Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_1/v11_123.txt

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Subject: SPACE Digest V11 #123

SPACE Digest                                     Volume 11 : Issue 123

Today's Topics:
             Re: SR-71:  LA to DC
            hubble telescope power
              Re: hubble telescope power
             Re: Power Economics and SPS
              Re: Funding IS The Problem
               Re: More info on Pegasus
              Re: hubble telescope power
                   Re: EMP
              Re: hubble telescope power
               Re: Rocket Info
----------------------------------------------------------------------

Date: 7 Mar 90 13:27:48 GMT
From: mstar!mstar.morningstar.com![e-mail]  (Bob Sutterfield)
Subject: Re: SR-71:  LA to DC

In article <[e-mail]> [e-mail] (John H. Kim) writes:
   ...SR-71... LA to DC in 00:68:15... target time was 00:64:00...

Yeah, those darned unforecast headwinds mess up my leg times, too :-)

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

Date: 7 Mar 90 03:31:35 GMT
From: [e-mail]  (Nick Kline)
Subject: hubble telescope power

over the plan to build several new telescopes on Mt. Graham, a nearby
mountain range.

The reason the 'scopes are controversial is because the mountain has
a diminishing number of red squirrels, a very endangered species.
Mt. Graham seems to be the only, or one of the only areas that these
squirrels are found.

The reason why I am bothering you all with this information is that in
a discussion on the 'scopes, an astronomy graduate student (speaking
on his own, I assume) said that ground based 'scopes, especially the
new variety to be manufactured by the U. of Az. are, much better than
the space based variety, and in fact are "10 to 20 times more powerful"
than the Hubble Space Telescope.

I have always heard that the HST would be MUCH more powerful than any
existing optical telescopes (cause it'd be in space).  Is this not true?

-nick

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

Date: 7 Mar 90 14:23:28 GMT
From: unmvax!nmtsun![e-mail]  (Daniel Briggs)
Subject: Re: hubble telescope power

In article <[e-mail]> [e-mail] () writes:
>[A good comparison of the merits of HST vs. large ground based scopes.
>Several other follow ups on the same theme.]
>So, which is better?  I don't tend to see either one going out of
>use anytime soon!

People are quite correct when they say that there are some programs that
are much better done with ground based telescopes, and that there is some
data that simply cannot be had by any other means than HST or an equivalent.

But but this into a $$ perspective.  The Keck ten meter telescope was
originally funded for something about $80 million.  (I think.  My memory
has proved faulty before!)  It is going to run a bit more expensive than
they had hoped, but that is still a good order of magnitude.  I have no
idea what the current price tag is on Hubble (Henry?), but it is in the
many billions class.

The moral I derive from this, is:  Space is very expensive.  Any astronomical
observations that _can_ be made from the ground, _should_ be made from the
ground.  It is much less expensive that way.  (The pleasant facts of life
that keep space junkies like you and I in business, is that there are many
interesting observations that simply _can't_ be made from the ground.)

-----
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: 7 Mar 90 17:14:54 GMT
From: helios.ee.lbl.gov!ncis.tis.llnl.gov![e-mail]  (Scott Finfrock)
Subject: Re: Power Economics and SPS

I can provide a couple of numbers that might be of interest
here.  I spent about a year working on a study of the extent
to which an SPS could be built out of lunar materials (results
were published as the vol.6, no. 1, 1986 issue of Space Power -
a small study but still interesting reading, check it out).

Some conclusions of the study:
1) A 5 GW SPS would weigh about 60,000 metric tons.
2) More than 99% of this could be lunar material.

Note that at current space shuttle capabilities/rates this
would take over 1000 launches at half a billion a pop
(unsubsidized cost).  It would also take about 100 years.
Obviously the shuttle is overkill for just lifting hunks of metal
and something could be gained from economy of scale but I
really doubt you would get more than an order of magnitude
improvement.  And that still only gets you to LOW Earth orbit.
(The Europeans and other commercial launch endeavors, BTW,
simply lack the raw weight lifting cabability required by a project
of this size).

The study estimates a factor of 50 cost savings for using lunar
materials.  Frankly I think that would be a pretty hard number to
substantiate but assuming it is correct then we begin to get
reasonable numbers.  The factor of 50 however assumes that all
necessary space based mining, processing, transportation, and
fabrication facilities are already in place.  A mighty big
assumption!  An enormous amount of machinery would be required
to build a 20 sqare mile structure (even in space) and if the
whole cost had to be factored into a single SPS it would
never fly (sorry about the pun).

The moral of the story is, IMHO, if you want SPS to be a reality
or even a possibility then support the space program.  The sooner
we get some materials processing and fabrication facilities in space
the sooner we will have a chance of convincing the powers that be
of dedicating some real money in this direction.


