hpr staging - got a good explaination?
Des Bromilow
to show the coupling of a booster, to sustainer in composite staging?
I see lots of people mention carbon shafts etc, but I guess you all know
what you're talking about, and assume I do as well... Sorry, I must have
missed that class.
After testing my G-switch and timer yesterday, I'll be moving into
electronic staging over the next few months.
Composite to BP,
Water to BP,
and then Composite to composite
and maybe hybrid to composite.
Thanks in advance
Des
--
Des Bromilow
(mad rocket scientist)
****Please remove the German anti-spam device before replying.(V2)
John H. Cato, Jr.
Des Bromilow
>I see lots of people mention carbon shafts etc, but I guess you all know
>what you're talking about, and assume I do as well... Sorry, I must have
>missed that class.
Des, what the 'deal' is...
... is that the 'traditional' approach (read: "scale up the Estes thing of
simply using a tubing coupler (that Estes even calls a 'stage coupler') and
do the same thing on HPR scalel") will simply not work. That weak
separation plane where the two stages join will simply generate
considerable forces - and there isn't a staging coupler made that could
handle it (at this scale).
.... soooo....
... the alternative is to *lengthen* this 'joining plane' (thereby
stiffening it up some (quite a bit, actually)). Coupler tubes won't work
here - but providing some 'guide rods' will. The concept here is to
provide some 'guide tubes' in the upper stage and 'guide rods' in the lower
(inter)stage that mate to it with a smooth and somewhat loose (say 1/16"
slip fit). At staging, the booster section simply slides away (and
provides a little 'linear guidance' upon doing so). It is the *length* of
this engagement that provides the (considerable) stiffness to the 'joint'
where the two stages join -- and that is critical for the vehicle to behave
as 'one piece' under initial boost. This is simply impossible to provide
(to the degree needed) with something like a 'coupler tube'.
Next question is what to use for these 'guide rods'. Metal sounds good,
but if it ever gets bent (like on touchdown), odds are one would never get
them straight enough to 're-mate' with the guide tubes. Enter carbon
fiber. According to one carbon arrow-shaft salesman, "They're either
straight or they're broken." Sounds good to me. Thus, most everybody uses
these carbon arrowshafts for their guide rods. They can take a decent
amount of abuse (on touchdown) and still not worry you if they'll ever
re-fit the sustainer guide rods.
For something like a 4 or 5" booster to a 3 to 4" sustainer, generally 12"
engagement of 3 or 4 1/4" arrowshafts -- mating to 5/16" tubing in the
sustainer will work just fine. If you're going to 7" to 5" stuff, I'd
begin to question if 1/4" arrowshafting is sufficient -- and there are some
sources that are bigger (getting up to 1/2"dia), which would be better at
this scale. Into The Wind (kite place) has fiberglass shafting up to this
size (and I think I've heard of a place or two that has carbon that size,
too).
Rule of thumb for engagement is about 3 to 4 sustainer diameters for
length. i.e. 3" upper stage should use 9 - 12" of 'guide rod' engagement.
That's the gist of it.
-- john.
RayDunakin
show the coupling of a booster, to sustainer in composite staging? >>
Here's one way of doing it. I've used this method on rockets of various sizes,
up to a 4" diameter J-to-J powered rocket:
http://albums.photopoint.com/j/AlbumIndex?u=743031&a=12969787