Evening star., 1938-12-01
Of Stors, Men
And Atoms
Notebook Of Science Progress
In Field, Laboratory
And Study
BIZ Thomas r. Henry.

BY Thomas r. Henry.
DR.. Forest Ray Moulton, eminent
astronomer and secretary Of the Ameri-
can Association for the Advancement Of
Science, was not exactly alarmed when
he heard over his radio one night few
weeks ago that the planet earth had
been invaded by monsters from Mars.
The hoax. however, started him think
ing on the actual possibilities Of trans
portation between one planet and an
other-of such a situation as would be
faced If there actually were intelligent
beings on Mars and the earth should 60
to war with them. He found, naturally,
quite lot of fantastic impossibilities.
First there are 10000 900 miles Of
vacuum between the two planets. Con-
sequently it would be necessary to travel
In air-tight containers-say sphere
with diameter Of 20 feet. Within this
sphere it would be necessary to maintain
normal atmospheric pressure. Once it
entered the vacuum, DR.. Moulton figures,
there would be an outward pressure OF
100000 pounds. It would require steel
walls at least tenth Of an inch thick
to resist this tremendous push. Such q
sphere would weigh about 4,800 pounds,
disregarding the weight of its human
cargo and freight.
The basic problem then becomes, DR..
Moulton says, getting sphere Of this
weight of the earth and outside the pull
of the earth's gravity-after which the
problem of reaching Mars would not be
so difficult. This would require that it
leave the earth with velocity of seven
miles a second, not making allowance
for the retarding atmosphere. This is
approximately ten times the muzzle
velocity of very high-power gun. At
this high velocity, DR.. Moulton says in
the current issue Of the Scientific
Monthly, official organ Of the associa-
ton, the atmospheric resistance would
be approximately $4,000 pounds per
square inch, or more than 100000 tons
on the forward side Of the sphere.
Under such a pressure the thin steel
shell would crumple like an eggshell.
Also, he points out, the resistance Of the
atmosphere would be 100000 times
gravity. Consequently the initial velo-
city would have to be about 10 times
seven miles q second. But the greater
the velocity the greater the atmospheric
pressure. The point would soon be
reached, he says, where no material
known on earth Gould Withstand such
pressure. Thus, DR.. Moulton points out,
no such space ship could be shot of the
earth, regardless Of the push of the ex-
plosion.
The other possibility is that of the
rocket ship. which propels itself for
ward by shooting backward some of its
own material. The principle involved,
he says. is illustrated by the "kick" Of
gun against the shoulder. The bullet is
sent forward at a high speed and the
gun backward at low speed, the velocities
being inversely as the masses. High
velocities need not be developed at first
and consequently the impossible barrier
Of increasing air resistance Is avoided.
On the other hand, DR.. Moulton stresses,
1t would be necessary to carry IN the
space ship itself all the explosives needed.
Let us assume" he says, that the 20
foot rocket is launched with an initial
velocity of only quarter mile a second,
which Is well within the muzzle speed
Of guns, and that enough material is
fired backward to maintain that velocity
until the rocket has reached an altitude
Of 100 miles, beyond which there will be
no appreciable amount of atmosphere
The gravity of the earth, however, would
have remained about constant.
'In order to get the rocket beyond the
earth's control there are two forces to
be overcome-the resistance Of the
atmosphere and the backward pull of
gravity. The work that would have to
be done to get the ship 100 miles into
the atmosphere at constant speed Of
q quarter mile a second would be ap-
proximately 10000, 100000 foot pounds.
If it weighed, with its load, 10 tons, the
work required would be 5000, ,OO0,0 900
pounds. Consequently the material shot
back from it would have to do 10000
100000 foot pounds of work.
This would require, even at the maxi
mum efficiency, as much energy as there
is in 10000 tons of coal. Since a rocket
weighing 10 tons could not carry an
initial load of 10000 tons, the impossi-
bility becomes obvious"
OF course 1t would be trtde easier
for Martians to get to the earth, since
that planet does not have so strong q
gravitational pull and It's atmosphere is
much lighter. It might be possible to
launch a lotion ship into space from
a Marian mountain top with only half
as much fuel.
STILL. DR.. Moulton holds, there is no
more need to worry about Marian at
tack on the earth than for an earth at
tack on Mars-assuming, which is absurd,
that there are intelligent beings on the
neighbor planet. For once such space
craft had gotten free Of the planet itself
and was speeding freely through q
vacuum the difficulties Of its occupants