"Evaluation of Ice and Frost Accumulation on the Space Shuttle Ext

"Evaluation of Ice and Frost Accumulation on the Space Shuttle External
Tank"

R.E. Rhodes and S.W. Walker
Proceedings of the Thirteenth Space Congress
April 7-9, 1976

http://klabs.org/richcontent/Reports.../rhodes_76.pdf


I`m most impressed by what it avoided to mention:

- Unprotected foam on the outside of a supersonic vehicle was an
untested news.

- That sheeding foam could endanger the TPS was obvious.

- That all problems in the paper and much more was the result of a wrong
weight/performance estimate early in the project. At least thats my
assumption. Otherwise I cant explain the neglect of an ET outershell.


Reminds of Apollo. There is the story that von Braun crossly overdesigned
the Saturn V after he got the first weight estimates for the LEM and CSM.
He did not trust the estimates. He was right and saved the Apollo project
timeline by his lone decision. If true, it seems they had no longer a
person with such authority in the early 1970s.


## CrossPoint v3.12d R ##

wrote:

Reminds of Apollo. There is the story that von Braun crossly overdesigned
the Saturn V after he got the first weight estimates for the LEM and CSM.
He did not trust the estimates. He was right and saved the Apollo project
timeline by his lone decision. If true, it seems they had no longer a
person with such authority in the early 1970s.



Yeah, it's always better to have several tons of excess capability than
a few pounds too little.
The Soviets didn't do that on the N-1, and found out it couldn't carry
enough weight for their lunar mission as it was envisioned due to the
booster coming in way over design weight.

Pay

In article ,
wrote:
I`m most impressed by what it avoided to mention:
- Unprotected foam on the outside of a supersonic vehicle was an
untested news.

No, it had been used quite successfully on the Saturn V second stage. (In
fact, the foam used for that was the original choice for the ET, but it
was awfully heavy and a new lighter foam ended up being used.) They had to
fly test samples on the X-15 to reach the relevant flight conditions.

- That all problems in the paper and much more was the result of a wrong
weight/performance estimate early in the project. At least thats my
assumption. Otherwise I cant explain the neglect of an ET outershell.

Such a shell adds its own problems and there was no indication that it was
necessary.

The shuttle *did* have serious problems with over-optimistic weight
estimates, but this wasn't one of them.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

On Wed, 21 Sep 2005 23:24:00 -0500, Henry Spencer wrote
(in article ):

The shuttle *did* have serious problems with over-optimistic weight
estimates, but this wasn't one of them.

In fairness, nearly every aerospace vehicle of any complexity usually
does. Hopefully the propulsion people take this into account at the
outset.

Aside: during late SSF days prior to CDR, Boeing was offering employee
bonuses of $200 for every pound reduced from the baseline launch weight
for the Node and Lab.

--
"Fame may be fleeting but obscurity is forever." ~Anonymous
"I believe as little as possible and know as much as I can."
~Todd Stuart Phillips
www.angryherb.net

Herb Schaltegger wrote:

On Wed, 21 Sep 2005 23:24:00 -0500, Henry Spencer wrote
(in article ):

The shuttle *did* have serious problems with over-optimistic weight
estimates, but this wasn't one of them.

In fairness, nearly every aerospace vehicle of any complexity usually
does.

Nit: In fairness nearly any project of any significant complexity
will exceed it's budget, it's timeline, or it's weight/volume
allowance.

Folks like to pretend NASA is an abberation, and everyone else gets it
right... But the reality is while NASA is an unusually bad case, but
not an unusual case.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

Herb Schaltegger ) writes:
On Wed, 21 Sep 2005 23:24:00 -0500, Henry Spencer wrote
(in article ):

The shuttle *did* have serious problems with over-optimistic weight
estimates, but this wasn't one of them.

In fairness, nearly every aerospace vehicle of any complexity usually
does. Hopefully the propulsion people take this into account at the
outset.

Aside: during late SSF days prior to CDR, Boeing was offering employee
bonuses of $200 for every pound reduced from the baseline launch weight
for the Node and Lab.

Theres also the addition of the centreline F-1 to the original C-5
design, which also helped out with the structural loads in the bottom
of the S-1C stage, and gave the vehicle more thrust, for a greater
load carrying capacity, which Von Braun's folks kinda suspected that
the Apollo spacecraft would end up needing, anyway...

Andre

--
" I'm a man... But, I can change... If I have to... I guess. "
The Man Prayer, Red Green.

I`m most impressed by what it avoided to mention:
- Unprotected foam on the outside of a supersonic vehicle was an
untested news.

No, it had been used quite successfully on the Saturn V second stage. (In
fact, the foam used for that was the original choice for the ET, but it
was awfully heavy and a new lighter foam ended up being used.) They had to
fly test samples on the X-15 to reach the relevant flight conditions.

