William:
I was thinking of more of a slot than a disk, with the wire stretched
under the membrane which would in operation be held against the wire by
the pressure. The wire would heat but not break, melting a line down the
middle of the slot, which would then flap open to give quick opening.
A near-circular wire on a disk would work as well though.
I don't know what kind of timing you could get, but the wire in eg an
ematch has to heat up too, a lot hotter than the melting point of some
suitable plastic.
I was also thinking in UK terms, where anything pyro get caught up when
it meets a lot of red tape.
Talon etc make non-pyro igniters which are fast enough for accurate
firework timing, but they are usually >10W as opposed to the few mW an
ematch needs.
Of course you could go to an exploding bridge wire if you want _really_
fast operation. :)
Peter.
On 09/10/2020 19:18, William Claybaugh wrote:
Peter:
It seems a reasonable enough idea.
The obvious concern is the millisecond timing available from a pyro activated valve: the computer says “go” and it’s gone.
With heating of a plastic disk there would clearly be some time delay before failure of the disk. This might not be much of an issue for separation at apogee but could matter some for other uses.
If I’m going to have to develop an initiator for this valve with the considerable testing that requires, I‘d just as soon have something that can be standardized across multiple other potential uses.
Bill
On Fri, Oct 9, 2020 at 11:46 AM Peter Fairbrother <peter@xxxxxxxxxx <mailto:peter@xxxxxxxxxx>> wrote:
On 09/10/2020 16:03, William Claybaugh wrote:
> David:
>
> Funny, I was just looking at these valves yesterday.
>
> As I've mentioned elsewhere, there is very little space for a
non-axial
> mount of the valve. For that reason I'm thinking I will go to an
> actuated burst disk.
Perhaps a silly idea, but could you use a plastic membrane - it's only
125 psi after all - and a heated wire or metal trace to melt it?
Would be very light, and 32A at 12v would provide a lot of heat...
Peter Fairbrother