Solid Fuel Annular Aerospike / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Solid Fuel Annular Aerospike

1 2 3 next

Move Thread

LAN_403

Chris

Sat Feb 10 2007, 07:27AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

I've made this little aerospike engine for fun; I found it much easier to make than a high quality traditional nozzle. The spike is made of graphite, which I shaped by hand on my drill press with files and sandpaper. I shaped the copper outer nozzle by hitting it with a hammer while heating and turning. It's an inward/outward core burning design where one layer of fuel burns outward toward the casing, and the other inward toward the core from a ring-shaped chamber. That way the burn area should remain constant for the entire burn. The spike simply unscrews to reload the engine. Air can pass through the core and out the end of the spike, providing both virtual spike length and cooling the core stem. Propellant is magnesium and potassium nitrate composite with epoxy. This engine is probably a bit heavy for a high altitude flight, so it is mainly just a fixed testbed engine to experiment with the concept of amateur aerospike nozzles.

Tests coming very soon!

ragnar

Sat Feb 10 2007, 07:42AM

Registered Member #63 Joined: Thu Feb 09 2006, 06:18AM
Location:
Posts: 1425

That's really neat, Chris. May I ask from where you sourced your graphite?

Chris

Sat Feb 10 2007, 07:47AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

I got the graphite on ebay. It was a large plate, but I have also gotten cylinders and things, and there is often a variety of shapes and stuff.

...

Sat Feb 10 2007, 08:34AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Aerocon carries a lot of homebrew rocket parts, although it takes all of the fun out of it if you just buy the pieces

Also, firefox is a great place to get all of those quasi-illegal chemicals. Their igniter kits (unmixed pyrogen = 100% legal in the states) totall rock BTW.

In any case, sweet motor! I would sorta like to get into diy motor making, but I just decided to do get a hybrid motor from west coast hybrids and just pretend that I buit it (heck, it comes as an aluminum tube with treads on one end, 2 spun aluminum bulkheads, and some o-rings) since I prefer to get the rocket off the ground so I can get some of that sweet GPS data

AndrewM

Sat Feb 10 2007, 10:55PM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

I'm not sure you're going to get much love out of this engine. The aerospike concept helps to minimize the effects of the transistion from over to under expansion, which is only a problem when you go from sea level to very very high. This little guy probably isn't going to benefit, but it looks cool.

Alex

Sat Feb 10 2007, 11:35PM

Geometrically Frustrated
Registered Member #6 Joined: Thu Feb 02 2006, 04:18AM
Location: Bowdoin, Maine
Posts: 373

Yeah, it is quite heavy and bulky. As Chris said, it's mainly a test of the concept.

Hopefully if this one works out, he'll try making a lighter one that will fly. Maybe he'll tell us if he has any plans for that...

Chris

Mon Feb 12 2007, 05:41AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Alex got it right, this engine is simply a tool for researching amateur aerospike design. The aerospike nozzle is by nature heavier than a traditional nozzle, and less efficient at a fixed altitude, but larger amateur rockets do indeed go high enough to benefit from the design. All my rocketry work so far has centered around static testbench engines for measuring thrust and impulse, and this is no different. Perhaps later I can move on to lighter weight flight-capable models.

This engine is now packed with 230g of propellant, comprised of 10.8% magnesium, 10% epoxy, and 79.2% potassium nitrate. I tested 40g pellets of 3 different compositions of those ingredients (all stochiometric with both the magnesium and epoxy but with different amounts of either) earlier today and found that one to have the most appropriate burn rate. The propellant is relatively hard to ignite. It has a fairly course grain. The two-way core burning design was very difficult to pack, hopefully I got it tight enough down in there.

Here's a shot of the packed burn chamber.

AndrewM

Mon Feb 12 2007, 07:13AM

Registered Member #49 Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362

Chris wrote ...

larger amateur rockets do indeed go high enough to benefit from the design.

how high would you say that is?

Chris

Mon Feb 12 2007, 07:26AM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

Probably anything above 10,000ft, which is barely achievable by smaller rockets. Larger amateur rockets can go a few times higher than that, with the biggest ever private rocket (though very well funded) going something like 380,000ft.

Steve Conner

Mon Feb 12 2007, 10:31AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Even if it's not as efficient as a normal rocket nozzle, it's still a pretty neat project IMO, in a "Who turned my rocket inside out" kind of way. I'm looking forward to seeing what it does

1 2 3 next

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob