Re: Ares vs DIRECT

Einar wrote:
On Dec 9, 7:58 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
On Dec 9, 6:56 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
On Dec 8, 8:11 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
On Dec 8, 7:29 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
On Dec 8, 5:39 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
On Dec 8, 5:13 pm, kT <cos...@xxxxxxxxxxxx> wrote:
Einar wrote:
The idea you people are pushing appears to the standpoint of a pure
know very litle to be very sensible, if it´s really true that all this
extant infrastructure can be reused. Building a new one, and really
two new ones must alone cost a bundle and then some.
It uses SRBs, and it uses engines that are already in use on launchers
that already exist and have been flying for some time now. That makes
the Direct proposals distinctly irrational.
<material not relevant to the point I´m discussing snipped>
Eeer...now I´m not an engineer or anything engineer related at all,
but even so that sounds bit weird. I would have expected the exact
opposite argument, i.e. that flying with existing hardware is a good
thing, as after all it´s tried and tested, which in other areas of
endevour, say involving earoplanes, is seen as a good thing.
If we follow your logic to its inevitable conclusion, we'd be flying the
shuttle and the EELVs. Hey, we are flying the shuttle and the EELVs!
That is an overstatement. What people do is that they create a new
veicle, which contains a number of old systems, yet also contains
enough new things to be an advance on the previous veicle. This kind
of incremental development was very common within the aeroindustry
during the interwar years, i.e. between WW1 and WW2.
The rule of a thumb being, the less new stuff you are using when
developing a new veicle of any kind, whicever what kind, it costs less
money to develope and the risks of costs overrun are minimized. Now,
this is a rule of a thumb I have read about from quite a varied
sources, to name an example the US army was once developing a super
duper heavy tank in cooperation with what was then called V-Germany.
After series of cost overruns, the whole thing was cancelled by the US
Congress and the M1 Abrahams developed instead, as a less complex and
less risky alternative, using fewer new expensive to develope new
technologies.
The ET (more precisely, the foam insulation) and the SRBs are the bad
parts of the shuttle, those are the parts we want to get rid of.
Direct proposes not only to get rid of them, but to build an entirely
new heavy lift launcher that uses them. It's Ares I and V regurgitated.
A very logical move, as it sounds to me knowing mostly about how the
aeroindustry used to do things, during older times. Incremental
development, meant f.e. that a new airframe often used systems and
technologies from the previous airframe. Then, incremental development
continued, next time over some of the systems were replased yet the
same airframe kept.
Systems of this size and complexity cannot be incrementally engineered,
except for the easy stuff, like the avionics and engines, for instance.
That was what the shuttle upgrade program was all about. Direct is just
more of the same only different, and we have plenty of the same already.
What has size anything to do with it? Complexity I think actually is
an argument for incremental change, as it´s very complex and expensive
to fully engineer a wholly new very complex systems from nothing, not
using any part of the old.
Greater complexity means the risks in designing a wholly new system
are even greater, because the numbers of unknowns are larger.
In other words, you want me to debate applied mathematics, engineering
and physics with the confessed uninformed.
I suggest something similar. Direct essentially appears to me to be
comparable to making a new airframe, while using as many of the old
systems as practical. A comparable philosophy. Then, gradually the old
systems can be replased over time. Then perhaps, some day, another
veicle will be built using many of those systems and then so on.
The Direct ET is an entirely new system, there is nothing old about it.
We have a vehicle that flying the RS-68 just fine - the Delta IV Medium.
A smaller veicle, I understand. Moreoever, it doesn´t utilize the
engineering facilities I´m sure that are a political necessity to
continue to use, if political support is to be found for the program.
Hence my design : the Delta V. Size really doesn't matter, because we
can ill afford another Apollo style moon program, and people are finally
realizing what we've knows all along, even the VSE destination is wrong.
It's the liquids that count. Liquid fuels, get it? Cryogenic fuels, ok?
Personally have nothing against LOX and liquid hydrogen combinations.
Different fuels offer different combinations of compromizes in the
design.
Remember, we are also dealing here with the precense of pork/barrel.
That´s part of the operational circumstances.
No, physics is the operational circumstance.
The proposal may be the least bad thing it´s possible to do with the
reources of Nasa given the current political reality within the USA.
If it involves inline SRBs, and upper stages that don't reach orbit,
it's the most bad thing.
So I must respectfully disagree.
Thus, the problem remains. The only part of the shuttle worth saving,
the premier component of the shuttles, with hundreds of equivalent
engine flights remaining, are the space shuttle main engines - SSMEs.
http://webpages.charter.net/tsiolkovsky/proposal/IPO.doc
You could try to educate yourself.
Well, more knowledgeable people about engineering, feel free to
comment.
There isn't much to comment about on these kinds of papers I write.
This is the point at which these things become self evident.
All truth passes through three stages. First, it is ridiculed. Second,
it is violently opposed. Third, it is accepted as being self-evident.
Arthur Schopenhauer (1788 - 1860)
Actually, the third stage is grudging acceptance, only over time does
an accepted theory come to be seen to be self evidently true as
additional support continues to be found.
Today plate tectonics are very much generally accepted, yet it took a
long time of painstaking research to find all the evidence which today
makes that theory appear self evidently true.
So in your world, the upper stages don't reach orbit, right?
In my world, even the first stages reach orbit.
Isn´t that a rather more difficul task, i.e. to design a single stage
capable of going the whole way to orbit?
I think of it more as a challenge. The harder part is designing them to
be immediately useful once they get to orbit. Getting to orbit is just a
six minute flight, and from then until apogee it's an entirely different
regime.
My understanding has so far been that nossle efficiency is a problem,
for something which is supposed to operate well enough right from
surface over to space. To many compromizes. You get a nossle which is
neither very efficient, where the athmosphere is thick nor very
efficient where the athmosphere is very thin.
There are no physical barriers to SSTO flight. We can do it now in
friction stir welded aluminum lithium alloys, and we could have done it
back in the sixties. Like I said, you could take the time to educate
yourself on the basics :
http://en.wikipedia.org/wiki/Single-stage-to-orbit
With a multistage rocker, each stage can be better optimized, thus
more efficient.
And thus, expendable, and thus, the problem remains. Right now, SSTO
engines are not a problem, we have them ready to go - the SSMEs.
The problem more precisely is the foam insulation on the tanks.
I think it´s better to go the incremental route of improvement.
That SSTO may be possible, does not mean that it´s desierable to
attempt it now. To put it simply, a SSTO is to expensive and risky a
project at this time.
If you had actually read the proposal through, and read my links, and
the links that are out there, you will see that SSTO is a trivial
exercise with the SSME. The SSME is as good as it gets.

