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First published in 2003 as a volume in the NASA "Monograph in
Aerospace History" series. This study contains photographs and
illustrations.
In 1945 some experts still considered the so-called sound barrier
an impenetrable wall, while winged rocket planes remained largely
relegated to science fiction. But soon a series of unique
rocket-powered research aircraft and the dedicated individuals who
built, maintained, and flew them began to push the boundaries of
flight in aviation's quest to move ever higher, ever faster, toward
the unknown. Beyond Blue Skies examines the thirty-year period
after World War II during which aviation experienced an
unprecedented era of progress that led the United States to the
boundaries of outer space. Between 1946 and 1975, an ancient dry
lakebed in California's High Desert played host to a series of
rocket-powered research aircraft built to investigate the outer
reaches of flight. The western Mojave's Rogers Dry Lake became home
to Edwards Air Force Base, NASA's Flight Research Center, and an
elite cadre of test pilots. Although one of them-Chuck Yeager-would
rank among the most famous names in history, most who flew there
during those years played their parts away from public view. The
risks they routinely accepted were every bit as real as those
facing NASA's astronauts, but no magazine stories or free Corvettes
awaited them-just long days in a close-knit community in the High
Desert. The role of not only the test pilots but the engineers,
aerodynamicists, and support staff in making supersonic flight
possible has been widely overlooked. Beyond Blue Skies charts the
triumphs and tragedies of the rocket-plane era and the unsung
efforts of the men and women who made amazing achievements
possible.
This study represents a means of highlighting the myriad of
technological developments that made possible the safe reentry and
return from space and the landing on Earth. This story extends back
at least to the work of Walter Hohmann and Eugen Sanger in Germany
in the 1920s and involved numerous aerospace engineers at the
National Advisory Committee for Aeronautics (NACA)/NASA Langley and
the Lewis (now the John H. Glenn Research Center at Lewis Field)
and Ames Research Centers. For example, researchers such as H.
Julian Allen and Alfred J. Eggers, Jr., at Ames pioneered
blunt-body reentry techniques and ablative thermal protection
systems in the 1950s, while Francis M. Rogallo at Langley developed
creative parasail concepts that informed the development of the
recovery systems of numerous reentry vehicles. The chapters that
follow relate in a chronological manner the way in which NASA has
approached the challenge of reentering the atmosphere after a space
mission and the technologies associated with safely dealing with
the friction of this encounter and the methods used for landing
safely on Earth.
For a while, it seemed the series of experimental aircraft
sponsored by the U. S. government had run its course. Between the
late 1940s and the late 1970s, almost thirty designations had been
allocated to aircraft meant to explore new flight regimes or
untried technologies. Then, largely, it ended. But there was a
resurgence in the mid- to late1990s, and as we enter the fourth
year of the new millennia, the designations are up to X-50. Many
have a misconception that X-vehicles have always explored the
high-speed and high-altitude flight regimes-something popularized
by Chuck Yeager in the original X-1 and the exploits of the twelve
men that flew the X-15. Although these flight regimes have always
been in the spotlight, many others have been explored by
X-vehicles. The little Bensen X-25 never exceeded 85 mph, and
others were limited to speeds of several hundred mph. There has
been some criticism that the use of X designations has been
corrupted somewhat by including what are essentially prototypes of
future operational aircraft, especially the two JSF demonstrators.
But this is not new-the X-11 and X-12 from the 1950s were going to
be prototypes of the Atlas intercontinental ballistic missile, and
the still-born Lockheed X-27 was always intended as a prototype of
a production aircraft. So although this practice does not represent
the best use of "X" designations, it is not without precedent.
For a while, it seemed the series of experimental aircraft
sponsored by the U.S. government had run its course. Between the
late 1940s and the late 1970s, almost thirty designations had been
allocated to aircraft meant to explore new flight regimes or
untried technologies. Then, largely, it ended. But there was a
resurgence in the mid- to late- 1990s, and as we enter the fourth
year of the new millennia, the designations are up to X-50.
OVERVIEW: This 700+ page book is part of the NASA HISTORY SERIES. A
history of the design and achievements of the high-speed, 1950s-era
X-15 airplane. FROM THE FORWARD BY WILLIAM H. DANA: The X-15 was an
airplane of accelerations. When an X-15 pilot looks back on his
X-15 flights, it is the accelerations he remembers. The first of
these sensations was the acceleration due to B-52 lift, which held
the X-15 at launch altitude and prevented it from falling to Earth.
