Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_1/V16NO148.TXT

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Date: Fri, 12 Feb 93 10:24:00
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #148
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 12 Feb 93       Volume 16 : Issue 148

Today's Topics:
                    Advanced Solid Rocket Program
                  Are Landsat Satellites receivable?
                        Challenger transcript
                         Fred is dead again.
                              hilarious
                           In Memorium, RAH
                        kerosene/peroxide SSTO
                        leading-edge anonymity
              Looking for orbital elements of the moon *
                    Mir/SSF(Fred) Combo Mission..
  New Russian Solar Sail results - data to help you see it (2 msgs)
                      parachutes on Challenger?
                             Polar Orbit
                 Russian Solar Sail Results (3 msgs)
stellar sizesRe: Electronic Journal of the ASA (EJASA) - February 1993)
                         Units and Star Trek

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Date: Sat, 6 Feb 1993 04:16:02 GMT
From: Henry Spencer <[e-mail]>
Subject: Advanced Solid Rocket Program
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>>(And then there's George Koopman's offer to fund development of a hybrid
>>SRB-replacement motor privately if NASA would promise to buy it after
>>successful testing...  NASA, of course, ignored it.)
>
>Not to be rude, but did he also promise a deliverable price equal to or below
>the current SRBs?

Not sure, although I wouldn't be at all surprised.  Amroc's hybrids are a
lot less hassle to make than solids; for one thing, no explosion hazard
is involved.

>Doesn't make much sense to promise something which would cost more per unit
>than current tech, unless it does something wondermarvelful.

You don't consider throttling and instant shutdown at any time useful?
Or better performance and greatly reduced handling hazards?  Not to
mention reduced pollution, much less abrasive exhaust plumes, and the
ability to do a pad abort in the event of ignition failure...
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: 5 Feb 93 22:26:44 GMT
From: Jordin Kare <[e-mail]>
Subject: Are Landsat Satellites receivable?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (John Schmidt) writes:
>In <araichel.728587393@cser> [e-mail] (Alan Raichel) writes:
>
>>    I have seen some pretty high resolution pictures taken by
>>the Landsat satellites....

I'm currently dealing with the Landsat 7 and Landsat Advanced Technolgy
folks on behalf of DOE.  If I were not seriously jetlagged right now I
could dig out some more details, but off the top of my head...

Landsat 4, 5 are operational.  6 is due to launch Real Soon Now.  7 has
been contracted for.  Technology for 8 is being developed.

>Hi there.  LANDSAT-4 and LANDSAT-5 both have a "Thematic Mapper" sensor
>capable of 28.5 meter pixel size, about two orders of magnitude better
>than the NOAA platform.  That comes to about 94 feet per pixel in terms
>of dimension.

6 will also have a 15 meter resolution panchromatic ("black and white")
band for sharpening the TM images.  7 will have a second instrument called
HRMSI ("Herm-see"), the High Resolution MultiSpectral Imager, with 5-m
resolution in multiple color bands and 2.5 meter resolution panchromatic.

>>    I know that hobiest can recieve APT and HRPT data from the
>>NOAA satellites.  What I was wonder if it is possable for people to
>>recieve the data from the Landsat satellites?
>LANDSATs transmit back via very-very high speed links, measured in
>multiple megabits per second.

75 and 150 Mbits/s standard

Usually those signals are beamed back to
>specific receiving stations, or (when capacity permits) up to the TDRS
>(Tracking and Data Relay Satellite) platforms.

L6 will transmit only to high-data-rate
ground stations, if I recall correctly.  L7 will
have several modes of ground transmission, plus a mode for transmission
through TDRSS.  One of the ground transmission modes will be a relatively
high power, low rate mode compatible with HRPT-class ground stations.

