stupid is as stupid does

http://www.abc.net.au/news/2013-10-18/an-asbestos-consumption-on-the-rise-in-asia/5032626?section=business

Governments in Asia have been accused of ignoring the dangers of asbestos, and allowing the ongoing use of the hazardous building material.

Sugio Furuya, coordinator of the Asian Ban Asbestos Network, or A-BAN, has told Radio Australia’s Asia Pacific consumption among many Asian countries is still on the rise, although countries like Japan, South Korea and Australia have banned the use of asbestos.

“Asbestos consumption in Asia is accounting for 70 per cent of global asbestos consumption,” Mr Furuya said.

“More than 90 per cent of asbestos is used for construction materials and the people touching asbestos are not informed about hazard.”

Mr Furuya says the material is being used in the construction of houses due to its low cost.

“Asbestos construction materials is only for factory or other industrial use,” he said.

“But now, asbestos cement is very easily used for residential homes in rural areas in many Asian countries.”

He says countries like India are intentionally ignoring the dangers of asbestos.

“There’s almost no regulation against asbestos in such countries and asbestos victims are still invisible in many developing countries,” Mr Furuya said.

“ takes no action to prevent people from asbestos exposure.”

He says it is important to educate people in the region about the dangers of the material.

“All people have a right to work and live in safe and healthy way,” he said.

“Safer alternatives are available everywhere, so it is not to use asbestos anymore.”

Mr Furuya says Australia can help Asian countries stop using asbestos.

“Australia has much experience and expertise to deal with asbestos,” he said.

“Australia can contribute… to avoid an asbestos epidemic in the future.”

I’m beginning to wonder if hobby rocket parts ought to be made of chrysotile-based materials, instead of cardboard and plastics. They would certainly be less-likely to catch fire, and therefore safer.

The Twin Towers were the first major high-rise structures to be built without asbestos fire-resisting materials – and see what happened there.

There are other fibrous insulating materials. Alumina fibre for example. I don’t think that they pose the same health risk as asbestos. They are probably a lot more expensive though.

mollwollfumble said:

The Twin Towers were the first major high-rise structures to be built without asbestos fire-resisting materials – and see what happened there.

They were loaded with asbestos, it is one of a number of reasons the towers were considered to be white elephants

http://m.youtube.com/watch?v=O1GCeuSr3Mk

Part 1 of 3, best 911 video ever made, it talks about the asbestos.
.

mollwollfumble said:

I’m beginning to wonder if hobby rocket parts ought to be made of chrysotile-based materials, instead of cardboard and plastics. They would certainly be less-likely to catch fire, and therefore safer.

unnecessary

any working rocket design even if made from plastic and cardboard is unlikely to catch on fire

chances are most accidental fires are started by cigarettes, camping equipment, tools not model rocketry.

anyway, asbestos products are banned in australia

> any working rocket design even if made from plastic and cardboard is unlikely to catch on fire

You haven’t seen my designs. :-(

It’s interesting that Estes rocket engines are simply encased in cardboard, right next to burning gunpowder at a typical temperature of 1200 Celsius. It’s not a combination that materials science would suggest, but it seems to work. I want to find out why it works by dissecting an engine to see if there’s anything special about the cardboard.

mollwollfumble said:

> any working rocket design even if made from plastic and cardboard is unlikely to catch on fire

You haven’t seen my designs. :-(

It’s interesting that Estes rocket engines are simply encased in cardboard, right next to burning gunpowder at a typical temperature of 1200 Celsius. It’s not a combination that materials science would suggest, but it seems to work. I want to find out why it works by dissecting an engine to see if there’s anything special about the cardboard.

the cardboard chars and any further stops

from what I’ve seen there is no further burning even a few seconds after flame out

mollwollfumble said:

It’s interesting that Estes rocket engines are simply encased in cardboard, right next to burning gunpowder at a typical temperature of 1200 Celsius. It’s not a combination that materials science would suggest, but it seems to work. I want to find out why it works by dissecting an engine to see if there’s anything special about the cardboard.

Have a look at Rocket Propulsion and Spaceflight Dynamics by Cornelisse, Schoyer, and Wakker (Pitman Publishing, 1979) and Handbook of Astronautical Engineering by Koelle (McGraw-Hill, 1961). Both have good discussions of how the fuel in solid-fuel engines insulates the case from the flame front. In the case of Estes model engines, the cardboard is not in contact with the flame for mare than a few hundred milliseconds.

Wocky said:

mollwollfumble said:

It’s interesting that Estes rocket engines are simply encased in cardboard, right next to burning gunpowder at a typical temperature of 1200 Celsius. It’s not a combination that materials science would suggest, but it seems to work. I want to find out why it works by dissecting an engine to see if there’s anything special about the cardboard.