Thanks a lot Henry! Thats big news for me. Looking at the Saturn V
I allways thought I see a painted metall surface

The whole foam story gets some epic dimensions. I found a X-15 photograph
how they did it:

A second type of experiment involved testing the insulation of the
Saturn booster on the dive brakes of the X-15 where the severe
real-environmental heating situation of the Saturn could be duplicated
(fig. 19). Saturn insulation on X-15 dive break showing flow-field rake
and photographic reference grid..
http://www.hq.nasa.gov/office/pao/Hi...ct/follow.html

One of the flights with "Saturn Insulation" was the deadly crash
of Major Adams 11-15-67:
http://www.check-six.com/Crash_Sites...rt/Ops_Rpt.htm

It was later repeated:
01 March 1968 X-15A Checkout mission Spacecraft: X-15A. Launch Site:
Edwards . Launch Vehicle: X-15A: Maximum Speed - 4631 kph.
Maximum Altitude - 31850 m. Tested Saturn V insulation.

As the last X-15 flight was October 24, 1968 I suspect no specific
test were done for the Shuttle programm. If I read your answer
right the foam on the Saturn V and X-15 was of another type and
more heavy (more robust?) than the later ET foam. If so, why was
the ET foam never tested the same way by some rocket?
Perhaps they had enough flight data to deduce sufficient ground tests?
Is there a paper somewhere on the foam history?

- That all problems in the paper and much more was the result of a wrong
weight/performance estimate early in the project. At least thats my
assumption. Otherwise I cant explain the neglect of an ET outershell.

Such a shell adds its own problems and there was no indication that it was
necessary.

Do you know how the Soviets solved it on the Energia?
Astronautics has a good picture but no mention of foam or insulation.
Could be a composite:
http://www.astronautix.com/lvs/energia.htm


So to use the new ET foam unprotected was a theoretical design
desision but with a knowledge base on some prior foam and test flights.
It seems the sheeding was a bad surprise after the first flight in 1981.
What went wrong? As we know from the CAIB NASA never had a sufficient
theory why the foam behaved that way. Even today after RTF they are
unsu

"...We were surprised at both the fact that it was PAL ramp foam and
the size of it." He said NASA now will have to re-examine the physics
behind foam loss and perhaps re-think the theory that voids in the
foam are primarily responsible for separation in flight.
"The idea that voids were primarily the cause of separation, that you
can see these voids in non-destructive inspection, has all been
challenged by what happened on the launch," Covey said.
(WILLIAM HARWOOD, CBS NEWS: July 29, 2005)


But could it be that the foam matched its specifications but the
specs were wrong?:

Data collected by sensors on Discovery's tank showed the air flow
across that region [PAL ramp] of the tank is more complex than
previously believed and significantly different from assumptions
built into computer programs used to model the environment.
(WILLIAM HARWOOD, CBS NEWS: September 8, 2005)

It reminds on the fact that the ET has the most harsh and complicated
flow regime of all launchers. Its hit by the shock waves from the SRBs
and the shuttle. I wonder that NASA never did full instrumentation
flights after the first one.



The shuttle *did* have serious problems with over-optimistic weight
estimates, but this wasn't one of them.

Could you point to a book or paper on this issue?


## CrossPoint v3.12d R ##

rk wrote:

Derek Lyons wrote:

Nit: In fairness nearly any project of any significant complexity
will exceed it's budget, it's timeline, or it's weight/volume
allowance.

Heh, estimates are usually given as +/- x units; many wonder why they bother
to put the '-' in.

Because JPL needs them in front of the 'science capabilities' section,
as the capabilities see a lot of '-' while they attempt to stay on
budget/timeline and within weight/volume.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

wrote:

As the last X-15 flight was October 24, 1968 I suspect no specific
test were done for the Shuttle programm. If I read your answer
right the foam on the Saturn V and X-15 was of another type and
more heavy (more robust?) than the later ET foam. If so, why was
the ET foam never tested the same way by some rocket?
Perhaps they had enough flight data to deduce sufficient ground tests?
Is there a paper somewhere on the foam history?

See http://www.nasa.gov/columbia/foia/index.html, and scroll down to
"Lessons Learned-A Technical History of the External Tank". Lots of
good stuff on the ET in that section.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

wrote:

ns.



Thanks a lot Henry! Thats big news for me. Looking at the Saturn V
I allways thought I see a painted metall surface

Cork also got used somewhere on the Saturn V as insulation IIRC; was it
in the four petals that covered the LM during ascent?


"...We were surprised at both the fact that it was PAL ramp foam and
the size of it." He said NASA now will have to re-examine the physics
behind foam loss and perhaps re-think the theory that voids in the
foam are primarily responsible for separation in flight.
"The idea that voids were primarily the cause of separation, that you
can see these voids in non-destructive inspection, has all been
challenged by what happened on the launch," Covey said.



But if you look at the in-flight photos of the ET after jettison, it
does look like there is a "pit" down at the bottom of the area where the
PAL chunk of foam detached from the ET:
http://www.spaceflightnow.com/shuttl...s/palramp4.jpg

Pat