Cruise Missile on E9-4 or 6

[1974_Trident]

Yesterday Mr_Rocketeer and i had a great nearly windless day launching in spite of losing his Nova Payloader in a tree. We got close to a dozen launches in in about four hours and we were both getting tired. Our second favorite school launch field was becoming more populated too.

Two launches in particular need mentioning. A flight of my Estes Big Daddy on E9-4 and Mr_Rocketeer's Estes Hi-Flier XL on E9-6. Both rockets went cruise missile 200 feet after liftoff. Cruise missile flights are cool but I don't like having to chase a rocket over a quarter of a mile on a windless day and both rockets headed to crowded areas. The Big Daddy landed in a parking lot. The Hi-Flier XL landed in the middle of a football game. In both instances the shock cords snapped on ejection and both rockets were recovered UNDAMAGED. I was pleasantly surprised that the football players and spectators thought the arrival of the rocket was really cool and the rocket was moved to the sideline to prevent damage.

This got me thinking; We have had over the past three years five out of six flights on E9-4 and E9-6 engines go cruise missile on us. Until yesterday I thought we were experiencing weather-cocking. I do not expect weather cocking on a windless day. All rockets in question have consistently flown straight up on D-12 3 or 5. I have the spent case from a previous cruise missile flight and the two from yesterday. On close examination I noticed that the nozzle on one E9-4 seems damaged. The clay around the orifice is chipped and close examination shows striation in the chips which look like erosion radiating out from the center. The damage is asymmetrical and suggests to me that the thrust may have been asymmetrical for long enough to turn the flight horizontal. Another E9-4 doesn't have any erosion of the clay nozzle but the residue around the orifice is distributed asymmetrically. The E9-6 from yesterday's Hi-Flier XL flight looks like the orifice is partially clogged with residue. All of the E-9 engines in question were bought about three and a half years ago in the same purchase.

Has anybody here experienced or heard of similar failures of the Estes E9 engines? All of the searches I did on this forum turned up catastrophic failures of similar sized engines but that is not what we have experienced.

 

[GregGleason]

I can offer an alternate theory: the launch weights were near the limits of the E9 (about 7.7 oz) and that there was wind at altitude that you did not detect from the ground.

Below is the D12 and D9 thrust curves as a comparison:





The E9 has a "so-so" punch off the pad, then the sustaining thrust goes below 10 N. The low thrust at this stage of the motor burn does make is susceptible to weather cocking if it hits winds aloft, and possibly setting the rocket into "cruise missile" mode.

But all that said, it is possible that if the nozzle is partially blocked it could cause the rocket to veer.

If the turn was sharp, my guess is that it was due to winds aloft.

Greg

 

[DizWolf]

When I first got back into rocketry I made the mistake of thinking "Hey E is bigger than D!" But the E9's are better suited to trying to go really high in really light rockets, than lifting fat heavy ones. The big daddy I can see going off (i had one go into the trees on an E9-6 on a calm day)...the high flier I would think to be ok...

 

[shreadvector]

Almost all residue on the nozzle is from the delay burn. The thrust portion leaves virtually nothing behind. Delay slag is molten lava looking and in always asymmetrical.

For there to be assetric thrust you need to have bistable and measurable nozzle erosion.

Short fat underpowered models launched with way too short launch rods tend to go horizontal .

Use higher thrust motors like Estes E12 or Aerotech E20.

 

[BEC]

To follow up on one point Fred touched on that was the first thing I thought of: how long a launch rod are you using for these? I'd think 4 feet would be a minimum. I'm more surprised about the HiFlierXL than the Big Daddy. Also, is the launch site surrounded by trees? If so, what seems calm on the ground may not be not all that much higher...

Also...this is why I'm flying E12s rather than E9s in general.

 

[1974_Trident]

Thank you everybody for your responses. Greg, thank you very much for the comparative thrust curves. I am most certainly dealing with a launch rod insufficiency now that you explained this to me. Tomorrow's trip; Home depot for 4' of 1/8" rod.

 

[Zeus-cat]

My Estes Phoenix used to do the same thing about the half time on a D12. As others have suggested switch to D12s, E12s or higher thrust reloadable motors. I really like E9s, but the rocket needs to be light.

 

[ThirstyBarbarian]

I experienced something similar today with an E9.

I have a Maxi Alpha III, and when I launch it on E12 motors in the small local field, I fly it in "Colossus" configuration by adding a 14" payload section to add some weight and keep the altitude down a bit. This generally works pretty well. Today I flew the rocket for the first time on an E9, and it seemed to struggle off the pad and weathercocked into the breeze. It was moving really fast when the chute deployed, and all 6 shroud lines tore out! The rocket fell on the roof of a school, and I was able to get it down later with a bit of paracord and a sand bag. The separated parachute drifted into the neighborhood, and I actually found it in my neighbor's front yard. There was damage to the rocket, but at least I got everything back and can repair it.

