Ramjet Sabot

[PaperNinja]

Actually, a scramjet would be better, they are capable of higher speeds

[ferret_guy]

But they require much higher speeds initially i am currently playing with ideas in Autocad CDF i will post results shortly

Edit:
After several different destines this is the one that did the best

[PaperNinja]

Hm, thank you!

It kinda makes sense that shape, because the "pressure point" is so far forward, by the time the gas ignites it has a lot of surface area to push on, unless I'm thinking of it the wrong way.

I'm still hoping those guides can double as fins

[ferret_guy]

idk i will do some free flow sims today

[PaperNinja]

Hey is that projectile above a ramjet or scramjet? I forgot to ask earlier...

[ferret_guy]

It has charastics of both but more similar to scramjet

Edit: It looks like it ill flw well with the fins

But it will make an epic shockwave

[PaperNinja]

Shockwave

Though with a projectile like that you'd need a sabot, or else it'll be really not airtight (for the injector) and inefficient...

Now if only I had a Hawaiian island so this could be like a 70-stage accelerator

How small will these projectiles be? I should be done with a .22 caliber 40x hybrid sometime after Christmas, which could be an injector for the accelerator.

[ferret_guy]

This is what happens when it moves too fast (it ignites the gas in front of it) blow back seems like it would be bad...

[PaperNinja]

Well as long as the injector seals against the accelerator, blowback should be TOO much of an issue, as long as the injector can take the pressures.

Also, I recently edited my above post, not sure if you noticed.

Edit: looks like I misunderstood your post

That does seem like an issue, like a jet firing it's engine backwards... Though if it's going supersonic, I don't quite understand why that would happen

[ferret_guy]

The projectiles are 2in in diameter and by blow back i mean it would ignite the gas in-front of it blowing the projectile back into the gun

[PaperNinja]

How do professional accelerators avoid blowback? I'm gonna research a bunch and see if I can comeup with anything...

[ferret_guy]

I would love to see this built and played with I think it could be a new era for spud guns (that of the ridiculously expensive projectiles shot at extremely high speeds just because you can)

Edit: After duble checking my math you would need pressures in the 190,000psi to get the oxygen/hydrogen gas to get it up to the 1095deg F required for ignition. I was looking at butane due to its much lower spontaneous ignition temperature (However I a assuming that just the pressure increase is creating the change in temperature not anything additional so this could be inaccurate)

[PaperNinja]

Hm, 200k psi is a little high for any commercially available tubing... Though I have seen 100k psi rated.

That's not the only thing igniting it however, because the flame front from the injector should help light the gas. Once the cycle is started, I believe the flame front behind the projectile should help light it.

Also, though it doesn't have to be mini, or just petit, I think a small caliber than 2" would probably be more fun.(not so much huge heavy stuff to store/transport) also, it's very hard to find stuff (or make it) that's safe with extreme pressures at so large a size.

[ferret_guy]

Well I did a little digging and Autodesk CDF cannot simulate the shock wave in sutch a small space as the tube, so the shock wave would impart enough energy on the gas to ignite it, at least according to what I read. I will have to brush up on my, well everything.

Edit: here is one of the papers that I thought was the best
https://people.mcgill.ca/files/andrew.h ... 09-632.pdf

[ramses]

As I remember, Autodesk CFD doesn't simulate compressible fluids.