Solar power hobbles another spacecraft? (The comet lander crippled)

On Friday, November 21, 2014 9:55:44 AM UTC-5, Chris L Peterson wrote:
On Fri, 21 Nov 2014 06:21:24 -0800 (PST), wsnell01@ wrote:

The only occurrence of "engineer" in the article was in reference to solar panels. "Engineering failure" was not mentioned explicitly in the article. However, I was primarily interested in the landing/anchoring system, which apparently did NOT work as expected (or as "engineered.")

I'm talking about the landing system, which does not represent an
engineering failure. My point was simply that there's a difference
between and engineering failure and something not working as hoped.

Tacoma Narrows... engineering failure -or- not working as hoped?

Which was it?

On Fri, 21 Nov 2014 07:45:47 -0800 (PST), wrote:

Tacoma Narrows... engineering failure -or- not working as hoped?

Which was it?

An engineering failure, because what happened was potentially
predictable given the knowledge available when the bridge was
designed.

The Philae landing system was designed with no actual knowledge about
the nature of the surface on which it would be used. It's also
possible that the failure was due to the degradation of the explosive
charges after a long period in a vacuum- a problem not recognized to
exist until after Rosetta was already launched. Again, not so much an
engineering failure as a problem caused by inadequate information.

On Friday, November 21, 2014 11:24:57 AM UTC-5, Chris L Peterson wrote:
On Fri, 21 Nov 2014 07:45:47 -0800 (PST), wsnell01 wrote:

Tacoma Narrows... engineering failure -or- not working as hoped?

Which was it?

An engineering failure, because what happened was potentially
predictable given the knowledge available when the bridge was
designed.

Yet surely the engineers must have -hoped- that it wouldn't fall down due to a relatively light wind?


The Philae landing system was designed with no actual knowledge about
the nature of the surface on which it would be used.

What DID they think the surface was made of, styrofoam?

It's also
possible that the failure was due to the degradation of the explosive
charges after a long period in a vacuum- a problem not recognized to
exist until after Rosetta was already launched.

Then perhaps they really didn't know what they were doing?

Again, not so much an
engineering failure as a problem caused by inadequate information.

You aren't really describing what (in your mind) is the difference between "engineering failure" and "not working as hoped."

On Sat, 22 Nov 2014 03:36:00 -0800 (PST), wrote:

Yet surely the engineers must have -hoped- that it wouldn't fall down due to a relatively light wind?

The engineering failure of the Tacoma Narrows Bridge is well
documented if you want to read about it. Petroski has written about it
extensively (as well as about other famous engineering failures).

The Philae landing system was designed with no actual knowledge about
the nature of the surface on which it would be used.

What DID they think the surface was made of, styrofoam?

Based on the best information available when the probe was under
design, they assumed a fairly fluffy, snow-like surface.

It's also
possible that the failure was due to the degradation of the explosive
charges after a long period in a vacuum- a problem not recognized to
exist until after Rosetta was already launched.

Then perhaps they really didn't know what they were doing?

I think they knew what they were doing. They simply lacked
information. Those are very different things.

You aren't really describing what (in your mind) is the difference between "engineering failure" and "not working as hoped."

In this case, it's the difference between an actual engineering error
and an assumption about conditions that turned out wrong, and which
could not have been reasonably foreseen because of a lack of complete
information.

On 2014-11-14 10:21:23 +0000, said:

Pu-238 is in short supply.

No it's not. The Japanese had so much in storage at Fukushima Daiichi
that they could have probably built an Eiffel Tower out of it.

And most anybody with a reactor can make it.

On 22/11/2014 11:36, wrote:
On Friday, November 21, 2014 11:24:57 AM UTC-5, Chris L Peterson wrote:
On Fri, 21 Nov 2014 07:45:47 -0800 (PST), wsnell01 wrote:

Tacoma Narrows... engineering failure -or- not working as hoped?

Which was it?

An engineering failure, because what happened was potentially
predictable given the knowledge available when the bridge was
designed.

Yet surely the engineers must have -hoped- that it wouldn't fall down due to a relatively light wind?

