_A Tornado Named Stormy_
Harrison (“Stormy”) Storms, Chief Engineer of the Los Angeles
Division, who had sparked the initial management-level interest in
the X-15 project, remained aloof from the day-to-day work on the
airplane. But as Chief Engineer (he had replaced Ray Rice, who moved
up to a Vice President’s slot), the technical responsibility for the
ship was his. When we ran into trouble, he was first to answer the
alarm and bring his high-level prestige and authority to bear. At no
time was he ever more than a few minutes away.
As time passed and all of us began to see the full dimensions of our
tiger, Stormy came around more often. By then, the fall of 1956,
we had moved to larger quarters on the second floor of the main
engineering building. Our team had grown to about sixty-five men, and
every day we leaned more heavily on the various departments of the
plant for aerodynamic, heating, structural data, and other help.
Stormy was short and wiry, 41 years old, a native of Chicago. As
a young boy he had developed an obsession for aircraft through
contact with model planes. He took a master’s degree in Mechanical
Engineering at Northwestern University and later made advanced
studies in aeronautical engineering at Cal Tech. When the Japanese
attacked Pearl Harbor, Stormy joined North American. A tough,
uncompromising, technical man, and an articulate one as well, Stormy
had fought his way to the top of North American. Although for years
he had lived in the nation’s outdoor playground, Southern California,
Stormy ignored the comforts and luxuries of life. Every waking moment
he devoted exclusively to thinking of new and better ways to make
airplanes.
Stormy naturally became one of the ideal men to lay new proposals
before the military. Thus when the Preliminary Design Section came
up with a new concept, Stormy took it to Washington and pounded the
halls of the Pentagon. He became a master at handling a presentation
because, for one thing, he hated to lose a competition. He was
scrappy, cocky, and confident. Under his direction the Los Angeles
Division all but cornered the market of the future flying Air Force.
Stormy had won the competition for the Air Force’s advanced fighter,
the Mach 3 F-108, and the advanced bomber, the Mach 3 B-70, both of
which would benefit from the X-15’s flight experience. There were no
other advanced combat aircraft in the Air Force inventory.
In the fall of 1956 the X-15 ran into serious trouble, both from
political and technical standpoints. Air Force Captain Mel Apt had
just died in the crash of the final X-2 airplane. The basic cause
was high-speed instability, a weakness in the airplane that was
predicted years before. The loss of the X-2 denied the X-15 program
badly needed flight experience and data in the Mach 3 zone and raised
many new questions about acceptance of high-speed instability. The
loss, in effect, vastly broadened the area which the X-15 would
have to explore. From a political standpoint, it put North American
and the government on the spot. If the X-15 also turned out to be
unstable and crashed as a result of this instability, it might
jeopardize not only all future research airplanes but also the entire
future of manned aircraft. Thus in a twinkling the X-15 became an
enormously important project at North American--indeed throughout
the government and aviation industry--bringing to a climax a problem
that had bothered us for some months.
According to the preliminary design studies and wind-tunnel tests,
the X-15, with its high-swept vertical tail, would be unstable during
certain brief periods of the flight profile. It is impossible to
build an airplane that can fly at six times the speed of sound and
land like a conventional airplane without a compromise somewhere
along the line. We had compromised in the tail. Its shape was not
ideal. After the X-2 crash Stormy moved in like a tornado.
The top members of the X-15 team gathered in his office. Stormy was
emphatic and wasted no words.
“This airplane is going to be directionally stable. One week from now
I want all of you back here with every tail-study you have made on
this configuration. I want the weight analysis, flutter studies, drag
studies, the dive-brake studies, the whole works from A to Z. Bill
Johnston says we have got to add some more tail below the fuselage,
so be thinking about that.”
We were back one week later with the paperwork in hand. Our engineers
had collected data from wind tunnels and other sources on every
conceivable tail shape. Ideally for our purposes, the best was
one that looked like the tail of a ballistic missile, with fins
protruding full length above and below the fuselage. But a fin below
the fuselage conflicted with the rear landing-gear arrangement, the
two skids which we had moved all the way aft to save weight. The
lower fin would stick down below the skids and dig into the ground
and become the world’s fastest plow, as we jokingly called it.
The discussion in Stormy’s office was deeply technical and no joke,
though. We pored over the paper studies, matching weight and drag
against performance, proposing, rejecting, theorizing. The problem
was complicated by a variety of factors. For example, the dive
brakes were attached to the upper tail. According to our design
scheme, to gain the biggest bite in the air the upper tail would
move as a complete unit. Then there was the nagging question of the
shape, or airfoil, of the upper and lower tail sections. Seen from
above in cross-section, a diamond-shaped tail was best because
the air “clung” to it better at low speeds. But at high speeds a
diamond-shaped tail, thick at the middle of the diamond, would add
little but weight to the X-15. Our goal was to conceive a new tail
shape without adding an excess pound.
We were in the midst of discussing a truncated lower tail, one that
would not scrape the ground on landing, when Stormy suddenly exploded:
“Why the hell can’t we simply drop the lower tail in flight, just
before landing? We don’t need it then. It’s during the high-speed,
high-altitude phase that we need it.”
“Drop it? Drop the ventral?” someone asked, startled. “It’s never
been done. How would you drop it?”
“Blow it off with a ballistic charge,” Stormy shot back. “Who cares
if it’s never been done? No one ever built an X-15, did they? This
ventral could have a small parachute to lower it to the ground after
it’s jettisoned. It would cost us only a few pounds.”
