Lame CEV windows

Looked it up, Melting point is far too low at around 250 celcius.
probably a pretty big no go for reentry. There has got to be somthing
better then glass though. Does the shuttle use glass?

In article .com,
wrote:
Yeah, good points, although why use glass? stuff like polycarbonate or
trivex is much stronger and ligher.

They don't handle heat very well, alas, and at least some of them don't
age well in an ultraviolet-rich environment.
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In article . com,
wrote:
Looked it up, Melting point is far too low at around 250 celcius.
probably a pretty big no go for reentry. There has got to be somthing
better then glass though. Does the shuttle use glass?

Yep. An inner pane of aluminosilicate glass (strong but limited heat
resistance) as the primary pressure window, a middle pane of fused silica
(not quite as strong but thermally quite remarkable) as combination backup
pressure seal and secondary thermal protection, and a fused-silica outer
pane as primary thermal protection.

To get better then glass, I think you have to go to exotic things like
synthetic sapphire, which generally aren't available in big slabs with
high optical quality. (Some of the orbiter windows are, or were, the
biggest optical-grade fused-silica windows ever made.)
--
spsystems.net is temporarily off the air; | Henry Spencer
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In article . com,
Tom Cuddihy wrote:
As they say on submarines...windows are for tourists...
Besides, in the age of color XGA flatpanel diplays that weigh 1 pound,
who needs windows?

Hard to take photographs through them. :-) (This is one reason why NASA
insists on optically-flat windows.)

There are also problems with limited dynamic range, inferior resolution,
difficulty in providing stereo vision, etc. that limit what you can do
with displays. People have been tinkering with camera-plus-display vision
systems for high-performance aircraft for *many* years, and to date
there's no actual use of them. Eyeballs plus windows still work better,
in addition to not needing electrical power and generally being more
fault-tolerant.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

"Tom Cuddihy" wrote in message
ups.com...

Henry Spencer wrote:
In article . com,
wrote:
I understand the design will change a bit, but is there is technical
reason to need little tiny apollo style windows on this thing? Why cant
you build big windows like the shuttle has on a capsule?

Big windows are heavy, which matters more to a smaller vehicle, and they
are difficult to protect against the higher temperatures of a capsule

As they say on submarines...windows are for tourists...

NASA should be thinking about tourists, because it is hard to justify more
than 6 flights to the moon without them and it is hard to justify designing
a new vehicle for less than 6 flights.

Space Tourism is for private industy and cash strapped defeated
superpowers. NASA should not be in that bussiness.

Henry Spencer wrote:
In article . com,
wrote:
Looked it up, Melting point is far too low at around 250 celcius.
probably a pretty big no go for reentry. There has got to be somthing
better then glass though. Does the shuttle use glass?

Yep. An inner pane of aluminosilicate glass (strong but limited heat
resistance) as the primary pressure window, a middle pane of fused silica
(not quite as strong but thermally quite remarkable) as combination backup
pressure seal and secondary thermal protection, and a fused-silica outer
pane as primary thermal protection.

Could probably use polycarbonate as the inner pane. Lighter, stronger,
cheaper. But it's easily scratched.

To get better then glass, I think you have to go to exotic things like
synthetic sapphire, which generally aren't available in big slabs with
high optical quality. (Some of the orbiter windows are, or were, the
biggest optical-grade fused-silica windows ever made.)

A few years ago there was a report on metal glass. By forming the metal
around nano particles, which are then dissolved away, a honey-comb
structure is made. With small enough holes (sub wavelength) the
material is transparant.

But it would much, much easier to use retractable cameras.

Henry Spencer wrote:
In article . com,
Tom Cuddihy wrote:
As they say on submarines...windows are for tourists...
Besides, in the age of color XGA flatpanel diplays that weigh 1 pound,
who needs windows?

Hard to take photographs through them. :-) (This is one reason why NASA
insists on optically-flat windows.)

But you'd get much better pictures having your camera outside the
window.

There are also problems with limited dynamic range, inferior resolution,
difficulty in providing stereo vision, etc. that limit what you can do
with displays.

I think modern cameras can match resolution of the human eye. Distance
estimation is a problem, but it is anyway in 3d space with limited
visual clues. I think Camera plus instrumentation specialised for the
task in hand (e.g. laser guidance) will be better than eyeballs. It may
not have been in the days of Apollo, but it is now.

People have been tinkering with camera-plus-display vision
systems for high-performance aircraft for *many* years, and to date
there's no actual use of them. Eyeballs plus windows still work better,
in addition to not needing electrical power and generally being more
fault-tolerant.

Range finding was used by the dambusters to get the right height. They
knew that the crew couldn't jusdge this accurately at night. I think a
space environment with the sharp contrasts between dark and light, and
no vertical on which to orientate means that eyeball through thick
window will be unreliable.

Likewise, when visibility is very poor, computers need to land the
plane. The pilots don't like doing this, but last time I experienced
it, it was the smoothest landing ever.

So scrapping windows on the CEV would save weight and money. But since
these are not NASA objectives ....

In article , says...

In article . com,
Tom Cuddihy wrote:
As they say on submarines...windows are for tourists...
Besides, in the age of color XGA flatpanel diplays that weigh 1 pound,
who needs windows?

Hard to take photographs through them. :-) (This is one reason why NASA
insists on optically-flat windows.)

There are also problems with limited dynamic range, inferior resolution,
difficulty in providing stereo vision, etc. that limit what you can do
with displays. People have been tinkering with camera-plus-display vision
systems for high-performance aircraft for *many* years, and to date
there's no actual use of them. Eyeballs plus windows still work better,
in addition to not needing electrical power and generally being more
fault-tolerant.


What about this:
http://www.af.mil/news/story.asp?id=123012131

(new armor glass the military is researching)

- Tim

I'd prefer a General Products hull.