Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V16_0/V16NO099.ZIP/V16NO099

Internet Message Format | 1993-07-13 | 36KB

Date: Sun, 31 Jan 93 05:13:02
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #099
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 31 Jan 93       Volume 16 : Issue 099

Today's Topics:
      Clinton's Promises (space) in Charlotte Observer (3 msgs)
Fluidic envelope on a point gravitational source suspended in a uniform field (2 msgs)
                        Help on catching this
                         Lunar Map  (2 msgs)
People dragging politics into everything (was Re: Today in 1986-Remember the Challenger)
                            Shuttle tiles
                      Solar Sail/Parachute/Brake
                         Surface map of Venus
                Today in 1986-Remember the Challenger
                    Using off-the-shelf-components

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----------------------------------------------------------------------

Date: Fri, 29 Jan 1993 21:10:12 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: Clinton's Promises (space) in Charlotte Observer
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Doug Mohney)
writes:

>    C) How do you set the damned thing up without using goverment help
>       in the first place? Guess who owns all the big launch facilities.

Aw, yes, the ultimate fallback argument.

The government owns all the launch facilities because the
government crushes anyone who tries to compete with them.

It justifies its strong arm tactics by saying that launch
facilities are a "national resource" -- without government,
there would be no launch facilities.

Perfect circular reasoning.

------------------------------

Date: Fri, 29 Jan 1993 21:14:34 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: Clinton's Promises (space) in Charlotte Observer
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Ian Taylor) writes:

>Ok say Clinton went off his rocker and did just that, does anyone think
>a US corporation would do it for $10bn, tax free? - assuming this station
>has a similar specification to Freedom for volume and power and X=4.

Well, the Japanese construction industry thinks it could do
the job for around one billion.  A real space station, a la
2001, not a little tin can like SS Freedom.  Unfortunately,
Shuttle transportation costs would add another $46 billion
to that.  But if you encourage the develop of a commercial
SSTO first....



------------------------------

Date: 29 Jan 1993 17:22:31 -0500
From: Matthew DeLuca <[e-mail]>
Subject: Clinton's Promises (space) in Charlotte Observer
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Edward V. Wright) writes:

[Private group putting up a space station]

>Well, the Japanese construction industry thinks it could do
>the job for around one billion.  A real space station, a la
>2001, not a little tin can like SS Freedom.  Unfortunately,
>Shuttle transportation costs would add another $46 billion
>to that.  But if you encourage the develop of a commercial
>SSTO first....

If the Japanese can develop and build a whiz-bang space station from scratch
for only $1 billion, why can't they develop their own SSTO for a few
million dollars?  If they can do one I am sure they can do the other.

Claims like this make me wonder: we hear from certain agitators on this
group how if we only were to use cheap Soviet hardware, we could do more in
space than we do now for only a fraction of the cost.  If this is true, why
didn't the Soviets do it?  At the height of the Soviets' power, it would have
been a great propaganda victory for them to have a bustling space activity
while the Americans limped along in their Shuttle...instead, we saw the
Soviets restricted to the same tin-can technology they've been using since
1961.  Something tells me it's just not as cheap and easy as certain people
like to make it seem.

--
Matthew DeLuca
Georgia Institute of Technology, Atlanta Georgia, 30332
uucp:      ...!{decvax,hplabs,ncar,purdue,rutgers}!gatech!prism!matthew
Internet: [e-mail]

------------------------------

Date: Fri, 29 Jan 1993 19:30:42 GMT
From: Bill Hyde <[e-mail]>
Subject: Fluidic envelope on a point gravitational source suspended in a uniform field
Newsgroups: talk.origins,sci.space

In article <[e-mail]>, [e-mail] (Benjamin T Dehner) writes:

    An impressive article, but I have one problem with it.



