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J.Lanum

Mon Feb 13 2006, 03:31AM

Registered Member #161 Joined: Mon Feb 13 2006, 03:15AM
Location:
Posts: 20

Hi, I'm a junior in high school, and I'm entering the Science Fair this year. My Title is:

Railguns as Mass Drivers: Are they an efficiend choice for the future?

I have only dabbled in electricity. Okay I wouldn't even call it dabbling. My procedure is to:

1. Build the railgun
2. Fire it and record data
3. Enlarge the data as if NASA were wanting to launch a spacecraft using a railgun.
4. Compare the efficiency of both the mass driver method and the current one used today.

Railgun Specs: (subject to change)

6 inch rails
4 disposable cameras (charging ciruit and capacitors)
I'd like to have an pneumatic injection system, but that seems impossible w/ my time constraints(one month).
My armature will probably be a penny or something that is inexpensive.

My rail gun will be tested in a vertical position in the way a spacecraft is launched. I have been devouring everything I can lately when it comes to railguns to hopefully make for the lack of inexperience.

So I have a month to do this along w/ prepare a presentation. You may ask why wait till now? Well my science teacher only told me of this as the second semester started so thats the reason for the late start. I'm looking at this year as a stepping stone for the next science fair.

Any suggestions. Am I in way over my head?

Michael W.

Mon Feb 13 2006, 03:38AM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

Ok, for 4 photoflash capacitors you will only have about 14.4 Joules (not alot) which will mostly make a large bang, which is a potentially dangerous bang under perfect (or unperfect conditions) when fired but not alot of propulsion, I think a better bet for you would be a rudimentary coil gun which would give more visual results for of electromagnetivity. Although If a rail gun is a must, use tin foil as a projectile. (It will give the most visual results)

J.Lanum

Mon Feb 13 2006, 04:01AM

Registered Member #161 Joined: Mon Feb 13 2006, 03:15AM
Location:
Posts: 20

Thanks for the Input. I have to do a railgun because I've already sent the forms in. What do you think about using Solar Power?

Bjørn

Mon Feb 13 2006, 04:15AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Forget about a classic rail-gun, it is to complicated. Take a look at this: 10 minute rail-gun

The title of the thread is not very informative, it says nothing about what you wonder about.

...

Mon Feb 13 2006, 04:48AM

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

You are going to have problems getting any rail gun action to happen with 15j. I would recommend saying you are using a 'plasma armature' (use a plastic [nonconducting]] projectile using a plasma [created by vaporising a small amount of a conductive material]), and use a closed bore so you use the pressure surge created from the armature exploding to propel the thing.

I would make it (because that is what I have laying around) by:
take a piece of 1/4" plastic (lexan, delrin, whatever), and cut 2 pieces 1" wide and 2" long, and a strip 1/4" wide by 3"
take a piece of 1/4" copper plate and cut 2 pieces 3/8" wide and 2.5" long
Stack the copper in between the plastic leaving a 1/4" gap in the middle
Put the 1/4" piece of plastic in the middle and press the copper up against it to there is a perfect 1/4" gap left
clamp one half in a vise and drill 1/8" holes every 3/8", and bolt it together with stainless hardware
drill the 1/8" holes every 3/8" and bolt that half together, and remove the plastic spacer
then cut a piece of plastic that is 1"x3/4" and set it on the back. Drill holes through to the copper, and tap then for 1/8" 32tpi screws and bolt it on.
Hook the cap bank (though a relay) to the Cu bar hanging out the other side
Glue a piece of Al foil to one side of the 1/4"x3" bar
Cut the 1/4"x3" copper bar into 1/4" long pieces. If they are a really tight fit in the bore sand them down a little
Push one piece down the bore so that it is like 1/8" from the end
Charge up the caps and close the really.
If all goes well you should get a nice sound bang an a piece of plastic shooting out the end with a bunch of sparks...

Good luck and be safe!

J.Lanum

Mon Feb 13 2006, 05:14AM

Registered Member #161 Joined: Mon Feb 13 2006, 03:15AM
Location:
Posts: 20

The 10 minute railgun offers no challenge in my opinion. I like to be challenged which is why I've taken on in my opinion a large task to be done in a month.

Question:
Would I get better results using a plasma armature?
Is it possible to use solar energy to power it?
Do I need an injection mechanism to overcome the static friction?

Thanks for the input so far guys it's really been helpful, but keep it coming. I'll try to have a list of parts up by tomorrow. Oh and sry about my not so informative thread title.

Bjørn

Mon Feb 13 2006, 05:32AM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Would I get better results using a plasma armature?

You will get no result at all unless you get a proper power source. With a few photo capacitors you will get some sparks and a small bang. If you get any detectable movement you will wonder if it is the result of electromagnetism or becaus of rapidly expanding hot air.

Is it possible to use solar energy to power it?

It is not practical, you need hundreds of large solar panels to get the required current. Solar energy can be used to power it indirectly by charging the capacitors. Car batteries are much better than solar energy for driving it directly but then you need to make a rather impressive switch.

Do I need an injection mechanism to overcome the static friction?

It is a well know trick, let the injector do 99.9% of the work and let the sparks fool people into thinking that the capacitors made a difference. You do not need it but it makes life a lot simpler.

J.Lanum

Mon Feb 13 2006, 10:40AM

Registered Member #161 Joined: Mon Feb 13 2006, 03:15AM
Location:
Posts: 20

Ok so I need a proper power source. Where can I find one that is practical yet not expensive? I asked the solar panels question because I could relate it to NASA using solar panels for its launch it would also greatly reduce the cost. I've seen some of the capacitors that like rollette use but I don't think I can afford that.

*edit* How many joules do I need to have a decent launch?

Michael W.

Mon Feb 13 2006, 03:31PM

Registered Member #50 Joined: Thu Feb 09 2006, 04:07AM
Location: Vernon, B.C, Canada
Posts: 324

By decent launch I'm guessing you mean a real railgun, I would guess on a very good rail gun about 25 KiloJoules....

the_anomaly

Mon Feb 13 2006, 03:40PM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

For a pneumatic injection I would get a 12g CO2 cartridge and devise some way to hold it, and then puncture it. Then as the projectile is moving it hits the rails and hopefully plasma will come out behind the projectile and the spectators would think the electricity was responsible. If it all went well 15juoles would contribute to the speed but as BjÃ¸rn BÃ¦verfjord said that would be like0.01%.

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