The risk of expensive failure is to great.
For simple SSTO? If you fail that bad, you need to go back and
completely rethink your analytics. Engine failures don't count.

We expect engine failures, the challenge is in the tank and nosecone.

The whole project is incremental, every launch is a new design.

About the foam insulation. What´s the problem? I know it´s been a
hasard for the shuttle, but when you have got everything stacked on
top of each other falling foam has nothing to harm on the way down.
The foam is friable in orbit. It's a challenge, do away with the foam
entirely. Clearly any fill insulation can be left on the ground. The
challenge again is the analytical model for tank and fuel heating during
the six minute boost phase. These analytical models are fundamental to
all space flight, if we can't get a handle on this we should give it up.

Sure, these engines appear to be nice engines.

http://en.wikipedia.org/wiki/SSME

Mind you, I have followed past failures in achieving SSTO with
interest, so I know it´s very far from being a trivial task.

Which explains why we've had structural efficiencies necessary for SSTO since the early 60's. The SCORE mission was clearly a stage and a half success, as is every successful shuttle flight. We're basically there, especially now that they claim they want to retire the SSMEs. The only thing preventing us from doing this has been the use of the SSMEs in the space shuttle system, once that is retired there is simply NO EXCUSE whatsoever for not doing this. Anybody who claims retiring the SSMEs is a good thing, is clearly not familiar with the value of space flight.

The share challenge of maintaining a sufficiently low structural
weight, yet at the same time achieve a sufficiently sturdy veicle,
which at the same time is able to carry an useful payload into LEO;
has so far proved to challenging.

Which explains why several obsolete vehicles have already acheived it.

I have not so far seen anything likely to do any better, for any near
future scenario. Now, what was the proposal you were talking about
again?

SSME on a structurally sufficient stage. As my COTS proposal clearly indicates, it's a trivial exercise in mass performance closure. However, just to placate the cranky lazy people like you, I've already pointed out that *ANY* booster enhancement of the SSTO core stage will easily close the mass performance solution. So your final excuse is nullified.

The trick is to characterize the structural and thermal behavior of the bare uninsulated stage on its atmospherically aggressive ascent flight profile under continuous cryogenic acceleration. As I have clearly pointed out, this behavior defines modern space flight. If we can't do this one thing, then we will never become a true space faring nation.

Ares I epitomizes this insanity, discarding a high performance upper stage and engine when it is 99.9 percent of the way to orbit. It's nuts.
.

Relevant Pages

  • Re: Ares vs DIRECT
    ... we are flying the shuttle and the EELVs! ... except for the easy stuff, like the avionics and engines, for instance. ... If it involves inline SRBs, and upper stages that don't reach orbit, ... There are no physical barriers to SSTO flight. ...
    (sci.space.policy)
  • Re: Ares vs DIRECT
    ... we are flying the shuttle and the EELVs! ... except for the easy stuff, like the avionics and engines, for instance. ... If it involves inline SRBs, and upper stages that don't reach orbit, ... There are no physical barriers to SSTO flight. ...
    (sci.space.policy)
  • Re: Ares vs DIRECT
    ... we are flying the shuttle and the EELVs! ... except for the easy stuff, like the avionics and engines, for instance. ... If it involves inline SRBs, and upper stages that don't reach orbit, ... There are no physical barriers to SSTO flight. ...
    (sci.space.policy)
  • Re: Ares vs DIRECT
    ... we are flying the shuttle and the EELVs! ... except for the easy stuff, like the avionics and engines, for instance. ... If it involves inline SRBs, and upper stages that don't reach orbit, ... There are no physical barriers to SSTO flight. ...
    (sci.space.policy)
  • Re: Er, Uh, Kinda important
    ... >> you think happens if the engines shut down before the shuttle has reached ... > America's progress in space instead of the shuttle disasters. ... China IS going to go to the moon. ... is that the reason it hasn't happened is not the fault of NASA. ...
    (alt.home.repair)