Was that an AF standard or a NASA one? AF, I dimly recall.
Henry
On 2/28/2018 6:55 PM, Doug Jones (Redacted sender randome for DMARC) wrote:
I was on the committee (in 2005, I think it was) that set the (several) standards for rocket-grade methane/LNG. I argued for and got a grade that was (paraphrasing) low sulfur, 99% hydrocarbons under C4. You can tolerate some C2 and C3 hydrocarbons, but nitrogen is death on performance (helium doesn't liquefy, of course). I felt that trying to specify the exact composition was a bad idea.
Citing the hassles of getting RP-1, we made sure that there was the broadest possible spec for RG LNG. I lost all that correspondence with my XCOR account, alas, so damifIknow what the current status is.
On 2018-02-28 10:45 AM, Henry Vanderbilt wrote:
On 2/28/2018 8:58 AM, Perry E. Metzger wrote:
On Sun, 25 Feb 2018 20:34:40 -0700 Henry Vanderbilt
<hvanderbilt@xxxxxxxxxxxxxx> wrote:
FWIW, plain-jane US market natgas has mostly been running between
$2.50 and $3 per million btu's (MMBtu) the last few years. There's
~12 gallons of LNG per MMBtu, at ~3.5lb/gallon, so that's 6-7 cents
a pound for the raw natgas feedstock.
Chances are there'll be markups for vehicle grade (high CH4, low
sulfur, from selected wells) natgas, and for liquefaction. But
there's till quite a bit of room for rocket LNG to come in
significantly cheaper than highly refined kero.
If you're liquefying the gas anyway, I would presume that purifying
the mixture by fractional condensation at the same time would be
practical?
I can't speak to details of the liquefaction and refining-to-pure-CH4 processes, beyond saying that a minute's googling indicates they're typically separate processes conducted on separate equipment.
My initial assumption would be that's for sound economic reasons, and my first guess would be that R&Ding a new combined process would be a major distraction from flying rockets, and likely a money-loser as well.
Because regardless of the exact process, if you're buying the result by the railroad tank-car full, chances are you'll have no trouble finding an existing refiner happy to set up to do all that for you. And if, at that sort of purchase volume, your fuel buyer can't get prices down to less than it'd cost you to develop and set up your own liquefaction/fractionation plant, you need a new fuel buyer.
Mind, it's not clear that fractionation to pure LCH4 is even useful. Simply using liquefied "vehicle grade" natgas - as mentioned, from selected wells that naturally have high CH4 and low sulfur fractions - seems to work just fine. If it's clean-burning enough not to gunk up an automotive piston engine, it seems to be fine for rocket motors too.
Admittedly in a limited number of tests so far. But I'd take Blue Origin's plans to use natgas rather than refined CH4 as a strong hint - they tend to do their homework quite thoroughly.
Henry
