Rms delay elements

[aa1961]

Would stacking delay elements against each other work ? Essentially making a slower delay

 

[rcktnut]

No, You can make a longer delay shorter by drilling, but can't make a shorter delay longer by stacking the elements. Longer delays are available for purchase.

 

[aa1961]

No, You can make a longer delay shorter by drilling, but can't make a shorter delay longer by stacking the elements. Longer delays are available for purchase.

Can I ask why that is?

 

[Voyager1]

Would stacking delay elements against each other work ? Essentially making a slower delay

No!
There is only space for one delay element in an RMS motor forward closure. You will need to get a reload with a longer delay time.
Additionally, even if you could fit an extra delay element in, modifying the motor like this might void its certification status.

 

[aa1961]

No!
There is only space for one delay element in an RMS motor forward closure. You will need to get a reload with a longer delay time.
Additionally, even if you could fit an extra delay element in, modifying the motor like this might void its certification status.

So you're saying it would work if you could fit one in.

 

[Voyager1]

I am definitely NOT saying that. It will not fit in!
Clearly you have not assembled an RMS reload if you're asking this question. There is only space for ONE delay grain in the forward closure of the motor.
Here is a section view of an RMS motor. The delay grain is at the front in the forward closure. The propellant grain fills the rest of the motor volume to the rear of the delay grain back to the nozzle; the ejection charge is at the far right on the other side of the delay grain. Where do you imagine you can install a second delay grain?

 

[cerving]

If you need a longer "delay" than what you can get from the motor vendor (usually because your rocket's apogee outruns the maximum delay), that's the time when you should be thinking about going to electronic deployment and ditching motor eject. You can get apogee deployment for as little as $15 (Eggtimer Apogee).

 

[NTP2]

If you need a longer "delay" than what you can get from the motor vendor (usually because your rocket's apogee outruns the maximum delay), that's the time when you should be thinking about going to electronic deployment and ditching motor eject. You can get apogee deployment for as little as $15 (Eggtimer Apogee).

Promoting your product like this, how dare you

Ps i recommend it

 

[aa1961]

I am definitely NOT saying that. It will not fit in!
Clearly you have not assembled an RMS reload if you're asking this question. There is only space for ONE delay grain in the forward closure of the motor.
Here is a section view of an RMS motor. The delay grain is at the front in the forward closure. The propellant grain fills the rest of the motor volume to the rear of the delay grain back to the nozzle; the ejection charge is at the far right on the other side of the delay grain. Where do you imagine you can install a second delay grain?

Well I'm assuming that a longer delay grain is longer physically which means if it's too short you should have room for more delay

 

[aa1961]

If you need a longer "delay" than what you can get from the motor vendor (usually because your rocket's apogee outruns the maximum delay), that's the time when you should be thinking about going to electronic deployment and ditching motor eject. You can get apogee deployment for as little as $15 (Eggtimer Apogee).

I'll check that out thanks

 

[Voyager1]

Well I'm assuming that a longer delay grain is longer physically which means if it's too short you should have room for more delay

I think you should post your questions in the Aerotech open thread.
https://www.rocketryforum.com/threads/aerotech-open-thread.125657/page-255#post-2543043

 

[prfesser]

Would stacking delay elements against each other work ? Essentially making a slower delay

In theory it *could* work but only in the right kind of motor.

The rubber flat gasket and delay o-ring in AT motors are there to keep flame from running between delay and insulator (that would be followed by ignition of the front of the delay, followed by immediate chaos and rapid disassembly of the motor, probably). Those seal elements are at the forward end of the delay. To stack two delays would require some arrangement to keep flame from igniting in the space between the delays.

IF there was an arrangement to keep flame away from that junction, it might work. Unsure as to why one would want to do this, though...

 

[JeffBigg]

What motor exactly do you want to have a longer delay?

 

[shockie]

In theory it *could* work but only in the right kind of motor.

The rubber flat gasket and delay o-ring in AT motors are there to keep flame from running between delay and insulator (that would be followed by ignition of the front of the delay, followed by immediate chaos and rapid disassembly of the motor, probably). Those seal elements are at the forward end of the delay. To stack two delays would require some arrangement to keep flame from igniting in the space between the delays.

IF there was an arrangement to keep flame away from that junction, it might work. Unsure as to why one would want to do this, though...

Perhaps a simple rubber o-ring? Or perhaps a glue ring on the outside top of the lower grain on its edges and the top grain pressed down on the bottom delay with the glue by preventing the outer rings of the propellant burning at the junction. The glue ring would act as a insulator barrier


I'm talking about experimental/tesearch rocket motors not commercial stuff.

 

[prfesser]

Perhaps a simple rubber o-ring? Or perhaps a glue ring on the outside top of the lower grain on its edges and the top grain pressed down on the bottom delay with the glue by preventing the outer rings of the propellant burning at the junction. The glue ring would act as a insulator barrier


I'm talking about experimental/tesearch rocket motors not commercial stuff.

Kosdon and Loki motors use a stack of o-rings on the delay. I expect that a single roring would allow some gas to slide by. The delay elements in this scenario would presumably be rather short, but if they're long enough perhaps two or three o-rings could be placed around each element.

 

[SolarYellow]

Will the first delay light the second delay reliably? Ignition of the first delay is assured by the burning of the propellant grain, which pressurized burning gases are in contact with the delay for anywhere from several tenths to several seconds. Is there any risk that the burning would not propagate across the grain boundary of stacked delays? For example, my understanding (possibly mistaken) of why the AT endburners like H13/H14 must use electronic deployment is that when the propellant grain gets to the end and burns out, the flame is not in contact with the delay face long enough to ensure ignition.

 

[prfesser]

Will the first delay light the second delay reliably? Ignition of the first delay is assured by the burning of the propellant grain, which pressurized burning gases are in contact with the delay for anywhere from several tenths to several seconds. Is there any risk that the burning would not propagate across the grain boundary of stacked delays? For example, my understanding (possibly mistaken) of why the AT endburners like H13/H14 must use electronic deployment is that when the propellant grain gets to the end and burns out, the flame is not in contact with the delay face long enough to ensure ignition.

A delay in intimate contact with another delay should almost certainly ignite in these conditions. The pressure drop, if it's an issue, occurred when the first delay ignited. Close to atmospheric pressure after that.