Hey Richard,
You mean density ... The word you're looking for is materials with high
density.
In particular, we're looking for large mass per unit of volume. Lead is 10x
as dense as water, and styrofoam is about one tenth as dense as water. 4
ozs of lead would be 400x the density of styrofoam. density = mass/volume
so we like a material with a high density which could have both high mass
atoms (high mass), and atoms that are closely packed (low volume) resulting
in a high value for mass/volume. Hey guess what, those are called metals :-)
In the periodic table, you can see a stair step starting at Boron (B), and
going all the way down to Polonium (Po), atomic number 84. Except for
Germanium (Ge) and Antimony (Sb), all the elements to the left of that line
can be classified as metals.
My favorite metal there is Osmium, the most dense metal in the world, given
that it is 2x the density of lead, the amount of energy you can put into
that (p=mv) seems that 1/2 the velocity would give you same amount of
energy for, say a 40 cal ammo shot. But Osmium is rare (50 parts per
trillion in the North American continent). Lead on the other hand is very
abundant.
Given the above, it seems you would have less risk with a high density
material like lead, BB's or other ductile metals given you are reducing the
amount of mass per volume. Furthermore, since that low volume of mass can
be located where
it does the most good, I would argue that these metals are safer since you
would have less dense materials.
Consider the nosecone filled with water versus the nosecone filled with
1/10 the volume of lead. Seems to me the nosecone filled with lead is less
risky than that filled with water. One will bury itself, the other crater.
Finally, we've been using lead weights to balance wheels for decades now;
USGS sites a statistic of about 65K tons of lead weel weights out on the
roads for the 200 million cars and trucks driving around in the US, about
2000 tons of this ends up on the roads and gets ground down and put into
the water table and air so it is problematic.
Substitutes range from Zinc, Steel, and composites and it seems 3M is
taking the lead there with a company called E-sys Automation. Seems like we
should follow their research since the automotive industry grapples with
the same problems.
But until you solve that problem I will stick with #8 bird-shot and
epoxy/foam :-)
best regards
-James
On Mon, Jan 30, 2017 at 3:46 PM, R Dierking <applerocketry@xxxxxxxxxxx>
wrote:
OMG, we are going to find out that all things are indeed connected.
*From: *Adrian P. Bailey <adrian@xxxxxxxxxxxxxxx>
*Sent: *Monday, January 30, 2017 3:45 PM
*To: *roc-chat@xxxxxxxxxxxxx; 'R Dierking' <applerocketry@xxxxxxxxxxx>
*Subject: *RE: [roc-chat] Re: Prohibiting Metal for Nose Weight
Methinks this would be a good topic for a forum… ;)
*From:* roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@
freelists.org] *On Behalf Of *richsilv@xxxxxxxxxxx
*Sent:* Monday, January 30, 2017 3:44 PM
*To:* 'R Dierking' <applerocketry@xxxxxxxxxxx>; roc-chat@xxxxxxxxxxxxx
*Subject:* [roc-chat] Re: Prohibiting Metal for Nose Weight
So you’re telling us that 8 pounds of Lava Rock would be OK?
*From:* R Dierking [mailto:applerocketry@xxxxxxxxxxx
<applerocketry@xxxxxxxxxxx>]
*Sent:* Monday, January 30, 2017 3:29 PM
*To:* richsilv@xxxxxxxxxxx; roc-chat@xxxxxxxxxxxxx
*Subject:* RE: [roc-chat] Re: Prohibiting Metal for Nose Weight
Funny. Good story too. But, not discussing bowling balls. Yes,
difference between getting hit with 8 lb bowling ball vs. 8 lb rocket nose;
not much!!! But, there is a significant difference between the potential
impact damage of an 8 lb. solid nose, pieces of metal, or 8 lbs. of
dirt/sand/water.
Also, we are discussing using metal (and in particular things that are
intended to be used for projectiles like bb’s and lead shot), vs.
alternative types of masses.
Richard
*From: *richsilv@xxxxxxxxxxx
*Sent: *Monday, January 30, 2017 3:08 PM
*To: *roc-chat@xxxxxxxxxxxxx
*Subject: *[roc-chat] Re: Prohibiting Metal for Nose Weight
People get strange things in their heads, don’t they…
I recall being very freaked out by the whole notion of a Bowling Ball
competition… I’m like thinking WTF I think I’ll go into town while they are
holding this competition…
Then I got to thinking about what’s in some of my rockets… And chatting
with others with larger projects… Seem to recall that the Gates Porthos had
more than 35 pounds of Nose Weight…
It took me a while to get over that…
And the irony of the situation was just too funny…. My wife and I used to
bowl in what’s called a Vegas League… Without going into a lot of details
about what that is… And we always flew to Vegas… Just consider that between
my wife and I we were bringing 3 or four bowling balls onto the Aircraft
(No, I was not going to let the Gorillas on the tarmac throw around my
pristine bowling balls…)… At the Safety check (this was well before 9-11)
someone got freaked “What, you cant take those on the Plane!”, “Why?” I
asked and the inspector couldn’t come up with much of an answer, but their
antics did finally get a manager over… The manager’s comment was (and I
quote) “What do you think they are going to do, roll the ball up the isle?”
To which there was a great laugh…
Then, when we get on the plane, I’m lifting these into the Overheads… and
people are freaking out (even though they were going be (largely) over my
head too…), a bowling ball up there? “What, you can put 70 pounds of
Purses, Laptops, Briefcases… But you are worried about < 4o pounds of
Urethane? But we complied and kept them on the deck… In those days, they
actually fit under the “seat in front”…
Mass is mass, don’t much matter what it is (as long as you have your
tetanus!) if its coming in ballistic, you’d better not be standing
underneath…
*From:* roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@
freelists.org <roc-chat-bounce@xxxxxxxxxxxxx>] *On Behalf Of *David Smith
*Sent:* Monday, January 30, 2017 2:04 PM
*To:* roc-chat@xxxxxxxxxxxxx
*Subject:* [roc-chat] Re: Prohibiting Metal for Nose Weight
Richard,
One of the main reasons for avoiding metal structural partd is so the
rocket is not conductive in the event of contact with electrical lines.
As for the hazzards of using BBs or hardware for ballast, I don't see
where an alternative is better. Mass is mass, metallic, ceramic, or
otherwise.
Do you have any examples where metal ballast caused damage or injuries
that woukd not have bee. the case with non-metal ballast of the same weight?
David Smith
Nar 78668, TRA 15803
Amateur Extra: W6DPS
On Jan 30, 2017 1:50 PM, "R Dierking" <applerocketry@xxxxxxxxxxx> wrote:
Next time the NAR and TRA safety rules are revised, there should be
something about what kind of nose weight should be used or how about
shouldn’t be used.
Don’t the codes already say something about minimizing the use of metal?
Why add it? There’s no good reason why metal has to be used; there are
other things that would work fine.
And, just to get ahead of the one response that’s going to ask if a rocket
with other types of weight could hurt someone just as bad. Yes, I realize
that. But, again, if you think through the various failure scenarios,
metal (bolts, lead shot, bb’s, what ever…) is a poor choice for nose weight.
What other things could be used? Things that would be even better for
both safety and performance.
Richard Dierking
