I'm not sure if Richard and I are saying the same thing in two different ways or perhaps we have a different understanding of the question. Just to clarify my answer:
Only plan for one failure.
Back gas only needs to cover the ascent to the first gas switch for two divers or the ascent for one diver to the second gas switch in the event that the deepest deco bottle is unavailable.
Said a different way, in a dive where there is bottom gas, a 70' bottle and a 20' bottle - my back gas should be enough to get two divers to the 70' stop, or enough to get me to my 20' stop in the event of a lost 70' bottle (which ever is greater), and my 70' bottle should be enough to get me to the surface in the event of a lost 20' bottle.
As I understand it - Minimum Gas is the amount of gas needed to complete your next ascent phase on your previous phase gas supply. Rock Bottom is the gas required to get two divers to the next gas supply.
Please correct any misunderstandings I may have.
Hunter
Only plan for one failure.
Back gas only needs to cover the ascent to the first gas switch for two divers or the ascent for one diver to the second gas switch in the event that the deepest deco bottle is unavailable.
Said a different way, in a dive where there is bottom gas, a 70' bottle and a 20' bottle - my back gas should be enough to get two divers to the 70' stop, or enough to get me to my 20' stop in the event of a lost 70' bottle (which ever is greater), and my 70' bottle should be enough to get me to the surface in the event of a lost 20' bottle.
As I understand it - Minimum Gas is the amount of gas needed to complete your next ascent phase on your previous phase gas supply. Rock Bottom is the gas required to get two divers to the next gas supply.
Please correct any misunderstandings I may have.
Hunter