News from PSFC - New videos on page 2

[reverend]

Well... Ok not really. I'm just having some fun experimenting with home-made rocket fuel: aka Rocket Candy. Potassium Nitrate (KNO3) as Oxidizer and Sorbitol (Artificial Sweetner) as the fuel. 100% success rate on static firings of the first 4 motors. Motor casings are PVC. The throat is a flat washer held in place by plumbers epoxy (putty). The nozzle is cut into the epoxy. I used an electronic ignitor I made by wrapping a bridge wire around a roll of paper soaked in KNO3. These worked pretty good. Next up... I'm going to the moon!

The Rocket Skateboard

Static Test Number 2

The Ignitor

More updates, pictures, and videos throughout the thread.

 

[jarmonik]

These worked pretty good. Next up... I'm going to the moon!

Candy rockets.:speakcool: Just don't shoot down any intelligence satellites on the way. That might cause problems with the authorities.

How's the ISP ?

 

[reverend]

ISP was low compared to other more expensive fuels... These particular motors only had a calculated delivered ISP of 119.6 seconds. These motors only had a Pmax of 350 psi.

With a casing that would withstand higher pressures, and a smaller throat, 140 seconds is attainable with red rocket candy.

I can deal with the lower ISP because of the cost of the fuel is only $1.90 USD per pound, (2.65 EUR per Kg)...

 

[reverend]

Here's specs from Richard Nakka's Spreadsheet

Click below to enlarge it...

 

[reverend]

Just completed some test runs in the simulator with data calculated from this spreadsheet. I am using an unreleased model rocket simulator I made that lets you define the motors thrust curve with a text file or in the scenario file. Notice during the burn (easier to see in the 3rd launch at 0.1x) that upon pressing the launch key the throttle is automatically matched to simulate the thrust curve.

The motor weighed 210 grams. There was 78 grams of fuel. The empty motor should have a mass of 132 grams. This is what I used for the rocket's empty weight. I guess this would simulate shooting the motor off by itself (and expecting it to go straight).

Velocity hit 340m/s, which is why you hear the sonic boom during the launch...:speakcool:

G90 Simulator Tests

 

[jarmonik]

It has a pretty high acceleration then... 35g

If you reduce diameter of the nozzle how much the pressure can raise ? Wouldn't that increase exhaust velocity.

 

[Brad]

35 G's, YIKES! :blink: I'd love to see how the simulation compares with the real thing.

 

[reverend]

It has a pretty high acceleration then... 35g

If you reduce diameter of the nozzle how much the pressure can raise ? Wouldn't that increase exhaust velocity.

Just for scientific purposes, to be clear... the Throat is the narrowest point in the opening (compressing the exhaust), the nozzle is the part that expands away from the throat (expanding the exhaust). Changing the nozzle exit diameter will not majorly influence the chamber pressure (assuming it doesn't get smaller than the throat). The throat and nozzle are often confused and the throat is incorrectly referred to as the nozzle. That's OK though

The throat diameter can be constricted to whatever size you could imagine. Internal pressure can be adjusted to anything as high as 9,000 or 10,000 psi. It's unlikely that a lightweight casing could be made to contain this kind of pressure... so a larger diameter throat is used. This motor has a 1/4th Inch nozzle. If the cross sectional area of the throat was cut in half, we'd get double the internal pressure.

This 1" PVC pipe had a rating stamped on the side of 473 psi. I included a small safety margin and decided on a 1/4 inch throat to keep the pressure at a max of 350 psi.

Thanks for showing some interest

 

[Ghostrider]

Candy rockets.:speakcool: Just don't shoot down any intelligence satellites on the way. That might cause problems with the authorities.

The authorities have never had a need for intelligence anyway. :lol:

 

[reverend]

Just finished my remote control ignitor box! Tested 10 times, works great! I'm using an RC Airplane reciever/transmitter that was originally rated for 1000 yards... I've added this monster antenna that might well double that range. This should give me a very large range of distances for a safety zone (1 mile radius? maybe...)

 

[James.Denholm]

You pyromaniac...

Soon you're going to be dropping V2s on us all...

 

[thomasantony]

While you are at it, drop one on Bart Sibrel. It will make us all happy.

 

[ryan]

I have a whole list of things you can aim it at, some are not people, some is known as a school.

 

[reverend]

I wanted to actually shoot something with my new R/C Ignitor, so off to WalMart I went to buy some Estes motors. I bought a 3 pack of C6-3's and a 3 pack of A8-3's. I had a bag of bamboo skewers surplus from my last bottle rocket program, so I taped each motor to a stick and headed down to the beach. The ignitor worked flawlessly for all 6 motors. I had my buddy handle the "Launch Pad Work", connecting the wires while I walked progressively farther down the beach. By the 6th rocket I was about 1000ft away and it still ignited flawlessly. We had some reasonably good flights with such a simple rocket design too... Sorry no pictures...

What's coming next: I have a 3 grain version of the G90 motor almost built. Initial calculations make this about an H112. I'll post some more information on this new design later. So far I've cut the casing, completed the nozzle end, produced the fuel grains, and inserted them... All that's left is to make an ignitor wire and plug the top.

Sorry about no pictures for recent activities.


OH yea, on the skateboard project. We've remounted the wheels on the other side of the board. This, although looking really weird for a skateboard, will provide a flat top as a platform for mounting a motor, with enough room for a motor bigger than the G90...

It also looks cool on the grounds that we have a big flaming skull painted on the top of the board now...

 

[reverend]

Update: Completed the 3 Grain motor by making the igniter wires and plugging the top with drylock hydraulic cement. This is my first time using cement to plug the end. After recalculating the numbers, this motor will be a G136

Here's the specs:

 

[reverend]

Today's G136 Rocket
Looks crude... That's fine. The motor itself looked perfect before it got taped up.

I just realized another milestone... this is the first time a re-usable component has been used... The stick has flown once before. It was used on "Redneck Rocket I". Here we go for "Redneck Rocket II"...

 

[Notebook]

Are you using Mathcad for your data and graphs?

Also, re: reusable. Are you certain thats the same stick from RNR I? It dosen't look scorched enough to me, and I can't see a barcode or fit for flight number...

N.

 

[reverend]

Are you using Mathcad for your data and graphs?

Also, re: reusable. Are you certain thats the same stick from RNR I? It dosen't look scorched enough to me, and I can't see a barcode or fit for flight number...

N.

The info and graphs come from this spreadsheet
http://members.aol.com/nakkarocketry/soft/SRM.zip

It is the same stick from the first launch... The first one didn't have the nozzle secured enough in the casing and it blew out and ejected the fuel grains... i said this stick once before... I didn't mention it was only about 10 feet... The remainder of the scortched part is now under the tape...

 

[Notebook]

That's a clever spreadsheet, lots of stuff in there.

Re-using a stick thats been in a launch failure, thats ambitious. Still you have to stick with the stick you know. How about putting flight rings on it?

N.

 

[Urwumpe]

On a Steeck! :rofl: