Anyone build a "lowish and slowish" two-stager?

[Donnager]

I have a LOC 5.5" Wolverine kit with a 54MMT, which didn't come with an Electronics bay/deployment section. I was looking at making it dual deploy, but was thinking that for not much more money (excluding electronics, I have a good stock of them), I could stack two Wolverine airframes and have a two stage that would have PLENTY of room for playing with electronics. So much room, that I can pick/choose what makes sense rather than Jam the goodies into the only space that is left.

Seems I can make this be a pretty loud but fairly low combination as a two stage. H/I's would get it to around 2500-3000, J's to 4000-6000, and K/J to 5000-7,000 ish. The interstage coupler will just be a 5.5" bay with an aluminum liner where it could be cooked by the sustainer. Booster would use motor deploy with electronics backup. The sustainer would be standard dual deploy. There will be enough electronics that I can fire a separation charge, but haven't decided.

First thought would be to put an RRC3 in the interstage and let it fire the separation charge and be the ejection backup to motor on the booster. Sustainer would have either an easy timer for the ignition and an RRC3 for dual deploy, or an RRC3 to light the sustainer and control dual deploy.

I have the Apogee Terrier booster with the cardboard Sandhawk 54mm body with a 29MMT, and a 54mm Mac canvas Arcas with a 38MMT. Both of these should be dual deploy (right now, just the canvas version is) and finding the right day to fly this combination is difficult. Anything outside our field is in the woods, with a <50% chance of recovery.

The 5.5" is an effort to make a two-stage that could be relatively reliably flown at our field. I also like the sound of a larger air started motor lighting near or below 1000'.

Just wondering what similar projects have been done.

 

[Charles_McG]

My entire sounding rocket fleet has flown on the idea of staging as low as I think I safely can, with sustainer apogee between 2,000-4000'. Motors are 29-38mm. I aim for a booster TTW of approximately the crosswind speed. Call it 12-15G. With a short burn CT White Thunder, that puts burn out at about 300' and sustainer ignition at 500-1000'. I fly eggtimer Quantums and Protons - the Proton handles the tight (sub second) timing better, imho.

 

[waltr]

I did this with a couple of Balsa Machining 3" school rocket kits.
Booster is the short kit with simple motor ejection.
Sustainer is the longer kit with a bay mounted just above the motor tube and along side a Stuffer tube.
Total weight around 1000gram so still Class 1. Been running a G74 in booster and D15 in sustainer to keep altitude low (we have a smallish field). Staging happens at a few hundred feet and easy to see.
A G74 is only about 6.5:1 TTW so slightly a bit low. Using Velocity lock out of 150 ft/sec at Motor ignition. So far this has worked. Only time things went bad is when sustainer motor took over 4 seconds to come up to pressure. Rocket had lost air speed and arced over.
Cris at Eggtimer recommends a 10:1 TTW to ensure enough velocity to keep the stack going straight up until sustainer ignites. From experience this is a reasonable guide line.

I don't recommend going too slow off the rail. Pick a booster motor with eough speed off the rail to prevent wind-cocking and to have a burn-out velocity over 150 ft/sec. More can be better if sustainer takes longer to light. Remember that a composite does not light instantaneously, consider this when doing sims and choosing times.

Bought extra coupler tubes & bulk heads to make an ISC.
Used a Eggtimer Quantum for Air-start and Apogee deployment. Seperation is done when sustainer motor starts.
This worked well and as simple as can be. The 24/40 D15 has not done any damage to the ISC but a larger motor might.

I do want higher altitude so will be putting an Eggtimer Proton in. This will do Seperation charge, motor air-start, Apogee deployment then fire a cable cutter to deploy main chute. Just did cable cutter testing Saturday single stage and it worked. Next month will run 2-stage with Proton.

This allows one ebay and altimeter to do the four functions without wire disconnects.

Putting an altimeter into the ISC on a 5.5: would be easy and just doing a single deploy should be fine if booster apogee is low. Full DD could be done with a cable cutter to keep it simple if desired.

