Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_9/V16NO916.TXT

Text File | 1993-08-03 | 34KB | 860 lines

Space Digest                Sun, 25 Jul 93       Volume 16 : Issue 916

Today's Topics:
                             ACRV return
                        A ride to mir for onl
                 A ride to Mir for only $12 million?
                               Catapult
           Clarke's "The Hammer of God" bought by Paramount
Cryogenic Rockets - Controversy between U.S, Russia and India (3 msgs)
                                 DC-X
            DC-X Prophets and associated problems (3 msgs)
                  GPS in space (was Re: DC-1 & BDB)
                         More press silliness
                      Space Lottery! Any ideas?
                                 test

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

Date: Sun, 25 Jul 1993 01:04:16 +1200 (NZST)
From: Bruce Hoult <[e-mail]>
Subject: ACRV return
Newsgroups: sci.space

[e-mail] (Henry Spencer) writes:
> A back-of-the-envelope calculation says that you need
> 112 fleets deployed to have a high probability of having one within
> 1000km of a random landing.  Not in the USN's wildest dreams were they
> ever capable of anything like that... and 1000km is a long way if the
> capsule has people in urgent need of medical assistance.

I had a tour inside an interesting machine at the Auckland airshow last
November -- a jet powered amphibian called the "Albatross".  Its STOL
capabilities and low speed handling were quite impressive for such a
large aircraft and it showed a pretty good turn of speed as well.  It
was the hit of the show, and hundreds of small boats turned out to see
it land on the harbour at Mechanic's Bay (the former "Empire" class
terminal).

The USSR used it to resupply and exchange crews for nuclear subs and
apparently the west was unaware of it until three or four years ago.

A few of those would make the ocean pickup task a little more
feasible...

-- Bruce

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

Date: Sat, 24 Jul 93 08:37:00 -0500
From: Charles Radley <[e-mail]>
Subject: A ride to mir for onl
Newsgroups: sci.space

 -=> Quoting Johnwl to All <=-

 Jo> man in space last night. At one point the figure of $12 million was
 Jo> stated as the "commercial" cost the soviets were asking to put a man
 Jo> into Mir. This cost seems very low. If try, I could imagine many
 Jo> millionares might be willing to plunk down this money for the ride of a
 Jo> lifetime! I have some questions, however:

 Jo> 1) can this cost be correct?!?

Yes, it is correct.

 Jo> 2) if they WOULD fly to Mir commercially, would they take anyone
 Jo> with the cash, or would they require firly rigorous training in
 Jo> case the paying passengers has to "back up" a cosmotnaut who fell
 Jo> ill,

All the guest cosmonauts take about six months of training.
Russia also seems to have some kind of policy restricting flights
to guests who have a scientific purpose.   Singer John Denver
wanted to fly to Mir, but I hear he was refused because his
flight would have no scientific content.


 for example. 3) are any components of the Energia lifter
 Jo> salvaged after lauch?

 Energia is not curently flying.  It has flown twice, and
 none of the components were reused.

 Jo> Sorry for the simple questions, but I am intrigued by the
 Jo> possibilities and may buy a lottery ticket!   ;-)

Some people tried to run a lottery in Texas, but it violated
state lottery laws, and the State attorney closed them
down.


... Internet address:- [e-mail]  Ad Astra per Guile !
--- Blue Wave/QWK v2.10

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

Date: 24 Jul 1993 16:42:49 GMT
From: Claudio Egalon <[e-mail]>
Subject: A ride to Mir for only $12 million?
Newsgroups: sci.space

> Only one millionaire has attempted this, so far as we know, and he
> wasn't willing to pay the full price, so he didn't fly.  (I'm assuming
> John Denver is a millionaire-- forgive me if this isn't true, John.)

I might be wrong but I recall that John Denver offered around US$40
million to fly to the Mir. Is it right? Since he did not fly, apparently
the Russians  were asking more than that. I am not aware of how much
the Japaneses paid to fly their journalist so I would like to know if
there  is anyone in the Net that have the right figures.