 Those are, of course,
>very special wideband links that, additionally, are encrypted.  Why??
>Well, since 01-October-1986, the data transmitted back from the LANDSAT
>series birds is owned fully by the EOSAT (Earth Observation Satellite)
>Corporation.  Not only is this data transmitted back to sites they
>own/operate in the US, but a couple of dozen sites abroad.  These foreign-
>based sites basically fall under somewhat different ownerships, and they
>sign a cooperative agreement with EOSAT to not only be able to download the
>data but to make it available to worldwide LANDSAT users.

Landsat is being returned to joint NASA/DoD control with L7, and I believe
distribution agreements for L6 are being negotiated.  The Landsat Remote
Sensing Act of 1992 mandates this new arrangement, and requires that
data be available to gov't and educational users (and maybe all users; not
sure) for the cost of filling the request... i.e., essentially copying costs.
This may result in at least some data being sent unencrypted.

>These foreign (and domestic receiving) stations are quite expensive
>sites, the least of which involves a 21 meter full-sky-tracking
>receiving dish for an antenna.

21 meter sounds awfully big.  21 feet (6+ meter) perhaps?  The L7 "economy"
downlink is likely to require something like a 3 meter dish.

>And, if I am correct, the satellites themselves were (until maybe
>recently) owned by the Federal Government, and the data they sent down
>to Earth was the part owned by EOSAT.  I'm not altogether sure if that
>changed recently, if EOSAT took over ownership of the whole thing.

As noted, the Feds took back ownership for future landsats.  DOD is responsible
for the satellite itself, and NASA for the "ground segment" -- receivers,
distribution and storage of data.

>>1. Do the Landsat satellites continously transmit pictures of what is
>>below them, or does it only take pictures of schedualed areas?
>(here, it's about >9:35 AM CST give or take a few minutes).

Landsat is sun synchronous, with equatorial crossing at 9:45 a.m., so it sees
_everything_ at about that time of day.  L7 may be moved to 10:30 a.m. to
match NASA's EOS AM1 satellite; this is currently a subject of debate.
Landsat can do either direct transmission or store images via tape recorders
for later playback; obviously the latter capability limits the area that
can be imaged.

...

>>3. Are the specifications on frequencies that the satellite transmit
>>on, and data rates, and formats available to the public?

    They almost certainly are available, since the Landsats conform
to various NASA standards for TDRSS, etc.  However, I don't know where to
get details.

>As far as this hobbyist is concerned, I think I won't be able to afford
>the reverse engineering; I'd be better off spending the money (up to
>$5000 for a full-scene digital image) to just buy the desired data from
>EOSAT.  I hope that legislation will eventually make it much cheaper for
>places like Universities and governmental entities to purchase this kind
>of resource; it's expensive enough right now.  (Even if my employer
>*does* spend our school's dollars to get it!)

As noted, the data will get significantly cheaper in the reasonably near
future.

>Since this system was designed beginning in the late 1970s and launched
>with your and my tax dollars in 1982/1983, (speaking strictly about the
>LANDSATs 4 and 5) I would suppose somewhere in an archive the documents
>exist.  After all, this business of privatization of LANDSAT didn't
>occur until 1986.  You can always start looking somewheres, but the idea
>of such a search could be more than most of us could handle.  Try NOAA
>and NASA facilities for a start; Goddard Space Flight Center in Goddard,
>MD. has been a key player in the LANDSAT story over the years, and so
>has the Earth Resources Lab at Stennis Space Center (Bay St. Louis, MS).
>Good luck!  I'd like to hear what you find out.
>Hope this helps.  Glad to answer this kind of question.
>John N Schmidt KD4EAI, Lab Director + 615-898-5561 M-F 1300-2230Z <7-4:30>

Ditto.

    Jordin Kare    [e-mail]

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

Date: 6 Feb 93 15:59:36 GMT
From: [e-mail]
Subject: Challenger transcript
Newsgroups: sci.space

I was reading a post entitled "Challenger Transcript" which contained the
following passage:

>> T>   A secret NASA tape reveals that the crew of the shuttle Challenger
>> T> not only survived the explosion that ripped the vessel apart; they
>> T> screamed, cried, cursed and prayed for three hellish minutes before
>> T> they slammed into the Atlantic and perished on January 28, 1986.


