Staging Methods for LPR Rockets...

Pem Tech

King Kraken Away!
Joined
Jan 19, 2009
Messages
4,695
Reaction score
309
Location
Llama Central
As has been stated, not much has changed in BP staging.
Guess I've been lucky with staging, except for the embarrassing Cherokee III incident way back in the 90's.
That was the only staged rocket I had built until the early 2000's. For no particular reason I built the Sea Skimmer and the heinous F-1 Medusa's Cousin. The Sea Skimmer was a spur of the moment military style scratch built D to D gap stager. The booster motor tube extends almost to the 2nd stage motor. No ports, no hooks, no engine blocks, no tape and both motors are friction fit. She has flown without fail for almost 15 years. See images below.
SeaSkimmerDSC_8549.jpeg
SeaSkimmerDSC_8565.jpeg
SeaskimmerDSC_8566.jpeg
SeaSkimmerDSC_8568.jpeg
SeaSkimmerDSC_8569.jpeg
As has been mentioned in previous posts, be mindful of the fit of the stage coupler. It needs to be tight enough to hold the booster in place but loose enough to pop free during staging. Soaking the coupler in CA then sanding to the proper fit is a great idea.

If I remember correctly the F-1 Medusa's Cousin was ill-conceived on a stormy night under the influence of too much cheap vodka, or something like that. It is a hideous kit bash/scratch build using parts of an Estes Double D and whatever was laying around the bench. The horrid thing is gaped staged from 2 D's to a single D over about 5 inches. No special construction, just opened up the transition to allow the exhaust gasses to pass through. Made sure the booster fit was correct and she flew well before being buried in an shallow unmarked grave. Again, no ports, no hooks, no engine blocks, no tape and all motors are friction fit. But with lots of ugly...
1DSC_8471.jpeg
1DSC_8474.jpeg
1DSC_8475.jpeg
1DSC_8477.jpeg

I guess the point is that staging isn't difficult and can be accomplished with a minimum of technology, effort and experience.
 

Pem Tech

King Kraken Away!
Joined
Jan 19, 2009
Messages
4,695
Reaction score
309
Location
Llama Central
View attachment 500928 View attachment 500929 View attachment 500930 View attachment 500931 View attachment 500933
The Split Infinity is a canted motor two stage using gap staging, you can see the two ventholes on the sustainer.
You can also see the matching vent holes on the booster's coupler, the two must align.
The slot in the coupler is there to prevent the booster from twisting and to ensure it goes onto the sustainer in the proper orientation.
There are corresponding tabs within the sustainer's motor-shrouds which can be seen, barely, in the final pic.

All of this is to demonstrate that two stage rockets can be as complicated or simple as you desire.

I launched this rocket many a times and never had a flight where only one of the sustainer motors ignited.

Wow!
Now that is an original idea!
 

Cape Byron

The BAR formerly known as Skippy-2
TRF Supporter
Joined
Aug 3, 2019
Messages
4,987
Reaction score
9,167
Location
Northern Rivers, Australia
If I remember correctly the F-1 Medusa's Cousin was ill-conceived on a stormy night under the influence of too much cheap vodka, or something like that.

I've conceived a number of things under the influence of too much alcohol. They ended up going to university and graduating, so that's nice.
 

Sooner Boomer

Well-Known Member
Joined
Mar 21, 2011
Messages
4,682
Reaction score
2,682
As well as the electronics I'm wondering what kind of small battery to use that has enough juice to fire an igniter.

There are lots of small form-factor batteries. You can take apart a 9v battery - some are made of of a bunch of "AAAA" batteries. There are small "watch" batteries, even higher voltage ones in lithium, that can be stacked. Speaking of lithium batteries, the common 18650 battery is supposed to be 18mm in dia, and 65.0mm long. My next "serious" project, my first attempt to use altimiter ejection will be based off of an Eggtime Quark (or a pair of them for redundancy), powered by 2S lipo batteries that are 16.5mm x 12mm x 45mm https://www.amazon.com/dp/B07R7856RX?psc=1&ref=ppx_yo2_dt_b_product_details
 

BABAR

Builds Rockets for NASA
TRF Supporter
Joined
Aug 27, 2011
Messages
9,931
Reaction score
4,594
I always get a kick out of people wanting do black powder staging to composites, mainly because I never see the point in putting anything larger than they have to in the sustainer or if 3 stage the mid stage.