They hadn't bargained on accidentally constructing a rather high Q
mechanical oscillator that was prone to serious resonance effects at
certain steady wind speeds. Bridge design was not fully understood at
the time.

There was less excuse for the London Millennium footbridge where the
design was resonant at normal footfall speeds and they were unlucky
enough to run a walking race across it on the opening day. Everyone on
the bridge lock stepped and the thing bounced sideways quite violently
(though not enough to break it).

http://www.youtube.com/watch?v=gQK21572oSU

The mention of soldiers breaking step when crossing a bridge is
interesting. I researched the original story and found that it was a
rickety suspension bridge in Salford England. A platoon of 74 troops
marched across it in step with predictable results.

http://www.information-britain.co.uk...tes.php?id=923

The Philae landing system was designed with no actual knowledge about
the nature of the surface on which it would be used.

What DID they think the surface was made of, styrofoam?

Basically conventional wisdom was dirty snowball so something like a
terrestrial glacier must have been their expectation. They got something
more like a quarry full of angular basaltic scree.

It's also
possible that the failure was due to the degradation of the explosive
charges after a long period in a vacuum- a problem not recognized to
exist until after Rosetta was already launched.

Then perhaps they really didn't know what they were doing?

Hard to know things before they were discovered unless you have a time
machine.

Again, not so much an
engineering failure as a problem caused by inadequate information.

You aren't really describing what (in your mind) is the difference between "engineering failure" and "not working as hoped."

The nature of a comet nucleus wasn't known so they were having to make
educated guesses about what would work to keep the probe on the surface.

--
Regards,
Martin Brown

On Sat, 22 Nov 2014 16:01:21 -0800, Oregonian Haruspex
wrote this crap:

On 2014-11-14 10:21:23 +0000, said:

Pu-238 is in short supply.

No it's not. The Japanese had so much in storage at Fukushima Daiichi
that they could have probably built an Eiffel Tower out of it.

Then why wasn't Godzilla there? Besides, the Eiffel Tower is mostly
air.


This signature is now the ultimate
power in the universe

On Saturday, November 22, 2014 9:57:40 AM UTC-5, Chris L Peterson wrote:
On Sat, 22 Nov 2014 03:36:00 -0800 (PST), wsnell01 wrote:

Yet surely the engineers must have -hoped- that it wouldn't fall down due to a relatively light wind?

The engineering failure of the Tacoma Narrows Bridge is well
documented if you want to read about it. Petroski has written about it
extensively (as well as about other famous engineering failures).

I had use the word "expected," whereas you used the word "hoped."

wsnell01 wrote:

"The only occurrence of "engineer" in the article was in reference to solar
panels. "Engineering failure" was not mentioned explicitly in the article. However, I was primarily interested in the landing/anchoring system, which apparently did NOT work as expected (or as "engineered.") "

peterson wrote:

"I'm talking about the landing system, which does not represent an
engineering failure. My point was simply that there's a difference
between and engineering failure and something not working as hoped."

You have failed to explain what you mean by:
"difference between and engineering failure and something not working as hoped."

The Philae landing system was designed with no actual knowledge about
the nature of the surface on which it would be used.

What DID they think the surface was made of, styrofoam?

Based on the best information available when the probe was under
design, they assumed a fairly fluffy, snow-like surface.

For a PERIODIC comet... REALLY?

On Saturday, November 22, 2014 7:01:23 PM UTC-5, Oregonian Haruspex wrote:
On 2014-11-14 10:21:23 +0000, wsnell01 said:

Pu-238 is in short supply.

No it's not. The Japanese had so much in storage at Fukushima Daiichi
that they could have probably built an Eiffel Tower out of it.

And most anybody with a reactor can make it.

But separating it from the isotopes that you DON'T want...

On Tue, 25 Nov 2014 18:32:19 -0800 (PST), wrote:

You have failed to explain what you mean by:
"difference between and engineering failure and something not working as hoped."

I have explained it clearly. I can only go so far to allow for your
intellectual limitations.

Based on the best information available when the probe was under
design, they assumed a fairly fluffy, snow-like surface.

For a PERIODIC comet... REALLY?

Yes. That was the view a dozen years ago.