[AR] Amateur Liquid TVC (was: Regarding Univerity solid rockets for cube-sat launch to orbit)

  • From: Henry Vanderbilt <hvanderbilt@xxxxxxxxxxxxxx>
  • To: arocket@xxxxxxxxxxxxx
  • Date: Sat, 3 Mar 2018 18:10:48 -0700

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>> 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


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