Of course, I am thinking that I want to recover the whole stack. You ALWAYS need enough force in the lowest booster stage to get the stack off the rod or rail at adequate velocity, D12 tends to be my go to for anything other than minimum diameter. But once I get the stack moving, the sustainer or mid stage(s) really have very little work to do, the bird is already up to speed, and if I really wanted altitude I’d go single stage with a bigger motor. Going smaller sustainer and if 3+ stages mid staging, I get all the entertainment of seeing the rocket stage, and much shorter walk and less chance of off vertical staging. Plus the smaller motors don’t mess the CG as much , and makes it easier for the first stage to get the stack moving.

Regarding using zero delay motors to deploy chutes and streamers, absolutely it works. Just understand that with zero delay you have no time for rocket to slow down, so especially with chutes you have a chance of shredding the chute or shroud lines, since the rocket will likely be at max velocity when it deploys. I learned this from experience. Streamers are a bit more forgiving.
 

GlenP

Well-Known Member
TRF Supporter
Joined
Oct 3, 2014
Messages
2,776
Reaction score
1,206
…Regarding using zero delay motors to deploy chutes and streamers, absolutely it works. Just understand that with zero delay you have no time for rocket to slow down, so especially with chutes you have a chance of shredding the chute or shroud lines, since the rocket will likely be at max velocity when it deploys. I learned this from experience. Streamers are a bit more forgiving.
Do you think possibly a JL Chute Release might work in that situation?
 

BABAR

Builds Rockets for NASA
TRF Supporter
Joined
Aug 27, 2011
Messages
9,931
Reaction score
4,594
Do you think possibly a JL Chute Release might work in that situation?
Took me a moment to think your thought process through.

with a couple caveats, it might help, as you are essentially using “nose blow” recovery (an actual I believe at one time standard recovery technique for small lightweight rockets that were just a little too big for featherweight. Currently I believe it is practiced quite frequently however totally unintentionally, when the chute is packed too tight and doesn’t make it out of the tube!). I believe it would help slow things down before deployment, which would be a plus.

caveats as follows

1. Even with nose blow, you are ejecting your nose cone at or near max velocity. On the good side, zero delay ejections seem to have less “force” than standard motors, but the rocket at velocity is still gonna yank a good bit on the cord because of this, and I am not sure if the extra mass of the JLCR is gonna help or hurt you. Definitely better than a full chute rapidly deploying at full velocity.

2. I don’t have a JLCR, but my understanding is that you set a deployment altitude above your launch pad altitude, technically “Above Ground Level” or “AGL.” For that to work, I presume you have to get the rocket ABOVE your set altitude to begin with. To do this with a zero delay motor you have to accomplish TWO things. First You need enough thrust, enough duration, and a relatively light and sleek rocket to get to that altitude before staging. That can be a challenge with available zero delay BP motors, which I believe max out at F15-0. Second, you gotta hope you don’t get too much weathercocking, as your rocket might travel 300 or 400 feet before staging, but if it is off vertical it may not be over 200 feet AGL.

as in all endeavors, often people mix up what they CAN do with what they WANT to do. I enjoy staging, for me half of the enjoyment is SEEING the staging (so I am good with anything from about 30 feet to maybe 150 feet, at 200 feet my eyes are good but it isn’t as exciting——unless the rocket is weathercocking and then the later the staging the closer to TOO exciting.:oops:). The SECOND part I like about staging is getting all my parts back. Hence I am not an altitude fiend for either the booster OR the sustainer.

but too each his or her own. I bow to those who have launch and recovered all parts of a three stage FarSide with max motors in each section. I have neither the desire, patience, (nor the recovery field) To do it myself.

for long gap boosters, my favorite recovery technique is to cluster it with a short delay (A8-3usually) cluster pod with it’s own chute. this has worked well.
 
Last edited:

lakeroadster

👀 Oddroc Scum 👀 CAD Monkey LPR/MPR
TRF Supporter
Joined
Mar 3, 2018
Messages
5,519
Reaction score
5,294
Location
Central Colorado

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
The old-school method had the flyer tape the motors together using one layer of cellophane tape and friction fitting the motors in the motor mount tubes.
Still what I do. :). Works fine, especially when adding a booster stage to a single stage rocket using CHAD staging. The rocket has to be very stable if you are going to do CHAD staging.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
When I launch a two-stager, I like to use a high initial thrust, but low total impulse engine, like an A8-0, as the booster engine. The second stage is a higher total impulse engine, such as a B6-6.

If I do it that way, the rocket isn’t so high up when the second stage ignites. I can actually see the rocket sort of “pause” and then it punches a hole in the sky when the second stage kicks in. Fun!
 

neil_w

OpenRocketeer
TRF Supporter
Joined
Jul 14, 2015
Messages
14,234
Reaction score
7,624
Location
Northern NJ
When I launch a two-stager, I like to use a high initial thrust, but low total impulse engine, like an A8-0, as the booster engine. The second stage is a higher total impulse engine, such as a B6-6.

