PSII launch controller battery

[Dane Ronnow]

I'm building a 2.6-inch rocket that will use three E9-8s in a cluster mount. I've got an Estes PSII launch controller that I use for single-engine rockets, but I know I need more than 9 volts for a cluster. My question is whether to go with an internal 11.1v 3S 2200mAh LiPo, or an external 12v 5Ah (Mighty Max) battery, which would connect via a Deans T connector pigtail (exiting the PSII through the side of the case).

I'm a little leary of the potential for a LiPo to burn down the house, but I don't know if a small wet cell battery will deliver the same burst of current needed to ignite three engines simultaneously. (I don't know that much about current, amps, resistance, etc.)

Cost of both setups—batteries and chargers—is roughly the same.

 

[neil_w]

I'm building a 2.6-inch rocket that will use three E9-8s in a cluster mount. I've got an Estes PSII launch controller that I use for single-engine rockets, but I know I need more than 9 volts for a cluster.

Do you really? I'll bet with dipped igniters you'll have no problem, whereas the off-the-shelf Estes Solar Starters would be a bit iffy even with 12V controller.

(Disclaimer: I haven't tried it, just going by what I think I know)

 

[samb]

Yes, well, welcome to the party. I think the PSII controller will work in either configuration. But I think neil_w brought up a good point about the current pyrogen-less Estes starters. Reliability leaves something to desired and when used in a cluster you multiply your chances for misfires. Lots of posts here about enhancing them by dipping the tip in various mixtures. The other issue is your choice of motors. E9's have a relatively long burn for BP motors which myself and many others dearly loved in the right model. They also have an unfortunate tendency to cato causing much mayhem and damage. I believe they have been removed from the 2020 catalog for that reason. They still are out there in the pipeline but be aware.
Anyway to answer your question I've used 2 amps per igniter as a rule of thumb for so long that I can't recall the source.
All that said, clusters are cool. A little igniter prep and some D12's might serve you better.

 

[Dane Ronnow]

E9's have a relatively long burn for BP motors which myself and many others dearly loved in the right model. They also have an unfortunate tendency to cato causing much mayhem and damage.

Can you clue me in here? Is the cato a launch pad explosion? Mid-flight explosion? Or are you talking about veering off trajectory and hitting somebody? According to OR, this rocket would love the E9. But according to me, the rocket would hate being destroyed.

On three E9-8s, the OR sim spits out an apogee of ~1900 feet, deployment velocity of 12 mph, and 11 Gs. E12-8s have an apogee of ~1850, same deployment velocity, and twice the Gs (21). D12-8s—1197, 8.38, 21G.

Not a huge difference other than acceleration. Anyway, I'll check into pyrogens. I'm a big fan of stacking the odds in my favor. Thanks for the input. I appreciate it.

 

[Spitfire222]

I exclusively use a PSII launcher for all my models using a 3S 1000mAh LiPo. Anecdotally, I haven't had a misfire in over a hundred launches, and the motors ignite the instant I press the go button. I know this isn't directly applicable to your situation, but I'd say you have a good chance of having success using the LiPo, assuming you place the igniters correctly. I would personally try that route to have the convenience of an in-controller battery. For your safety concerns, you can get a LiPo battery bag, and it should be enough piece of mind, especially for only one battery pack. Good luck!

 

[Dane Ronnow]

the convenience of an in-controller battery

That's what I'm thinking too. I'm not terribly worried about LiPos blowing up, but it's a consideration. Thanks for the input.

 

[Scott_650]

Can you clue me in here? Is the cato a launch pad explosion? Mid-flight explosion? Or are you talking about veering off trajectory and hitting somebody? According to OR, this rocket would love the E9. But according to me, the rocket would hate being destroyed.

On three E9-8s, the OR sim spits out an apogee of ~1900 feet, deployment velocity of 12 mph, and 11 Gs. E12-8s have an apogee of ~1850, same deployment velocity, and twice the Gs (21). D12-8s—1197, 8.38, 21G.

Not a huge difference other than acceleration. Anyway, I'll check into pyrogens. I'm a big fan of stacking the odds in my favor. Thanks for the input. I appreciate it.

The Estes E9s don’t “blow up” so much as burn through at a high rate while producing much lower thrust until the ejection charge goes off, adding even more high pressure gas into the body tube. They can also burn through the side of the motor casing. The E12 was introduced as a replacement for the E9.

