Facing the Heat Barrier - NASA's History Office

Facing the Heat Barrier: A History of Hypersonics
Jupiter nose cone. (U.S. Army)
pounds constituted the mix of glass cloth and Micarta plastic that formed the ablative
material. To aid in recovery in the ocean, each nose cone came equipped with a
balloon for flotation, two small bombs to indicate position for sonar, a dye marker,
a beacon light, a radio transmitter—and shark repellant, to protect the balloon from
attack. 65
The first nose-cone flight took place in May. Telemetry showed that the re-entry
vehicle came through the atmosphere successfully and that the ablative thermal protection
indeed had worked. However, a faulty trajectory caused this nose cone to fall
480 miles short of the planned impact point, and this payload was not recovered.
Full success came with the next launch, in August. All three stages again fired,
pushing the nose cone to a range of 1,343 statute miles. This was shorter than the
planned range of Jupiter, 1,725 miles, but still this payload experienced 95 percent
of the total heat transfer that it would have received at the tip for a full-range flight.
The nose cone also was recovered, giving scientists their first close look at one that
had actually survived. 66
In November President Eisenhower personally displayed it to the nation. The
Soviets had stirred considerable concern by placing two Sputnik satellites in orbit,
thus showing that they already had an ICBM. Speaking on nationwide radio and
television, Ike sought to reassure the public. He spoke of American long-range
bombers and then presented his jewel: “One difficult obstacle on the way to producing
a useful long-range weapon is that of bringing a missile back from outer
space without its burning up like a meteor. This object here in my office is the nose
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Nose Cones and Re-entry
cone of an experimental missile. It has been hundreds of miles into outer space and
back. Here it is, completely intact.” 67
Jupiter then was in flight test and became the first missile to carry a full-size nose
cone to full range. 68 But the range of Jupiter was far shorter than that of Atlas. The
Army had taken an initial lead in nose-cone testing by taking advantage of its early
start, but by the time of that flight—May 1958—all eyes were on the Air Force and
on flight to intercontinental range.
Atlas also was in flight test during 1958, extending its range in small steps, but it
still was far from ready to serve as a test vehicle for nose cones. To attain 5,000-mile
range, Air Force officials added an upper stage to the Thor. The resulting rocket, the
Thor-Able, indeed had the job of testing nose cones. An early model, from General
Electric, weighed more than 600 pounds and carried 700 pounds of instruments. 69
Two successful flights, both to full range, took place during July 1958. The
first one reached a peak altitude of 1,400 miles and flew 5,500 miles to the South
Atlantic. Telemetered data showed that its re-entry vehicle survived the fiery passage
through the atmosphere, while withstanding four times the heat load of a Thor
heat-sink nose cone. This flight carried a passenger, a mouse named Laska in honor
of what soon became the 49th state. Little Laska lived through decelerations during
re-entry that reached 60 g, due to the steepness of the trajectory, but the nose cone
was not recovered and sank into the sea. Much the same happened two weeks later,
with the mouse being named Wickie. Again the reentry vehicle came through the
atmosphere successfully, but Wickie died for his country as well, for this nose cone
also sank without being recovered. 70
A new series of tests went forward during 1959, as General Electric introduced
the RVX-1 vehicle. Weighing 645 pounds, 67 inches long with a diameter at the
base of 28 inches, it was a cylinder with a very blunt nose and a conical afterbody for
stability. 71 A flight in March used phenolic nylon as the ablator. This was a phenolic
resin containing randomly oriented one-inch-square pieces of nylon cloth. Light
weight was its strong suit; with a density as low as 72 pounds per cubic foot, it was
only slightly denser than water. It also was highly effective as insulation. Following
flight to full range, telemetered data showed that a layer only a quarter-inch thick
could limit the temperature rise on the aft body, which was strongly heated, to less
than 200ºF. This was well within the permissible range for aluminum, the most
familiar of aerospace materials. For the nose cap, where the heating was strongest,
GE installed a thick coating of molded phenolic nylon. 72
Within this new series of flights, new guidance promised enhanced accuracy and
a better chance of retrieval. Still, that March flight was not recovered, with another
shot also flying successfully but again sinking beneath the waves. When the first
recovery indeed took place, it resulted largely from luck.
Early in April an RVX-1 made a flawless flight, soaring to 764 miles in altitude
and sailing downrange to 4,944 miles. Peak speed during re-entry was Mach 20,
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