|>     Ok, now what about the atmosphere? The force away from the earth
|> on a molecule in the atmosphere will be given by
|>     F(r) = G*m*(Mearth/r**2 - Msat*cos(b)/diss**2)
|> where
|>     Mearth = mass earth
|>         Msat = mass saturn
|>         r = distance of object from earth center
|>         diss = distance of object from saturn
|>         diss**2 = dise**2 + r**2 - 2*dise*r*cos(b) [law of cosines]
|>         b = angle bewteen object and Saturn as seen from Earth.
|>
|>     A molecule will be lost to space when it's velocity is high enough
|> so that, when it reaches an infinite distance from earth, (where gravity from
|> earth is now 0) it is still moving (can't be pulled back).  Or, as a limiting
|> case, when the velocity at infinity is zero.  Or, when the work done on the
|> particle (\int F dx) does not equal it's kinetic energy.  So if we start at
|> velocity V at the earth surface, the escape velocity will be
|>
|>              /infinity
|>             |
|> Vesc**2 = 2G| [-Msat*cos(b)/(r**2+dise**2 - 2*cos(b)*r*dise) + Mear/r**2] dr
|>             |
|>            /Rearth
|>
|> which evalutates too (not a hard integral; split into two components, and
|> use algebraic substitution)(and change notation d = dise)
|>
|> Vesc**2 = Vold**2 - 2*G*Msat*cos(b)(pi/2 - arctan(Rear**2+d**2*(1-cos(b)**2))
|>
|> Where Vold is the nominal value of the escape velocity of 1.12e6 cm/s.
|> Expanding the arctan in a series, this gives us
|>
|> Vesc**2 = Vold**2 - 2*G*Msat*cos(b)/(Rear**2+d**2*(1-cos(b)**2))
|>
|> Taking as a representive value of cos(b) = 1/2, for a numeric example we have
|> Vesc = 1.119e6 cm/s.


    You should actually take cos(b) to be one, since the
    loss of atmosphere will be dominated by escape at the
    sub-saturnian point.  Escape velocity is a function of
    the square root of the gravitational acceleration, so if
    we are postulating an effective gravitational force of
    4m/sec**2 the escape velocity should be less than two thirds
    of the current value.  The probability distribution for
    molecular velocity is maxwellian

    F(v)dv = const*exp(-const*v**2)v**2

    (where the constants are temperature dependent).

    This distribution has a long "tail" leading out to
    infinite velocity.  Any substantial decrease in escape
    velocity greatly enhances the fraction of molecules
    which are moving fast enough to escape.  Even if the planet
    were somehow as cool as earth is today, the bulk of the
    atmosphere would leak out in a fairly short time.

    If the saturnlit side were somehow temperate, then
    at the center of the dark side temperatures
    would be well below the freezing point of carbon dioxide.
    (Since in Ted's postulated word all of the continents are
    grouped around the north pole, there would be a completely
    zonal (i.e. east-west as oppposed to north-south) circulation
    in the southern oceans, and no substantial energy transport
    from the equator (a chilly place anyway, in this scenario)
    to the antarctic.  Similarly, with no mountain ranges or land/sea
    contrast to kick off long waves, the southern jet stream would
    also be quite zonal, so there would be few of the baroclinic eddies
    which currently transport most of the atmospheric heat north
    in midlatitudes.)

    C02 levels would rapidly drop to the point where photosynthesis
    would be impossible, and pretty much everything would die.
    Quite a golden age.


|> flux at the top of the earth's atmosphere?  Let's assume an albedo of 0.8
|> (Venus is 0.76) which, among other things, implies thick cloud layers such
|> that no one would ever SEE the bloody sun.  If we let energy freely radiate
|> at the opposite side of the earth (to 0 K space) the equlibrium temperature
|> will be such that Flux(in) = Flux(out), or
|>
|> 2*pi*Rear**2*.2*1.e9 = 4*pi*Rear**2*sigma*T**4
|>
|> T**4 = .2*1.e9/(2*sigma)
|>
|> T = 1152 K
|>
|>     While this is an incredibly crude approximation, the point is made
|> (I think) that the earth will be fried.

