Model Forum / General / Models / December 2007

Wanted any PRACTICAL solutions to liquid fuel reactor(rocket) motors
MAJOR requirement fairly cheap and cheerfull even at the risk of muc
lowwer power outputs

The project so far

attach a suitable 4  to 6kg reactor motor to a modified F5D 1 metr
wing span RC model plane for fun to get small fast runs reaching speed
of 250MPH plus for a few seconds

Requirements motor run times of some 3  to 5 seconds idealy with abilt
to PRECISION  light up in flight and PRECISION  relight several time
making say 4 motor runs of 5 seconds each  and glide around in betwee
motor burns and electric motor or bungee launch take off to get to ful
height to commence first motor runs

reasearch to date elimates most off the shelf rocketry solutiuons fo
various reasons

the pulse jet solutions is not what i wish to do in this time as th
motors are very large for the KG push and cant be easly relight in mi
air

Steam reactor power solutions look to be too heavy in this time
but if somebody can prove other wise I am all ears as it looks supe
cheap
great solution for model cars but too heavy for model planes is m
guess

CO2 bottle solutions look to be way  too heavy and real low power s
not pratical

Most solid fuels have in-exact firing times eg non PRECISION  and fo
multi fire ups would reguire several rocket motors and AP fue
reloadables are crazy money so not pratical
gun powder off the shelf solutions are tiny tiny power like a or
motors and this project is closer to f or g or h motors  and gunpowde
large motors dont work as the large grain or pellets break up to easy
making motor runs fizzle and pop and not work

Liquid solutions preferably would be mono props but those fuels hav
issues

The best solution Hydrogen peroxide at 98% down to barely usable 80
types are impossible to source in Europe generaly and as I live an
work all around europe I prefer to use easy to obtain fuels and the
are extremly cautic (similar to acid affects ) so not practical fo
cost and protective clothing issues

Nitromethane fairly easy obtainable in larger model plane shops or LH
but sooooooo wicked expensive at ~50 euro ~£30 for 5 litres and eac
flight of 20 seconds motor run would probably be 1/2 litre 500cc makin
it 5 euros £3 euro a fight or ~12 euros £8 a minute engine run time  an
as nitro methane fuel is nearly all oxegen and nitrogen molicule i
requires 9 times the same fuel as methanol solutions  and worst it
nearly impossible to ignite without extreme    pressures and you stil
realy need some outside oxidizer fuel component not much but some t
get clean burn there buy making reactor motor very complex and mos
likely not to be a practical solution

Other fuels like gasoline (petrol)and deseil kerozene all have n
oxegen in the fuel and require to carry some form of oxydent  such a
LOX (liquid oxegen) with the complexity asnd weight issues of LOX  bu
probably not practical as supply of LOX are tricky and probabl
expensive

other solutions like mix Nitric acid red humourous with kerozene
agggghh realy not pratical

Hydrazines also way to dificult to get and extremly toxic realy no
pratical

Alchols fuels like ETHANOL METHANOL have some 50% of the molicule a
oxegen so thereby needing half the oxegen  to supply the fuel(but yo
need double the fuel compared to petrols fuels) but saving some weigh
from less LOX but probably not practical as supply of LOX are trick
and probably expensive

The better solutions for me would be to find a simplex way to oxegenat
the fuel without LOX if a solution exists

one theory I have  is to  disolve KNO3 saltpeter into methanol

salt peter is tricky to get but not impossible

Methanol is easy and fairly cheap at  ~15 euro ~£10 for 5 litres to ge
from LHS

I cant find out from reasearch or inquirys to umpteen forums wil
mixxing these two components make the methanol fuel shock sensitive o
even explosively unstable imeadialy or over time whatever
What I do know from reasearch is mixxing saltpeter KNO3 to nitr
methane will make nitromethane shock sensitive so that is definitly
non starter to use fuel which has any nitromethane added

I am assuming that even if  salt peter KNO3 or some such other suitable
chemical is mixxed with fuel like methanol there existst the probabilty
that there will still be a need for extra oxegen from somewhere

I was hoping then to use nitro oxide in preference to LOX as it looks
cheaper and easier to use than LOX when using small amounts but LOX
might be cheaper in large amounts if I am forced to do methanol LOX
solutions

Basically once I can solve the fuel oxidation issues i can start to
construct a simplex reactor (rocket ) motor to suit the fuel

mayby somebody who knows the real engineering issues of fuels and motor
components might have practical solutions

I shall assume for  practical purposes that i can pump the fuel into
the motor using simple air pressure from a bike pump into a suitable
container such as RC undercarage air supply tin can or some spring
loaded syringe solution  whatever but pumping mayby 25cc or one onze a
second wont be so easy

The first trials will be done on RC car on the ground to test the
princibles before becoming airborne

any realy realy good ideas shoot  but spare me the ram jets and puls
jet andAP realoadbles

Ralf