure liquid state.
It also increases the fuel's ISP somewhat.

It increases it due to the fact that a leaner fuel mix is used. Perfect
combustion of H2+O2 to H2O cannot be counted on due to the short
latency time in the combustion chamber. LH2/LOX is burned at a 1:4
ratio instead of 1:8 ratio by mass/weight. With Slush-LH2/LOX the H2 is
birned at a 1:6 ratio, a 50% improved fuel efficiency. The Isp remains
constant as only the reaction of 2H2+O2=2H2O counts. None of the
unburned H2 adds thrust.


Now I have learned that liquid hydrogen is transported, both by rail
and truck, in carbon fiber composite tanks which hold the fuel in a
liquid state without evaporation at 250 atmospheres pressure. This
works out to be a little less than 4000 psi.

Composite tanks for compressed H2 have been approved in Europe for road
vehicle use to 10,000 psi pressure, with 2.35 safety margin, passing
tests to 24,000 psi.

Several ideas have come to mind. First, why not use these tanks in
place of the evaporation tanks on rockets? Second, why not build even
stronger tanks and super compress the hydrogen into slush, or even into
a pure solid state?

Stronger tanks up to 2,000,000 psi are theoretically possible but the
cost is out of this world. A new era of "conformable tanks" is just
dawning, and the testing process is bth time-consuming and costly.

DEsigning high pressure tanks for Hydrogen Economy fuel cell road
vehicles has uncovered a new failure mode never seen before and not
even predicted by prior experience. These tanks can be made to explode
where the tank turns to dust, and it happens so fast that high speed
cameras with 4000 frames per second barely capture the even on one
single frame, although sometimes it happens between frames.

Now you see it, now you don't, in 1/3000th of second.
http://www.eere.energy.gov/hydrogena...eisberg_04.pdf
http://www.eere.energy.gov/hydrogena...fs/30535ar.pdf

They call it "benign" failure because it doesn't throw tank shrapnel,
but you are still left with a ball of Hydrogen rapidly expanding.



Titanium tanks can easily take 100,000 psi. Why not use titanium, add
a little helium, take hydrogen to a solid state and use that to fuel
SSMEs (Space shuttle Main Engines)? This would produce 'atomic'
hydrogen with an ISP around 750+, not the ~450 ISP of standard liquid
hydrogen.

For the same reason they don't use peanut butter: ductility. The reason
we can shape titanium is because of ductility. That's the thing you
want to avoid in high pressure tankage.



The real question is whether or not the SSME can stand up to 'atomic'
hydrogen with it's higher ISP. This, I believe, needs to be tested by
NASA.

Forget SSME. The experimentt is over -- it failed to produce what it
was being tesed for: cheap frequent reusable orbit insertion. Time to
move on. NASA has accepted that decision. Now it's your turn. It's
over.


A significantly denser hydrogen, perferably solid, combined with a
substantially higher ISP should result in spectacular performance.

There's no such thing as "spectacular performance" when it costs, $55m,
$500m or 1.2b per averaged flight. Get over it -- the entire concept
failed to deliver cheap regular frequent orbit. Move on to better
things. This is a cul de sac. Back out and start from where it went
wrong. You can't make progress in this dead end.


Atomic hydrogen is being experimented on by NASA. I wonder, however,
why it's application with real live equipment is taking so long to come
about. It is really just a solid form of the fuel that is currently
being used by hydrogen burning engines. Extra ISP is just extra ISP,
requiring at most some beefing up of the combustion chamber, throat,
bell and maybe the lines running from the tanks to the throat.


I welcome any comments on liquid hydrogen. It seems to me to be the
fuel of the future, not just the 'old' Shuttle.

NASA flew the Helios Prototype to 96,863 feet on 28 horsepower of Solar
Photovotaics-Powered plastic covered wings in 2001. Extend THIS, not
waste your time tweaking the Shuttle.

I predict that the first spaceplane to reach ISS will be a rocket
powered biplane with wings larger than 8,000 feet square. It will look
more like the B2-Spirit carrying the Concorde piggyback than it will
look like the Space Shuttle riding on the 747.

It will take on the bulk of it's oxidizer at 100,000 feet as it sprints
to orbit, and the wingloading will be less than 20 pounds per square
foot at takeoff. Like the Helios Prototype, it will have PV solar cells
on the upper wing surfaces for power during orbit.

It will carry both water and ammonia for return fuel, converted to N2,
O2 and H2 at station. The N2 and some of the O2 will be left at station
each trip for breahable atmosphere for an ever expanding LEO habitat
program, and the H2 and some of the O2 will be used for poiwered
decent. NH3 has 1.7 times the Hydrogen density of LH2. Nine liters H2O
has 1 kilogram of H2 and 8 kilograms of O2 contents, compared to 14
liters for one kilogram of LH2, 1.5 times the Hydrogen density.

It makes more sense to carry breathable air to station in forms
containing fuel values for refueling than to carry compressed air tanks
to station. Because of the long processing times, return fuel would
likely be made at station from previous deliveries, although solar
cells on wings permit staying as long as it takes for return flight
without depending on prepositioned return fuels.

