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[John Stedman]

I'm trying to find out if Jetex Rocket Motors are still available in any form. These little powerpacks were quite popular in the 1960's for propelling small, light model hydroplanes across ponds at very high speed for a couple of seconds. They used solid pellets of rocket fuel which is probably banned by the EU these days. Perhaps somebody knows if there is an equivalent available?

[Stan]

Hi John I think these motors did come back for a short while.But I have feeling they are just history now but who knows you may be lucky.


Stan

[Stan]

Hi john just checked the web they may be still available.Just type in jetex motors hope this helps.


Stan.

[g6swj]

Any good - Estes  Engine Pack
https://www.amazon.com/Estes-A8-3-Engine-Pack-3-Each/dp/B0006ZVZ94/ref=sr_1_fkmr1_4?s=toys-and-games&ie=UTF8&qid=1485029685&sr=1-4-fkmr1&keywords=estes+pellets

[grendel]

there is quite a following in the model rocketry scene, I believe there are many more types of rocket motors available nowadays.

[John Stedman]

Hmmm, interesting! eBay have an information page about Jetex engine propellants which is hilarious. Apparently the fuel was concocted in an ICI factory 'Somewhere In Scotland' (so look for a big crater). The main constituent of this potentially lethal stuff was Guanidine Nitrate (obviously), but there were other 'Secret Ingredients'. The similarity of the chemical name to the word 'Guano' convinced some people that the explosive concoction was made from bat droppings, but this was just an Urban Myth, apparently. The main problem was that the fuel deteriorated rapidly, even if stored in your own temperature-controlled Nuclear Bunker. It's said to be out of production, sadly. Maybe I could try to create my own: I mean, it's not rocket science, is it?

[C-3PO]

Estes Rocket Motors - not Jetex...

Here is a  link

https://www.elitemodelsonline.co.uk/Rockets/Rocket-Motors

[BFSMP]

ahh.. what's wrong with a bit of sodium nitrate and sugar mixed 2;1 works wonders as a rocket fuel, 


Jim.

[John Stedman]

The Jetex-powered model boats I saw on Hampstead Pond back in the 60's used the standard single solid fuel pellets, and reached maybe 20 knots for two seconds. But I once saw a version that held three pellets and was even faster. So Ive been thinking, could that idea be taken to extremes?


Everybody's heard the Urban Myth about the USAF guy who thought it would be a good idea to strap a Jet Assisted Take-Off rocket to the roof of his car. It didn't end well for him: a cliff face was involved. But anybody who saw the Space Shuttle take off will have been awed by the sheer brute power of its twin Solid Rocket Boosters. Using a fuel called APCP, the SRBs were the main force that accelerated the Shuttle to to an altitude of 30 miles and a speed of over 3,000mph. Now that's impressive.


So could such forces be controlled and managed to push a model boat up to outrageous speeds? How would you control it? Where would you do it? Is anybody insane enough to try? Conventional models have reached over 120mph, but I'm thinking much faster than that. Faster than a manned watercraft has ever achieved. Faster than sound, even. Impossible? Probably. But...


First, control. Conventional RC strategies just aren't going to cut it. We'd need some form of autopilot, probably using GPS technology to keep the boat in a straight line. These systems already exist, and can be used to precisely 'autoland' airliners without the pilot doing a thing. But at very high speed it's not enough to have control only in the yaw axis. Stability in roll and pitch axes is also going to be critical. Conventional 'passive' ideas of simply shaping the hull to achieve this won't be sufficient. We'd need 'active control' in the form of moveable aerodynamic surfaces, again a technology that the aerospace industry has mastered.


Keeping all this managed would be too limited by human reaction times, system latency and abilities to pre-empt potential instability issues. It would require a computer controlled system that could 'learn' by developing Artificial Intelligence on runs at increasingly higher speeds. Again, AI software is available and is already used by many industries. Driverless cars are beginning to prowl our roads. And keeping a model boat stable in a straight line at speed has got to be easier than finding a parking space in Chelsea.


So where would you do it? I suggest Cambridgeshire. There's a combination of river and canal called 'The Bedford Level' that stretches for 20 miles in a virtually straight line without any locks or other obstructions. It has minimal current flow and is often as flat as a millpond. It's so calm and featureless that it was once chosen for the classic experiment that proved the earth was more-or-less spherical. At about 30' wide it's obviously too narrow for a manned speedboat, but for a model, well...


And the classic question is, of course, "How fast will it go, Mister?". Difficult to speculate, but my response is "Well, how fast do you want it to go?"

[Arrow5]

Forget Jetex, a toy.  Sugar and Nitrate recipe for a smoke bomb, copious smoke.  Back to Youtube, search for "fastest model boat in the world. The final cut.wmv"   it is on carltonjacobs2005`s channel. Loch Ness is wider than the Bedford Level, mile wide  20 miles long. Used by John Cobb on final run.

