Evening star., 1961-09-17

80
conventional chemical rockets
to get to the moon, needed
even more when atomic rock
cts become practical.
Hydrogen is full of paradox
It costs so cents pound but
is SO light that it is cheaper
by the gallon (34 cents than
premium grade gasoline. 1t is
terribly cold (423 degrees below
Fahrenheit zero) but it burns
with a flame so hot as to be
practically invisible, 1t lash"
the product of its combus-
tiorl-is water.
Hydrogen in its pure form
is the most plentiful substance
in the universe, but extremely
rare on earth. Still, the earth
contains. a vast reservoir of
hydrogen; the oceans are about
two-thirds hydrogen by vol
un1e. But when spacemen want
hydrogen gas for their rockets
they go to oil wells. Liquid hy-
drogen is a petrochemical
product.
"Lox" Much Hotter
Liquid oxygen has to be kept
insulated from most substances
in rocket systems to keep them
from freezing, But it is insu-
lated In a hydrogen-oxygen
system to keep the oxygen
from boiling the hydrogen;
"Lox" is a full 125 degrees
Fahrenheit warmer than liquid
hydrogen.
hydrogen is priced as a rock
ct fuel because of the tremen-
doQs impulse it develops. Still,
no o.one is touting 1t as a suit
abb fuel for big booster rockets
like the first-stage Saturn or
NoYa.
And one final paradox: The
almost universal optimism
abeut hydrogen propulsion is
based on littlN more tn a n
faith. No hydrogen powered en-
girte has yet flown, and the
development process so far has
been plagued by bugs, slippages
and delays.
The two major builders of
hydrogen engines today are
Rocketdyne in California and
Pratt & Whitney in Florida.
Rocketdyne is developing J-2,
an. engine designed for 100000
pounds thrust, scheduled for
tests in 1868. paw has pro-
duced a smaller, 15,0o0-pound
engine called RL-10-3A, slated
to fly in the Atlas-Centaur late
this year or early next.
Both engines are in the Nova
moon-rocket picture, as we'll as
in earlier phases of the manned
space program. In the moon
mission, J-2' would provide Sec,
ond or third stage propulsion,
while RL-10 would be used for
lunar landing and takeoff ma
neuvers.
Bigger Thrust Seen
Some experts believe the J-2
is only the beginning of large
hydrogen-oxygen systems. Pm
quite sure you'll see 100000 to
/ million pound hydrogen sin
gle chambers before Nova
flies" says C. Branson Smith,
assistant chief scientist for
United aicraft in Hartford.
J-2 is the biggest in the space
program at present, however.
What may be the first piece
of the Nova moon rocket to
be built is already taking shape
at Douglas Aircraft's plant in
Santa Monica, Calf. This is
the S-4 stage of Saturn, ini-
TALLY intended as a second stage
component that could become
Nova's fourth stage.
Construction problems with
S-4 point up one serious dis
advantage of hydrogen. 1t takes
a lot of volume to contain a
substantial amount of it. De-
signers say this makes hydro
gen unsuitable in boosters, be-
cause it's tanks would have to
be intolerably large and heavy
The S-4 stage is essentially
a huge tank of thin aluminium
Al feet long and 18 feet in
diameter. 1t is believed to be
the biggest single piece of hard
ware built to date in the Space
Age. To make it Douglas had
to invent it's own technology
and design huge welding tools
some as big as a small house
Full of Energy
Hydrogen's tremendous en-
ergy content makes it worth all
the trouble, however. Rocket
fuels are rated by specific i'm
pulse" or the number of pounds
of thrust generated for each
pound of fuel consumed pei
second. Solid fuels in use today
are rated at about 240 and the
usual liquid mixture of kero-
sene and oxygen has a rating
of about 30L. Hydrogen-oxy.
gems rating is 400 or more
full third above its nearest ma
jor competitor. Hydrogen
fluorine would be even better
but this mixture presents some
difficult design and handling
problems.
When nuclear power final!
gets into the picture, hydrogen
will be used with cut al
oxidizer. This will boost TIN
specific impulse to 300 or 1000
In an atomic rocket hydrogen
gas will be pumped cold int,
the core of a nuclear reactol
quickly heated to many thou
sands of degrees, and shot ou
the exhaust nozzle.
A joint Atomic Energy-NAS.
program called NERVA (nu
clear engine for rocket vehicl
application is now bein
pushed for missions eve
4.