>> T>   Two minutes forty-five seconds later the tape ends. That's when the
>> T> shuttles crew compartment, which remained intact after the vessel
>> T> exploded over the Atlantic, hit the ocean at over 2,000 miles per
>> T> hour, instantly killing the crew.

>> T>   The tape is said to begin with a startled crewman screaming,"What
>> T> happened? What happened? Oh God - No!"  Screams and curses are heard-
>> T> several crewmen begin to weep- and then others bid their families
>> T> farewell.

The reponse which this poster received was something like, "Horse manure."
After that, there was a "my friend's uncle was on an Apollo moon shot, so I
have access to classified info" bit of fencing and the article ended.

Well, I remember reading a book entitled, "Challenger," or something like that,
which outlined the accident and the subsequent investigations which followed,
particularly the medical investigation made by NASA's Joseph P. Kerwin (Skylab
fans should remember him as the guy who did weightless acrobatics to "Also
Sprach Zarathustra" on the first mission.).  Dr. Kerwin noted that the
emergency oxygen systems beneath four of the seven seats in the crew module had
been activated and that one had been used for almost three minutes.  These
systems must be manually operated.  This implies that as many as four
crewmembers were conscious after the explosion of the main propellant tank.
The second thing which was noted by Kerwin was the damage to the crew module
itself.  The reconstructed cabin shows all the signs of impact damage (with the
ocean) but none of the damage one would expect from heat and blast.  This is
consistent with the evidence of high-speed camera footage of the event, which
clearly shows the orbiter being torn apart by aerodynamic stress after being
"jerked" upward into a high angle-of-attack by the explosion.  The force of the
nearly 3000 mph winds, even at that altitude, were enough to tear the wings and
fuselage apart.  These same recordings show the box-like crew compartment of
the orbiter emerging from the blast, following the trajectory of the bird at
the time of the explosion.

As far as the content of the "transcript" goes...  Will the original poster
send me info about this?  Sources?

Aaron Christopher
Ball State Univ.

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

Date: Sat, 6 Feb 1993 04:17:29 GMT
From: Henry Spencer <[e-mail]>
Subject: Fred is dead again.
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>... Director of OMB Panetta is proposing (and Clinton seems
>to be accepting) a $12 billion NASA budget. The money is to come from
>ending Freedom and ASRM.

Latest news:  Clinton has denied any plan to terminate Fred, although
he has not ruled out cutting it back.
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: Sat, 6 Feb 1993 17:59:20 GMT
From: Tesuji <[e-mail]>
Subject: hilarious
Newsgroups: sci.space,sci.astro,alt.privacy

X-Anon-To:sci.space,sci.astro,alt.privacy

The response the Challenger transcript has gotten
has been hilarious.

If you guys can't joke about bone cancer,
childhood leukemia, and facing certain
horrifying death, then you guys don't have
the perspective to call yourself adults.

Get a life.  Get *seven*.  Ha ha.

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

Date: Sat, 6 Feb 1993 00:52:43 +0000
From: Anthony Frost <[e-mail]>
Subject: In Memorium, RAH
Newsgroups: sci.space


  >> Venus is a cloud-covered hellhole; better RAH should get
  >> something with a view of open space.

  > Perhaps one of "the cool green hills of Earth"?

  > Then again we might want to name one of the clefts of Valles
  > Marineris "Smith-Heinlein", or some future Lunar habitation
  > "Garcia-O'Kelly-Davis- Heinlein pressure."

I think he would have settled for Heinlein Square in Luna City. Must be time
to read "The Man Who Sold the Moon" again...