There is a perpetual requirement for air and water deliveries to LEO,
so some launch budget must alway include these payload fractions
anyway. It's going to be a very long time before lunar deliveries of O2
will help supply.


Another option is CH4/LH2 Gelled Hydrogen with metal particles.
http://sbir.grc.nasa.gov/launch/GELLED.htm


The high solar power and long solar "days" of above atmosphere will be
used for making cryogenic gases in orbit for active cooling re-entry.
Return cargos may be returned seperately on their own unpiloted craft
assembled at LEO. This will bring the wingloading down below 5 pounds
per foot square. Oxidizer will be reloaded on return trip same way as
outbound for powered aeronavigation to any convenient chosen landing
port. Such a craft will do double duty as transcontinential air
carrier.

Now, as Jean Luc Picard would say: "Make it so".

Thank-you H2-PV NOW. I am still pondering your post and . . . learning
from it.


While I am doing that let's engage in a little pencil sharpening.

Hydrogen is very interesting and so is oxygen. H20 is, of course,
water. We drink it, bathe in it, and take it completely for granted.

H20 is really a combination of 2H2 + O2 yielding 2H2O. They come
together with an enormous output of energy, hence the hydrogen/oxygen
Shuttle fuel. It takes another large amount of energy to split them
apart but this splitting yields yet more energy than consumed because
no energy is really consumed. It simply continues on until it is
dissipated one way or another.

Automobiles seem to run best in the darkness of early morning because
moisture (dew) enters the engines of our cars and super charges them.
In fact devices called super chargers are built for automobiles. Is it
steam in the cylinders? Hardly.

Jet engines are much the same. A little moisture in the air and
significant increases in power output are manifest. Too much, however,
and the 'candle' goes out. Too much power here to be explained away as
steam expansion.

Not enough, though, to be explained as the splitting or recombining of
water molecules either. Apparently, a few of the molecules do this
while the rest become steam. The energy output is so great that a few
molecules breaking apart and recombining can 'really' make a difference
over old fashioned fossil fuels.

What if we use a simple little terrawatt laser, along with any other
helper device we can think of, and really get the temperature of a
combustion chamber into the magnetic bottle area of several hundred
thousand degrees. Then add water.

If the chamber is designed like a jet with an afterburner we might be
able to achieve an initial splitting of all, or nearly all, of the
water in the first chamber only to have it 'naturally' recombine in the
afterburner. Energy output? Beyond description.

With that much thrust heavy engines, even in the tons, will not matter.
The ratio will dwarf nearly any degree of engine weight. Once
ignited, the reaction should become either self sustaining or nearly
so.

Will additional oxygen be needed? It shouldn't be. After all, the
reaction needs just enough to recombine and that is exactly the ratio
of hydrogen/oxygen you started with -- exactly. Stick some water in
your tanks, light up the lasers, and off you go!

I suspect that thrust figures for hydrogen/oxygen rockets and various
super charged engines reflect that only a tiny amount of water is so
split and recombined. The trick is to split and recombine ALL the
water.


tomcat

Notes, afterthought, and an update:


The concept of 'water fuel' is, admittedly, very speculative. To the
best of my knowledge, it has never been done. It is a theoritical
concept idea that might, just might, result eventually in a radical new
rocket propulsion beyond even NASA's 'atomic hydrogen' experiments.

We are so used to putting fires out with water that, at first, the
concept of 'water fuel' seems absurd. It is not. It is soundly based.
Actually, just one step beyond the LH2/LOX system in use today.

It may appear that I am advocating a hydrogen fusion concept that has
not worked for nuclear fusion power output despite billions of dollars
spent. This, however, is not the case.

What is being presented with the 'water fuel' concept is a molecular
splitting and a molecular fusion of hydrogen and oxygen atoms, not
'atomic fusion'. Molecular splitting is much, much easier to
accomplish than it's atomic cousin. It occurs naturally every time you
light a fire. The combusion of wood, coal, or whatever is the result
of the splitting of molecules and the subsequent release of energy
(fire), and smoke.

What is so hard in the case of 'atomic fusion' should prove much easier
for the 'molecular fusion' of water. It, apparently, is happening on a
tiny scale within supercharged motors and turbines. Increase the heat
by several magnitudes and it should happen on a mega scale releasing
huge amounts of energy.

How huge? Well, if I am not mistaken, the formula reads that a single
double molecule of water (2H2O) releases 572 thousand joules of energy
per double moleucle. Now multiply that by a few hundred trillion
molecules and see what you get! Interested? If I have misread the
energy formula for molecular water fusion please post a note. Frankly,
it sounds almost unbelievable. Heretofore I had though only nuclear
(atomic) fusion could generate energy like this.

Once again, I await your comments.


tomcat

tomcat wrote:
Notes, afterthought, and an update:


The concept of 'water fuel' is, admittedly, very speculative. To the
best of my knowledge, it has never been done. It is a theoritical
concept idea that might, just might, result eventually in a radical new
rocket propulsion beyond even NASA's 'atomic hydrogen' experiments.

