"B"s for a Red Nova?

[TomLee]

Getting ready for a Thanksgiving Day launch session with the visiting grandkids; praying for sunshine and no wind! So, I know D engines are recommended and Cs are acceptable but would a B4 engine get a Red Nova off the launch rod safely? We don't have a super large field and it's surrounded by trees so I don't want this to go too high. I can use a smaller chute to bring it down faster but after all this work in building and finishing I don't want too hard a landing, of course. Are there any other ways of thinking about this? It's just a stock Estes Red Nova, no modifications or anything to affect the weight or profile.

Thanks in advance for your thoughts!

 

[NTP2]

Open rocket will solve all your problems. It’s free to.

 

[mh9162013]

Getting ready for a Thanksgiving Day launch session with the visiting grandkids; praying for sunshine and no wind! So, I know D engines are recommended and Cs are acceptable but would a B4 engine get a Red Nova off the launch rod safely? We don't have a super large field and it's surrounded by trees so I don't want this to go too high. I can use a smaller chute to bring it down faster but after all this work in building and finishing I don't want too hard a landing, of course. Are there any other ways of thinking about this? It's just a stock Estes Red Nova, no modifications or anything to affect the weight or profile.

Thanks in advance for your thoughts!

If you built it REALLY light, it might be possible. If you use a B4 engine, you'll probably need a B4-2 and I'd be surprised if you get 50 feet of altitude and a full parachute deployment before it hits the ground.

To help put it in perspective, I used a B4-4 in a cloned Goblin (which was built heavy, granted) and I got just over 70 feet with it.

Like has already been said, simming is a good idea.

 

[lakeroadster]

I'd recommend against it.

The off the rod speed may not be adequate for a stable flight, and it may not reach adequate height for chute ejection before lawn darting.

Proceed at your own risk.

 

[GlenP]

Another quick and dirty resource is ThrustCurve.com
https://www.thrustcurve.org
If the empty rocket is about 1/4 pound, and you use the 20g rule of thumb in the first say 0.15 sec, then you want to see a thrust curve that gives you about 5 pounds in that initial kick off the pad. B6 and even C6 only reach about half of that. A Super C5 or a C11 would be a safer bet. Any wind at all could shift it sideways into a cruise missile if not going fast enough off the rod.

(I don’t have any personal experience with that particular rocket. Can you use a longer rod? Maybe.)

 

[bjphoenix]

Getting ready for a Thanksgiving Day launch session with the visiting grandkids; praying for sunshine and no wind! So, I know D engines are recommended and Cs are acceptable but would a B4 engine get a Red Nova off the launch rod safely? We don't have a super large field and it's surrounded by trees so I don't want this to go too high. I can use a smaller chute to bring it down faster but after all this work in building and finishing I don't want too hard a landing, of course. Are there any other ways of thinking about this? It's just a stock Estes Red Nova, no modifications or anything to affect the weight or profile.

Thanks in advance for your thoughts!

I think B6 would have a better chance than B4 but it might not get high enough for successful deploy. What that rocket needs is a C5-3 in an adapter or a C11.

 

[Ronz Rocketz]

It's fine. Send it!

 

[PDawg]

It's fine. Send it!

Sounds like something I would say!

 

[mh9162013]

It's fine. Send it!

What's the weight of that rocket?

 

[Tom Flint]

I'd try a B6-2, not a B4. I've successfully launched a 6 ounce rocket with a B6-2.

 

[TomLee]

Thank you, everyone, for your help with this. What a resource! To your points....

• So far I think "it's not such a good idea" seems to outweigh "it'll be fine" by a bit. I tend towards caution myself, but thanks for the encouragement, Ronz Rockets, and the video confirming that a B6-4 actually launches successfully. Man, that thing came back down fast! And I notice you used a standard 1/8" launch rod to boot.
• I've never used a simulator but I can see its value here. That jpg from lakeroadster is amazing. The numbers are pretty telling. Which simulator is that from? I appreciate the motor data link, GlenP.
• mh9162013--My Red Nova is at 80.86 g/2.85 oz with paint, chute, and Kevlar shock cord (I guess that's not really a stock Estes item). Still have to add decals and clear coat but that'll be minimal additional mass. I just now put some recovery wadding and a C6-5 engine (the only C I presently have) and it weighed 108.78 g/3.84 oz. This is easily within Tom Flint's B6-2 range

Once again, thank you.

 

[Ronz Rocketz]

What's the weight of that rocket?

Don't know. I ended up selling it to someone but have a new one waiting in the wings. I guess it's time.

 

[mh9162013]

mh9162013--My Red Nova is at 80.86 g/2.85 oz with paint, chute, and Kevlar shock cord (I guess that's not really a stock Estes item). Still have to add decals and clear coat but that'll be minimal additional mass. I just now put some recovery wadding and a C6-5 engine (the only C I presently have) and it weighed 108.78 g/3.84 oz. This is easily within Tom Flint's B6-2 range

If it's under 85 grams, it'll probably be fine with a B6-2 or even B4-4 engine. However, it won't be after you paint it and add the decals...together, they can add more weight than you might expect. Depending on how you paint it, expect your rocket to weigh more than 100 grams when you're done. In that case, I'm not sure if using a B engine will suffice.

 

[lakeroadster]

... I've never used a simulator but I can see its value here. That jpg from lakeroadster is amazing. The numbers are pretty telling. Which simulator is that from? I appreciate the motor data link, GlenP.

It's Open Rocket, and it's freeware... get ya some here: https://openrocket.info/​

 

[TomLee]

It's Open Rocket, and it's freeware... get ya some here: https://openrocket.info/​

Got it. Thanks!

 

[NTP2]

Got it. Thanks!

If you got questions just ask also @neil_w has some tutorials on here.

 

[smstachwick]

Other C options include the Q-Jet C12s and C18s. I’ve flown a couple of C18s and they scoot!

 

[Back_at_it]

If you built it light you could get away with the B4-2. You'll also wan tot ensure that you fly it straight up and don't tilt the rod.

 

[bjphoenix]

Got it. Thanks!

For a popular rocket model you can search the internet and find simulation files already made. Open rocket can read files for another simulation program called rocksim so you can search for those too.
If you use someone else's sim file you should check to see that it matches the weight of your finished rocket. Some people will override the weights of different components, maybe even make other changes, but it can give you a good starting point.

 

[TomLee]

Thank you everyone for all this info. I've picked up some neat things not even related to my specific Red Nova question, e.g. the simulation programs. And being such an Estes user I'd never even looked at those Q-Jet motors. Maybe that C12-4 would work for me.