Project Strato-Lab was a high-altitude manned balloon program sponsored by the United States Navy during the 1950s and early 1960s. The Strato-Lab program lifted the first Americans into the upper reaches of the stratosphere since World War II. Project Strato-Lab developed out of the Navy's unmanned balloon program, Project Skyhook. The program was established in 1954 and administrated by Commander Malcolm Ross (United States Navy). Malcolm Ross and others developed the program to accomplish research required for the manned rocket program to follow. This program provided biomedical data that was used for subsequent efforts in space. Malcolm Ross launched five numbered flights (Strato-Lab 1 through Strato-Lab 5) as well as other unnumbered flights.
Strato-Lab was developed to allow humans to make observations and perform experiments in the upper reaches of the stratosphere using balloons constructed of a thin layer of polyethylene plastic. These balloons were developed during the earlier Projects Helios and Skyhook by Jean Piccard and Otto C. Winzen. Their purpose had been to reduce the weight of the balloons to a fraction of previously used rubber balloons. The Strato Lab program used both open and pressurized gondolas built by Winzen Research Inc and the balloon program in the Mechanical Division of General Mills, Inc. Strato-Lab built on the earlier programs with goals to obtain fundamental data in the fields of astronomy, astro and atmospheric physics, and human physiology at high altitudes.
The Strato-Lab flights made a number of contributions to the manned space flight program. One set of experiments demonstrated that protons from solar flare activity posed a serious risk to humans working in space. This contributed to developing methods of predicting and monitoring solar flare activity. Strato-Lab also contributed to early astronomical observations above the bulk of the Earth's atmosphere. Secondarily to the scientific objectives of the program, Strato-Lab set a number of records for scientific endeavor and general aeronautics.
The Strato-Lab flights culminated in a record-setting flight on May 4, 1961, by Commander Malcolm Ross and Lieutenant Commander Victor Prather (United States Navy) to test the Navy's Mark IV full-pressure suit. The Mark IV suit overcame problems of weight, bulk, ventilation, air and water tightness, mobility, temperature control, and survival capabilities so well that NASA selected a modified version for use by the Project Mercury astronauts. The May 4 flight was the most severe test of the suit that was ever conducted. The flight set an altitude record of 113,740 feet (34.67 km), lasted 9 hours 54 minutes, and covered a horizontal distance of 140 miles (230 km). The research goals of the flight were successful, but Victor Prather drowned during the helicopter transfer after landing.
For this record ascent, President John F. Kennedy presented the balloonists (Victor Prather, posthumously to his wife) the 1961 Harmon Trophy for Aeronauts. For one day the balloonists held the record for the highest that any American had traveled into space. The Soviet cosmonaut Yuri Gagarin had orbited the Earth almost a month earlier, on April 12, 1961; and the next day, on May 5, Alan Shepard flew a sub-orbital trajectory on the Mercury Redstone rocket.