Mega Red Max deployment issue

[emckee]

Hi folks,

I built a MDRM with my son last year and took it out for a launch. We sent it up on an F52 reload with the standard ejection charge (included with the reload). Launch was beautiful, but the rocket came in ballistic.

Kiddo was very disappointed, as might be expected, but is thankfully still flying.

Upon investigation, it appeared the deployment charge had gone off, but was insufficient to provide enough pressure to kick the NC off. It's possible that the ejection charge didn't go off at all, given how smashed the NC and BT were, but it looked like it had, from what I could tell.

He received another MDRM for Christmas this year and it's nearing completion, so I'm interested in making sure that we don't have a repeat of the earlier maiden flight and lawn dart.

When you fly your MDRM on a hobbyline reload, do you find the included ejection charge is sufficient to pressurize the internal volume of this large (4"!) rocket? Do you augment the charge with extra powder?

I've built many AT reloads, from 24mm up to L3 motors, all without issue (though now I've probably cursed myself). I've never had an assembly issue previously, but can't guarantee that wasn't the cause. I'd like to think that I didn't make a stupid mistake, like gluing the NC in (it wasn't glued in), or something like that, but I'm cautious enough that I want to ensure others don't know something about this kit that I don't.

Appreciate the feedback!

Thanks,
-e

 

[Rex R]

to much dog barf can cause problems probably from over cooling the ejection gasses. a chute protector and or a stuffer tube(to decrease tube volume) would probably be in order.
Rex
*edit*
if the ejection well cap was no longer in place, the charge went off. the only question is when.

 

[TangoJuliet]

I know it doesn't exactly answer your question, but I've only used two AT Single Use G40-7's in mine so far, with no issues at all. I have a Nomex chute protector in mine, no dog barf.

 

[kevinkal]

I've flown only the Estes (AeroTech) G80-7T motors, three of them, with no problems. I tape the nosecone to be snug, not too tight. I have noticed, given the black nosecone paint, that the sun can make a HUGE difference in how tight the nosecone fits. I make absolute certain to double check how tight the nosecone it on AFTER the sun has warmed up the rocket on the pad for a few minutes. Generally.. the nosecone seems to expand more than the body tube and thus it gets tighter.

 

[dr wogz]

I'm taking a bit of a guess here..

But the shape of the NC might be the issue. the ever popular Big daddy suffers from incomplete separation due to the shape of the bottom of the NC. it has a slant on it, which will allow the NC to pop off slightly, and allow the ejection gasses (pressure) to not fully dislodge the NC..

 

[ThirstyBarbarian]

All the Aerotech motors I have flown in my MDRM-based rocket have either been Single-Use or DMS, and the standard charge included with the motors has always been sufficient.

 

[JumpJet]

I would make sure the nose cone fits LOOSE.


John Boren

 

[K'Tesh]

I'm taking a bit of a guess here..

But the shape of the NC might be the issue. the ever popular Big daddy suffers from incomplete separation due to the shape of the bottom of the NC. it has a slant on it, which will allow the NC to pop off slightly, and allow the ejection gasses (pressure) to not fully dislodge the NC..

I really wish Estes would come up with a better design for attaching the nosecone that could undeniably prevent that from happening.

I plan on modifying all of my larger nosecones with this possible issue to fill in the vent/slant if it's going to use a nose pop type of recovery.

 

[kevinkal]

I would make sure the nose cone fits LOOSE.


John Boren

A loose nosecone with the MDRM can and will lead to drag separation right after the motor burns out.

 

[qquake2k]

Don't forget, the nose cone can't be too loose. If it is, it may not build up enough pressure to pop it.

 

[JumpJet]

Has anyone ever seen a Mega Max Nose cone Drag Separate? I don't think this can happen on this model. I know many of you are going to disagree with this statement but I'll have to see it to believe it.


John Boren

 

[rharshberger]

Has anyone ever seen a Mega Max Nose cone Drag Separate? I don't think this can happen on this model. I know many of you are going to disagree with this statement but I'll have to see it to believe it.


John Boren

On the Estes recommended motors most likely not. Probably would only happen on motors the rocket was not originally intended for John, mainly V-max and Warp 9 motors that when combined with nose cone av-bays, would give the nose cone enough inertia that it would allow the airframe to drag seperate, of course both of these possibilities are from mods beyond the original design.

 

[ThirstyBarbarian]

Has anyone ever seen a Mega Max Nose cone Drag Separate? I don't think this can happen on this model. I know many of you are going to disagree with this statement but I'll have to see it to believe it.


John Boren

I think it's pretty unlikely too.

