On 3/3/2018 7:10 PM, William Claybaugh wrote:
Henry:
Per Keynes, “In the long run we are all dead”:
There is ultimately no point to solving problems that have already been solved. Amateurs....
Half a century ago I estimated that about a century from then “amateurs” would be able to build a nuclear explosive. I hold by that estimate. “Amateur” just means “late to the game”.
On Sat, Mar 3, 2018 at 6:11 PM Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>> wrote:
On 3/3/2018 4:30 PM, William Claybaugh wrote:
> I’d always assumed N2O as simplest and thus likely cheapest.
There's certainly already an N2O "installed based" of suppliers,
plumbing hardware, and experience in the amateur/student community,
which would indeed tend to save all sorts of time & money over starting
utterly from scratch.
On a tangent, it occurs to me that a nitrous hybrid might be the
simplest initial testbed for such a liquid TVC system. Some additional
plumbing and controls, but no new consumables.
> However, given that rolleron’s and canards have been proven on high
> power rockets and that even high end amateur rockets only need
guidance
> in the atmosphere, I’d start there.
The long-term goal here, I think, is to eventually expand the
amateur/student high-end envelope beyond the effective atmosphere, and
thus the guidance techniques that depend on atmosphere.
And if I'm not mistaken (I'd certainly expect correction here if I am)
the techniques you cite aren't very effective at low airspeeds, and thus
force amateurs into the high-thrust/short-burn end of the design space,
in order to achieve enough airspeed for aerosurface effectiveness before
they're off a practical-length rail.
It could be interesting, I would think, to open up the
lower-thrust/longer-burn end of the amateur design space. My
sans-numeric-analysis impression is that going supersonic right near the
ground has to be eating up a lot of energy that would be better spent
performance-wise if applied a bit later on when the air's thinner.
> If—and only if—some fool was throwing around eight figures for a
> “student-built” copy of what the Japanese have already done (that
is, a
> cubesat launcher) would I worry about exoatmospheric pointing.
At this point, there are people with eight-figure budgets working on
smallsat launchers, but they're not students or amateurs. (At least not
any more.)
Again, the idea here is to build amateur/student community capabilities
incrementally toward the point where the time and cost of such a thing
have dropped an OofM or two. It won't happen overnight, no. One step
at a time.
> As between LITVC and moveable nozzles, I’d probably go for the latter
> since how to do it is understood: expensive, but likely less
costly to
> have one of the players teach you how to do it then to reinvent
LITVC,
> which is largely lost knowledge.
I'm not sure any likely student or amateur group would be able to afford
what AJR or Orbital-ATK would charge to pass along their
gimballed-solid-nozzle expertise. Assuming it's practically sharable at
all, given the prominent defense applications.
LITVC strikes me as much more amenable to an amateur/student low-cost
cut-and-try development approach. And if it's now lost knowledge, all
the more fun rediscovering and mastering it - but that's a
personal-taste thing...
Henry
> On Sat, Mar 3, 2018 at 4:06 PM Henry Vanderbilt
> <hvanderbilt@xxxxxxxxxxxxxx <mailto:hvanderbilt@xxxxxxxxxxxxxx>
<mailto:hvanderbilt@xxxxxxxxxxxxxx
<mailto:hvanderbilt@xxxxxxxxxxxxxx>>> wrote:
>
> On 3/3/2018 3:42 PM, Henry Vanderbilt wrote:
> > On 3/3/2018 3:20 PM, John Schilling wrote:
> >> If I were doing it today - and the cost and complexity of
gimballed
> >> solids is such that I'd seriously consider it - I'd use an
> aqueous HAN
> >> solution as the fluid. Only about half the free oxygen
of NTO,
> but at
> >> least an order of magnitude less hassle on the pad. And yes,
> run the
> >> fluid at constant rate calibrated to run out right after
the motor
> >> burns out, with steering done by a proportional four-way
diverter.
> >> There's no excuse for that causing leakage on the pad;
the diverter
> >> valve almost by definition can't be leak-tight but it
does mean you
> >> only need one leak-tight valve upstream of the diverter.
> >>
> >> Well, OK, one series-redundant valve train. And I'll even
> consider a
> >> pyrovalve for this application, since we're going solid
anyway.
> >>
> >
> > And, circling right back to where we started (the question of
> what sort
> > of high-performance solids might be doable by a serious
> university team)
> > simplified liquid-injection TVC actually sounds like
something that
> > might be a worthwhile and achievable enhancement to the
current
> > non-professional state of the art.
> >
> > I'd be tempted to gain experience and work out the bugs on a
> > medium-performance first pass, mind - an off-the-shelf
solid, plus a
> > relatively benign albeit low-performance TVC fluid, to
develop an
> > initial flight demonstrator. Save aqueous HAN (or maybe
peroxide?)
> > TV-fluid and shooting for 100 km for a subsequent iteration.
>
> Duh! For a KISS liquid TVC demo, what do you think of
nitrous for the
> TVC fluid?
>
> Henry
>
