Payload safety working group (PSWG). A working group formed for each NASA Payload with a primary purpose to
(1) ensure a project’s compliance with applicable safety requirements and (2) that the safety risk is identified, understood,
and adequately controlled.
Performance specification. A statement prescribing the particulars of how a component or part is expected to perform
in relation to the system that contains the component or part; includes specific values for range of operation, input, output,
or other parameters that define the component’s or part’s expected performance.
Personnel work platforms. Platforms used to provide personnel access to flight hardware at off-pad processing facilities
as well as at the launch pad; they may be removable, extendible, or hinged.
Pneumatic. Operated by air or other gases under pressure.
Pneumatic test. A test of a pressure vessel or system in which a gas is introduced and pressurized to a designated
level in a manner prescribed in the applicable code. (Reference Paragraph UG-100, ASME Code, Section VIII,
Division 1, or Part 8 Paragraph 8.3, ASME Code, Section VIII, Division 2, and Paragraph 345.5, ASME B31.3.)
Populated area. An outdoor location, structure, or cluster of structures that may be occupied by people; sections of
roadways and waterways that are frequented by automobile and boat traffic are populated areas; agricultural lands, if
routinely occupied by field workers, are also populated areas.
Positive control. The continuous capability to ensure acceptable risk to the public is not exceeded throughout each phase
of powered flight or until orbital insertion.
Power source. (1) A battery; (2) the point of direct current (DC) to alternating current (AC) conversion for capacitor
charged systems.
Pressure component. a component such as lines, fittings, valves, regulators, and transducers in a pressurized system;
normally pressure vessels or pressurized structures are excluded, because of the potential energy contained; they generally
require additional analysis, test and inspection.
Pressure system. Any system above 0 psig that is classified as follows: low pressure, 0 to 500 psi; medium pressure,
501 to 3000 psi; high pressure, 3001 to 10,000 psi; ultra-high pressure, above 10,000 psi. The degree of hazard of a
pressure system is proportional to the amount of energy stored, not the amount of pressure it contains; therefore, low
pressure, high volume systems can be as hazardous to personnel as high pressure systems; see pressurized system.
Pressure vessel. A container that stores pressurized fluids and (1) contains stored energy of 14,240 foot pounds (19,130
joules) or greater based on adiabatic expansion of a perfect gas; or (2) contains gas or liquid which will create a mishap
(accident) if released; or (3) will experience a MOP greater than 100 psia; excluded are special equipment including
batteries, cryostats (or dewars), heat pipes, and sealed containers; or (4) per the ASME definition, summarized briefly;
pressure containers that are integral pumps or compressors, hot water heaters and boilers, vessels pressurized in excess
of 15 psi (regardless of size), and vessels with a cross-sectional dimension greater than 6 inches (regardless of length of
the vessel or pressure).
Pressurized structure. A structure designed to carry both internal pressure and vehicle structural loads; the main
propellant tank of a launch vehicle is a typical example.
Pressurized system. A system that consists of pressure vessels or pressurized structures, or both, and other pressure
components such as lines, fittings, valves, and bellows that are exposed to and structurally designed largely by the acting
pressure; electrical or other control devices required for system operation are not included; a pressurized system is often
called a pressure system; see pressure system.