Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_0/V15NO069.TXT

Internet Message Format | 1993-07-13 | 24KB

Date: Tue,  4 Aug 92 05:11:39
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #069
To: Space Digest Readers
Precedence: bulk


Space Digest                Tue,  4 Aug 92       Volume 15 : Issue 069

Today's Topics:
           A 12 mile tether that generates 5000v? (2 msgs)
          Energiya's role in Space Station assembly (3 msgs)
                            ETs and Radio
          ReEe: aA 12 mile tether that gernerates 5000v?
                         Red-blooded ET's : )

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
    "Subscribe Space <your name>" to one of these addresses: listserv@uga
    (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 4 Aug 92 05:46:56 GMT
From: "Michael C. Matthews" <[e-mail]>
Subject: A 12 mile tether that generates 5000v?
Newsgroups: sci.space

In article <samw.712636367@bucket> [e-mail] (Sam Warden) writes:
>[e-mail] (Richard A. Schumacher) writes:
>
>>Not applicable: efficiency won't come into it unless you try to extract
>>power from this long skinny generator. A static voltage will be created
>>without any worry about efficiency.
>
>Extracting power: now, that's the real question.  I understand quite
>well how a static p. d. is induced, but not at all how anybody's going
>to get power out of these things, the way folks are talking about.
>From whatever ion current the ends can pick up?

That's right.  The circuit is completed through the ionosphere.  The
electron guns on the Orbiter spew electrons out into the plasma.  The
charge travels down the magnetic field lines to the upper atmosphere
at the magnetic pole, where the plasma densities are sufficiently high
to allow the charge to "jump lines". From there, it follows the upper
field line back to the satellite, completing the circuit.  If you want
to use this current, you put your load between the lower end of the
tether and the electron gun.

>What kind of _usable_
>output are these things predicted to be capable of?

This all depends upon the current carrying capacity of the ionosphere.
This is really an unknown; one of the prime objectives of the TSS-1
mission is to quantify this.  It is a function of the plasma density,
the strength of the magnetic field, the resistance in the tether, and
the quality of the plasma contact that can be made at each end of the
tether.  The TSS-1 mission uses rather primitive plasma contact
methods -- an electron gun on the Orbiter and electrically conductive
paint on the satellite -- so large currents are not anticipated.  We
are hoping for up to 500mA, and the electron guns will support up to
750mA (which is, therefore, the most we will see unless the main
engine bells and assorted other exposed metal in the payload bay
provide an unanticipatedly high amount of contact).  It is hoped that
future tethered satellite missions will use more sophisticated means
of plasma contact (such as the hollow cathode, which continuously
releases small amounts of argon gas to enhance the plasma environment
around the cathode), which could allow one to tens (or more) of amps
of current to flow through the tether.  It is conceivable that kilowatts
or even megawatts of power could be generated (at the expense of orbital
angular momentum, of course).
--
Mike Matthews, Tether Dude    +------------->   [e-mail]
"Got the Shuttle on a String"  \_ Now accepting NeXTMail via KlugeNet(TM)!
Lockheed-ESC                  |
Houston, TX                   |          *** WILL HACK FOR FOOD ***

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

Date: 4 Aug 92 06:07:33 GMT
From: "Michael C. Matthews" <[e-mail]>
Subject: A 12 mile tether that generates 5000v?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Andrew Haveland-Robinson) writes:
>
>In article <[e-mail]> [e-mail] writes:
>
>>The 5000 volts are induced by the Earth's magnetic field as the spacecraft
>>orbits. The same principle in using magnets to enduce a voltage when you
>>pass a magnet through a coil of wire.
>
>I can see that this will work, though it's practicality may be limited
>as it would start to slow down the shuttle if any serious power could
>be drawn.
>
Absolutely! TANSTAAFL.

>Could be modified to form a magnetic vacuum drag 'chute I suppose!

