Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page
]]]]] EXPERIMENTS WITH BOMB-PROPELLED SPACESHIP ODELS: [[[[[[[[[[
One Researcher's Personal Account (11/26/88)
by Freeman Dyson
[Freeman J. Dyson is a physicist.]
(From Adventures in Experimental Physics, Beta (1972), pp. 323-6)
[Kindly uploaded by Freeman 10602PANC]
In an article called "Death of a Project" [Science, 9 July
1965, Vol. 149, No. 3680, pp. 141-144], I describe the public and
political history of Project Orion. I do not mention there the
fact that we made bomb-propelled models that actually flew. Here
I describe how the project looked from a personal point of view.
Ted Taylor began the project in 1958, inspired by the belief
that a small group of people with imagination and daring could
build nuclear space-vehicles much cheaper and enormously more
capable than conventional multistage chemical rocket vehicles.
He was enthusiastically supported by Fred de Hoffmann who was
director of the General Atomic laboratory in La Jolla,
California. I found Ted's technical concept convincing and
joined the project in La Jolla when the total number of
employees was three. I worked on it for fifteen months -- the
most exciting and in many ways the happiest of my scientific
life. When I left the project in September 1959, the number of
employees had risen to fifty; we had together solved to our
satisfaction most of the basic problems of vehicle design, the
technical feasibility of our concept had been clearly
established, and the government had decided not to take us
seriously. Wernher von Braun and his chemical rockets had won
the battle for government support, and the pattern of the space
program was set in a way that left no place for us.
In the early days of the project we were all amateurs.
Everybody did a little of everything. There was no division of
the staff into physicists and engineers. I particularly enjoyed
being immersed in the ethos of engineering, which is very
different from that of physics. A good physicist is a man with
original ideas. A good engineer is a man who makes a design that
works with as few original ideas as possible. There are no prima
donnas in engineering. And for a physicist accustomed to the
pressure of personal competition, it was refreshing to work in a
genuinely collective endeavor.
To prove our claims, there were four main jobs to be done.
First there were theoretical calculations of the interaction
between a high-velocity stream of gas from a nuclear bomb and the
massive pusher-plate which covered the bottom of the ship. These
calculations involved many areas of physics: hydrodynamics,
radiation transport, elasticity and chemistry. The crucial
quantity to be calculated was the mass of material boiled off
from the pusher-plate by each explosion. If this mass was less
than a few milligrams per square centimeter, the ship could
survive; otherwise not. The second job was to observe
experimentally the boiling off of material from small areas of
plate exposed to gas jets driven by high explosives. The
explosive jets were able to cover only part of the range of
temperatures, pressures and durations that were of interest for
the full-scale ship. But the experiments provided a detailed
check of the theoretical calculations within the overlapping part
of the range and gave us confidence that the theory had not
overlooked anything essential. The third job was to draw
complete engineering designs of full-scale ships. Here the major
problems were the shock-absorber system, coupling the
pusher-plate to the rest of the structure, and the ejector system
which had to throw out ton-sized bombs at a speed of a few
hundred feet per second with a delivery rate of one or two per
second. Contrary to our original expectations, the ejector
system stretched the state of the engineer's art more severely
than did the shock absorbers. But we arrived at several workable
solutions to both problems.
Flying of Bomb-Propelled Ship Models
The fourth job was to build and fly model ships propelled by
two-pound charges of chemical high explosive. The models were
not true scale models, since no chemical explosive can approach
the ratio of power to mass in a nuclear explosive. The purpose
of the flying models was to demonstrate that a vehicle possessing
in rudimentary form the same engineering components as a
full-scale ship, including pusher-plate and shock absorbers and
ejector system, could be made to function correctly. [The test
system ejected two-pound charges of chemical explosives at a rate
of five-per-second.]
The model flights were the most beautiful part of the whole
project. We had a launch site on a hillside covered with
flowering shrubs and cactus, overlooking the Pacific Ocean. We
usually went out early on Saturday mornings to set up the model
and were ready for the countdown about lunch time. I often
wondered what the Saturday afternoon sailors on the ocean thought
of us, when some weird-looking object rose briefly from the test
stand and blew itself into a thousand pieces. I still keep in my
desk drawer a bag of aluminum splinters which I collected after
one of our test flights, to prove to myself that all these happy
memories are not just dreams.
The last of our flights took place on November 12, 1959, a few
weeks after I had left the project and returned to my more
respectable scientific work at Princeton. Brian Dunne reported
the event to me by letter:
"Wish you could have been with us to enjoy the Point Loma
festivities last Saturday. The Hot Rod flew and flew and flew!
We don't know how high yet. Six charges went off with
unprecedented roar and precision. We think we have it all
recorded with five movie cameras. The chute popped exactly on
the summit and it floated down unscathed right in front of the
blockhouse. We are planning a champagne party for Wednesday."
So ended the romantic days of Orion. When the government
decided not to use nuclear propulsion for the main civilian space
program, our project was turned over to the Air Force. The Air
Force kept it alive for six more years, during which a great deal
of excellent work was done, but there was no more brave talk of
manned expeditions to Mars by 1965, and of sampling the rings of
Saturn by 1970. What would have happened to us if the government
had given full support to us in 1959, as it did to a similar
bunch of amateurs in Los Alamos in 1943? Would we have achieved
by now a cheap and rapid transportation system extending all over
the Solar System? Or are we lucky to have our dreams intact?
* * *
Return to the ground floor of this tower
Return to the Main Courtyard
Return to Fort Freedom's home page