Claudio Oliveira Egalon
[e-mail]

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

Date: 24 Jul 1993 08:12:31 GMT
From: Darth Vader <[e-mail]>
Subject: Catapult
Newsgroups: sci.space

I was wondering if anyone out there ever thought about what it would take to
build a Heinlein style catapult.  What would it cost?  Would any private
corporation be able to fund such a project?  Is it technologically possible
at the present?  Just speculating absently...
--

    _/_/_/_/  _/_/_/_/  _/    _/ | [e-mail]
   _/        _/    _/  _/_/  _/  | [e-mail]
  _/_/_/_/  _/_/_/_/  _/ _/ _/   | Remember, the enemy's gate
       _/  _/    _/  _/  _/_/    | is DOWN.
_/_/_/_/  _/    _/  _/   __/     |            -- Ender Wiggin

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

Date: Sat, 24 Jul 1993 13:25:47 GMT
From: "Gerald G. Marfoe" <[e-mail]>
Subject: Clarke's "The Hammer of God" bought by Paramount
Newsgroups: sci.space

I just caught the tail-end of NPR's interview with Arthur C. Clarke from
Sri Lanka. At the end of the interview, Susan Stamberg (sp?) announced that
Clarke's latest novel, "The Hammer of God", had been bought by Paramount.
Looks like we'll be seeing the movie in a few years then.

Would anybody happen to have taped the interview? If anybody can get a
transcript of the interview and post it on sci.space, I'd appreciate it.
Clarke was saying something like, if or when we do encounter other
intelligent lifeforms in the universe, that he should hope that they weren't
malevolent beings. Hopefully, any malevolent race would have self-destructed
before it got into contact with us.

---

-------------------------------------------------------------------------------
Gerald G. Marfoe                    |"Mirabile visu. Mirabilia/Et itur ad astra
InterNet: [e-mail]    |... Suus cuique mos. Suum cuique.../
          [e-mail]   |Memento, terrigena./Memento, vita brevis."
                                    |- "Afer Ventus", Enya, "Shepherd Moons"

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

Date: Sat, 24 Jul 1993 12:08:11 GMT
From: Herman Rubin <[e-mail]>
Subject: Cryogenic Rockets - Controversy between U.S, Russia and India
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Matthew DeLuca) writes:
>In article <22qica$[e-mail]> [e-mail] (George William Herbert) writes:
>>[e-mail] (Savita Kaveti) writes:

>>>     Leaving the politics aside, Can any knowledgeble nettor comment on
>>>     whether cryogenic engines can be used for missiles.

>>No, except for the first generation of missiles (US and Russian),
>>nobody's ever used cryogenic (especially LOX/LH2) motors in missiles.

>In other words, the answer is yes.

>I think the restriction and U.S. interference is kind of silly (after all,
>the most likely target of an Indian nuke is Pakistan, and they're not
>exactly a distant target), but it *is* true that the technology could be
>used that way.

Instead of trying outlandish arguments, just use a little freshman physics.
Take any launch vehicle, put on a massive load aligned so that it doesn't
spin out of control, and the resulting trajectory is that of a missile.

The only way this would be useless for the purpose is if the launch vehicle
has too much power for this.  This would be the case if the vehicle, unless
greatly modified, will lift objects far more massive than a missile into
orbit.

--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)
{purdue,pur-ee}!snap.stat!hrubin(UUCP)

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

Date: 24 Jul 1993 10:17:17 -0400
From: Pat <[e-mail]>
Subject: Cryogenic Rockets - Controversy between U.S, Russia and India
Newsgroups: sci.space,talk.politics.space

In article <22qica$[e-mail]> [e-mail] (George William Herbert) writes:
>[e-mail] (Savita Kaveti) writes:
>>      Leaving the politics aside, Can any knowledgeble nettor comment on
>>      whether cryogenic engines can be used for missiles.
>No, except for the first generation of missiles (US and Russian),
>nobody's ever used cryogenic (especially LOX/LH2) motors in missiles.
>

Meaning Yes.  But, as is easily noted,  the logistical difficulties
of Liquid Fueled Rockets  especially cryogenics  makes them poorly
suited for military purposes.  Of COurse Liquid Fueled vehicles are
significantly easier to develope  and far more flexible,  making them
much more suitable both as space launchers and first generation vehicles.

