Many people are familiar with the events of May 5, 1961, when US Navy Commander Alan B. Shepard, Jr., became the first American to reach space. Less well known, however, are the events of May 4, 1961. The day before Shepard became America’s first astronaut, two other Navy officers ventured to the edge of space beneath a plastic balloon on the Strato Lab High V flight.

Strato Lab High V was the culmination of a series of flights by Navy aeronauts in the late 1950s and early 60s. The first four flights used a sealed, pressurized capsule. For the final flight, the pilots rode in an open gondola. Commander Malcolm Ross, veteran of the previous Strato Lab High missions commanded this flight. Lt. Commander Victor G. Prather, a medical officer from the Naval Medical Research Institute in Bethesda, Maryland, accompanied him.

Strato Lab High V carried emulsion plates to trap cosmic radiation particles and meteorological instruments, but the main objective of the flight was to test the Navy’s Mark IV full pressure suit. Manufactured by B. F. Goodrich, the Mark IV was the basis for the Project Mercury space suits. Goodrich engineer Russell Colley, who built the first pressure suit ever flown by aviator Wiley Post, helped develop the Mark IV and Mercury suits. Strato Lab High V was the most severe test of the suits conducted up to that time.

The Mark IV comprised two layers: a neoprene rubber impregnated nylon pressure bladder and a nylon cover that protected the bladder and kept it from over-inflating. For space use, the outer layer was aluminized, giving it a silver look. Operational Mark IV suits were green in color. Ross and Prather wore aluminized insulation layers over the standard Mark IV, giving their suits the same appearance as the Mercury space suits. The covering for the Strato Lab High V suits comprised four layers. The outermost was a metalized silicone rubber coated nylon layer over a Trilok spacer, over two more layers of metalized fabric. The ensemble included insulated coveralls, boot covers, hood, and mittens worn over the gloves. Pre-flight tests indicated mobility problems due to the insulated layers, so the insulation below the elbows was removed. Ross and Prather also had electric heated gloves and socks. Ross only turned on his glove heaters briefly, just to verify they worked. Otherwise, he did not use the supplemental heating during the flight. Prather, by comparison, used the heating in both the gloves and socks during substantial portions of the flight. (It should be pointed out that early in the ascent, Prather dropped the insulating muff that was worn over one of the gloves and could not retrieve it.)

The gondola comprised an open framework of aluminum tubing with two side-by-side seats inside. The control panel was on a pedestal between the seats. For temperature control, Ross suggested an arrangement of Venetian blinds on the sides and top of the gondola. One side of the blinds was painted black; the other was covered with aluminized Mylar. By adjusting the blinds to either absorb or reflect sunlight, the pilots could adjust the temperature inside the gondola. The blinds on the front of the gondola could be raised and lowered to provide an unobstructed view.

Ross and Prather took off from the deck of the aircraft carrier USS Antietam at 7:08 AM on May 4, 1961. The balloon envelope was the largest ever launched for a manned flight — 10 million cubic feet! It was made from seven acres of polyethylene and weighed a ton. Fully inflated, it was 300 feet in diameter. The carrier was in the Gulf of Mexico, steaming with the wind so the air speed on the deck was zero.

Ross and Prather endured bitterly cold temperatures, condensation on the visors of their helmets, and communications problems during their ascent. Despite these difficulties, they reached an altitude of 113,740 feet. As later reported by Ross: “In silent awe, we contemplated the supernal loveliness of the atmosphere.” It was 9:47 AM, a little more than two and a half hours after launch.

Ross decided to begin descending almost right away, but encountered problems establishing a steady descent. By 11:15, he and Prather were still floating at 110,000 feet. Ross mentally plotted their descent rate versus time versus oxygen supply and realized they could very well run out of oxygen if they didn’t descend soon. He continued valving helium, finally achieving a descent rate of 500 feet per minute at 90,000 feet. They “won the race with oxygen”, but faced another problem that is common to high altitude balloons – when Ross established a steady descent rate, it was too high. Typically, whatever descent rate a balloon establishes in the stratosphere will double as it passes through the tropopause. Facing a too-fast descent, they quickly began jettisoning ballast in an effort to lighten the aerostat.

Even after dropping all the available ballast, Strato Lab continued to descend too fast, so Ross and Prather began throwing everything else they could overboard, including the radio. By reducing the weight of the gondola, the aeronauts finally brought the descent under control. They even relaxed enough once they were below 7,000 feet to open the visors on their helmets and smoke cigarettes. Preparing to land, Prather cut off the drag rope while Ross threw out the Venetian blinds that had been used to control the temperature in the gondola. When the gondola splashed down in the Gulf, Ross released the balloon. They sat there, floating comfortably, surrounded by the debris they jettisoned during the descent.

The Antietam was just a mile and a half away when they landed in the Gulf of Mexico. With rescue helicopters overhead and the aircraft carrier approaching, Ross and Prather were in a jubilant mood, knowing they had completed all the objectives of the flight. As the helicopter moved into position, it lowered a line to the pilots. Ross went first. Stepping on the hook at the end of the line, he slipped and fell into the water but held onto the line and was hauled aboard the helicopter. When it was Prather’s turn, he also slipped and fell into the water, but was unable to keep hold of the line. Seawater poured into his suit through the open face plate. Rescue divers were quickly in the water, but they were too late — Prather drowned. Prather’s tragic death devastated Ross and marred what was otherwise a brilliant flight.

President John F. Kennedy presented the 1961 Harmon Trophy for Aeronauts to Ross and Prather (posthumously) for this flight.

Written by Greg Kennedy on May 1st, 2013 , Space History

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