On Mon, Aug 2, 2010 at 12:16 PM, James Perkins <ja...@loowit.net> wrote:
> On 08/02/2010 11:13 AM, I wrote:
>> Learning from the failures of others, what can we gain from this?
>> * On clusters, design the ignition to minimize the chance that two
>> motors can ignite, yanking the ignitors out of the third motor (perhaps
>> make the rocket light it's own ignitors?). I wonder if they would share
>> their ignitor setup so we can learn something from them.
>
> Hm. One part of this is physical contact between the solid rocket fuel and
> the ignitor (being pulled out before ignition). You could help with that by
> physically binding the ignitor's cabling to the rocket, but then if you
> still needed milliseconds more contact to ignite, while the rocket is under
> motion, you really *do* need the ignition power source, current switch, and
> cabling to all live on the rocket or be on a long wire.
>
> I wonder if you only need positive ignition response for a short time before
> it loses value. Perhaps if the ignition components were external to the
> rocket and on a 20m cord or launch rail interlock where it gets disarmed/
> falls off once the rocket clears the launch tower, then you can avoid a
> motor firing up well into flight. Maybe a long ignition wire is best.

A number of orbital rockets use a hold-down mechanism to ensure all
motors are firing properly before liftoff. How feasible would
something like that be for an amateur rocket? For example, could there
be a link that would disconnect under the thrust of all three motors,
but not under the thrust of just two?

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