Have a look at Rocket Propulsion and Spaceflight Dynamics by Cornelisse, Schoyer, and Wakker (Pitman Publishing, 1979) and Handbook of Astronautical Engineering by Koelle (McGraw-Hill, 1961). Both have good discussions of how the fuel in solid-fuel engines insulates the case from the flame front. In the case of Estes model engines, the cardboard is not in contact with the flame for mare than a few hundred milliseconds.

is that because it chars?

some motors will burn for 3 seconds or more meaning that the inner tube closest to the venturi will be exposed to hot gases for more than a few milliseconds. if the cardboard chars then the cardboard is no longer exposed.

cotton works in the same way in safety clothing, after the first milliseconds etc the cotton stops burning as the char forms a protective barrier

Any idea what the Estes “2274 RECOVERY WADDING Flame resistant wadding protects recovery system” is made of? Have been unable to buy flame-retardant spray from local hardware, craft and camping shops; they don’t stock it.

>> any working rocket design even if made from plastic and cardboard is unlikely to catch on fire
> You haven’t seen my designs. :-(

To give you a clue, here is a graph I made up in Excel of total motor cost vs altitude achievable. I have assumed intermediate assembly ability (am not assuming that the builder is an expert).

Forget 1- and 2-stage rockets. The highest rocket altitude on this graph, 6 km, would be achieved with a 27-stage rocket. I have no reason to suppose that the almost-linear correlation of altitude vs cost couldn’t continue up to the edge of the Earth’s atmosphere, in which case it would be possible to send a hobby rocket into space for about the price of the cheapest car.

the hobby rocket have recommended take off weights

don’t bother with the smaller motors – buy the biggest you can buy for your state – or just make them if you live in NSW – NSW has effectively banned rocket motors due the puny motors legally available so you’d be better off making something far more powerful than muck around buying them.

you might be able to stage them but what real height you’d get to is another matter

I wouldn’t bother with the parachutes if I were you

the hobby rocket have recommended take off weights

don’t bother with the smaller motors – buy the biggest you can buy for your state – or just make them if you live in NSW – NSW has effectively banned rocket motors due the puny motors legally available so you’d be better off making something far more powerful than muck around buying them.

you might be able to stage them but what real height you’d get to is another matter

I wouldn’t bother with the parachutes if I were you

the other complication is the shape of the rocket, having a chunky cluster will increase cross sectional area, ideally you have the slimmest, lightest frame for a model rocket due to the weak motors

you don’t want the rocket to approach supersonic in the thickest parts of the atmosphere or you’ll just spend more power pushing air

mollwollfumble said:

Any idea what the Estes “2274 RECOVERY WADDING Flame resistant wadding protects recovery system” is made of? Have been unable to buy flame-retardant spray from local hardware, craft and camping shops; they don’t stock it.

>> any working rocket design even if made from plastic and cardboard is unlikely to catch on fire
> You haven’t seen my designs. :-(

To give you a clue, here is a graph I made up in Excel of total motor cost vs altitude achievable. I have assumed intermediate assembly ability (am not assuming that the builder is an expert).
http://i120.photobucket.com/albums/o162/DavidPaterson/SSSF/Altitudevsprice_zpse2c387ad.jpg
Forget 1- and 2-stage rockets. The highest rocket altitude on this graph, 6 km, would be achieved with a 27-stage rocket. I have no reason to suppose that the almost-linear correlation of altitude vs cost couldn’t continue up to the edge of the Earth’s atmosphere, in which case it would be possible to send a hobby rocket into space for about the price of the cheapest car.

Either I’m missing something, or you haven’t fully described what that graph means. Just as a simple example, you suggest that a 27-stage rocket could get to 6km altitude; some simple calculations suggest that a 27-stage rocket wouldn’t even get off the ground. Page 76 of this pdf http://www.estesrockets.com/media//catalogs/Estes_2013_Catalog2.pdf gives the mass of the highest-powered E-sized Estes rocket engine at 61.2g, and its maximum lifting capacity at 482g; 27 of these would have mass 1652.4g.

the other unspoken problem with hobby rocket motors is that they are known to be underpowered compared to their theoretical power

another issue is the temperature of the motor itself before ignition – it has bearing on how well it will burn

wind will affect the flight path and will turn the rocket into the wind and create more drag

in most cases once you’ve accounted for the weight of the motors and the frame of the rocket you are effectively limited to about 3 in my estimation as the max take off weight is based on it achieving a flying speed before leaving the guide rail

001100010010011110100001101101110011

001100010010011110100001101101110011

001100010010011110100001101101110011

I have yet to send up even a single rocket, but have assembled a kit and ordered rocket parts for a home-made one, so this is all theoretical and any advice you can give will be a huge help.

