E engine in a Semroc Saturn 1B?

[Paul]

First post here--I purchased a Semroc Saturn 1B kit last year (had one from Estes in 1978) and goofed up the motor mount. Semroc sent me a new engine retainer, which I installed. I didn't realize the retainer is 3 3/4 inches long until I put a D 12-3 engine in, and it kept going! Can this model fly safely on an E engine?
Thanks!
Paul

[mojo1986]

I don't know the answer to your question, but if not you could always stick in a 1" spacer ahead of a 'D' engine.

Joe

[barone]

SEMROC doesn't show an E as a recommended motor. It does however show a cluster of four C's that would make an E impulse (two Cs = D, two Ds = E). As long as the E doesn't weigh more than the four C's and it meets the minimum liftoff weight, it should fly.

[ghrocketman]

I would NOT try flying any heavy 4" diameter rocket on an anemic low average thrust Estes SU BP E9....it will not fly safely.
If you want to try an "E" get an RMS24 with an E18W or E28T reload.
A 4xC6-5 cluster is the equivalent of a 36 n-sec E24, and Estes E9 is only 28 n-sec (not even equal to a full 20 n-sec D and a full 10 n-sec C put together) with a very low average thrust.

A D12 will barely fly it but an E9 won't with any reasonable length launch rod (under 8 feet).

Don't risk a nicely built complex kit such as the Semroc S1B on a wimpy Estes E9.

If you doubt this, send an email to Carl at Semroc; I'd bet his answer is the same as mine....DON'T USE AN E9.

[Doug Sams]

First post here--I purchased a Semroc Saturn 1B kit last year (had one from Estes in 1978) and goofed up the motor mount. Semroc sent me a new engine retainer, which I installed. I didn't realize the retainer is 3 3/4 inches long until I put a D 12-3 engine in, and it kept going! Can this model fly safely on an E engine?I am quite experienced in the hobby, but have no experience with this bird, so value this swag in that light.

If you want to use E motors, I would use an Aerotech E18 or similar - something with a little more kick off the rod.

Doug



.

[tbzep]

I think the max thrust of four C6-3's is considerably higher than the max thrust of a single E9. I'll have to check, to make sure. IIRC, the E9's max thrust is about 10N less than a D12.

Ok....just got back from the NAR test data web page....

C6-3 peak thrust 14.09N Four of them would be a bit over 56N peak thrust.

The E9-4 only has a peak thrust of 19.47N.......way under half of a four C6 cluster.


Just for the info, a D12-3 peaks at 29.73N...hey, at least I did remember it was about 10N more than the E9. My memory isn't completely gone. ;)

[Paul]

Thanks for the info!
Paul

[Carl@Semroc]

I would not try it! I did try an SLS Laser-X once on a single E9 and it was VERY sluggish, almost unsafe. It is two ounces lighter than a Saturn 1B. Rocksim says a Saturn needs a 10 foot rod to reach 30MPH with an E9!

[bobschmoot]

dont do it dood.

[chanstevens]

Better bet--use that 1" spacer recommended earlier, but slip an F12 behind it, not a D12. Lots of smoke, and much more enjoyable flight.

E9 would only be an option if you have a good shovel and are looking for an excuse to build another one after the learning experience from building this one.

[barone]

Better bet--use that 1" spacer recommended earlier, but slip an F12 behind it, not a D12. Lots of smoke, and much more enjoyable flight.

.
Aaaarrrrrr......POWER BABY!

[ghrocketman]

I love Chan's comments about the shovel...HILARIOUS ! :p

I don't know too many people that fly LPR/MPR anything from 10' launch rods...most likely any 10' length of 3/16" rod would have SEVERE rodd-whip by the time the rocket clears.

E9's are BAD NEWS for any heavy/large diameter type rocket.
About the biggest thing I like to use them in is the Semroc SLS Aero Dart or one of my 1972 Enerjet Aero Dart Clones.
In an Estes Eliminator they are great...in the Executioner (or anything that size) they are only MARGINAL.
Anything larger, you are looking for mayhem !

LPR/MPR seriously needs a semi-hi-thrust BP "E" that actually has some semblance of load-lifting ability.

I see Estes E9's as having extremely low "utility" value; one can always use a high-avg thrust engine in a light rocket, but the converse is obvoiusly NOT true; that is why I would wish manufacturers would error on the high-thrust side insted of low if they only want to produce one say "E" engine....it would be MUCH more useful.

I'd like to know why the E9 could not be "semi-ported" with a mandrel like the old C5/B8 series to make say an E18 or E20 ?

