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Subject: SPACE Digest V13 #595

SPACE Digest                                     Volume 13 : Issue 595

Today's Topics:
              Re: 2001 and NASP
                SR-71
        Re: Tethers (was Re: Laser launchers)
               Re: Saturn V and the ALS
       POTENTIAL MAJOR SOLAR FLARE WARNING CANCELLATION
             Re: Building Infrastructure
                Meteor Showers
          Re: What comes after Fred's death?
 Re: Request For Discussion: sci.space.moderated (questions/answers)

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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----------------------------------------------------------------------

Date: 15 May 91 13:54:25 GMT
From: eru!hagbard!sunic!mcsun!ukc!icdoc!syma![e-mail]  (Nick Watkins)
Subject: Re: 2001 and NASP

From article <[e-mail]>, by [e-mail] (James Davis Nicoll):
> In article <[e-mail]> [e-mail] writes:
>>   Has anyone noticed the remarkable resemblance between
>>the proposed National Aerospace Plane and the space transport
>>in 2001: A Space Odyssey?
>     Wasn't the space plane in 2001 nuclear powered (NERVAesque,
> if I recall correctly)?
You do indeed. It also wasn't single stage to orbit, but had a
recoverable first stage, and a launching rail (described in the book).
More like Saenger than NASP or HOTOL I'd say.

Nick
--
Dr Nick Watkins, Space Plasma Physics, Univ. of Sussex, Brighton BN1 9QH, UK
JANET: [e-mail]        BITNET: [e-mail]

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

Date: 19 May 91 00:33:17 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!menudo.uh.edu!nuchat!lobster!n5abi![e-mail]
Subject: SR-71


 The June issue of Popular Mechanics includes an article on the SR-71 and
mentions that NASA is putting three back in service for research. Does
anyone know where they will operate from? I would guess Edwards but the
article never says.

-----------------------------------------------------------------------
Gene Kennedy - Ham Radio Operator, N5ABI - lobster.hou.tx.us!n5abi!gak
-----------------------------------------------------------------------

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

Date: 19 May 91 17:57:12 GMT
From: news-server.csri.toronto.edu!helios.physics.utoronto.ca!aurora.physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Tethers (was Re: Laser launchers)

In article <[e-mail]> [e-mail] (Walter Dnes    ) writes:
>[e-mail] (Christopher Neufeld) writes:
>
>>    No, that's not right. If the tether is rotating, resembling the spoke
>> of an invisible wheel rolling around the surface of the Earth, then the
>> velocity of the tip drops to zero briefly.
>>
>     "If the tether is rotating..." W-H-O-A !!!!!!!!!!!!!!!!!!
>
>  [ Physics 101 analysis of an untapered rotating tether deleted ]
>  [ Conclusion, not surprisingly, is that an untapered tether
>    would break                                                  ]
>
   Well, now do it again with the assumption that the area of the tether
is a function of distance from the centre, and that the area at any
point is sufficient to exert a tension equal to the total apparent
weight of the tether it must support plus the payload apparent weight,
plus some safety margin. You can manage a rotating tether with an area
taper of between 2500 and 8000, or a radius taper of less than 100, with
commonly available bulk materials like Aramide or HP-PE (don't ask me
what this stands for). These figures are for a 1000 km tether, peak
acceleration of about 10 gravities.
   It turns out that the longer the tether the better. The taper scales
with the orbital velocity squared, so a longer, higher tether doesn't
flare out in the middle so much. Further, the tip acceleration is
smaller, so the tether can handle larger payloads. Remember that the
payload of the tether is actually measured in Newtons, and the higher
the peak acceleration the smaller the mass which can derive that
acceleration from a fixed magnitude force.
   Make it a 2000 km tether and the area taper drops to about 1500 for
HP-PE, with peak acceleration of about 5 gravities. 4000 km tethers
bring the area taper down to about 600, accn about 2 gravities. Note
that in these figures the 500 m/s velocity of the surface of the Earth
is included.

>     This is one half of the tether. Newton's 3rd law implies that
>the other portion has identical force *IN THE OTHER DIRECTION*.
>Also 5 times the earth-surface weight of the tether.
>
   Whoa there! Back to your 101 notes. The tension force is not
multiplied by two for the two arms of the tether! A rope under one
Newton of tension applies that force in both directions, by Newton's
third law. What that really means is that it doesn't matter whether
there's another arm on the tether or it's nailed to an asteroid, the
tension at the centre (or the surface of the asteroid) is that required
to hold up one arm of the tether. Think of it this way: I have a rope
running over a pulley with a 10N weight on each end of the rope. What
is the tension in the rope? It's 10 Newtons. Now, I cut the rope at the
pulley and tie the cut ends to the ceiling. What's the tension in each
rope? It's 10 Newtons.