I would be surprised if any country  first developes  solids.

Of course,  The real question to ask, is would Liquid fueled ICBM's
be very useful  given the significant advances in  US and FSU technology.
answer NO.  Liquid fueled vehicles have such a poor readiness level,
that I would venture that aany country relying entirely on
liquid fueled vehicles would need some  10 times their  actual
use inventory in order to maintain readiness.

Also Liquid Cryogenics,  require such a large logistical Tail,  they
would be poor candidates for Mobile launchers ( A major current problem)
and even poor candidate for ICBM's  any air burst  would most likely
disrupt all the support tankage.


>exact items, as black-box items, had essentially zero military
>usage (except insofar as any space launch vehicle can launch
>military recon and communications payloads as well as commercial
>payloads).
>

True.  given Indias already developed some Launcher capacity,
it is silly to claim they already lack this capacity organically.


>However, the propulsion expert was very strongly of the opinion that
>the transfer would end up including enough basic information that
>things such as basic understanding of combustion process modeling
>would also be transfered, which are applicable to essentially any
>motor design.  Personally, given that India has already indigenously
>developed and launched liquid-fuel vehicles, I think they already have
>enough knowledge that anything gained by inspecting a LOX/LH2 motor
>would be pretty meaningless, but my expert friends disagreed.
>

Realize,  that even though your friends work at lewis,
the US military Industrial complex  has a strong belief that
only Americans  have the grace from god  to ever come up with an idea.

They find it hard to accept that smart people are really the same everywhere.

>The final word is that the experts seem to think that there were
>dual use technologies involved, at some level, though the overt
>items were civil-use.  As this is an area where they know more than
>I do, I'll strongly suggest that you listen to them seriously,
>as I did, though based on my (lesser) direct knowledge I disagreed.

The real question to ask them, is what makes them think that
the indians  couldn't develope the military technologies anyway?

After all the BS they went through trying to buy a CRAY,  they ended
up building their own MPP.  it's a little crude.  (Its a lot crude)
but they built it, and now they don't have any restrictions on their
activities.

pat

--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 24 Jul 1993 10:09:32 -0700
From: Dennis Cuy <[e-mail]>
Subject: Cryogenic Rockets - Controversy between U.S, Russia and India
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Herman Rubin) writes:
>In article <[e-mail]> [e-mail] (Matthew DeLuca) writes:
>>In article <22qica$[e-mail]> [e-mail] (George William Herbert) writes:
>>>[e-mail] (Savita Kaveti) writes:
>
>>>>    Leaving the politics aside, Can any knowledgeble nettor comment on
>>>>    whether cryogenic engines can be used for missiles.
>
>>>No, except for the first generation of missiles (US and Russian),
>>>nobody's ever used cryogenic (especially LOX/LH2) motors in missiles.
>
>>In other words, the answer is yes.
>
>>I think the restriction and U.S. interference is kind of silly (after all,
>>the most likely target of an Indian nuke is Pakistan, and they're not
>>exactly a distant target), but it *is* true that the technology could be
>>used that way.
>
>Instead of trying outlandish arguments, just use a little freshman physics.
>Take any launch vehicle, put on a massive load aligned so that it doesn't
>spin out of control, and the resulting trajectory is that of a missile.
>
Cryogenic motors can and have been used as launch vehicles for
nukes.  The US used them in the 50s (late?) and through the 60s
until they started replacing them with the solid-propelled
Minuteman I's in 1963 (followed by MMIIs and MMIIIs).  The US
maintained the Titan missiles up until maybe the mid-80s when the
last one was taken out of service somewhere in the South (Alabama?)
- I think that's what I remember reading.  However, they were
notorious as far as maintaining them on strategic alert all the
time.  Trying to maintain the LOX/LH2 in the missile was probably
the biggest problem.  With solid motors, all you have to do is
worry about the guidance and other avionics boxes from going down
- they're far better as strategic forces.

So, yes, you can use cryo engines on launch vehicles intended as
missiles.  It's just tough to keep them at some level of readiness
all the time.  If you just plan on firing a couple and knew exactly
when you wanted to do it, it doesn't sound any more difficult than
a regular orbital mission.