I felt like the E9 launch was noticeably slower off the pad. I could see that the rocket kind of did a little shimmy after it left the rod and seemed to waver on which direction it was going to go for a moment. On the E12, the rocket jumped off the pad a lot faster and the flight was straighter. There was something nice about the slow take off and long burn on the E9, but I can't have my rocket doing a cruise missile trick in this neighborhood park. I know some people worry about catos with E12's but I'm personally more concerned about crashes with the E9 than catos with the E12. I'm sticking with the E12's.

Here's a video of both flights today, one on the E12 and one on the E9. Aside from my nephew trying to take some cell phone video of various launches, this is my first attempt at taking a video of one of my launches. My wife was holding the little old point-and-shoot Cannon Elph, and I think she did a pretty good job of keeping the rocket in the frame. This was also my first try at editing video on the Mac. (I'm trying to keep expectations low...) Take a look and see if you can tell a difference in the strength of the two launches and if you can see the wiggle off the rod on the E9.

[video=youtube_share;ma4dklU8rT4]https://youtu.be/ma4dklU8rT4[/video]

Edit: Just noticed I put the wrong date on the video title --- it was 11/17, not 10/17.

 

[Rex R]

oh no. not an E9 for a maxi-alpha 3...from what I've seen that combo has a tendency to not end well.
Big daddy: I built mine mostly stock(internal & external fillets (wood glue), and swapped the lugs for 1/4"), flies well on E18s through F39s. I do use a 5' rod.
Rex

 

[chadrog]

Thank you everybody for your responses. Greg, thank you very much for the comparative thrust curves. I am most certainly dealing with a launch rod insufficiency now that you explained this to me. Tomorrow's trip; Home depot for 4' of 1/8" rod.

You should be using 3/16" minimum.

 

[bill_s]

I've flown many E9s in rockets up to 10.5 oz., never a problem ... 9 oz. is better though and 10 needs a 6' rod at least. At 10oz. a highly overstable rocket in high winds once did get about 70 degrees of weathercocking right off the pad but I still wouldn't call it a cruise missile, in fact it landed downwind of the pad, being even better at drifting than weathercocking.

I've seen a case of nozzle problems (C6) and I don't know if pushing the igniter holder plug in the nozzle too hard could cause it, but seems a good idea to not overdo that.

 

[TopRamen]

I never hear anything good about E Motors. Never. Unless your talking about the Single Use or Reloadable Composites or the new Estes BP 29mm E16s.

 

[bobkrech]

Run a sim. The lift-off velocity is too low with the E9 because the lift-off thrust of an E9 is much less than that of a D12. To get an equivalent lift-off velocity use a 1 foot longer launch rod or switch to an E12 motor.

Bob

 

[ThirstyBarbarian]

I never hear anything good about E Motors. Never. Unless your talking about the Single Use or Reloadable Composites or the new Estes BP 29mm E16s.

I actually love the E12s.

 

[Zeus-cat]

I never hear anything good about E Motors. Never. Unless your talking about the Single Use or Reloadable Composites or the new Estes BP 29mm E16s.

The E9-6 is one of my favorite black powder motors.

 

[CarVac]

I've heard great things about the E75. Never flown one myself (nor seen one fly) but it sounds fun.

 

[shreadvector]

I run the safety check table at our club launches and have observed hundreds and hundreds of Estes black powder E motor flights (E9, E12, E16 and F15).

The only failures have been from the one single batch of E12 motors that has had the date code very clearly posted in thread after thread after thread. Dozens and dozens from all the other date codes have been flawless (and ASTOUNDING) and the E12-0 motors from that date code seem fine as well as I have not seen any failures. And I don't think I saw any failures of the E12-8 either. Very, very rarely have I seen an E9 failure, with most being the 'pop out' of the nozzle with no thrust and sitting there and flaming out the nozzleless bottom of the motor. A tiny percentage has been the more violent "blow-through", but I have not seen a larger precentage of those than I see in D12 or C6 or B6 motors.

Again, if you see hundreds and hundreds of launches, you will see a few motor failures.

So, other than that first batch of E12-4 and E12-6 motors with that one specific date code, I love them.

And we have flown the Maxi-Alpha 3 with an E9-4 motor many times, but we always use either a 3/16" x 5 foot long steel launch rod or a 1/4" x 6 foot long steel launch rod.

Using a short launch rod is irresponsible and dangerous.

I never hear anything good about E Motors. Never. Unless your talking about the Single Use or Reloadable Composites or the new Estes BP 29mm E16s.

 

[TopRamen]

The E9-6 is one of my favorite black powder motors.