> the hobby rocket have recommended take off weights

Ah, yes. I now I ignore this. The main reason for ignoring recommended take-off weight is the length of the take-off rod. The standard launch rod provided with the motors is 0.8 metres. For a high altitude launch a rod length about 10 metres (or more in strong winds) is needed. Double the length of the take-off rod and you can enormously increase the safe maximum weight a motor can carry. The key is not “take off weight” but minimum velocity, if the velocity drops too low at any point in the trajectory then wind will push it off course. I’m trying for a minimum free velocity of 50 to 55 m/s, for the highest altitude rockets in the chart I’m predicting a minimum of 46 to 48 m/s.

> don’t bother with the smaller motors – buy the biggest you can buy for your state

What is the biggest in your state? A Queensland rocket shop sells up to class N. I once met someone who launched a class O from Western Australia.

Victoria (where I live) has a certification scheme with three levels. Uncertified up to G, level one certification up to I, level 2 certification up to L, level 3 certification for M or larger. So I’m limited to G for the time being. There’s also a height limitation for uncertified but I don’t remember what it is.

Big single stage is fantastic for heavy weight to low altitude, but the velocity rapidly gets so large that air drag (roughly proportional to velocity squared) becomes enormous, which greatly limits height per unit fuel. I find it extremely annoying that “big” rocket motors all have an extremely poor ratio of propellant mass to total motor mass. Small rocket motors have a poor ratio, but much better than the big ones. eg. Commercial rocket – propellant is 85% of motor mass, small black-powder C6.0 motor propellant is 57% of motor mass, reloadable motors propellant is about 33% of motor mass.

Have you ever heard of a single-use “composite” motor, of any diameter, that is available somewhere in Australia and can be used as first stage booster? Please.

What’s available for “big” in multistage?

Which is the smallest-diameter reloadable motor that can be used as a first stage booster?

I don’t happen to own a farm. I know where I can’t fly rockets near Melbourne because of “controlled airspace” limitations and safety restrictions (clouds/fire risk/required clear area), but don’t know how to find somewhere I can fly them. Any advice?

I’m thinking of flying one in my garage. OK?

> or just make them if you live in NSW – NSW has effectively banned rocket motors due the puny motors legally available so you’d be better off making something far more powerful than muck around buying them.

Make how?

——————-

I found a couple of things from a pure theoretical analysis.

One is “fuel usage (and hence cost) per metre of altitude is minimised if air drag is exactly equal to rocket weight”.

Two. The weight is proportional to the base area, the thrust for prespecified fuel type is roughly proportional to the base area, the drag is proportional to the base area, so my second realisation was “cross sectional area hardly matters”, except for cost and payload weight of course, so for small cost you want a thin rocket.

A third searching the internet was “workmanship matters a very large amount”.

The above led me to my key number “135 m/s”. Accelerate a rocket from launch as rapidly as possible to 135 m/s and thereafter hold it at that velocity as closely as possible, that will minimise fuel usage per unit height. Following on from that, it becomes a trivial exercise to estimate roughly how long the rocket fuel has to burn to reach a given height – it’s a long time in hobby rocket terms, and that means that the total height of the fuel in the rocket has to be large. Furthermore, the faster the fuel burns the taller the rocket has to be.

> you might be able to stage them but what real height you’d get to is another matter

Each extra stage would add to the probability of failure, so a near foolproof staging system is needed. :-(

> I wouldn’t bother with the parachutes if I were you

Serious question, why not? I can think of two reasons why not – one is that it increases the length of the payload and therefore reduces rocket aerodynamic stability, the second is that a parachute going off at high altitude is a sure way to guarantee that it gets blown so far that I’ll never see it again. Is that why you said it?

Talking about getting lost, do you know of anyone attaching one of those VHF trackers to a rocket? They’re normally attached to animals, including small birds and microbats. If I was to get one for you would you want it?

> the other complication is the shape of the rocket, having a chunky cluster will increase cross sectional area, ideally you have the slimmest, lightest frame for a model rocket due to the weak motors

That’s why a “chunky cluster” is best used only for the initial launch boost, at speeds so low that aerodynamic drag hardly matters.

> you don’t want the rocket to approach supersonic in the thickest parts of the atmosphere or you’ll just spend more power pushing air

The theory I looked at strongly suggested that for minimum fuel cost per unit altitude I want to stay under half the speed of sound in the thickest parts of the atmosphere.

