Multi-Stage with RMS?

I'm looking at the ability to launch with RMS motors. I've seen the 18mm, 24mm, and 29mm casings. Definitely looking at the ability to use them.

Is there any way to build a two stage rocket that would fly off of RMS motors? Obviously I'd need multiple casings. Just wondering if it's possible without some serious electronics and altimeters. Wondering if they can do the "burn through" like BP motors.

Unlike Estes "black powder" motors which are ignited at the nozzle (bottom) end, - RMS motors start burning from the TOP.

Staging RMS motors requires electronics and igniters.

Really no other way.

As scott said, really need electronics.

Much simpler to cluster them. Not exactly the same effect, but it can be done with no on board electronics.

This video shows how Solid RMS motors ignite (top down) which is why the blow-through won't work. It's also much harder to ignite than black powder motors.

[video=youtube_share;SZgxEdajwdE]https://youtu.be/SZgxEdajwdE[/video]

Well that eliminates LPR multi-stage with RMS. Thanks for the info guys.

Wait. If they burn top to bottom, how does the ejection charge work?

A small delay starts burning at the beginning. It's between the burning motor core and the black powder charge. The set burn rate makes it possible to drill out the delay to set how long before ejection.

The delay seals the motor, and when it burns out sets off the ejection charge.

Another thing to consider, as the rockets get bigger they get inherently more dangerous. If a low power 2 stage goes horizontal before lighting the upper stage, when the upper stage does light, it has less mass, and burn rate than a High power rocket would. Therefore it is a good idea, and a mandate at some launch fields, and national organizations, that when staging composite motors, there is some kind of ignition inhibit. This is done in the electronics, so if the rocket is not in a near vertical state, the upper engine does not light. You can see in this video how things could have gone seriously wrong. Start at about 25s in.

https://www.youtube.com/watch?v=1VAkWgbCtA4

I would suggest you find a local club to visit one of their launches, as a learning aide. you will find most rocketeers ready and willing to help.

Apogee components sells small electronic staging timers for just this purpose. You can do some fairly small rockets with these. Agree that altimeters or other staging electronics would likely be too heavy for a smaller rocket.

Later and good luck! OL JR

PS. BTW, as someone else explained, RMS motors use a small delay grain pellet inserted into the forward closure end of the motor that is ignited when the motor ignites, and which burns slowly forward to set off the ejection charge, and is drillable to set the actual delay time... It is VITAL not to get *any* grease or O-ring lubricant on the face of this delay pellet or it will not ignite, thus no ejection charge-- your rocket will streamline in and crash.

mikeyd said:

Another thing to consider, as the rockets get bigger they get inherently more dangerous. If a low power 2 stage goes horizontal before lighting the upper stage, when the upper stage does light, it has less mass, and burn rate than a High power rocket would. Therefore it is a good idea, and a mandate at some launch fields, and national organizations, that when staging composite motors, there is some kind of ignition inhibit. This is done in the electronics, so if the rocket is not in a near vertical state, the upper engine does not light. You can see in this video how things could have gone seriously wrong. Start at about 25s in.

https://www.youtube.com/watch?v=1VAkWgbCtA4

I would suggest you find a local club to visit one of their launches, as a learning aide. you will find most rocketeers ready and willing to help.

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Crikey, hobby rocketry to artillery in 10 seconds.

Does anyone know anything about that launch and the aftermath?

YodaMcFly said:

Crikey, hobby rocketry to artillery in 10 seconds.

Does anyone know anything about that launch and the aftermath?

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Can't help with the details but Midwest Power is an annual multi-day event put on by a club in Iowa. Big rockets and, sometimes, big CATO's.

YodaMcFly said:

Crikey, hobby rocketry to artillery in 10 seconds.

Does anyone know anything about that launch and the aftermath?

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There was a thread about that flight somewhere around here - lots of arguments and "grumpy old men" commentary.

AlnessW said:

There was a thread about that flight somewhere around here - lots of arguments and "grumpy old men" commentary.

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Funny - I saw lots of "good ways to make sure your rocket doesn't do that" commentary.