I believe I was misunderstood. Water as CARGO is relatively compact and
easily packaged without heavy containers. They sell it in plastic
bottles in stores. It only become fuel after being processed in orbit
into the two parts. 2.4 gallons of water electrolyze into 1 kilogram of
Hydrogen and 8 kilograms of Oxygen. The volume of gases is quite large.
If you know you need fuel for return, taking H2O is the most compact
form, and considerably safer than than carrying around excess flamable
gases before you actually need the gases.

Hydrogen under pressure and liquified still takes 14.12 liters per
kilogram of volume. H2O under no particular pressure only requires 9
liters to hold the same kilogram of Hydrogen. Actually the 9 liters
holds 1 kg H2 and 8 kg of O2, so the gas pressure container mass and
the volume savings are high.

Either the spacecraft or the station requires electrolysis means to
convert the compact water into useful gases. Probably both should be
equipped to do that. The Faraday Disk is ancient technology from the
1850s, over a century and a half old. In 1889 Nikola Tesla patented a
DC dynamo power generator, patent # 406,968 based on Faraday's Disc.

http://www.abdn.ac.uk/~u02rjr4/px2013/Faraday.htm
http://en.wikipedia.org/wiki/Homopolar_generator

Faraday discovered you could generate electricity by rotating a
conductor past a magnet, or vice versa. Tesla discovered you can
generate the same current by rotating both the magnet and the conductor
together. In zero-G without friction you would call such a thing a
gyroscope, but an electical generating gyroscope.

The Homopolar generator illustrated in the wikipedia article link
produced 2 megaamperes of current. At 2 volts that would be 4,000
kilowatts per hour. It takes about 42 kWh to electrolyze 2.4 gallons of
water, so this device could have produced 95 kilograms of H2 per hour
from water cargo for return fuel. (There would also be about 761
kilograms of O2 per hour simultaneously generated.) Carrying the
numbers on forward, 24 hours of power generation would produce 2280
kilograms of H2, a week's production 15,960 kilograms of H2. A month
would make 68,400 kilograms of H2. That's from one homopolar generator
per example given above. The limit is how much water can be carried to
LEO.

The proposed Spaceplane has LH2 and LOX tanks for takeoff. Mostly the
LH2 is required for atmospheric flight because the oxidizer is in the
air being passed through.

See the SKYLON for one version of LH2 air-breathing first-phase of
launch.
http://en.wikipedia.org/wiki/Skylon

The Oxygen weighs 8 times the Hydrogen (actually 4 times for
rich-mixture 4H2+O2 LH2 burning, or 6 times for LH2/Slush mixtures).
You don't want to launch any more O2 or LOX than you really need for
orbit. The LH2 tanks can be smaller by at least 33% if your return H2
is packaged as H2O going up. There's no weight savings but there is
important volume savings, which translates as reduced tankage mass and
ship volume savings. At LEO station you convert the water to fuel for
return trip and refill the now nearly empty LH2 tanks for return
navigation fuel. Again, you only need part of the Oxygen until you get
to the stratosphere and can begin air-breathing again. You can leave
surplus O2 at the space station.

Transporting bulky gases to the spacestation in heavy pressure
containers does not make sense. You can carry blocks of ice instead,
which make their own packages. The ice doesn't slosh around and you can
shrinkwrap it for the brief trip between surface to LEO. No heavy tanks
required -- eliminating any weight is critical for success to add more
cargo mass.

The space station has a real need for air supply. Pure oxygen is
flamable and the Earth's Nitrogen/Oxygen ratio is proven satisfactory
to reduce fire hazards of O2..

Ammonia is another rocket fuel. Liquid ammonia has 1.7 times more
Hydrogen than Liquid Hydrogen does, and it has it at far lower pressure
and far less refrigeration temperatures. Carrying ammonia is one way to
carry return rocket fuel AND transport needed gases to LEO. If you have
to carry nitrogen anyway, for station air, ammonia is liquid at far
higher temperatures than LH2 is, and the pressure is only about 8
atmospheres to keep it liquid.

One catalytically decomposes the NH3 to retrieve the N2 and H2. Such
technology is commonplace, in fact already on the market to fuel
Hydrogen Fuel Cell cars. See the ZAP motors website for links.

http://snipurl.com/mpsb
Results 1 - 100 of about 13,300 for Zap Motors Ammonia Fuel Cell.

So, to go over it once mo
(1) -- Some LH2 required for horizontal airport takeoff. Some LOX
required for initial takeoff.
(2) -- Additional LH2 required for altitude flight around 100,000 feet.
Spaceplane takes on O2 from the air: some is immediately burned, some
is flash-chilled to LOX as SABRE example. Speed is increased to mach
5.5 and air-breating ceases. Speed is further increased and air-launch
to LEO occurs, using stored fuels and oxidizer.
(3) -- At LEO, water and ammonia is processed. N2 and some O2 is left
behind for breathable atmosphere. The H2 and some of the O2 is
liquified for return fuel.
(4) -- Return flight begins. H2 sufficient for entire flight is
onboard. O2 sufficient for navigation down to 100,000 feet is carried.
From 100,000 feet to landing spaceplane becomes air breather again.

