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