5 or more stages

Dont know about a chimp playing an accordion - I dont much like accordion music anyway but I reckon a dog that spoke Norwegian might of some use

OK, I started this thread, but had to wait until the bushfire season finished here to launch the 10-stage rocket.
To recap, the first stage was a separate E12 and the following 9 C6 motors were in a rack rocket.

Launch failed. A CATO on first stage didn't help. Second stage worked perfectly. Third stage veered off course for reasons still unknown - possibly fin damage, inadequate stiffness or motors shifting within the rocket body. It nosedived into the ground on the sixth stage, but all 10 stages fired.

I recovered all parts and am rebuilding it. Have done more flammability and strength tests, but have only discovered that the initial design seems to be OK. The CATO could have been caused by dropping the motor.

The 10-stage is the small rocket in the following photo (the larger one will be a single stage H, then hopefully a 5-stage G high-powered)

The failed launch is on this video
https://www.youtube.com/watch?v=IARwktKIHc4

Guaranteed failure. Smart people don't do this stuff. Quit wasting your (and our) time.

> 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 ground and it is "on" the ground, and the remaining motors continue to fire.

Your prediction was 100% accurate. I still don't know why. Mind you, the first stage CATO didn't help.

I am a bit curious how you will recover a rocket with H and multiple G motors which is basically a cardboard tube with no weight. I launched a two stager with two C motors last year and, unsurpisingly, after staging, we never saw it again.

I have no idea how high an H motor will loft what is basically a paper tube with some more motors in it but even assuming shockingly poor performance the final G motor will loft an empty tube quute some distance and given the fact it will already be very high i cant see how you will ever keep sight of it.

I know this sort of stuff is there to be done, maybe, but I just cant see how you will track the rocket. Also given my own experience with two stagers failing o the ectent k have given up on staged rockets I just cant see how you could ecpect to get all five stages working perfectly in one go, plus its going to be expensive for sure.
Possibly some kind of electrical air start would help to guarantee upper stage ignition before burn out of a lower stage to ensure separation before the lower stage has slowed down.

It all looks very unstable and reminds me a bit of the v3 gun.....it might be doable but at what cost and if altitude/speed is your thing it would seem to be a hard way to do it.

He has no plans to recover any of it. He just wants to bolt 6 or 10 or 68 or 328 motors together nose to nozzle to nose to nozzle, light 'em off, and see what will happen. Like a kindergartner lighting off firecrackers.

I will tell you what will happen: some of the motors will light, some won't, very quickly the "rocket" will dive into the ground, and after that it's only a matter of what gets hit or what gets set on fire.

At least the extreme level of skepticism I'm encountering on this forum tells me that launching a 10-stage rocket is not "reinventing the wheel".

As for "must satisfy US laws", I'm waiting for Jamie, Adam, Grant, Carry and Tory to be arrested as they break very many US rocketry laws.

JStarStar said:

Guaranteed failure. Smart people don't do this stuff. Quit wasting your (and our) time.

Click to expand...

That hurt. My applied maths ability, my PhD in Engineering, and my lifetime of work in engineering research says that I am "smart people". I applied Goddard optimisation to generate the design, which involved first deriving the relevant differential equations and then writing software to solve them.

The solution says it should succeed in reaching about 1.75 km high, that's nearly 5,800 ft, not high but I'm doing this low power first to prove that massive multistaging can be done, not to break any altitude records. Stability analysis says that first two stages are unconditionally stable and that stability improves as more motors are shed towards the midpoint of 5 stages. Deviation from vertical should be not much worse than for a single motor with the same thrust duration of 19 seconds.

Perhaps I should add that in Australia it is much more difficult to buy solid fuel hobby rocket motors with long duration burns than it is in America.

> I am a bit curious how you will recover a rocket with H and multiple G motors which is basically a cardboard tube with no weight.

No weight I wish.

Both the single stage H and the four/five stage G will be equipped with a proper parachute, and also an altimeter that sounds an alarm signal on landing - so I can find it using the noise generated. And they will be fired in a sheep paddock that is treeless and large in extent.

For later rockets, 433 MHz tracking looks good, some lightweight trackers normally used for tracking birds work over distances exceeding 10 km.

> i cant see how you will ever keep sight of it.

I'll be launching in a group of competent rocket watchers, who seem to have better sight than I have.