DizWolf said:

Funny - I saw lots of "good ways to make sure your rocket doesn't do that" commentary.

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Yeah... which usually counts as "ruining my fun" for the yahoos that scream "no harm, no foul" and "how cool was that!"

Later! OL JR

samb said:

Can't help with the details but Midwest Power is an annual multi-day event put on by a club in Iowa. Big rockets and, sometimes, big CATO's.

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Illinois not Iowa... Roughly 100 miles wsw from downtown Chicago. The Wildmans "home" club QCRS is the host - usually last weekend in October.

scsager said:

Illinois not Iowa... Roughly 100 miles wsw from downtown Chicago. The Wildmans "home" club QCRS is the host - usually last weekend in October.

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Yep, the launch site is in Illinios. QCRS is in Iowa, right ?

Kruegon said:

I'm looking at the ability to launch with RMS motors. I've seen the 18mm, 24mm, and 29mm casings. Definitely looking at the ability to use them.

Is there any way to build a two stage rocket that would fly off of RMS motors? Obviously I'd need multiple casings. Just wondering if it's possible without some serious electronics and altimeters. Wondering if they can do the "burn through" like BP motors.

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I've been wrestling with this question off and on for a couple of years. I believe that it is entirely possible to do an Aerotech RMS composite motor to an Estes or Quest black powder upper stage motor, the key problem being the lack of a factory made zero second delay. A non-electronic staging composite booster to composite sustainer would be difficult if not impossible because of the manner of ignition required in core burning composite motors. An end burning composite motor like those made by Apogee Components could probably be made to work.

https://forums.rocketshoppe.com/showthread.php?t=12147

My recent tests begin at post # 25.

tmacklin said:

I've been wrestling with this question off and on for a couple of years. I believe that it is entirely possible to do an Aerotech RMS composite motor to an Estes or Quest black powder upper stage motor, the key problem being the lack of a factory made zero second delay. A non-electronic staging composite booster to composite sustainer would be difficult if not impossible because of the manner of ignition required in core burning composite motors. An end burning composite motor like those made by Apogee Components could probably be made to work.

https://forums.rocketshoppe.com/showthread.php?t=12147

My recent tests begin at post # 25.

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It was done in the first TARC competition which required a 2-stage rocket. The ejection charge from an AT motor with a minimum delay can be used to gap stage an Estes BP motor. The TARC team from St. John's Shrewsbury, MA finished in second place that year doing it IIRC.

Bob

bobkrech said:

It was done in the first TARC competition which required a 2-stage rocket. The ejection charge from an AT motor with a minimum delay can be used to gap stage an Estes BP motor. The TARC team from St. John's Shrewsbury, MA finished in second place that year doing it IIRC.

Bob

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I plan on trying this myself. it seems like a great way to get a staged rocket off the pad. use a high thrust AP motor to get up to speed then use BP to keep it going. the trick will be getting the very short delay timed right. not sure if it's better to drill it out or cut it down and add a spacer.

RKeller said:

I plan on trying this myself. it seems like a great way to get a staged rocket off the pad. use a high thrust AP motor to get up to speed then use BP to keep it going. the trick will be getting the very short delay timed right. not sure if it's better to drill it out or cut it down and add a spacer.

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I think that for most flyers, drilling would be the best option because it doesn't appear to violate any of the rules against motor modification and is already a common practice. However, one must exercise due diligence when drilling because too deep of a hole will result in delay failure 100% of the time with destruction of the air frame. The object is to capture 100% of the motor thrust with as short a delay as possible prior to the communication of fire to a second stage. I offered my videos only as a proof of concept and in the hope that one of the major motor makers might take notice and pursue this concept using the proper techniques and testing.

And for the children.... don't try this at home, you'll put your eyes out! :no:

Just make sure not to drill the delay shorter than recommended by AT. I wonder if using a coarser granulation of BP like say F or FF would be better since the ejection charge would throw larger burning grains toward the BP motor, and it would be slightly less energetic than 4F.

rharshberger said:

Just make sure not to drill the delay shorter than recommended by AT. I wonder if using a coarser granulation of BP like say F or FF would be better since the ejection charge would throw larger burning grains toward the BP motor, and it would be slightly less energetic than 4F.