When the X-15 pilot hit the launch switch, the B-52 lift was no
longer accessible to the X-15. The X-15 fell at the acceleration
due to Earth's gravity, which the pilot recognized as "free fall"
or "zero g." Only when the pilot started the engine and put some
"g" on the X-15 was this sensation of falling relieved. The next
impression encountered on the X-15 flight came as the engine lit,
just a few seconds after launch. A 33,000-pound airplane was
accelerated by a 57,000-lbf engine, resulting in a chest-to-back
acceleration of almost 2 g. Then, as the propellant burned away and
the atmosphere thinned with increasing altitude, the chest-to-back
acceleration increased and the drag caused by the atmosphere
lessened. For a standard altitude mission (250,000 feet), the
weight and thrust were closer to 15,000 pounds and 60,000-lbf at
shutdown, resulting in almost 4-g chest-to-back acceleration. The
human body is not stressed for 4 g chest to back, and by shutdown
the boost was starting to get a little painful. Milt Thompson once
observed that the X-15 was the only aircraft he had ever flown
where he was glad when the engine quit. On a mission to high
altitude (above 250,000 feet), the pilot did not regain any
sensible air with which to execute a pullout until about 180,000
feet, and could not pull 1 g of lift until 130,000 feet. Flying a
constant angle of attack on reentry, the pilot allowed g to build
up to 5, and then maintained 5 g until the aircraft was level at
about 80,000 feet. There was a deceleration from Mach 5 at 80,000
feet to about Mach 1 over the landing runway, and the pilot
determined the magnitude of the deceleration by the use of speed
brakes. This ended the high-g portion of the flight, except for one
pilot who elected to start his traffic pattern at 50,000 feet and
Mach 2, and flew a 360-degree overhead pattern from that starting
point. Flight to high altitude represented about two-thirds of the
199 X-15 flights. Flights to high speed or high dynamic pressure
accounted for the other third, and those flights remained well
within the atmosphere for the entire mission. The pilot of a
high-speed flight got a small taste of chest-to-back acceleration
during the boost (thrust was still greater than drag, but not by
such a large margin as on the high-altitude flights). The
deceleration after burnout was a new sensation. This condition was
high drag and zero thrust, and it had the pilot hanging in his
shoulder straps, with perspiration dripping off the tip of his nose
onto the inside of his face plate. Milt Thompson collected
anecdotes about the X-15 that remain astonishing to this day. Milt
noted that at Mach 5, a simple 20-degree heading change required 5
g of normal acceleration for 10 seconds. Milt also pointed out that
on a speed flight, the (unmodified) X-15-1 accelerated from Mach 5
to Mach 6 in six seconds. These were eye-opening numbers at the
time of the X-15 program. Those of us in the program at flight 190
thought that the X-15 would continue indefinitely. Then, on flight
191, Major Michael J. Adams experienced electrical irregularities
that made the inertial flight instruments unreliable and may have
disoriented him. In any case, at peak altitude (266,000 feet), the
X-15 began a yaw to the right. It reentered the atmosphere, yawed
crosswise to the flight path, and went into a high-speed spin. It
eventually came out of the spin but broke up during the reentry,
killing the pilot.
First published in 2003 as a volume in the NASA "Monograph in
Aerospace History" series. This study contains photographs and
illustrations.
For a while, it seemed the series of experimental aircraft
sponsored by the U.S. government had run its course. Between the
late 1940s and the late 1970s, almost thirty designations had been
allocated to aircraft meant to explore new flight regimes or
untried technologies. Then, largely, it ended. But there was a
resurgence in the mid- to late1990s, and as we enter the fourth
year of the new millennia, the designations are up to X-50. Many
have a misconception that X-vehicles have always explored the
high-speed and high-altitude flight regimes---something popularized
by Chuck Yeager in the original X-1 and the exploits of the twelve
men that flew the X-15. Although these flight regimes have always
been in the spotlight, many others have been explored by
X-vehicles. The little Bensen X-25 never exceeded 85 mph, and
others were limited to speeds of several hundred mph. There has
been some criticism that the use of X designations has been
corrupted somewhat by including what are essentially prototypes of
future operational aircraft, especially the two JSF demonstrators.