    Even more so in that these one level models tend to underestimate
    planetary temperatures as it ignores the atmospheric greenhouse
    effect.  For example, such a model predicts
    the earth's temperature to be 255 absolute.



                        Bill Hyde
Department of Oceanography
Dalhousie University,
Halifax, Nova Scotia
[e-mail] or hyde@dalac

------------------------------

Date: Fri, 29 Jan 1993 22:17:37 GMT
From: Benjamin T Dehner <[e-mail]>
Subject: Fluidic envelope on a point gravitational source suspended in a uniform field
Newsgroups: talk.origins,sci.space

>What would the characteristics be of the fluidic envelope (atmosphere and
>hydrosphere) of a gravitational point source (say, the earth) if it were to
>be suspended (through some magical method which would NOT affect the oceans)
>in a uniform (or near-uniform) intense (approximately 6 meters per second
>per second) gravitational field (say, from something that would become Saturn)?

>Off hand, I wonder about the long-term status of the atmosphere.  Would the
>escape velocity on the "near" side be reduced such that the molecular velocity
>at "room temperature" be sufficient to "bleed off" the air?  What WOULD the
>imposition of a uniform field over the inverse square field do the e.v.?
>Someone care to perform the integral?

    Excuse me for being stupid, by I made a fundamental f***up last
time I tried to answer this (in addition to misunderstanding the question.)
    Typically when calculating the escape velocity, one simply calculates
the work needed to take a particle an infinite distance away.  This, however,
is no longer the case.  One simply needs to go out to an Rmax, where Rmax
is given by the distance at which the external force balances out the earths
force.  Rmax would be given by the equation g = GM/Rmax**2, where g is the
external field, G is gravitational constant, M = earth's mass.  Plugging
in numbers, this gives us Rmax = 8.153e8 cm.  Now the total energy required
would be an integral from Rear to Rmax of m(GM/r**2 - g)dr, and set this
equal to an initial kinetic energy 1/2*m*Vesc**2 to find Vesc.  Doing this
gives us an answer of Vesc = 1.72e5 cm/s, compared to the current value of
1.12e6 cm/s, which is quite a change.
    (As an aside, the earth could not hold bound any body beyond Rmax,
either atmosphere or satellite.  While this is far enough out atmosphere
shouldn't be a problem, what about satellite?)
    Now, what fraction of the molecules in our atmopshere will have a
velocity above this?  If we assume the atmosphere has a Maxwellian
distribution (good for most of atmosphere), then the velocity distribution
function looks like

f(v)dv = (m/2/pi/k/T)**1.5*exp(-m*v**2/2/k/T)*4*pi*v**2*dv

where
    m = molecule mass = 5.31e-23 g  (O2, for example)
        T = temperature = 250K  (Why not?)
        k = Boltzmann constant = 1.381e-16 erg/K

    So we want to integrate this beasty from Vesc to infinity.  It turn
out that only about 8.e-8 of the molecules are statistically above the
escape velocity.  (No, I didn't do this myself.  I used maple.)  I am
uncertain of what this says about the long-term lifetime of the atmosphere.
Accorind to Zelik and Smith (1987), the rms velocity must be > 10*escape
velocity to retain an atmosphere for billions of years.  In this case,
Vrms = (3*k*T/m)**(1/2) = 4.414e4 for O2, < 10 * Vesc.  Anybody got a better
idea on the diffusion rate out of the atmosphere?  Also, I took low temper-
atures in the above example.  A higher representive temperature would make
things a bit worse.  Also, N2, being ligher, would leak out even faster.  It
has a Vrms = 4.72e4 cm/s, and a fraction above the escape velocity of 1.1e-6.
I do not think the earth could hold on to N2 for very long at all (timescale
of ~ a few hundred years??).

