Re: Buying a BBJ and converting it to hydrogen

I agree that a fat BBJ that's getting your supposedly cheap LH2 and
consuming atmosphere of mostly N2 as it's fuel is technically doable,
although not nearly as fast due to the aerodynamic friction, and not
without creating NOx unless that useless N2 portion of our atmosphere
is getting eliminated while on the fly.

- Brad Guth


Willie.Moo...@xxxxxxxxx wrote:
On Dec 24, 4:07�pm, BradGuth <bradg...@xxxxxxxxx> wrote:
On Dec 23, 2:50 pm, Willie.Moo...@xxxxxxxxx wrote:





On Dec 24, 2:15 am, BradGuth <bradg...@xxxxxxxxx> wrote:

Good grief! � For the same cruising range, perhaps using an A380 with
roughly 10% the passenger and freight capacity is a more than likely
alternative. �Remember the amount of volume necessary for the LH2 is
not going to be all that unlike the shuttle ET, except you'll need
much more fuel storage capacity your unless cruising range isn't a
factor.
- Brad Guth

Willie.Moo...@xxxxxxxxx wrote:
I was going to call this what I did during my summer vacation! �lol

All this discussion about hydrogen fueled airlines and such caused me
to spend a lot of time, a few minutes a least, thinking in detail
about what it would take to convert a conventional airliner to burn
hydrogen.

That and the stink some reporters on FOX made about Al Gore's carbon
foot print because he flew a private jet around - haha - caused me to
think about private jets conversions. �I'm thinking about buying a
used BBJ - and a new one - which will be delivered in 7 years - and
when the old one is retired - having all the pieces and parts in place
to upgrade it.

The jet engine isn't difficult at all. The first jet engines used
hydrogen. �In today's world NOx production can be a problem, but this
can be reduced dramatically by staged combustion of the hydrogen -
which entails burner changes. �With these changes engineers who have
tested jet engines with hydrogen at the Dornier aircraft company, in
1998 and 1999 - were able to get hydrogen fueled jets to produce 2% to
the NOx of regular jet fuel powered varieties. �That with a total
reduction to zero of carbon was great!

Alright, so take a look at slides 30 and 31 at the following URL

http://www.theoildrum.com/uploads/3246/csmith.pdf

On slide 30 is shown a hydrogen version of the Dornier 328. �This
Dornier 328 shown here uses under wing nacelle tanks and a stretch in
cabin volume to increase it to 50 passengers - to take advantage of
the increased lifting capacity.

On slide 30 is shown a hydrogen version of the Airbus A300 - a
hydrogen version of the Beluga - which is basically a Beluga with
hydrogen tank up top, and a standard A300 interior below. �Hydrogen's
high efficiency at longer range means they opted for longer range
aircraft here.

But we're looking at a Boeing BBJ variant. � Here are the typical 737
specs - this is a starter for a preliminary analysis of what I have in
mind. � This is a 737 800 a little bigger than the BBJ - but will do
for our purposes of a preliminary analysis.

737-800 Technical CharacteristicsPassengers

�Typical 2-class configuration �162
�Typical 1-class configuration �189

Cargo 1,555 cu ft (44 cu m)
Engines (maximum thrust) �CFMI CFM56-7 27,300 lb
Maximum Fuel Capacity 6,875 U.S. gal (26,020 L)
Maximum Takeoff Weight 174,200 lb (79,010 kg)
Maximum Range 3,060 nautical miles (5,665 km)
Typical Cruise Speed (at 35,000 feet) �0.785 Mach

Basic Dimensions
� Wing Span � � � � � �112 ft 7 in (34.3 m)
� With Winglets � � � �117 ft 5 in (35.8 m)
� Overall Length � � � �129 ft 6 in (39.5 m)
� Tail Height � � � � � � � 41 ft 2 in (12.5 m)
� Interior Cabin Width �11 ft 7 in (3.53 m)

So, has anyone ever seen a 747 carry the Space Shuttle Orbiter around?

http://www.murdoconline.net/2007/enterprise_atop_747-thumb.jpg

Compare that to the Airbus A300 hydrogen variant.

