Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_1/V15NO183.TXT

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Date: Fri, 11 Sep 92 05:00:23
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #183
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Space Digest                Fri, 11 Sep 92       Volume 15 : Issue 183

Today's Topics:
                         3 booster questions
                    farthest Laser signal (3 msgs)
            FASER theory --> FASEN --- "n" (somewhat epic)
                      FASER theory -- BL aspects
                       How to build ion engine?
              Is NASA really planning to Terraform Mars?
                  One Small Modest Proposal (2 msgs)
          One Small Step for a Space Activist... Vol 3 No 9
                   Pluto Direct Propulsion Options
      Pluto Direct Propulsion Options Part II: The Silly Season
               QUERY Re: Pluto Direct/ options (4 msgs)

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

Date: Thu, 10 Sep 1992 15:59:12 GMT
From: Henry Spencer <[e-mail]>
Subject: 3 booster questions
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>[1].What makes Titan so expensive?  I would think that this would be a
>mature launch system where no one needs to masturbate the machinery before
>launch.  Is there something inherent in its properties (such as long storage
>fuel tanks?) or is it in the way the system is managed?

It has the same problem as most current boosters:  it carries very expensive
payloads that are difficult to replace, so there is great incentive to spend
lots of money on anything that might improve reliability even slightly.
There is *no limit* to how much you can spend making things a little bit
more reliable.  For example, the Titan SRB segments get elaborate attention
to ensure that even the smallest gaps between fuel and casing are found and
dealt with, even though nobody has any idea whether they really matter.
(Big ones do, and there is some speculation that the last Titan launch
failure was caused by one, but the small ones could well be harmless.)

Its cost per kilogram of payload is not grossly out of line with that of
the smaller medium boosters, especially if you discount somewhat to allow
for the fact that it's basically still a government program, burdened
by unnecessary paperwork and inefficient management.  (Commercial Titan
sales have been essentially zero.)

>[2].Atlas still goes *boom* a lot?  Is this inherent to the design of having
>two of the engines fall off and the difficulty in shutting off the fuel flow
>to these engines?

Neither.  The recent failures have been Centaur problems.  They're a bit
surprising, since the RL10 has been a very reliable engine.

>... Perhaps developing an LRB for the Shuttle will not be justified
>on its own.  Perhaps developing an HLV will not be justified on its own.
>However, if you have an HLV whose first stage will also serve as an LRB
>you could amortise development costs pretty fast.  Is there something wrong
>with this idea?

Nothing, and indeed it's not new.  The problem with developing a heavylift
booster is *there is no market*.  The problem with developing an improved
shuttle booster is *there is no market*.  People have offered to do it if
NASA would promise to buy a (successfully tested) production version; NASA
is not interested.
--
There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
mistakes, but... make *new* ones. -D.Sim|  [e-mail]  utzoo!henry

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

Date: 10 Sep 92 13:35:09 GMT
From: Rohit Sharma <[e-mail]>
Subject: farthest Laser signal
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] ("Richard Schroeppel") writes:
>>Note that radar signals have been bounced off Venus, and were
>>actually used for some mapping...
>
>I believe JPL has done interplanetary radar work as far as Jupiter.
>
>>Assuming the purpose of your question is to consider "How feasible
>>are lasers for high bandwidth, semi-private, space communication?"...
>
>Feasible.  There is intense interest in the idea, and some in-space
>experiments will fly in this decade.  (It's just possible that secret
>military systems might be operational already -- laser communications
>systems would have very tight beams that would be very difficult to
>eavesdrop on.)
>--
>There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
>mistakes, but... make *new* ones. -D.Sim|  [e-mail]  utzoo!henry

  I would be pretty sure that military systems are in place and working
since companies like General Dynamics were working on precisely the same
thing in 1963-64-65 !  Even though the lasers available then were mostly
HeNe or primitive CO2s, they had enough encouraging results to make this
project into a bigger and better funded one in late sixties.
 BTW, anybody on this newsgroup know of anybody who worked at the
General Dynamics PLant in Rochester, NY ?? (in the laser com group). I
believe the plant was moved in 1969.