        Anthony

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

Date: Sat, 6 Feb 1993 14:03:37 GMT
From: Paul Dietz <[e-mail]>
Subject: kerosene/peroxide SSTO
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:

>>> Higher molecular weight in the exhaust is what hurts the exhaust velocity,
>>> but it actually helps on thrust...
>>
>>Is this right?   The coefficient of thrust doesn't depend on molecular
>>weight, only on pressures, throat area and specific heat ratio k...
>
> Hmm, I think you're right.  Somewhere I picked up the belief that there
> was a dependence, but I'd never taken a hard look at the equations to
> try to find it, and it doesn't seem to be there.


Perhaps the belief came from the comparatively low thrust of many
LH2/LOX engines.  However, this stems more from the fact that these
engines are intended for upper stages, and so are optimized more for
high Isp in vacuum rather than high thrust in atmosphere, and so have
comparatively small throat areas to increase the pressure ratio of the
nozzle.

Engines with denser propellants can get by with smaller pumps for
a given chamber pressure, though.

    Paul F. Dietz
    [e-mail]

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

Date: Sat, 6 Feb 1993 14:05:01 GMT
From: david niebuhr <[e-mail]>
Subject: leading-edge anonymity
Newsgroups: sci.space,sci.astro,alt.privacy

In article <[e-mail]> [e-mail] writes:
>[e-mail] (Tesuji) writes:
>
>>X-Anon-To:sci.space,sci.astro,alt.privacy
>>
>>I believe that fast adapters are accepting
>>anonymous postings as the next step in personal
>>freedom in communication.
>
>Perhaps but it also guarantees that a large number of people won't
>bother reading what you have to say.  If you're not willing to take
>responsibility for waht you write, why should it be given any credence?
>

Notice how in the original post, the author made written comments about
doing physical violence to those that possibly disagreed.  If he put
his name to that article, he could possibly be arrested.

Actually, the whole article sounded like it was written by a punk kid
who thought that he/she was being heroic by sounding off like he/did
but was afraid to put his name and correct address on his post.

Dave
--
Dave Niebuhr      Internet: [e-mail] / Bitnet: niebuhr@bnl
Brookhaven National Laboratory Upton, NY 11973  (516)-282-3093

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

Date: Sat, 6 Feb 93 07:22:11 GMT
From: Ryan Korniloff <[e-mail]>
Subject: Looking for orbital elements of the moon *
Newsgroups: sci.space

I am looking for, if they exist, orbital elements (2-line) for the moon.
If they exist or you know where I can get them please let me know by email.
Thank you.


         --- Ryan Korniloff
         --- [e-mail]

--
         --- Ryan Korniloff
         --- [e-mail]

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

Date: 6 Feb 93 07:30:23 GMT
From: "Michael K. Heney" <[e-mail]>
Subject: Mir/SSF(Fred) Combo Mission..
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Dave Michelson) writes:
>
>Recently, there has been much talk about launching satellites into polar
>orbit from near the poles (Poker Flats, Alaska or Ft. Churchill, Manitoba)
>in order to maximize the payload to orbit.  I checked out my usual sources
>(Introduction to Space Dynamics and Fundamentals of Astrodynamics) but
>couldn't find anything concerning the effect of launch site latitude
>and desired orbit inclination on the maximum payload...

For a purely polar orbiter, you want 0 velocity in the east-west direction.
That means from any latitude other than one of the poles, you have to kill
the eastward velocity you pick up from the earth's rotation.   This is highest
at the equator, which is why you want to launch payloads from the equator
if possible - you pick up the maximum advantage from the rotating earth.

I *believe* that for any given orbital inclination (at least 0-90), you're
best off launching from that latitude.  (Actually, I think that for the
90-180 degree inclination range, you're also better off at the corresponding
latitude, in this case, 180-inclination).  Disclaimer - I'm not an
orbital mechanic, but I've seen one on TV.