> Possibly some kind of electrical air start would help to guarantee upper stage ignition before burn out of a lower stage to ensure separation before the lower stage has slowed down.

Good point. I'll keep that in mind, I was thinking of doing the opposite to keep the air drag to its optimum value.

> it might be doable but at what cost and if altitude/speed is your thing it would seem to be a hard way to do it.

OK. Let me re-introduce you to Goddard optimisation. The solution to the problem of minimum fuel to maximum altitude was found mathematically by Goddard. The rocket ascent needs to go through three phases. The first phase is where the thrust is as large as possible, the weight of this rocket stage should be 30% of the total rocket mass, and a single stage for this phase suffices. The second phase has the thrust tuned to a low level for a long burn time to keep the rocket speed at optimum - optimum speed occurs when the downward force due to air drag is equal to the downward force due to gravity. The third phase is coast to maximum altitude.

For minimum fuel consumption the second phase MUST have a long burn time. To get a long burn time you need either to multistage solid rocket motors for a large number of stages, go to liquid fuel, or break the law. The stability problems encountered in multistage rockets can only be overcome by placing the fins adjacent to the first or second stage, but attaching them structurally to the last or second last stage. Got it so far?

As for cost, the equations predict that 100 km altitude for a total motor cost of $550 and total motor power in the L range is doable. But I DON'T expect you to believe that, I have trouble believing it myself, and won't believe it until I do it.

mollwollfumble said:

my PhD in Engineering, and my lifetime of work in engineering research says that I am "smart people"..

Click to expand...

Having a degree and being smart are 2 different things

I watched Mark Pflafkin's 5 stage D rocket fly at the first SpudRoc event we had here. It flew straight up, no problems. First stage, however, only lifted the rocket about 10-15 feet, that had us worried for a second but it went on to stage successfully and we recovered all the stages One of the benefits of launching in a desert

I think this is a cool concept but to be able to test and fly your H and G rocket you will need to launch it at a club due to club rules. Right??


Sent from my iPhone using Rocketry Forum

More power to ya! I wish success and learning to you.

Just curious. Why are the fins so small? They barely look adequate for a single stage rocket, let alone the multiple stages you are using here.

Mr. mollwoolfumble, you are having entirely too much fun. Such activities are no longer tolerated here in these United States for the good of the children. If you want to see what the children are up to, you must look no further than YouTube. :duck::no::rant::rofl:

> Just curious. Why are the fins so small? They barely look adequate for a single stage rocket, let alone the multiple stages you are using here.[/QUOTE]

There's no extra weighting in the nose, if that's what you're wondering. What's happening is that the motors extend all the way along the rocket shaft right up to the nose cone, and that means that the weight of stages 6 to 10 counterbalance the weight of stages 3 to 6, so fins only need to be the about same as would be required for a two stage. I've optimised the fin sizes so that stability for stage 1 and stage 2 is the same.

The fins for stages 2 to 10 are attached to stage 10 so are not shed as each intermediate stage is shed. That means that rocket stability ought to increase as more stages are shed. It's all confirmed by the Barrowman equations. If anything, I worry that later stage flight is too stable.

> I think this is a cool concept but to be able to test and fly your H and G rocket you will need to launch it at a club due to club rules. Right??

H yes. G no. I can launch G locally provided I don't enter controlled airspace or interfere with people or aircraft. For G, I use a public site that has a limit of 2500' AGL and is used as an unofficial (not club) model aircraft flying area and golf driving range.

> I watched Mark Pflafkin's 5 stage D rocket fly at the first SpudRoc event we had here. It flew straight up, no problems. First stage, however, only lifted the rocket about 10-15 feet, that had us worried for a second but it went on to stage successfully and we recovered all the stages.

Yes. 5 stages is about the limit when all the motors are the same size, though a successful 6 stage was recorded by Ken Good (1969). More stages than 5 and you need a more powerful motor as the first stage. For the last flight I used an E followed by 9 Cs. I had calculated that under the E's thrust it would reach 240 feet on the first stage, but it actually went much higher than that on first stage - I don't know why.

Rebuilt and flew 10 stage. No changes to design apart from extra hoop stress reinforcement at mid height. More care in the handling of motors. I considered changing the vertical rods to metal (titanium, aluminium, CuNi or stainless) but confirmed by calculation that all of them would add too much weight to the rocket so stayed with carbon fibre. Metal is not advisable in a public place anyway.