- Rohit Sharma

  [e-mail]

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

Date: Thu, 10 Sep 1992 15:02:01 GMT
From: David Knapp <[e-mail]>
Subject: farthest Laser signal
Newsgroups: sci.space

Ron, would you be interested in posting some of your planetary probe inormation
to alt.sci.planetary?


--
David Knapp                                      University of Colorado, Boulder
Perpetual Student                                   [e-mail]

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

Date: 10 Sep 92 15:45:46 GMT
From: Henry Spencer <[e-mail]>
Subject: farthest Laser signal
Newsgroups: sci.space

In article <![e-mail]> [e-mail] (Michael V. Kent) writes:
>>>... lasers for high bandwidth, semi-private, space communication?"...
>>Feasible.  There is intense interest in the idea, and some in-space
>>experiments will fly in this decade.
>
>Forgive my not knowing the basic vocabulary, but is this what's known as a
>lidar (laser radar?)?  If so, the Lidar In-Space Technology Experiment is
>scheduled for a 1994 launch.

No, lidar is bouncing laser beams off uncooperative objects and observing
the reflection.  Laser communications, the subject of the discussion, is
sending them one way to a cooperative receiver.  (Well, you probably end
up going both ways, for several reasons, but in principle it could be
unidirectional.)

>>It's just possible that secret
>>military systems might be operational already ...
>
>I know work is active in this area, but has anything flown yet?

"I could tell you, but then I'd have to kill you." :-)

No, actually, I don't know either...  If they exist, they are quite secret.
--
There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
mistakes, but... make *new* ones. -D.Sim|  [e-mail]  utzoo!henry

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

Date: 10 Sep 92 05:00:38 GMT
From: "Paul M. Koloc" <prometheus!pmk>
Subject: FASER theory --> FASEN --- "n" (somewhat epic)
Newsgroups: sci.physics.fusion,sci.astro,sci.space

    FASEN; Fusion Amplification by Stimulated Emission of Neutrinos

In article <[e-mail]> [e-mail] (Barry Merriman) writes:
>In article <[e-mail]> [e-mail] (Paul L Schauble) writes:
>> TITLE: Reposting of FASER Theory

>>         Fusion Amplification by Stimulated Emission of Radiation
>>             Copyright (C) June 4, 1989  by David H. Mitchell

>[non theory deleted]

para Hypothesis?

>If resonant standing waves induce fusion reactions in a solid medium,
>you need to explain why the medium is not ripped apart first, since
>the fields required are much greater than the binding energy of the
>material. This is the obvious problem with such 'theories', and I note
>that there was no mention of how to avoid this.

The answer may be possible although NOT commercial. Use the old
"If your brakes fail, do your best to compensate by changing
direction."  As Barry points out Electromagnetic Radiation is
not likely the answer.

What is required in this case is a radiation that has little
or no cross-section for non-fusing matter, but has an
exceptionally high capture cross-section for capture by
-- and transform of -- near fusion events into fusion events.
From yesteryear, an intriging problem in astrophysics of how
to make a star pulse burn.  Could this be tied to this
hypothetical concept?  How can an exponentiating burn rate in
one portion of a star be spread within a few tens of seconds
to the whole star??  The answer could explain some of the
rhythmic energy fluctuations observed in stars.

If fusion stimulating radiation works with these characteristics
of fusion neutrinos, then perhaps P&F really do have a relatively
fast rise time and ultra sensitive neutrino detector. The
detector bit is pretty far fetched, but still worth thinking
about.

The reason I believe neutrino stimulated fusion burning may be
an important part of "real" stellar energy performance is the
following:

Consider an exponentially rising localized core burn, producing
a sharply rising enhanced flux of neutrinos.  If the stimulated
fusion capture works with the neutrino flux squared then a kind
of threshold level could be surpassed where the FASENeutrino
(FASEN) would trigger like exponentially rising burns elsewhere
until fuel conditions or temperatures shifted to lower capture
cross-sections and by the flux either dropping below -- or the
threshold climbing above -- so the FASEN pulse extinguishes.
In any event the stimulating flux most likely would NOT be
coherent neutrino flux but it may be more analogous to the
"super-radiance" of very strongly excited fluorescent material.

