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
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
Richard Dierking
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