Dennis
email:  [e-mail]

[These are just my opinions and no one elses.]

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

Date: Thu, 22 Jul 93 15:23:27 GMT
From: aaron thode <[e-mail]>
Subject: DC-X
Newsgroups: sci.space

I support the Clipper, but I also think there are a lot of unwarranted claims
floating around. Here are three examples to show that the Clipper is
very experimental, and that any talk of "man-rating" and "$10 to orbit"
is somewhat premature.

        1) MacD optimistic projections for DC-1 launch cost is <$1000/lb, not
$20/lb. This is based on their own viewgraphs.
        2) Several thorny technical issues haven't even been tackled let.
MacD is looking for help in designing coatings for carbon-carbon composites,
because an unprotected heat shield will be eaten away by atomic oxygen upon
reentry. So some applied research needs to be done.
        3) A source at MacD close to the project says that no one on the
team is confident that SSTO is possible. "We are building the Wright Flyer,
and people are talking as if we already had the DC-10," he said.

        What the so called 'critics' are pointing out is that one can
do more damage to a program by making unwarranted claims than by saying
nothing at all. So please, no talk about launch costs or man-rating for
now. Let's just get the damn SX-2(or whatever the current prototype is)
funded.

Aaron

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

Date: 24 Jul 1993 13:13:50 GMT
From: "Michael C. Jensen" <[e-mail]>
Subject: DC-X Prophets and associated problems
Newsgroups: sci.space

Greg Moore ([e-mail]) wrote:

: Do those begin to give you clues as to why some of us are frustrated
: by NASA?
:       Fortunately, NASA does seem to be reforming, praise Goldin!

We are restructuring and learning from our mistakes. (We ARE all
human, and prone to make some now and then..) NASA still has one
of the most competent and skilled work forces of ANY organization on
the planet, and once we get our act together, watch those babies
fly..

(Much of the thanks does indeed go to Goldon, AND the many people
inside NASA who have proven willing to make and accept the changes
nesessary to reform NASA and make it a more efficient organization..
from what I've been reading about the new "projects structuring"
system that probably will end up being used, I beleive most of those
with open minds out there will find themselves pleasantly surprised.
It's important to note that these changes have been going on for
almost a year, and will probably take another year or two to get
working right, but personally I beleive NASA'll end up doing it, and
doing it right. Give em a chance.. ;)

Mike

--
Michael C. Jensen   Valparaiso University/Johnson Space Center
[e-mail]  "I bet the human brain is a kludge." -- Marvin Minsky
[e-mail]  *WindowsNT - From the people who brought you edlin*
---Disclaimer: The opinions expressed are my own... ---

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

Date: 24 Jul 1993 10:56:15 -0400
From: Pat <[e-mail]>
Subject: DC-X Prophets and associated problems
Newsgroups: sci.space

In article <22pjt7$[e-mail]> [e-mail] (Michael C. Jensen) writes:
>Henry Spencer ([e-mail]) wrote:
>add to a program IMHO) my point is that the shuttle max of near eight
>flights a year is MOSTLY caused by limitations of number of vehicles
>availabe, and therefore is a poor argument against the shuttle system.


Michael.

        Don't you think a sorty rate of 2/year, is awful poor performance.
considering  OV's  cost 1.5 Billion each.  probably 1 Billion each
if you bulk buy and get  newer designs  (allowing for incompatibility
in the fleet).   It's this crap sorty rate that has people annoyed.

pat

--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 24 Jul 1993 11:02:32 -0400
From: Pat <[e-mail]>
Subject: DC-X Prophets and associated problems
Newsgroups: sci.space

Mary doesn't even mention that the B-1's ECM system
doesn't work right.

pat
--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 24 Jul 1993 10:41:26 -0400
From: Pat <[e-mail]>
Subject: GPS in space (was Re: DC-1 & BDB)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>In article <22ov33$[e-mail]>, [e-mail] (Pat) writes:
>So, uh, where do you get the money to keep running all those science launches
>which you allege to have sitting in the wings AND purchase more ELVs and
>Russian launchers?
>

