5 or more stages

[Bazookadale]

Well as long as we're being technical - Apollo was a 3 stage vehicle - which was boosted by the 3 stage Saturn.
What ? - that's not technical, it's just nerdy - Oh well!

Technically the Apollo was a 6-stage vehicle:

S1: S-1C
S2: S-II
S3: S-4B
S4: SM
S5: LM (DS)
S6: LM (AS)

 

[gerbs4me]

Just had a quick question about FAA stuff. If my rocket weighs less than 1500g and has less than 125g of propellent I do not need a waiver or notification if I'm flying at my own launch?
I usually fly my bigger stuff with my club.

Thanks

 

[wetmelon]

Just had a quick question about FAA stuff. If my rocket weighs less than 1500g and has less than 125g of propellent I do not need a waiver or notification if I'm flying at my own launch?
I usually fly my bigger stuff with my club.

Thanks

Sounds right to me, but I'm not certified. Check the NAR website for more info.

Also, just because we can... I simulated a 6 stage C6-0 rocket using my 3D printed rockets that can stack boosters. It's completely silly and I would fully expect it to fail miserably, but it's theoretically possible, even with TWR > 3 on the first stage.

 

[fleafrier1]

This is only a two stage rocket, but I think this guy's design shows a lot of potential. 5 D12's put out around 10 lbs. of of thrust. He could have had a stack of 10 more D12s in the sustainer and likely no problem boosting it sufficiently for safe flight.

https://www.youtube.com/watch?v=86tTsPi0FPc

 

[green dragon]

5 D12s have an initial thrust of 9 lbs each = 45 lbs. A cluster of 10 will safely fly anything even semi-modroc ( though 10 will require a waiver due to being over the propellant weight ). 4-5 lb on 10 Ds is a very realistic flight, been there, done that.
For multi staging, just for grins, since not sure of a practical reason, with larger, longer burn motors available, and we're talking black powder anyways ( ie: low ISP and large mass fraction ). I'd go with a rack rocket - 5-7 stages, and enjoy the thrill of the staging.

 

[fleafrier1]

At snow ranch I've seen a guy fly a four stage rocket powered by E12s. IIRC, it was a mile high black powder attempt. The first stage burn was a little shaky, but it got off and staged at what appeared to me to be maybe a little over 100'. After staging of course, it rapidly accelerated, burned for 9 more seconds, and flew well out of my visual range. I don't know what diameter it was, but it would have been nice to know, because it seemed pretty clear that a fifth E12 would have been too much. I think any more and you might need some sort of cluster to get the stack moving.

I once built a pretty quick & dirty 3 stage 18mm minimum diameter rocket and launched it on 3 C6s, because I was curious about how far you could go with BP staging, too. It was right around 100 grams pad weight. It dropped the first stage (just the first motor) at maybe 200' and then really accelerated from there. After burnout, it was pretty much out of sight and of course, I never found it. I remember the ejection charge from the C6-7 at the top was barely audible. It flew great, but my feeling after that flight was also that one more motor would be too much. There is definitely a point of diminishing returns when stacking long burn BP motors.

My impression from those two flights is that when trying to take it as far as you can go with this, you shouldn't necessarily pick the highest impulse motor for your first stage, but instead the one with the best thrust curve for heavy lifting. I don't know exactly what would work best for 24mm powered birds because I've never tried to build one like this, but I'd guess if you went minimum diameter, 3 D12s boosting 2 E12s for a total of 5 stages would work. For an 18mm bird, I'm fairly certain that 2 B6s boosting 2 C6s (4 stages) would fly. In fact, I'd bet you could trim an inch off the empty part of the case at the front of the B6 booster motors and then maybe even add a 3rd one, but of course you would be modifying motors, and could not fly at sanctioned launches.

 

[mollwollfumble]

Back again. I built and flew a six stage rack rocket using six C6s. The tops of the rack rod cage were glued directly to the corners of a square nosecone. No recovery mechanism. Total parts cost (excluding motors, glue and paint) about $15. The following is before painting.


On first launch things went badly wrong. The first stage went "pop" instead of "shhhh". The second stage spat out its nozzle. Third and higher stages didn't fire. 6 of the 8 glue joints of the bottom of the rack cage failed, one of the vertical rods split at the bottom and the top of one rod came loose from the nosecone.

