If a butterfly in Brazil flaps it's wings...
On Jun 16, 2015 7:08 AM, "R Dierking" <applerocketry@xxxxxxxxxxx> wrote:
Perhaps there have been similar discussions on other chat groups? Seems
we have just become accustomed to rockets taking weird paths occasionally.
But there has to be a reason. Perhaps other than rocket instability or a
deflecting rail, there’s several things we could do to reduce this from
happening. Like relocating the rail buttons; perhaps it’s not even that
difficult.
For example, I’ve wondered if it would help by rotating the pads 90
degrees so the usual wind doesn’t push the rocket ‘sideways’ as it travels
down the rail. Does this make sense?
It would be nice to have some information and analysis for rockets that
have ‘weird’ liftoffs. Sometimes the answer is right there, it just takes
close attention.
Anyway, for the large launch pad on a trailer, I’m going to start with
some basic ideas and go from there. You must have a massive or well
anchored/stable pad base with a blast deflector that will not move the base
during initial thrust, and a rigid guiding structure. It would be nice to
have a launcher like the ones used for sounding rockets, but this pad must
be mobile. I need to work on the logistics a bit, because presently my
trailer storage spot is not large enough for my camper trailer plus this
new utility trailer. I’ll post back in several months and hopefully will
have some progress.
*From:* Bryce Chanes <dmarc-noreply@xxxxxxxxxxxxx>
*Sent:* Monday, June 15, 2015 11:36 AM
*To:* roc-chat@xxxxxxxxxxxxx
Richard.
My observations from last years XPRS when Aeropac had their new
"Trans-America Tower" or Uber Uber Rail, (A 30' tall radio tower with a
rail on it) and used it to launch the ARLISS projects, was that even with
30' of rail launching an M, in most if not all cases the rockets were sent
off in a random direction when they reached the top of the rail, even
though they are considerably stable rockets, and the wind was low to
non-existent.
I don't know, but to me, having a rocket fly straight off the pad is more
than just a more stable rocket and longer/stronger tower.
Very interested.
Bryce Chanes
At Jun 15, 2015, 9:55:44 AM, R Dierking wrote:
First, I’m wondering how much stiffer a 1515 is than a 1010 rail? Cross
section is 50% more, so approximately double?
One of my last fights over a year ago now (way too long ago) was a K1275R
off one of the back pads using a 1010 rail. The rocket went noticeably West
immediately after leaving the rail and it wasn’t the wind. Luckily, the
rocket landed close to the pad because of the wind during descent. One time
the wind really helped.
There’s always a lot of discussion about rocket stability, but think about
how important a reliable launch pad is. Of course, what engine in what
rocket is very important to how massive/stable the pad must be and how long
the guiding structure should be. Regardless of size, I think there is some
occasional thrust vectoring with AP engines that takes place moments after
ignition that seems to stabilize. What would be the reason that some
rockets left the rail in the Punisher drag race at an angle? I’m curious if
other people believe momentary thrust vectoring occurs?
If you are going over say 10K’ in a location like Lucerne Dry Lake, you
need to be reasonably sure that the rocket is stable (of course), and that
it’s going to fly in the direction you choose.
I’ve been considering launch pad designs for several years, and checked
out all the custom pads at the last two BALLS launches I’ve gone to. Some
are really cool with elaborate pad leg designs and lifting mechanisms but
the ones with a sturdy/stiff launch rail adequately supported along its
entire length seem the best to me. This is my opinion, and I might be a
little jealous of the money some spend on their launch pads.
I’m considering purchasing a 12’ x 5” utility trailer for the base of a
launch pad that would also be a platform for a test stand. The pad would
use the triangular aluminum tower material that seems to be popular for
many large launch pads. A link follows that shows a base for an antenna
tower. * I would like to know if anyone else is interested in
participating in the construction of a large launch pad/test stand. It
would serve as our launch pad/test stand at ROC and FAR launches and be
very useful for XPRS/BALLS.*
*http://www.dipolnet.com/footing_for_aluminum_antenna_tower_E9151.htm
<http://www.dipolnet.com/footing_for_aluminum_antenna_tower_E9151.htm>*
Richard Dierking
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