Now for the relatively local REAL world. (hypothesized)

Within our sun just such a massive neutrino pulse burn in the
core of the sun every 11 years would produce a jump in temperature
throughout the sun. Especially important here is that pulse
heating would happen at a magnetic/plasma saturation boundary.
This would cause super saturation of the flux generating little
PLASMAK(tm) like vacuum magnetoplasmoids (PMK) structures which
themselves generate an additional pulse fusion burn of relatively
short duration, but significant total additional energy.  Also
that energy is deposited much nearer the surface of the sun.
(This was discussed in another posting in sci.physics.fusion.)
As you recall, the vacuum magnetoplasmoids then cool their
central magnetized rings as they rise from buoyancy through the
sun's Mantle, and then move into the photosphere where they
become unstable due to pressure anisotropy and subsequently
break apart.  The remnants then wash to the surface and are seen
as "sunspots" with their trapped magnetic flux. This flux
releases the flux from the strongly magnetized Kernel ring's
remnants as energy which dissipates driving flares, etc.

>In absence of such a mechanism, you would at least need to cite
>experimental evidence that this occurs. Citing P&F hardly counts, I'd say.

Gee!  You are discounting the world's fastest FP neutrino detector?
                        :)

And just look at all that heat from 1988 solar cycle FAZEN pulse.
During this peak solar cycle a whopping sunspot count of a 55 year
high was taken.  The excess heating pulse has radiated away, except
for the extra heat absorbed by the heat trapping Pacific which
integrated the excess over the last 4 years.  A good chunk of this
heat is still stored, which is now currently sitting off California
keeping the western USA in a warm high).  However, this summer
most of the land has cooled off and the weather has come up with
more record cool days than warm ones.
                     :-)

Where's the green house effect??    "It's cloud cover, my boy --
      -- enhanced  cloud cover.

               Does Gore really believe this stuff?
             Nope! The weather doesn't FAZEN 'em a bit.
>--
>Barry Merriman, UCLA Dept. of Math, UCLA Inst. for Fusion and Plasma
>Research,  [e-mail] (Internet; NeXTMail is welcome)

Thanks Barry and David

lines by pmk@prometheus
Copyright (C) September 10, 1992 by Paul M. Koloc
+---------------------------------------------------------+**********+
| Paul M. Koloc, President, Prometheus II, Ltd.           +Commercial*
|                   Bx 222, College Park, MD 20740-0222   ***FUSION***
| mimsy!promethe!pmk        [e-mail]  ***in the***
| [phone]            promethe=prometheus           **Nineties**
+---------------------------------------------------------************

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

Date: 10 Sep 92 10:37:44 GMT
From: "Paul M. Koloc" <prometheus!pmk>
Subject: FASER theory -- BL aspects
Newsgroups: sci.physics.fusion,sci.space

In article <EACHUS.92Sep9105601@Dr_No.mitre.org> eachus@Dr_No.mitre.org (Robert I. Eachus) writes:
>
>     I'm curious.  How fast a rise time do you need, and at what
>voltage?

Later.

>  .. . I remember buying 5 KV 80 microFarad Mylar capacitors from
>Maxwell.  Only good for about a thousand shots, but a kilojoule you
>can hold in your hand is nothing to sneeze at. (You'll break your
>wrist--as I remember it they weighed about 20 pounds. :-)  They also
>made larger capacitors and firing switches for them.  I remeber
>pictures of a 50 Megajoule test.  We also used to buy 100 joule oil
>filleds by the pallet load.  A lot more wiring, but they lasted for
>years.  The only advantage of the mylar caps was an extremely low
>impedence, and they weighed a tenth as much per joule.

A BIG advantage.

>     Prices have probably gone up a lot since I was playing with high
>voltage, but putting together a Megajoule source (with a once per five
>minutes firing rate) could be done back then for under 100 thousand
>dollars.  If you can use a homopolar generator, it can be done a lot
>cheaper...

