staging question for newby

i've built a handful of model rockets now and am getting more and more proficient in my builds... as i go i am becoming a bit more adventuresome and would like to take something new on... i really like rockets that go high... i am finding some guys are into rockets that are big.. some are into rockets that are beautiful... i like rockets that go high...

being a new rocketeer i am relying on lessons learned in high school physics 15 years ago to guide me in this endeavor. if you want something to go fast and far... you need it to be as light as possible and have as much energy as possible. with that as my guiding principle i'd like to see about trying to pack the most punch into as small of a rocket as possible.

any ideas on staging E's with BT-50 tubes? is that even possible? or maybe an E booster with a C second stage with a BT-50 tube?

or maybe retrofitting thin tubs on top of larger tubes that hold the engines?

with rockets my assumption is not only do you need to go far and fast... you need to go straight up... so i need fins that help stability without getting in the way of height.


i don't have a PC so getting a rock sim type software won't work for me... just got a MAC.

thanks

808rocketman said:

i don't have a PC so getting a rock sim type software won't work for me... just got a MAC.

thanks

Click to expand...

Both RockSim and OpenRocket work with Mac.

Openrocket is your friend. You can do stages and fine tune the design before you cut up tubing. Best of all it's free! And easy to use.

A minimun dia 24mm (bt-50) to another will go high. Problem might be getting it back. Will take some different coupling but it could be done.

I have several stagers but none minimum dia just yet. All Red Max kit bashes, and they all have had successful launches. A standard Red Max punched out to handle D's and then add a two stage booster, yep it goes high.

Now you got me wanting to try a minimum dia two stage.

Oh and Welcome to The Rocketry Forums. Lots of great folks here. Enjoy!

See ya,
Rod

Openrocket will work on macs. Just get the right version at the website. I use it on a mac mini just fine. Just make sure you have the mac up to date.


https://openrocket.sourceforge.net/

Yes, a BT-50 is the size tube for 24mm D and E motors. A minimum diameter stager built with such an airframe would go very high.

My first stager was a kit so that's what I'll recommend. There are many to choose from but here's one using 24mm motors. https://www.estesrockets.com/rockets/by-engine/e/007225-extreme-12tm

This document contains the basic write-up on black powder motor staging concepts that will give you the basic vocabulary. https://www2.estesrockets.com/pdf/2845_Classic_Collection_TR-TN.pdf

One thing I've learned is that two (or more) sets of eyes are almost always required for successful recovery of booster(s) and sustainer. Hope this helps.

thank you... i'm going to give Openrocket a try when i get home from work today.

so if i line up BT-50's for the body and booster... does the coupling go on the outside? and do they make couplings that fit on the outside or just inside? if only inside, how do i fit two D's in there?

thank you!

RodRocket said:

Openrocket is your friend. You can do stages and fine tune the design before you cut up tubing. Best of all it's free! And easy to use.

A minimun dia 24mm (bt-50) to another will go high. Problem might be getting it back. Will take some different coupling but it could be done.

I have several stagers but none minimum dia just yet. All Red Max kit bashes, and they all have had successful launches. A standard Red Max punched out to handle D's and then add a two stage booster, yep it goes high.

Now you got me wanting to try a minimum dia two stage.

Oh and Welcome to The Rocketry Forums. Lots of great folks here. Enjoy!

See ya,
Rod

Click to expand...

+1 on Open Rocket working on MACs. Mine works well. And OR is free, versus $125 for Rocksim.

Here is how (at least my way, there are others) to make a 24mm to 24mm (C-11, Ds, or Es) 2 stage rocket. In this method, the motor case is also the coupler.
In the upper stage, glue the motor block so the motor sticks out 1/2". I recommend sizing this for an E, and then when using Ds or C-11s, use a spacer that makes up the difference. Cutting a spent 24mm motor to proper length makes a good spacer.
For the booster (bottom stage), cut the body tube so it is the length of the motor you want to use (C11 and D, or E length) plus 1/2", plus the length of a motor block.
Glue the motor block into the BOTTOM of the body tube. Then add fins and everything else to both stages.

When prepping for flight, take your two motors and tape them together end to end using clear office tape (make sure they are both orientated correctly). Slide the combo into the top stage. Make sure the fit is very tight, so it won't kick out during the ejection phase. Then slide booster over the bottom motor and ensure it is snug, but doesn't have to be as tight as the top motor. Ensure the area where the booster tube slides over the top motor isn't very tight, so they will separate when the top motor ignites. The plastic tape will melt at this time.

Another "cheap" way to stage is to tape two motors together and slide it into a single stage rocket, with no "booster" stage. I do caution you on this. If you don't have software to figure out the CP, and thus the stability, you are endanger of lowering the CG too much and making the rocket unstable. Also, some people consider kicking a loose spent motor out during flight a violation of the safety code. But I consider the "tumble" recovery of a spent paper motor case to be safe.

Third way: Buy a 2 stage kit and do this for your first 2-stage to learn how they do it, then scratch build your own cloud-killer.