>What would the physical distribution of the object be?  On the planetary
>surface, the vector sum of the two fields would make "downhill" towards
>the primary (except in a line straight through the center of mass of the
>secondary (earth).  On the "near" point, 'g' would be reduced and on the
>"far" point 'g' would be increased.  The equipotential surface would
>be furthest from the center of mass of the secondary on the "far" side
>and nearest to the center of mass on the "near" side.  How would this
>affect things?  Would the lithosphere retain sphericality, or is the
>material strength insufficient to prevent drastic redistribution to conform
>with the equipotential shape (read: terminal earthquakes).  What would
>the atmospheric pressure be, since the mass of the atmosphere would be
>on the "far" side and the 'g' is reduced on the 'near' side?  Would the
>partial pressure of O2 be sufficient for respiration?  Would there be
>ANY oceans & lakes on the "near" side?

    I'm not sure how to answer these.  A 'uniform' field would cause no
gravitational gradients, and so I would need a more exact definition of
exactly what was holding the earth in place.  Plus, it's time I got back to
work anyway :)

Ben

Rerences:
Zelik and Smith (1987) "Introductory Astronomy and Astrophysics",
CBS: Philidelphia

--
James W. Meritt:  [e-mail] - or - [e-mail]
The opinions above are mine.  If anyone else wants to share them, fine.
They may say so if they wish. The facts "belong" to noone and simply are.


-----------------------------------------------------------------------------
Benjamin T. Dehner    Dept. of Physics and Astronomy
[e-mail]       Iowa State University
                      Ames, IA 50011

------------------------------

Date: Fri, 29 Jan 1993 21:31:11 GMT
From: Rajesh Batra <[e-mail]>
Subject: Help on catching this
Newsgroups: sci.space,sci.physics

Hi,

Here's a problem that I'm just plain stuck on, see if you can help.

Scenerio:  You're on the moon, a 1700 m/s container (containing ice) which
weighs approximately 120 kg is hurled at you. How do you catch it such
that you can salvage the ice? You have free reign over the container-
hence the size/material.

        I'm currently investigating silica aerogels--
        or a big crater coated with steel or some tough
        material to ram the projectile into. Hopefully, I can
        close the opening of the container before the vaporized
        ice escapes.


                        Thanks for your time,

                        Rajesh Batra
                        University of Cincinnati
                        Aerospace Engineering
                        [e-mail]

------------------------------

Date: Fri, 29 Jan 1993 19:40:30 GMT
From: Lord Vader <[e-mail]>
Subject: Lunar Map
Newsgroups: sci.space,sci.space.shuttle

I need a digital map of the moon for ground tracks.  What
I am looking for is a projection onto a rectangular area
like you commonly see when earth ground-tracks of orbiters
are shown (I can't think of the name of that type of
projection).  I have been told that no such thing exists,
although one would think that someone took the Apollo and
lunar orbiter data and did this at some point.  I also
saw recently someone say that the Smithsonian has some
lunar stuff on laser disk, which would imply that the
data were digitized at some point.  Anyway, If anyone knows
of the existence of such a map, I would appreciate hearing
from you.

Mike Loucks
[e-mail]
and no, I don't have any noble statement to put after my name

------------------------------

Date: Fri, 29 Jan 1993 21:07:41 GMT
From: Edmund Hack <arabia!hack>
Subject: Lunar Map
Newsgroups: sci.space,sci.space.shuttle

In article <[e-mail]> [e-mail] (Lord Vader) writes:
>I need a digital map of the moon for ground tracks.  What
>I am looking for is a projection onto a rectangular area
>like you commonly see when earth ground-tracks of orbiters
>are shown (I can't think of the name of that type of
>projection).  I have been told that no such thing exists,
>although one would think that someone took the Apollo and
>lunar orbiter data and did this at some point.

There is no "official" NASA digitized moon map available as best as I
can tell from talking to a bunch of NASA lunar science and cartography
types.  Remember that at the time the data were generated, digital
cartography was just starting.  If someone could scrape together the
data, lots of lunar science types would like to have one.
>I also
>saw recently someone say that the Smithsonian has some
>lunar stuff on laser disk, which would imply that the
>data were digitized at some point.

