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"Prep School" for Rocket Warfare
Radio-steered "city busters" of the war that must never happen may be the "next
generation" of those sky scraping rockets that are trying their primitive fins high
above the New Mexico desert.
Jet-driven underwater missiles are swimming along a test channel in California,
grimly promising to make the torpedo a firecracker by comparison.
The giant rocket - which may eventuate in the most terrible of atomic weapons
boring thousands of miles through space, or in an interplanet ship or an intercontinental
freight carrier or a scientific explorer of the skies - is in its infancy. The race
is on for its development, and imaginative American scientists and war-schooled
military men are pooling theory and experience to keep the United States to the
fore in a field where German supremacy almost won the war.
We were not asleep while the V-2s - now captives serving us as laboratory tools
-were flattening city blocks in England. Rockets played their part in our own victory.
But the "V" weapons nearly changed the final score, and the Allies were fortunate
that time was too short for the Nazis to learn all that we now are learning of long-range
missiles.
V-2 on New Mexico firing platform is fueled by liquid oxygen-alcohol
blend carried in two 1000-gallon tanks
Concrete blockhouse where controls for firing all giant rockets are located.
All controls for firing large missiles are in this concrete blockhouse
with walls 10 feet thick and roof 27 feet thick. Sprinkler system seen at top and
sides of roof is safeguard against blaze in case misfired rocket falls on the blockhouse.
Tower at rear is for observing small rocket.
A Apparatus to establish time base for all stations observing rocket's
flight in trial
B Soldier peers from outside at B five-inch-thick armored glass protecting
an observation slit
C Firing of all large missiles is directed by operators at this
panel in the blockhouse
Already we have plans for static test stands to try the motors for 150-ton rockets
that are being conceived in current research programs. Other rockets that can race
to the upper limits of the atmosphere and relay weather information back to earth,
supersonic "test tubes" that will investigate new air-foil shapes, radar-tracked
and radio-guided rockets all are close to realization.
Before he relinquished leadership of the AAF, General H. H. Arnold warned Congress
of the need for an intensive research program: "If we fail to keep not merely abreast
but ahead of technological development, we needn't bother to train any force and
we needn't make any plans for emergency expansion. We shall be totally defeated
before any expansion could take place!"
This summer at White Sands, New Mexico, Proving Grounds the Army Ordnance Department
is experimentally firing a series of German V-2s up to the 100-mile level above
the earth, well beyond the heights their inventors achieved. These nearly 14-ton
giants, pointed skyward on a concrete launching platform, emit fire like a blast
furnace and leave the ground with the roar of 100 express trains.
The rocket takes off slowly at the speed of a building elevator but accelerates
rapidly and is moving 3000 miles per hour within a minute. It reaches maximum velocity
of 3800 miles an hour at a point about three quarters of the way in its path of
descent, finally crashing in the impact area, 30 to 40 miles away, its fuel explosion
alone gouging a crater 35 feet across and 25 feet deep.
Controls for the firing are located in a concrete blockhouse some 300 feet away,
with walls 10 feet thick and a 27-foot-thick roof. The rest of the area is cleared
and a rocket shell fired from the blockhouse signals the outlying observation stations
two minutes before the hulking V-2 is sent on its way. Painted a glaring yellow
and black to aid observation, the finned cylinder is as high as a three-story building.
"WAC Corporal" in position at bottom of 102-foot steel launching tower.
The rocket weighs nearly 700 pounds and is 16 feet long. Standing alongside is Dr.
Frank J. Malina, Cal Tech scientist who developed fuel now used to fire it nearly
50 miles up
The giant V -2 missiles and rocket aircraft were two of Germany's major jet propulsion
achievements during the war. The United States, meanwhile, concentrated on short-range
artillery and aircraft rockets that were most suitable to our immediate military
needs. But all the while, under wraps, we were working on advanced types in the
longer-range categories.
Much of this research was centered at a secret 40-acre laboratory area near Pasadena,
Calif., operated by the Jet Propulsion Laboratory of the Guggenheim Aeronautical
Laboratory of the California Institute of Technology. Here scientists invented and
perfected the JATO (jet-assisted takeoff) units by which heavily-loaded military
aircraft are boosted into the air after very short runs. Here, too, they developed
the various GALCIT solid grain propellants for a variety of propulsion purposes.
