Test Facilities

Medical Laboratory - Pressure Chamber



.
.
.
In 1984, the baro-chamber was put into operation. The baro-chamber enabled us to conduct diving experiments of up to 1000 m of depth (possible pressure of 5 mbar to 70 bar absolute) among other things.  Due to the special configuration of the facility, it is possible to imitate the  working conditions characteristic for offshore diving in the laboratory . In the old facility of the then existing DFVLR-Institute of Flight Medicine, a saturation dive in 220 m of depth was conducted for the first time world-wide in 1966. 

The living-chamber  A is on the ground floor of the research hall: 2.2 m in diameter and 6.6 m total length for the permanent stay of 4 probationers. The sanitary appliances are in the back (wash-basin, showers, toilet).

The man-lock in the front part serves as entrance and as experimentation area. The test subjects reach the transfer chamber B through the sanitary part, which corresponds to a "bell" of offshore facilities in its dimensions. Chamber C (imitates  the open sea when filled with water and serves as another experimentation room when dry)  can be accessed through a hydraulically operated hatch in the basement floor.  All chambers can be operated independently of one another. As the most important partial component, the LSS (LIFE SUPPORT SYSTEM) regulates the temperature, moisture and the 
percentage of O2 in the air. These are interesting parallels to spacecraft, which also require a closed atmospheric circulation

The diving experiments were provisionally concluded with a 40-day HELIOX saturation dive in 615 m.

Apart from the necessary readiness for the underwater training for astronauts and for the treatment of major decompression accidents, since 1991 the scientific work has focused on questions of air and space travel like isolation, altered gas mixtures, the development of space suits, EVA-related problems and activities in great height.


Heliox
Heliox is a mixture of oxygen and helium;  the percentage of oxygen may  - depending on the manner of  use -  be above or below the normal value of 21 %. In diving, helium serves as a replacement for nitrogen, which is responsible for the narcotic effect (rapture of the depth) in great depth.

Helium
is obtained  as a "by-product" from natural gas sources and is - like nitrogen - an inert gas. Helium has a clearly smaller density (= 0,178 g/l) than air (= 1,2 g/l) and the speed of sound amounts to 1017 m/s at 300 K (air 347 m/s).  With speech production, the oscillations of higher frequency that occur in the larynx and are emphasized by resonance in the nasopharyngeal cavity are preferred by helium. The resulting "duck voice" can be compensated only incompletely by the use of an unscrambler (electronic device for speech rectification).

On one hand, this entails a substantial complication of work because the personnel on deck may be unable to understand the diver correctly . On the other hand, the problems in vocal communication between the divers lead to social and psychological problems.  Helium also has a strong cooling-down effect, as its heat conductivity is much higher (=0.143 W/mK) than that of air (=0.024 W/mK). For this reason, a habitable helium atmosphere has to be heated to approx. 32°C  in spite of its lower thermal capacity in order to prevent loss of the diver's body heat.


Contact
eMail - Barokammern
E-Mail: barokammern@dlr.de
URL for this article
http://www.dlr.de/me/en/desktopdefault.aspx/tabid-2011/2949_read-4541/