Login    Register
User Information
Username:
Password:
We are a free and open
community, all are welcome.
Click here to Register
Sponsored
Who is online

In total there are 65 users online :: 5 registered, 0 hidden and 60 guests


Most users ever online was 218 on Wed Dec 07, 2016 6:58 pm

Registered users: anello, Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot] based on users active over the past 5 minutes

The Team
Administrators
Global Moderators
global_moderators.png CS

Ramjet Sabot

A place to ask general spud cannon related questions.
Sponsored 
  • Author
    Message

Unread postAuthor: PaperNinja » Wed Dec 12, 2012 9:01 pm

Actually, a scramjet would be better, they are capable of higher speeds
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Wed Dec 12, 2012 9:23 pm

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
  • 0

Attachments
Results.png
Closeup of the edge of the projectile with a 500 Kh/s flow around 2000 Psi just behind the head enough to ignite a oxy-hydrogen mix
projectile.png
projectile.png (15.78 KiB) Viewed 542 times
User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Thu Dec 13, 2012 1:51 am

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 :wink:
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Thu Dec 13, 2012 9:33 am

idk i will do some free flow sims today
  • 0

User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Thu Dec 13, 2012 10:04 am

Hey is that projectile above a ramjet or scramjet? I forgot to ask earlier...
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Thu Dec 13, 2012 5:59 pm

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
  • 0

User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Thu Dec 13, 2012 6:56 pm

Shockwave :twisted:

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 :roll:

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.
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Sponsored

Sponsor
 


Unread postAuthor: ferret_guy » Thu Dec 13, 2012 10:12 pm

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...
  • 0

Attachments
projectile.png
User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Thu Dec 13, 2012 10:14 pm

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 :oops:

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
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Thu Dec 13, 2012 10:20 pm

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
  • 0

User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Thu Dec 13, 2012 10:22 pm

How do professional accelerators avoid blowback? I'm gonna research a bunch and see if I can comeup with anything...
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Fri Dec 14, 2012 1:10 pm

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)
  • 0

User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: PaperNinja » Fri Dec 14, 2012 1:36 pm

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.
  • 0

User avatar
PaperNinja
Sergeant Major
Sergeant Major
 
Posts: 190
Joined: Sun Jun 17, 2012 7:51 pm
Location: Droneland
Reputation: 0

Unread postAuthor: ferret_guy » Fri Dec 14, 2012 5:44 pm

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.higgins/AIAA-18209-632.pdf
  • 0

User avatar
ferret_guy
Specialist
Specialist
 
Posts: 42
Joined: Mon Jul 23, 2012 11:36 am
Reputation: 0

Unread postAuthor: ramses » Fri Dec 14, 2012 8:07 pm

As I remember, Autodesk CFD doesn't simulate compressible fluids.
  • 0

POLAND_SPUD wrote:even if there was no link I'd know it's a bot because of female name :D
User avatar
ramses
Major General
Major General
 
Posts: 1679
Joined: Thu May 29, 2008 6:50 pm
Reputation: 3

PreviousNext

Return to General Spud Cannon Related

Who is online

Registered users: anello, Bing [Bot], Google [Bot], MSNbot Media, Yahoo [Bot]

Reputation System ©'