>Walter Dnes
>[e-mail]             [e-mail]


--
 Christopher Neufeld....Just a graduate student  | There no place like $FC58
 [e-mail]    Ad astra! | They're $FF69-ing my
 cneufeld@{pnet91,pro-cco}.cts.com               | every word! Send for a
 "Don't edit reality for the sake of simplicity" | free $A56E.

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

Date: 19 May 91 00:45:58 GMT
From: usc!samsung!umich!ox.com!hela![e-mail]  (Allen W. Sherzer)
Subject: Re: Saturn V and the ALS

In article <[e-mail]> [e-mail] (Frank Crary) writes:

>If returning a broken satellite to Earth for repairs "lost money" why
>are insurance companies willing to PAY NASA to do this?

Simple: NASA charges the insurance company a highly subsidized rate.
Suppose you have a sattellite which can be fixed up and sold for
$100M. NASA says they will recover it for $75 million so you say
'fine, do it'. NASA spends upwards of a billion dollars doing
the actual work. The insurance company makes money and the taxpayers
absorbe the loss.

That's what I mean by 'lost money'.

>As for repairing a satellite on orbit, what sort of "dry dock" are you
>thinking of.

Standards exist for putting field replaceable units in some satellites
(like Solar Max). Initially all it would be is a pressurized facility
to replace these units and do minor repair. Eventually as the market
grows it will make sense to add capability. Eventually they will
do integration with parts sent from Earth and made on the moon.

>Building and operating a station of this size, as well as building and
>operating the Orbital Manuvering Vehicle could easily cost FAR more than
>just throwing the satillites away when they fail.

Of course it will. Just like the government lost lots getting the
airline industry started with the Kelly Act. What it does do is to
reduce the incrimental costs so that individual enterprises can be
profitable. Eventually, the maintenance of the infrastructure can
be handed off to the private sector. Also remember that a station
like this would be involved in lots of other activites. Any one of
these if saddled with everything would fail.

>>Even as we speak the DoE is doing work using a Soviet military reactor.

>The DoE has bought a soviet "Topaz 2" space nuclear reactor. They did NOT
>buy it for use.

Correct. The original poster was claiming that it would be impossible
to buy ANY space hardware. I agree it would be a bigger step to buy
a Soyuz to acutally use but it could be done.

>How will the experiment module get to the station? Unless you have an
>OMV (Which is worth having, but not trivial to build, fly and operate)

As I said, with a portion of the second or third years savings from
the Shuttle we could build an OMV.

>Also, from where will the module get power during the time it is
>in transit to the station? This will take at least a few hours and many
>payloads CANNOT be turned of in filght.

This would be a problem. I guess you are correct we would need to
send them up using the HLV; a Titan wouldn't do. Fortunatly, we
built two with about a third of the first years savings.

>>>Sure. You're going to ask people who were put on hold for close to 3 years
>>>post-Challenger to go back to the drawing board.

>>In some cases, yep.

>If NASA made a commitment to fly someone's experiment on the Shuttle, they
>have a responsibility not to jerk him around

I agree that these issues would need to be addresses in the transition.
I don't know how we would do that. However, anybody who works with NASA on
the Shuttle has already been jerked around so it should be nothing new :-)

>(e.g. by forcing him to re-
>design his experiment or constantly changing the launch data.)

No, NASA would never do that! :-)

  Allen

--
+---------------------------------------------------------------------------+
|Allen W. Sherzer |        Allen's tactics are too tricky to deal with      |
|   [e-mail]   |             -- Harel Barzilai                           |
+---------------------------------------------------------------------------+

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

Date: Sun, 19 May 91 13:53:03 MDT
From: oler <@BITNET.CC.CMU.EDU:[e-mail]> (CARY OLER)
Subject: POTENTIAL MAJOR SOLAR FLARE WARNING CANCELLATION
X-St-Vmsmail-To: st%"[e-mail]"

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                     POTENTIAL MAJOR FLARE WARNING

                          WARNING CANCELLATION

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                             May 19, 1991


ATTENTION:

     Region 6619 has now rotated beyond the western solar limb.  Major
flaring is not expected from the regions currently visible.  Flaring will
remain confined to low-level C-class events with a chance for an isolated
M-class flare.

     The Potential Major Flare Warning has been terminated.


                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

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

Date: 20 May 91 06:05:14 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Re: Building Infrastructure

In article <[e-mail]> [e-mail] (Frank Crary) writes:

>[garunteed purchase]
>The payloads should be what the government needs, in the
>orbits they need them, say in support of a major program (Lunar base?)