I didn’t want to commit to the hardware needed for LiPo batteries so I went with rechargeable NiMH replacement batteries - the charger is less fiddly than LiPo charging and maintenance. More power than regular alkaline batteries and reusable - I’ve done plenty of two motor Estes BP clusters but not a trio and they’ve worked fine.

 

[Dane Ronnow]

The Estes E9s don’t “blow up” so much as burn through at a high rate while producing much lower thrust until the ejection charge goes off, adding even more high pressure gas into the body tube. They can also burn through the side of the motor casing. The E12 was introduced as a replacement for the E9.

Got it. Thanks!

 

[Dane Ronnow]

The E12 was introduced as a replacement for the E9.

Another question, which relates directly to why I was leaning toward the E9 rather than the E12 or the D12: Regarding deployment velocity, how fast is too fast? I can get E12-6s and D12-5s locally (Hobby Lobby). But they kick the chute out at ~35 mph. (I can get a slower deployment velocity with E12-8s and D12-7s, but I have to order them online, where they are more expensive than Hobby Lobby.)

Is 35 mph too fast, or no big deal?

 

[neil_w]

According to OR, this rocket would love the E9. But according to me, the rocket would hate being destroyed.

These two statements are incompatible.

 

[Dane Ronnow]

These two statements are incompatible.

Okay, that's funny. And probably true.

 

[Scott_650]

Another question, which relates directly to why I was leaning toward the E9 rather than the E12 or the D12: Regarding deployment velocity, how fast is too fast? I can get E12-6s and D12-5s locally (Hobby Lobby). But they kick the chute out at ~35 mph. (I can get a slower deployment velocity with E12-8s and D12-7s, but I have to order them online, where they are more expensive than Hobby Lobby.)

Is 35 mph too fast, or no big deal?

If you can post your OR file it would be helpful. The lack of flexibility with delays is a definite limiting factor with Estes motors.

As long as the sim with E12s shows the recovery event +/- 2-ish seconds from apogee you should have a safe flight.

Most online retailers prices will be close to HL’s price but the hazmat fee is the sticking point with online buying.

 

[neil_w]

Is 35 mph too fast, or no big deal?

OR kicks out a warning above 50 mph. So 35 mph is within range. I normally target a bit less than that if I can, to allow more margin for error, but it's not a bad number to go with. Is the delay showing too long or too short? Because for both motors, both longer and shorter delays are available, which might get you a bit closer to ideal.

 

[Dane Ronnow]

OR kicks out a warning above 50 mph. So 35 mph is within range. I normally target a bit less than that if I can, to allow more margin for error, but it's not a bad number to go with. Is the delay showing too long or too short? Because for both motors, both longer and shorter delays are available, which might get you a bit closer to ideal.

Too short, by about 1.5 secs. I know I can get another two seconds delay in the E12-8 and D12-7, but I was trying to avoid online ordering. Engines are about $2 more per pack, plus shipping. But that's better than shredding a parachute.

 

[neil_w]

You shouldn't shred. By all means try with what you can get, and if you find it to be too short then you can adjust the next time.

 

[Dane Ronnow]

If you can post your OR file it would be helpful.

 

[samb]

Can you clue me in here? Is the cato a launch pad explosion? Mid-flight explosion? ...

Cato is typically a motor malfunction at or shortly after ignition. Black powder motors are susceptible to tempurature cycling that causes voided in the grains. Rapid deflagration, nozzle spitting, premature ejection charge, no joy. Damage to the model varies from “not much” to “total”. Apparently E9s exhibited this problem enough for Estes to stop production this year. This could be a temporary situation IDK. Hard to tell by just looking at a pack of motors if you have problem. I liked E9 motors but I haven’t used any in a few years. You asked about batteries in this thread and I apologize for taking it in a different direction.

 

[Dane Ronnow]

You asked about batteries in this thread and I apologize for taking it in a different direction.

No problem. It's all good information. I appreciate the input! FWIW, I'm slowly, but surely, walking away from E9s. Maybe someday Estes will reintroduce it, or something comparable—longer burn, lower acceleration.

 

[Ronz Rocketz]

My understanding from Bill Stine's comments in the 2019 Rocketry podcast is that they discovered the E9's made in winter were more likely to Cato so they pulled the line and replace with E12. In the August NAR forum, Bill commented that the E12 and 29mm motors have been low in stock but will be ramping up production with the new tooling.