Yes... but you can also use it as a magnetic drive.  If you reverse
the current flow (by applying power to push electrons out the top
instead of allowing them to flow out the bottom), the tether becomes
the armature of an electric motor instead of a generator, and you can
raise your orbit.  The combination of these two modes (power
generation and propulsion) gives you an extremely efficient battery
(actually, more like a flywheel, in that it converts electrical energy
to angular momentum and vice versa).  This has been proposed for use
on the space station for energy storage -- you could use excess solar
power on the sunny side of the orbit to raise your orbit with the
tether, and then use the tether to generate power (and lower the
orbit) on the dark side.

A former boss of mine (an ex-TSS guy) who now works on space station
actually did propose this a couple of years ago, but the idea was
rejected as too risky (since it depended on an unproven technology).
--
Mike Matthews, Tether Dude    +------------->   [e-mail]
"Got the Shuttle on a String"  \_ Now accepting NeXTMail via KlugeNet(TM)!
Lockheed-ESC                  |
Houston, TX                   |          *** WILL HACK FOR FOOD ***

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

Date: 3 Aug 92 10:27:04 GMT
From: [e-mail]
Subject: Energiya's role in Space Station assembly
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] writes:
> In article <[e-mail]>, [e-mail] (Gerald Cecil) writes...
>>[e-mail] writes...
>>> The cross plane maneouver from 51 degrees down to 28.5 degrees has an
>>> enormous penalty in payload.  This is why you will NEVER see a Soyuz at
>>> SSF orbit unless it is on Energia.  The payload penalty will drop Energia's
>>> delivered payload to around 50,000 pounds.  I do not know the dynamics and
>>> this estimate is based on what I have read in generalities regarding that
>>> Energia could at best only deliver a Soyuz to SS Freedom. Anybody have
>>> Delta V numbers for such a plane change?
>>

Forgive me for being a naieve European, but it seems to me that the obvious way
of using an Energia (or several) to get the Space Station launched, and
avoiding the problems of launching into several different orbital inclinations,

is to build an Energia launcing platform at KSC. This would inevitably be
cheaper than the many shuttle launches needed to lift the same mass as one
Energia, and the added infrastructure would allow for much more rapid (and
cheaper) expansion of the SS. It would also give the CIS much needed export
money and would seal the links between US and CIS space engineers.

Somehow I suspect that politics will not allow this to happen, but I'd guess
this to be the optimum engineering solution.

But then I don't work for NASA or ESA...


--
================================================================================
Dave Clements, Oxford University Astrophysics Department
================================================================================
clements @ uk.ac.ox.vax            |  Umberto Eco is the *real* Comte de
dlc      @ uk.ac.ox.astro        |           Saint Germain...
================================================================================

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

Date: 3 Aug 92 14:23:18 GMT
From: [e-mail]
Subject: Energiya's role in Space Station assembly
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] writes:
> In article <[e-mail]>, [e-mail] (robert.f.casey) writes...
>>Ok, so there is a big penalty launching an Energiya from 57 degrees and
>>changing orbital planes, but could we have them ship a complete (unfueled)
>>Energiya rocket to Kennedy and we launch it from there?  Do we have any
>>launch pads that could hancle it?  Or taken out of mothballs?
>
> There are no pads that can handle an Energia class bird at KSC besides LC 39-A
> and LC 39-b which are Apollo/Shuttle pads.  Plans were made in the original
> layout for LC 39-c,d but they were never built.  Also the VAB would have to be
> extensively modified to handle integration of Energia which is much larger
> (wider) than the Shuttle/Apollo.

Energia, like most of the CIS launchers, is, I believe, a horizontally
assembled stack, so many of the large infrastructure costs, like the VAB, are
reduced.

> From an infrastructure standpoint, which is
> much of your costs in putting any HLV in service, it is cheaper to bring back
> the Saturn V for launching heavy payloads of any type from KSC. Thanks for
> the correction on the Inclination of Skylab. Dang that impresses me even more
> that the S V could do that to 50 degrees inclination!
>

Someone else brought up the question of shipping Energias to KSC. The Anotonov
225 transporter, the largest cargo place yet, was specifically designed to
shift chunks of Energia around, so you could just fly them in to KSC. Rather
easier than barging them in as we are told happened with the SV.