Key is to sim, sim and sim again.

 

[Donnager]

My entire sounding rocket fleet has flown on the idea of staging as low as I think I safely can, with sustainer apogee between 2,000-4000'. Motors are 29-38mm. I aim for a booster TTW of approximately the crosswind speed. Call it 12-15G. With a short burn CT White Thunder, that puts burn out at about 300' and sustainer ignition at 500-1000'. I fly eggtimer Quantums and Protons - the Proton handles the tight (sub second) timing better, imho.

Thanks. I don't have a good soldering station and I have been known to overheat some sensitive parts, so I'll save the parts I may destroy, and stick with pre-assembled electronics.

Mine won't look much like a sounding rocket unless there's a goony version. I've thought about playing with this in a smaller frame, but the extra workspace is really hard to turn down.

I think I'll go ahead and get the second kit and start laying this out.

Cris at Eggtimer recommends a 10:1 TTW to ensure enough velocity to keep the stack going straight up until sustainer ignites. From experience this is a reasonable guide line.

Thanks, I haven't heard this guideline, but all my sims where I was comfortable with the plots were between 11 and 20 TTW. Nice to know I was on the right track.

 

[Charles_McG]

Ute Tomahawk comes close to a goony.

 

[waltr]

Even if you are not going to build Eggtimers do go to the web site/support/ Quantum & Proton and down load the air start documents. They are a very good read on different ways to setup and have good suggestions.

Also, there is a Cluster & Multi-stage forum that is worth going through and reading all the mulitstage air start threads.
Good to see what can go wrong and how to consider safety.

 

[Donnager]

Ute Tomahawk comes close to a goony.
View attachment 545288

Similar in size to a LOC Norad PRO Maxx with an extra set of fins. I will say I thought about making another small two-stage when I built my Pro-Maxx.

The double stack Wolverine would look something like this (plus interstage coupler and top e-bay)-- Should be utilitarian enough. I'll have to come up with a nice sticker set or neat paint job to go with it.

 

[b.wieting]

I've flown LOC Mini and MegaMagg, both dual deploy, each modified w/ an inserted E-bay.

Now I've been thinking about stacking the Mini atop the Mega booster using a modified Mega NC for the interstage. Maybe a crazy idea...

 

[Donnager]

I've flown LOC Mini and MegaMagg, both dual deploy, each modified w/ an inserted E-bay.

Now I've been thinking about stacking the Mini atop the Mega booster using a modified Mega NC for the interstage. Maybe a crazy idea...

A full stack picture of what I have now. It is about half painted currently. I plan to take a couple pictures of the coupling between the stages and the sustainer motor mount. This was the biggest area of change in the rocket(s). I'll try and explain what I did and answer any questions. It may be a day or so.

 

[Handeman]

I'm putting together my first 2 stage. The sustainer has 38mm MMT and flown before. Will probably fly on 38 4G EX motor. The booster will have a 75mm MMT and fly on 75mm 1 or 2 grain EX, or maybe 4g 54mm EX. It should stay below 7500 ft. I'm not sure if that meets your "lowish and slowish" criteria.

 

[Donnager]

Mine is painted. Decals need to set, and I'll finish it. Just lacks final holes for altimeter, and mounting same.

Some sims based on actual weights--Still need a few tweaks on sustainer ignition timing, but they are close:
Booster/Sustainer/Altitude (ft)
I500/I280DM/2,871
I500/H550/1,984
J800/I280DM/4,515
K550/J250/5,571--Peak velocity on the sustainer is only 440MPH on this one
H550/J250/2,239
H550/H550/1,052 *Gulp*

 

[b.wieting]

Beautiful! (Like the rocket rack too...).
Tracker, like Eggfinder?

 

[Donnager]

The sustainer will have a tracker in it. Just a beacon, not GPS enabled.

Like the rocket rack too...

You should see behind me when I was taking the picture. The area could use a little policing. Mostly stuff that can't fit on a rack.

