The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

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thin surface layer. So brief was the duration of high
temperatures that very little heat flowed into the
plate, and the researchers concluded that active cooling
was unnecessary and that either aluminum or steel
would be durable enough to serve as plate material.
The situation was similar to that in an automobile
engine, in which the peak combustion temperatures
far exceed the melting points of the cylinders and pistons.
The engine remains intact because the period of
peak temperature is short compared to the period of
the combustion cycle.
Still, it was evident that some experimentation was
needed, and so the Orion team built a series of models,
called Put-Puts or Hot Rods, to test whether
pusher plates made of aluminum could survive the
momentary intense temperatures and pressures created
by chemical explosives. Several models were
destroyed, but a 100-m flight in November 1959, propelled
by six charges, was successful and demonstrated
that impulsive flight could be stable. These
experiments also suggested that the plate should be
thick in the middle and taper toward its edges for
maximum strength with minimum weight.
There was no obvious technical flaw in the Orion
scheme or any argument to suggest that it could not
be implemented economically. Its huge weakness,
however, was that it depended upon atomic explosions
that would release potentially harmful radiation
into the environment—a fact that would ultimately be
its undoing.
Early on, Taylor and his team recognized that they
would need substantial government funding. The
Advanced Research Projects Agency was approached
in April 1958 and, in July, agreed to sponsor the project
at an initial level of $1 million per year. However,
this funding was short-lived. The newly formed
NASA was beginning to acquire all civil-oriented
space projects run by the federal government, while
the Air Force was assuming control over space projects
with military applications. Orion was initially
excluded from both camps because the Air Force felt
it had no value as a weapon, and NASA had made a
strategic decision in 1959 that the civilian space program
would, in the near future at any rate, be nonnuclear.
Most of NASA’s rocket engineers were
specialists in chemical propulsion and either did not
understand or were openly opposed to nuclear flight.
Moreover, NASA did not want to attract public criticism
by being seen to favor atomic devices. Orion was
ARPA’s only space interest, and in 1959 it decided it
could no longer support the project on national security
grounds.
Taylor then approached the Air Force, which, after
much persuasion, agreed to support Orion, providing
that some military use could be found for it. However,
Secretary of Defense Robert McNamara was
unconvinced that Orion could become a military
asset, and his department consistently rejected any
increase in funding, effectively limiting it to a feasibility
study. For the project to take off literally, it was
essential that NASA become involved, so Taylor and
James Nance, a General Atomics employee and later
director of the Orion project, made representation to
Marshall Space Flight Center (MSFC). They put forward
a new design that called for the Orion vehicle to
be carried into orbit as a Saturn V upper stage, the
core of the spacecraft being a 90,000-kg “propulsion
module” with a pusher-plate diameter of 10 m (limited
by the diameter of the Saturn). This smaller
design would restrict the specific impulse to between
1,800 and 2,500 seconds—a figure that, though low by
nuclear-pulse standards, still far exceeded those of
other nuclear rocket designs. The proposed shockabsorbing
system had two sections: a primary unit
made up of toroidal pneumatic bags located directly
behind the pusher plate, and a secondary unit of four
telescoping shocks (like those on a car) connecting the
pusher plate assembly to the rest of the spacecraft. At
least two Saturn V launches would have been needed
to put the components of the vehicle into orbit. One
of the missions suggested for this so-called firstgeneration
Orion was a 125-day round-trip to Mars,
involving eight astronauts and about 100 tons of
equipment and supplies. A great advantage of the
nuclear-pulse method is that it offers so much energy
that high-speed, low-fuel-economy routes become
perfectly feasible.
Wernher von Braun, at MSFC, became a supporter
of Orion, but his superiors at NASA were not so
enthusiastic, and the Office of Manned Spaceflight
was prepared only to fund another study. Serious concerns
surrounded the safety of carrying hundreds of
atomic bombs through Earth’s atmosphere. And
there was worse news to come for the project. With
the signing of the nuclear test-ban treaty by the
United States, Britain, and the Soviet Union in
August 1963, Orion, as a military-funded program
calling for the explosion of nuclear devices, became
illegal under international law. The only way it could
be saved was to be reborn as a peaceful scientific