The design goal is to increase the capacity of the launch tube from .5 gallons to 1.0 gallons. There are three ways to do this:

Double the length of the tube (Increase length from 36" to 72")

Double the diameter of the tube (Increase diameter from 2" to 3")

Use both a longer and large diameter tube (2.5" pipe X 54")

Use two longer smaller diameter barrels. (1.5" pipe 54" long)

Parts Design #1 Longer pipe:

Launch tube size is increased from 36 inches to 70 inches.

Item  Qty  Cost  Description 

1 1 52.98 2" Stainless Steel Pipe 72 inches, Sch 10 2 2 6.90 2-1" Reducing Coupler, Ass-Weld, Sch 10 4 1 42.75 1"X36 304L Threaded Stainless Steel Pipe, Sch 40 5 1 11.48 1" 304 Stainless Steel T, Sch40 6 1 15.34 1" 304 Stainless Steel Street, Sch40

Total Cost: $151.01

Parts Design #2:

Launch tube diameter is increased from 2" to 3".

Item Qty Cost Description 1 1 83.56 3" Stainless Steel Pipe 72 inches, Sch 10 2 2 9.38 3-2" Reducing Coupler, Ass-Weld, Sch 10 3 1 6.90 2-1" Reducing Coupler, Ass-Weld, Sch 10 3 1 6.62 2-1.5" Reducing Coupler, Ass-Weld, Sch 10 4 1 41.48 1.5" 304L Stainless Steel Pipe, Sch 10 5 1 31.63 1"X24 304L Threaded Stainless Steel Pipe, Sch 10 6 1 11.48 1" 304 Stainless Steel T, Sch40 7 1 15.34 1" 304 Stainless Steel Street, Sch40

Total Cost: 215.77

Parts Design #3:

Launch tube diameter is increased from 2" to 2.5" and length is increased to 54".

Item Qty Cost Description 1 1 67.64 2.5"X72" Stainless Steel Pipe, Sch 10 2 2 30.67 2.5-1.5" Reducing Coupler, Ass-Weld, Sch 10 3 1 41.48 1.5" 304L Stainless Steel Pipe, Sch 10 4 1 5.80 1.5-1" Reducing Coupler, Ass-Weld, Sch 10 5 1 31.63 1"X24 304L Threaded Stainless Steel Pipe, Sch 10 6 1 11.48 1" 304 Stainless Steel T, Sch40 7 1 15.34 1" 304 Stainless Steel Street, Sch40

Total Cost $234.69

Parts Design #4:

Dual Launch tube deisign.

Item Qty Cost Description 1 2 41.48 1.5X54" Stainless Steel Pipe, Sch 10 2 4 5.80 1.5-1" Reducing Coupler, Ass-Weld, Sch 10 5 1 16.51 1"X12 304L Threaded Stainless Steel Pipe, Sch 10 6 2 11.48 1" 304 Stainless Steel T, Sch40 7 3 15.34 1" 304 Stainless Steel Street, Sch40

Total Cost $ 181.75

Analsys.

Option #1: Increasing the length of the launch tube is the lowest cost solution. The length of the launch tube plus ingnitor is likely to be eight feet though.

Option #2: This is viable, but there are some worries that a larger valve would be needed for this design. Valves larger than 3/4 are very expensive. And stainless steel adds even more cost.

Option #3 The 2.5 inch pipe is an odd size and therefor the fittings cost a great deal more. That pushes the cost of the design up quite a bit. Simply because you then need 2 $30 fittings instead of $6 fittings.

Option #4: Using a dual tube design is interesting. The cost is only slightly more than option #1 but the length is likely to be only six feet. Notably it is cheaper than option #3 by almost 2/3. Though the number of welds is increased quite a bit. However there is no need to bend a 1" diameter pipe as in options #1-3