Ramjet tidbits

[Zippiot]

i started forming a nozzle with regular clay that shrinks <7%. it is drying now, i can dremel it to fit once it is fired. i tried modeling clay (sculpy) just for kicks, it hardened up around 400 degrees but started to burn around 700, and was completely engulfed in flames around 1000. sculpy might work great as a rocket fuel, mix some of it with enough oxidizer and bake it in the oven around 350-400, it should harden up solid to wutever shape you want.

[Najm]

If the insides of a ramjet are coated or covered with ceramics wuold it generate more thrust because of all the heat energy going out to heat the exhaust rather than the walls of the ramjet?

[Zippiot]

it depends, some ceramics absorb and dissipate heat, others deflect it. if it dissipates heat then you lose power, if it deflects it then you gain power.

[Zoch]

How about http://en.wikipedia.org/wiki/Grancrete?

It's a new type of concrete based off ceramicrete, the stuff in nuclear power plants. It's got a short cure time and can be sprayed onto a mold, and it's fire resistant.

[Zippiot]

33 bux for 50 pounds...i doubt i will ever need that much...

[El-Kablooey]

Kitty litter is a clay called bentonite. It makes great disposable nozzles, and it's about the simplest and easy a method you'll find. All you do is drop a little into your casing (dry) and pound it in with a wooden dowel. Taper the end of the dowel to the correct shape for forming your nozzle. Keep adding kitty litter and pounding on it until your happy with it. Then all you have to do is drill out the center.

[Zippiot]

doesnt bentonite cause horrific lung dammage? i had heard of the kitty litter thing im just too emabrassed to ask my neighbors for a scoop of kitty litter, i already got cement it works fine

[Al Belli]

Hi,

Bentonite is a type of clay, and as with other fine materials, should not be inhaled.
Bentonite is non toxic, and is used in animal feed as a modifier.

Al Belli

[Najm]

Can there be a ramjet inside a ramjet design?
Air flowing in the outer ramjet will take away heat from the walls of the inner ramjet and create additional trust(by expansion).

[Zippiot]

they have done that with rockets. a rocket inside of a tube, the tube channels air with the exhaust and creates slightly more thrust, but so far they have not made an efficient model.

little ramjet inside of big ramjet...

different design speeds or are both made to run at the same speed?

[Najm]

different design speeds or are both made to run at the same speed?

Could do with a bit of experimenting to find out what gives the greatest increase in thrust. It would take a bit of time to do that though.

[Zippiot]

i guess it depends on what you are looking for...

if high speeds are wanted then maybe big ramjet is set for speed, if efficiency is wanted then setting the little ram for high speeds...the second should also get up to speed faster (based on no scientific experimentation)

what if, there are multiple intakes all coming out the same exhaust, and each is opened at the right speed and closed at the wrong speed. this might jsut work, no multiple ramjets no having to light more than 1, constant burn through many speed designs!

i might just try this, i got 2 speeds of forced in air, shop vac without nozzle (around 200-250 mph) and with nozzle (400+mph!!! but same amount of airflow...)


and i have an interesting idea for fuel and flameholder, but i must work them out before i psot them for all of you out there to pick apart

[Greg O'Bryant]

Just one more thing about nozles. I have made caly nozles for my rocket motors. A trick that I learned to help it pack together is to mix some oil to powdered clay (just enough to so it clumps up but isn't damp yet). Tamp this around a nozle and it comes out very solid, doesn't shrink and is resonably heat stable.

[Zippiot]

what kind of clay?

the kitty litter stuff (bentonite was it) or some other clay?

i like mixing sodium silicate with anchoring cement, the cement expands and is quite strong (even stronger with fiberglass shards mixed in)

[Greg O'Bryant]

Just powdered pottery clay. I'm shure anythig would work like kitty litter