By the way, my looking at “asbestos” substitutes was because it may be possible to use a finless rocket (which would help a large amount in multistage, which usually require very large fins) or a rocket with very small fins if the rocket motor is jammed as far forward in the rocket body as possible, and the business end of the nozzle is within the rocket tube. One of two problems is that the rocket tube itself would then get very very hot.

mollwollfumble said:

I have yet to send up even a single rocket, but have assembled a kit and ordered rocket parts for a home-made one, so this is all theoretical and any advice you can give will be a huge help.

I’ve launched many, many rockets, all my own design. Most used Estes engines, but some used home-made engines, including several liquid-fuel. I’ve had some spectacular failures, too.

Why asbestos? What is wrong with other heat shields?

> launch rod … 10 metres.

My mistake, I meant to say 10 feet, but perhaps 10 metres really is necessary for overloaded rockets. The Top Gear Reliant Robin Space Shuttle had a launch rail of close to 10 metres.

wookiemeister said:

I’ve launched many, many rockets, all my own design. Most used Estes engines, but some used home-made engines, including several liquid-fuel. I’ve had some spectacular failures, too.

I’d love to hear about the liquid-fuelled ones. H2O2, LOX, N2O or other?
What principles did you use for the Estes-engine rocket designs?

roughbarked said:

Why asbestos? What is wrong with other heat shields?

I’ll take the answer to this slowly. For “asbestos” in the following read “chrysotile”, which is by far the least dangerous form of asbestos and accounts for 95% of asbestos found in US buildings.

Any non-halogenated carbon-based material (such as plastic) is intrinsically flammable.
Any halogenated carbon-based material has a lower melting point than chrysotile, and those with no hydrogen (eg. Teflon) are ozone-unfriendly.
Any intumescent heat shield expands in volume when heated, so cannot be used where dimensional stability is needed.
Graphite has a high thermal conductivity.
High-melting point metals such as tungsten have even higher thermal conductivity.
Glasses, being formed from melt, have lower melting temperatures than chrysotile (eg. Pyrex glass has half the melting point of chrysotile).
Clay-based ceramics tend to be brittle.
Concrete-based ceramics have low tensile strength unless reinforced by something (such as chrysotile!)

That leaves heat shields such as borax and silica- and alumina-like ceramics.
Borax melts at a low temperature.
Ceramics tend to be brittle.

Silica- and alumina-like ceramics are expensive to spin into fine fibers, and when they are spun into fine fibers they are just as dangerous as chrysotile because the danger from chrysotile is purely due to physical shape and size, not due to chemistry. The small fiber diameter of chrysotile helps to overcome intrinsic brittleness by being geometrically like a small-diameter coiled spring.

I’m not saying that chrysotile is always the best heat shield (the space shuttle uses 8 different types of heat shield) but it is cheap, effective, and at least as safe as any other fibrous heat shield with fibers of the same diameter.

I find it so annoying that chrysotile is lumped in the public mind with the much more dangerous amosite and deadly crocidolite under the umbrella heading of “asbestos”. They’re not even chemically related, chrysotile is a serpentine whereas amosite and crocidolite are amphiboles. That’s an enormous chemical difference.

Thanks mollwoll.

I haven’t launched that many, I think you are confusing me with sticky

Other considerations , what kind of flex will be in long guide rod? What will happen if it flexes as the rocket moves up the rod?

Clustering the rocket brings new challenges. If one motor doesn’t fire or starts / finishes at a different time it will throw the rocket out. To counter this you’ll need fins.

Amateurs will normally use one high powered motor that is in perfect alignment, anything else brings unknowns unless some serious development/ testing has been carried out.

The fins of a rocket have to be perfect or it will introduce roll which leads to somersaults from my experience.

The hobby rockets can’t be relied upon to go up any great height unless you designed a very thin lightweight body. Theoretical thrust is never anywhere close actual thrust.

The smaller the CSA the better, body length shouldn’t exceed 15 diameters if possible

The longer the rocket the more drag

A nose cone decides what kind of drag the rocket will have

My own thoughts are moving away from solids

You could manufacture NO2 , cool it and make N2O4

This has more oxygen than nitrous, is easily held as a liquid, is a powerful and easily made oxidiser and cheap to make.

An N2O4 hybrid with toffee/ some other fuel is controllable and cheap to make

Mollwoll are you still able to post on the other site about this sort of thing

I need to ask you some questions

The other site being X-prize technical?

I still have the address so suppose I can post.
BTW, my csiro email has shut down so avoid it.

Yes, I can still log in to the restricted area. BTW, had my first two failed launches yesterday.

see you there