That sounds like a plan, but I'd probably suggest using a non-water fluid
for soaking your sand, otherwise any residual moisture could develop
bacteria and/or leech into your printed structure and weaken it -- or just
make sure you empty it out every so often and clean it....
On Tue, Jan 31, 2017 at 10:57 AM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
Perhaps many people didn’t gain anything by this discussion, and I would
be sorry to hear that.
However, I have. I’ve been able to read the comments and it’s helped me
work through my own challenge of deciding what I was going to do for my L3
and its Nike Smoke nose. I planned everything else before beginning to
build, but not the nose, including the place for GPS.
I’m going to 3D print a thin-walled cone that will fit inside the tip of
the nose and choose it’s base diameter to continue as a tube. Then, based
on sim, I’ll determine the amount of mass to add, use wet sand because it
packs better and add until I reach the target amount of mass. This cone
and tube will then be sealed and placed in the tip of the nose with a
minimal amount of silicone. The rest of the space in the nose will be for
the tracking and of course the bulkhead for the u-bolt.
I’ll sim both the sand and using the metal density data supplied in
previous posts and see how much difference it makes in stability.
OK?
Richard Dierking
*From: *Alexander Jones <uscjones@xxxxxxxxx>
*Sent: *Tuesday, January 31, 2017 10:12 AM
*To: *roc-chat@xxxxxxxxxxxxx
*Cc: *Allen Farrington <allen.farrington@xxxxxx>
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
I think the key is how the the rocket structure is actually built. The
assumptions I've seen here are that the rocket is either going to stay
together and come in ballistic (and then hit as if it's a solid mass), or
break apart and come down in pieces, but nobody has addressed what happens
at impact, whether it's a complete rocket coming in ballistic, or large
pieces (like the nose cone). If you've got a thin molded fiberglass cone
that's going to basically shatter at impact, then yes, absolutely a bag a
sand is going cause less damage than an equal-mass lump of lead, especially
one that structurally reinforces the tip of said nose cone, but if you've
got a stiff FW nosecone with an aluminum tip on it, that thing's more
likely to drive itself THROUGH whatever it hits (with the possible
exception of a boulder or something), and the type of material you're using
for mass isn't going to make a difference. If you want to make a nose
weight as safe as possible, you add a substructure that's designed to
attenuate the impact (like crumple zones in a car), then place your mass
behind that, and you can make your mass as dense and as solid as you want,
then it won't cause nearly as much damage bc all the kinetic energy will be
absorbed by the destruction of your structure. You definitely don't want
to use a fluid, bc unless you seal it in a completely airless rigid
chamber, it'll slosh, and then you run into stabilization issues as your CG
wildly and randomly shifts (read/watch the description why the first probe
launch failed in The Martian). If your rocket's shredding at altitude so
badly that your nose cone actually ruptures and sprays your nose weight
everywhere, then I think you've got bigger problems than what kind of nose
weight you're using.
On Tue, Jan 31, 2017 at 9:48 AM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
I too am a little confused why some people don’t seem to be understanding
what I’m talking about. It has to be mostly me.
What happens to the dispersion of debris from a rocket that ‘comes in
hot’ from let’s say less than 45 degrees vertical?
Would it be different for a nose with sand vs. a nose with nails and
epoxy? Or, how about a rocket that becomes a ‘land shark’ and comes apart
as it skims the ground?
I’m not a PI attorney and far from it, but would there be additional
problems if someone was injured by a rocket that contained bullets, etc.
vs. sand.
Maybe people shouldn’t give any consideration to what goes in their
rockets when it comes to dead mass? Stuff that does nothing but adds
mass. I will, but that’s my choice. Some projects are really unique and
may actually require high densities. I’m thinking most don’t and having
the center of the dead mass back slightly because of the lower density will
not make a difference. People seem to accept things that make large
differences all the time and don’t blink.
And, for the stuff I’m building that has a lot of metal components, you
will never see those projects at a ROC launch. It’s just to dangerous for
the venue.
Richard Dierking
*From: *Allen Farrington <allen.farrington@xxxxxx>
*Sent: *Tuesday, January 31, 2017 9:09 AM
*To: *roc-chat@xxxxxxxxxxxxx
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
Not offended, just bewildered...
I'm out...
Allen
Sent from my iPad
On Jan 31, 2017, at 7:20 AM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
Well, Smith is going to get a kick out of this, but I thought this was
done last night and when I woke this morning and saw all the emails, I
said, ‘oh man.’ I tried to read all the emails that came to me on this
subject. However, some where blocked because of my system’s choices for
junk mail. I bet a forum wouldn’t do that.
This topic is interesting and was posted as an example of how chat
operates when there’s a subject that could be controversial. It was not
designed to be a waste of time. For example, the same day I received
lakebed reports posted over 10 days from the launch. Did I consider
getting this group of emails a waste of my time? Yup, I did. Still, not
everyone did, and I see that too. But, it’s chat and I get them all.
So, I wake up in the morning and 10 people have posted replies, comments,
and even direct questions to me. How do I answer them?
Here’s one: To Allen: No
Oh, and there’s another one I didn’t see. And, some funny comments I
need to read through.
I made the subject line, Prohibiting Metal for Nose Weight. I didn’t
list things that I thought were particularly bad like nails, shot,
bullets. Also, I didn’t put rocks in the subject line. Although kids
probably insert rocks in the nose for weight.
Someone said it would be better to have a large solid mass free falling
then a bunch of bb’s. My point was don’t use either.
Yeah, I didn’t give the perfect answer or solution to my subject line,
but I did give some alternatives. Just saying, before you use nails and
epoxy, think if you can use something else. There are things that would be
a public relations nightmare to explain.
And, to Allen, please don’t be offended. I was just saying “No” to make
a point. Your post is interesting, but that’s not what I thought the major
problem is with using pieces of metal. Although, the two types hitting
something like an RV might yield different results. But then, Myth Busters
is pretty much gone.
Richard Dierking
So, can I get back to my rocket projects? 😊
*From: *Adrian P. Bailey <adrian@xxxxxxxxxxxxxxx>
*Sent: *Tuesday, January 31, 2017 3:16 AM
*To: *roc-chat@xxxxxxxxxxxxx
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
Sorry, I replied to the wrong post. It’s hard to tell when they are all
via email… ;)
*From:* roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@freeli
sts.org <roc-chat-bounce@xxxxxxxxxxxxx>] *On Behalf Of *David Erbas-White
*Sent:* Monday, January 30, 2017 11:51 PM
*To:* roc-chat@xxxxxxxxxxxxx
*Subject:* [roc-chat] Re: Prohibiting Metal for Nose Weight
On 1/30/2017 11:46 PM, Troy Monroe Stacey wrote:
...and if I use charcoal for weight, and it comes in ballistic, will I
have a diamond when I'm done??? <G>
David Erbas-White
BTW, Allen - I was thinking more about your scenario and my first
assumption was that you were saying that the lead is already a lump, and
sand, due to heat, would become a lump too, so there's no benefit to use
sand over lead. Plus I was thinking that even superheated and fused, the
lump of glass would probably be a bigger lump than the lead and could
actually be worse than lead because it occupies more space. However, I was
thinking more and I'm wondering now if the heat from impact would render
either material molten and simply fragment into tiny shards either way?
What do you think? Although from a safety aspect, this is all meaningless,
since these things occur at impact and if that impact was a car or a
person, the damage or injury would be the same, correct?