Consider also the mass.  However some inertial storage units have
high specific energy.  I would still like to see a kick CF unit to
act as an energy source refeed pulser storage for PLASMAK(tm) engines
restart.

PLASMAK(tm) formation and long life is energy efficient from the
standpoint of the ratio of the: (PMK energy)/(formation output
energy) --  or the in: (plasma nkT energy)/ (the total field
energy). And being so compact the total PMK energy is not much
compared to a the 6 to 20 gigajoules in the toroidal field coils of
a tokamak.

Relative efficiencies are by comparison to a tokamak. Cap development
at Maxwell Labs will have 10 kJ/kg specific energies.

Neato pulse lines may be developed to extend cap lifetimes and
optimize transfer energy.   Weights on a 10 megajoule bank would
be 1 metric ton --  what's needed for a 1 to 3 gigawatt generator.
It would be nice to have engines of 20 gigawatts with burst operation
to 25 gigawatts.  Even operating around 17 gigawatts each, a pair of
these can put a sizeable payload on the surface of Mars.  This
assumes we will burn p-^(11)B  (protium boron isotope eleven).  That
trip goes from earth's surface to the Martian surface using two
different propulsion generation modes. Trip times of 300 to 450
hours seem about right.

>                    Robert I. Eachus
>

+---------------------------------------------------------+**********+
| Paul M. Koloc, President, Prometheus II, Ltd.           +Commercial*
|                   Bx 222, College Park, MD 20740-0222   ***FUSION***
| mimsy!promethe!pmk        [e-mail]  ***in the***
| [phone]            promethe=prometheus           **Nineties**
+---------------------------------------------------------************

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

Date: 10 Sep 92 16:04:45 GMT
From: Ron Peterson <[e-mail]>
Subject: How to build ion engine?
Newsgroups: sci.space

Could someone please describe to me how to build a practical ion rocket
engine?

I'd like to know if it would be possible to build a micro-sized
platform that could lift itself in the air powered by a solar cell
or very small battery.  I thought that perhaps a tiny ion motor
with a solar cell painted on its exterior might be capable of
lifting itself off the ground.
[e-mail] or uunet!vicorp!ron

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

Date: Thu, 10 Sep 1992 14:59:18 GMT
From: David Knapp <[e-mail]>
Subject: Is NASA really planning to Terraform Mars?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Frank Crary) writes:
>In article <[e-mail]> [e-mail] (David Knapp) writes:
>>If you want to make your backyard unlivable, go ahead, but the second you are
>>doing things that make *everyone's* backyard unlivable, you should expect
>>a response.
>
>I'd have to disagree on two points: I don't think there is any evdence
>we are making the Earth "unlivable."

You mean ignoring any possible consequences of ozone loss and maybe even
global warming? Let's even completely ignore increasing risks of nuclear
war (from non-NATO develpment) or from nuclear disaster.  We can also ignore
steady expansionism of the populace.

Even if you ignore all the globe-threatening issues, *population* growth,
which you can *count on*, will still be one of our greatest challenges.  It
will keep growing until it simply *can't* and that only happens when world
resources, particularly in food stuffs, become steadily taxed. Don't
kid yourselves, this is *going* to happen whether you like it or agree with
it.

> In some respects, we may have
>made it a less pleasent place to live, but that is a very different
>thing from uninhabitable.


Even after you look at the population curve and make some simple extrapolations,
keeping in mind things like fossil fuel depletion in the next 50 years,
shifting agricultural zones, you do not see this?

>I hope you aren't suggesting absolute
>prefection with respect to the Earth's environment should be a
>pre-requsite to extra-planetary ventures.

I would be happy with mediocre agreement on the significant issues, which
we have not even *approached.*

>Second, since there is no live on Mars, nor anywhere else in the
>Solar System, excatly who's backyard is Mars, if not our own?

You do not know there is no life on Mars or anywhere else other than Earth.
I don't see the relevance of arguing over the label of 'back yard'.  I don't
think as a society, or even a planet, we have yet learned how to manage our
*own* planet, not even a *little*.  Because of this I don't think we are
qualified to begin applying our ignorance to anther planet.

Luckily, this will not be an issue for many years.


