Multiple Engines???

Am 24 Nov 2003 10:43:17 -0800 schrieb "George William Herbert":

I know of occurences, where the term 'hard start' WAS used as an
euphemism to explain, why a mission goal could not be achieved.

One example I can pick out is the Ariane-5 mission (L#142) that should
have launched Artemis and BSAT-2B to GTO - BSAT was lost completely,
and Artemis lost much mission time by that so called hard start...

So, find a second such incident.

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

But btw: I would not need to find more incidents than one - even one
single documented use of that term (you're free to chose one :-)
proves my words right, undeniable and without doubt.

cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
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Am 24 Nov 2003 10:43:17 -0800 schrieb "George William Herbert":

I know of occurences, where the term 'hard start' WAS used as an
euphemism to explain, why a mission goal could not be achieved.

One example I can pick out is the Ariane-5 mission (L#142) that should
have launched Artemis and BSAT-2B to GTO - BSAT was lost completely,
and Artemis lost much mission time by that so called hard start...

So, find a second such incident.

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

But btw: I would not need to find more incidents than one - even one
single documented use of that term (you're free to chose one :-)
proves my words right, undeniable and without doubt.

cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
--
/"\ ASCII Ribbon Campaign
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http://zili.de X No HTML in
/ \ email & news

"Josh Hopkins" wrote in message ...
Bimese is one of those ideas that just doesn't work when you start looking
at the details.


The points you make may be true if the two component vehicles maintain
a single, fixed, role (i.e. booster and orbiter). However, IMHO, the
key benefit of the Bimese concept can only be realised if it is
extended to mission operations and the two identical vehicles are used
in both roles (e.g. on odd numbered missions Vehicle A is the orbiter
and Vehicle B the booster; on even numbered missions Vehicle A is the
booster and Vehicle B the orbiter).


On top of that, the functional requirements for a first and second stage
really aren't all that similar. A true bimese configuration forces the
duplication of wholly unnecessary systems on the two stages.


However, if the concept is applied at the operational level, these
design aspects become wholly necessary and, therefore, fully
justifiable.

Obviously, carrying around the deadweight of these superfluous systems makes
the overall system substantially heavier than an optimized design. To which
one might argue that mass isn't what matters - cost is. So consider this,
does it really make sense, from an cost standpoint, to needlessly duplicate
the components of the system that are the most expensive to buy and
maintain - engines, TPS and power?


Not if the vehicles maintain a fixed role. However, if they
continually swap roles, I can see many benefits in terms of both
operations (common facilities, EGSE, components and procedures), costs
(increased production runs) and system robustness (interoperability of
vehicles, which also allows for a smaller fleet).


For more on this subject, see "Selection of Lockheed Martin's Preferred TSTO
Configurations for the Space Launch Initiative" paper number IAC-02-V.4.03
from the 2002 World Space Congress. It describes a trade study in which
bimese placed last out of twenty TSTO configurations. It is interesting to
observe that all three of the SLI/2GRLV contractor teams plus NASA studied
bimese concepts, and that bimese was the initial baseline for Boeing and
Orbital, yet by the end of the contract no one thought it was the preferred
choice.


I haven't yet seen this paper - did they consider the benefits of
exchanging operational roles or assume each vehicle performed just one
fixed role?


Dave

Josh Hopkins

"Josh Hopkins" wrote in message ...
Bimese is one of those ideas that just doesn't work when you start looking
at the details.


The points you make may be true if the two component vehicles maintain
a single, fixed, role (i.e. booster and orbiter). However, IMHO, the
key benefit of the Bimese concept can only be realised if it is
extended to mission operations and the two identical vehicles are used
in both roles (e.g. on odd numbered missions Vehicle A is the orbiter
and Vehicle B the booster; on even numbered missions Vehicle A is the
booster and Vehicle B the orbiter).


On top of that, the functional requirements for a first and second stage
really aren't all that similar. A true bimese configuration forces the
duplication of wholly unnecessary systems on the two stages.


However, if the concept is applied at the operational level, these
design aspects become wholly necessary and, therefore, fully
justifiable.

Obviously, carrying around the deadweight of these superfluous systems makes
the overall system substantially heavier than an optimized design. To which
one might argue that mass isn't what matters - cost is. So consider this,
does it really make sense, from an cost standpoint, to needlessly duplicate
the components of the system that are the most expensive to buy and
maintain - engines, TPS and power?


Not if the vehicles maintain a fixed role. However, if they
continually swap roles, I can see many benefits in terms of both
operations (common facilities, EGSE, components and procedures), costs
(increased production runs) and system robustness (interoperability of
vehicles, which also allows for a smaller fleet).


For more on this subject, see "Selection of Lockheed Martin's Preferred TSTO
Configurations for the Space Launch Initiative" paper number IAC-02-V.4.03
from the 2002 World Space Congress. It describes a trade study in which
bimese placed last out of twenty TSTO configurations. It is interesting to
observe that all three of the SLI/2GRLV contractor teams plus NASA studied
bimese concepts, and that bimese was the initial baseline for Boeing and
Orbital, yet by the end of the contract no one thought it was the preferred
choice.


