This subcooled methane idea, how is it supposed to work?
I thought about it, and pulled some of the physical data, but I'm still not
quite getting it.
Presumably you cool it down so that the vapour pressure is low, so the tank
walls can be thin and light and I ran cpropep-web and looks like you'll get
nearly the same Isp as Kerosene. But the propellant density and impulse
density is unimpressive.
I can see some small wins, like you it helps having the two propellants at
about the same temperature, but no big win. What am I missing?
To be honest, Musk really needs a hydrogen upper stage.
And Musk's other idea of making everything bigger, it would help a bit; but
Falcon 9 is pretty big already; he'd mainly gain on the reduced reentry
shielding due to area/volume relationships.
On 24 December 2015 at 14:42, Findley, Jeff <jeff.findley@xxxxxxxxxxx>
wrote:
On Wednesday, December 23, 2015 3:09 PM Derek Lyons wrote:
Quoted for truth. "Everyone" expected him to stick the first bargelanding. And the second. And the third.
Yet the times he didn't and their predictions were wrong have alreadygone down the memory hole.
We’re skirting very close to “fanboy bashing”, which I’ve seen on enough
websites over the years. “The other side” has called Musk’s Falcon 9 a
“hobby rocket”, criticized the “low performance” of the Merlin engines, and
said that reuse would never happen (because smarter minds than his have not
been able to do it yet, so it must not be possible). So, all of those
predictions have also “gone down the memory hole”.
As Bill correctly points out, there's good reason for healthyskepticism. (Not the least of which is the track
record of a very complicated and "sporty" landing sequence.)
While true, Musk also has a mind for the future. Let’s draw some
parallels with Tesla...
The first Tesla was an extremely impractical car, but you have to start
somewhere (Falcon 1). The second Tesla was a quite impressive car, but
still far too expensive for most people to afford at about $100k (Falcon 9
and Falcon Heavy). Eventually, Musk plans on selling an “affordable” car,
but it requires building the biggest battery factory on the planet before
he can even think about starting production (LOX/methane fully reusable
launch vehicle).
Say what you will about Musk, but he thinks big, and he thinks very long
term.
Jeff
--
Jeffrey Findley
Product Eng
Siemens Industry Sector
Siemens Product Lifecycle Management Software Inc.
2000 Eastman Drive
Milford, OH 45150 United States
Tel. :+1 (513) 576-5606
Fax :+1 (513) 576-2840
jeff.findley@xxxxxxxxxxx <http://jeff.findley@xxxxxxxxxxx%20>
www.siemens.com/plm
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx]
*On Behalf Of *Derek Lyons
*Sent:* Wednesday, December 23, 2015 3:09 PM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Re spacex falcon 9 landing
On Dec 23, 2015 11:44 AM, "William Claybaugh" <wclaybaugh2@xxxxxxxxx>
wrote:
Take care; there is a difference between doubt and >professionalcaution: I'm inclined to the view that >competent engineers, given good
specs, will at least >meet their goals. Thus it seems likely that Falcon 9
will >be easier to refurbish than previous examples >of reusable
hardware. But in addition to being designed >for reuse it was also designed
for very low cost as an >expendable. It is worth considering whether the
total >cost of reuse is going to be lower than the intentional-->and
demonstrated--low cost of expending. That is not >doubt, that is a subject
matter expert thinking carefully >bout the the details.
Just sayin'
Bill
Quoted for truth. "Everyone" expected him to stick the first barge
landing. And the second. And the third. Yet the times he didn't and
their predictions were wrong have already gone down the memory hole.
As Bill correctly points out, there's good reason for healthy skepticism.
(Not the least of which is the track record of a very complicated and
"sporty" landing sequence.)
D.