Dorothy ‘Dottie’ Lee: Blazing a trail back home
The men returning home from
the Moon at an incredible 25,000
miles per hour faced a blistering reentry into the Earth’s atmosphere
encountering soaring temperatures
of 5,000 degrees Fahrenheit. Death
was but feet away were it not for an
ablative heat shield installed on the
base of the Command Module (CM)
that melted and eroded away as
the heat of atmospheric friction built
up. Many engineers were involved in
designing the heat shield and other
systems that would bring each crew
home safely. Dorothy Lee was one
such engineer specialising in ablative
heat shield technology.
Dottie Lee’s childhood interest in
astrophysics led her to believe early
on that humanity was destined to
and spacecraft stability all of which
informed her later work.
Lee was soon invited to work for
the director of engineering and
development Dr Max Faget, the
famous designer of the Mercury
capsule and who later contributed
to the designs of the Gemini, Apollo
and Space Shuttle spacecraft. As
the only lady working with a team
of male engineers under Faget, the
“human computer with a calculator”
was adopted into this exclusive
engineering club and soon excelled
responsible for her own teams. Then,
on October 4th 1957, Sputnik orbited
the world and everything changed.
NACA was re-tasked from an advisory
would encounter, she and her team
made a series of calculations to
measure the aero-thermodynamic
characteristics
of
an
Apollo
Command Module (CM) at re-entry.
Wind tunnel tests gathered pressure
and heating rate data at varying
angles of attack with the atmosphere.
Along with previous data gathered
and Gemini programs, Lee was then
able to collate the data, punch their
values into a series of cards, and feed
slow process as computers at the
time were in their infancy. They were
huge, slow and had only a fraction
of the power and portability of an
average phone today. Despite this,
Lee was able to calculate predictions
of the extreme temperatures and
pressure generated from a superorbital speed re-entry. However these
were all still theoretical.
Based
on
Lee’s
predictions,
the ablative heat shield technology
previously used on Mercury and
Gemini spacecraft. This required
materials and techniques as the
Apollo Command Module (CM)
heat shield was much bigger than its
predecessors and would encounter
far greater stresses. Materials such
a new Avcoat epoxy resin was used.
This epoxy novalic resin was created
Dorothy Lee, the “human computer with a calculator” hard at work developing re-entry predictions for Apollo.
Credit: NASA Johnson Space Center
reach the Moon. As an alumnus of
Randolph-Macon Women’s College
in Virginia, Lee proved she was a
natural at mathematics and upon
graduation was soon recruited in
1948 to work for NACA (National
Advisory Committee for Aeronautics).
Placed in their PARD (Pilotless
Aircraft Research Division) under
the direction of Langley Research
Centre, she was a “human computer
with a calculator” testing different
from Wallops Island. She explored the
characteristics of blunt nosed and
34
34
body into NASA and funding soon
Lee moved to Houston and the
principles developed on Mercury
were translated onto the Apollo
Program. The earlier work Lee had
spacecraft stability and blunt/
cone shaped spacecraft properties
became essential in predicting the
performance of the ablative Apollo
heat shield, or Thermal Protection
System (TPS) as it was known. Given
the predicted orbital and superorbital velocities Apollo spacecraft
brazed steel structure. This matrix was
bonded to the shell of the CM, where
each honeycomb was painstakingly
inspected. Any defects meant the
resin had to be removed and the
whole process restarted from scratch.
It had to be perfect as any anomalies
in the resin could cost the lives of an
Apollo crew.
Following
Lee’s
theoretical
predictions and the production
of a satisfactory heat shield, four
to approximately 18,000 mph) and
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