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Yes on the coarser grain on the ejection charge, but you would still need to fill the fire port hole with FFFF to insure communication of fire. That's why FFFF is used in muzzle loading firearms.

Aerotech specifications for their various delay grains show that an E28-7T delay is 0.438" long whereas an E28-4T is 0.344" long, a difference of 0.094" for a burn rate while not under pressure of 0.0313"/second which is most nearly 1/32"/second.

Thus 0.125" while not under pressure would be consumed in about 4 seconds. (4 x 1/32" = 1/8" or 0.125") Since the total grain is 0.344", subtracting 0.125" (4 seconds) would leave 0.219". That 0.219" while under pressure is consumed in 1.22 seconds according to NAR test results. This also means that the propellant under pressure is burning at the rate of 0.1795"/second, nearly six times as fast as it burns while not under pressure! This is why there must be a sufficient thickness of APCP remaining at burnout or the remnant will fail, and this is why you can't cut it down to zero.

At least that is my understanding of the process.

https://www.aerotech-rocketry.com/u...-b849-b9d11cb57f3d_aerotech_delay_lengths.pdf
https://www.nar.org/pdf/Aerotech/E28.pdf

tmacklin said:

Yes on the coarser grain on the ejection charge, but you would still need to fill the fire port hole with FFFF to insure communication of fire. That's why FFFF is used in muzzle loading firearms.

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I agree with an FFFFg primer being needed for the reason you state, I didn't really think about it that much until you mentioned it, especially since a delay grain doesn't really produce enough pressure inside the casing to force the hot gasses into the charge holder, it makes sense a fine grain powder would need to sit directly on top the delay grain.

Just use the BP charge supplied with the motor. It works just fine.

You can gap stage the sustainer BP motor up to 10"-12" if you vent the void near the base of the sustainer motor. This allows the hot ejection gases to push out the cool air out of the interior void between the booster and the sustainer motors. Without venting it won't ignite reliably.

You can ground test the configuration by placing an igniter and BP in the forward closure of the motor (No reason to burn a booster motor. Simply run the igniter/e-match leads out through the strike hole in the forward closure and out a used nozzle.) Load the BP motor in the sustainer and firmly clamp the sustainer against a support pole several feet above the ground so it won't take off. (Orientation is not important so the rocket can be horizontal if it's easier.) The only requirement is that the booster need to drop or be pushed off. Stand back and fire the ejection charge. The sustainer ignition and the BP charge should separate the booster which will drop away.

Bob

Sure, why waste a perfectly good black powder motor for testing. And yes, venting when gap staging is essential as G. Harry Stine pointed out in his classic book. Actually, I just enjoy watching the ejection charge that is not normally visible in an actual flight. Sort of a Grand Finale when it's too windy too fly! :wink:

Make sure if using an RMS motor to do the lower stage NOT to use the RedCap ejection charge cover since it may block the upper stage motor nozzle when it gets blown off.

As for BP gap staging I have done it many times and it works great as long as you have pressure relief holes between the motors. I like to put them just below the upperstage motor.

rharshberger said:

Make sure if using an RMS motor to do the lower stage NOT to use the RedCap ejection charge cover since it may block the upper stage motor nozzle when it gets blown off.

As for BP gap staging I have done it many times and it works great as long as you have pressure relief holes between the motors. I like to put them just below the upperstage motor.

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If you will re-read my description of my recent tests you will notice that I discarded the red plastic cap and substituted a tiny wad of cotton and piece of perforated masking tape for the purpose of igniting a second stage motor. I did so precisely for the reason you stated. I also reduced the amount of ejection powder as there was essentially no gap in my test scenario. I suppose if the top of the ejection cavity on the booster was in direct contact with the clay nozzle of the sustainer motor, very little ejection material would be necessary to ignite it, although something like cotton or tissue would be still be necessary to form a sacrificial retainer.

Sorry Ted missed that part.

rharshberger said:

Sorry Ted missed that part.

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Oh, no need to apologize. There's a lot to digest in this little saga and I may well have been a bit verbose.