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<mailto:uscjones@xxxxxxxxx>
Sent: Tuesday, January 31, 2017 10:12 AM
To: roc-chat@xxxxxxxxxxxxx<mailto:roc-chat@xxxxxxxxxxxxx>
Cc: Allen Farrington<mailto: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<mailto: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<mailto:allen.farrington@xxxxxx>
Sent: Tuesday, January 31, 2017 9:09 AM
To: roc-chat@xxxxxxxxxxxxx<mailto: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<mailto: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<mailto:adrian@xxxxxxxxxxxxxxx>
Sent: Tuesday, January 31, 2017 3:16 AM
To: roc-chat@xxxxxxxxxxxxx<mailto: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@xxxxxxxxxxxxx>
[mailto:roc-chat-bounce@xxxxxxxxxxxxx] On Behalf Of David Erbas-White
Sent: Monday, January 30, 2017 11:51 PM
To: roc-chat@xxxxxxxxxxxxx<mailto: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?