There is no expectation that at landing the spaceplane will be empty.
Space manufacturing is the justification for high levels of traffic to
and from orbit. Zero gravity and high quality vacuum have sufficiently
high value in some manufacturing. A spaceplane ought to be able to
carry 80,000 pounds to LEO and land with the same in finished products.
Therefore there is no expectation tha a lightweight landing is assured.

Nothing stated here above or previously implies "fusion" or sci-fi
concepts. Everything is basically off-the-shelf components, except the
SABRE rocket and SKYLON spaceplane.

The expansion program for space habitats would require vast amounts of
breathable air, which is heavy to launch. With enough power water can
be endlessly repurified and recirculated, but large quantities of water
will have to transported as well.

Dreamers dream of rockets with no demands of supplying life's
essentials like water and air, but there's no where to go, and no
reason to go unless these are provided in adequate amounts.

Solving ALL the problems is required, not just solving your favorite
one of them. You have to be sure you can carry air and water and fuel
and power generation and habitat building materials and machinery and
tools and raw materials. Because its a business you have to be able to
keep schedules and bring down the profit-making products safely and
unbroken.

I have no idea what caused you to leap to conclusions about "water
fuel" and fusion etc below, but I have no comments to make on them. My
comments were made above and are relevent to the topic title "Hydrogen
Fuel".

This is not some mysterious subject: all of our cars will be operating
on Hydrogen within a decade, either internal combustion engines or fuel
cells. Just understanding the chemistry and physics of that has
occupied the lifetimes of first class scientists, and after 300 years
of scientific investigation we are nowhere close to the complete
understanding of Hydrogen, let alone Hydrogen and Oxygen as a molecule.
Nobody you know can yet explain why snowflakes make six-sided symmetry,
or why they don't all make the same pattern. Currently there are
several thousand of the world's best engineering minds working hard to
perfect hydrogen storage tanks, improve electrolysis efficiency and
introduce the Hydrogen Economy. These may seem like trivial efforts but
the future of mankind in space and on Earth depends on their successes.

Maybe, if these guys succeed they will buy enough future that others
can eventually invent "water fuel" and fusion power, instead of
scrounging in some Mad Max post-apocalptic hell of the collapse of
society because of climate degradation or peak oil warfare for limited
and dwindling resources.

We are so used to putting fires out with water that, at first, the
concept of 'water fuel' seems absurd. It is not. It is soundly based.
Actually, just one step beyond the LH2/LOX system in use today.

It may appear that I am advocating a hydrogen fusion concept that has
not worked for nuclear fusion power output despite billions of dollars
spent. This, however, is not the case.

What is being presented with the 'water fuel' concept is a molecular
splitting and a molecular fusion of hydrogen and oxygen atoms, not
'atomic fusion'. Molecular splitting is much, much easier to
accomplish than it's atomic cousin. It occurs naturally every time you
light a fire. The combusion of wood, coal, or whatever is the result
of the splitting of molecules and the subsequent release of energy
(fire), and smoke.

What is so hard in the case of 'atomic fusion' should prove much easier
for the 'molecular fusion' of water. It, apparently, is happening on a
tiny scale within supercharged motors and turbines. Increase the heat
by several magnitudes and it should happen on a mega scale releasing
huge amounts of energy.

How huge? Well, if I am not mistaken, the formula reads that a single
double molecule of water (2H2O) releases 572 thousand joules of energy
per double moleucle. Now multiply that by a few hundred trillion
molecules and see what you get! Interested? If I have misread the
energy formula for molecular water fusion please post a note. Frankly,
it sounds almost unbelievable. Heretofore I had though only nuclear
(atomic) fusion could generate energy like this.

Once again, I await your comments.


tomcat

H2-PV NOW wrote:
If you know you need fuel for return, taking H2O is the most compact
form, and considerably safer than than carrying around excess flamable
gases before you actually need the gases.

This is an interesting argument. Consider a voyage to Mars for instance.
Solar arrays could continually electrolyse water to provide not only O2
for cabin, but also O2 and H2 for propulsion. And the water would also
serve as shielding.

However, you would still need storage for H2 and O2 for the major
propulsion events. For instance, for orbit insertion at Mars, you'd need
to have enough fuel stored to do the burns to do a quick orbit
insertion. So you'd need to be building up some O2 and H2 tanks slowly
over time so that they are full at the time you need to do a large burn
in a short amount of time (entering orbit, leaving orbit). The advantage
is that you'd re-use the tanks for multiple events isntead of carrying
tanks for each of the 4 big events (leave earth, arrive mars, leave
mars, arrive earth).

But if it takes you months to fill thsoe tanks by using solar power to
electrolyze water, then you need to have tanks capable of storing h2 and
O2 for months.

