Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_5/V16NO539.TXT

Internet Message Format | 1993-07-13 | 14KB

Date: Fri,  7 May 93 05:23:55
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #539
To: Space Digest Readers
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Space Digest                Fri,  7 May 93       Volume 16 : Issue 539

Today's Topics:
                Location Devices for RVs, also SARSATs
                             LRDPA update
               SSTO vs SSTO vs TSTO (Was: Boeing TSTO)
                         Vandalizing the sky.

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

Date: 05 May 93  21:17:12
From: [e-mail]
Subject: Location Devices for RVs, also SARSATs
Newsgroups: sci.space

(Michael Daniel Fennell) writes:
|3.  What is the coverage of SARSATS?  Are they in LEO with only
|intermittant coverage of a fixed position on the earth, or are they
|in geosynchronous orbit?

Pat writes:
>I think it's some sort of inclined orbit.  prety much everything
>gets covered, you just have to wait for a pass.

The SARSATs are a package on the US NOAA polar-orbiting weather
satellites (used to be known as the "TIROS" series).  They are in a
sun-sychronous orbit (about 98.6 deg, 440 nmi), and there are two US
satellites.  Some time ago, it was discussed to also include these
SARSAT packages on a Russian sun-synch weather satellite, but I
don't remember if this was ever done (I believe it was).
   The system is very simple -- it just uses a receiver listening
for a signal at a specific frequency band.  It picks up the signal
and then relays it and the time it was received to a ground
station (I believe the time stamp is just a periodic beep on the
sat receiver tape which can be referenced against a ground time
baseline.)  The ground station listens to the signal as relayed
from the satellite, and from the time it was heard at the satellite
and the Doppler shift in the received signal, plus the known
satellite empheris, can estimate the transmitter's location within a
square mile or so.  That's sufficient to dispatch a rescue team --
who can then home in on the downed aircraft using handheld portable
receivers once they know about where to look.

>I would look into how the Big Bird capsules were designed, and
>recovered.  That was vintage 60's technology and should be
>declassifed.  You may be able to get air force surplus an entire
>film recovery capsule,  with chutes and radios.
   It's not declassified.
   But other reentry technology, particularly for a one-use small
reentry system isn't that hard. (It's doing it predictably and well,
as well as reusably, that's difficult).
   The easiest reentry technique is to design a "hypersonic bowling
ball" -- don't try to make it statically or dynamically stable --
just make it survive reentry.  You can have up to +/- 30 nmi of
dispersion after reentry, but if you are over open ocean, that might
not be a problem.
   For an alternative location system, you might use a GPS receiver.
You can buy a commercial handheld off-the shelf system for <$1000,
which will locate itself to +/- 100 meters, and put out the position
location as an digital RS-232 output. (They're designed to feed into
a notebook computer.) Buying just the reciever card and antenna is
even cheaper.  The commercial systems are suprizingly rugged -
almost as rugged as the MIL-STD ones (remember these things are
designed for use by field surveyors, field geologists, boaters and
hikers, who bash them around in the outback during regular use).
   To find the reentry capsule, just take the output from the GPS
receiver, re-transmit the location coordinates on an appropriate
frequency (Short wave?), and listen for it.  It's a much more
immediate reception (rather than waiting for hours or days from the
SARSAT system), provides better location precision, and might be
cheaper to boot.
   Heck, you might be able to get a firm to donate a ruggedized
receiver in exchange for using it in their advertisements (A $1000
receiver from an existing production line is a doable donation....).
 ---------------------------------------------------------------
 Wales Larrison                        Space Technology Investor


--- Maximus 2.01wb

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

Date: 04 May 93  14:45:42
From: [e-mail]
Subject: LRDPA update
Newsgroups: sci.space

Back to the Moon Bill Nears Introduction in Congress

        As the first session of the 103rd Congress nears
midpoint, the chances of introduction of the Lunar
Resources Data Purchase Act grow. There are two ways for
this (or any bill) to be introduced in Congress, either as a freestanding
bill, or as part of another bill. In this case, there is a good chance that
the Back to the Moon Bill will be combined with other space legislation into
an omnibus space bill. This omnibus bil would be reviewed by the Authorization
Committee,and then forwarded to other committees for their review.
        This is extremely good news. However, a more favorable course would be
to have the bill introduced as a freestanding piece of legislation. This would
keep the bill as intact as possible (in an omnibus bill, there is a greater
possibility of the bill being watered down). Since we want a return to
the Moon as fast as possible, we need to keep working on
getting the bill introduced. If you have a few spare minutes,please contact
your congressperson to have them assist in the introduction of the Lunar
Resources Data Purchase Act.
        If you would like to help jumpstart America's long
dormant lunar exploration program, please send E-mail with your U.S. postal
service address.


--- Maximus 2.01wb

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

Date: 05 May 93  21:15:52
From: [e-mail]
Subject: SSTO vs SSTO vs TSTO (Was: Boeing TSTO)
Newsgroups: sci.space

[e-mail] writes:
> NASA/DOD/DOT are trying to put together a coherent strategy
> for future US gov't space transportation systems, and trying to
> juggle near-term launch needs (like for DoD and NASA) against
> medium-term needs (including commercial considerations), and
>against  the investment and risk of going to "leap frog" new
>technologies  like SDIO/SSTO and NASP and Beta.

Keith Mancus replies:
>  Good posting overall, Wales, but I have to comment on this last.
>I don't think it's fair to lump technologies like SSTO/Beta
>together with NASP.  NASP requires breakthroughs in many areas, and
>requires a long-term development program with a lot of basic
>research.  As my GN&C professor put it, "You could make a career
>out of NASP."  SSTO/TSTO, on the other hand, is an incremental
>technology that builds on what has gone before.  Most of the parts
>are taken off the shelf, or small evolutions of off-the-shelf
>parts.