I have to say that this is another example of the good planning that went in to
the design of old USSR space projects. They designed these things to be used a
lot, and made it easier in the long term.

--
================================================================================
Dave Clements, Oxford University Astrophysics Department
================================================================================
clements @ uk.ac.ox.vax            |  Umberto Eco is the *real* Comte de
dlc      @ uk.ac.ox.astro        |           Saint Germain...
================================================================================

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

Date: 3 Aug 92 20:27:10 GMT
From: Bruce Watson <[e-mail]>
Subject: Energiya's role in Space Station assembly
Newsgroups: sci.space

In article <[e-mail]| [e-mail] writes:
|the correction on the Inclination of Skylab. Dang that impresses me even more
|that the S V could do that to 50 degrees inclination!

There is not as much penalty by launching into a highly inclined orbit--just
the loss of delta V from not taking full advantage of the earth's rotation.
The big loss comes from changing from one inclination to another while
in orbit.



--
 __________________________________________________________________________
|[e-mail]|    "Another Case of too many scientists and     |
|Bruce [e-mail]> [e-mail] (Fred Christiansen) writes:

   Not necessarily so, if you do your homework carefully.  I've talked with
   contractors re what they pay the

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

Date: 4 Aug 92 01:01:39 GMT
From: Gary Coffman <ke4zv!gary>
Subject: ETs and Radio
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>>>Now subtract out all Population II stars, no heavy elements like iron...
>>
>>I mentioned iron for two reasons. First, it's necessary for oxygen
>>transport via the blood.
>
>Tell it to the crustaceans, which use copper instead.

Copper works, but it's not as efficient (2X worse), and copper's elemental
abundance is much lower.

>>Second, and this is opinion, it's needed
>>for the planet to have a significant magnetic field to redirect energetic
>>radiation from the planetary surface...
>
>The bulk of the radiation shielding on Earth is from the atmosphere, not
>the magnetic field.  Unquestionably the field is useful, but it's far
>from essential.  (Note that life on Earth has survived many field
>reversals, during which the field is more or less absent temporarily.)

True, but very high mutation rates occur during the field's absence.
Indeed a field that comes and goes might be necessary for rapid evolution.

>>>>subtract out all systems that don't have a planet in the liquid water zone,
>>The potential liquid water zone of a G star like ours is roughly from
>>near Venus orbit to somewhat beyond Mars orbit given specially designed
>>planets in the various places. Now on the solar system scale, that's a
>>small range of distances.
>
>Two planets inside it and one a near miss is "small"?  Sounds adequate
>to me.  There is no reason to believe that our solar system is unusually
>heavily populated in its inner regions, and indeed considerable reason
>to believe that it is fairly typical.  Based on what we know now, most
>any planetary system around a reasonable star should have at least one
>planet in the liquid-water zone.  The major uncertainty is whether
>that planet will be the right size for its location.  The odds of that
>aren't 100% by any means (Earth hit, Mars missed), but they aren't one
>in a million either.  One in two?  Maybe one in ten if you're a pessimist.

Sample of one. All reports of extrasolar planets have been super Jovian.
We don't know if planets in the liquid water zone are likely or not.
Certainly as a percentage of total solar system volume, the liquid water
zone is small. Other stellar types also have liquid water zones of different
extents.

>>... the accretion process, the remelt, the second
>>cooling, and finally the out gassing of water vapor and methane that
>>formed the primordial atmosphere took about 1/3 the life of the solar
>>system to occur. (At least according to popular theories of planetary
>>formation)
>
>Please cite references.  My recollection is that the system is dated
>at 4.5-5 GYr old, and life on Earth is dated back to 4GYr at least.
>Life -- simple life -- appeared quickly on Earth, probably as soon as
>it was cool enough.  (This is another encouraging sign, although it
>might have been a fluke.)

My understanding is that the sun is 10-15 billion years old and Earth
is around 4.5-5 billion years old. That may be wrong.