Does that suggest anything?

Sure does - what about an ADD ON TANK right on top of the 737? �That
way you could store your tanks on the tarmac, refill them and lift
them in place, like changing batteries on a big energizer bunny.
Sweet.

So, fuel volume is 26 cubic meters. �That means you carry around 20.8
metric tons of the stuff on a typical day. �This translates to 890 GJ
of thermal energy.

Converting to hydrogen therefore which has 143 GJ per metric ton,
means that you need to carry 6.3 metric tons of hydrogen around with
you. �Add in a fuel tank weight of 10% fuel weight, and that's 0.6
metric tons. �Add interconnects and so forth, that's 0.1 metric tons.
A total of 7 metric tons of weight replacing 20.8 metric tons. �This
adds 13.8 metric tons to the payload capacity of the aircraft.

Now,at 70 kg per cubic meter that translates to 90 cubic meters. 3..5x
as large as the jet fuel tank. Let's say we can occupy 60% of the
fuselage length above the CG with a tank - judging from the Space
Shuttle length atop the 747 transport ship. �We might be able to do
more, but won't know for sure without detailed wind tunnel tests and
flow analysis.

60% of the 39.5 m length is 23.7 m. �Dividing this dimension into the
total volume of 90 cubic meters comes up with 3.8 sq meters. �Assuming
a constant circular cross section (as a first pass) produces a
cylinder 2.2 m in diameter and 23.7 meters long. �Now a cylinder is
not ideal, an ideal shape would be some sort of tear drop shape that
has a much lower drage - up to 1/10th that of a cylnider, but the
volume and diameter relations would be within a factor of 50% of the
diameter calculated here - that is 3.3 m maximum diameter would be
near the right size of a optimally shaped tear drop holding the
requisite hydrogen.

A 26% increase in dimension allows a doubling of the fuel capacity
(with a reduction of payload gain to 6.8 metric tons) and an increase
in range to 8,000 km while increasing speed by 5% and other
improvements besides, like increase angle at take off, shorter take
off and landing runs etc, despite the increase in form drag (and
reduction in induced drag)

The 14 ton fuel tanks (and 1.2 ton empties) would be easily lifted off
the top of an aircraft that taxied under a loading crane - or had a
loading crane on a truck drive up to the aircraft - removing the empty
and loading up the full one. �Several could be kept at airports that
served hydrogen fueld 737s.

So, the used BBJ costs $32 million - what do you think the upgrades
and infrastructure would cost? �(and you'd keep the jet fuel tanks and
be able to switch back and forth if needed)- Hide quoted text -

- Show quoted text -

Brad,

And you claim not to be a master of Black Propaganda. �But here you
are, practicing it like a pro.

You'e gotta know that the Space Shuttle ET carries 106 metric tons of
liquid hydrogen in 1,497 cubic meters while I just said that I would
carry 6.3 metric tons of liquid hydrogen in 90 cubic meters - to
maintain the same range - and perhaps double that to 12.6 metric tons
in 180 cubic meters to nearly DOUBLE the range.

Sheez

http://en.wikipedia.org/wiki/Space_Shuttle_external_tank

But here you are, forever stuck within this anti-think-tank of Usenet
naysayland, still poor as hell and going nowhere fast, much less via
hydrogen. �What's wrong with this picture.
- Brad Guth- Hide quoted text -

- Show quoted text -

Your statement is nearly free of any meaning in the context of our
discussion. You compared the add-on tank which is to carry from 6.2
to 12.4 metric tons of hydrogen to the Space Shuttle External Tank
that masses over 700 tons!!! I replied that such a comparison is not
only inaccurate, but it marginalizes the very concept. You replied
with gibberish.

