NASA's new focus plan revealed

"Pat Flannery" wrote in message
...
On 2/24/2010 7:30 AM, Jeff Findley wrote:

It's likely to be "more robust" simply becaue it is a Russian design.
The
"more complex" part, I'm not so sure about. If you have an engine like
the
RD-180 which is a staged combustion engine which is regeneratively
cooled,
there is no fundamental reason that it can't be classified as reusable.

So maybe you can make a expendable one that's simpler and cheaper, sort
of
the kerosene/LOX equivalent of the RS-68.
Unless they intend to resurrect the F-1 in some modified form.

True you often can make an expendable version of an engine which is
simplified in some ways, but I have a feeling that what you're really
doing
when making an expendable version is tweaking the design so it's easier
to
manufacture. If that results in some trade-offs which would otherwise
reduce "reusability", then that trade would likely be made. But there is
a
point where shaving margins off an engine makes it less reliable, even
for a
single use.

I could picture them going with a simple non-staged combustion engine and
ablative nozzle that lowers isp in exchange for lower production costs.

And much lower ISP. The RS-68's lower performance (compared to the SSME's)
was the main reason that the Ares V kept getting bigger and bigger. In the
end, I think it was a false economy to choose the "cheaper" RS-68 for Ares V
considering how it made the rest of the vehicle bigger (10m diameter core),
more complicated (SRB's lengthened to their limit), and more expensive. The
expensive part impacted the ground infrastructure nearly everywhere to
handle the much larger diameter and much heavier SRB's. When you start
talking about the concrete foundation of your launch pads not being strong
enough to handle the weight of the new launch vehicle, you're getting into
massively expensive upgrades.

Jeff
--
"Take heart amid the deepening gloom
that your dog is finally getting enough cheese" - Deteriorata - National
Lampoon

OM wrote:
On Fri, 26 Feb 2010 11:26:27 -0500, "Jeff Findley"
wrote:

In the end, I think it was a false economy to choose the "cheaper" RS-68 for Ares V

...I actually chalk it up not so much as an effort to reduce costs,
but to throw the Former Soviet Empire a bone in the form of a
propaganda move that said "Hey, here's proof we're no longer going to
nuke one another! We're using their engines and paying them for the
damn things!"

You're confusing the RS-68 (a US engine, used in the Ares V) with the
RD-180 (a Russian engine, used in the Atlas V).