Facing the Heat Barrier - NASA's History Office

Facing the Heat Barrier: A History of Hypersonics
The concept was born in exuberance. Its planners drew on estimates “that by
1970 the orbital payload accumulated annually would be somewhere between two
million and 20 million pounds.” Most payloads were to run near 10,000 pounds,
thereby calling for a schedule of three flights per day. Still the concept lacked an
important element, for if scramjets were nowhere near the state of the art, at Convair
they were not even the state of the imagination. 53 Space Plane, as noted, used
ramjets with subsonic combustion, installing them in pods like turbojets on a B-52.
Scramjets lay beyond the thoughts of other companies as well. Thus, Northrop
expected to use LACE with its Propulsive Fluid Accumulator (PROFAC) concept,
which also was to cruise in the atmosphere while building up a supply of liquefied
air. Like Space Plane, PROFAC also specified conventional ramjets. 54
But Republic Aviation was home to the highly imaginative Kartveli, with Ferri
being just a phone call away. Here the scramjet was very much a part of people’s
thinking. Like the Convair designers, Kartveli looked ahead to flight to orbit with
a single stage. He also expected that this goal was too demanding to achieve in a
single jump, and he anticipated that intermediate projects would lay groundwork.
He presented his thoughts in August 1960 at a national meeting of the Institute of
Aeronautical Sciences. 55
The XF-103 had been dead and buried for three years, but Kartveli had crafted
the F-105, which topped Mach 2 as early as 1956 and went forward into production.
He now expected to continue with a Mach 2.3 fighter-bomber with enough
power to lift off vertically as if levitating and to cruise at 75,000 feet. Next on the
agenda was a strategic bomber powered by nuclear ramjets, which would use atomic
power to heat internal airflow, with no need to burn fuel. It would match the peak
speed of the X-7 by cruising at Mach 4.25, or 2,800 mph, and at 85,000 feet. 56
Kartveli set Mach 7, or 5,000 mph, as the next goal. He anticipated achieving
this speed with another bomber that was to cruise at 120,000 feet. Propulsion was
to come from two turbojets and two ramjets, with this concept pressing the limits
of subsonic combustion. Then for flight to orbit, his masterpiece was slated for
Mach 25. It was to mount four J58 turbojets, modified to burn hydrogen, along
with four scramjets. Ferri had convinced him that such engines could accelerate
this craft all the way to orbit, with much of the gain in speed taking place while
flying at 200,000 feet. A small rocket engine might provide a final boost into space,
but Kartveli placed his trust in Ferri’s scramjets, planning to use neither LACE nor
ACES. 57
These concepts drew attention, and funding, from the Aero Propulsion Laboratory
at Wright-Patterson Air Force Base. Its technical director, Weldon Worth, had
been closely involved with ramjets since the 1940s. Within a world that the turbojet
had taken by storm, he headed a Nonrotating Engine Branch that focused on ramjets
and liquid-fuel rockets. Indeed, he regarded the ramjet as holding the greater
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First Thoughts of Hypersonic Propulsion
promise, taking this topic as his own while leaving the rockets to his deputy, Lieutenant
Colonel Edward Hall. He launched the first Air Force studies of hypersonic
propulsion as early as 1957. In October 1959 he chaired a session on scramjets at
the Second USAF Symposium on Advanced Propulsion Concepts.
In the wake of this meeting, he built on the earlier SR-89774 efforts and launched
a new series of studies called Aerospaceplane. It did not aim at anything so specific
as a real airplane that could fly to orbit. Rather, it supported design studies and
conducted basic research in advanced propulsion, seeking to develop a base for the
evolution of such craft in the distant future. Marquardt and GASL became heavily
involved, as did Convair, Republic, North American, GE, Lockheed, Northrop, and
Douglas Aircraft. 58
The new effort broadened the scope of the initial studies, while encouraging
companies to pursue their concepts to greater depth. Convair, for one, had issued
single-volume reports on Space Plane in October 1959, April 1960, and December
1960. In February 1961 it released an 11-volume set of studies, with each of them
addressing a specific topic such as Aerodynamic Heating, Propulsion, Air Enrichment
Systems, Structural Analysis, and Materials. 59
Aerospaceplane proved too hot to keep under wraps, as a steady stream of disclosures
presented concept summaries to the professional community and the general
public. Aviation Week, hardly shy in these matters, ran a full-page article in October
1960:
USAF PLANS RADICAL SPACE PLANE
Studies costing $20 million sought in next budget, Earth-to-orbit vehicle
would need no large booster. 60
At the Los Angeles Times, the aerospace editor Marvin Miles published headlined
stories of his own. The first appeared in November:
LOCKHEED WORKING ON PLANE ABLE TO GO INTO ORBIT
ALONE
Air Force Interested in Project 61
Two months later another of his articles ran as a front-page headline:
HUGE BOOSTER NOT NEEDED BY AIR FORCE SPACE PLANE
Proposed Wing Vehicle Would Take Off, Return Like Conventional Craft
It particularly cited Convair’s Space Plane, with a Times artist presenting a view
of this craft in flight. 62
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