I do admit on re-thinking that metaphorically an add-on tank atop a
737 airframe can be thought of as a sort of external tank similar to
the shuttle, and perhaps I shouldn't have responded so negatively to
your concept.

I've done a little more thinking on this subject...

Measurement BBJ
Crew 2

Length 39.47 m (126 ft 6 in)
Fuselage Width 3.76 m (12 ft 4 in)
Fuselage Height 4.11 m (13 ft 6 in)

Wingspan 35.79 m (117 ft 5 in)
Height 12.05 m (41 ft 2 in)

Weight Empty 45,730 kg (100,815 lb)
Maximum take-off weight 79,015 kg (174,200 lb)
Maximum landing weight
Maximum speed 890 km/h (481kt, Mach 0.82)
Range 10,620 km (5,735 nm)
Service Ceiling 12,496 m (41,000 ft)
Thrust-to-weight 0.52:1
Powerplants CFM International CFM56-7 turbofans
Thrust 117.4kN (26,400 lbf)


Now draw an arc that represents the top of a BBJ fuselage. Make a
copy of that arc. Move it up 1 meter. Draw vertical lines connecting
the ends of the top arc to the ends of the buttom arc. What is the
area of the space between? The answer is 3.76 m! The same as a
rectangle 1 meter tall by 3.76 m width. That's because the arc above
adds what the arc below subtracts from a box made by the box when
connecting the ends horizontally.

39.47 meter length x 3.76 m2 = 148.4 cubic meters

for every meter of height added. At 0.07 tonnes per cubic meter
that's 10.388 tonnes per meter of height added to the 4.11m height of
the existing BBJ cabin. 1.5m height addition, slightly shorter length
than that given here, due to rounding of the front before reaching the
nose, and before reaching the tail, provides for 12.5 metric-ton
hydrogen capacity - giving the modified aircraft 20,000 km range,
while INCREASING payload and take off performance. Modifying the
wings and flaps to lower landing speed, modifying the engines to take
advantage of hydrogen to increase thrust 22% - allows STOL
performance.

This tank is likely to have 0.05% boil off per day. Thus 14% remains
after 30 days. Most aviation and jet fuels have a more limited life
than this;

http://www.intertek-cb.com/petrotesting/jetfueldegradation.shtml

The Glenn Research Center in Cleveland Ohio has looked into the
potential of MEMs based cryogenic refrigerators that are powered by
the boil off to reduce boil off rates below these levels. Boil off
itself can be used by fuel cell systems to provide auxiliary power for
the tank.

http://www.cstl.nist.gov/projects/fy05/msci05radebaugh.pdf

A fully fueled tank holding 12.5 tonnes of hydrogen with a 0.05% boil
off yields 6.25 kg per day. That's 260 grams per hour. 72 milligrams
per second. Enough to generate 6.1 kW of electrical power in a fuel
cell that's 60% efficient. A cryogenic refrigerator that reduces boil
off by a factor of five, would consume 1.22 kW. Modulating this
output would allow power levels of the tank systems to be throttled up
and down, and operate independently of the external tank.

http://www.flickr.com/photos/8362988@N06/810948952/

The tank would start just above the front wind screen and arc up 1.5
meters by the time is went behind the entry door. Then its sides
would wrap around the back of the door, and run along the top edge of
the windows. It would have a slot in the back to wrap around the base
of the tail fin, as it tapered back to end at the tail section. The
antennae located on the top would be surrounded by pickups, and the
antennae patterns would be repeated precisely atop the tank.
Structural connections would be located at appropriate points around
the roof of the aircraft. Fuel connections would be placed in the
base of the tail section and connect to the tank there during set
down. In the superstructure just described, there would be four tank
sections running the length of the tank just behind the door and
running to just past the the base of the tail. Each tank holding
3.125 metric tons of hydrogen. Mechanical, electrical, and other
components are located in the tank housing fore and aft of these four
dewars.
.