I haven't yet seen this paper - did they consider the benefits of
exchanging operational roles or assume each vehicle performed just one
fixed role?


Dave

Josh Hopkins

In article ,
Mike Miller wrote:
Not unless it has truly excellent aerodynamic performance, which is
another nasty can of worms. It's not all that high up by the time it
can get turned around.

Alright, back to powered flybacks for first stages. Are jet engines
worth the trouble of extra systems?

Without having done the arithmetic, I suspect they're very hard to avoid.
Using rocket thrust just eats up too much fuel, especially given that a
rocket stage's subsonic L/D is unlikely to be all that good.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

In article ,
Mike Miller wrote:
Not unless it has truly excellent aerodynamic performance, which is
another nasty can of worms. It's not all that high up by the time it
can get turned around.

Alright, back to powered flybacks for first stages. Are jet engines
worth the trouble of extra systems?

Without having done the arithmetic, I suspect they're very hard to avoid.
Using rocket thrust just eats up too much fuel, especially given that a
rocket stage's subsonic L/D is unlikely to be all that good.
--
MOST launched 30 June; first light, 29 July; 5arcsec | Henry Spencer
pointing, 10 Sept; first science, early Oct; all well. |

Heinrich Zinndorf-Linker (zili@home) wrote:
Am 24 Nov 2003 10:43:17 -0800 schrieb "George William Herbert":
I know of occurences, where the term 'hard start' WAS used as an
euphemism to explain, why a mission goal could not be achieved.

One example I can pick out is the Ariane-5 mission (L#142) that should
have launched Artemis and BSAT-2B to GTO - BSAT was lost completely,
and Artemis lost much mission time by that so called hard start...

So, find a second such incident.

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

This is not an argument about whether Hard Starts ever happen.
They clearly have happened, a lot in engine development, and some
in early flight programs. I was never challenging that.

I am challenging that Hard Starts are in any way a significant
contributor to production space launch vehicle launch failure
rates.

But btw: I would not need to find more incidents than one - even one
single documented use of that term (you're free to chose one :-)
proves my words right, undeniable and without doubt.

Umm, no. What you said earlier was:
Heinrich Zinndorf-Linker wrote:
Am 22 Nov 2003 19:21:55 -0800 schrieb "George William Herbert":
Engines actually rarely explode on failure; going back
through the history of flight failures shows almost exclusively
systems failure followed by shutdown, or accidental shutdown,
without any uncontained failure. It's not unknown but is a lot
rarer than 'graceful' shutdowns.

Ok, then search for "hard start" instead - that's the euphemism used
for engine explosion when it occurs on ignition. You will maybe
surprised to find a significant number of them...

You specifically argued here that not just did hard starts
happen in production flights, but that there were a significant
number of them.

"one" is not "a significant number".

As I said; take the Space Launch Systems guide, 3rd edition,
and detailed failure histories of the various rockets,
and look at the failure causes.

Your assertion that there are a significant number
of them is not born out by the data, based on my
qualitative analysis when you first brought this up.

You are welcome to, for example, take all the failures listed
and categorize them and provide statistics, if you want to
argue the contrary. But as I said... I didn't find any hard
start induced launch failures through 1999 in the book,
leafing through it to see what the historical occurrances
looked like. I missed one or two somewhere? Credible.
I missed something statistically significant, out of the
hundred or so entries for failures? Less credible.


-george william herbert

Heinrich Zinndorf-Linker (zili@home) wrote:
Am 24 Nov 2003 10:43:17 -0800 schrieb "George William Herbert":
I know of occurences, where the term 'hard start' WAS used as an
euphemism to explain, why a mission goal could not be achieved.

One example I can pick out is the Ariane-5 mission (L#142) that should
have launched Artemis and BSAT-2B to GTO - BSAT was lost completely,
and Artemis lost much mission time by that so called hard start...

So, find a second such incident.

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

This is not an argument about whether Hard Starts ever happen.
They clearly have happened, a lot in engine development, and some
in early flight programs. I was never challenging that.

I am challenging that Hard Starts are in any way a significant
contributor to production space launch vehicle launch failure
rates.

But btw: I would not need to find more incidents than one - even one
single documented use of that term (you're free to chose one :-)
proves my words right, undeniable and without doubt.

Umm, no. What you said earlier was:
Heinrich Zinndorf-Linker wrote:
Am 22 Nov 2003 19:21:55 -0800 schrieb "George William Herbert":
Engines actually rarely explode on failure; going back
through the history of flight failures shows almost exclusively
systems failure followed by shutdown, or accidental shutdown,
without any uncontained failure. It's not unknown but is a lot
rarer than 'graceful' shutdowns.