The idea of manned travel to Mars using chemical propulsion is quaint

Face facts the travel time is just too long. To go to mars or elsewhere
is going to demand nuclear propulsion or something even better

We cant for safety reasons use nuclear for launching from earth to
orbit, which is REALLY our biggest need.

Certinally we can find a crew to take 6 or 8 months each way to mars
and a couple years there till its time to return.

the trouble with a 4 or 5 year mission its just too expensive,
requiring too many consumables, and redundant gear.

now compare that with nuclear propulsion, where the travel time is just
a few months each way, fire engines till half way out, then flip around
and decelrate the rest of the way. with a month on the surface the
mission is over before the non nuclear mission has evven arrived. that
cuts costs dramatically!

the big problem with getting out of LEO is $$$

NERVA the nuclear stage could of been built 30 years ago

John Doe wrote:
H2-PV NOW wrote:
If you know you need fuel for return, taking H2O is the most compact
form, and considerably safer than than carrying around excess flamable
gases before you actually need the gases.

This is an interesting argument. Consider a voyage to Mars for instance.
Solar arrays could continually electrolyse water to provide not only O2
for cabin, but also O2 and H2 for propulsion. And the water would also
serve as shielding.

I guess I should have been more clear and said that my interests are
Spaceplanes SSTO to LEO. Going to Mars without a Lunar base is, well,
Lunacy. A lot of what you might want for a trip to Mars is
prepositioned on the moon, where the launch penalties are far lower.

My interests are not intellectual but actual. I want to enable the SSTO
and LEO habitat efforts and then GEO and L-5. A step by step effort
means that travelling to Mars is on a luxury liner, not in a cramped
tin can with your fellow's unwashed smelly feet drifting into your face
all night packed like sardines, slowly going insane.

Of course tastes differ, and some people actually prefer spending five
or more years of their life in conditions similar to a blend of
third-world prison cell and a homeless shelter with guys who don't
bathe too often.

Yes, water is a luxury item in space, and as of right now, Earth is the
only certain place to get any. A single gallon of it weighs 8 pounds,
and according to NASA, that makes a gallon of water worth $80,000 at
the International Space Station, wholesale, before tax and dealer prep.

Did you know that at the ISS they dump their **** overboard, at $80,000
a gallon for that too? You'd think with vacuum close at hand and
nightime temperatures below freezing, they could freeze-dry purify it.
Or daytime temperatures steam distill it. Maybe if they had to pay for
supplies lofted to orbit they might think better, but they have a rich
uncle sugar who pays all their bills, so they don't have to think.

However, you would still need storage for H2 and O2 for the major
propulsion events. For instance, for orbit insertion at Mars, you'd need
to have enough fuel stored to do the burns to do a quick orbit
insertion.

I guess you have a rich uncle sugar too...

So you'd need to be building up some O2 and H2 tanks slowly
over time so that they are full at the time you need to do a large burn
in a short amount of time (entering orbit, leaving orbit). The advantage
is that you'd re-use the tanks for multiple events isntead of carrying
tanks for each of the 4 big events (leave earth, arrive mars, leave
mars, arrive earth).

NOBODY is going to Mars like that. It's not just an Apollo mission writ
larger..


But if it takes you months to fill thsoe tanks by using solar power to
electrolyze water, then you need to have tanks capable of storing h2 and
O2 for months.

I could have sworn I answered that objection in the message above in
the thread. Let me look...
http://snipurl.com/mqu0
Yup, there it is...

The Homopolar Generator is portable, works everywhere in the universe
as far as I know, as far as anybody knows right now. You make a disk
out of a conductor and add a magnet layer to it and spin it. While
there is no gravity drag on it in zero-G it still hass mass which
requires power to spin it. However it need have no friction, which is
more serious than gravity drag, but then it has electrical reactance
which adds up over time. While you won't get a free lunch out of such a
thing you can get astronomical amounts of power (literally,
astronomical).

The reason you don'y know more about homopolar generators is because
they are used on hush-hush classified stuff like driving nuclear sub
propellers, or experimental railguns for tanks. Some applications are
proprietary because companies don't want to tell the competition how
they are doing what they do, like welder power supplies and
electrolyser units.

How about a nice leisurely time period gaining a body of experience in
civilian applications like power supplies at LEO. Then, after enough
people know the difference between a homopole and a gay pride parade,
then, maybe, we might be ready to discuss propulsion that has more
power and less costs than rockets?

Until then, concentrating on SSTO to LEO is about the hardest thing the
human race is actually capable of achieving in any time period of
reasonable length. But good luck in your interplanetary jail cell with
your neighbor's stinky feet if you decide to rush pell mell into things
without solving the easier problems first before you tackle the harder
ones.

Without SSTO to LEO the water supply on any mars expedition is going to
be too rationed to have bathing. Not even Uncle Sugar is rich enough to
buy you two years of drinking water at $80,000 per gallon.