>>The great extinction, due to oxygen liberation, took another
>>4 billion years, before oxygen based life became dominant. I think we
>>can safely assume that intelligent life would require the energetics
>>only possible to oxygen breathers.
>
>I concur that you *probably* need a high-energy chemistry such as that
>of oxygen, and there are no other good bets evident.  (The halogens are
>comparatively rare elements for fairly fundamental reasons, oxygen is
>quite abundant for the same reasons.)
>
>However, again I'd like to see references for the time scale.  Animal
>life based on oxygen has been extant and probably dominant for most of
>the history of life on Earth, I believe.  What took a long time was
>the transition to vertebrates, not to oxygen.  Superfically this doesn't
>change the line of argument much, since intelligent invertebrates don't
>seem very likely either.  The important difference is that we're now
>dealing with a transition whose timing doesn't seem to be constrained
>by fundamentals of physics.

Yeah, you're right. The extinction was about 4 billion years *ago*
rather than taking 4 billion years.

>>... One of the greatest unknowns
>>is whether life bearing planets naturally evolve intelligent creatures,
>>or whether that's a rare accident. We don't have any data to support
>>either position very well.
>
>Agreed.  It took a while for vertebrates to become intelligent here.
>An unusually long while?  An unusually short while?  Open question.
>However, note that it happened to some degree on three parallel lines
>of development:  apes, whales, and elephants.  You have to really
>stretch the point to claim that it's inordinately rare.
>
>>>>who've thought about the question say that there are perhaps 50 systems
>>>>in the galaxy that may have life as we know it.
>>>References, please...
>>One of Sagan's books quoted this figure...
>
>If memory serves, that number was for communicating civilizations at roughly
>our current level of development, not just for life.  Whether this is the
>total set of interest depends on whether you assume a relatively short
>lifetime for such civilizations, as Sagan did.  More to the point, he
>assumed that interstellar distances were an impassable barrier, and that
>communication was the only issue.  Wrong.

I'm also only talking about intelligent life advanced enough to communicate
with us. That likely means that they are in a state of development within
minus 50 years to plus maybe 1000 years. If technical civilization progresses
as I suspect, they'll either be dead or so advanced that the methods they
use to communicate would be so radically different from ours that neither
of us would recognize the other's signals.

>>>The only argument against extraterrestrial life/intelligence that strikes
>>>*me* as being particularly telling is the Fermi Paradox:  if they're out
>>>there, why didn't they colonize this planet long before we evolved?

After thinking about it a bit more I have another reason. Perhaps they
consider it more trouble than it's worth. a Dyson sphere or Ringworld
would give them vastly more living space without having to leave home.
If they aren't particularly fast breeders, they simply may have not
faced the necessity to coming our way. Yet. (Watch the Skies!)

Gary

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

Date: 4 Aug 92 06:25:55 GMT
From: "Michael C. Matthews" <[e-mail]>
Subject: ReEe: aA 12 mile tether that gernerates 5000v?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>> I can see that this will work, though it's practicality may be
>limited
>> as it would start to slow down the shuttle if any serious power
>could
>> be drawn.
>>
>
>
>I would hardly call it "limited practicality" when you can change
>orbit to a lower one by storing the orbital energy in a battery for
>later reuse (less entropies bill) for reboost to higher orbit.
>Reaction mass need only be used for recharging this "orbital battery"
>after some number of cycles.
>
>It might also be useful for re-entry. Maybe add on a small electric
>thruster to make it a bit quicker.