I glued the bits back together, reloaded motors, strengthened the top by wrapping it with nylon fishing line, strengthened the bottom by wrapping it through holes in the fins with copper wire. Total weight after repair, including motors, 201 g.

Second launch things went almost perfectly. All six stages fired. The rocket didn't disintegrate. The trajectory was a smooth arc, starting to descend as the 6th stage was firing. Stage separation caused no path deviation. Maximum altitude wasn't great, between 500 and 1000 ft whereas calcs suggested more like 3000 ft. I guess the build accuracy has to be better to ensure that it flies almost vertically. The rocket was not recovered.

That's good enough for me to try more stages next time. For more than six stages I need a more powerful first stage.

> Try a 3D printed rocket! (Pm me)

The next flight will have a 3-D printed four-lobed nosecone. Each lobe will contain the end of a rack rod. It's already printed.

 

[JStarStar]

So in other words, let's just light off six motors. Okay.

 

[adrian]

There's usually a very short delay between one stage burning out and the next one igniting. During this time the rocket begins to decelerate and tip over. By the time 12 stages have done their work, the rocket is quite likely to be pointing either horizontally or down. 30 stages will almost certainly end with a powered descent.

Moreover, each stage carries with it a chance that it will fail to ignite the next stage, and if any one of them fails to ignite then the upper stage (with the ejection charge and parachute) won't ignite either.

On first launch things went badly wrong. The first stage went "pop" instead of "shhhh". The second stage spat out its nozzle. Third and higher stages didn't fire.

...

Second launch things went almost perfectly. All six stages fired. The rocket didn't disintegrate. The trajectory was a smooth arc, starting to descend as the 6th stage was firing.

So, as I said...

Of course, if you're not bothered by minor details like the Safety Code (specifically "10: Recovery System. I will use a recovery system such as a streamer or parachute in my rocket so that it returns safely and undamaged and can be flown again, and I will use only flame-resistant or fireproof recovery system wadding in my rocket"), and if you actually want the rocket to come down in a powered ballistic dive, then by all means continue. Just don't expect any approval from anyone here, or for that matter from your local law and fire officers.

 

[Astro-Baby]

Bit late to this thread and am hardly expert, i would rate me as a space chimp, but i recall someone telling me they built a semi scale Rhinebote with 5 stages. I did a search on here but couldnt find the post. It was in response to my proposed rhinetochter build ( now in planning stage ie i have some drawings together ). Anyway i seem to recall the poster putting a five stager together which worked but the upper stage was lost, no surpises there I guess. It flew so far that the top bit just went into the void.

So it can be done to five stages so long as there is an acceptance of losing the ship. Me..no thanks ai put a lot of work into my birds and would hate to build with an opening position of knowing you will most likely suffer loss even assuming all five stages work out. To date ai have only had one fully successful two stage launch. Al the others have been lost or destroyed at staging.

 

[JStarStar]

Certainly any 'rack rocket' launched with *no* recovery system is, by definition, in violation of the MRSC.

And no, no RSO in the world would buy the argument the upper/sustainer stage is designed to utilize 'featherweight recovery.'

Plus a launch designed to eject 4 or more loose motor casings certainly pushes the spirit if not the letter of the MRSC in just about every sense.

The ejection of loose motor casings is essentially a 'shady area' grandfathered in from the very early prehistoric days of model rocketry when it was used fairly commonly in 'featherweight' models and also early boost gliders. It was *partially* banned, at least for use in competition, when the Sporting Code was written to specifically forbid the use of free-falling motor casings. Since there were already models designed to eject free-falling motor casings, the general attitude seemed to be, 'oh well nobody has gotten killed so far so i guess let's just not worry about it.'

Maybe it's time to re-think an amendment to the Safety Code for permissible NAR SPORT flying to forbid them as well.

With larger-size D, E and now F BP motors avaiable, if people keep launching rockets designed to kick expended motor casings, it's probably just a matter of time before somebody's ejected 29mm F motor casing comes auguring in from 2000 feet and drills a hole right through somebody's car roof -- or somebody's head.

