the Minitat program were expected to use a closed-circuit rebreather system-- 

 specif ically, General Electric 's MK-lO-MOD-3 Underwater Breathing System, 

 which permits long excursions (4 to 6 hr) to depths in excess of 1000 FSW 



Test No. 1 of the Minitat series had yielded evidence suggesting that safe 

 ascent to 100 FSW might be made following a 6-hr excursion to 175 FSW when an 

 air equivalent is breathed. There was, however, no available data on the 

 depth to which the Minitat aquanauts might safely ascend on their sorties 

 from the habitat. From a scientific point of view. Test No. 7--the final test 

 that was (and could be) funded- -should logically have been a repetition of 

 Tests No. 5 and 6. But the critical need for data on ascent-excursion limita- 

 tions from 100 FSW forced a modification of the final dive profile to include 

 an ascent simulation. 



Computer computation on allowable excursion limits had suggested that a 6-hr 

 ascent to 70 FSW would be safe. Test No. 7 of this series was accordingly 

 modified to include such an exposure. After saturation, Subject A entered the 

 outer lock of the chamber, which was decompressed to 70 FSW; he exercised over 

 a 4-hr period by lifting a 40-lb weight 1.5 ft 800 times. He then rested for 

 4 hr at 70 FSW, breathing 907o N2 and 107o O2. In the meantime the inner lock 

 of the chamber had also been decompressed to 70 FSW. While Subject A rested, 

 Subject B--breathing the same mixture--duplicated the former's workload. 

 Subject B did not have a rest period, meaning that he was at 70 FSW for only 

 4 hr whereas Subject B was there for 8 hr. They were both again recompressed 

 to 103 FSW, at which pressure they remained for 20 hr; they were then decom- 

 pressed to surface pressure, without incident, according to the 49-hr, 20-min 

 schedule. 



The satisfactory completion of Test No. 7 provided a decompression schedule 

 that could be used in the 14-day chamber experimentation scheduled by the 

 University of Pennsylvania to evaluate the pulmonary, hematopoietic, and 

 central nervous system effects of prolonged exposure to an atmosphere of such 

 nitrogen density as that proposed for the Minitat. The results of that 

 experimentation are reported separately. Suffice to say that the six subjects 

 were safely decompressed according to the 49-hr, 20-min table--meaning that, in 

 all, the table had been tested and proven satisfactory with 12 subjects. The 

 decompression table as approved for the 100-FSW Minitat missions is shown in 

 Appendix C. 



Although funding limitations precluded the testing of more than two subjects in 

 a simulated descent and two in a simulated ascent excursion, the Medical Board 

 accepted the following restrictions in the Minitat excursions: 



1. Descent to 175 FSW on air for 4 hr, with direct ascent 

 to the habitat 



2. Ascent to 75 FSW for 4 hr, either breathing air or a 

 mixture containing no less than 10% 0^ 



3. An obligatory 12-hr interval between any descent excursion 

 and an ascent excursion to 75 FSW 



IX-19 