Cal Tech also is experimenting with new liquid propellants and with various kinds
of radio controls.
The institute's jet propulsion program for the armed services was initiated by
Dr. Theodore von Karman. At present Dr. C. B. Millikan is acting chairman of the
executive board and Dr. Frank J. Malina is acting director of the Jet Propulsion
Laboratory.
Three million dollars have been spent for explosion-proof observation rooms,
conrete firing pits in which rockets are anchored for stationary tests, a towing
channel for the study of underwater jet-propelled missiles, and other special equipment.
The project personnel operate a test station for the Ordnance Department of the
AAF Muroc Army Air Base, Calif., where a firing pit large enough for the testing
of liquid propellant rocket motors of up to 20,000 pounds thrust has been constructed.
A motor of this size consumes propellants at the rate of three tons per minute.
V-2 being readied on launching platform for firing test. It is more than
46 feet long and 5.41 feet in diameter. At present its maximum range is about 230
miles and its greatest vertical distance between 75 and 100 miles. Descending, it
attains 3800 miles an hour. Relative trajectories of both the V-2 and the WAC Corporal
are shown
Hydrobomb tests are made in this 500-foot tank with underwater observation windows.
The electric-powered tow car is lowered to the tracks at either side of the tank,
completely straddling it when in operation. Still experimental, this plane-borne
supertorpedo can carry a heavier charge twice as fast as current types
Among the moderate-range experimental missiles developed at Cal Tech were the
eight-foot-long needle-nosed "Private A" that has a range of 11.3 miles, and the
"Private F," similar to "A" but equipped with horizontal lifting tail surfaces of
nearly five feet span plus stubby nose wings of less than three feet span. They
were designed for studying guided missiles.
For the Ordnance Department the project built the "WAC Corporal," code name for
an upper-air sounding rocket that has been tracked by radar to an altitude of 43.5
miles. It carries meteorological instruments in its long needle-point nose.
The WAC Corporal is 16 feet long, a foot in diameter and weighs less than 700
pounds. It is launched vertically inside three guide rails contained in a 102-foot-tall
steel tower. Initial acceleration comes from a booster unit that delivers 50,000
pounds of thrust for a little more than half a second. An inertia-operated valve
then turns on the main motor that delivers 1500 pounds of thrust for a total of
45 seconds. This drives the missile almost 50 miles up.
The booster unit consists of an adapted motor of a "Tiny Tim" rocket, originally
designed to be launched from an airplane and delivering the punch of a 12-inch naval
shell. It was developed at Cal Tech and was used at Okinawa.
The propellant. mixture in the WAC Corporal consists of a fuel and an oxidizer,
each in a separate tank, that combust spontaneously when brought together in the
combustion chamber. Aniline is used as the fuel and nitric acid is used as the oxidizer.
This combination, developed under Dr. Malina, automatically ended ignition, combustion
and "throbbing" problems earlier encountered with liquid propellants.
Compressed air pressure feeds the propellants into the combustion chamber. The
jacketed chamber is cooled by the flow of the aniline en route from its storage
tank.
Much work is being done on liquid propellants. The present acid-aniline combination
is superior to an earlier nitric acid and gasoline mixture that was ignited by a
spark plug in the combustion chamber. New discoveries in turn may supersede acid-aniline.
One oxidizer that has promise is a high-strength hydrogen peroxide. A nitromethane
monopropellant, too, is being used experimentally in small rocket motors for periods
as long as five minutes.
One American technique has been to force the propellants from their tanks to
the combustion chamber by means of compressed air. The Germans used this and also
developed the turbo-rocket system, used in the V-2, by which gas obtained from hydrogen
peroxide operates a turbine that pumps the propellants from their tanks. Research
is continuing on these systems and also on a way of manufacturing pressurizing gas
from chemicals placed in the rocket.
