The stored energy given by Ragnarok assumes an isothermal process, where the system is by definition receiving energy input during the process through heat transfer. A form more appropriate to our purposes (and more in line with what I would call the "stored energy") is E[sub]stored[/sub]=(k[sup](γ+...

Late to the party, but I would dearly love to have the old chat back. It was a veritable fount of fascinating and humorous conversation, and typically contained the highest level discussion anywhere on the site, including the forum. I don't think we abused it - we made it fun. I would jump at the ch...

HGDT is typically less accurate than GGDT for the "common" performance envelopes considered around here, but is probably still within 20% (GGDT can be scary accurate at low speeds, say less than 200m/s). HGDT and GGDT are both 0D codes (meaning that the gas is considered to have negligible mass and ...

You'll want a backstop filling with low/no mechanical strength, and sufficient density to stop your projectile in the available distance without a peak acceleration high enough to damage it. You can use water hammer pressure calculation formulas to get an approximate idea of the stress on the projec...

jackssmirkingrevenge wrote:No correspondingly impressive footage?

The cameras were focused on the test apparatus, not the charging system.
The footage goes like this: *60Hz hum* ... *ominous hissing noise* ... "Hmm, I wonder what's making it do th- *screen whiteout* *BOOM* ... "[expletives deleted]".

Got it in one. I didn't budget enough time to finish the second stage. Had I completed it, performance would have been similar to that of the electric gun I posted two years ago (which is currently out of commission due to a fairly impressive transformer explosion... ).

So the sabot is also the "burst disk"? What mix were you shooting at? The shear skirt is incorporated into the base of the sabot, yes. It's not shown in the FEA output though. This was with 2.75 : 7.24 propylene / oxygen at a pre-ignition pressure of 12.8 bar (absolute pressure - the nitrogen conte...

In the world of spuds today: Sabot design, shear skirts, and 3/8" tungsten carbide ball bearings. http://i813.photobucket.com/albums/zz59/ONKinetics/SabDes1.png http://i813.photobucket.com/albums/zz59/ONKinetics/DSC_1123.jpg http://i813.photobucket.com/albums/zz59/ONKinetics/DSC_1114.jpg http://i813...

You've probably seen this paper before, JSR, seeing as how it's the first Google search result for "sabot design", but it has a neat little dynamic analysis that explains exactly what went wrong with your first batch of projectiles: http://www.dtic.mil/dtic/tr/fulltext/u2/a056428.pdf Basically, that...

Let me first say that it's quite refreshing to see someone using modeling tools around here. I'm quite busy with school at the moment, but I'd be interested in discussing this project with you over the break (starting a week from now). I'm the resident ETG builder here. I love designing them and hav...

D_Hall has it. To give a little background, it's probably worthwhile to elaborate on the boiling process. As you're probably aware, boiling temperature of a liquid is pressure dependent (in the case of water evaporating into air, the water evaporates because its temperature is above the boiling temp...

But now i have a broken fan and i think i have a leak somewhere. When i tried stuffing a potato down the barrel for the second time, i think there was too much air pressure building up in the chamber and it broke the fan from that square plastic thing it's in. I need to make a mental note to take t...

I was about to tell you of the headaches I've had from a similar setup, but D_Hall described it exactly. That's quite likely to be the source of your problem.

jmc, you still haven't given the volume of your fuel meter. Measure it and tell us, or you're not going to get anywhere with this question.

But police are the worst thing to have ruin your day, second only to an exploding gun. Assuming that the exploding gun wasn't immediately lethal and didn't cause paralysis or other permanent disability, I'd take that over the police any day. Nice work, Fnord. I'm looking forward to coming across th...