I’d always assumed N2O as simplest and thus likely cheapest.
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.
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.
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.
Bill
On Sat, Mar 3, 2018 at 4:06 PM Henry Vanderbilt <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