But this is not new---the X-11 and X-12 from the 1950s were going
to be prototypes of the Atlas intercontinental ballistic missile,
and the still-born Lockheed X-27 was always intended as a prototype
of a production aircraft. So although this practice does not
represent the best use of "X" designations, it is not without
precedent.
It is a beginning. Over forty-five years have elapsed since the
X-15 was conceived; 40 since it first flew. And 31 since the
program ended. Although it is usually heralded as the most
productive flight research program ever undertaken, no serious
history has been con-assembled to capture its design, development,
operations, and lessons. This monograph is the first step towards
that history. Not that a great deal has not previously been written
about the X-15, because it has. But most of it has been limited to
specific aspects of the program; pilot's stories, experiments,
lessons-learned, etc. But with the exception of Robert S. Houston's
history published by the Wright Air Development Center in 1958, and
later included in the Air Force History Office's Hypersonic
Revolution, no one has attempted to tell the entire story. And the
WADC history is taken entirely from the Air Force perspective, with
small mention of the other contributors. In 1954 the X-1 series had
just broken Mach 2.5. The aircraft that would become the X-15 was
being designed to attain Mach 6, and to fly at the edges of space.
It would be accomplished without the use of digital computers,
video teleconferencing, the internet, or email. It would, however,
come at a terrible financial cost-over 30 times the original
estimate. The X-15 would ultimately exceed all of its original
performance goals. Instead of Mach 6 and 250,000 feet, the program
would record Mach 6.7 and 354,200 feet. And compared against other
research (and even operational) aircraft of the era, the X-15 was
remarkably safe. Several pilots would get banged up; Jack McKay
seriously so, although he would return from his injuries to fly 22
more X-15 flights.Tragically, Major Michael J. Adams would be
killed on Flight 191, the only fatality of the program.
Unfortunately due to the absence of a subsequent hypersonic
mission, aeronautical applications of X-15 technology have been
few. Given the major advances in materials and computer technology
in the 30 years since the end of the flight research program, it is
unlikely that many of the actual hardware lessons are still
applicable. That being said, the lessons learned from hypersonic
modeling, simulation, and the insight gained by being able to
evaluate actual X-15 flight research against wind tunnel and
predicted results, greatly expanded the confidence of researchers.
This allowed the development of Space Shuttle to proceed much
smoother than would otherwise have been possible. In space,
however, the X-15 contributed to both Apollo and Space Shuttle. It
is interesting to note that when the X-15 was conceived, there were
many that believed its space-oriented aspects should be removed
from the program since human space travel was postulated to be many
decades in the future. Perhaps the major contribution was the final
elimination of a spray-on ablator as a possible thermal protection
system for Space Shuttle. This would likely have happened in any
case as the ceramic tiles and metal shingles were further
developed, but the operational problems encountered with the
(admittedly brief) experience on X-15A-2 hastened the departure of
the ablators.
" Access -- no single word better describes the primary concern
of the exploration and development of space. Every participant in
space activities -- civil, military, scientific, or commercial --
needs affordable, reliable, frequent, and flexible access to space.
To Reach the High Frontier details the histories of the various
space access vehicles developed in the United States since the
birth of the space age in 1957. Each case study has been written by
a specialist knowledgeable about the vehicle described and places
each system in the larger context of the history of spaceflight.
The technical challenge of reaching space with chemical rockets,
the high costs associated with space launch, the long lead times
necessary for scheduling flights, and the poor reliability of the
rockets themselves show launch vehicles to be the space program's
most difficult challenge.
The flight campaign for the American space shuttle began on April
12, 1981, with the launch of STS-1 from the Kennedy Space Center,
Florida, and ended on July 21, 2011, with wheels stop of STS-135.
During the 30 years and 135 missions in between, the program
experienced triumphs and tragedies, amazed the world with its
orbital exploits, and was frequently the subject of admiration,
condemnation, pride, and despair. This book provides a detailed
overview of the history of winged spacecraft and the development of
the vehicle we call the "space shuttle," and provides a technical
description of the orbiter, main engines, external tank, and solid
rocket boosters. Two pages are dedicated to each of the 135
missions flown by the American space shuttle, including technical
data, crew names, and photos of each mission. The Challenger and
Columbia accidents are discussed, along with a discussion of what
NASA did to fix the flaws and continue flying. The book concludes
by covering the retirement of the vehicle and the delivery of the
four remaining orbiters to their final display sites.
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