Probably a Dumb ? DD and Motor Delays

[dford]

How do people launch motors that aren't plugged and don't use the motor delay for DD?
I don't want to use the motor delay at all.
How do I turn a "M" delay into a "No Delay" and the motor function correctly?

Everything I research leads me into how to do dual deployment, leaving out the motor delay situation.

 

[grouch]

Grease the bottom of the delay. Good to go. The delay won't light.

 

[dford]

Grease the bottom of the delay. Good to go. The delay won't light.

No way? I never thought of that. Now that I can do, easily.

 

[tim cubbedge]

On CTI motors, I cut open the white paper on top of forward closure and dump out the black powder.
On AT motors, I just don't add any BP when I build it.

 

[rharshberger]

No way? I never thought of that. Now that I can do, easily.

Loss of the delay will also remove the tracking smoke. I leave the delay in normally and fill the ejection charge well with compressed dog barf, then put the redcap or tape over that (make sure not to put use the BP), never had a problem. The motor has depressurized by the time the delay burns through, so the dog barf works to keep any hot bits from pushing up into the body of the rocket.

 

[Kallahan11]

On CTI motors, I cut open the white paper on top of forward closure and dump out the black powder.
On AT motors, I just don't add any BP when I build it.

This is my method as well, this doesn't change the way the motor burns in any way. Is there a reason to using the grease the delay method? Either way you're out a delay grain.

Sometimes with an adjustable motor delay if the delay is longer than needed I will leave it in un-drilled as a backup. This will only pop the drogue though.

 

[Forever_Metal]

This is my method as well, this doesn't change the way the motor burns in any way. Is there a reason to using the grease the delay method? Either way you're out a delay grain.

Sometimes with an adjustable motor delay if the delay is longer than needed I will leave it in un-drilled as a backup. This will only pop the drogue though.

better to slow it a little with drag than to let it return ballistic...

 

[dford]

Loss of the delay will also remove the tracking smoke. I leave the delay in normally and fill the ejection charge well with compressed dog barf, then put the redcap or tape over that (make sure not to put use the BP), never had a problem. The motor has depressurized by the time the delay burns through, so the dog barf works to keep any hot bits from pushing up into the body of the rocket.

Oh geez. This is when the light bulb comes on. "Don't put the black powder in"
That would be the cause of motor eject not the delay itself. Blonde moment.
Good thinking with the dog barf in the red cap. Thank you gentlemen.

 

[mccordmw]

This is my method as well, this doesn't change the way the motor burns in any way. Is there a reason to using the grease the delay method? Either way you're out a delay grain.

Sometimes with an adjustable motor delay if the delay is longer than needed I will leave it in un-drilled as a backup. This will only pop the drogue though.

+1 to that. That's what I did for my L1. The full delay was calculated to be 3 seconds after apogee. Perfect as a backup in case the primary drogue charge at apogee failed and the secondary drogue charge at apogee +1 second also failed. I really really wanted to bring it home in one piece. :-D

 

[Bat-mite]

If the delay is too short, then for sure dump it and save the powder. If the delay is sufficiently long, keep it undrilled and use it as emergency backup charge.

 

[dford]

I'd try utilizing a "long delay" but I sim to a 20+ second ideal delay.
I'll utilize this concept on future DD flights for sure.

 

[dhbarr]

How do people launch motors that aren't plugged and don't use the motor delay for DD?
I don't want to use the motor delay at all.
How do I turn a "M" delay into a "No Delay" and the motor function correctly?

Everything I research leads me into how to do dual deployment, leaving out the motor delay situation.

One argument in favor of ungreased / no powder ( other than tracking smoke ) is a slight reduction in base drag caused by the gas expansion : m04r altitudes!

 

[davdue]

Loss of the delay will also remove the tracking smoke. I leave the delay in normally and fill the ejection charge well with compressed dog barf, then put the redcap or tape over that (make sure not to put use the BP), never had a problem. The motor has depressurized by the time the delay burns through, so the dog barf works to keep any hot bits from pushing up into the body of the rocket.

+1 I do this on all my DD flights.

 

[Onebadhawk]

Loss of the delay will also remove the tracking smoke. I leave the delay in normally and fill the ejection charge well with compressed dog barf, then put the redcap or tape over that (make sure not to put use the BP), never had a problem. The motor has depressurized by the time the delay burns through, so the dog barf works to keep any hot bits from pushing up into the body of the rocket.

+1....
I do this in an attempt to keep the inside of the booster clean....

Teddy

 

[AdAstraPerAspera]

You can also fill the delay well with grease or leave it empty if you don't have dog barf.

If you do want to grease the delay, grease the FWD end, so it will still burn and give you tracking smoke. Of course this isn't possible with CTI 54 and under or Aerotech EZ loads...

 

[K'Tesh]

If the delay is sufficiently long, keep it undrilled and use it as emergency backup charge.

Since the motors I'd be likely to buy include the charge (I'm not looking to go with experimental motors any time soon), I see no advantage not to use it (provided the delay is sufficient). I'd be using it as a backup just in case something in the AV bay F's-up, and the primary and redundant (planned) charges both fail.

 

[AdAstraPerAspera]

You can buy longer delays for Aerotech loads that don't make the motor EX. Aerotech sells them through most of their vendors, though it may be a special order some places.

 

[djs]

I'd be using it as a backup just in case something in the AV bay F's-up, and the primary and redundant (planned) charges both fail.

2 weeks ago I flew a DD rocket, with dual altimeters. I thought "this thing has flown fine before" and didn't put the powder in the ejection charge on the H550 ST motor that I flew. Sure enough, both charges failed at apogee, and the rocket came in hot. Fortunately, the main charge went off, so the rocket didn't hit the ground ballistic, but I still spent 3 hours searching for it, only to find it sticking out of the ground, almost completely destroyed. Moral of the story- take every chance you've got to save the rocket, for safety's sake.

 

[Banzai88]

You can buy longer delays for Aerotech loads that don't make the motor EX. Aerotech sells them through most of their vendors, though it may be a special order some places.

I just started flying AT loads, but don't all the newest loads (in the tubes instead of the bags) come with the longest delays? Are there delays that are LONGER?

As for a regular DD. I try to set up the delay on the motor as backup for the flight computer. In the rare case where I have dual redundant dual deploy, the main is set for apogee, the backup for A+1 second, and the motor for A+2-3 seconds. Since the delay timing on the motor is notional, I try to have several seconds past apogee on it so as not to risk overpressure of the tube in the event that something goes really wrong.

I've had a few ripple fires where the main charge blew at apogee, the back up at +1 second and the motor at +2 seconds and it was so close together in altitude and time that we couldn't tell a difference from the ground.....just one BIG BOOM. Smoke was STILL rolling out of the tube by the time rocket hit the ground! I try to ensure a little more spacing now.

 

[K'Tesh]

2 weeks ago I flew a DD rocket, with dual altimeters. I thought "this thing has flown fine before" and didn't put the powder in the ejection charge on the H550 ST motor that I flew. Sure enough, both charges failed at apogee, and the rocket came in hot. Fortunately, the main charge went off, so the rocket didn't hit the ground ballistic, but I still spent 3 hours searching for it, only to find it sticking out of the ground, almost completely destroyed. Moral of the story- take every chance you've got to save the rocket, for safety's sake.

OUCH!!!