Kennedy Space Center has developed an aviation/aerospace safety device designed to warn crewmembers of a potentially dangerous or deteriorating cabin pressure condition. About the size of a large pager, the Personal Cabin Pressure Altitude Monitor and Warning System operates independently of other aircraft/spacecraft systems and tracks the pressure conditions of the local environment. The monitor warns (by means of audio, vibratory, and visual alarms) of the impending danger of hypoxia when cabin pressure has fallen to preprogrammed threshold levels. A lighted digital screen displays a text message of the warning and annotates the pressurization condition causing the alarm.

The current model contains a miniature, but highly accurate, pressure transducer. Its readings are further enhanced by employing a collocated

temperature sensor to thermally compensate the device. The unit is microprocessor based and is used to interface the sensors, displays, and alarms as well as operate the embedded code to solve the mathematical algorithm that converts the indicated pressure readings to altitude. Through panel-switch selection, the user can choose the units of the altimeter to be displayed (i.e., feet or meters), the units of temperature (degree Celsius or Fahrenheit), and whether to indicate the altitude above ground level (AGL) or above mean sea level (MSL). When the device is used as an altimeter, the user can also select the current altimeter (pressure) setting for either pressure altitude or indicated altitude display. The user can further choose which set of Federal Aviation Administration (FAA) flight rules the unit is to monitor - either commercial [Federal Aviation Regulation (FAR) Part 121/135 or noncommercial (FAR Part 91)] operations.

Hypoxia is a state of oxygen deficiency in the blood, tissues, and cells sufficient to impair functions of the brain and other organs. Because the partial pressure of oxygen is reduced as altitude increases, hypoxia is a concern to flight crews when flying above 10,000 feet cabin pressure altitude. The symptoms of hypoxia often go unrecognized because the brain is the first organ to be affected. Once hypoxia occurs, it is difficult, and often impossible, for the person to acknowledge the situation or to take corrective action. In the early stages, there is considerable loss of judgment and cognitive ability. Performance can seriously deteriorate within 15 minutes at altitudes

as low as 15,000 feet. The ability to take action is lost in 20 to 30 minutes at 18,000 feet and in 5 to 12 minutes at 20,000 feet. At 35,000 feet, the time of useful consciousness is a mere 30 to 60 seconds.

Throughout aviation history, there have been numerous incidents in which aircraft crewmembers and/or passengers have been incapacitated by hypoxia. The most compromising condition leading to hypoxia is not the immediate and recognizable rapid decompression, but one in which a slow yet significant leak has developed in the pressurized cabin or cockpit of an airplane. With crewmembers and passengers unaware, they may either simply fall asleep or be otherwise unknowingly incapacitated. Though many aircraft are fitted with cabin pressurization, monitoring, and alerting systems, there are situations in which the onboard system fails or is misconfigured, rendering the occupants or crew totally unaware of a deteriorating, low-oxygen environment. Another situation is one in which the pilot either knowingly or unwittingly ventures too high for too long in a nonpressurized aircraft.

The aviation application for the monitor includes monitoring and protection for both scenarios. For pressurized aircraft, the invention provides an independent warning of cabin pressure altitude when a cabin leak or other reason for pressurization loss might go undetected. For nonpressurized aircraft, the monitor tracks the time and altitude profile of the cockpit in accordance with prescribed regulations and provides a warning to the crew when supplemental oxygen is to be used.

Human space operations can also benefit from the innovation in Low-Earth-Orbit (LEO) vehicles such as Space Shuttle, Space Station, and Mir, as well as long-duration interplanetary vehicles and future planetary habitats. The proposed ground-based applications include the Mars simulation chamber at KSC and the various pressure/vacuum test chambers at NASA's Space Flight and Research Centers. Applications in its existing form, beyond aviation and aerospace, include

use as an altimeter and thermometer for mountain climbers and as a barometer and thermometer for meteorological measurements. With the selection of a different pressure transducer and modification to the software, the device could be used to track the pressure, depth, and time profiles in human-tended underwater habitats and hyperbaric chambers.

The cabin pressure monitor has undergone a fast-track development effort in 2000, going from concept to flight demonstrator units in less that 9 months. The flight units were tested in the laboratory, in an altitude chamber where normal ascent and rapid decompression profiles were flown, and in various pressurized and nonpressurized aircraft. The technology was introduced to the public in the summer at the Experimental Aircraft Association (EAA) Airventure 2000 airshow held in Oshkosh, Wisconsin. An industry briefing followed in October with commercialization efforts well underway.

Key accomplishments:

• Developed first- and second-generation working prototypes for general and commercial aviation use.
• Tested demonstrator units in the laboratory, an altitude chamber (including explosive decompression), and a variety of aircraft environments.
• Introduced the unit to the public at the EAA Airventure 2000 air show in Oshkosh, Wisconsin.
• Applied for a NASA patent.
• Held an industry briefing and initiated technology transfer and commercialization efforts.