[Firefly]

John,


Regrettably Jetex motors are no longer available.  A UK company produced a similar motor, powered by pellets, some years ago under Jet-X label.  That company went out of business following the passing of its proprietor.  A small company, based in the Czech Republic, also produced a similar motor to the Jetex sold under the Rapier brand name.  However, Rapier ceased production when EU and Czech legislation, enacted in 2010, recategorised Rapier motor propellant as fireworks rather than model engines. This required the manufacturer to set up secure production facilities which were unaffordable and so led to the demise of the Rapier company. As far as I am aware, there is no similar propulsion system currently available for model use.


I have read, on some model aircraft forums, of attempts to use Estes rocket motors as replacements for Jetex/Rapier. However, these seemed mostly unsuccessful as the models either couldn't cope with the stresses imposed by the power of the motors causing them to break up in flight or the model caught fire as consequence of the motor efflux.


Not very helpful but, hopefully, tells something of the story as to why Jetex motors are no longer available.


Mick

[John Stedman]

At the very high speeds I'm envisaging here, a major issue would be the dynamic interaction between the natural frequencies of oscillation of the vessel (in all axes) and how these may resonate with any undulations in the water surface. Resonance is bad news for anything that moves fast in a fluid like water or air, because each cycle tends to build on the previous one until grip is overwhelmed by momentum, control is lost and 'ballistic' behaviour takes over. The pre-collision dynamic behaviour of the Mecedes Benz S280 in which Henri Paul, Emad Fayed and Diana Spencer died showed this well.  A large body of water is more likely to cause complications in this respect. A long narrow 'millpond' would present itself to an approaching hydroplane or hydrofoil as an almost 'solid fluid', increasingly so as the speed rose, and if the boat were designed as an 'interactive three point hydroplane' (which seems the most likely configuration) then it would be more likely to remain within its safety margins. But of course, as always, extensive practical testing would be necessary to prove the many concepts involved. Original thinking would be the order of the day.


Regarding propellant, APCP appears to be the baseline choice. There are more modern compounds which have a better thrust to weight/bulk ratio, but most of these are restricted to military use. Solid rocket fuel is 'all or nothing', producing around 100% power output from the moment of ignition until the fuel is expended. There is no 'throttle control'. So the burn time would have to be designed to give full thrust to the end of the official speed measurement zone. As the fuel burns, the all-up weight of the boat would reduce considerably, which would require compensating actions from the stability systems, and quite possibly a 'morphing' of the surfaces in contact with the water. Some back-of-the-envelope calculations, based on very approximate weights, likely air resistance, water drag and fuel efficiency, suggest that the model could be moving several times faster than any model boat has done before. I don't know if it would be possible to test these theories with a smaller craft and then scale them up, but I've got someone looking into it.

[John Stedman]

John,

Regrettably Jetex motors are no longer available.  A UK company produced a similar motor, powered by pellets, some years ago under Jet-X label.  That company went out of business following the passing of its proprietor.  A small company, based in the Czech Republic, also produced a similar motor to the Jetex sold under the Rapier brand name.  However, Rapier ceased production when EU and Czech legislation, enacted in 2010, recategorised Rapier motor propellant as fireworks rather than model engines. This required the manufacturer to set up secure production facilities which were unaffordable and so led to the demise of the Rapier company. As far as I am aware, there is no similar propulsion system currently available for model use.

I have read, on some model aircraft forums, of attempts to use Estes rocket motors as replacements for Jetex/Rapier. However, these seemed mostly unsuccessful as the models either couldn't cope with the stresses imposed by the power of the motors causing them to break up in flight or the model caught fire as consequence of the motor efflux.

Not very helpful but, hopefully, tells something of the story as to why Jetex motors are no longer available.

Mick

Fascinating Mick, thank you! I always suspected that the EU were to blame for stopping the sale of working rocket engines to young people. I mean, where's the danger in that?

[Arrow5]

Any thoughts on the Carlton Jacobs boat on Youtube ?

[Plastic - RIP]

 Solid rocket fuel is 'all or nothing', producing around 100% power output from the moment of ignition until the fuel is expended. There is no 'throttle control'.

Not quite - normally, the solid fuel is formed around a mandrel so the inner core is shaped like a star to give much more surface area for the burn. More surface area = more power. The shape of the core can be designed to give a gentle push at the beginning to reduce acceleration forces and then a smooth burn to give constant power. With stacked cores with different shaped internal shapes, all sorts of power delivery is possible as the burn progresses through the fuel. (this can be useful with things like the shuttle to reduce acceleration at low altitudes through dense air to reduce stress on the airframe)

[John Stedman]

Any thoughts on the Carlton Jacobs boat on Youtube ?