This is mainly surface and astronaut photography.  I have handled some
of the cartographic camera images from the later Apollo missions.  They
are 12 inch wide by many feet long B&W prints (35-40 feet or so long!).
Note that _Mars_ has better maps (and digital ones!) than the Moon.
Except for some equatorial regions, the uncertainty in object locations
and elevations is really crummy on Lunar maps.

>Anyway, If anyone knows
>of the existence of such a map, I would appreciate hearing
>from you.
>
One could take one of the commonly available maps of the moon (i.e.
National Gepgraphic Society, USGS), digitize it, dewarp it and reproject
it with some work.
--
Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
[e-mail] - I speak only for myself, unless blah, blah..
"I'm not an actor, but I play one on TV."
"Detail Dress Circuits" "Belt: Above A, Below B" "Close B ClothesMode"

------------------------------

Date: Fri, 29 Jan 1993 16:04:49 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: People dragging politics into everything (was Re: Today in 1986-Remember the Challenger)
Newsgroups: sci.space

In <[e-mail]> [e-mail] (FRANK NEY) writes:


>> I can't believe they wouldn't let you discuss on of the most tragic
>> events in recent history.

>I can.  Public schools are notorious for the collection of politically
>correct liberals infesting them.  They probably thought that the money
>would have been better spent on welfare and that NASA and the
>Challenger Seven deserved what they got.

It could as easily have been a bunch of crypto-fascist right-wingers
who thought that any discussion of something that failed would be
'unAmerican'.  But I think it most likley that they simply wanted to
try to conduct the classes that they were supposed to be conducting,
figuring that people could talk about this on their own time.

>God, I hate PC Libs!  Especially when they are in positions to
>indoctrinate our future.

God, I hate partisan ideologue fanatics!  Especially when they are in
positions to pollute an otherwise reasonable discussion.

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

------------------------------

Date: Sat, 30 Jan 93 11:41:08 EST
From: John Roberts <[e-mail]>
Subject: Shuttle tiles

-From: [e-mail]
-Subject: Re: Shuttle tiles
-Date: 25 Jan 93 07:09:06 GMT
-Organization: Auburn University, AL

-In article <[e-mail]>, [e-mail] (John Roberts) writes:
->
-> -From: [e-mail] (Gary Coffman)
-> -Subject: Re: Let's be more specific (was: Stupid Shut Cost arguements)
-> -Date: 11 Jan 93 15:48:12 GMT
->
-> -Shuttle designers... chose to use refractory silicates in the form of
-> -tiles. These are very poor conductors of heat, you can place your bare
-> -hand against one side of the tile while playing an oxy-acetylene torch
-> -on the other and not notice a temperature rise.
->
-> I think perhaps you mean a propane torch, or butane torch like Mary described.
-> Pulling some numbers from the Rogers report and elsewhere, the leading
-> edges of the Shuttle wings have to withstand heating up to 2750 F, and are
-> made of layers of graphite cloth in a carbon matrix, with the outer layers
-> chemically converted to silicon carbide. The upper fuselage, the coolest
-> portion during reentry, is only heated to about 600 F. The Shuttle has
-> high-temperature and low-temperature ceramic tiles, which are described in
-> this report as being "nearly pure glass" (I had thought they were silica),

-Not sure what the difference is,  silica/sand/glass,. Same different thing isn't
-it?.