I've been using two 9v batteries in series which produces 1.4amps. The starters burst into flames. I bought 26650 LiPo batteries but after reading the warnings, I'll stick with the 9v batteries for now.

 

[Scott_650]

I played around with your sim file and even though the flight over E12-6s and D12-5s does show deployment right before apogee I don’t think it’s early enough to cause a problem. A longer delay would be closer to optimal but IMO probably not worth the additional cost for the motors.

If I were building this rocket and wanted to use E12-6s and D12-5s regularly I’d make two changes to give me an improved safety margin - go from three to four fins and add some length to the body tube (preferably about an inch to the upper tube). The increase in drag brings the velocity at deployment down a bit without taking too big a bite out of apogee. If you’re set on three fins adding strakes from the main fins to the top of the lower body tube would work too.

Whether the cost and convenience of picking up motors at HL is worth the slightly lower safety margin or redesign of the rocket is up to you. If it were my rocket - in either your original configuration or modified as above - I’d fly it on the shorter delays. But it’s not mine it’s yours so you’ll have to decide. If you think about it report back after you fly it - I’m curious as to the real world results.

 

[RocketRev]

A deployment just before apogee at 35mph will do less damage than a deployment at 35mph after apogee because the rocket before apogee is decelerating. Deployment after apogee always means that the rocket is accelerating. Deployment and coming in ballistic which is acceleration is always going to do more damage than deployment during deceleration.

Just my 2 cents worth....if that much.....

Brad

 

[Dane Ronnow]

If it were my rocket - in either your original configuration or modified as above - I’d fly it on the shorter delays.

I'm thinking the same thing. I played around with the sim file per your suggestions and did see an improvement—down to ~22mph. But I kind of feel like I'm splitting hairs—a modest gain from changes that will require replacement parts and rebuilding. I'm going to go with what I have, paying close attention to areas that will see higher stress—shock cord mount on the ejection baffle, shroud line attachment points on the parachute, swivels, etc.—and live with it.

Thanks for fiddling with that file, and for your time. I appreciate it.

 

[Dane Ronnow]

A deployment just before apogee at 35mph will do less damage than a deployment at 35mph after apogee

Agreed. (I think they call that 'the lesser of two evils.')

 

[Zeus-cat]

A link to the thread about bad motors. Check your E9 date codes against the ones on the list.

Suspected Bad Motor List | The Rocketry Forum

 

[Dane Ronnow]

Check your E9 date codes against the ones on the list.

I haven't purchased any of these yet. I was planning to, but . . .

 

[Five]

I'm building a 2.6-inch rocket that will use three E9-8s in a cluster mount. I've got an Estes PSII launch controller that I use for single-engine rockets, but I know I need more than 9 volts for a cluster. My question is whether to go with an internal 11.1v 3S 2200mAh LiPo, or an external 12v 5Ah (Mighty Max) battery, which would connect via a Deans T connector pigtail (exiting the PSII through the side of the case).

I'm a little leary of the potential for a LiPo to burn down the house, but I don't know if a small wet cell battery will deliver the same burst of current needed to ignite three engines simultaneously. (I don't know that much about current, amps, resistance, etc.)

Cost of both setups—batteries and chargers—is roughly the same.

Ive launched clusters of three c’s with the regular Estes igniters, no problem. It took a few different configurations though. Also three c’s with Estes sonic igniters.
Let me also add that i have been using the same set of Duracell’s for over a year. 20+ launches

 

[Ronz Rocketz]

I was surprised to see the E9-8 still for sale. They probably determined these are not faulty.

https://estesrockets.com/product/001675-e9-8-engines/

 

[Dane Ronnow]

Let me also add that i have been using the same set of Duracell’s for over a year. 20+ launches

Six C-size Duracells in a PSII launch controller?

 

[Dane Ronnow]

I was surprised to see the E9-8 still for sale.

Right. On Estes' web site. I saw that too. I think I'll drop them a line and see if they're back in production, or they just never removed the E9-8 listing.

 

[Five]

Six C-size Duracells in a PSII launch controller?

I just recently switched them out for energizers, i thought it was about that time. I didn’t want to be hosting a launch for friends and family. You have all eyes on you as you begin the countdown, “5, 4, 3, 2, 1,” and nothing happens.