We thought that over for a while. It was indeed a startling idea.
But, as we finally concluded, why not?
Next we tackled the airfoil of the tail, batting around the diamond
shape versus other, more conventional shapes. As related, the diamond
was the best approach for the X-15’s low-speed flight, and it would
still have some high-speed advantage. The one problem was that it was
marginally adequate and much too heavy.
“What would happen,” Stormy asked, “if we cut that diamond shape off
in the middle? Slice it right in two. Once the air passes the hump of
the diamond, it has finished its work. It separates from the surface.
The air won’t know it if the rear of the diamond isn’t there. That
might cut the weight of the tail in half.”
He was right. Wind-tunnel studies showed that the air behaved
properly with only half a diamond, as seen in cross-section. We
chopped the diamond in half, with the result that the X-15 in
final form has a tremendous, wedge-shaped upper and lower vertical
stabilizer, about which much ill-informed speculation has been
spread around. It was no more and no less than a new attempt to get
the most tail for the least weight. With this innovation, plus the
droppable lower ventral (also wedge-shaped), the X-15 was supplied a
tail that would make it completely stable in all speed ranges. Thanks
to Stormy’s ingenious mind and courage, it was done despite the
strong objections.
* * * * *
In November of 1956 the design of the X-15 was frozen, and a special
team started work on the mock-up of the airplane. The dummy mock-up
was completed in a frenzy the night before our formal customer
inspection in December, 1956. As I recall it, the painters were up
half the night putting finishing touches on the wood and soft-metal
fuselage. When we saw the “complete airplane” the following day,
squatting behind a walled-off area marked “SECRET,” we were amazed
and proud. All the parts fitted, and to the untrained eye the
airplane in its final shape appeared ready to take off. We had
reached this point, from conceptional design to mock-up inspection,
in twelve months flat. Considering the product we were building, I
believe this must be a record of some kind.
About a hundred customers, including both NACA and Air Force
personnel, came to the North American plant to gawk at and criticize
our tiger. Among these was my old friend and boss, Walt Williams, who
was still running NACA’s High Speed Flight Station. Now that the X-2
had gone by the boards, I could see the eagerness in his face. He
was literally panting to get his hands on the X-15. I might add that
we at North American were equally eager to deliver it to his test
facility.
I escorted Williams about the dummy airplane. His mind was churning
with questions. He, of course, knew about the new tail concept--we
reported all changes or modifications on the X-15 to our customers
immediately, and NACA passed them on to the industry--but when he
saw the rear of the full-scale model for the first time he eyed it
skeptically. I put his mind at rest with a technical dissertation,
flavored with a smattering of North American sales pitch. Williams
poked his head inside the cockpit, shotgunning questions.
No detail, however small, was overlooked in this inspection.
For example, one Air Force officer, after a careful survey
of the instrument panel, said to me: “Scotty, I don’t see a
landing-gear-position-indicator light on the panel. How will you know
for sure if your gear is down?”
“The wiring and gauges for gear-indicator lights, we figured, would
weigh about five pounds. Now when you get right down to it, they
really aren’t necessary. Figure this. You’re coming in dead-stick at
200 miles an hour ready for touchdown. To maintain your air speed
and prevent a high rate of sink near the ground, it’s best not to
put the gear down until the last few seconds. Otherwise, the drag
would be too great. So you pull the gear handle. If the gear doesn’t
come down, you’ve had it. You have no engine power. You can’t take
off and go around again for a second landing. So what good does a
gear-position-indicator light do you?”
All in all, our customers gave us a hearty pat on the back. The
X-15 passed its inspection with flying colors and Charlie Feltz
released the engineering drawings. To be sure, there were many minor
requests for changes. I believe they totaled about ninety-five,
half of which we had anticipated. At the time of the inspection,
in fact, our engineers were busy modifying these items. The only
really big proposal that emerged from the inspection was an idea of
Walt Williams’ that the X-15 engine be designed so that it could
“idle” while the plane was still mated to the mother ship. Williams
wanted this to avoid the prospect of an engine failure after drop.
But that was a problem for RMI, not North American. The engine was a
customer-furnished item.
* * * * *
The one cloud gathering on the X-15 horizon at that point in history
was the rocket engine. Facing unprecedented problems, the thin line
of technicians at RMI had wavered and fallen back. By mock-up time
the XLR-99 engine was six to eight months behind the overall X-15
schedule and, we guessed, destined to drop even further behind
schedule. For all of us on the X-15 team, this turn of events,
inevitable in an advanced technological jump of that order, caused
great concern and loud cries of anguish. We knew that in the end such
a delay would reflect on our own efforts at perfection.
Once again Stormy took the reins. After several prolonged meetings
with our propulsion engineers, we wrote a letter to the Air Force
which loudly rang the alarm. North American again offered to supply
the engine from its Rocketdyne Division. But it was too late. By then
the Air Force was heavily committed to the RMI effort. Contracts had
been let; many millions had been invested in the small company. North
American’s Rocketdyne was still busy supplying engines for Atlas and
Thor, and designing even more powerful rocket engines, and the Air
Force was still opposed to calling upon the division for technical
assistance for the X-15. We would have to sweat it out.
I was considerably put out about the engine delays. The engine was
obviously crucial to the entire project. If it failed, we all failed,
and I in particular failed in the goal of my life. The situation
reached the point where I was no longer invited to attend the
rocket-propulsion meetings. On that one subject I had turned into an
outspoken zealot, and the others soon tired of my needling.