Silica is silicon dioxide (quartz being one well-known form). Sand is
"little bitty rocks", which is frequently (but not always) composed largely
of silica. (As a counterexample, the sand at White Sands, New Mexico is
mostly gypsum.) Glass is an amorphous supercooled liquid composed of any
of a variety of substances. The definitions overlap somewhat - for instance,
I believe fused quartz would count as both silica and glass. Rapidly-cooled
rocks and metals (the latter cooled at rates of up to hundreds of thousands
or millions of degrees/s) can sometimes form glasses. In everyday usage, glass
generally refers to silica dissolved in a molten alkaline material, such that
the mix is liquid below the melting point of silica. (I've done that with an
ordinary propane torch and a homemade crucible - melt some baking soda or
washing soda, then pour in some clean, fine-grain quartz sand - the grains of
sand will sort of swirl around like "Cream of Wheat" then dissolve into the
mix, making an astonishingly poor-quality glass. In case anybody gets ideas,
be careful working with high-temperature materials, and wear safety equipment.)

Common glasses:
 # Soda-lime glass: 72% silica, 15% sodium oxide, 9% calcium oxide.
 # Soda-lead glass: (made by substituting lead oxide for the CaO and some SiO2)
 # Borosilicate glass: 80% silica, 4% alkali, 2% Al2O3, 13% boric oxide
     (Pyrex)
 # 96% silica glass: can be heated red-hot, then plunged into ice water
     without cracking. (Vycor)

I got the tile description from the Rogers report, which doesn't really
explain what it means by "glass". I'm inclined to believe they meant one
of the kinds with melting point lower than that of pure silica. One reason:
fused quartz is so difficult to work with (high melting point and high
viscosity) that if you do manage to do something with fused quartz, you *brag*
about it - you don't use the generic term "glass". Also, the lower-temperature
glass tiles are rated to 1200 F, and pure silica ought to be good up to 2950 F
(continuous exposure rating).

-> with nearly 90% of the volume being "air". The low-temperature ceramic tiles
-> are are rated to 1200 F, and the high-temperature tiles to a higher value,
-> but something below wing leading-edge temperatures.
->
-> While such temperature resistance is admirable, a properly-designed
-> acetylene torch can heat a thermally isolated object to 6000 F (~ 3300 C).

-That's great, not all  acetylene torches rate much lesss run up to 6000F.  I've
-used one myself with the tile in my hand just for kicks.

Was that a properly-adjusted oxygen-acetylene welding torch with the tip of the
inner flame touching the tile? I know some plumbers use an air-acetylene
torch that presumably doesn't get as hot as an oxyacetylene model.
It's also possible to run an oxyacetylene torch with the oxygen turned off -
you get low temperatures, and a billowing, sooty flame. (Try that in cold
weather sometime - the acetylene flame makes little fragile streamers of
soot, which float gracefully through the air and land on your clothes, at
which point they sink in and *never* wash out. :-)

Torch outfits sometimes come with a "heating" head, which might provide a
lower temperature. But that's somewhat of a cop-out - if you're going to
advertise thermal tiles as "able to withstand the heat of an oxyacetylene
torch", you'd better mean that they can withstand some reasonable application
of such a torch - not the mildest possible application.

Tell you what - you send me two intermediate-temperature (glass) Shuttle
tiles, and I'll try to melt one with an acetylene torch. If I succeed, I'll
send the melted one back to you. (Naturally, I'd have to keep the other tile
as an experimental control. :-)

Of course, melting point isn't the whole story - the rate of energy input
and energy output have to be considered. Shuttle tiles can radiate energy at
an impressive rate - but an oxyacetylene torch with a reasonable-size
welding tip can produce heat at an impressive rate too. I suspect that in
order to radiate at a rate equal to the heat production of such a torch,
the tile would have to be hotter than the melting point of the constituent
glass.

-> I wouldn't expect any trouble melting most ceramics - I've accidentally
-> melted fire bricks that I was using as a backstop for acetylene welding.
->
->>From the 1961 CRC handbook, here are some temperature ratings for ceramics
-> and other materials:
->
->   SAFE CONTINUOUS OPERATING TEMPERATURE / MELTING POINT
- [list of materials, some of which would be viable candidates for heat
-  shields.]

-lets not be more specific, let's allow some linguistic (not always the same as
-scientific) lattitude.

