Re: Vision of the three Rs: Regular, Reliable and Reusable

Totorkon wrote:
On Feb 20, 7:29 pm, "kT" <cos...@xxxxxxxxxxxx> wrote:
On Feb 20, 9:20 pm, "Totorkon" <aertr...@xxxxxxxxx> wrote:





On Feb 20, 6:52 pm, "kT" <cos...@xxxxxxxxxxxx> wrote:
On Feb 20, 8:23 pm, "Totorkon" <aertr...@xxxxxxxxx> wrote:
On Feb 20, 4:26 am, Fred J. McCall <fmcc...@xxxxxxxxxxxxx> wrote:
Ian Woollard <ian.wooll...@xxxxxxxxx> wrote:
:Fred J. McCall wrote:
:> Would it really? We don't know that with any certainty.
:
:Beyond a certain point, do we know that any space activities are worth it?
No, we don't. That's rather the point...
--
"Some people get lost in thought because it's such unfamiliar
territory."
NASA runs on a current budget of a bit over 16 billion per year. The
stipulation is that a reusable launch system, of say twenty tons,
could reduce the cost to orbit by a factor of ten.
I can get a (roughly) 20 ton rocket into orbit with a single SSME,
with a few thousand pounds of fuel to spare. It's a simple matter of
placing the SSME into the nose cone carrier, and returning it to
Earth. That should at least allow us to get enough experience and hard
numbers to come up with something better.-
The RS68 has nearly twice the thrust and costs about a seventh as much
as the SSME RS25. While not as efficient, wouldn't it be better to
base an RLV on its $14M price tag?
It also weighs twice as much as an SSME. It's a hard starter too. Did
you forget that it isn't reusable? That's why the Delta IV Medium is a
two stage launch vehicle. If you want to fly the RS-68, fly the Delta
IV Medium.

When you launch an SSME in SSTO configuration, you are not throwing
the engine away. It's not expendable, it's reusable, get it?- Hide quoted text -

- Show quoted text -

I've read that the SSME must be overhauled after twenty minutes
operation.

So what. We've got 15 of them. That's 45 flights right there. What kind of spacecraft do you think you can build with 45 cryogenic tanks?

My assumption is that a reusable engine could be derived
from the RS68, as the only part that isn't inherently reusable is the
ablative coated nozzel.

All hydrogen engines are by definition reusable, but the nozzle is the most expensive and time consuming to fabricate of all of the parts of these kinds of engines. NASA has been dragging its feet for years on the necessary upgrades like the channel wall nozzle and electric hydraulics.

I may be mistaken, but it does seem wise to
work with a design that has only 10% the parts count of the RS25.

It makes sense to work with the engines that we have. We have SSMEs. Lots of them. Plus lots of spare parts, and lots of people qualified to launch them and rebuild them. It's just plain insane to retire them.

The RS-68 is a non starter. It's far too heavy, far too inefficient, and far to dangerous to ignite. That's why NASA intends to throw them away five at a time. What don't you understand about the irrationality of it?

You won't even make it to Africa with an RS-68.

You'll easily make orbit with an SSME.

--
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http://orbit.medphys.ucl.ac.uk/orbit.html
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Relevant Pages

  • Re: GRIFFINS DRIVE FOR SHUTTLE-DERIVED
    ... >> launch vehicle for manned CEV ... Payload would be atop the ET. ... >> outperform the comparable RS-68 concepts. ... SSME design. ...
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  • Re: GRIFFINS DRIVE FOR SHUTTLE-DERIVED
    ... The info I have says that the SSME vacuum ISP ... If the RS-68 was put into upper stage use ... RS-68 cost has probably doubled ... out of them because they're relatively low pressure engines. ...
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  • Re: Google Cindy Sheehan (was: Re: Peace Mom)
    ... >I heard suggestions of it, the staged-combustion aerospike, but I haven't ... the SSME had stability problems, but both the J-2 and J-2S had some, ... and the less said about the LOX/kerosene and N2O4/hydrazine engines, ... >>>a 1.5 stage vehicle. ...
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  • Re: GRIFFINS DRIVE FOR SHUTTLE-DERIVED
    ... The RS-68 gives the ground lever thrust 650 klb. ... Assume three RS-68:s to compensate for the 33 s lower vacuum isp ... Assume the SSME recover pods weight is 1 ton each. ... shortage in the "ET" stage to make the lunar injection stage larger ...
    (sci.space.policy)
  • Re: Vision of the three Rs: Regular, Reliable and Reusable
    ... I can get a 20 ton rocket into orbit with a single SSME, ... two stage launch vehicle. ... the cost of additional propellant is trivial. ...
    (sci.space.policy)
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