Air Force Launches Massive, Secret Spy Satellite

On Thu, 25 Nov 2010 10:32:13 -0500, Jeff Findley
wrote:


It will certainly help the economics if they can get the first stage
recovery system on Falcon 9 to work correctly, unlike on the first flight.

True, but SpaceX is approaching this like recovery and re-use is a nice
to have feature for the future. They're still focused on low cost
manufacturing for Falcon 9. Notably the engines really aren't the uber
high ISP engines you'd expect from a typical American launcher. SpaceX
traded lower ISP to get lower cost manufacturing. This appears to be a
good trade. Sure the tanks end up bigger, but tanks and fuel/oxidizer
are far cheaper than uber expensive high ISP engines.

There's a point where you cross over toward diminishing returns
though. Ginormous tanks can be a ground-handling nightmare. The SRBs
remember are the size they are so they'd fit on railway cars. Start
building huge tankage and you need lots of expensive infrastructure
(i.e., NASA's barges or the Delta Clipper) to handle and transport it.

Brian

On 11/26/2010 3:43 PM, Brian Thorn wrote:

There's a point where you cross over toward diminishing returns
though. Ginormous tanks can be a ground-handling nightmare. The SRBs
remember are the size they are so they'd fit on railway cars. Start
building huge tankage and you need lots of expensive infrastructure
(i.e., NASA's barges or the Delta Clipper) to handle and transport it.

The big problem is that in the absence of some future need for manned
capability to orbit beyond ISS, Atlas V, Delta IV, and Falcon 9 have to
fight with Proton, Sealaunch, and Ariane V to try to keep financially
afloat in a world where around 95% of space launches to orbit (outside
of military reconsats) involve commercial comsats, commercial imaging
sats, or navsats.
You can only cut that pie into so narrow of wedges before it becomes too
unprofitable for most companies to survive due to the paucity of world
yearly launch needs.
The cost of maintaining the assembly and launch infrastructure for the
vehicles will in short order become greater than any commercial profits
realized by their yearly launch rate.
At that point, the only purpose of their existence will be either
national pride or as public works programs.

Pat

In article , bthorn64
@suddenlink.net says...

There's a point where you cross over toward diminishing returns
though. Ginormous tanks can be a ground-handling nightmare. The SRBs
remember are the size they are so they'd fit on railway cars. Start
building huge tankage and you need lots of expensive infrastructure
(i.e., NASA's barges or the Delta Clipper) to handle and transport it.

True, so you don't do that when you need to grow bigger. Instead, you
go for parallel first stages like Delta IV. That's the current plan for
the heavy version of Falcon 9.

The other thing that helps is using LOX/kerosene engines for your first
stage(s) instead of LOX/hydrogen. SpaceX has also made the right choice
in this area as well. As long as you're not going for uber high ISP,
you might as well choose a very dense fuel to help minimize the tank
size for your lower ISP engines.

Jeff
--
42

In sci.space.policy message
, Fri, 26 Nov 2010 17:43:58, Brian Thorn
posted:

There's a point where you cross over toward diminishing returns
though. Ginormous tanks can be a ground-handling nightmare. The SRBs
remember are the size they are so they'd fit on railway cars. Start
building huge tankage and you need lots of expensive infrastructure
(i.e., NASA's barges or the Delta Clipper) to handle and transport it.


Only if you construct them in the wrong place, to spread the pork.

The larger USN ships are, I believe, invariably built near seaports,
rather than trucked in from somewhere like Utah.

But ginormous rocket tanks are comparatively light; fly them in under
Zeppelins.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms and links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

On 11/30/2010 12:53 PM, Dr J R Stockton wrote:

But ginormous rocket tanks are comparatively light; fly them in under
Zeppelins.

Fill them with hydrogen, and fly them in _as_ Zeppelins. ;-)
I'm joking, but later in its career Atlas boosters were filled with
helium instead of the original nitrogen for pressurization during
transport, and it did markedly decrease their weight.
On something as big and lightweight as a Shuttle ET, filling it with
gaseous hydrogen or helium for transport could make it significantly
lighter for moving it around.

Pat