Directions in space?

On Sun, 22 Jun 2008 02:02:36 GMT, Gene wrote:
Robert Carnegie wrote in news:0f81f0ac-47d1-48d0-
Larry Niven's "One Face" isn't quite this; in a spaceship accident,
the computer turns out to be broken, but also the ship is dumped into
the far-distant future, but handily near Earth tidally locked to the Sun.

What happened to the Moon?

Probably it ran away; it's tidally receding, very slowly, isn't it?

Dave
--
\/David DeLaney posting from "It's not the pot that grows the flower
It's not the clock that slows the hour The definition's plain for anyone to see
Love is all it takes to make a family" - R&P. VISUALIZE HAPPYNET VRbeableBLINK
http://www.vic.com/~dbd/ - net.legends FAQ & Magic / I WUV you in all CAPS! --K.

Dear Robert Carnegie:

"Robert Carnegie" wrote in message
...
....
Let's remember that Clarke failed to predict
the operatorless satellite television station -
he expected a crew necessary to fit
repacement valves as required -

A "valve" no doubt being a vacuum tube. I do not think he felt
we would abandon "broken" satellites, and keep in mind we do have
to vist some of them periodically to replace batteries, or fit
them with corrective lenses.

Wonder why we don't use vacuum tubes for high power circuits in
space? We have vacuum, so we don't need the glass envelope...

David A. Smith

Robert Carnegie wrote in news:0f81f0ac-47d1-48d0-
:

Larry Niven's "One Face" isn't quite this; in a spaceship accident,
the computer turns out to be broken, but also the ship is dumped into
the far-distant future, but handily near Earth tidally locked to the
Sun.

What happened to the Moon?

:: Larry Niven's "One Face" isn't quite this; in a spaceship accident,
:: the computer turns out to be broken, but also the ship is dumped into
:: the far-distant future, but handily near Earth tidally locked to the
:: Sun.

: Gene
: What happened to the Moon?

IIRC, they didn't know. It's just gone. Possibly the earth had been moved,
as in "World out of Time", since this is long after any expanded-red-sun
state, but I don't recall for sure about that. I do remember they were
puzzled about a lot of things, and Just Didn't Know what had happened
in detail.


Wayne Throop http://sheol.org/throopw

In rec.arts.sf.science "N:dlzc D:aol T:com \(dlzc\)" wrote:
Wonder why we don't use vacuum tubes for high power circuits in
space? We have vacuum, so we don't need the glass envelope...

Even without the glass, I imagine that a vacuum tube will be significantly
bulkier, more massive, and more expensive than the semiconductor
equivalent.

--
Mike Ash
Radio Free Earth
Broadcasting from our climate-controlled studios deep inside the Moon

In article , dlzc\
wrote:

Wonder why we don't use vacuum tubes for high power circuits in
space? We have vacuum, so we don't need the glass envelope...

They actually do use 'traveling wave tubes' (Wiki or Google for
details) for some transmitters on spacecraft. But they don't send them
up without envelopes.

One of the reasons for this is that spacecraft systems require a lot of
testing. And it would be helpful to test them without having to put
the whole system into a huge expensive vacuum chamber.

--
David M. Palmer (formerly @clark.net, @ematic.com)

Dear Michael Ash:

"Michael Ash" wrote in message
...
In rec.arts.sf.science "N:dlzc D:aol T:com \(dlzc\)"
wrote:
Wonder why we don't use vacuum tubes for high
power circuits in space? We have vacuum, so
we don't need the glass envelope...

Even without the glass, I imagine that a vacuum
tube will be significantly bulkier, more massive,
and more expensive than the semiconductor
equivalent.

A FET is not very far from a vacuum tube. It uses applied an
E-field to "choke" the flow of electrons.

Vacuum tubes don't have to be large, but they do still need
"heaters" (what the dopants do in a semiconductor). And I accept
that near-Earth vacuum isn't good enough for sensitive
applications.

David A. Smith

On Sat, 21 Jun 2008 18:53:36 -0400, David DeLaney wrote:
| N:dlzc D:aol T:com \(dlzc\) wrote:
|Wonder why we don't use vacuum tubes for high power circuits in
|space? We have vacuum, so we don't need the glass envelope...
|
| It's not a very good vacuum, and we haven't spent the last 40 years on R&D
| miniaturizing and improving vacuum-tube technology the way we have transistor
| technology, basically. And partly because of that, there aren't vast quantities
| of types of twisty little vacuum tube, all different, lying around to plug
| into one's design process for the circuits needed for the latest space
| venture...


Besides, without the little glass envelopes, how do you stop electrons
going to the positive terminals of adjacent tubes? I suppose that metal
shielding in place of the glass would work, but it would need to be
strong enough so it won't deform and cause a short, and be prevented
from becoming charged and interfering with the function of the unit.
Perhaps glass isn't so bad after all.


--
Reverend Paul Colquhoun, ULC. http://andor.dropbear.id.au/~paulcol
Asking for technical help in newsgroups? Read this first:
http://catb.org/~esr/faqs/smart-questions.html#intro

Paul Colquhoun wrote:
On Sat, 21 Jun 2008 18:53:36 -0400, David DeLaney wrote:
| N:dlzc D:aol T:com \(dlzc\) wrote:
|Wonder why we don't use vacuum tubes for high power circuits in
|space? We have vacuum, so we don't need the glass envelope...
|
| It's not a very good vacuum, and we haven't spent the last 40 years on R&D
| miniaturizing and improving vacuum-tube technology the way we have transistor
| technology, basically. And partly because of that, there aren't vast quantities
| of types of twisty little vacuum tube, all different, lying around to plug
| into one's design process for the circuits needed for the latest space
| venture...


Besides, without the little glass envelopes, how do you stop electrons
going to the positive terminals of adjacent tubes? I suppose that metal
shielding in place of the glass would work, but it would need to be
strong enough so it won't deform and cause a short, and be prevented
from becoming charged and interfering with the function of the unit.
Perhaps glass isn't so bad after all.


The glass is oke, you just dont have to pull the air out.
They do use some tubes on satelites, like a traveling wave tubes,
which has a gain of about 1000.000 times at very high frequencies,
and is usefull as power output stage for transmitters or radars.

"David DeLaney" wrote in message
...
On Sun, 22 Jun 2008 02:02:36 GMT, Gene wrote:
Robert Carnegie wrote in
news:0f81f0ac-47d1-48d0-
Larry Niven's "One Face" isn't quite this; in a spaceship accident,
the computer turns out to be broken, but also the ship is dumped into
the far-distant future, but handily near Earth tidally locked to the
Sun.

What happened to the Moon?

Probably it ran away; it's tidally receding, very slowly, isn't it?

Dave


This is a very slow process, with the Earth predicted to tidally synchronise
with the moon in 50 billion years--long after the Sun evolves into a white
dwarf with about half its current mass lost. The moon would still orbit the
Earth.

So if there is still a Sun in the story, the loss of the Moon can't be a
natural process.

I doubt that the Sun's tides could cause the Earth to synchronise during the
Sun's remaining lifetime, so maybe that aspect was also artificial. Or
maybe the author was not worrying too much about scientific details.

Maybe someone needed it for building materials?

--
Mike Dworetsky

(Remove pants sp*mbl*ck to reply)