Nike Smoke (Series 2) Which Engine to use???

[tfrielin]

This past weekend I had a series of great launches with my Estes Nike Smoke--four launches using four Aerotech F50-4T composite engines.

I'm still feeling my way with composites, so this is my question:

I wasn't entirely satisfied with the high acceleration of the Nike Smoke on these engines. It took off so fast, I couldn't really enjoy the liftoff experience.

So--should I switch to other F composite engines to get a lower liftoff acceleration? Will the NS fly ok with less powerful engines?

I'm not all that interested in maximizing altitude performance---where I fly, that's just asking for it to float away. But I'd really like to maximize the smoke and fire of a slower liftoff experience.

Is something like a F23-4 engine powerful enough for a Nike Smoke? Would I hit the sweet spot of slower liftoff without it cartwheeling into the ground after it leaves the launch rod?? Or is there even a sweet spot?

Thanks for any guidance.

 

[NOLA_BAR]

My favorite motor for this rocket is the G40-7W. I much prefer the longer burning white motors over the Blue Thunder for the reasons you mentioned.

 

[tfrielin]

My favorite motor for this rocket is the G40-7W. I much prefer the longer burning white motors over the Blue Thunder for the reasons you mentioned.

Hmm---How about a G40-4W instead? That 7 second second delay sounds like too long for comfort?? I usually detach shock cords when the rocket has time to go vertical incoming...??

 

[NOLA_BAR]

The 7 second delay is perfect for this rocket, the 4 second is too short, the rocket is traveling too fast. A G40 will send it to about 1,600 ft which may be too high for your field.

 

[tfrielin]

The 7 second delay is perfect for this rocket, the 4 second is too short, the rocket is traveling too fast. A G40 will send it to about 1,600 ft which may be too high for your field.

Yeah---the altitude was why I was looking for an F engine to provide a slower liftoff-- A 29mm F engine below the F50 I used??

Is there such a thing?

I can gamble on 1600 or so feet if there's no other good option....It's only my time and money to lose. but, over the decades, I've come to accept that!!!

 

[NOLA_BAR]

Another single use motor is the AT F26-6FJ. It should keep it under 1,000ft.

 

[tfrielin]

Another single use motor is the AT F26-6FJ. It should keep it under 1,000ft.

Yeah, that sounds about right---I'll go for that one next time. Thanks!!

 

[NOLA_BAR]

The F26-6FJ might be a bit slow off the launch rod. Hopefully someone with OpenRocket can chime in and check it.

 

[Scott_650]

Edited

Sounds like a job for a simulation - plugging it into ThrustCurve shows the F26 works ok (it was one of the motors recommended by Estes) shows an apogee of 235 m, delay of 5 seconds so the -6 delay will be fine. Does come of the pad a bit slower than an F50 - 10 m/s as opposed to 13.5 m/s.

I assumed a finished weight of 510 g, the rest using the default settings in TC so if you’re using a longer launch rail/rod your mileage may vary!

 

[samb]

My PS II Nike Smoke did it's first flight on an F26 several years ago. No surprises but not much performance either. I used a 6 foot rod and I didn't note the wind speed that day but I think it was relatively calm, certainly under 10 mph. With a shorter launch guide and higher wind I would be concerned about a cruise missile trajectory. It really does want more power.
+++++1 for Thrustcurve. Great tool for answering the question, "What motor to use???"

thrustcurve.org

This is an older video from the developer of Thrustcurve that uses the Nike Smoke as an example for how to choose motors:

Choosing Motors

 

[neil_w]

Came here to recommend Thrustcurve also. There is no reason to guess and speculate about this sort of thing when there is a way to get a proper answer.

Thrustcurve won't give you the most accurate values for apogee and ideal delay, but it'll give decent estimates, and it *will* give you good numbers for rod speed, since it's only dependent on the rocket's mass. Even if you also model the rocket in OR or Rocksim, Thrustcurve is still the quickest and easiest way to get a quick survey of which motors will work safely in the rocket.

 

[Scott_650]

One minor caveat on using TC - it tends to be on the conservative side concerning rod speed - some results will show a “no go” for a motor that works great and may even be a motor recommended by the designer. Rule of thumb of course is around 30MPH (13.8-ish m/s) but we all know we have rockets that are plenty stable launching at lower speeds - lighter weight rockets with good fin design can usually launch safely at lower speeds, longer launch rod/rail, and low winds are a big help with lower speed launches as well.

 

[neil_w]

One minor caveat on using TC - it tends to be on the conservative side concerning rod speed - some results will show a “no go” for a motor that works great and may even be a motor recommended by the designer. Rule of thumb of course is around 30MPH (13.8-ish m/s) but we all know we have rockets that are plenty stable launching at lower speeds - lighter weight rockets with good fin design can usually launch safely at lower speeds, longer launch rod/rail, and low winds are a big help with lower speed launches as well.

You don't necessarily have to take Thrustcurve's word for which motors are "good", but it will at least give you rod speed estimates for every motor in the world and you can decide for yourself.

Thrustcurve does let you set your preferred minimum rod speed, if you want to set it lower than the default 50 fps.

 

[Scott_650]

You don't necessarily have to take Thrustcurve's word for which motors are "good", but it will at least give you rod speed estimates for every motor in the world and you can decide for yourself.

Thrustcurve does let you set your preferred minimum rod speed, if you want to set it lower than the default 50 fps.

I always look at all the results when I use TC. Sometimes I’ll change the default settings if I think about it - usually I’m using TC either in the field if I want to make a change before launch or while I’m shopping online for motors trying to decide what I need (uh, guess that’s really “want” isn’t it ).