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History of Research in Space Biology
and Biodynamics
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- - PART V -
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- Aircraft Crash
Forces
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- [65] One of the
less exotic aspects of the biodynamics program-one which has
received only a modest amount of research effort but which has
yielded certain interesting results-has been that related to crash
forces experienced in aircraft accidents. The study of aircraft
crash forces has obviously much in common with the study of
eascape from aircraft. Moreover, the first aeromedical sled runs
on the Holloman high-speed track to deal expressly with a topic
other than escape from aircraft were concerned with aircraft crash
forces. These runs began on 21 April 1955 and lasted through 28
June, overlapping slightly with the earliest of the high-speed
windblast runs by the sled Sonic Wind Number
2.4 Specifically, they aimed to reproduce the combined
vertical and horizontal crash forces encountered in certain types
of forced landings, basing the test configurations on actual crash
data compiled by the National Advisory Committee for Aeronautics.
As stated in one test report,5
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- [66] Pilots of
high angle of attack jet aircraft, such as the Delta Wing F-102,
have incurred back fractures caused by forced landings in which
the tail was dragging the ground at near stalling speed with the
pilot seated in the nose 55 feet beyond the end of the tail, and
18 to 25 feet above the ground. When tail structures catch on
ground obstructions, the nose of the aircraft can be slammed to
the ground viciously with forces estimated at better than 60 g's.
For the protection of pilots, it is necessary to evaluate the
combined effect of the two components by reproducing them on the
deceleration sled.
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- In these tests, an F-102 seat was rigged
to drop vertically seventy inches and decelerate by impinging on a
metal cylinder, while at the same time the entire apparatus,
attached to a rocket sled, was being decelerated horizontally by
water brakes on the high-speed track. In the first full-scale
experiment of 21 April-which followed a series of static tests-an
anthropomorphic dummy was used, sustaining peaks of roughly fifty
g's vertical and twenty-five g's horizontal deceleration.
Subsequently, anesthetized chimpanzees took part in the
experiments. With varying types of protection and no irreversible
injury, they received forces ranging up to sixty g's vertical in
combination with twenty g's horizontal deceleration. Taken as a
whole, the experiments supplied valuable data both on crash forces
as such and on the value of different crash restraints and
energy-absorbing seat cushions. For example, they demonstrated how
the impact of vertical g-forces could be reduced by means of
up-lifting chest and shoulder straps.6
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- Aircraft crash forces have also been
studied on the crash-restraint demonstrator, informally referred
to as Bopper, which is one of the specialized test facilities
established at Holloman solely or primarily for the work of the
Aeromedical Field Laboratory. The original version of the Bopper
was acquired from Northrop Aircraft, Incorporated in March 1955
and was replaced by an improved model a year later. It is a seat
propelled by elastic shock cord along a short, portable stretch of
track; it can impart g-forces of short duration, with magnitude
(on the new model) up to about thirty g's.
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- The Bopper was used in a special study of
subject responses to low-impact aircraft crash forces.
Participants in this test series experienced deceleration on the
Bopper ranging up to twelve g's in aft- and forward-facing
positions, secured with seat belt only. Immediately after
exposure, each subject released the seat belt manually and
proceeded along an aisle to a simulated emergency exit. Subjects
were carefully observed to see how quickly and efficiently they
were able to release the belt and reach the exit-something that
must be executed without delay whenever there is danger of flash
fires breaking out or in the event of a water landing. The results
indicated that responses were slightly better after deceleration
in the backward-seated position, thus supporting a point of view
that Colonel Stapp and many other aeromedical officers had often
urged upon the aviation industry, without much
success.7
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- Although a technical note published on
these Bopper tests related them expressly to an aircraft crash
problem, any data on g-tolerances with seat-belt restraint was
also of interest for automotive crash research. The officer who
directed these tests (together with Colonel Stapp, who was chief
of the entire laboratory from April 1953 to April 1958) was
Lieutenant Sidney T. Lewis, whose primary assignment was task
scientist for Automotive Crash Forces (Task 78507 of Project
7850). Naturally, much of the work performed under the automotive
crash program was applicable in turn to aircraft crash studies.
Similarly, tests have been performed on the Daisy Track, whose
main purpose is basic research on impact forces, in order to
evaluate particular types of aircraft crash harness. Both the
automotive crash program and the operation of the Daisy Track will
be discussed below in greater detail.
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- However, at no time since the F-102
drop-seat experiments has aircraft crash research, as such, been
one of the major activities of the Aeromedical Field Laboratory.
When Project 7850, Biodynamics of Human Factors in Aviation, was
established, it contained a separate Task 78506, entitled
Tolerance to Aircraft Crash Forces; and there was even talk of
staging barrier crashes with jet aircraft on the Holloman
high-speed track. But no such experiments were held, nor did the
aircraft crash program ever have a full-time task scientist. In
March 1958, finally, when Project 7850 was revised to become
Biodynamics of Space Flight, Task 78506 was changed from Aircraft
Crash Forces to Patterns of Deceleration in Space Flight.
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[67] (MISSING PHOTO)
- Drop Seat Used in Aircraft Crash
Experiments on the High-Speed Track
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- [68] The new
version of this task will also be discussed more fully below. Even
now, aircraft crash study will not necessarily be excluded
altogether from the work of Project 7850. Project documentation
indicated that research would be conducted on "dynamic stress
characteristics of the human body" as a factor in "design and
specifications" for both aircraft and space vehicles; and the
project is still interested in "impacts," which in turn include
crash forces.8
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