If I do it that way, the rocket isn’t so high up when the second stage ignites. I can actually see the rocket sort of “pause” and then it punches a hole in the sky when the second stage kicks in. Fun!
A8 in red, B6 in green (courtesy of thrustcurve.org):
1656189708655.png
As you can see, the B6 has a higher initial thrust spike to get the rocket moving, so it's a better booster motor. The A8 is really misnamed (there are historical reasons for this which I don't recall ATM); it really is more like an A3.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
A8 in red, B6 in green (courtesy of thrustcurve.org):
View attachment 524338

As you can see, the B6 has a higher initial thrust spike to get the rocket moving, so it's a better booster motor. The A8 is really misnamed (there are historical reasons for this which I don't recall ATM); it really is more like an A3.
To paraphrase George Costanza: You are ruining this for me, Neil! ;-)

The A8-0 still has a lower total impulse compared to the B6-0. So using it on the first stage achieves my goal of being able to actually see the rocket’s second stage kick in.
 

smstachwick

LPR/MPR sport flier with an eye to HPR and scale
TRF Supporter
Joined
Jul 29, 2021
Messages
1,767
Reaction score
1,494
Location
Poway, CA
The A8 is really misnamed (there are historical reasons for this which I don't recall ATM); it really is more like an A3.

The motor dates back to when thrust was measured in imperial units. It was originally an A.8 (0.8 pounds average thrust) and that was retained with slight modification when Estes motors went to Newton measurements.

All of the old catalogs on the Estes website and on Ninfinger display this.

The motor remains much the same today, generating an average of 3N (0.8 pounds) of thrust for well under one second to deliver about 2.5 Newton-seconds of total impulse.

An A8-0 is still a valid booster motor in very light rockets that are intended to stage low. I have flown a few.

The A10-0T actually delivers more maximum thrust at liftoff than the A8-0 (about 12 Newtons) but an average of two Newtons of thrust because of its anemic sustaining thrust. It’s called an A10 to advertise its improved maximum thrust over the A3T. It would a better choice for getting a heavier two-stager going than the A8-0.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
The A10-0T actually delivers more maximum thrust at liftoff than the A8-0 (about 12 Newtons) but an average of two Newtons of thrust because of its anemic sustaining thrust. It’s called an A10 to advertise its improved maximum thrust over the A3T. It would a better choice for getting a heavier two-stager going than the A8-0.
Now there’s an idea! How about an A10-0T (13mm), um, inserted into the rear of an engine in a single stage rocket (18mm) to do some CHAD staging? I am not sure how I would get it to stay in place and then come off cleanly when the second stage ignites. Maybe just creative use of Scotch tape…?
 

smstachwick

LPR/MPR sport flier with an eye to HPR and scale
TRF Supporter
Joined
Jul 29, 2021
Messages
1,767
Reaction score
1,494
Location
Poway, CA
Now there’s an idea! How about an A10-0T (13mm), um, inserted into the rear of an engine in a single stage rocket (18mm) to do some CHAD staging? I am not sure how I would get it to stay in place and then come off cleanly when the second stage ignites. Maybe just creative use of Scotch tape…?
Scotch tape should work fine. The gas is more than hot enough to melt it or weaken it instantly, staging should be a snap. Build an airframe around the kind of joint and you’re in business.

If it turns out I’m wrong and it does a death dive, it won’t go very high and the damage should be repairable.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
If it turns out I’m wrong and it does a death dive, it won’t go very high and the damage should be repairable.
I only conduct CHAD staging and other “heads up” experiments on “beater” rockets. Don’t get me wrong, I love my beater rockets. They look like heck but they keep on flying. Still, if a beater rocket has a hard landing that ends up in the rocket being “totaled”, well, “its time was up”, you know?
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
A10T vs. A8:
View attachment 524378

Interestingly, the curve for the A10T do not show the listed 12N max thrust.
This is why, although you prepare as much as you can, and run the numbers, at the end of the day sometimes you just press the two launch buttons simultaneously and see what happens. (Yes, my homemade launch controller has two launch buttons that have to both be pressed at the same time to launch the rocket. My idea of a safety feature. Stolen from the Estes “Electron Beam” controller circuit.)
 

smstachwick

LPR/MPR sport flier with an eye to HPR and scale
TRF Supporter
Joined
Jul 29, 2021
Messages
1,767
Reaction score
1,494
Location
Poway, CA
I only conduct CHAD staging and other “heads up” experiments on “beater” rockets. Don’t get me wrong, I love my beater rockets. They look like heck but they keep on flying. Still, if a beater rocket has a hard landing that ends up in the rocket being “totaled”, well, “its time was up”, you know?
I had a Generic E2X that became a beater after a water landing. It did a death dive when the A8-0 booster failed to light the B6-6 sustainer and I retired it from flight duty. It was an act of mercy. I’ll have to find the flight video.

