LITVC is easier than one might think, and Nitrous works really, really well
(approaching N2O4 in effective ISP as measured by this subscale test using
load cells to measure side force generated to calibrate how much N2O needs
to be injected to achieve a given thrust vector angle)
https://www.youtube.com/watch?v=8osJpwXAJs8
On Sat, Mar 3, 2018 at 6:10 PM, William Claybaugh <wclaybaugh2@xxxxxxxxx>
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”.
Bill
On Sat, Mar 3, 2018 at 6:11 PM Henry Vanderbilt <
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 Vanderbiltgimballed
<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
>> solids is such that I'd seriously consider it - I'd use anmotor
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
>> burns out, with steering done by a proportional four-waydiverter.
>> There's no excuse for that causing leakage on the pad; thediverter
>> valve almost by definition can't be leak-tight but it does meanyou
>> only need one leak-tight valve upstream of the diverter.that
>>
>> 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
> might be a worthwhile and achievable enhancement to the currentplus a
> 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,
> relatively benign albeit low-performance TVC fluid, to develop anperoxide?)
> initial flight demonstrator. Save aqueous HAN (or maybe
> TV-fluid and shooting for 100 km for a subsequent iteration.the
Duh! For a KISS liquid TVC demo, what do you think of nitrous for
TVC fluid?
Henry