--
Mike Heney                |   Senior Systems Analyst and     |  Reach for the
[e-mail]   |  Space Activist / Entrepreneur   |  Stars, eh?
Kensington, MD (near DC)  |     * Will Work for Money *      |

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

Date: Sat, 6 Feb 93 12:11:13 CST
From: [e-mail] (Yaron Sheffer)
Subject: New Russian Solar Sail results - data to help you see it

Hi Glenn and everybody...
Am wondering if there are any predictions available for Austin TX
to see this Mir/Mirror combo? The sky is just about to clear over here...
Thanks!!!
-Yaron

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

Date: 6 Feb 1993 18:42:09 GMT
From: Claudio Egalon <[e-mail]>
Subject: New Russian Solar Sail results - data to help you see it
Newsgroups: sci.space

From what I could read, the solar sail now is flying separetely from
the Progress. My question is was it supposed to be this way or the
separation occured because of a problem with the solar sail and
Progress ship?

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

Date: Sat, 6 Feb 1993 04:02:45 GMT
From: Henry Spencer <[e-mail]>
Subject: parachutes on Challenger?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>>The weight penalty would be substantial, and ejection seats are not
>>entirely safe to have around.  They're also rather bulky.
>
>Not safe, as in explosives in the crew cabin for a week or more?  Or unsafe as
>in tempremental and likely to punch a hole in the roof?

Ejection seats contain both explosive charges and rocket motors.  Neither
is something you want to have in the cabin unnecessarily.  No big deal if
proper precautions are taken... but it only takes one mistake to kill someone.

One reason why the escape pole was chosen over a rocket-assisted bailout
system was the hazards of having rockets stored in the cabin.
--
C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
effect since OS/360.                    |  [e-mail]  utzoo!henry

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

Date: 5 Feb 93 21:41:36 EST
From: Chris Jones <[e-mail]>
Subject: Polar Orbit
Newsgroups: sci.space

In article <[e-mail]>, davem@ee (Dave Michelson) writes:
>In article <[e-mail]> [e-mail] (Chris Jones) writes:
>>
>>As I said yesterday (in <[e-mail]>), for polar orbit the latitude of the
>>launch site doesn't matter (except that a launch site at either pole would have
>>lots of longitude lines along which to launch in order to achieve polar orbit).
>I would like to hear from someone who can actually cite a text or paper that
>deals with the matter in more detail.  In a recent issue of Financial Post

>magazine, an article dealing with a proposal to reactivate the National
>Research Council's Churchill Rocket Range for commercial launches of polar
>orbiting satellites quotes the director of aerospace studies at the University
>of Toronto as saying that there is a definite advantage to launching near
>the poles rather than the equator.  Furthermore, the advantage is commercially
>significant in a competitive launch services environment.

Well, one of us (you, me, or the "director of aerospace studies at the
University of Toronto") is mistaken.  I don't have a detailed reference, but
everything I can recall says that there's no advantage to being near the poles
to launch into a polar orbit.  Looking up Space Exploration in a not-so-recent
(1977) Encyclopaedia Brittanica (v 17, p 360), I read

"In projecting a satellite into Earth orbit, the launch vehicle is invariably
tilted after liftoff in an easterly direction.  Launching to the east is done
to take advantage of the Earth's eastward surface velocity.  This rotational
surface velocity is about 1500 feet (450 metres) per second at the equator and
1370 feet (400 metres) per second at the latitude of Cape Kennedy.  It would be
perfectly possible to launch a satellite on a westerly orbit, but an additional
2000 feet (600 metres) per second would be required for an orbit of the same
altitude compared with an easterly one.
     If the satellite is launched in a northerly or southerly direction, a polar
orbit is obtained.  The easterly surface velocity launch advantage is lost"

(The Israelis have launched at least two satellites toward the west, to avoid
having the launch appear to be an attack on their neighbors to the east).

