rail gun
Michael Koppelman
Are there Tripoli rules related to this? Could we rail gun launch a
rocket up a few thousand feet and then airstart? Why carry all that
propellent up with you if you can instead get the energy from ground-
based equipement?
M.
Bill Kalsow
That's the whole idea behind a multi-stage flight. Drop booster weight
as soon as possible to make the rest of the flight efficient. The
non-resuable cost of the booster propellant is the downside.
From my reading of the Tripoli safety code, it looks like ground-based
assists are allowed. Here's section 11 of the HPR safety code:
http://www.tripoli.org/Launches/Safety/HighPowerSafetyCode/tabid/185/Default.aspx
11. Launching Devices
1. Launch from a stable device that provides rigid guidance until
the rocket has reached a speed adequate to ensure a safe flight path.
2. Incorporate a jet deflector device if necessary to prevent the
rocket motor exhaust from impinging directly on flammable materials.
3. A launching device shall not be capable of launching a rocket at
an angle more than 20 degrees from vertical.
4. Place the end of the launch rod or rail above eye level or cap it
to prevent accidental eye injury. Store the launch rod or rail so it is
capped, cased, or left in a condition where it cannot cause injury.
Rail guns seem a bit exotic (and probably pretty expensive to produce).
I would think an air cannon would be more in line with what we could
actually produce. The world record for a 8-10 lb pumpkin is 4483 ft:
http://en.wikipedia.org/wiki/Pumpkin_chunking
http://science.discovery.com/videos/punkin-chunkin-2009-air-cannons.html
http://science.discovery.com/videos/punkin-chunkin-2009-young-glory-iii.html
____________________________________________________________________
Bill Kalsow
Wayne Johnson
Now it's been a few years since I took Physics, so check my math...
The speed formula is s=sqrt(d/a) where d is the distance traveled and a is the acceleration. Forgive me, I used feet...
| Rail length (ft) | |||||||||||||
| Acceleration(g) |
2 | 5 | 10 | 20 | |||||||||
| 10 | 35.88872 | 56.74504 | 80.24961 | 113.4901 | |||||||||
| 20 | 50.75431 | 80.24961 | 113.4901 | 160.4992 | |||||||||
So, for a 5' rail gun at 20g acceleration, we get 80ft/sec or about 54 mph.
---
Wayne Johnson, | There are two kinds of people: Those
3943 Penn Ave. N. | who say to God, "Thy will be done,"
Minneapolis, MN 55412-1908 | and those to whom God says, "All right,
(612) 522-7003 | then, have it your way." --C.S. Lewis
From: Bill Kalsow <kal...@comcast.net>
To: tripo...@googlegroups.com
Sent: Wed, September 15, 2010 9:51:45 AM
Subject: Re: [tripoli-mn] rail gun
http://groups.google.com/group/tripoli-mn
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Michael Koppelman
mentioned, compressed air or a pyrotechnic of some sort. Point the
pumpin chucker straight up and light the motor at maximum velocity and
you get a nice head start. If my math is right, if they can chuck an
8-10lb pumpkin to 4483' then can chuck it straight up to half that or
2200'.
M.
> > Are there Tripoli rules related to this? Could we rail gun launch a
> > rocket up a few thousand feet and then airstart? Why carry all that
> > propellent up with you if you can instead get the energy from ground-
> > based equipement?
>
> That's the whole idea behind a multi-stage flight. Drop booster weight as soon
> as possible to make the rest of the flight efficient. The non-resuable cost of
> the booster propellant is the downside.
>
> From my reading of the Tripoli safety code, it looks like ground-based assists
> are allowed. Here's section 11 of the HPR safety code:
>
> 11. Launching Devices
>
> 1. Launch from a stable device that provides rigid guidance until the rocket
> has reached a speed adequate to ensure a safe flight path.
> 2. Incorporate a jet deflector device if necessary to prevent the rocket
> motor exhaust from impinging directly on flammable materials.
> 3. A launching device shall not be capable of launching a rocket at an angle
> more than 20 degrees from vertical.
> 4. Place the end of the launch rod or rail above eye level or cap it to
> prevent accidental eye injury. Store the launch rod or rail so it is capped,
> cased, or left in a condition where it cannot cause injury.
>
> Rail guns seem a bit exotic (and probably pretty expensive to produce).
>
> I would think an air cannon would be more in line with what we could actually
> produce. The world record for a 8-10 lb pumpkin is 4483 ft:
> http://en.wikipedia.org/wiki/Pumpkin_chunking
> http://science.discovery.com/videos/punkin-chunkin-2009-air-cannons.html
>
>
> ____________________________________________________________________
> Bill Kalsow
>
> --http://www.tripolimn.org/http://groups.google.com/group/tripoli-mn
> You received this message because you are subscribed to the Google
> Groups "Tripoli Minnesota" group.
> To post to this group, send email to tripo...@googlegroups.com
> To unsubscribe from this group, send email to
Bill Kalsow
> My thought was not so much an electromagnetic one but maybe, as was
> mentioned, compressed air or a pyrotechnic of some sort. Point the
> pumpin chucker straight up and light the motor at maximum velocity and
> you get a nice head start. If my math is right, if they can chuck an
> 8-10lb pumpkin to 4483' then can chuck it straight up to half that or
> 2200'.
Ok, too much fun! :-)
I suppose I can do the math and figure out the muzzle velocity
of a 10lb pumpkin that travels 4483'. Maybe I'll work on it
during the balls trip. (What is the drag on a spinning
pumpkin??)
In any case, I started to wonder what commercial engine would
be able to launch a pumpkin that far. I think the trouble with
larger rocket engines is that they burn too long, much longer
than it would take for a pumpkin to clear a 20-30' barrel.
Finally, I decided to RockSim a pumpkin chunkin attempt. Attached
is my .rkt file and the output from a simulation. I built a
"pumpkin" with a round nosecone, a round transition section, and
a 1" x 54mm motor mount tube. The outside surfaces are "unfinished".
I used the mass override so that loaded with a J1999 engine it weighs
just under 10lbs and the CG is in the center of the pumpkin.
In the first few attempts the 2D visualization of the flights made
it clear that I had a problem with the pumpkin tumbling through the
air while still under thrust (0.67 secs for the J1999). So I ended
up with a *long* 250 ft (!!) launch rod. I set the launch rod at
80 degrees off vertical (only 10 degrees above horizontal!). My
pumpkin flew for just over 9 seconds, with apogee at 290 ft and
landed 2386 ft down range. It's still a long way from the 4483'
world record.
Who wants to make the next attempt?
____________________________________________________________________
Bill Kalsow
Michael Koppelman
that work?
M.
> 3KViewDownload
>
> pumpkin.rkt
> 19KViewDownload
Bill Kalsow
degrees is optimal only under some rather unrealistic conditions. E.g.
No atmosphere, frictionless projectile, ...
It's easy to change the launch rod angle in rocksim. I started at 45
and ended up at 80 to optimize the distance.
Sent from my iPhone
On Sep 18, 2010, at 11:17 AM, Michael Koppelman <michael....@gmail.com