Crashed again. This time had a CATO on stage 4, it arched over on stages 5 and 6, and hit the ground on stage 8.

I need to sort through hypotheses as to why it crashed. Possibilities are:

1. Motor failure
1a. A percentage of black powder motors are guaranteed to fail, or
1b. Black powder motors only fail if subjected to poor handling - accelerations or moisture absorption.

2. Failure of multistaging method of using a single turn of sticky tape
2a. Intrinsic problems with sticky tape - lateral thrust on breakage, energy loss due to overpressure, risk of motor failure due to overpressure
2b. Sticky tape construction errors - lateral thrust due to doubling up tape near join

3. Problems due to multistaging
3a. side thrust because of misalignment of stages relative to one another
3b. energy loss because lowest stage ejected before combustion is complete
3c. time delay on startup of upper stage from glowing embers
3d. energy loss due to downward acceleration of ejected stage

4. Problems due to rack rocket concept
4a. Drag on vertical rods, lower cage and fins due to exhaust gases
4b. Changes in aerodynamics caused by burning of vertical rods, lower cage or fins
4c. Friction between ejected stage and vertical rods

5. Problems with build quality

Any comments? Suggestions?

H yes. G no. I can launch G locally provided I don't enter controlled airspace or interfere with people or aircraft. For G, I use a public site that has a limit of 2500' AGL and is used as an unofficial (not club) model aircraft flying area and golf driving range.

Click to expand...

Yes but you can not use more than 2 G engines total or have more that 125 grams of propellant in the rocket,Weighs more than 1,500 grams including motor and Uses a motor with more than 160 Newton-seconds of total impulse (an"H" motor or larger) or multiple motors that all together exceed 320 Newton-seconds or it is considered high power.

conman13 said:

Yes but you can not use more than 2 G engines total or have more that 125 grams of propellant in the rocket,Weighs more than 1,500 grams including motor and Uses a motor with more than 160 Newton-seconds of total impulse (an"H" motor or larger) or multiple motors that all together exceed 320 Newton-seconds or it is considered high power.

Click to expand...

He's not even in the USA. He's in Australia from what I gathered.

Well you asked about staging issues - I cant claim expert status, or even space chimp status really, but I did say up front that it would be a near miracle to get all stages to work ok. My experience with much simpler two stagers has been very bad - all of them have had issues and none could really be said to have flown straight up or even close. I have pretty much given up on a two stage 'out the box' but may give it another go with one of my own design. I think the real headache is the out of the box motors basic reliability. An electric air start might improve the odds but it may also end up being a bit heavy gen the large amount of motors and wire you would need. As I say I am not expert - just a meddler/tinkerer really but thats my gut feel for it based on (limited) experience.

Just in case you need to check your math on how many stages/engines you'll need to get to 100km. https://what-if.xkcd.com/24/

My experience with much simpler two stagers has been very bad - all of them have had issues and none could really be said to have flown straight up or even close.

Click to expand...

Do you know why?

Just in case you need to check your math on how many stages/engines you'll need to get to 100km. https://what-if.xkcd.com/24/

Click to expand...

Yes. I derived the same thing independently by solving the thrust equation in Excel before seeing that xkcd cartoon. What the cartoon says is exactly correct, give or take a few percent, for black powder rockets. It turns out to be false for composite propellant, but there are several subtleties with that that need to be discussed elsewhere.

> I need to sort through hypotheses as to why it crashed. Possibilities are:

1. Motor failure
1a. A percentage of black powder motors are guaranteed to fail, or
1b. Black powder motors only fail if subjected to poor handling - accelerations or moisture absorption.

2. Failure of multistaging method of using a single turn of sticky tape
2a. Intrinsic problems with sticky tape - lateral thrust on breakage, energy loss due to overpressure, risk of motor failure due to overpressure
2b. Sticky tape construction errors - lateral thrust due to doubling up tape near join

3. Problems due to multistaging
3a. side thrust because of misalignment of stages relative to one another
3b. energy loss because lowest stage ejected before combustion is complete
3c. time delay on startup of upper stage from glowing embers
3d. energy loss due to downward acceleration of ejected stage

4. Problems due to rack rocket concept
4a. Drag on vertical rods, lower cage and fins due to exhaust gases
4b. Changes in aerodynamics caused by burning of vertical rods, lower cage or fins
4c. Friction between ejected stage and vertical rods

5. Problems with build quality

Any comments? Suggestions?