It's just a guess, but I think it would be more advantageous to look for a high
mountain from which to launch rather than a northerly latitude.  That way you'd
have less of that thick air to punch through.
--
Chris Jones    [e-mail]

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

Date: Sat, 6 Feb 1993 03:33:23 GMT
From: Glenn Chapman <[e-mail]>
Subject: Russian Solar Sail Results
Newsgroups: sci.space

    I posted this in hast and it appears to not have made it in earlier
sorry:


     For those interested in watching the Russian Solar Sail
experiment here is some more useful information.  The experiment
started with the Progress TM-15 cargo craft, undocking from the Kvant
module port at the rear of the Russian Mir space station about 12 midnight
PST on Feb 4th.  The Progess was rotated about its axis
and the kevlar/aluminum solar sail was spun out to be held ridgid by the
rotation force.  The sail have ellipse like holes forming 8 missing
"spokes" to help shape the structure.  One announcement stated that
shortly after it was deployed and had gone over Europe the sail was
detached from the from the Progress.  Thus what was observed here
in Vancouver was 3 objects on Thursday, the solar sail, which was
flashing at about 2 sec intervals, followed 4 minutes later by the progress
and Mir (separated by 5 degrees from each other).  Observations today
had the sail appearing some 13 minutes before Mir, consistant with an
estimate I have of orbital decay for the very light sail.  I
estimate the sail will appear about 53 minutes infront of Mir for
areas on saturday, Feb. 6th.  By the way on Radio Moscow they announced
that the sail, when reflecting on an area, will illuminate a ground area
4 km in diameter.

                            Glenn Chapman
                            Simon Fraser U.
                                                        School Eng. Science.
                            [e-mail]

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

Date: Sat, 6 Feb 1993 04:11:48 GMT
From: Glenn Chapman <[e-mail]>
Subject: Russian Solar Sail Results
Newsgroups: sci.space

     Some additional information for those looking for the Russian
solar sail experiment (Znamya).  For those who have not seen the solar
sail it appears as a bright yellow flashing object some time in front
of the Mir space station.  On Feb. 4 at Vancouver, B.C. Canada it
appeared at 6:37, about 4 minutes ahead of the Mir station, which
was itself preceeded by a dimmer object - which probably is the
Progress TM-15.  The 5 degrees separation of Mir and the Progress
corresponds to about 35 km (21 miles) - about what I would expect
in this experiment.  The Znamya's lead those was 1800 km - certainly
this could only come from rapid orbital decay.  On Feb. 5th it came
some 13 minutes (+/- 1 minute) in front of Mir according to another
observer here , at 7:04 am (in an area not covered by the overcast sky).
My estimates suggest now that for Saturday it will be between 39 and 53 minutes
ahead of the Mir station values.  This corresponds to a drop of 95 Km
in altitude, to about 300 km, in just two days.  This is not unreasonable
for such a low mass object.  The Mir space station, with about the same
cross sectional area as this 20 metre diameter solar sail, falls about
1 km per day unless corrective action is taken.  The much lighter solar
sail has less energy to lose, and hence would fall faster. My initial
estimate was that the Progress/Znamya combination would fall about
20-30 km per day - Progress masses 5 Tonnes at this point, about 5% of
Mir stations mass).  Hence this is falling much faster than that estimate
and tends to confirm the statement that Znamya was separated from the
Progess.  At this rate it will burn up in just a few days.  The reason
why the solar sail is flashing is probably it has now lost its shape
and is tumbling without the mass of the Progess to stabilize it.
In some ways this makes it much easier to spot - it is just that the
time estimates are now way off from those of Mir station.
     I would have to say that more than anything else this seeing this
string of 3 objects coming one right after the other in orbit
and the flashing sail was one of the most impressive sights I have
ever seen in observing satellite objects.  If you get the chance
try to see it.


                            Glenn Chapman
                            Simon Fraser U.
                                                        School Eng. Science.
                            [e-mail]

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

Date: Sat, 6 Feb 1993 18:28:12 GMT
From: Leigh Palmer <[e-mail]>
Subject: Russian Solar Sail Results
Newsgroups: sci.space

In article <[e-mail]> Glenn Chapman,
[e-mail] writes:
>[very useful information regarding the orbit of the jetisoned Znamya]

Thanks for that information, Glenn. While it didn't clear the clouds here
in Burnaby, it may have helped someone else to see the sail. It would be
very interesting to hear more reports of sightings of Znamya over the few
days it has left in orbit, and wouldn't it be spectacular to witness its
reentry?