Cooling the rocket motor is another problem. The best method so far has been
to circulate the liquid propellant around the motor to absorb the heat. Under investigation
is a proposed "film cooling" method by which the walls of the combustion chamber
and exhaust nozzle are coated with a film of liquid. It may be that the evaporation
of this film during combustion will keep the walls at a satisfactorily low temperature.
Another weapon that Cal Tech is working on experimentally is the hydrobomb, designed
to be dropped from an airplane and to travel under water like a super-torpedo. A
jet propulsion motor gives the hydro bomb an underwater speed of 70 miles per hour,
twice the speed of the usual Navy torpedo. It carries a much heavier charge than
a torpedo but has a shorter underwater range.
The hydrobomb is almost 10 feet long and has a diameter of 28 inches. Its motor
is similar to a JATO unit.
For testing the hydrobomb a water tank 500 feet long, 12 feet wide and 16 feet
deep was built at the experimental area. The tank has an underwater window through
which the performance of the missiles may be watched and recorded. A rocket-propelled
tow car was placed astride the channel. Electric motors that give the tow car a
speed of 40 miles per hour have since replaced the rocket power.
Another of the Cal Tech projects is the RAFT, a rocket apparatus intended to
move an experimental airfoil at the speed of sound, or at supersonic speeds, in
order to measure its aerodynamic characteristics and report them by radio. Its name
is taken from the initials of the designation "Rocket Air Foil Tester." It will
augment and check wind tunnel studies on new wing shapes by actually flying them
at speeds approximating those for which they are designed.
Present experimental RAFTs consist of standard five-inch High Velocity Aircraft
Rockets fitted with a special type of nose. Almost six feet long, the standard HVAR
rocket travels just under 1000 miles per hour without an airfoil attached.
The airfoil under test is supported in front of the rocket's nose by means of
a rod or beam. The other end of this beam is supported at three points inside the
nose of the rocket. Lift, drag, and moment that act on the airfoil in flight are
registered at these three points by magnetic strain gauges.
A novel radio hookup relays this information to the ground. Each of the strain
gauges controls the frequency of an audio-oscillator circuit. Variations in strain
thus create comparable variations in frequency. The nose of the rocket, insulated
from the motor, serves as a half-wave-length antenna to transmit variations to the
ground, where they are received and recorded.
To keep their huge V-2 missiles on their intended courses the Germans provided
automatic pilots with three gyroscopes to control the pitch, yaw and roll.
At Cal Tech, ORDCIT men (Ordnance Department and California Institute of Technology),
in conjunction with the Sperry Gyroscope Company, are working on automatic pilots
of greater accuracy and more positive control. They are experimenting with telemetering
systems by which a rocket reports information about itself to the ground, and on
"radio link" control apparatus by which a missile may be maneuvered and directed
during flight.
A typical automatic rocket pilot consists of three air-operated gyroscopes connected
to pneumatic motors that are geared to the steering segments of the rocket fins.
When the rocket veers from its course the gyro mechanism signals the motors, which
then operate the rudders sufficiently to bring the missile back on course. The gyros,
amplifiers and motors all are driven by compressed air from the tank supplying pressure
to the propellant tanks.
Telemetering is new and complex. It reports 10 conditions continuously to a ground.
station during the flight of the rocket.
These include the angular rates around each of the three axes of the missile,
position of each of the four control rudders, hinge movement on one control surface
and longitudinal and transverse acceleration.
Small instruments in the rocket are actuated by these conditions and each of
these mechanical quantities is made the frequency-controlling element of an audio-frequency
oscillator. Five of the oscillators modulate a radio-frequency carrier wave of about
100 megacycles. The 10-channel instrument system consists of two five-channel groups,
with the two transmitters using a common antenna that projects from the nose. The
various frequencies are screened by filters on the ground and are separately transcribed
on mechanical recorders.
Still under development, too, is a "radio link" that will permit a flight control
operator on the ground to watch the flight of a rocket on a radar screen and signal
corrections if the rocket appears to be veering away from its desired course. These
corrections, picked up by a radio receiver in the nose of the missile, would be
automatically applied to the air-operated rudder motors. All the details of this
remote control system have not been worked out as yet but the general principles
are well understood.
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