"/users/as-phys/knapp/.letter" 59 lines, 2558 characters
s
Send, abort, edit, or list?
Append .signature file? [y]

(re-entering cbreak mode)
End of article 22135 (of 22160)--what next? [npq]
--
David Knapp                                      University of Colorado, Boulder
Perpetual Student                                   [e-mail]

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

Date: 10 Sep 92 11:31:40 GMT
From: John Roberts <[e-mail]>
Subject: One Small Modest Proposal
Newsgroups: sci.space

-From: [e-mail] (Allen W. Sherzer)
-Subject: One Small Step for a Space Activist... Vol 3 No 9
-Date: 9 Sep 92 19:31:28 GMT

-On the plus side, station supply will mean placing a lot of
-mass into LEO, and this could make the market for launch
-services a LOT bigger, which could help reduce launch
-costs. But the way things currently are, NASA intends to use
-only the Shuttle (with its high cost) for resupply. Not only
-will this deny the advantages of a larger market but it will
-add huge costs to the Station life cycle.

-If a way to resupply Freedom could be found which didn't
-require Shuttle, the payback would be enormous. Not only
-would the larger launch markets lower costs, but non-Shuttle
-based resupply could mean that the entire Shuttle program
-can be phased out, freeing up roughly three BILLION every year.

I trust you're not trying to win political support for this proposal.
("Not only will it stop your dog barking at night and tearing up the
neighbor's garden, the Winchester cartridge will also *kill* your dog,
so you don't have to pay for all that expensive dog food!" :-)

You'll probably get a more favorable response if you wait until we have
a new dog before proposing to shoot the old dog. Concentrating on the need
for a new dog as an end in itself would probably speed the process.

John Roberts
[e-mail]

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

Date: 10 Sep 92 13:29:09 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: One Small Modest Proposal
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (John Roberts) writes:

>-Subject: One Small Step for a Space Activist... Vol 3 No 9
>-Date: 9 Sep 92 19:31:28 GMT

>I trust you're not trying to win political support for this proposal.

I am simply making two points:

1. Our current approach of worring about everything EXCEPT the cost is
   getting us nowhere.
2. Better, cheaper, faster solutions are out there. We need only allow them
   to work.

>You'll probably get a more favorable response if you wait until we have
>a new dog before proposing to shoot the old dog.

No problem. All that is needed is for NASA to:

1. Announce that they will move to cheaper station resupply should the
   private sector make it available.
2. Fairly price Shuttle flights and announce that no special consideration
   will be given it when considering alternatives.

>Concentrating on the need
>for a new dog as an end in itself would probably speed the process.

That's part of it. As I said, Freedom life cycle and Shuttle costs will
make it impossible to do anything more for the next 30 or so years. But
not only do we need a new dog, we need to insure it isn't built the old
way.

Think about it, Station resupply will more than double the current launch
market measured in pounds to LEO. That size market and constancy of
demand will make totally privately developed spaceships practical. Protecting
half that market by making it use the more expensive Shuttle wastes money
better spent elsewhere and denies us an important chance to make space
cheaper and self sustaining.

Why is space exploration the only place where wasting money is seen as
a virtue?

   Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "If they can put a man on the Moon, why can't they     |
|  [e-mail]     |  put a man on the Moon?"                               |
+----------------------226 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 10 Sep 92 13:15:22 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: One Small Step for a Space Activist... Vol 3 No 9
Newsgroups: talk.politics.space,sci.space

In article <[e-mail]> [e-mail] (Michael V. Kent) writes:

>NASA intends to use only the Shuttle for resupply ONLY until something
>better comes along.

As it currently stands Shuttle and Freedom together spend all the money
which could go toward a Shuttle replacement. NASA therefore intends
to use the Shuttle forever.

>The mistake here is thinking of the Shuttle as a launch vehicle.  It is not.

It isn't?

>A second mistake is thinking its sole mission is Station resupply.  That, too,
>is untrue.

I am not suggesting that at all. What I am suggesting is that using the
outlined approach we will have a better and cheaper overall capability.