That's actually more than a rhetorical question. The large drag to mass
ratio of this object puts it into a class with few members, notably the
Echo balloons of the sixties. Were reentries of those objects witnessed
or monitored by radar? Were any fragments recovered? We have a lot of
real estate up here in Canada between 49 and 51 degrees, with a
relatively high probability of being the reentry site, second only to
Russia I suspect. I doubt that there are motors on Znamya to deorbit it,
so we'll sit here and wait for it to drop in our laps.

>     I would have to say that more than anything else this seeing this
>string of 3 objects coming one right after the other in orbit
>and the flashing sail was one of the most impressive sights I have
>ever seen in observing satellite objects.  If you get the chance
>try to see it.

I agree, but that will probably be impossible with this particular string
of objects again. For those interested, however, the NOSS 2-1 and NOSS
2-2 satellites, which fly in formations of three, can often be seen - if
one has the software to predict them. These all fit comfortably into the
field of view of binoculars, and are quite an exciting find for any
observer. I can imagine the UFO stories which might arise from a chance
observation of these birds.

Leigh

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

Date: Sat, 6 Feb 1993 03:33:01 GMT
From: [e-mail]
Subject: stellar sizesRe: Electronic Journal of the ASA (EJASA) - February 1993)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail]
(Jeff Bulf) asks:

>         Revolving around a small yellow star between the celestial paths
>     of a crater-scarred world called Mercury and our blue-white Earth lies
>     the planet known as Venus.
>
> As I understand it, isn't the Sun a considerably larger-than-average star?
> Recent articles in Astronomy have gone into this some. Apparently average
> is around red-dwarf size.

Well, Sol is a bit more massive than the average.  Still, that makes very
little difference in diameter.  Taking the example of a K-5 main sequence
star with effective T = 3500 K and luminosity 1/10 that of the Sun, it
still has a diameter that is ~93% of the Sun's diameter.  There just
isn't much variation in stellar diameter along the main sequence although
there is considerable variation in mass.  Even a monster O-5 with 50
solar masses glowing 200,000 times as bright with effective T = 50,000 K
will have a radius of only 6.5 times the Sun's radius.  An A-0 such as
Vega is less than 3 times the Sun's diameter.  For a star to be half
the diameter of the Sun on the main sequence it would have to be a
tiny little M-5.

As mass is added to stars they mostly just get more tightly bound by
self gravity.  They have to go off the main sequence and start fusing
elements in shells as well as their cores before they can bloat up into
monsters 200 times the size of the Sun.  But since their off-main-sequence
lifetimes are so short compared to the time they spend on the main
sequence, these beasts don't add much to the "average" size over time.

Also, I suspect there was some literary license being used in the "around
a small star" line.

-Bill Gawne,  Space Telescope Science Institute

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

Date: 6 Feb 93 16:02:31 GMT
From: [e-mail]
Subject: Units and Star Trek
Newsgroups: sci.space

Someone writes...

In article <[e-mail]>, [e-mail] (Tom) writes:
> From: Otto Maddox <[e-mail]>
>
>>     How long would it take a ship traveling at Warp 1 to get to a
>>planet that is 60 light years away?
>
> I'm afraid I can only work in MKS or CGS.  Can I get some units on 'warp'?
>
> -Tommy Mac
> ------------------------------===========================================
> Tom McWilliams               |Is Faith a short '  `      '   *.;     +%
> [e-mail]       |cut for attaining    +    .      '
> [phone] -or- 353-2986 |  . knowledge? ;"'       ,'    .   '     .
> a scrub Astronomy undergrad  |      *     ,    or is it just  .       .
> at Michigan State University |   ';   '        * a short-circuit?   ,
> ------------------------------===========================================

If you use the "old" warp factor, it would take 60 years.

Aaron Christopher
Ball State Univ.

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End of Space Digest Volume 16 : Issue 148
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