282 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1958 
test bed for the Atlas and Titan ICBM’s. The Thor is currently 
undergoing development testing. The first three firings of this mis- 
sile ended in failures; however, the ultimate success of this weapon is 
not questioned. When it is released for operational use, the Strategic 
Air Command will be responsible for its tactical deployment. 
The Jupiter, like the Thor, is a single-stage, intermediate-range bal- 
listic missile. The similarities do not end here. Both vehicles use 
the same engine, and it has been reported that they may also adapt the 
same airframes. This vehicle is estimated to be 50 to 60 feet in length 
and 8 feet in diameter. The Jupiter IRBM, like the Thor, has known 
test failures. The first two failures of the Jupiter test vehicle were 
attributed to sloshing fuel. The third test vehicle was a success and 
flew its prescribed range of 1,500 miles. The Navy had initially spon- 
sored the development of the Jupiter with the Army, but, because of 
special shipboard problems, the Polaris was substituted for the Jupiter 
by the Navy. 
The Polaris is a two-stage, fleet ballistic missile vehicle capable of 
being launched from surface ships or from underwater by special 
submarines. The propulsion system is a solid rocket motor, said to be 
the largest built to date. The motor is housed within a vehicle ap- 
proximately 40 to 50 feet long and 100 inches in diameter. Range is 
given as 800 to 1,500 miles, and the warhead is said to be nuclear. 
It is the opinion of the authors that the sublaunch TIRBM will 
achieve a role of greater strategic significance in the very near 
future. Furthermore, it is believed that the use of the solid-pro- 
pellant motor for this application will come of age and be accepted 
by all services. (It is interesting to note that there is no evidence 
to date that the Soviets have developed a large solid motor for ex- 
treme-range missiles.) 
The United States Air Force has the prime responsibility for 
developing the ICBM. There are two missiles that are currently 
under development in this category—the Atlas and the Titan. 
The Atlas is approximately 100 feet in length and 12 feet in 
diameter. The vehicle is boosted by two 185,000-pound-thrust, 
liquid-propellant engines and sustained by a single 100,000-pound- 
thrust, liquid-propellant engine. The Atlas is known as a “stage- 
and-a-half missile,” ie., “parallel staged,” somewhat similar to the 
British wrap-around technique. At launch all three engines are 
utilized. The vehicle takeoff gross weight is over 200,000 pounds. 
Its maximum range is 5,500 miles, apogee (maximum altitude) about 
800 miles, and reentry velocity approximately 15,000 miles per hour. 
The expected accuracy is 20 miles, using celestial guidance. The 
current status or operational date of the missile is not known, but it 
is expected to be some time after 1960. The first two firings of this 
vehicle in June and September 1957 ended in misfire. The cause has 
