The presence of the other light alkanes also makes LNG easier to light than
methane.
-R
On Wed, Feb 14, 2018 at 6:41 PM Rand Simberg <simberg@xxxxxxxxxxxxxxx>
wrote:
This is why BO is using LNG for propellant instead of pure methane. They
anticipate their propellant costs dominating total launch costs...
On 2018-02-14 18:27, Henry Vanderbilt wrote:
On 2/14/2018 6:26 PM, Henry Spencer wrote:
On Wed, 14 Feb 2018, Randall Clague wrote:
When we first started with methane, we put some effort into using
liquid nitrogen to liquefy natural gas from our municipal supply. We
found that natural gas gets tarry as you cool it, and that it's easy
to freeze it unintentionally. When we froze it, we were done for the
day.
I wonder if that is at least partly due to impurities, both
hydrocarbon (unsaturated hydrocarbons reportedly get *very* viscous
down at the bottom of their liquid ranges) and non-hydrocarbon
(notably the sulfur-compound "stenchant" put into municipal gas so you
can smell it).
That is to say, it might not be an issue for relatively pure propane.
But it's certainly something that would need checking before you
relied on it. (And cheaper propane often has some propylene in it...)
Indeed. What PG&E delivered to the local gas meter was a long way
from pure CH4. Lots of heavier fractions in your average consumer
natgas.
The lesson there is, if you want to be in the launch business, don't
try to get there by learning the gas refining business first.
If you're buying enough propane (or whatever) to run a serious rocket
development program, chances are you'll be able to find someone to
bulk deliver it at whatever purity grade you need at a tolerable
price.
And by the time you're buying to support an active high-rate flight
program, the price should be downright reasonable with a bit of
haggling.
Henry V