Be that as it may, I still hear nothing but bad Stories about them. Just stating a Fact.

 

[shreadvector]

Your "fact" is that you are hearing stories.

I and others have posted actual launch result facts from observing and using dozens/hundreds of them.

Failures are rare. It is annoying when they happen to you or your freinds, but the actual facts are that they are very reliable ooutside of that one specific known batch of E12-4 and E12-6 motors.

Try a bunch yourself and then post the results. The E12 motor is ASTOUNDING. The E16 and F15 are just as ASTOUNDING, but they have a higher average thrust and are larger in diameter (and cost a bit more...).

Be that as it may, I still hear nothing but bad Stories about them. Just stating a Fact.

 

[cerving]

The E9 is a nice long-burn motor for very light rockets, to get a decent thrust/weight ratio (5:1) your rocket needs to weigh no more than about 6.5 oz with the motor installed. Most E-size rockets will weigh significantly over this, which is why they go cruise-missile or even nose-dive. A longer launch rod is really just a band-aid, the E9 just doesn't produce enough thrust for heavier rockets, although it's a killer sustainer motor for a small 2-stager. 5:1 with an E12 will get you to about 8.5 oz, that covers almost all of the Estes 24mm fleet. There WAS an early cato issue with some E12's, almost all of the ones that I have heard of were from the same batch (I had one too), but since then I have not seen any more. Shreadvector is right, give the E12 a try, unless you want to go big and get an Aerotech E20 pack.

 

[JeromeK99]

Your "fact" is that you are hearing stories.

I and others have posted actual launch result facts from observing and using dozens/hundreds of them.

Failures are rare. It is annoying when they happen to you or your freinds, but the actual facts are that they are very reliable ooutside of that one specific known batch of E12-4 and E12-6 motors.

Try a bunch yourself and then post the results. The E12 motor is ASTOUNDING. The E16 and F15 are just as ASTOUNDING, but they have a higher average thrust and are larger in diameter (and cost a bit more...).

I think Fred has mentioned this before and I tend to agree with him...

We all seem to notice failures of E9 & E12 at launches primarily because they are louder and more spectacular than smaller motors. They are just more noticeable. if you pay attention to large numbers of launches, you will see a number of A-C motor mishaps.. they just don't stand out.

I was at a couple of the launches when Fred tested several batches of E12 motors after folks started to complain. Beautiful and spectacular flights! Not one mishap.

Earlier this month I was at the big November ROCstock weekend event. A young LCO was on the mic and in control.. there was a mishap with an E9 that blew through the top on the pad. He made the comment on how typical that was. I just shook my head because there were dozens of good launches that weekend on E powered BP motors. Not to mention many BP mishaps on many other motors. When you launch hundreds of BP motors you are going to have a few failures. The E9 & E12 have gotten a bad reputation for just being bigger and louder than the rest.


Jerome

 

[ThirstyBarbarian]

I agree the E12 motors are astounding. I like flying BT-80 sized rockets that are 3 feet or longer, and these motors with those rockets cross a certain threshold of awesomeness that smaller rockets and motors cannot touch. And in my local field where I like to launch, you really cannot go any bigger.

I also agree that most of the bad reputation of the E12 seems to be rumor that grew out of problems with a single bad batch. I've flown more than a dozen now, and they were all great --- my personal favorite motor! In my opinion, the choice between an E12 and and E9 should not be based on relative risk of cato, but what is the right motor for the given rocket and the given conditions.

Actually, part of what I was doing on the day I made the video I posted was to do a sort of qualitative test of how different E motors would work in my "colossus" sized MAIII. I wanted to compare the Estes E12 and E9 and an Aerotech E20. Unfortunately, my controller cannot light the igniter that comes with the E20, so we did not get to try that one. My conclusion was that the E9 is probably not appropriate for the rocket I was flying under the slightly breezy conditions and with the short rod. I liked the long burn, but I think it would work better in a lighter rocket --- the problem with that is that it might go too high for my local field. I might try the E9 in this rocket again under perfectly still conditions and with a longer rod, but mostly I think I will stick with E12's.

Regarding the rod, my current 3/16" rod is only 3 feet long, so I do need to go longer. My local hardware store sells steel rod in 6 foot lengths. It seemed like the 3/16" rod in 6-foot lengths was kind of flexible and springy. Is there any problem with a rod being TOO long? I could buy one and cut it down to 5 feet, but would that make much difference? The 1/4" rod in 6-foot lengths seemed stiff enough. Maybe the solution is to put 1/4" lugs on everything...

 

[shreadvector]

The correct solution is the simplest one that you mentioned: Use 1/4" lugs on all of your larger and/or slower moving models and get that 1/4" dia by 6' long steel rod. You will be very happy.