I am putting together a specialized kind of inflateable life raft and
need to buy or construct the most compact inflation system possible. 
A compressor will not work in this application and cryogenic storage
or stored gas pressures above 1000 psi are not an option.  The stored
gas, system or material must be stable for long term storage under
normal conditions of temperature etc. found on the deck of a boat.
Production or release of the gas (approximately 20 cubic feet) must be
accomplished within 5 minutes but should not be explosive (such as is
used in air bags in cars).  Materials that produce extreme cold when
expanded are ok.

The options currrently appear to be:

1. Compressed gas (such as carbon dioxide-nitrogen-air-argon etc.),  

2 Liquified gas (ie. propellants such as freon or propane),   

3 Pyrotechnic (ie. burn a solid chemical such as is used in smoke
grenades but not so quickly or with so much heat as to burn the life
raft),

4 Chemical (ie. combine two chemicals that produce a gas). 

What I need to know is, "what system or material will provide the
greatest ratio of expansion from its stored state to its expanded
state.

The most common system uses a cylinder containing carbon dioxide
compressed to 830 psi.  By way of example I would need to know the
ratio of volume of the compressed gas (at 830 psi) to the volume of
the expanded gas (at sea level) and compare it to the ratios of other
gasses and methods.  My need is to compare the four systems, gas,
liquified gas, pyro technical and chemical, and various materials for
stored volume/expanded volume.


A chemical engineer can probably answer this question off the top of
his head based upon the basic properties of materials but I'm stumped.

Good Luck.

This is just the baseline ratio you are looking for.

From the ideal gas law we can use the following equation to compute
the change in volume.  (Also Boyle's Law p'/p = v/v')
Pressure * Volume = n * R * Temperature (in K)
Assuming rafts are about 2 psi and the atmosphere is about 15 psi.
830/(2+15) = 48.8
So you would get about 50 times expansion in volume from the
compressed gas.
Given you wanted 20 cubic feet, that's about .4 cubic feet at 830 psi.
 That number would probably be adjusted up for cold temperatures, high
atmospheric pressure and safety measures.  Also the gas cools with the
initial rapid expansion, but it should quickly reach ambient
temperature.

http://scienceworld.wolfram.com/physics/IdealGasLaw.html
http://216.239.51.100/search?q=cache:eP4UUekkXWkC:www.equipped.com/avraft9.htm+raft+pressure+psi&hl=en&ie=UTF-8
http://www.princeton.edu/~asmits/Bicycle_web/pressure.html

Commercial airbags in vehicles use sodium azide, KNO3 and SiO2.  Gas
generation is initiated with an electric pulse, generating N2 gas. 
Using the ideal gas law

PV=nRT where P=Pressure, V=Volume, n=# of moles of gas, R=gas constant
and T=Temp

one can calculate the amount of reactants required to fill a given
volume with evolved N2.  The easiest way to do this is to have an
abundance of KNO3 and SiO2, and a known amount of sodium azide (which
is good anyways because sodium azide is the most toxic of the bunch). 
The number of moles of sodium azide will turn into the same number of
moles of N2 gas, and you will get more gas from another side reaction
that is taking place, and you can calculate the variables by knowing
the specs on your raft (especially the maximum pressure).

These reactions and their stoichiometry are detailed on:
http://www.chem.uky.edu/courses/che115/airbag.html

Enjoy