 

[samb]

Don't forget:

The OP is an Aussie so FAA and NAR rules mean nothing. I hope he has his own little piece of the Outback to conduct his artillery experiments.

From the initial post: "The second reason I'm on the forum is that I want to work up through a series of tests to massively multistaged (eventually to at least 12 stages and possibly as many as 30 stages)." He's really just getting started.

He's retired so I'm inferring that that means he's reached a certain age with all extremities, most brain cells, and determination intact.


mollwollfumble - Sorry I have nothing constructive to add other than good luck and stay safe.

 

[adrian]

Bit late to this thread and am hardly expert, i would rate me as a space chimp, but i recall someone telling me they built a semi scale Rhinebote with 5 stages. I did a search on here but couldnt find the post. It was in response to my proposed rhinetochter build ( now in planning stage ie i have some drawings together ).

Take a look earlier in this thread. I also mentioned my four stage Rheinbote there. And also someone else's five stage Comanche. Both of them lost their three uppermost stages, which left the other guy with enough spare boosters to buy another Comanche and do it again, and me with only the first stage booster from Rheinbote.

So it can be done to five stages so long as there is an acceptance of losing the ship. Me..no thanks ai put a lot of work into my birds and would hate to build with an opening position of knowing you will most likely suffer loss even assuming all five stages work out. To date ai have only had one fully successful two stage launch. Al the others have been lost or destroyed at staging.

The other condition is that the first stage must have plenty of power to lift the dead weight of the rest of the stages. Rheinbote had six motors in its first stage which is why the fourth stage was heading up when it ignited, unlike mollwollfumble's six stager which was headed down when its final stage fired.

 

[Astro-Baby]

Ah ha...sorry Adrian, I thought it may have been you with the Rhinbote but damned if I could find the post. I thought it was a five stager from memory but i did recall bits of it were lost and yes of course a big stager would need a lot of whoomf to get the deadweight moving. I considered building Rhinetochter to be a two stage but decided on the basis that every two stager so far has come to grief I would play a bit safe. Its a mad enough build as it is and will quite possibly skywrite etc without adding more worry to the whole program

 

[JStarStar]

Don't forget:

The OP is an Aussie so FAA and NAR rules mean nothing. I hope he has his own little piece of the Outback to conduct his artillery experiments.

From the initial post: "The second reason I'm on the forum is that I want to work up through a series of tests to massively multistaged (eventually to at least 12 stages and possibly as many as 30 stages)." He's really just getting started.

He's retired so I'm inferring that that means he's reached a certain age with all extremities, most brain cells, and determination intact.


mollwollfumble - Sorry I have nothing constructive to add other than good luck and stay safe.

Yep, following the NAR MRSC is not just a silly fixation on following rules or keeping US legal or administrative forces off his back, the MRSC is based on common-sense precautions to avoid dangerous situations no matter where you are flying.

If the OP has a massive massive flying area where rockets taking off half-cocked in crazy directions aren't going to bother anybody, and he's got a bunker or something where he can jump so getting hit with a 12-stage rocket is survivable, well go ahead and knock yourself out.

 

[mollwollfumble]

> The OP is an Aussie so FAA and NAR rules mean nothing. I hope he has his own little piece of the Outback to conduct his artillery experiments.

As soon as I get up to a total power of G, or a height above 2500 ft, I'm going to join the Tripoli rocket club so I can use their outback launch site. Then I have to satisfy their laws in order to pass successive certification through more powerful rocket engines. So far I've been using a place in a near-city national park where model planes are regularly flown, and where others have occasionally fired off rockets.

> Practice has shown that sequential ignition of more than four stages is problematic and becomes more a matter of sheer luck than operational success. The 'rack rocket' things basically just prove you can tape 5 or 6 (or more) motors together and get 'em to light.