 

[kevinkal]

Has anyone ever seen a Mega Max Nose cone Drag Separate? I don't think this can happen on this model. I know many of you are going to disagree with this statement but I'll have to see it to believe it.


John Boren

On the Estes recommended motors most likely not. Probably would only happen on motors the rocket was not originally intended for John, mainly V-max and Warp 9 motors that when combined with nose cone av-bays, would give the nose cone enough inertia that it would allow the airframe to drag seperate, of course both of these possibilities are from mods beyond the original design.

I think it's pretty unlikely too.

I have seen two youtube videos where it deployed at burnout... drag separation. I'll see if I can find and link them. I want to say he was fly G80-#Ts.

 

[kevinkal]

Here's a link to the video where the Mega Der Red Max appears to suffer drag separation. It was an F50. Look at the fin leading edges.. looks like no sanding done at all.. lots of drag.
Read the first comment below the video:
"Watching your video.. it appears that your nosecone and chute came out immediately after the motor thrust phase stopped.. The deceleration forces probably caused the nose cone and parachute to come out as soon as the thrust stopped. After the thrust stopped, I counted to six and heard a pop noise which I think is the ejection charge firing into the already empty body tube. How tight did you have your nosecone before this launch? (I know it's been over a year since you'd launched this one)"

[video=youtube;3oD2mTwHFXw]https://www.youtube.com/watch?v=3oD2mTwHFXw[/video]

If you don't see the embedded video, here's a link to the video.

 

[JumpJet]

I don't see any video or link!
Is it just me?

 

[TangoJuliet]

It must just be you. I have the link, but I can't watch it due to company restrictions on YouTube.

 

[Rex R]

a mega red with a camera taped to the side is not in a stock configuration.
Rex

 

[ThirstyBarbarian]

Here's a link to the video where the Mega Der Red Max appears to suffer drag separation. It was an F50. Look at the fin leading edges.. looks like no sanding done at all.. lots of drag.
Read the first comment below the video:
"Watching your video.. it appears that your nosecone and chute came out immediately after the motor thrust phase stopped.. The deceleration forces probably caused the nose cone and parachute to come out as soon as the thrust stopped. After the thrust stopped, I counted to six and heard a pop noise which I think is the ejection charge firing into the already empty body tube. How tight did you have your nosecone before this launch? (I know it's been over a year since you'd launched this one)"

[video=youtube;3oD2mTwHFXw]https://www.youtube.com/watch?v=3oD2mTwHFXw[/video]

Interesting video. Maybe it was drag separation. The reason it seems unlikely is that the 4" nose cone itself is very wide and has a lot of drag, and it is relatively light and doesn't have a huge amount of momentum. So you would expect the NC to have a good amount of drag pushing into the airframe, and little momentum to overcome that drag. You would expect drag separation to be an issue with skinny, minimum-diameter type rockets that have a lot of nose weight.

My modified MDRM has extra drag in the form of pods attached to the fins, and it has extra nose weight to balance out the extra weight of the pods and larger motors. So I do keep the nose a bit snug with a wrap of masking tape around the NC shoulder. It's still not very tight. If you pick the rocket up by the nose cone, it does not freely slide out, but you can't stand around holding it like that, and if you give it a little shake, the booster drops off.

Another issue if you fly the rocket very fast to higher altitudes is that pressure can force the nose cone out. It's probably not going to happen on an F50 or G80, but if you fly it to 1500' or 2000' on a fast motor, the rising pressure differential might push the nose cone out until you reach the slope in the shoulder. Then when the ejection charge blows, it will just vent out and not eject the nose cone. To prevent that, drill a 1/8" vent hole in the airframe to allow the pressure to equalize during the boost. It's not big enough to vent the ejection charge, just big enough to equalize pressure. As an added precaution, you can tape the NC in place by using two very small tabs of masking tape --- I tear off a 1/4" to 1/2" piece of tape and put one on each side to tape the nose cone to the airframe. It's enough to hold the NC in place, but the ejection charge easily breaks the tape (like a very weak sheer pin). In fact, if you don't like using the wrap of tape around the NC shoulder, the tape-tab shear pin is probably all you really need.

 

[ThirstyBarbarian]

I don't see any video or link!
Is it just me?

i see an embedded video. Here is the link https://m.youtube.com/watch?v=3oD2mTwHFXw (I'm on my iPad, so that's to the youtube mobile site).

 

[JumpJet]

At Home I see the video just fine. I'm not saying it's not there but I never heard an ejection charge going off. I've seen this same thing happen at our field with several different sizes and shaped rockets over the years. In each case the ejection charge went off early. If another camera took video of this flight from the ground it would be much easier to see what happened.

John Boren