>If Station resupply is offloaded to another vehicle, you still
>want to keep the Shuttle around for missions like EURECA, TSS, SHARE, CIRRUS,
>Hubble revisits, satellite repair, retrieving, and servicing, etc.  These
>are missions which still need to be done and that the Shuttle was designed to
>do.

Few of these missions can be cost justified using Shuttle. The ones which
can, can fly on Freedom for a fraction of the cost.

The problem with this whole arguement is that it ignores the cost of doing
anything. That mode of operation has ground us to a halt and cannot
continue if we want to go anywhere.

If you want to continue this, please provide cost justifications for
your arguements.

>Please note two things.  NASA would like to go to a 180-day rotation about
>two years after PMC (instead of 90 days).  Also, NASA plans to expand the
>station to an eight man crew (EMCC).  Plan your vehicle accordingly.

180 day rotations with twice the crew will require the exact same number
of launches and will therefore have zero cost impact.

>I like the heavy-lift idea, but I don't think they fill the mission well.

They do the job for a lot less money. What else is there?

>It seems like you're adapting a mission to the vehicle and not the other
>way around.

Exactly. That's why it is cheaper.

Think of it this way, the car I drove to work in today has four seats and
a trunk. Yet I only drive myself to work. I also have a lot of papers in
my car and a person's seat (where I keep them now) is not the best place.

So what your saying is that instead of adapting my car to the mission
(getting me to work) I should design and build a custom car with only
one seat and a filing cabinet for my papers.

I don't do that because I can't afford to. NASA should do the same for
the exact same reason.

>If you're going to
>build a new vehicle, build it to the mission requirements.  (If I were
>a station manager, I'd rather have 5 flights of 20,000 lbs each than one
>flight of 100,000 lbs.  It offers much more flexibility).

At several times the cost. No, a station manager living on a fixed budget
would prefer the far cheaper good enough solution.

>You want to use an Atlas?  The rocket that goes "boom" a lot?

Not that often. A launch escape rocket will make the vast majority of
those accidents survivable. Shuttle also goes boom and is far more
likely to kill crew (and $2 billion orbiter) when it does.

The bottom line is that this is a dangerous job and people will die.

   Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "If they can put a man on the Moon, why can't they     |
|  [e-mail]     |  put a man on the Moon?"                               |
+----------------------226 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Thu, 10 Sep 92 13:13:43 -0500
From: [e-mail] (Phil G. Fraering)
Subject: Pluto Direct Propulsion Options

Henry Spencer, net.authority, pontificates:

\It is extremely difficult to combine a reasonable payload and a manageably
/short trip time with an orbiter mission.  Pluto is *a long way away*; to
\get there in under a decade, the probe has to be fast.  Killing all that
/velocity is inordinately expensive in mass.  You really cannot do a Pluto
\orbiter in a reasonable amount of time with 1960s propulsion technology,
/which is what all currently-planned missions use.
--
\There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
/mistakes, but... make *new* ones. -D.Sim|  [e-mail]  utzoo!henry


Just out of curiosity, is there a way to convince them to use post-early-
1960's technology, like an ion drive of some sort?

--
Phil Fraering [e-mail] where the x is a number from 1-5.
Phone: [phone] SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560
If seven maids with seven brooms swept for half a year,
do you think, the Walrus asked, that they could make it clear?
I doubt it, said the Carpenter, and shed a bitter tear.
---------
"NOAH!"                        \           \ Lewis Carrol
"Yes lord?"                     > Bill Cosby, The Story of Noah
"HOW LONG CAN YOU TREAD WATER?"/

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

Date: Thu, 10 Sep 92 13:16:40 -0500
From: [e-mail] (Phil G. Fraering)
Subject: Pluto Direct Propulsion Options Part II: The Silly Season

hs>It is extremely difficult to combine a reasonable payload and a manageably
hs>short trip time with an orbiter mission.  Pluto is *a long way away*; to
hs>get there in under a decade, the probe has to be fast.  Killing all that
hs>velocity is inordinately expensive in mass.

dm>Aerobrake?

dm>                 Support U.N. military force against Serbia

dm>-- >                  [e-mail]                        < --

Since Nick hasn't said it yet, I will...

