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Ooooh hey, would it be possible to build a RAMJET-type rocket engine?  Something with a forward-pointing scoop that forces more air into the combustion chamber when the rocket accelerates.  You could do that with clay I think, if it can withstand the heat and pressure...

Bah, you would never be able to produce a sonic boom with a model rocket.  It wouldn't make any more noise than a "regular" rocket.

Tallgeese wrote:

A thin sheet of steel shouldn't be TOO heavy, should it?

No, but it will burn away pretty quickly.  You need a material that resists changing temperature; steel is (of course) metal and has a relatively high thermal conductivity.

Grout, plaster or clay all have drying times. If you can wait 24 hours for the grout or plaster give them a try or baking of clay.

What about fiberglass? I know bondo used to sell a fiberglass repair kit for boats and other fiberglassed bodies. The kit would come with a number of fiberglass cloth strips which then would be covered with the bondo epoxy. Dunno maybe an idea?

EDIT:
Went to bondo's site wow has their product line grown.
http://www.bondo-online.com/catalog_bro … ?parNbr=24
They still have fiberglass but which one? Then there's Dyna-Glas the high end pro stuff. Have no idea if it would be better or suitable.

Last edited by LLEVIATHANN (2006-01-24 4:56 pm)

Wiki On Fiberglass wrote:

Chemistry
The basis of textile grade glass fibers is silica, SiO2. In its pure form it exists as a polymer, (SiO2)n. It has no true melting point but softens up to 2000°C, where it starts to degrade. At 1713°C, most of the molecules can move about freely. If the glass is then cooled quickly, they will be unable to form an ordered structure (Gupta, 544). In the polymer it forms SiO4 4- groups which are arranged as a tetrahedron with the silicon atom at the center and four oxygen atoms at the corners. These atoms then form a network bonded at the corners by sharing the oxygen atoms.

The vitreous and crystalline states of silica (glass and quartz) have similar energy levels on a molecular basis, also implying that the glassy form is extremely stable. In order to induce crystallization, it must be heated to temperatures above 1200°C for long periods of time (Loewenstein, 6).

Molecular Structure of GlassAlthough pure silica is a perfectly viable glass and glass fiber, it must be worked with at very high temperatures which is a drawback unless its specific properties are needed. It is usual to introduce impurities in the form of other materials into the glass to lower its working temperature. These other materials also impart various other properties to the glass which may be beneficial in different applications. The first type of glass used was soda-lime glass or A glass. It was not very resistant to alkali. A new type, E-glass was formed that is alkali free (< 2%) and an alumino-borosilicate glass (Volf, 338). This was the first glass produced for continuous filament formation. E-glass still makes up most of the fiberglass production in the world. Its particular components may differ slightly in percentage, but must fall within a specific range. The letter E is used because it was originally for electrical applications. S-glass is a high strength formulation when tensile strength is the most important property. C-glass was developed to resist attack from chemicals, mostly acids which destroy E-glass (Volf, 340).

Since E-glass does not really melt but soften, the softening point is defined as, “the temperature at which a 0.55 – 0.77 mm diameter fiber 9.25 inches long, elongates under its own weight at 1 mm/min when suspended vertically and heated at the rate of 5°C per minute” (Lubin, 152). The strain point is where the glass has a viscosity of 10 14.5 poise. The annealing point, which is the temperature where the internal stresses are reduced to an acceptable commercial limit in 15 minutes. The viscosity at this point should be 10 13 poise (Lubin, 152).

Way out on a limb here and have not a clue. but it was fun.

Fried Chicken wrote:

jeff-o wrote:

Ooooh hey, would it be possible to build a RAMJET-type rocket engine?  Something with a forward-pointing scoop that forces more air into the combustion chamber when the rocket accelerates.  You could do that with clay I think, if it can withstand the heat and pressure...

That would produce the sonic boom....


Anyway, I think I need some sort of clay/grout/cement.  I don't mind waiting 24 hours for it to harden, that's not too bad...  Now, grout would be easiest... what kind of grout should I get?

No idea.  I've never had to buy grout before.

Hmmm, one article I found mentioned that the gases right at the narrowest part of the nozzle are travelling at mach 1.  That's still not enough to move the whole rocket at mach 1, though.

Fried Chicken wrote:

For now, I stick with small rockets that cannot do any harm.

just how much powder are you using? and what's it's burn rate under compression?

it really doesn't take too many grains of powder to be calling you "Lefty" or "Lucky" should you survive a rapid burn with too little pressure release.

I suggest a cinder-block launch silo...  and a good 20-30 feet.

I agree with jeff-o.. with one addition.
that's 20-30 feet THICK.

burn rate > containment = boom.
and don't think it won't go boom if you contain it.
you will probably be famous one day.. just hope it's not Darwin Award famous.

Last edited by macnuke (2006-01-25 5:41 pm)

You could try to replicate the Estes rocket engines.  Get a long sheet of paper, coat it with glue on one side, and wrap several layers around a diameter large enough to contain the rocket fuel (a thick marker, maybe).  Once the paper layers are about 3/16" to 1/4" thick, they should hold in the pressure just long enough for the fuel to burn out.

Well, I have my tubes, like I have said a million times.  I got them from http://www.cannonfuse.com

They are perfect for rockets.  I need the rocket nozzle, but yes, those are very good instructions for improvising if you (god forbid) run out of materials.

jeff-o wrote:

alright then, back to nozzles.

How about magnesium? 

Actually, to be honest, I just bought 2, 4 ounce rods of 99.8% pure magnesium on ebay   I might make a post on that...

And it would make a beautiful signal flare