I'll get some pictures of the motor mounts, the stage transition, and the upper bay for lighting the sustainer and separating the stages, so you can see what I did. The biggest change was moving the aft centering ring forward about 4" or so while keeping the MMT and the body tube rigid with that void.

 

[kswing]

I've done something along these lines. It's 4" blue-tube with the staging electronics in an e-bay next to the sustainer MMT. I used an Eggtimer Quantum to handle the staging and an Eggtimer Quark for the DD on the sustainer. The booster was simply motor eject. I moved the aft CR on the sustainer up a few inches for the inter-stage coupler. It got about 4300' from an I540 to an I345.

Here's a link to the build thread: https://www.rocketryforum.com/threads/blue-stage-high-power-two-stage.143899/

 

[Donnager]

Alright... Down to business.

The nose cone of the booster is a LOC coupler with stiff internals. The top half has been lined with 0.040 aluminum for flame impingement and added weight. It has an Altus Metrum Easy Mini as a backup to the motor--I have no idea how to figure this delay, so I've added redundant apogee here.



The sustainer is a Dual deploy 5.5". Basic electronics are an Altus Metrum Easy Mini with a Missileworks RRC2L as a backup.


Now, the back of the sustainer. The rear centering ring had to be moved forward a good bit. I used 4.5". The rear of the rocket is the original LOC tube, with a layer of epoxy and a LOC tube coupler under the fins. There is also T-T fiberglass on the outside to be sure the sustainer can stays rigid and round.

The fins had to be re-cut to be able to adequately tie in to the motor tube. The 4"+ 54mm tube extension was not a good idea in my mind, especially if motor reducers were used. I installed a 75mm motor mount tube with two centering rings for the extension, with the front one being epoxied to the rear 5.5" centering ring. A 54mm flanged Aeropack retainer was added to finish it.


The sustainer will be separated by and lit by an Altus Metrum easy timer located in the side of the rear of the rocket.


The Easytimer will be able to use either a LiPo or 9V battery. Conduit is in the center of the bottom of the electronics. It is very close to the center at the back of the sustainer.

 

[Donnager]

Wow at spherical abberation/lens distortion.

 

[waltr]

Looking good. I like the idea of the 54mm MMT inside a 75mm tube to ensure the bottom end of the MMT is rigid.

Is the easy timer in the lower end of sustainer going to do separation and motor ignition or just ignition and motor separates?
Looks like you are planning AT motors. The igniters will need some current/Voltage to fire.
Make sure you ground test the igniters to ensure the battery chosen with fire it.

For sustainer ignition I made igniters with shooter's wire and 40ga nichrome dipped in QuickBurst ProCast. Then use a 300mA-Hr 2S 30C LiPo for the Eggtimer Quantum. This easily fires the igniter.

 

[Donnager]

Looking good. I like the idea of the 54mm MMT inside a 75mm tube to ensure the bottom end of the MMT is rigid.

Is the easy timer in the lower end of sustainer going to do separation and motor ignition or just ignition and motor separates?
Looks like you are planning AT motors. The igniters will need some current/Voltage to fire.
Make sure you ground test the igniters to ensure the battery chosen with fire it.

For sustainer ignition I made igniters with shooter's wire and 40ga nichrome dipped in QuickBurst ProCast. Then use a 300mA-Hr 2S 30C LiPo for the Eggtimer Quantum. This easily fires the igniter.

The Easytimer in the sustainer, will do both, separation (when booster goes out) and ignition (predetermined time, dependent on combination).

I don't have an issue with igniters. I use doped e-matches, not aerotech igniters (which I have had issue with), usually with quick burst or something hotter. I have lit very big motors very quickly with these. Pretty much every ground launch over the last two-three years for me has been an e-match test.

Thanks.

 

[waltr]

Those igniters will be great.
Looking forward to the launch report.

 

[David Schwantz]

I have the ultimate lo and slo 2 stager. It is BP D motors. The second stage lights at about 50', almost right in front of you.

 

[b.wieting]

Estes Boosted Bertha is also a great kit for low and slow.
Our scout troop built/flew it as a troop rocket at our rocketry campout at FAR last February.