That's what I'm trying to test. Now that I have tried in turn, with C6 black powder:
1 stage - kit rocket
3 stage - static test in shed
4 stage - burn-down tube
6 stage - rack rocket

I think I'm ready to try out 10 stages.
Stage 1 - E12-0
Stage separation after stage 1 as for usual two stage rocket (as described in Estes Classic Collection)
Stages 2 to 10 - C6 rack rocket

The total rocket lift off weight will be ~290 grams, which isn't much. It's not the sort of rocket that would do a lot of damage if it hits anything. After 10 stages it's down to ~50 grams. The upper 9 stages will be built from four 5 mm OD carbon fiber tubes, with fins and supports from 0.8 * 25.4 mm carbon fiber section. The tubes will slot into four lobes of a nosecone that I've had 3-D printed.

The overall aim of my project here is that of minimising fuel usage (and hence weight) to given height. I calculate that, after a first brief high-thrust phase, the burn time has to be very long in order to keep air drag down. The three ways to get a long burn time are home-made motors, hybrid motors, and massive multistaging of commercial hobby rocket motors. Hobby rocket motors tend to have burn times near 2 seconds, which is nowhere near long enough. 30 to 70 seconds burn time would be better.

The aim at this stage is not for great altitude, but to see whether I can overcome the tendency for it to fly horizontal after four or five stages. If I can get my 10 stage to still be rising during the 7th stage I'll be completely happy.

After 10 stages in black powder, my next step will be to run a static test in shed of an electronically timed ignition of a two-stage G80 composite motor, then slowly build up to more G80 stages.

 

[mollwollfumble]

Any advice on changing motor diameter at a stage separation, say from 24 mm diameter Estes to 18 mm diameter, both minimum diameter design. It must have been done many times. Can I do it without "gap staging"? Any tips?

 

[Mr Rocket]

Any advice on changing motor diameter at a stage separation, say from 24 mm diameter Estes to 18 mm diameter, both minimum diameter design. It must have been done many times. Can I do it without "gap staging"? Any tips?

A standard 18mm casing will actually fit inside a 24mm casing for multistaging. This is used in the Estes Design of the month Tao (Not the production version which is a completely different rocket). There are several threads on the forum about this rocket, including mine https://www.rocketryforum.com/showt...lized-2-stage-rocket-stable&highlight=finless. Still waiting to launch it though. My last 5 launch attempts have all been scrubbed by wind or rain.:sad: So I cannot vouch for it's reliability.:confused2:

 

[BABAR]

The ejection of loose motor casings is essentially a 'shady area' grandfathered in from the very early prehistoric days of model rocketry when it was used fairly commonly in 'featherweight' models and also early boost gliders. It was *partially* banned, at least for use in competition, when the Sporting Code was written to specifically forbid the use of free-falling motor casings. Since there were already models designed to eject free-falling motor casings, the general attitude seemed to be, 'oh well nobody has gotten killed so far so i guess let's just not worry about it.'

Maybe it's time to re-think an amendment to the Safety Code for permissible NAR SPORT flying to forbid them as well.

With larger-size D, E and now F BP motors avaiable, if people keep launching rockets designed to kick expended motor casings, it's probably just a matter of time before somebody's ejected 29mm F motor casing comes auguring in from 2000 feet and drills a hole right through somebody's car roof -- or somebody's head.

I use motor eject regularly for C and sometimes D engines without a streamer. Since the expended casings are unstable, I have figured they tumble and would not come up to significant velocity to cause damage or injury. Those F motor casings look pretty substantial. I wouldn't want one coming down on my head even from 100 feet.

My main concern has been risk of fire. I have personally seen the burning propellent residual chunks (or at least something hot) on the ground at the impact site of an expended C motor cause a very localized grass fire which was easily put out (it was cut bermuda grass in the middle of winter in the middle of a soccer field.) The impact of the engine with the ground "breaks" the chunks off and they fall through the front wide open "mouth" of the casing onto the surround ground. It might have been bad had I not been able to get there quickly. Suddenly the restrictions on engine eject models in drought conditions implied by rocketry clubs made a whole lot more sense.

I'm not sure how much a streamer helps, I guess any additional time to let the residual engine contents cool helps. I haven't flown rack rockets but I think streamers might be a little bit hard to incorporate and still get reliable separation/sliding of the engines out the back.

 

[JStarStar]

The CP of an expended motor casing, since it is a cylinder, should be precisely at the midpoint of its length.

Presuming ALL the propellant burns out, the only weight inside the expended casing is the nozzle at the tail end. This will shift the CG measurably from the midpoint toward the tail end.

