Yeah, I'd forgotten about the environmental restrictions on Freon, which
probably makes that a non-starter. I still think there would be value
in starting with a fluid with about the physical properties of nitrous
but no reactivity, and then going to N2O. Provided such a fluid could
be found that doesn't come with its own unique hassles. Similarly, if
the goal is a HAN-based system, water or a non-reactive salt solution
could be a good place to start.
John Schilling
john.schilling@xxxxxxxxxxxxxx
(661) 718-0955
On 3/3/2018 4:16 PM, William Claybaugh wrote:
John:
I think I know the report you are referencing.
I agree that nitrous is far more dangerous than commonly understood, but not for less than about 6 inch (15 cm) diameter rockets, or LITVC tanks.
If one wants low cost, then multiple development efforts are a mistake (this was SpaceX s error on Merlin, albeit forced by funding constraints); proving a system w/ Freon—which is largely banned from release into the environment—and then going to N2O and then to HAN is likely a mistake compared to starting w/ the solution w/ which you want to arrive.
Bill
On Sat, Mar 3, 2018 at 4:58 PM John Schilling <john.schilling@xxxxxxxxxxxxxx <mailto:john.schilling@xxxxxxxxxxxxxx>> wrote:
On 3/3/2018 3:05 PM, Henry Vanderbilt wrote:
On 3/3/2018 3:42 PM, Henry Vanderbilt wrote:Nitrous should work, but I'm looking at an old DTIC report
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
<https://urldefense.proofpoint.com/v2/url?u=http-3A__www.dtic.mil_dtic_tr_fulltext_u2_268731.pdf&d=DwMFaQ&c=clK7kQUTWtAVEOVIgvi0NU5BOUHhpN0H8p7CSfnc_gI&r=rPTfWqtJdrL0Ber-yr0E_hSjRXuvJH6ZmQx03u8-2as&m=wL9BrTzzfQKxLzHLKhnvDgi7CiaXVEY1qheOYHbxDOY&s=GGr0b0xuDjpKCCAvhSryDfM10wuWfOBWhrEXaMzF8A0&e=>
that got decent results from Freon. Looks like their application
was for the old Subroc system, whic as the name implies was meant
to be used aboard submarines and so wanted the safest possible
liquids.
So, Mark I amateur system uses Freon, and if/when you need the
extra performance you start testing a Mark II using N2O.
Carefully, because it is an energetic oxidizer even if nominally
benign at STP. If you get that working safely and reliably, you
can think about things like HAN.
John Schilling
john.schilling@xxxxxxxxxxxxxx <mailto:john.schilling@xxxxxxxxxxxxxx>
(661) 718-0955