You're missing the point - while some people value sci.space only as a
"debating society", others are actually interested in space-related
technology and applications. The topic being discussed was spacecraft thermal
shielding, and the actual magnitudes are extremely relevant to this discussion.
I posted the temperature limits on other materials as part of the general
topic of thermal shields. Linguistics had nothing to do with it, except
insofar as everything we deal with in sci.space is words. A significant
problem with electronic networks is that once an incorrect item gets posted,
it can propagate for months or years.

However, as long as you bring up the point, being able to express yourself
so that you can be understood is vitally important. Many of the technical
problems that have arisen in the aerospace effort are due to people having
difficulty making themselves clearly understood. (I'm not referring to people
who use English as a second language - in fact, many of them use better
English than most native English speakers, because they work harder at it.)

For you unfortunate people who just can't seem to learn to write
intelligibly, there are automatic spelling checkers and style checkers.
(Yes, I'm aware that my own English is far from perfect - you folks are a
bad influence on me. :-) For an example of good communication through clear
expression, study Henry's posts - consistently at least 99% perfect.

-Paul S. Shanley

John Roberts
[e-mail]

------------------------------

Date: Fri, 29 Jan 1993 22:17:30 GMT
From: Rob Douglas <[e-mail]>
Subject: Solar Sail/Parachute/Brake
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Jonathan Deitch) writes:
|>
|>  >From: [e-mail]
|>  >Date: Mon, 25 Jan 1993 15:50:33 GMT
|>  >Newsgroups: sci.space
|>
|>  >A Solar Sail if I understand right when it arrives at its Steller destination
|>  >it becomes a Solar Parachute/Brake. Am I right?
|>
|> Yep ... you simply turn it around and use it to capture the *outward* solar
|> wind of your destination star to slow you down.
|>

Works ok if your destination is another star, but for destinations within the
solar system you will need another way to stop.

You could use rockets or something, but the point was to avoid them altogether,
so I would say, you would have to sail past your objective and then turn
around, maintaining your momentum, and head back in towards the sun.

Turning around the solar sail won't matter at all anyway, as both sides will
be able to reflect (and therefore absorb momentum from) photons.

Its the old "Which side of the aluminum foil is it better to have facing out"
argument.  Doesn't matter.  If a photon passes through one way, it passes
through the other.

--
==========================================================================
| Rob Douglas                       |  Space Telescope Science Institute |
| AI Software Engineer              |  3700 San Martin Drive             |
| Advanced Planning Systems Branch  |  Baltimore, MD  21218, USA         |
| Internet: [e-mail]      |  [phone]   [338-1592 (fax)] |
==========================================================================

Disclaimer-type-thingie>>>>>  These opinions are mine!  Unless of course
    they fall under the standard intellectual property guidelines.
    But with my intellect, I doubt it.  Besides, if it was useful
    intellectual property, do you think I would post it here?

--
==========================================================================
| Rob Douglas                       |  Space Telescope Science Institute |
| AI Software Engineer              |  3700 San Martin Drive             |
| Advanced Planning Systems Branch  |  Baltimore, MD  21218, USA         |

------------------------------

Date: 29 Jan 93 17:53:18 GMT
From: Willie Smith <[e-mail]>
Subject: Surface map of Venus
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Chris Ott) writes:
>     I'm looking for a surface map of Venus, i.e. the one returned
>from Magellan, in computer readable form.

Call the NSSDC at [phone] and ask for their catalog.  You want
the MIDR data set, which comes in volumes of 33, 18, or 5 CD-ROMs
depending on the resolution you want.  The disks aren't very
expensive, there's a _lot_ of data there, and the 'pictures' are quite
impressive.  I've got volume 1 of the 33-volume set, and once I work
on my print-to-HPLJ program a bit, I'm gonna start making wallpaper!