2-stage, minimum diameter rockets can go very high, so be mindful when picking a field and choosing the weather to fly in. You may loose sight of the upper stage or even the booster. A 2nd pair of eyes to spot the booster is helpful.

And don't forget getting the right motors. Get the zero delay "-0" motors for the booster and usually the 7 second delay "-7" motors for the sustainer (upper stage).

any recommendations on altimeters and how to fit that on a rocket?

I just whipped up this example to show it can be done. The file still needs fins, recovery, nose cone shoulder and such but the engine and staging should work. This is going to be a hot rod of a rocket. Just keep track of stability and make sure you adjust weight of the parts as you go.

The sustainer motor case becomes the coupler, this would actually be a pretty easy build, hardest part would be keeping the fins aligned during assembly.

Once you play with Openrocket, you will try all sorts of designs to see if it will work.

***updated file below

Jolly Logic has a unit that will fit in a BT-50

Oh and the other hardest part about this rocket would be getting it back!

Have fun!

Rod

808rocketman said:

any recommendations on altimeters and how to fit that on a rocket?

Click to expand...

Perfectflite has a couple that will fit. I have a "P-Nut" that fits into BT20 tube (size of an A,B,C motor). Make a payload bay in your rocket. Get a coupler for BT-50. Make sure it has no holes in it, this way the ejection gasses don't get into your payload bay. These gasses are bad for electronics. I prefer a solid balsa coupler for this application. Then cut a length of tube that is equal to, or slightly longer than the nose cone shoulder plus the altimeter length, plus the coupler shoulder. Glue the top half of the coupler to the payload bay tube. Connect the bottom of the coupler to the recovery system just as you would connect the NC if you didn't have a payload bay. Make sure the NC fits tight. Use some tape on the inside or outside of the joint to ensure it stays in place during flight. Make sure the bottom of the coupler fits snug with the body tube, but loose enough it will eject (just like you would with a regular NC). But keep in mind, that with the extra weight (my altimeter is .25 oz) there is slightly more chance of drag seperation before ejection.

I forgot to mention, drill a 1/8" hole into the payload bay tube so it will sense air pressure.

You could get one of the many kits out there that are multi-stage to learn the basics of LPR staging, and how the pieces fit together. Many of those have very good performance, and will provide many valuable lessons that can then be used in your scratch-built endeavors. See if you can find an Estes Commanche 3...3 stage that fully loaded will take a D12-0 to a C6-0 to a C6-7...Good luck getting much of anything beyond the first booster back...lolMany great multi-stage kits to choose from and learn from before building your own.

I went and finished that example file above. This will be a performer. Best to have LOTS of eyes on this one. Such a simple build that I may have one ready for our spring time launch at Argonia. Bright paint colors are a must. Oh and lots of eyes tracking both booster and sustainer.

View attachment two stage min dia example.ork

I've built and flown a few two stages and constructed them much as CZ described.
The first (and most impressive) was designed on OR to peak at around 2200'. I painted it in fluorescent green hoping it would be easy to find. It had an Estes D12-0 as the lower stage and a D12-7 for the upper.

It flew perfectly, straight as a die. The delay trail disappearing between two clouds was memorable. There were lessons learned however.

1. It was the last I saw of the sustainer stage - much in line with what others I have said.

2. Unless you're prepared to lose a £30-£60 altimeter, don't install one.

3. OR is excellent.

4. I was concerned about a spent D motor falling without recovery as well. In practice it "fluttered" back to the ground along with the fin tube, without a problem. Tumble recovery works. We did recover that bit.

5. Fluorescent paint is useless unless you have an indication of where it went (even with six pairs of eyes tracking it).

As a footnote I was planning to fly an 18mm minimum diameter two stager with Klima D9's. The OR design predicts a little over 3000'. Needless to say I've shelved the flight for now. At least until I can find a flat, open horizon desert in the UK.

SO

A guy at my club flew a Comanche3 on 3 E-9s. He wrapped it in Aluminum foil to help see it. It simmed out to 4,700 ft. It weather cocked a lot and didn't go nearly that high. We found the 3rd and 2nd stages, but he lost the Sustainer. Building it and getting it to go high are the easier parts. Finding it after launch is the hard part.

Now he is making a 29mm Comanche to use the Estes black powder Fs. He calls it his F'n Comanche. Hope to see it fly this spring/summer.

CZ Brat said:

I forgot to mention, drill a 1/8" hole into the payload bay tube so it will sense air pressure.

Click to expand...

IS there enough change in air pressure to measure height in a low power rocket? I always assumed that it was GPS positioning that was being read, or am I wrong?

Kirk G said:

IS there enough change in air pressure to measure height in a low power rocket? I always assumed that it was GPS positioning that was being read, or am I wrong?

Click to expand...

Yes. (depending on the sensitivity of the sensor)
Many (most ?) altimeters measure height with barometric pressure sensors.

https://www.jollylogic.com/products/altimeterone/
https://www.missileworks.com/rrc2


GPS may be present on higher dollar units, mostly used to aid tracking and recovery.