Every time I mention re-programming between fiscal years you return
to your mantra  that only the curreny FY means anything.  So i  guess
they don't.  gee. too bad.  if only they had better accountants.
then they might do better things.


|
|Pat, you're being dim.  Very dim.  The government reserves the right to cancel
|out funding at any time. And does. Ask the Sooper-Dooper collider people, who
|have seen the axe fall on them.
|

ASk the SSC folks,  why they are also 300% over projected costs.
Does that turn a light on?

|You're trying to argue that funding is gu-an-damn-teed on a multi-year basis.
|And as we've seen both recently and in previous examples, it ain't so.
|

Nothing is guaranteed,  but GAO rules allow  transfer of small
fractions between fiscal years.

If the state didn't do that, you wouldn't have gotten your 26th paycheck
last year.


|>Commercial yes.  but for gear that is large, heavy and can use man tending
|>STS is still it.  much as I like DC-1,  until it starts flying
|>we do need to stick it out with the shuttle.
|
|IF it is brought to term.  IF.

Remember this line folks.


|>Of course,  MTPE  keeps scaling down so badly,  that SSF  may end up
|>being a significant working platform.
|
|Scaling down?  No, they decided not to build mega-project satellites, using
|smaller platforms with less risk.
|

Another euphemism for scaling down.  The original version of MTPE
was for 70 some birds.  in all altitudes.  now it looks like 4-6.

2 most likely.

|Gee Pat, it's amazing to see such ENTHUSIASM for marginal uses of SSF,
|considering your avowed skepticism that it will ever fly.
|

Well, considering i find the Bio-medical excuse  ridiculous,  and i
have doubts about the science return  from the Materials science.

that only does leave one other mission.



|>Of course,  Taurus  is hardly well qualified hardware.  it's launch record
|>is not as good as say a soyuz.
|
|DoD is buying it. By the time Freedom is on orbit, it will be well-qualified.
|Actually, you'll see Taurus and probably one or two other companies with 30-60
|day launchers by 1998.  DoD/Air Force recognizes the need for rapid launch turn
|around exclusive of whatever NASA requirments exist.
|

IF it is brought to term.  IF.

Funny,  you apply one set of rules  to a SSRT project  and another
to an ELV project.


|>true.  but our  track record for fed-ex type launching is poor.
|
|There's been no defined need before. DoD/AF is working on this, as noted above.  It is

The need has been defined since the 70's.  it was why STS was supposed
to have a rapid sortie rate.  And why the USAF spent  4 billion
on Vandenburg.

|a recognized problem within the Air Force that putting sats on orbit on demand
|is a weakness, especially given the need for putting up payloads during Desert
|Storm.
|

Desert Storm  just tore the bandage off the wound.


|>I am convinced SSF won't meet operational spec.
|
|Nice of you to back off your previous assertions.
|

Considering i include  long term manned tended capacity as one of those
specs,  i wonder what you mean.  SSF  is a large welfare program,
for the aero-space corporations.  Any attempt to produce
flight hardware is just a unwanted by-product.


>>Dave McKissock is a decent guy.  most of the program is full of decent
>>folks,  but the program is not oriented at producing good flight
>>quality hardware.
>
>And what makes you qualified to judge that?  I can think of a lot of engineers
>you've just insulted.  Your brush is as large as Sherzer's anymore.
>

Well,  let's wait and see what the program produces.

>> I think they will have major problems with
>>functionality,  and that it will cost a lot more then they think.
>
>Sure. Because they will have to skimp up front to stay below the $2.1 bil
>ceiling and pay for it later.
>

HEy,  if they can't build a product with 20 billion dollars  they should
get out of the game.  that's a cop-out doug.


>>SSF has far too many risk activities in it.
>
>Yet you wanted to make it more risky by launching it into higher inclinations.
>Oh geez.
>

What additional  risks does the program take by higher inclination orbit?

And actually, it's not just me, this time.  It's also the Vest Panel.
Are you going to call them names too?


>>I was much more interested in hte JSC plan.  less risk,  faster time to build.
>>more use of existing infra-structure.  but the Reagan plan had already
>>screwed up everyone.
>
>Pat, what a crock.  Blame it all on the Republicans.  Typical.  Congress
>has equal blame to assess here, as does the way the United States government
>does business.