Click to expand...

I solved 2-D trajectories to evaluate the three alternatives: a) Single massive failure, b) Loss of power, c) Side-thrust.
All I could be sure of what that neither loss of power nor side-thrust could explain the observed trajectory on its own. A 25% loss of power with 25 degrees of side thrust was the best fit, but even that gave the wrong shape for the descent trajectory - so it looks as if a single massive failure played a part.

My next step will be to discard the use of sticky tape as a tool for multistaging, to see if that is the problem.

My guess is that I'll end up having to X-ray motors before assembly in order to eliminate faulty manufacture, and that I'll have to get aluminium couplers machined to near-micron accuracy to eliminate side-deflections on stage separation. I may also have to eliminate the rack rocket design in order to reduce motor exhaust drag on rods and fins, but the expense of that would be a heavier launch and more air drag - and both are crucial.

Have you read
https://arapress.com/vts.php
I think it has the answers.
Basically for the rocket to be stable the CG has to be in front of the CP. But gravity works on CG, so the instant the rocket is not perfectly vertical, gravity pulls the CG and leans the rocket over. The fins stabilize it in the new non-vertical, then gravity pulls it again. etc.. etc..
The result is with a long enough burn time it will come in ballistic under power EVERY time.
They also have a book on staging.
https://arapress.com/shpr.php

Airobert said:

Have you read
https://arapress.com/vts.php
I think it has the answers.
Basically for the rocket to be stable the CG has to be in front of the CP. But gravity works on CG, so the instant the rocket is not perfectly vertical, gravity pulls the CG and leans the rocket over. The fins stabilize it in the new non-vertical, then gravity pulls it again. etc.. etc..
The result is with a long enough burn time it will come in ballistic under power EVERY time.
They also have a book on staging.
https://arapress.com/shpr.php

Click to expand...

I haven't seen those yet. Thanks, I will look at those in detail.

In case you're wondering, the delay on making my third attempt at a 10-stage rocket using 9*C6 for upper stage on an E12 first stage is because I used high temperature paint, and during curing of the high temperature paint in the oven the nose-cone melted. So, warning, never heat a 3-D printed plastic part to 140 degrees C for more than a few seconds. As a result I've ordered a new nosecone. I also needed to cut the rods shorter so the next attempt will be a 9-stage.

For this 9-stage I'm trying two different multistaging techniques used together - the rack rocket and the sliding fit. Rack rockets have worked up to 6 stages. The addition of a sliding fit inside the rack is to test if the multistaging arch-over problem is due to Mr Vernon Estes' recommendation of using a turn of sellotape to attach like stages together, 30 mm of sliding fit replaces the sellotape.

i.e., eliminating any potential failure due to Number 2 above:
> 2. Failure of multistaging method of using a single turn of sticky tape

> The result is with a long enough burn time it will come in ballistic under power EVERY time.

I've been playing around with OpenRocket and now realise how important it is to angle the rocket at the correct angle off vertical as a function of wind speed. A difference of even half a degree off optimal for given wind speed has a catastrophic effect on maximum altitude. So have made a new launch platform with a heavier base and thicker longer launch rod, bought an anemometer for measuring wind speed, and disinterred a plumb bob for angle measurement. I know enough about wind to roughly compensate for the increase of wind speed with height, though compensating for change in wind direction with height requires a test flight in advance of the main flight.

Successful launch of multistage 9-stage black powder hobby rocket. First stage E12, Other stages C6. Total flying distance exceeds 3.4 km. The design is a combination of rack rocket and conventional multistaging. Listen to narration on video for more details. The final launch lug configuration is not shown.

[video=youtube;ougqfMptDj0]https://www.youtube.com/watch?v=ougqfMptDj0[/video]

Really interesting (and amazing, it's awesome you were able to make it work). Does the rack rocket not have the thrust loss you see in rockets where the engine is recessed inside the BT? Also, so you know why it started to head sideways and then down? Is it just the action of staging that causes flight deviations?

You might want to check out Random Flying Object's L3 build. He is setting it up to be able to take input from canards, which would allow you to keep the rocket ascending without veering off course. His rocket was set up to be 2 stage flying M motors, but you could use smaller composites for the same general design.