Willie Smith
[e-mail]
--
Willie Smith    [e-mail]    [e-mail]     "I'll make
Beelyuns and Beelyuns from the book contract and the TV show with
government funding for looking for the nothing in the void where The
Bang caused the hole in the middle of it all" Frank Hayes - Cosmos.

------------------------------

Date: 29 Jan 1993 20:27:59 GMT
From: Doug Mohney <[e-mail]>
Subject: Today in 1986-Remember the Challenger
Newsgroups: sci.space,sci.space.shuttle

In article <[e-mail]>, [e-mail] (Mary Shafer) writes:

>I work on a base named after a guy who was killed in flight test and
>all the streets I drive on are named after dead aircrew.  It's sad,
>it's regrettable, but it happens.  I still accept any ride I can in
>any airplane (high-performance types preferred since ejection seems
>superior to bailing out).

>There have been a number of studies that show that people overestimate
>the risk of rare events (airliner crashes, for example) and
>underestimate the risk of everyday events (driving, for example).
>Obviously there's more in the perception of risk than just the
>numbers.

Perceptionally/culturally/M-TV-wise:

There's a difference between dying in prime time with the world watching a
unique event verses a twenty second one-time on the local news coverage verses
a two column inch notation on page B3 of the local paper.

"Dan, let's play the video again one more time for our viewers--"

Consider the 120-plus people who died during Desert Shield/Storm operations.
More people probably died in auto accidents in the U.S. during the same time
period, but only one set will (eventually) get their own memorial.

Be discreet. Die in the middle of the wilderness in your sleep.


                    I have talked to Ehud, and lived.
  -- >                  [e-mail]                        < --

------------------------------

Date: 29 Jan 93 18:01:43 GMT
From: Willie Smith <[e-mail]>
Subject: Using off-the-shelf-components
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Edward V. Wright) writes:
>Space-qualifed today means
[...]

I forget where I saw it (maybe BIX?), but here's a couple of alternates:

    Space Qualified:    The mass of the paperwork exceeds the mass
                of the vehicle

    Man Rated:        The height of the stack of paperwork exceeds
                the designed flight altitude.

"I say, that's a joke, son!"  Foghorn Leghorn

Willie Smith
[e-mail]
--
Willie Smith    [e-mail]    [e-mail]     "I'll make
Beelyuns and Beelyuns from the book contract and the TV show with
government funding for looking for the nothing in the void where The
Bang caused the hole in the middle of it all" Frank Hayes - Cosmos.

------------------------------


To: [e-mail]
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Path: crabapple.srv.cs.cmu.edu!cantaloupe.srv.cs.cmu.edu!rochester!udel!bogus.sura.net!howland.reston.ans.net!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!kelvin.jpl.nasa.gov!baalke
From: Ron Baalke <[e-mail]>
Newsgroups: sci.space,sci.astro,alt.sci.planetary
Subject: Magellan Update - 01/29/93
Date: 29 Jan 1993 19:52 UT
Organization: Jet Propulsion Laboratory
Lines: 27
Distribution: world
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Forwarded from Doug Griffith, Magellan Project Manager

                        MAGELLAN STATUS REPORT
                           January 29, 1993

1.  It was another quiet week for the Magellan spacecraft as it
continues to operate normally transmitting a carrier signal plus
1200 bps X-band telemetry.  All temperatures are in the expected range.

2.  The spacecraft has completed 6655 orbits of Venus and is now 55%
complete on its gravity data collection in Cycle-4.

3.  Dr. Steve Saunders gave a presentation on the results of the
Magellan Venus Mapping Mission at NASA Headquarters on Wednesday,
January 27.  It will be aired on NASA Select at a later date.

4.  The Project continues its systematic archiving of science data.  A
complete validated catalog of data from the first 243-day mapping
cycle has been delivered to the Planetary Data System Central Node at
JPL and to the PDS Geosciences Node at Washington University.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Every once in a while,
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | try pushing your luck.
|_____|/  |_|/       |_____|/                     |

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End of Space Digest Volume 16 : Issue 099
------------------------------