H2-PV NOW wrote:
Probably has to do with the glass lining, don't you think? If it wasn't
a vacuum seperated bottle in a bottle, then convesctive and conductive
heat gain would be high. The coldness of the LOX would promote thick
frost/ice accumulation on the tank outer surfaces leading to both
aerodynamic drag and ice chunk falling hazards.


NASA seems to be having a problem with tank ice on the Shuttles. In my
judgment it is best to put the tanks within the body of the vehicle,
not attach them to the belly.


It increases it due to the fact that a leaner fuel mix is used. Perfect
combustion of H2+O2 to H2O cannot be counted on due to the short
latency time in the combustion chamber. LH2/LOX is burned at a 1:4
ratio instead of 1:8 ratio by mass/weight. With Slush-LH2/LOX the H2 is
birned at a 1:6 ratio, a 50% improved fuel efficiency. The Isp remains
constant as only the reaction of 2H2+O2=2H2O counts. None of the
unburned H2 adds thrust.


Rocketdyne says that the SSME is 99% efficient. I don't know what that
figure is based on but I don't think it really means that 99% of the
fuel is converted to energy. More efficient combustion of the LH2/LOX
mixture may be called for.


Composite tanks for compressed H2 have been approved in Europe for road
vehicle use to 10,000 psi pressure, with 2.35 safety margin, passing
tests to 24,000 psi.

Several ideas have come to mind. First, why not use these tanks in
place of the evaporation tanks on rockets? Second, why not build even
stronger tanks and super compress the hydrogen into slush, or even into
a pure solid state?

Stronger tanks up to 2,000,000 psi are theoretically possible but the
cost is out of this world. A new era of "conformable tanks" is just
dawning, and the testing process is bth time-consuming and costly.

One way to 'slush' LH2 is to allow rapid evaporation of the liquid in a
vacuum. Since rocket tanks are vented a similiar condition must exist
in the vacuum of space. Also, liquid helium is used to provide
pressuriziation gas for the tanks. Since liquid helium is colder than
liquid hydrogen this would tend to 'slush' the tanks too.

It may very well be, therefore, that rocket tanks exposed to space gain
a substantial performance boost due to 'atomic' hydrogen atoms fusing
together on combustion. Also, the helium gas present will greatly
expand. In this sense, the helium is not inert.

The concepts of 'atomic' hydrogen fuel may have already been proved in
Outer Space on various flights. It might have resulted in mysterious
power increases on LH2 engines. And, if this is the case, it may have
also proven that current engines, such as the SSME, are capable --
without modification -- of handling the increased stress of 'atomic'
hydrogen fuel.

We may, indeed, be very close to actually utilizing the new NASA
'atomic' hydrogen fuel, which is just the next step beyond 'slush'.


DEsigning high pressure tanks for Hydrogen Economy fuel cell road
vehicles has uncovered a new failure mode never seen before and not
even predicted by prior experience. These tanks can be made to explode
where the tank turns to dust, and it happens so fast that high speed
cameras with 4000 frames per second barely capture the even on one
single frame, although sometimes it happens between frames.

Now you see it, now you don't, in 1/3000th of second.
http://www.eere.energy.gov/hydrogena...eisberg_04.pdf
http://www.eere.energy.gov/hydrogena...fs/30535ar.pdf

They call it "benign" failure because it doesn't throw tank shrapnel,
but you are still left with a ball of Hydrogen rapidly expanding.


Thicker, stronger tanks shouldn't be all that expensive and should
remedy the situation


For the same reason they don't use peanut butter: ductility. The reason
we can shape titanium is because of ductility. That's the thing you
want to avoid in high pressure tankage.


What are the tanks normally made of, aluminum?


Forget SSME. The experimentt is over -- it failed to produce what it
was being tesed for: cheap frequent reusable orbit insertion. Time to
move on. NASA has accepted that decision. Now it's your turn. It's
over.


The SSME (Space Shuttle Main Engine) is a proven workable engine. With
slight modifications it could well become the 'atomic hydrogen' engine
of the future.


There's no such thing as "spectacular performance" when it costs, $55m,
$500m or 1.2b per averaged flight. Get over it -- the entire concept
failed to deliver cheap regular frequent orbit. Move on to better
things. This is a cul de sac. Back out and start from where it went
wrong. You can't make progress in this dead end.


I agree that the Shuttle is graying a little with age. New vehicles
are required to do what needs to be done. My recommendation is a
waverider triangle with LH2/LOX propulsion. But the potential of new
fuels should be considered as well. One of the top contenders is
'atomic hydrogen' in development at NASA's Glenn Research Center.


NASA flew the Helios Prototype to 96,863 feet on 28 horsepower of Solar
Photovotaics-Powered plastic covered wings in 2001. Extend THIS, not
waste your time tweaking the Shuttle.

I predict that the first spaceplane to reach ISS will be a rocket
powered biplane with wings larger than 8,000 feet square. It will look
more like the B2-Spirit carrying the Concorde piggyback than it will
look like the Space Shuttle riding on the 747.