Ok, then search for "hard start" instead - that's the euphemism used
for engine explosion when it occurs on ignition. You will maybe
surprised to find a significant number of them...

You specifically argued here that not just did hard starts
happen in production flights, but that there were a significant
number of them.

"one" is not "a significant number".

As I said; take the Space Launch Systems guide, 3rd edition,
and detailed failure histories of the various rockets,
and look at the failure causes.

Your assertion that there are a significant number
of them is not born out by the data, based on my
qualitative analysis when you first brought this up.

You are welcome to, for example, take all the failures listed
and categorize them and provide statistics, if you want to
argue the contrary. But as I said... I didn't find any hard
start induced launch failures through 1999 in the book,
leafing through it to see what the historical occurrances
looked like. I missed one or two somewhere? Credible.
I missed something statistically significant, out of the
hundred or so entries for failures? Less credible.


-george william herbert

Am 30 Nov 2003 01:42:55 -0800 schrieb "George William Herbert":

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

This is not an argument about whether Hard Starts ever happen.
They clearly have happened, a lot in engine development, and some
in early flight programs. I was never challenging that.

That's a begin of concensus :-)

I am challenging that Hard Starts are in any way a significant
contributor to production space launch vehicle launch failure
rates.

Yes, I think so. I will try to explain below.

You specifically argued here that not just did hard starts
happen in production flights, but that there were a significant
number of them.

"one" is not "a significant number".

That discussion seems to lead to a "hunt in a circle". In my eyes
every single occurence has its significance. Especially in a regime
with low total numbers every single incident counts. And space
launches ARE low in numbers, so even one "hard start" counts - in my
opinion.

As I said; take the Space Launch Systems guide, 3rd edition,
and detailed failure histories of the various rockets,
and look at the failure causes.

Your assertion that there are a significant number
of them is not born out by the data, based on my
qualitative analysis when you first brought this up.

I followed your advice to take the SLSG3, and picked a page 'by
chance' (it was the 'Titan') and looked for mission failures. And I
found a relatively large number of failure descriptions, that COULD
have been called hard start, instead. Especially the Titan-Agena
launches seem to be in that category.

You are welcome to, for example, take all the failures listed
and categorize them and provide statistics, if you want to
argue the contrary. But as I said... I didn't find any hard
start induced launch failures through 1999 in the book,
leafing through it to see what the historical occurrances
looked like. I missed one or two somewhere? Credible.
I missed something statistically significant, out of the
hundred or so entries for failures? Less credible.

Maybe we have simply a different view about significance, especially
when used as a statistical term. I'd say, we should end that
discussion - or continue it, and follow up via eMail...

cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
--
/"\ ASCII Ribbon Campaign
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http://zili.de X No HTML in
/ \ email & news

Am 30 Nov 2003 01:42:55 -0800 schrieb "George William Herbert":

ok, look back to the development history of the first American liquid
fueled multi-stage sounding rockets somewhen in the 19'fifties - there
was that very same euphemism chosen for describing a failure cause. Or
read the history of X-planes - you will find that term used in this
way, too.

This is not an argument about whether Hard Starts ever happen.
They clearly have happened, a lot in engine development, and some
in early flight programs. I was never challenging that.

That's a begin of concensus :-)

I am challenging that Hard Starts are in any way a significant
contributor to production space launch vehicle launch failure
rates.

Yes, I think so. I will try to explain below.

You specifically argued here that not just did hard starts
happen in production flights, but that there were a significant
number of them.

"one" is not "a significant number".

That discussion seems to lead to a "hunt in a circle". In my eyes
every single occurence has its significance. Especially in a regime
with low total numbers every single incident counts. And space
launches ARE low in numbers, so even one "hard start" counts - in my
opinion.

As I said; take the Space Launch Systems guide, 3rd edition,
and detailed failure histories of the various rockets,
and look at the failure causes.

Your assertion that there are a significant number
of them is not born out by the data, based on my
qualitative analysis when you first brought this up.

I followed your advice to take the SLSG3, and picked a page 'by
chance' (it was the 'Titan') and looked for mission failures. And I
found a relatively large number of failure descriptions, that COULD
have been called hard start, instead. Especially the Titan-Agena
launches seem to be in that category.

You are welcome to, for example, take all the failures listed
and categorize them and provide statistics, if you want to
argue the contrary. But as I said... I didn't find any hard
start induced launch failures through 1999 in the book,
leafing through it to see what the historical occurrances
looked like. I missed one or two somewhere? Credible.
I missed something statistically significant, out of the
hundred or so entries for failures? Less credible.

Maybe we have simply a different view about significance, especially
when used as a statistical term. I'd say, we should end that
discussion - or continue it, and follow up via eMail...

cu, ZiLi aka HKZL (Heinrich Zinndorf-Linker)
--
/"\ ASCII Ribbon Campaign
\ /
http://zili.de X No HTML in
/ \ email & news