Not very quick, though, unless you intend to throw away the tether and
the end mass... it takes quite a while to reel it back in.
>
>And you could move cargo (slowly) to higher orbits. But you probably
>want something that won't mind spending a bit of time in the Van
>Allen Belts...
>
You would likely not get to the Van Allen Belts, since tether
electrodynamics depends on the plasma of the upper atmosphere to
complete the electrical circuit.  If the atmosphere is too thin, you
can't get good current flow.  So, you probably wouldn't get out of low
earth orbit, unless you can keep your perigee at a couple of hundred
kilometers and just raise your apogee until you can fire an apogee
kick motor (or do a lunar gravity assist) to raise your perigiee, but
that would take a REALLY long time unless you can run hundreds of amps
or more through your tether.
--
Mike Matthews, Tether Dude    +------------->   [e-mail]
"Got the Shuttle on a String"  \_ Now accepting NeXTMail via KlugeNet(TM)!
Lockheed-ESC                  |
Houston, TX                   |          *** WILL HACK FOR FOOD ***

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

Date: 4 Aug 92 00:42:23 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Red-blooded ET's : )
Newsgroups: sci.space

In article <0eS=[e-mail]> [e-mail] (David O Hunt) writes:
>
>> I mentioned iron for two reasons. First, it's necessary for oxygen
>> transport via the blood. Second, and this is opinion, it's needed
>> for the planet to have a significant magnetic field to redirect energetic
>> radiation from the planetary surface. Now iron is the result of supernova
>> explosions. Population II stars formed *before* supernovas became common
>> enough to supply heavy elements.
>
>I'll buy the iron argument about magnetic fields, though I think that
>some other light metal might work...I'm admittedly ignorant about geomagnetics,
>but isn't it the currents in the core rather than the composition of
>the core?

The iron serves to concentrate the field, same as any electromagnet. There
are other ferromagnetic materials, but they are based on *rare* earth
elements. Being rare they are unlikely candidates. The whole idea of
rejecting Population II stars is that they were the first formed and
lack the heavier elements that are formed by core burning to completion,
up to iron, and heavier elements formed in supernovas. Population I
stars have heavier elements than hydrogen mainly because of dispersion
from novaed and supernovaed Population II stars.

>As to requiring iron to carry oxygen - NONESENSE!  Spock did it with
>copper!  :)  Seriously, the horseshoe crab has _copper_ based blood.
>Magnesium, among other light metals, could also work (don't know the
>exact energetics, alas...shouldn't have slept through chem! :)  And
>why do we assume it must be a _metal_ carrying the oxygen - there are
>non-metals with oxygen-affinity.

Iron has twice the reactivity with oxygen as copper and is twice as
efficient in oxygen transport. Iron is also in greater elemental
abundance than copper. While it's possible that elements other than
iron could serve for oxygen transport, ruthenium and osmium are in
the same group, they are likewise rare. Iron is the stable end
product of light element fusion, as found in stars, and some heavy
element fission. It has the best chance of being involved in life
simply because it has the right properties and is more common than
the others which are formed by the same processes in stars.

>> The great extinction, due to oxygen liberation, took another
>> 4 billion years, before oxygen based life became dominant. I think we
>> can safely assume that intelligent life would require the energetics
>> only possible to oxygen breathers.
>
>What about other bi-elemental gasses?  Cl2 may be too energetic, but we
>can't assume not...the main problem I see to this is the relative
>abundances of the elements.  Perhaps N2?

I think Cl and Fl can be ruled out for the reason that they form much
stronger bonds than oxygen. That's why flouro and chloro carbons are
so stable. Life processes depend on a delicate balance of competing
energies. The switch from oxygen to Cl or Fl would require changes in
every reaction needed for life. Fl-Si life may be possible in a very
energetic environment, but Cl-C or Fl-C life is unlikely.

>> >Also, why insist on it being life as we know it?
>>
>> Because we wouldn't recognize any other kind. Any lifeform not based on
>> carbon chemistry would be very strange indeed.
>>
>> Gary
>Maybe, maybe not.  We may not understand its biology, but a lithium
>skeleton lying on the ground of an extra-solar planet might be a clue.

If we recognized it as a skeleton and not some odd mineral formation.

>And I highly suspect, given numerous examples of convergent evolution on
>earth, that similar structures would evolve elsewhere.

Bipeds with bilateral symmetry are likely candidates for various reasons.
The details could vary widely however. If the planet were of significantly
different mass, the creatures might look very different. See Niven's
Neutron Star.

Gary

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

End of Space Digest Volume 15 : Issue 069
------------------------------