A side note:  most of the technology assumed in the study was
available.  Yes it would be expensive to take prototype technology
up to the production stage but I believe this would not be
significant when compared to the transportation costs.

substans
--

                      -Scott Finfrock-

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

Date: 7 Mar 90 23:43:56 GMT
From: thorin!homer![e-mail]  (Jonathan Leech)
Subject: Re: Funding IS The Problem

In article <[e-mail]> [e-mail] (Jim Bowery) writes:
>He is, after all, the person who coincidentally materialized to denounce
>my posting of "Fun Space Fact #1: Launcher Development Costs" just as
>all my subsequent messages to the space news/digest started "disappearing"
>without an explanation or bounce-back even though all my other network
>communications have been going through without any problem whatsoever.
>(Yes, I've made "-request"s for an explanation to no avail.)

    First NASA assassinated George Koopman.  Now there's a conspiracy
to prevent Bowery from posting.  I can hardly wait to see the next
plot unveiled.
--
    Jon Leech ([e-mail])    __@/
    ``One never knows... Deacon now wants to conduct population
      explosion tests *underground*.'' - Molester Mole

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

Date: 7 Mar 90 05:21:18 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: More info on Pegasus

In article <[e-mail]> [e-mail] (Mary Shafer (OFV)) writes:
>>to first flight.
>
>Not quite correct.  The mating problems were discovered _before_
>any flight tests were conducted.  That is, until the Pegasus was
>correctly mounted, the B-52 wasn't even moved.  I should point out
>that the mating problems were caused by the Pegasus, since it didn't
>fit as it should have.

The people at OSC were under the impression that their rocket had been
deisgned right and that it was the mating pylon's fault, not theirs.  It is
really hard to assign proper blame in cases like this. :-)

>Also, numerous electrical problems in the Pegasus have caused quite
>a bit of delay in the program.  Some of these were discovered _in_
>flight, much to everybody's dismay.
>
>The source of my information is post flight briefings and status
>reports from OSC and involved NASA team memebers.

After rechecking sources more carefully i do find that there were internal
problems on the rocket.  However, they were apparently 'quick fix' types, while
the mating and the interface computer have been drawn

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

Date: 7 Mar 90 07:04:07 GMT
From: agate!sag4.ssl.berkeley.edu![e-mail]  (Herman L. Marshall)
Subject: Re: hubble telescope power

In article <[e-mail]> [e-mail] (Nick Kline) writes:
>
  [stuff deleted about red squirrels and Mt. Graham]
>
>... an astronomy graduate student (speaking
>on his own, I assume) said that ground based 'scopes, especially the
>new variety to be manufactured by the U. of Az. are, much better than
>the space based variety, and in fact are "10 to 20 times more powerful"
>than the Hubble Space Telescope.
>
>I have always heard that the HST would be MUCH more powerful than any
>existing optical telescopes (cause it'd be in space).  Is this not true?

There are several ways in which the HST will be much more powerful
than ground-based telescopes and other ways in which its functions
cannot be duplicated on the ground.  These uses stem from it
being in orbit, to be sure, but for three reasons 1) that images
are less blurred when one doesn't have to look through the atmosphere
and 2) UV observations from 1200 angstroms to about 3200 angstroms
simply cannot be done from the ground simply because the atmosphere
absorbs this radiation, and 3) the atmosphere causes intensity
variations that would not occur when observed from orbit.

These points being stated, there are several types of observation
that HST can make better than existing telescopes:

1) UV flux imaging and spectroscopy - The mirror of HST is many times
bigger than that of the International Ultraviolet Explorer, the only
other orbiting UV telescope.

2) High angular resolution imaging - The angular resolution is limited
by the optics, not the atmosphere, to about 0.1 arc seconds.  So far,
the best ground-based imaging that has been achieved is around 0.3
arc seconds and that is with sophistocated active optics and still
requires an excellent site.  When HST was designed, 1 arc second
seeing was considered excellent (and still is at most sites).

With high resolution, the spectrometers can achieve higher spectral
resolution and the cameras can detect fainter stellar images.

3) High speed photometry - One instrument is dedicated to taking
photometric data that cannot be achieved from the ground.

Because of the small mirror size (by today's standards, of course),
HST is *not* more useful for certain observations, such as detecting
or measuring spectra of faint resolved sources such as galaxies.

