[ToddF]

I agree that the most likely proposed use of the helium would be for "balloons" used to block a tall shooter, so let's look at that application...

If the balloons in question were made from elastomeric material, your typical balloon animal balloons, to be inflated the interior pressure must be above 1 atm. If the interior pressure is above 1 atm, they are pneumatics devices. I can see these as being illegal for two reasons. 1) They are not in the list of permissible pneumatics devices in R78. 2) Even if it were argued that a balloon is a tank of variable volume, unless it is a very special balloon, it would not be rated to 125 psi and would violate R76.

However, if the "balloon"s were made of mylar or some other inelastic material, it is easily possible to "inflate" the envelope of the bag with a volume of helium without the interior pressure exceeding 1 atm. If the bag started out flat (internal volume ~0), as gas is added, the interior pressure remains at 1 atm until the internal volume reaches the maximum allowed by the geometry of the bag. At that point, the volume can no longer increase, and adding additional gas requires a rise in pressure (assuming no temperature change). If the bag is made of light enough material, it could "float" before the interior pressure reached 1 atm.

So, it is conceivable that a team could attach to their robot a helium filled mylar envelope with an internal pressure not exceeding 1 atm. As the internal pressure does not exceed 1 atm, it is not a pneumatic device. Since the gas is not stretching an elastomer skin, there is no energy storage. There wouldn't even be a requirement to fill the bag using the robot compressor. You would, however, need to have a very good pressure gauge on your fill station so you could prove that the internal pressure doesn't exceed 1 atm.

Of course, such a bag might not hold up to getting a frisbee shot into it, but that's another problem...