Supersonic?

[ammosmoke]

How is this possible? The burst disk simply blasts into little tiny pieces, freeing the air all at once pretty much. If this iris valve you are talking about is like the iris of an eye, I can see it being very fast, but it still has to open outward, with a narrow escape first off.

[hoastmaster]

the mechanism works with a powder charge used in concrete nail guns
the release time of the iris is faster, discs has to blast into little peises wich means that there is a delay time. physics lesson, to blast something into little peises needs energy, opening something with separate energy source uses none of that energy. Therefor time of energy release is less.

[CannonBall]

Then your actually telling that if u would open a ball valve with ur own hands, that it would be faster than a piston valve....
There is no faster valve then a burst disk it is instant flow.....

[DYI]

Burst disks can open in under .5ms, that's pretty damn fast.
The only iris valves that I have seen are meant to control the flow of powdered solids, it would be very difficult to seal an iris valve, due to the way they are built. This would have to be a custom built, highly reinforced valve, and I can't see a powder charge opening such a heavy mechanism in under .5 ms.

If you really wanted as fast opening as possible, it could be done with much less complexity than the iris valve you describe: Make a two layered burst disk, with high explosive sandwiched between the layers. When you set off the explosive, the disk would be blasted appart even faster than usual. It would work the same way, but wouldn't cost thousands of dollars to build.