Payload Container Material Testing and Recommendation

Launching a balloon normally means sending up a container -- often referred to as the "payload box" or "balloon sat" -- housing cameras, trackers, and perhaps other devices or items to be taken to near space.  For novices, payload containers often start as a store-bought product: a Styrofoam ice chest, a soft-sided lunch box, or even a fishing tackle box.  But if you are serious about wanting to climb as high as possible,  you will want to make a custom payload container. It is one of the best ways to eliminate excess weight on your flight train as you can build a box that is just the right size for your equipment. And in turn, it minimizes the amount of lifting gas (e.g., helium) needed, providing for more room for gas expansion in the balloon envelope. The result: a better likelihood of reaching maximum altitude.

Making your own custom payload box can be a very enjoyable project.  To begin such a project, you likely will first want to know the answer to very basic question.  “What is the 'best' material for payload container construction?”  'Best' is defined by materials having:

(1) the lowest weight per area

(2) the highest insulating property

(3) the greatest cushioning for a hard landing, and 

(4) the sturdiest overall construction

1 1/2" Styrofoam, 1/2" Pink Foam Construction Panel, 1/4" Foam Core Board

Four different materials were considered, measured and tested: 

1 ½” medium density “white” Styrofoam 

1" medium density "white" Styrofoam

½” high density “pink” construction grade foam panel

¼” foam core art board

The following table summaries the testing results:

                                        Grams / sq. in.      R-Value      Cush         Constr. Strength     Overall Score

           

1 ½” Styrofoam         .351                5.8        High            High                  8

1” Styrofoam             .234                4.0        Med             High                  9   

½” Pink Panel            .274               3.0        Med             High                  6

¼” Foam Core           .225               1.0         Low             Med                  5

Foam Core: Offers low mass for a given area – coming in at .225 grams per square inch – 36% lighter than 1 ½” “White” Styrofoam.  However, it has little insulting capability against the cold, has doubtful cushioning for a violent crash, and has limited construction strength.  Overall rating: 5 / 10

½” Pink High Density Foam: The high-density construction-grade panel foam is 22% lighter than 1 ½” Styrofoam.  It offers good insulting value for its density – listed as R-3.   But its thickness may not be the best protection in a hard crash.  Its ½” width does makes it a somewhat challenging material for box construction.  Overall rating: 6 /10

1” White Styrofoam: Styrofoam has very low mass per area of the materials considered coming in at .234 grams per square inch.  The 1" thickness offer very good insulating value at R 4.  And the 1" thickness provides good protection for hard landings and offers a nice width for building.  Its major downfall is that it is difficult to find as an off-the-self product, often requiring special order from a retailer.  If you can find it, it is the ideal material-- of the four listed here-- for payload construction.  Overall rating: 9/10

1 ½” White Styrofoam: This material has the heaviest mass per area of those tested, coming in at .351 grams per square inch.  Its thickness benefits the payload in two signifiant ways: It has an insulating R value of 6 and it provides excellent protection of equipment in case of a hard crash. Overall rating is 8/10.