It got replaced by a converted Hi-Flier that continued my work with 18mm two-stagers. That story is another altogether.

But my general rule with beaters is that if I can just put it back together, why not? If I have to take it apart to fix it, then I may as well just get a new kit with fresh, quality, un-worn parts. I’ve made some exceptions but that’s how it normally goes.
 

brockrwood

Well-Known Member
TRF Supporter
Joined
Jun 9, 2015
Messages
1,734
Reaction score
1,259
Location
Denver, Colorado, USA
I had a Generic E2X that became a beater after a water landing. It did a death dive when the A8-0 booster failed to light the B6-6 sustainer and I retired it from flight duty. It was an act of mercy. I’ll have to find the flight video.

It got replaced by a converted Hi-Flier that continued my work with 18mm two-stagers. That story is another altogether.

But my general rule with beaters is that if I can just put it back together, why not? If I have to take it apart to fix it, then I may as well just get a new kit with fresh, quality, un-worn parts. I’ve made some exceptions but that’s how it normally goes.
I save the still salvageable parts from the dead beaters until I have enough parts to make an aberrant, mutant, monstrosity rocket.

C91863C3-3BBD-426D-ACAB-ECE5DA304523.jpeg
 

smstachwick

LPR/MPR sport flier with an eye to HPR and scale
TRF Supporter
Joined
Jul 29, 2021
Messages
1,767
Reaction score
1,494
Location
Poway, CA
For the next flight I decided to up the ante a bit and upgrade the sustainer to a B6-6, angling the rod a bit closer to vertical for a straighter flight. This one was less than successful. The stages separated but the sustainer failed to light. At first it fell sideways, its fins rolling it, but in the last portion of its descent it straightened and impacted the surface with a good thud. It was at that instant I was glad I had decided to keep the booster motor pretty small for the first few launches. If it had come in from the altitude that a C6-0 would have put it at, that could have been trouble.

I enter frame at T+ 0:22 to recover the rocket.

View attachment 516552


View attachment 516553 This is the third time I have had this error. The first was with my Super Gnome, where my application of tape was nowhere near strong enough to hold the motors together long enough to stage. I improved my technique and got it to work reliably enough at November ROCstock and subsequent launch events. The second was with my Super Star Trooper with DART. I did not determine the cause of this failure at the time but my best guess was that the remnants of the booster propellant grains simply missed the nozzle. That rocket was also small enough to tumble back without damage. This larger, heavier one wasn’t so lucky.

I solicited some troubleshooting input from the other fliers at the range. Jim Myres from Discount Rocketry examined my rocket and he mentioned the gap staging techniques with which I was already familiar, pointing out that the pressure probably popped the booster off before the sustainer could ignite. I was puzzled as to how this was possible, since I’d taped the motors together with what I thought was decent technique, but since packing up for the day I think inclined to agree with him.

Since getting involved in rocketry again, I’ve noticed that the cellophane tape that I packed in my range box is pretty weak in terms of adhesive strength. It’s not exactly the kind of weak that you’d find on a Post-it note but it’s substantially easier to remove from surfaces than the translucent Scotch tape with which I’m sure we’re all familiar. My guess is that he is indeed correct, the motors were not held in place firmly enough.

I also now believe that this was the reason for my Super Star Trooper’s staging failure.

After that conversation I returned to my table and removed the unused B6-6 motor. The friction fit was a bit too tight, so I ended up pulling out the entire mount and cutting the motor mount tube to get the motor free. Given the previous water recovery and today’s nose-first crash, I think this rocket has earned retirement.

I ended up buying a pair of standard Hi-Fliers from Jim’s trailer to continue flying 18mm two-stage at the next DART launch and possibly LDRS. Hopefully a new roll of tape will resolve my staging woes and this won’t happen again for a while.
Here’s my staging failure.

This is one of the most disappointing things that can happen at the range because you instantly know three things:
  1. What happened
  2. What’s going to happen
  3. That there’s nothing you can do about it.
From rocketreviews.com. Whose data should I trust?

View attachment 524388
Interesting. Apparently the A10-3T is kind of pushing the limits of that casing.
 
Top