Lithobrake!

--
Phil Fraering [e-mail] where the x is a number from 1-5.
Phone: [phone] SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560
If seven maids with seven brooms swept for half a year,
do you think, the Walrus asked, that they could make it clear?
I doubt it, said the Carpenter, and shed a bitter tear.
---------
"NOAH!"                        \           \ Lewis Carrol
"Yes lord?"                     > Bill Cosby, The Story of Noah
"HOW LONG CAN YOU TREAD WATER?"/

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

Date: 10 Sep 92 13:57:54 GMT
From: Doug Mohney <[e-mail]>
Subject: QUERY Re: Pluto Direct/ options
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Tom A Baker) writes:
>>Could you clarify whether this craft is supposed to just flyby (a la
>>Voyager) or is truly a Pluto "orbiter"? ...
>
>It is extremely difficult to combine a reasonable payload and a manageably
>short trip time with an orbiter mission.  Pluto is *a long way away*; to
>get there in under a decade, the probe has to be fast.  Killing all that
>velocity is inordinately expensive in mass.

Aerobrake?

                 Support U.N. military force against Serbia

  -- >                  [e-mail]                        < --

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

Date: 10 Sep 92 15:39:27 GMT
From: Craig Helmuth <[e-mail]>
Subject: QUERY Re: Pluto Direct/ options
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Doug
Mohney) writes:
>In article <[e-mail]>, [e-mail] (Henry Spencer)
writes:
>>
>>It is extremely difficult to combine a reasonable payload and a manageably
>>short trip time with an orbiter mission.  Pluto is *a long way away*; to
>>get there in under a decade, the probe has to be fast.  Killing all that
>>velocity is inordinately expensive in mass.
>
>Aerobrake?
>
>                 Support U.N. military force against Serbia
>
>  -- >                  [e-mail]                        < --
>

At that temp, the term might be better spelled "Aerobreak"!    ;-)


Craig Helmuth        [e-mail]

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

Date: 10 Sep 92 23:48:38 GMT
From: Ron Baalke <[e-mail]>
Subject: QUERY Re: Pluto Direct/ options
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Doug Mohney) writes...
>In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>
>>It is extremely difficult to combine a reasonable payload and a manageably
>>short trip time with an orbiter mission.  Pluto is *a long way away*; to
>>get there in under a decade, the probe has to be fast.  Killing all that
>>velocity is inordinately expensive in mass.
>
>Aerobrake?
>

We don't have that much practical experience with aerobraking into orbit
capture - it has never been attempted before.  If given the chance, Magellan
will perform a number of aerobrake maneuvers through the atmosphere of
Venus to circularize its orbit, but the uncertainty is so great that we
can only estimate that it will take from 100 to 300 days.  Pluto does have a
tentative atmosphere, but we know so little about it.  A flyby mission will
help to enlighten us.  If you haven't noticed already, the basic blueprint
for planetary exploration is to do a flyby first, then follow it up with
an orbiting mission, and then follow that up with a lander.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Anything is impossible if
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | you don't attempt it.
|_____|/  |_|/       |_____|/                     |

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

Date: Thu, 10 Sep 1992 16:13:38 GMT
From: Henry Spencer <[e-mail]>
Subject: QUERY Re: Pluto Direct/ options
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>>... Pluto is *a long way away*; to
>>get there in under a decade, the probe has to be fast.  Killing all that
>>velocity is inordinately expensive in mass.
>
>Aerobrake?

In what? :-)  Pluto does have an atmosphere of sorts at the moment, but
I'd guess it's too thin to do much aerobraking in, even if we knew its
properties well enough to plan an aerobraking mission, which we don't.
And we'd have to kill a lot of velocity; Pluto is roughly 150 km/s-years
away (how's that for strange units? :-)), so for a reasonable trip time
we're talking about killing maybe 20 km/s, which is high.
--
There is nothing wrong with making      | Henry Spencer @ U of Toronto Zoology
mistakes, but... make *new* ones. -D.Sim|  [e-mail]  utzoo!henry

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End of Space Digest Volume 15 : Issue 183
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