Thus an expended motor casing should be at least theoretically stable -- if traveling in reverse, toward its tail end.

Of course motor casings do not have adequate corrective surfaces to make them reliably stable, but I would still hazard a guess that dropped from sufficient height, through reasonably non-turbulent air without side currents to induce lateral spins, motor casings would generally tend to assume a mostly-stable attitude and dive tail-end-first.

 

[Crazy_Rocketeer]

Well apperatly these people should get sued
https://copenhagensuborbitals.com/tm65.php

 

[mollwollfumble]

I fired off my six-stage rack rocket a month ago now. It was a limited success, by the fifth stage it was flying horizontally. But it was sufficiently successful that I've now built a 10-stage low-power black powder rocket. The first stage is separate (E12-0) and stages 2 to 10 (C6) are contained in a rack rocket. Total lift-off weight 345 g. This is it after assembly and before painting.


Nose-cone is 3-D printed. All other parts are carbon fibre, either made from 5 mm OD 3 mm ID tubes or 25*0.8 mm section.

I won't be able to launch this 10-stage until the bushfire season is over, and we're right in the middle of it now.

 

[rstaff3]

I would predict this will end up horizontal too...but if the conditions are fire-safe, go for it! Carbon fiber and 3-D printing seems entirely too high tech for a single use rocket

 

[shreadvector]

You are wrong. It will not "end up horizontal".


It will only remain horizontal for a short while and it will arc over and point downward under thrust and hit the ground with one or several motors firing while in or on the ground. if it is not "in" the gorund and it is "on" the ground, and the remaining motors continue to fire, it will skitter and bounce from place to place until motors stop igniting or are all consumed. Whatever is in the flaming path will be ignited. Hopefully the launch is conducted on a completely brush free desert plain (with no automobiles located where they might be burned or destroyed should they be hit by the crashing "rocket").

I would predict this will end up horizontal too...but if the conditions are fire-safe, go for it! Carbon fiber and 3-D printing seems entirely too high tech for a single use rocket

 

[rstaff3]

You are wrong. It will not "end up horizontal".


It will only remain horizontal for a short while and it will arc over and point downward under thrust and hit the ground with one or several motors firing while in or on the ground. if it is not "in" the gorund and it is "on" the ground, and the remaining motors continue to fire, it will skitter and bounce from place to place until motors stop igniting or are all consumed. Whatever is in the flaming path will be ignited. Hopefully the launch is conducted on a completely brush free desert plain (with no automobiles located where they might be burned or destroyed should they be hit by the crashing "rocket").

I assumed the fire proof launch area and I guess I jumped the gun as I agree with your assessment. Even if the E12 keeps it perfectly vertical, there is no way those C6-s will. My emoticon related to the materials not the concept.

 

[shreadvector]

Yes, your message was clear to me, but I always like to "say things out loud" for the rest of the folks reading this in case they think this is a smart or useful experiment.

I assumed the fire proof launch area and I guess I jumped the gun as I agree with your assessment. Even if the E12 keeps it perfectly vertical, there is no way those C6-s will. My emoticon related to the materials not the concept.

 

[rstaff3]

Yes, your message was clear to me, but I always like to "say things out loud" for the rest of the folks reading this in case they think this is a smart or useful experiment.

Yeah, I can't argue with you on that.

 

[Airobert]

It WILL turn towards the ground. All rockets do unless they have active stabilization. It has to do with the CG, CP and thrust. It's the old balance the broom in one hand trick-it can't be done without active stabilization.

https://en.wikipedia.org/wiki/Pendulum_rocket_fallacy

https://en.wikipedia.org/wiki/Gravity_turn

Here is THE book on the subject.

https://arapress.com/vts.php

They also have other books.

https://arapress.com/space_products.php

 

[JStarStar]

this entire thread fits into the "chimpanzee playing the accordion" category in that it probably CAN be done, yet gives no indication why anyone would ever want to.

 

[shreadvector]

Bumping thread since we just got the news about the big fire. No confirmation that the fire was caused by the clearly dangerous rocket discussed in this thread that would obviously hit the ground whilst still burning.