I didn't know the NASA chief works for Tom Foley.  Oh and next time
some small country gets invaded,  should they  go see Jim Wright for
assistance?  It's the presidents job to get funding.  Reagan had no trouble
getting 70 Billion dollars a year for Black world prohjects.  SSF
was not a major interest for him.  Look at the real world funding increases
he got for the DOD.  It al depends on priority.

pat:9


--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 23 Jul 93 18:55:01 GMT
From: Bruce Watson <[e-mail]>
Subject: More press silliness
Newsgroups: sci.space

There was an article in the local paper's Sunday magazine
about time capsules. The Voyager spacecraft were mentioned for their
gold plated copper phonograph records and the following statement
was made:

"Sometime in the next century these spacecraft will leave the
Milky Way and begin exploring other galaxies."

--
Bruce Watson ([e-mail])

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

Date: Sat, 24 Jul 93 08:43:00 -0500
From: Charles Radley <[e-mail]>
Subject: Space Lottery! Any ideas?
Newsgroups: sci.space

 -=> Quoting Greg Moore to All <=-

 GM>
 >There are, of course, many liability problems involved. The relative health
 >of the "winner" is a prime one. NASA would be considered negligent if they
 >sent someone through the rigors of launch, the wonder of zero-g, and the
 >stress of reentry knowing (or remaining purposely ignorant) of a heart con-
 >dition or something. That's just for starters.
 >
 GM> Make the winning prize transferable.  I know a lot of
 GM> grandparents that might buy up scads of tickets so their little
 GM> Johnny can fly into space.

 GM> Of course be up-front about the hazzards.  Make some
 GM> limits (person has to be 18 years or older and pass the same
 GM> physical as payload specialists).  Also, do NOT allow
 GM> substitutions.

 A couple of years ago a group in Texas tried to run a lottery
 where the winner would fly to Mir.

 Unfortunately the Texas state attorney declared the operation
 illegal, and immoral.   It violated Texas state lottery laws.
 The operation was closed down in a blaze of publicity and
 money received was refunded.

 Beware.




 GM> So, you get a person 25 years old in the prime of
 GM> his/her life, no problem.  They fly.
 GM> Or you get a person 67, poor health, etc.  I'm sure
 GM> they could sell the ticket, or give it to someone of their
 GM> choice.

 GM> I don't think liability is a big problem.
 GM> And remember, you can't sign away your rights to sue, so a
 GM> waiver won't solve all problems.  Besides, in the case of
 GM> something like a Challanger mishap, where a known problem
 GM> was overlooked, and the recommendation of several engineers
 GM> was overturned, I'd want to sue for damages.

 >So I wouldn't be too sure that we're looking at an easy path. But I posted
 >the Space Lottery idea because I think it *is* workable. I also believe it
 >could do a great deal of good for the space program in general.
 >
 >If it is to work, then we need to apply 'pressure' to more than just NASA.
 >At the moment, much of the government believes that the space program isn't
 >a priority. A false view to be sure. Perhaps the way to grease the wheels
 >is to continually press the idea that economic expansion for our country
 >lies off-planet, and that a lottery could enrich the government (!) to let
 >it happen --because a lottery would get much of the nation contributing
 >without complaining about taxes. It's funny. People will raise hell about
 >a tax increase that will cost them $1 a week. But they'll gladly spend a
 >few times that voluntarily if they believe there is the remotest possi-
 >bility that there's something in it for them. :-)
 >
 >
 >--
 >Bob Kirkpatrick -- Dog Ear'd Systems of Spokane, WA
 >I love my country. I'm just not fond of it's people and I hate the government.



... Internet address:- [e-mail]  Ad Astra per Guile !
--- Blue Wave/QWK v2.10

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

Date: 23 Jul 93 22:18 PDT
From: Alan McGowen <[e-mail]>
Subject: test
Newsgroups: sci.space

This is a test, please ignore it.