This begs the question: why does the government need a lunar base?

The government has two major needs in space that cannot be directly met
privately -- defense and exploration.  The purchase of launch et. al.
services to meet those needs should be determined by the Pentagon and
space explorers respectively, not by "space infrastructure" planners who
are not motivated to meet anybody's needs.


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 20 May 91 08:02:48 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Meteor Showers


Here is some info on meteor showers, and also a a couple of questions:

* What are the best theories and observations regarding the distribution
  of mass in these orbits (from the comet itself to Tungaska-sized fragments
  to dust).  Does the distribution come close to the "same mass in each
  size range" rule of thumb for asteroids?

* What is the percentage of water ice in each sized fragment?  I understand
  that dust particles contain no water, and comets themselves contain
  mostly water.  How about fragments of intermediate size -- for example,
  what was the percentage of water ice in the Tungaska fragment?


some meteor showers and their parent bodies
-------------------------------------------
_caveat_: due to informal scholarship, the perihilion figures are
  +/- 2 months, at best.  From various sources, but primarily from
  _Cambridge Encyclopedia of Astronomy_.
                                    next
shower        max    range        ZHR    parent        period  peri
------        ---    -----        ---    ------        ------  ----
Quadrantids    Ja4   Ja1-5        100    ?        ?    ?
v Pi-Puppids    Ap24  Ap21-26         60    Griggs-Skje     5.2     Au 92
                                    Oc 97
d Beta Taurids  Jn29  Jn23 - Jl5     20    Encke        3.3     ?
f Alpha Capricornids
        Au1   Jl15 - Au25     10    Honda-Mrkos-Pjd 5.28    Ja 92
                                    My97
Perseids    Au12  Jl25 - Au18     70    Tuttle 2    ?    ?
v Draconids    Oc8   Oc7-10        "high"  Giac.-Zinner    6.52    Fe 91
                                    Oc 97
Orionids    Oc21  Oc6-27         35    Haley        73    2069
Taurids        No1   Oc10 - De5     12     Encke        3.3     ?
v Leonids    No17  No14-20            1,000  Tempel-Tuttle   33.3    Oc99
Geminids    De13  De8-16         60     3200 Phaeton    ?    ?
Ursids        De21  De17-25         5    Tuttle        13.6    Jn 94


ZHR = Zenith Hourly Rate
v = variable, ZHR for perihilion
d = daytime
f = fireballs


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 20 May 91 18:53:28 GMT
From: swrinde!sdd.hp.com!caen!ox.com!hela![e-mail]  (Allen W. Sherzer)
Subject: Re: What comes after Fred's death?

In article <[e-mail]> [e-mail] (Steve Willner) writes:

>Hasn't it occurred to anyone that life sciences research (keeping a
>couple of astronauts in orbit for a year or so) can be done without a
>space station?  All that should be needed are another couple of
>shuttle orbiters, extended duration modifications (up to 30 days is
>already planned), and rendezvous capability.

I don't think it would work. First of all, you would need to arrange
schedules so that the desired orbits of all the missions are compatable.
That may or may not be a problem.

Even if this problem was solved, you still couldn't launch Shuttles
fast enough. Current plans for eight flights a year which would
keep over a third of the year unoccupied.

>[Thanks, Allen, for keeping us up to date.]

My pleasure.

  Allen

--
+---------------------------------------------------------------------------+
|Allen W. Sherzer |        Allen's tactics are too tricky to deal with      |
|   [e-mail]   |             -- Harel Barzilai                           |
+---------------------------------------------------------------------------+

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

Date: 20 May 91 17:48:03 GMT
From: munnari.oz.au!metro!cluster![e-mail]  (Raymond Lister)
Subject: Re: Request For Discussion: sci.space.moderated (questions/answers)


  >  From: [e-mail] (Tarl Neustaedter)
  >
  >  ...
  >
  >  Reasons for asking for a moderated group:
  >      1)   ...
  >      2) There are frequently *many* answers to a single question.
  >         A moderator can reduce that down to the few most concise answers,
  >         and reduce the number of repeated postings.

There is a simple non-moderator solution to this problem.  Postings requesting
information should end with something like ...

   "Do not post the answer.  Mail it directly to me.  I shall post a summary."

This works reasonably well in other groups.  Unfortunately, I doubt that
sci.space has the *collective* intelligence to make it work.

Like most people, I'd love to see sci.space moderated.  But, like most people,
I don't want to be the moderator.

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

End of SPACE Digest V13 #595
*******************