The first operational capstan partial pressure suits (PPS) were produced in custom sizes for early rocket powered X-Plane test pilots, by the David Clark Company. They produced the T-1 capstan pressure suit in standardized sizes made of nylon cotton twill. It was chamber tested to 32 km and subsequently flown in a variety of high altitude aircraft. The T-1 Capstan suit (5 to 1 ratio), incorporated an anti-G suit, no chest bladder, and came in 12 standardized sizes for fighter aircraft.
By end of World War II studies were underway to develop better anti-G garments for fighter pilots using the inflatable bladder principle. At the same time Dr. James P. Henry of the University of Southern California was experimenting with a new concept in aircrew protection, known as capstan type partial pressure suits. Dr. Henry's partial pressure suit operated by imposing mechanical pressure on the body directly, compressing the abdomen and limbs in the manner of a G-suit through the use of inflatable bladders in the abdominal area and pneumatic tubes (capstans) running along the limbs. The wearer's head was fully enclosed in a tightly fitting, rubber lined fabric hood, the oronasal component of which featured a discrete area in front of the face, fitted with a transparent visor and fed by oxygen delivered through a corrugated rubber hose (the facial assembly of this early helmet has the appearance of full-face, rubberized oronasal chemical and biological respirators in use today).
Although the David Clark Company had been approached initially by Dr. Henry to help develop his suit concept, David Clark anti-G protection contracts for the US government made direct cooperation difficult. Rather, materials and a skilled technical assistant were made available by the company to allow Dr. Henry to continue his development in California. As a result of continued testing, many improvements in the design were suggested. These recommendations ultimately resulted in the David Clark produced T-1 suit, the first standardized mechanical principle type suit authorized for use to protect US Air Force aircrew from the combined effects of depressurization and G forces. The T-1 suit incorporated anti-G protection but no chest bladder. A development variant of the T-1 was the S-2 partial pressure suit, which evolved originally for use in bomber aircraft although it was also used in experimental aircraft test projects. The S-2 suit had no anti-G or chest bladders. In 1951 the US Air Force authorized limited production of the S-2 suit for certain projects, but it was the T-1 suit which figured most prominently in the first high altitude jet and rocket propelled aircraft experiments of the late 40s and early 50s
The original helmet used with the T-1 suit was designated the K-1 helmet. It consisted of a snug, laced nylon hood which was worn with a two-piece, close fitting, two-part white outer shell; a further improvement of the K-1 helmet made use of a substantially larger, one-piece green fiberglass outer shell.