Because the E9 has such limited utility and a cost only very little less than an RMS24 E18 or E28, i find myself using my RMS24 E's much more often.

[Paul]

I guess I need to learn more about E and up engines. As a BAR, I only have experience with A to D engines. Where can I find more information that will explain these mysteries to me?
Paul

[chanstevens]

Well, a good first place to look regarding the "don't use an E9" issue is the manufacturer's max recommedned liftoff weights by motor. For Estes, that's page 39 in the catalog at http://www.estesrockets.com/assets/downloads/2007estescatalog.pdf. For Aerotech, I am not sure there's a master list anywhere, but it's on the package labels.

You can also get a feel for this looking at thrust curves (published online with NAR or thrustcurve.org). If you're a recent BAR and haven't gotten your bearings yet on modern advances, you might also check out the rocket simulators like Rocksim--they can help you avert disaster like underpowered rockets, wrong delays, etc.

Of course, some of the basics have not changed and are applicable beyond your A-D experience. Each letter doubles the TOTAL impulse (roughly). The number after the letter represents the AVERAGE impulse. Do some basic math, and you can see that if an E has double the impulse of a D, but an E9 has a lower average thrust than a D12, then the D12 has a serious butt-kicking thrust spike advantage over an E9, and it's the thrust spike that gets you off the rod at a safe velocity.

[PaulK]

Agree with Chan, with the caveat that, in my opinion, the max recommended lift off weight of 15oz for an E9-4 is really much too high. That is less than a 2:1 thrust-to-weight ratio. A nice intro to motor selection is found here (click on 'motor selection'):

http://www.info-central.org/index.cgi?propulsion

[ghrocketman]

I think about 9oz would be a reasonable max for the E9-4, and that is only on a low-drag (no BT101 Maxi-Brutes) airframe with a 4+ foot launch rod.

Personally, I don't launch anything over 6oz on an E9-anything as I typically only use 3' rods at my home launch site.

[tbzep]

Just to help folks get a good grasp on things, the E9 peak thrust is more than 2N less than the C11 and only about 5N more than a C6. If you are afraid to launch a rocket with a C11, don't launch it on an E9!

Peak Thrust:

C6-x 14.09N
C11-x 21.73N
D12-x 29.73N
E9-x 19.47N

Just in case we forget....

Four C6-3 cluster: 56.36N peak thrust,
Total impulse 35.28N/s

[chanstevens]

Just to help folks get a good grasp on things, the E9 peak thrust is more than 2N less than the C11 and only about 5N more than a C6. If you are afraid to launch a rocket with a C11, don't launch it on an E9!

Peak Thrust:

C6-x 14.09N
C11-x 21.73N
D12-x 29.73N
E9-x 19.47N

Just in case we forget....

Four C6-3 cluster: 56.36N peak thrust,
Total impulse 35.28N/s

Good points, though we probably need to also remind folks that motor selection can lead to TWO types of terrestrial recovery causes. Peak thrust (and rod length/stiffness) is important to make sure the rocket leaves the rod with enough velocity for the fins to do their job and keep it pointing up. Additionally, total impulse is necessary to get the thing high enough off the ground to reliably deploy a recovery device. That's why the max liftoff weight for a D12-7 would be smaller than for a D12-3 even though they have the same peak thrust. It takes the combination of speed and altitude to make a decent flight (oh yeah--CP/CG stability).

Why is it that when it comes to things that can go wrong on a flight, I feel like I'm such an expert? :rolleyes:

[ghrocketman]

Something is serously wrong when a motor manufacturer produces a C engine that has higher peak thrust than any E engine in their lineup.

The E9 has a woefully dismal load-lifting ability which is exactly the opposite of what is needed in BP offerings.
The only way an E9 can lift a decent amount is to cluster them, but then you add to the overall weight of the rocket.
A cluster of 2 E9's has roughly the same total impulse as a single RMS24 F39 reload, but has roughly 3 times the weight and only HALF the average thrust. The cost for two SU BP E9s is also considerably higher than the single F39 reload as well.

The only less useful E engine ever produced was the FSI "non real E" E6 engine that often tested below 20 n-sec (full D) of total impulse. Those things were a bad joke.

[tbzep]

Why is it that when it comes to things that can go wrong on a flight, I feel like I'm such an expert? :rolleyes:

LOL! :p

We can just say that you've seen it all, instead of experiencing it. :cool:

[tbzep]

The only less useful E engine ever produced was the FSI "non real E" E6 engine that often tested below 20 n-sec (full D) of total impulse. Those things were a bad joke.