It will take on the bulk of it's oxidizer at 100,000 feet as it sprints
to orbit, and the wingloading will be less than 20 pounds per square
foot at takeoff. Like the Helios Prototype, it will have PV solar cells
on the upper wing surfaces for power during orbit.

It will carry both water and ammonia for return fuel, converted to N2,
O2 and H2 at station. The N2 and some of the O2 will be left at station
each trip for breahable atmosphere for an ever expanding LEO habitat
program, and the H2 and some of the O2 will be used for poiwered
decent. NH3 has 1.7 times the Hydrogen density of LH2. Nine liters H2O
has 1 kilogram of H2 and 8 kilograms of O2 contents, compared to 14
liters for one kilogram of LH2, 1.5 times the Hydrogen density.

It makes more sense to carry breathable air to station in forms
containing fuel values for refueling than to carry compressed air tanks
to station. Because of the long processing times, return fuel would
likely be made at station from previous deliveries, although solar
cells on wings permit staying as long as it takes for return flight
without depending on prepositioned return fuels.

There is a perpetual requirement for air and water deliveries to LEO,
so some launch budget must alway include these payload fractions
anyway. It's going to be a very long time before lunar deliveries of O2
will help supply.


Another option is CH4/LH2 Gelled Hydrogen with metal particles.
http://sbir.grc.nasa.gov/launch/GELLED.htm


The high solar power and long solar "days" of above atmosphere will be
used for making cryogenic gases in orbit for active cooling re-entry.
Return cargos may be returned seperately on their own unpiloted craft
assembled at LEO. This will bring the wingloading down below 5 pounds
per foot square. Oxidizer will be reloaded on return trip same way as
outbound for powered aeronavigation to any convenient chosen landing
port. Such a craft will do double duty as transcontinential air
carrier.


Interesting ideas, but watch out for Murphy's Law. The greater the
complexity, the greater the risk of failure. Therefore, extreme
complexity means extremely great probability of failure no matter how
many precautions are taken.


tomcat

tomcat wrote:
H2-PV NOW wrote:
Probably has to do with the glass lining, don't you think? If it wasn't
a vacuum seperated bottle in a bottle, then convesctive and conductive
heat gain would be high. The coldness of the LOX would promote thick
frost/ice accumulation on the tank outer surfaces leading to both
aerodynamic drag and ice chunk falling hazards.


NASA seems to be having a problem with tank ice on the Shuttles. In my
judgment it is best to put the tanks within the body of the vehicle,
not attach them to the belly.

Look at that big external tank that the shuttle and two solid rocket
boosters are strapped on. Now WHERE INSIDE do you fit that?


It increases it due to the fact that a leaner fuel mix is used. Perfect
combustion of H2+O2 to H2O cannot be counted on due to the short
latency time in the combustion chamber. LH2/LOX is burned at a 1:4
ratio instead of 1:8 ratio by mass/weight. With Slush-LH2/LOX the H2 is
birned at a 1:6 ratio, a 50% improved fuel efficiency. The Isp remains
constant as only the reaction of 2H2+O2=2H2O counts. None of the
unburned H2 adds thrust.


Rocketdyne says that the SSME is 99% efficient. I don't know what that
figure is based on but I don't think it really means that 99% of the
fuel is converted to energy. More efficient combustion of the LH2/LOX
mixture may be called for.

You are misunderstanding what is meant by efficiency. H2 can only burn
when it finds O2. In the tiurbulent gas streams and combustion
environment it gets a very short amount of time to do that.

Theoretical efficiency is 100% if every molecule of H2 finds an O or O2
the mate up with. Because of the short latency time in the combustion
chamber that 100% fuel efficiency is not possible. "Rich" mixutes of
fuel and oxidizer means that there is extra fuel in the mix looking for
O2 partners and the chances of finding them are increased. LH2/LOX
rockets typically have double the H2 component, 4O per 1H, wasting 50%
of the fuel as unburned expelled molecules in the rexhaust stream.
Slush/LH2 only wastes half of that, for a ratio of 6O per 1H ratio.

The goal is not to conserve fuel, but to get sufficient power, in the
short time that it will do you any good. Efficiency, then is getting
all the power you possibly can in the short latency time that fuel and
oxidizer are lingering in the combustion chamber. If they burn
downstream you get no lift from that.

....

One way to 'slush' LH2 is to allow rapid evaporation of the liquid in a
vacuum. Since rocket tanks are vented a similiar condition must exist
in the vacuum of space. Also, liquid helium is used to provide
pressuriziation gas for the tanks. Since liquid helium is colder than
liquid hydrogen this would tend to 'slush' the tanks too.

It may very well be, therefore, that rocket tanks exposed to space gain
a substantial performance boost due to 'atomic' hydrogen atoms fusing
together on combustion. Also, the helium gas present will greatly
expand. In this sense, the helium is not inert.

I think you are over-estimating the virues of "atomic" hydrogen. Fuel
cells reduce hydrogen to atomic form through catalysis, and they do it
quietly, efficiently, and non-spectaularly. Fuel cells are not rocket
engines because of some magic property of atomic (non-molecularly
bonded) hydrogen.