I never really understand the point of putting big engines in a multistage bird unless you are taking a video and want a long flight .
I understand staging for NASA almost finless or finless rockets as a means of getting a payload to high altitude or out into orbit or space. But with model rockets with fins, it seems like gram for propellant gram, you get more payload or altitude per total grams of propellant by going up an engine size or three than by staging. Especially for the sustainer I tend to put the smallest engine I can in it (with appropriately shorter delay) so I can say, "yes it successfully staged" and still say (hopefully) " and I recovered all the stages." Since the upper stage (or stages) is (are) already up to speed when they ignite, seems like they don't need much to continue the flight. For 18mm engines I also like the wider nozzle of the A8 compared to the B6 and C6 as I figure particularly for gap staging it increases probability of successful upper stage ignition.

the Jolly Logic altimeter one is sensitive enough to measure a distance change of approximately one foot of elevation. the thought has occurred to me that, should I need to rebuild the booster for my Estes Avenger, a 24mm engine mount would work nicely.
Rex

BABAR said:

I never really understand the point of putting big engines in a multistage bird unless you are taking a video and want a long flight .
I understand staging for NASA almost finless or finless rockets as a means of getting a payload to high altitude or out into orbit or space. But with model rockets with fins, it seems like gram for propellant gram, you get more payload or altitude per total grams of propellant by going up an engine size or three than by staging. Especially for the sustainer I tend to put the smallest engine I can in it (with appropriately shorter delay) so I can say, "yes it successfully staged" and still say (hopefully) " and I recovered all the stages." Since the upper stage (or stages) is (are) already up to speed when they ignite, seems like they don't need much to continue the flight. For 18mm engines I also like the wider nozzle of the A8 compared to the B6 and C6 as I figure particularly for gap staging it increases probability of successful upper stage ignition.

Click to expand...

Quite true (about larger single stage motors being more efficient that multistaging smaller motors) but, as someone's quote from Feynman about physics and sex, "Sure, both produce practical results, but that's not why we do it" (or words to that effect), the same holds true for staging rockets...

We do staging because it's fun and different, not for "maximum capability"...

Later! OL JR

BABAR said:

I never really understand the point of putting big engines in a multistage bird unless you are taking a video and want a long flight .
I understand staging for NASA almost finless or finless rockets as a means of getting a payload to high altitude or out into orbit or space. But with model rockets with fins, it seems like gram for propellant gram, you get more payload or altitude per total grams of propellant by going up an engine size or three than by staging. Especially for the sustainer I tend to put the smallest engine I can in it (with appropriately shorter delay) so I can say, "yes it successfully staged" and still say (hopefully) " and I recovered all the stages." Since the upper stage (or stages) is (are) already up to speed when they ignite, seems like they don't need much to continue the flight. For 18mm engines I also like the wider nozzle of the A8 compared to the B6 and C6 as I figure particularly for gap staging it increases probability of successful upper stage ignition.

Click to expand...

There is an issue when going to a larger motor means increasing the motor diameter. I just did a quick OR sim of a 2 stage minimum diameter 18mm rocket. With two C6s it projected an apogee of 1292. Two C6s combined have 21.6 grams of propellant. Did another quick sim of a 24mm minimum diameter rocket with a D12, and it simmed out to 1000ft. It has a propellant mass of 21.1 grams. I then did a 2 stage 24mm with two C11 (22 grams total), and got just over 1000ft as well.

CZ Brat said:

There is an issue when going to a larger motor means increasing the motor diameter. I just did a quick OR sim of a 2 stage minimum diameter 18mm rocket. With two C6s it projected an apogee of 1292. Two C6s combined have 21.6 grams of propellant. Did another quick sim of a 24mm minimum diameter rocket with a D12, and it simmed out to 1000ft. It has a propellant mass of 21.1 grams. I then did a 2 stage 24mm with two C11 (22 grams total), and got just over 1000ft as well.

Click to expand...

I stand corrected

I spotted these https://www.ebay.com/sch/i.html?_fr...tes+cc+express&_nkw=estes+cc+express&_sacat=0 on Ebay today and thought you my try one first to get your feet wet. I modified mine by making the sustainer stage with a longer motor mount to accommodate 24 mm E9-8 motors, and built the booster as per instructions. It flies perfectly without additional nose weight and probably in excess of 2,000 feet, which is farther than I can see. :eyepop:

There's something about watching a staged rocket fly. You are constantly thinking out loud during the boost off the pad 'Come on light, come on light, come on light...

Then the pop and whoosh when the stage burns out and starts the next engine. Then you start thinking out loud, man that's going really high, better start chasing it now.

But there is always that chance that it won't stage. Had one happen to me, but when they work, it's a show!

I build them to fly, light as I can and smallest recovery I can get a way with. Small chutes or streamers. I also have the launch pasture at Argonia, Ks to aid with recovery. At least until the crops start growing. Amazing how even a 6 inch dia rocket can disappear in a new wheat field.