Octagonish small pipelauncher for small rockets or sub-orbitor space vehicles.
Acceleration: 2 seconds at 3 gees, 1/2 second at 2 gees
Acceleration distance: 3 gees: 58.8 meters (speed at this point: 58.8 m/s)
2 gees: 1/2 the 58.8 meters is added the 58.8, plus 2.45 meters: 90.65 meters (297')
Speed at 297': 68.6 m/s (153 mph).
Mass:
8 steel 2' diameter pipes 8 with 6' spacers rough circumference 64'at weld length 300': 276,888 lbs- Pipe (.218"): 132,888 lbs Spacers (.250") 144,000 lbs Spacers are not flat plate steel, rather they curved as though they part of pipe 20' in diameter, then replace eight 2' sections of this pipe with the 2' pipes.
Now, instead steel use a weldable alumimun alloy. Steel spec grav is 7.8 and aluminum is 2.7, giving 95,846 lbs (48 tons) instead of 276,888 lbs.
Now still need a cap and bottom section- these don't weigh much and probably make whole thing about 60 tons.
Displacement: 10 squared times pi= 314.159 cu' per 1' of length
Saltwater weighs 64.08 lbs per cu'
Displacement weight per 1': 20,113 lbs (5 tons)
Add weight of payload, say 30 tons.
Need air column 18' below water line to float, 54' below waterline
to accelerate 3 gees and air pressure inside chamber 24 pisg.
About 1 million dollars to make it. And probably about $200 in air
and fuel per launch. Needs about 500' depth of water.