Instead of trying to squeeze more power out of hydrogen as a fuel, stop
making it work so hard and accomplish more. The problem is NOT that
hydrogen is not giving lots of power already -- the problem is it is
being asked to lift 8 to 16 times its own weight in oxidizer from a
dead stop under the thickest part of the atmosphere.

That's the problem to solve: how do you avoid the weight and volume
penalty of carrying 8 to 16 times the fuel mass (of oxidizer) until you
are clear of 90% of the atmosphere? SKYLON and SABRE claim they are
solving that problem by air-breathing up until they are at Mach 5.5,
and filling their LOX tanks at high altitude from the thin air at high
speeds.

It's a very intelligent approach. Unfortunately the math is not that
clearly on their side. In order to chill air to LOX temperatures they
need additional LH2, which is colder, but not that much colder than
LOX. Air is 90% N2, which will drain heat from LH2 without contributing
any lift, so the N2 has to be jettisoned with it's chill subtracted
from the LH2. The process of seperating O2 and N2 has to occur very
fast or else too much LH2 is being lost, and the take-off LH2 load
begins to get too big and too heavy for the mission objective, which is
to reach LEO as a Single-Stage-To-Orbit vehicle.

The margins are slim. The allowable time window is narrow. The
technology must work perfectly and it must work extremely well.

For these reasons, plus the small cargo payload, SKYLON does not look
like a useful answer even if it does work as advertised.

The concepts of 'atomic' hydrogen fuel may have already been proved in
Outer Space on various flights. It might have resulted in mysterious
power increases on LH2 engines. And, if this is the case, it may have
also proven that current engines, such as the SSME, are capable --
without modification -- of handling the increased stress of 'atomic'
hydrogen fuel.

There's no such thing as "Leprechan Hydrogen", some magical hydrogen
that is different from the ordinary kind. Hydrogen as H2 is more
compact than hydrogen as H+H atomic non-molecular form. I don't care if
you freeze it into bricks, the molecular form has reduced in size from
atomic solitaires. Atomic H is very unstable and seeks the first form
of stability as H2. This is an exothermic chemical reaction that
liberates heat energy which causes a chain reaction that causes all the
H to form H2, but now highly excited by the thermal energy released.
Heat turns to kinetic energy which becomes expansion and pressure
energy and the end of that is ruptured tanks, death and destruction.

For WHAT? So you can avoid looking at the real problem of trying to
lift too much oxidiser from a dead stop under the thickest atmosphere?

SKYLON is not the best answer, but it is far better than trying to lift
too much oxidizer in the first place.

The first place SKYLON can be improved is with much bigger wings. NASA
Helios prototype flew to 100,000 feet in 2001, the same altitude that
SKYLON picks up its oxygen supply, but the Helios got there on big
wings with 28 horsepower of electric motors. Those electric motors were
powered by solar cells,

There are several proposals to launch from 100,000 feet from platforms,
including an unmanned kite, and one proposal to launch from balloon.

Stop asking Hydrogen to lift backbreaking loads all on it's own. It
can't do more than physics allows and Leprechan Hydrogen found in a
box of Trix is not any kind of answer.

Shed the weight. Use the air for lift. Take on the oxidiser at the last
altitude there still is plenty. Be already going fast when you load the
oxidizer. Begin going fast after 90% of the air is below you. Hydrogen
can do this much and no more. Settle for what the laws of physics says
is the limits.

The Shuttle costs $10,000 per pound of payload delivered. Accept it
that is too high a price to pay. "Atomic" hydrogen is not cheaper, but
it's more deadly, for no important gain in trading dihyfrogen for
monohydrogen.


We may, indeed, be very close to actually utilizing the new NASA
'atomic' hydrogen fuel, which is just the next step beyond 'slush'.

So what? You pay $15,000 per pound to orbit instead of $10,000 and get
lots more crashes on TV to talk about.

The problem is not that Hydrogen is not powerful enough already. The
problem is we are loading it down with too many burdens to carry. If
you want $10 per pound payload to orbit you have to shed the weight,
you have to let the Earth's low altitude air carry some of the weight,
and you need to load the heaviest part of the fuel supply after the air
is very thin, and do this when you are already moving faster than
non-astronauts move through the air.

You are redesigned a fine fuel instead of redesigning a fat pig of a
ship. Even NASA has given up on the Shuttle. It never did what it was
created to do: frequent, regular, low-cost, routine flights to LEO with
a cargo equivilent to a highway truck load. Even if the external tank
was half as big, filled with twice as powerful Leprechan monohydrogen,
there would still be two solid rocket boosters strapped on. The LH2/LOX
external tank is not recovered, and it's cost is not the main barrier
from meeting the objectives: frequent, regular, low-cost, routine
flights to LEO with a cargo equivilent to a highway truck load.

The thing that is strapped to the tank is the problem, and nothing you
can do to that tank and its contents will change the thing strapped on
it.