Herman L. Marshall
Space Science Laboratory
U. California, Berkeley

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

Date: 7 Mar 90 14:33:24 GMT
From: zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!stdb.jhuapl.edu![e-mail]  (Jim Meritt)
Subject: Re: EMP

In article <[e-mail]> [e-mail] (Tim Maroney) writes:
}In article <[e-mail]> [e-mail] (Tim Maroney) writes:
}>}It would also take a pretty large hydrocarbon explosion to create EMP.
}
}In article <[e-mail]> [e-mail] (Jim Meritt) writes:
}>accidently.
}>
}>If you are trying, it doesn't.  You do have to doctor the charge a bit, though.
}
}How so?  A friend who is a well-known hard SF author with a degree in
}physics told me (and put in one of his books) that any sufficiently
}powerful explosion will cause a shower of Compton electrons from the
}upper atmosphere, which is what fries electrical circuits and is what
}we call EMP.  Is there some additional requirement on the
}characteristics of the blast?  (I may have misunderstood him, of
}course, but I did ask him about the subject the last time we had
}dinner, and he confirmed his original statement.)

You cheat.  Put some of the alkali metals in with the charge.  Stuff
ionizes real easily/well.  Use magnetohydrodynamic effects (the charged
stuff and motion from the blast) (along with trailing wires) to create the
pulse.  Read about it a few years ago in Aviation Leak.  Concerned
a non-nuclear artillery shell with EMP.  A nuke does it with brute force.
Ain't gonna get it by accdent chemically (usless a REAL accident!)

Opinions expressed are solely those of the author, and do not necessarily
represent those opinions of this or any other organization.  The facts,
however, simply are and do not "belong" to anyone.
[e-mail]  - or - [e-mail]  - or - meritt%aplvm.BITNET

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

Date: 7 Mar 90 06:03:00 GMT
From: tahoe![e-mail]  (Art Johnson)
Subject: Re: hubble telescope power

In article <[e-mail]> [e-mail] (Nick Kline) writes:
>over the plan to build several new telescopes on Mt. Graham, a nearby
>mountain range.
>
>The reason the 'scopes are controversial is because the mountain has
>a diminishing number of red squirrels, a very endangered species.
>Mt. Graham seems to be the only, or one of the only areas that these
>squirrels are found.
>
>The reason why I am bothering you all with this information is that in
>a discussion on the 'scopes, an astronomy graduate student (speaking
>on his own, I assume) said that ground based 'scopes, especially the
>new variety to be manufactured by the U. of Az. are, much better than
>the space based variety, and in fact are "10 to 20 times more powerful"
>than the Hubble Space Telescope.
>
>I have always heard that the HST would be MUCH more powerful than any
>existing optical telescopes (cause it'd be in space).  Is this not true?
>
>-nick

Depends on the sense of the word 'power.'  In terms of resolving
power, i.e., fine angular resolution, the HST will certainly
beat any other game in town for a long time, simply because it will
be well above the atmosphere and its light-distorting properties.
(To say nothing of its claim to having the most nearly perfect large
telescope mirror ever built)!

And being above the atmosphere likewise gives the Hubble instrument
access to light of all wavelengths.  That's a big plus for many
observing programs.

But in terms of light gathering power (largely a function of sheer
primary-mirror "acreage") the existing and soon-to-be-built giant
telescopes on earth's surface will still likely win out. Granting
that the HST will not be subject to the atmospheric attenuation of
starlight, and granting further that well-nigh perfect optics allow
a fainter threshold magnitude than 'ordinary' optics...even so, giant
new telescopes like the Keck in Hawaii will reveal fainter objects.
Furthermore, the advent of 'adaptive optics' will mean that future
earth-based telescopes can even approach the resolving power of the
HST, although probably not match it.

So, which is better?  I don't tend to see either one going out of
use anytime soon!

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

Date: 6 Mar 90 19:03:31 GMT
From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!ux1.cso.uiuc.edu!uxh.cso.uiuc.edu![e-mail]  (John E. Prussing)
Subject: Re: Rocket Info

In article <[e-mail]> [e-mail] (Russ Brown) writes:
>>
>>I'm preparing a simple programming assignment for my students and I wonder
>>if someone could give me some figures.  Does anyone have a rough estimate of
>>mass of a rocket (esp. Saturn V)?  How about fuel capacity?  How about
>>a conversion factor between kilograms of fuel and thrust (in Newtons)?
>>--
>Heres some stuff from "Bound for the Stars", Adelman & Adelmand, Prentice-
>Hall, 1981. (Chapter 5)
>
>- One pound of hydrogen and oxygen burning for one second exerts 456
>pounds of force. This gives it a 'specific impulse' of 456 seconds.
>"Hydrogen-Oxygen is the highest specific impulse of any chemical
>combination of fuels in use today".
>
=-=-=-=-=-=-=-=-=--=-=-=-
Specific impulse is simply a measure of the rocket's exhaust velocity,
not the thrust.  A specific impulse of 456 s corresponds to an exhaust
velocity of 4469 m/s.  How much thrust is produced depends on the
mass flow rate also.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
John E. Prussing                             Internet: [e-mail]
Aeronautical & Astronautical Engineering
University of Illinois at Urbana-Champaign    Bitnet: jep@uiucuxh

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

End of SPACE Digest V11 #123
*******************