A less-known aspect of the F-104 Starfighter was its experimental use as a launch platform for small sounding rockets. By using a jet fighter as a first stage, an expensive expendable rocket stage could be dispensed with, and launch location could be chosen pretty much at will. Studies showed that an F-104 launched single-stage Viper sounding rocket should attain 800,000 feet altitude; a two stage Altair should reach 6,000,000 feet (1136 miles).
From about 1958 to 1962, NASA undertook a series of tests to demonstrate the concept. An F-104 that had been modified for air launched weapons testing was used. The aircraft had an extendable launch rack for the MB-1 “Genie” nuclear tipped air-to-air missile; a Sidewinder launch rail was attached to that rack, and was used to hold and launch the sounding rocket. The rocket was a single-stage vehicle based on the Grand Central Rocket Co. Viper I-C solid rocket motor. This rocket was referred to as the ALSOR (Air Launched Sounding Rocket).
Image of F-104 with ALSOR (via NASA)
Image of F-104 with ALSOR (via NASA)
The rocket was produced with two different nose geometries, Model A and Model B. The Model A design was for the launch of a balloon: it would inflate after deployment (using water and isopentante, which would boil in the low pressure environment), and included an aluminized corner reflector inside. The balloon would fall and be measured by radar; atmospheric density could then be measured by careful examination of acceleration profiles.
Photo of a deployed atmospheric density-measuring balloon.
Model A payload section
As for Model B:
The model B vehicle was designed for a classified experimental scanning device that telemetered a continuous signal to ground receivers during a flat – trajectory launch in which maximum range (160 nautical miles) was desired.
The “Viperscan” was a Naval Ordnance Test Station device designed to take infrared images of the surface of the Earth and transmit them to ground station; it was not recoverable. Not much is known about it; it seems like the sort of thing that might have made for a handy fast-reaction recon system. Nowhere near as capable as an SR-71, but probably far cheaper and faster (no film recovery and development, for instance).
Models A and B
Artists impression of F-104 in steep vertical climb launching an ALSOR.
ALSOR mission profile
Data on the five test flights.
The test program demonstrated that the concept of an aircraft-launched sounding rocket was practical. However, the F-104 proved to be temperamental in this role, and apparently the concept was dropped.
This fifty-year-old concept was recently revived by the Star Lab project, which is planned to use an F-104 to launch a suborbital rocket.