Thunder God Suborbital History
Fifth in a Series Reviewing Thor Family
by Ed Kyle, Updated 6/17/2009
Thor intermediate range ballistic missiles
(IRBMs) performed a total of 152 suborbital flights from 1957 to 1975, a number that
includes nine previously discussed suborbital Thor-Able flights and three suborbital
Thor-"Delta" ASSET missions described below. Most of the 24 suborbital
launches performed after the IRBM was deactivated in 1963 were performed by retired Thor
missiles that had once stood active in Great Britain.
There were 59 Thor IRBM development launches from Cape Canaveral
pads 17A, 17B, and 18B during the 1957-1960 period. This number does not include
Thor 103, which blew up on its launch pad several minutes before its planned liftoff.
An additional 50 combat training launches occurred from
Vandenberg AFB pads 75-1-1, 75-1-2, 75-2-6, 75-2-7, and 75-2-8 during 1958-1962.
Two Thors flew suborbital "Big Shot" missions from Cape
Canaveral in 1962. They boosted Echo balloons above the atmosphere to test balloon
deployment methods for subsequent Echo orbital launches performed by Thor Delta and Thor
Two-Stage Thor-Delta ASSET Prelaunch
Thors lofted six ASSET (Aerothermodynamic/elastic Structural
Systems Environmental Tests) lifting body reentry experiments on suborbital flights from
the Cape during 1963-65. These were U.S. Air Force missions that evaluated reusable, maneuverable, re-entry vehicle designs that might be able to fly
to a precise landing point on earth. At least one of the ASSET reentry vehicles was
recovered after parachuting to an ocean landing.
Single-stage Thors performed three of the
flights. Two-stage vehicles that used retired Thor first stages topped by what were
essentially Delta second stages performed the other three flights. The final ASSET
launch on February 22, 1965 was the last U.S. Air Force Thor flown from Cape
Eight more Thors were launched from Johnston Island in the
Pacific Ocean as part of Operation Fishbowl during 1962. Operation Fishbowl,
performed in a rush during a gap in U.S. Soviet arms control treaties, seems almost
unbelievable when contemplated more than 45 years after it occurred.
Fishbowl Thor at Johnston Island
Operation Fishbowl aimed to launch and detonate hydrogen bombs at
high altitudes. The program was designed to test high altitude nuclear weapons
effects against ballistic missile reentry vehicles (RVs). The Thors carried
instrumented RVs and "pods" attached to the side of their propulsion sections.
The RVs and pods were released prior to warhead detonation. After reentering,
the RVs floated beneath parachutes to the Pacific and were recovered. The Thors flew
from a pair of tactical launchers (Launch Emplacements 1 and 2) set up near one corner of
the tiny island. During launches, most Johnston Island personnel had to be evacuated
to ships standing offshore.
The tests taught the U.S. about the effects of exoatmospheric
nuclear explosions, both on orbiting satellites and on ground-based communications and
power systems. The project produced dazzling nuclear effects, but it
also suffered a series of disastrous failures that deposited radioactive plutonium
contamination on and around Johnston Island.
The first Fishbowl launch was a successful R&D flight with no
warhead. The second launch, carrying an active warhead, was "lost" by a
defective range safety tracking radar and had to be destroyed 10 minutes after liftoff
even though it probably ascended successfully.
Imagine knowing that a missile with a live, set to be armed
nuclear warhead was flying overhead, out there somewhere, destination unknown. The
missile's potent 400 kiloton W50 thermonuclear warhead, never recovered, is still possibly
"out there" somewhere.
Three subsequent Thors, all carrying nuclear warheads, suffered
propulsion system failures and had to be destroyed by range safety. Two of
those destructions occurred downrange, a minute or more into flight, dropping some
radioactive contamination on and near Johnston Island. The third failure, on July
25, 1962, was a true Cold War disaster.
Bluegill Prime Thor
Burns Before RSO Explosion
Thor 180, the missile for that "Bluegill Prime" shot
attempt, was fitted with a W50 thermonuclear warhead capable of producing a 400 kiloton
explosion. The Thor suffered a stuck propellant valve at ignition, causing a leak
that fed a rapidly expanding fire as it stood on its launch pad. The range safety
officer fired the destruct system, destroying the Thor, the warhead, and the launch
emplacement, which burned for some time.
The emplacement and portions of the island were contaminated with
highly radioactive plutonium spread by the fire and windblown smoke. Despite several
subsequent cleanup efforts, Johnston Atoll, managed by the U.S. Fish and Wildlife Service
since 2000, is still affected by contamination from the Operation Fishbowl launch
Johnston Island Launch Emplacement 1
In the end, Operation Fishbowl only produced three successful
high altitude explosions. One of these, Starfish Prime on July 9, 1962, was a 1.4
megaton explosion, created by a W49 warhead at an altitude of 400 kilometers.
It created a fireball and artificial aurora visible in Hawaii, along with an
electromagnetic pulse that disrupted power and communications as far away as Hawaii.
It also pumped enough radiation into the Van Allen belts to destroy or seriously
degrade seven orbiting satellites.
The final Fishbowl launch carried the "Kingfish" 400
kiloton warhead up to its 98 km detonation altitude. Kingfish was one of the last
above-ground U.S. nuclear tests, because the U.S. and the Soviet Union signed an
atmospheric test ban treaty shortly thereafter.
Eighteen more suborbital Thor launches took place from Johnston
Island, from both pads including a "decontaminated" and rebuilt Launch
Emplacement 1, during the 1964-1975 period. Most were in support of Program 437.
Program 437 turned Thor into an operational antisatellite (ASAT)
weapon system, a capability that was kept top secret for many months even after it was
deployed. The program used modified Thor missiles that had been returned from the
original Great Britain deployment. ASAT Thors were positioned and active at the two
Johnston Island launch pads from 1964 until 1970. They were stored in mothballed
condition at Vandenberg AFB from 1970 until 1975, when any possibility of restoring the
ASAT program was finally terminated. In the end, Thor stood active ASAT duty for
many more years than it had stood active IRBM duty.
A Thor at Johnston Island
The ASAT Thors would have lifted nuclear warheads to
near-intercepts of satellite targets in low earth orbits. The missiles could hit
satellites up to 700 km in altitude using a Mk. 49 nuclear warhead with an 8 km kill
Program 437 test launches did not carry live warheads, but were
steered toward orbiting targets. Targets included spent Agena stages and pieces of
"space junk". Care was taken to avoid even the appearance of aiming toward
a Soviet satellite.
Four of the launches, performed during 1965-66, were part of
Program 437-AP (Advanced Payload), which replaced the warhead with a camera/film return
system and reentry capsule. The suborbital flights were aimed to fly near orbiting
satellites. On three occasions the missions were aimed toward, and apparently
photographed, orbiting Agena stages. One of the flights attempted, and reportedly
failed, to photograph NASA's OAO-1 satellite, which had suffered a power failure shortly
after its launch three months earlier.
A pair of experimental suborbital missions related to Program 437
were performed in 1970, just after the ASAT program had been stood down but before the
Johnston Island launch pads were mothballed. Launch Emplacement 2 was restored to
service briefly to host two ballistic missile defense test launches in 1975. These
"Ballistic Missile Defense Test Target Program" flights provided tracking
targets for U.S. missile defense research. The last of these, performed by Thor 274
on November 5, 1975, was the final suborbital Thor launch.
Though it was the final suborbital Thor, Thor 274 was not the
final launch of a retired Thor ballistic missile. Several would fly toward orbit as
"Thor Burner" rockets.
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