The clip is worth a look, but it's hard to see what happened to cause the crash. Most likely it was a stability issue, either triggered by unforseen aerodynamic or hydrodynamic forces, or both, since the design and construction of the boat appear to be rather unsophisticated. The terminal velocity of the craft is reported as 204mph, perhaps even 250mph. However, World Records are not measured in terms of terminal velocity. World Records require certain rules to be complied with, which normally include the necessity of completing two full officially measured runs in opposite directions within a time limit, provision of appropriate timing apparatus which has been independently certified for accuracy, the averaging of speeds achieved over the measured distances, evidence that the craft was in some manner 'controlled' and not simply 'ballistic', and, most importantly, that all of these matters were observed, checked and confirmed by independent observers appointed by the record-keeping authority. The Guinness Book of Records compilers have similar criteria, and to satisfy them is quite a complex and expensive matter. But it would seem to be a pity to go to all the the effort of establishing a 'World Record' and not then have the satisfaction of seeing it given Approved Status.

[Arrow5]

The crash was only incidental , I thought the clip might demonstrate a very fast model boat powered by a rocket that was in another league from Jetex.  They only claimed "the fastest model boat in the world" not a world record.  Speed records for model boats would be ratified by model boat organisations not Guinness.    The design of that model was a more or less standard outrigger similar to K7 which brings us back to the start of the thread. Plenty of carbon-fibre seen in the  wreckage . He says rudder failure as cause of crash, just a guess IMHO.  I  would have thought that  12ft model of K7 with a conventional drive and a powerful i.c. engine would go fast enough and leave an almost smokeless rooster tail similar to a turbine to be convincing on film. Simple to run and maintain etc etc.   Any thoughts on the Aussie father and son team Warby ? Conventional monohull.

[tony23]

I have got 20 Jetex motors from the 60's and early 70's some still in boxes I used to build balsa gliders and fit them onto them even lost a couple in thermals    fuel pellets were the hardest things to get I have still got some in old tins they came in. They did release them in the early 90's so there should be stock around but these things are becoming harder to find every day.

[John W E]

http://www.ebay.co.uk/itm/CARD-with-10-VINTAGE-JETEX-600-FUEL-PELLETS-WICKS-MODEL-JET-AIRPLANE-CAR-MOTOR-/142250683822?hash=item211ecd2dae:g:0EcAAOSw2xRYgDnL

hi some on eBay
john

[malcolmfrary]

A friend of mine back in school days had a Jetex powered speedboat.  As said earlier, about 2 seconds of go, but that followed by the wait for the little yellow thing to drift in.
Many years later, a different friend got an Estes outfit.  Bigger and probably better, there was a selection of fuel pellet sizes, from something about AA battery size to D cell size for different run time and thrust.  The electric ignition was "interesting".

As to control, with solid fuel, there just isn't any apart from that built in by the maker.  Once its lit, it burns.  Doesn't matter whether its a tiny toy like a Jetex motor or a space shuttle, it burns as it might and produces thrust until there is nothing left to burn.

[Colin Bishop]

'it burns as it might and produces thrust until there is nothing left to burn.'

Often after incinerating the model to which it is attached....

Colin

[Plastic - RIP]

There's an interesting page here: http://www.davidsissonmodels.co.uk/Ian%20Wingrove.htm

All about Gerry Anderson's models - they used Jetex for all of their rocket effects.

[Jerry C]

As a young lad I built a Supermarine Swift, (Keikraft?), with a jetex motor insulated with asbestos paper and fitted with lightweight augmentor tube. Hand launched on first hint of thrust it climbed very rapidly until motor went out then glided down gently in a lazy left spiral. Had many flights. All much longer than even the Keilcraft Ace rubber powered model which we had to wind up with a hand drill brace.
Previously, to learn and understand the Jetex motor we ran a balsa sheet rocket suspended on 100 yards of fishing line with two paper clips. My best friend was at the nasty end of the line. Motor was always still burning when it got to him and motor jumped out of the clip setting fire to the grass near by. Motors were a sod to clean after use.  Thoroughly enjoyed learning from them. 
Jerry.

[Arrow5]

There is a couple of videos on Youtube of fairly recent Jetex Days at Old Warden.   I couldn't afford the Jetex boat so made a balsa  enlarged Tomboy float, worked fine. Fuel pellets weren't cheap for a young teenager then.

[BFSMP]

I am reading this thread with great glee and thinking back to my childhood when I and a couple of friends used to knock up, on a regular basis, boats and planes and have competitions with them as to how far they would "fly" either on, in, or above water level.
Corners were cut and often the motor would part company with the model and shoot off like a bullet, with a return to the local model shop for a replacement jet, but boy was it fun.
We never thought of the dangers to life, limb or bystander and so it would seem neither did the manufacturers of Jetex.
It would also seem neither did any others on here who owned these demonic contraptions and played with them, but how they were built to be played with, fun and no care to self at all was just exciting.
But it's no wonder that they were finally discontinued.
Elf and safety would these days have apoplexy if they saw 10/11 year old kids playing on a public lake with a potential bomb.
I wish those days of care free fun could return, as kids are sure missing out on it.


Jim.