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


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Source-Info:  Sender is really [e-mail]


In a previous article, [e-mail] (Randy) says:

>[e-mail] (Russ Renaud) writes:
>:
>: In a previous article, [e-mail] (Remi Cabanac) says:
>:
>: >>Where on the Internet could one get some information
>: >>re: the SETI project?  I'm looking for some basic info,
>: >>as well as perhaps some technical details, such as what is
>: >>the smallest discernible signal that the SETI radio telescope
>: >>are capable of detecting?  How are they processing the
>: >>myriad of signals they must be receiving.
>: >>
>: >>--
>: >
>: >I've just heard a lecture from Franck Drake and Billingham on the SETI project,
>: >at ISU in UAH few minutes ago.  Basically, the SETI receivers are built to
>: >detect the equivalent of earth emission from 5000 light years, which
>: >corresponds roughly to 10-23 W/m2/Hz (I'm not sure of the units).
>: >But it depends on the radio-telescope used (these data are for Arecibo).
>: >The emission are processed by an MSCA able to manage 6 million channels at once.
>: >Each emission is filtered with rigorous criteria such as periodicity, intensity
>: >regularity, etc...
>: >Until now, 38 signals are interesting and cannot be explained by radio
>: >terrestrial interference (yet).  But none are periodic.
>: >
>: >Remi Cabanac.
>:
>: I would assume this would be 10^-23 Watts/metres squared/Hertz, which
>: is a ratio of signal density to bandwidth.
>:
>: I would assume that one of the limiting factors in detecting these
>: extremely weak signals would be the internal thermal noise of the
>: microwave amplifiers.
>:
>: In conventional RF amplifiers, thermal noise is expressed as.
>: Pn = KTB, where:
>: Pn = Noise power in Watts
>: K  = Boltzmann's constant 1.38(10^-23)
>: T  = Noise temperature in degrees Kelvin
>: B  = receiver bandwidth in Hertz.
>:
>: With GaAsFET RF amplifiers, noise temperatures of less than 50 Kelvin
>: can be easily achieved even by us Amateur Radio operators.  I would
>: think that the SETI microwave equipment would be capable of far lower noise
>: temperatures figures, bring Pn very close to Boltzmann's constant.  I
>: have no idea if Pn=KTB would be a valid equation if K is a value
>: very close to 0 degrees kelvin.
>:
>: Can anyone shed some light on this?
>:
>:
>: --
> For those of us trying to visualize the signal levels involved....
>
>Assuming a plain CW transmitter, keyed slow enough to 'fit' the band-pass
>of the SETI receiver, located at that distance ( 5000 Light years), how
>much power would be needed for it to be heard, if the transmitter is using
>a unity gain dipole, and 1400 mc?
>
>
>--
>
>Randy,KA1UNW             If you get a shock while servicing your equipment
>                        DON'T JUMP!  You might break an expensive tube.
>
>
Jeez! I was hoping you would be able to tell me!  G3RUH made use of a
formula for determining signal strength for dish antennas for mode S
satellite  receivers in an issue of the AMSAT Journal. I'm not certain
how to substitute a dipole into that equation, so let's try the 300
metre dish in Puerto Rico.

Pr = Pt(pi d^2 /4) / (4 pi r^2) where:

Pr  = is the received signal strength in Watts;
Pt  = is the RF output of the ET's tranmitter in Watts;
d^2 = the diameter squared of the dish in metres
r^2 = the radius squared of the expanding sphere which
      is our radio wave; ie the distance between the
      tranmitter and receiver in metres.

Ok, I believe that one light year is 9.46E^15 metres.  If it isn't, then
this will screw up the calculation.

Let's assume a megawatt for the Et's transmitter, and 50 lightyears
of distance. Then;

Pr = 1E^6(3.14 x 9E^4 /4) / (4 x 3.14 x 2.24E^35)

Pr = 7.065E^10 / 2.81E^36 =

which, forgiving any dumb math mistakes is

2.514E^-26 watts, which is quite weak, certainly in relation to
Boltzmann's constant, which is 1.38E^-23.  So this signal would
definitely be less than the internal thermal noise of the
receiver.

I imagine that the SETI project has some means, perhaps using
signal processing, to improve this situation considerably.

73 de ve3uav



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End of Space Digest Volume 16 : Issue 916
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