I loved seeing those things staged with Estes D12's or FSI D21's (and D18's? not sure on that one). You could easily see the rocket slow down after staging. If the rocket had any size at all, it would slow WAY down!

[PaulK]

Just in case we forget....

Four C6-3 cluster: 56.36N peak thrust,
Total impulse 35.28N/sWhat I find interesting is that when Estes produced the 1B kit, the recommended motors were 4xA8-3, 4xB6-2/4, or 4xC6-5 (though the B6-2 combo wasn't recommended until 73). To further Chan's point, while the peak thrust of the A or B motors would be enough to get it going, the A combo certainly would not get it high enough to safely recover, and the B would be marginal.

All this talk of the 1B makes me want to launch mine again this spring. I also hear there are going to be some real nice launch photos of a Semroc 1B in the March issue of Launch. :o

[tbzep]

What I find interesting is that when Estes produced the 1B kit, the recommended motors were 4xA8-3, 4xB6-2/4, or 4xC6-5 (though the B6-2 combo wasn't recommended until 73). To further Chan's point, while the peak thrust of the A or B motors would be enough to get it going, the A combo certainly would not get it high enough to safely recover, and the B would be marginal.


Since I haven't flown a 1/70 Saturn 1B, I don't know how marginal the D12-3would be, but if it flies pretty well on it, I'd have to disagree on the four B6 cluster. Four B6's have higher peak thrust and total impulse than a D12.

Four B6-2/4's
Total impulse 17.32N/s
Peak thrust of 48.56N.

Single D12-3
Total impulse of 16.84N/s
Peak thrust of 29.73N.

[PaulK]

You are correct. A quick sim shows 4xB6 reaches 196', a D12 reaches 175', and 4xA8 reaches 75'. If only 3 B6 motors light, it reaches 140', with a B6-2 deploying at apogee. A B6-4 would be scary in that situation. 4xC6-3 reaches 395', which is the only configuration I've used.

[tbzep]

You are correct. A quick sim shows 4xB6 reaches 196', a D12 reaches 175', and 4xA8 reaches 75'. If only 3 B6 motors light, it reaches 140', with a B6-2 deploying at apogee. A B6-4 would be scary in that situation. 4xC6-3 reaches 395', which is the only configuration I've used.

You'd definitely need to be diligent in prepping B6-4's to make sure they all ignite. :cool:

[pantherjon]

How much does the 1B weigh?

I have flown my Mercury Invader to very good flights using Estes E9 motors..And this is a 3" diameter rocket that tips the scale at 8.6oz..
http://i156.photobucket.com/albums/t21/Pantherjon/Invader.jpg

[tbzep]

How much does the 1B weigh?

I have flown my Mercury Invader to very good flights using Estes E9 motors..And this is a 3" diameter rocket that tips the scale at 8.6oz..


The Semroc catalog data says 9.9oz, and most of us tend to build heavier than catalog numbers.

[BAR_Daddy]

For the record, I have flown my Estes E version of the V-2 maxibrute on the dreaded E9 SU BP made by estes at least 20 times. The launch rod is 5 feet long.

I have never had an unsafe flight.

I will admit that I would not fly it on that motor in any moderate wind, but I have had nothing but success.

Having said that, I much prefer the AT E and F reloads as well as the AT F21 SU!

I have had similar results with the maxi Honest John that I built (modified to accept 3.75 in long motors)

I also have the Semroc Saturn 1B kit. When I build it, I plan to use the estes D and E motors, as well as the AT reloads.

Again, my two cents.

[ghrocketman]

The owner of Semroc has stated do not fly the 1/70 S1B on an Estes E9...you would think people would take HIS advice if no one else's.

It would be completely FOOLHARDY to fly a kit of complex construction (this ain't no 3FNC BT60 sport job) such as the S1B on a dismally low-thrust E9.

Anyone who does must like using TRASH BAG post-flight recovery of their uniquely RE-KITTED models.

I'll stick to RMS loads of an E18 or HIGHER only.

[jay]

Clustering, in my opinion, is the only way to go with the Semroc SAT1B, but, thats just my opinion. :)

[jay]

The owner of Semroc has stated do not fly the 1/70 S1B on an Estes E9...you would think people would take HIS advice if no one else's.

It would be completely FOOLHARDY to fly a kit of complex construction (this ain't no 3FNC BT60 sport job) such as the S1B on a dismally low-thrust E9.

Anyone who does must like using TRASH BAG post-flight recovery of their uniquely RE-KITTED models.

I'll stick to RMS loads of an E18 or HIGHER only.
Also, I agree with ghrocketman, only I stick with BP motors. :)