This month's popular science - hydrogen powered hyper jet


http://www.popsci.com/popsci/

The February issue of Popular Science has an article of a hydrogen
powered hyper-jet, which pretty much justifies my earlier comments
about a Concorde replacement, which I've repeated below.

Cheers all!
William

* * * *

The Concorde was a Mach 2,2 passenger jet that carried 100 passengers
and had the following specifications


188.6 tonnes - total weight
78.2 tonnes - empty weight
96.5 tonnes - fuel weight
13.9 tonnes - payload


Each tonne of jet fuel has 43.8 GJ of thermal energy. Thus, to drive
this aircraft its 7,250 km range expended 4226.7 GJ of energy. The
tank weight for the jet fuel is about 0.8 tonnes.


To create this much thermal energy with hydrogen fuel requires 29.6
tonnes of hydrogen. To contain this amount of hydrogen requires a
tank massing 3.0 tonnes. This is quite a massive tank. However, the
combined weight of fuel plus tank of 32.6 tonnes is less than the
fuel
plus weight of jet fuel which is 97.3 tonnes. This is a weight
savings of 64.7 tonnes. Adding this to the empty weight and payload
obtains 156.8 an increase of 70.2% The payload rises to 23 tonnes
and
the empty weight rises to 133 tonnes. As a result


The fuselage is 2.88 m in diameter and the length is 61.66 m. in the
Concorde.


This increases to 3.44 m in diameter and to .73.6 but the wings staty
the same.


The number of first class passengers increase to 170 from 100.


Fuel costs drop from $96,500 per flight to $23,700. Assuming $900
per
ton for jet fuel and $800 per ton for hydrogen.


That's a reduction from $1,485 per passenger at 65% loading to $215
per passenger at the same loading.


188.6 tonnes - total weight
137.0 tonnes - empty weight
29.6 tonnes - fuel weight
23.0 tonnes - payload weight


Concorde tickets sold for $12,000 - but the plane seldom flew full
and
tickets were highly discounted. - so pricing efficiently at say 2x
fuel costs a Concorde ticket should go for $3,000 and a hydrogen
concorde replacement could sell for $430


When one looks further back in history, we can see another aircraft
that is interesting, the XB70 Valkyrie. This aircraft was very
similar in size and weight to the Concorde, but flew 50% faster -
Mach
3.5


http://en.wikipedia.org/wiki/XB-70_Valkyrie


The interesting thing about this is that the propellent weight is
about the same fraction as in the case of the Concorde despite the
fact that the speed is 50% greater and the range is greater as well.
This suggests that a Mach 3.0 aircraft (2,000 mph) capable of flying
between New York and Paris or New York and London in 1 h 45m - is
possible. An LA to Tokyo flight is also interesting, which could
be
done in 2h 45m at Mach 3.0. LA to Sydney, if the range could be
worked out would take 3 h 45m at Mach 3.0. NYC to LA would take 1
h
20m. A direct flight from London to Sydney at Mach 3.0 would take 5
h
30m if range could be worked out.


Increasing aircraft size to 350 kg - about the size of a 777-200 -
smaller than a 747.- and assuming structural weight can be reduced to
60% - we have;


350 tonnes - total weight
210 tonnes - structural weight
77 tonnes - fuel weight
63 tonnes - payload weight.


This is enough for 450 passengers at the same loading as the
Concorde. At $800 per tonne for hydrogen this is $50,400 per flight.
With 75% loading that's $150 per passenger. Ticket prices at 2x fuel
prices are $300 per passenger. This is at a seat spacing that is on
par with business or first class seating for the 2 to 4 hour flights.


With larger fuel weight percentage range increases. Furthermore
systems can be simplified. For example, a combined cycle ramjet/
rocket engine can operate with liquid oxygen during takeoff and
landing, and use ramair at speed. This would be akin to a JATO unit
that stays permanently attached to the aircraft.. To achieve Mach
0.7
with an advanced RL10 engine set opeating at 466 sec Isp requires a
5%
propellant fraction - as the rocket segment to the ram rocket.
That's
17.5 tonnes of propellant. At a 5.88:1 lox/h2 ratio that's 2.5
tonnes
hydrogen and 15 tonnes liquid oxygen. This leaves 17% fuel fraction
remaining, which is greater than the fuel fraction sited earlier so
ranges should be higher, especially when the range from altitude and
speed are added.


With a thrust to weight ratio of 0.35 the aircraft should produce
122.5 tonnes thrust. That's 18 RL10 type pumpsets feeding a thrust
chamber and intake system. 3 sets per intake/thruster means a 6 pack
of the type seen on the XB70. All 18 systems comprise a total weight
of 2.5 tonnes.


Two between


Sydney LA
Tokyo LA
LA NYC
NYC London
NYC Paris


would require 10 aircraft be constructed. WIth two spares used as
training and test aircraft, that's 12 aircraft. At $200 million per
aircraft, this is a program cost of $2.4 billion. With 12,000 flight
cycles per aircraft, this is a total of 120,000 flight cycles for the
10 operating aircraft. With 450 passenger seats at 75% loading - 338
passengers per flight. 40.56 million trips per fleet. At 2 flight
cycles per aircraft per day - that's 12 year life span. At $450 per
flight that's a $300 profit per trip - or $12.2 billion profit for
the
fleet. The flight consumes 7.44 million tonnes of hydrogen over
their
lives.


Increasing costs to $750 per flight and assuming a loading factor of
85% - dramatically increases profits 226% to $27.7 billion over the
life cycle of the fleet!


.

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