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

On Feb 20, 8:35 pm, kT <cos...@xxxxxxxxxxxx> wrote:
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.

Isn't that expense the primary reason for the ablative alternative.
How difficult would it be to refit the engine with a new nozzle?

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?

What it lacks in efficiency and weight it more than makes up in
thrust, the cost of additional propellant is trivial. Why the
difference in ignition difficulty?

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

You'll easily make orbit with an SSME.

--
Get A Free Orbiter Space Flight Simulator :http://orbit.medphys.ucl.ac.uk/orbit.html- Hide quoted text -

- Show quoted text -

You might well be right, though I would have hoped that an RLV could
be built on the cheap. In any case, a frequent flyer RLV should be
NASA's first and primary goal.

.

Relevant Pages

  • Re: Google Cindy Sheehan (was: Re: Peace Mom)
    ... >>>engines are the highest performance, ... It has nothing whatsoever to do with 1970's technology or 2010 ... An expanding nozzle or better ... SSME could be used with a aerospike since there is no such supply of turbine ...
    (misc.writing)
  • 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. ...
    (misc.writing)
  • Re: Google Cindy Sheehan (was: Re: Peace Mom)
    ... In fact, even today, its technology readiness is ... the engine performance could be minimized. ... > gas-generator cycle and the altitude-compensated SSME proposals I've ... > seen mentioned use a passive plug nozzle or an expanding bell. ...
    (misc.writing)
  • Re: SRB-Based EELV Launcher Article
    ... That nozzle is my biggest bitch, and the RS-68 is heavy as hell, but at ... RS-68, and then even if they had to blow it off the back of the tankage, ... It has already been demonstrated with the SSME. ... Demonstrator, RS-83, Cobra, whatever ... ...
    (sci.space.policy)
  • Re: Is Crew Launch Vehicle Too Big?
    ... Unless you've already paid for the engines. ... engine will be cheaper than updating SSME for air-start (changes ... And by the way, J-2S has never flown, the original J-2 had ... But they'll need SSME for the Heavy Lifter anyway, ...
    (sci.space.policy)