   Hmm... as to "whether its fair to lump technologies like
SSTO/Beta together with NASP." is a debatable point.   I should
point out the purpose of the NASA/DoD/DoT "Access to Space" study is
to compare options -- so comparing a rocket powered SSTO to an
airbreather/rocket SSTO is a legitmate (and IMHO, required) trade.
   As a point of interest, I note the current NASA/DoD/DOT access to
space study is very specifically considering three typical vehicles
for Option 3 (Advanced Space Transportation Technology Systems) -- a
rocket-powered SSTO, a Airbreather/rocket SSTO, and a TSTO
airbreather/ rocket configuration.  From the technical descriptions,
the rocket powered SSTO is very similar to the Rockwell SSTO with
features from some of the Langley SSTO work, the Airbreather/rocket
SSTO is a NASP, and the TSTO airbreather/rocket is a Boeing Beta,
less the ramjets (it stages at only Mach 3.5).
   It is interesting to note the Access to Space study is using a
VTHL rocket powered SSTO, and not a Delta-Clipper type VTVL rocket
powered SSTO.  (I noted VTVLs were being considered for TSTO and
SSTOs in the previous status report on the study.).   The rumor is
McDonnell Douglas (MDC) declined to support the study.  It is also
interesting to note the team on Option 3 includes Col Payton from
the USAF, who was Mike Griffin's deputy at SDIO when Mike Griffin
was director of technology at SDIO, and would be conversant on SSTO
technologies and developments.

   As a last comment -- making a rocket-powered SSTO is still a non-
trival task. You seem to imply that SSTO/TSTO is pretty simple:
  >SSTO/TSTO, on the other hand, is an incremental technology that
  >builds on what has gone before.  Most of the parts are taken off
  >the shelf, or small evolutions of off-the-shelf parts.
   I'll agree that the NASP program has one major significant new
development that a rocket-powered SSTO doesn't need -- to
demonstrate performance and operation of a SCRAM engin.
   But it has to be pointed out that the DC-X program is only
proving out a couple of techniques needed to be demonstrated before
going on to the next stage of the program.  There are still a lot of
technologies and techniques that have to be refined and developed
before a SSTO can fly to orbit -- for example, the flight-weight
reusable cryo tanks, the flight control system (more than just the
VL part for the DC-X), the TPS/flight control system, new engines,
new light weight materials for the primary and secondary structure,
the integrated propulsion/RCS system, etc. etc.
   Some of these technologies and techniques are coming from the
NASP program (flight weight reusable cryo tanks and lightweight
material for primary structure).  I'm not saying a rocket powered
SSTO can't be done -- but just that there are a LOT of details which
still need to be worked out.  Paper vehicles always fly much better
than real hardware.  And it is a non-trival task to make a flight
vehicle.

   I'm going to echo some other participants on the net here, in
that trivalizing the development of a SSTO is a mistake.  There are
numerous ways to get to orbit, but "the devil is in the details".
It's not a trivially easy thing do.  Heck, it's costing Boeing about
$5 B and about 5-7 years to design and build a 777 -- and that's
an even smaller "off the shelf, or small evolution of off-the-shelf
parts" project.  :-).
   It's going to take time and cost serious money, and problems will
be encountered that will have to solved (and they will be).  Any
multi-billion and multi-year project is by definition "non trivial"
IMHO.  You have to go out and sweat through the details and MAKE the
F***ing THING.   And we can, and should.
 ------------------------------------------------------------------
 Wales Larrison                           Space Technology Investor


--- Maximus 2.01wb

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

Date: Thu, 6 May 1993 23:00:49 +0000
From: "Peter R. Humphrey" <[e-mail]>
Subject: Vandalizing the sky.
Newsgroups: sci.astro,sci.space

In article <[e-mail]> [e-mail] writes:
>In <[e-mail]> kevin patrick kretsch writes:
>>The sky was never intended to be a billboard (if it
>>was intended at all!) and hopefully it never shall be.
>  How do you know ??? Do you have a direct line to God ???
>Perhaps the sum purpose of life on Earth is to evolve a species
>who can paint pictures in the sky ...

No, the sum purpose of life on Earth is to ensure that there continues
to be life on Earth.

--
Rgds

Peter Humphrey  |  [e-mail]         | Voice 0932-343158
Woking, UK.     |  [e-mail]   | Data  0932-353948

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


From: Rob Unverzagt <[e-mail]>
Newsgroups: sci.geo.meteorology,sci.astro,sci.space
Subject: Re: moon on goes image
Date: 6 May 1993 22:33:16 GMT
Organization: Organization?  You must be kidding.
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References: <[e-mail]>
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Source-Info:  Sender is really [e-mail]

In article <[e-mail]> [e-mail] (R Clark x4971) writes:
>
> Over in sci.astro there is currently some discussion from someone pointing
> out that the moon was visible on a recent satelite image (the standard US
> coverage image). Sorry, I don't recall the date/time but those posts should
> still be current for most news sites.

The images in question were not about the moon in the image
but about a lunar eclipse in the image.  If we're talking
about the same images -- maybe my memory is failing.

The eclipse images were from GOES on 17 October 1986 at
1800 UT.

> Someone posted a list of additional opportunities when this might occur by
> searching lunar positions over the year. He used a position to make it
> visible on the standard 'domestic tv version' of the image. For anyone
> with access to the full hemisphere image it should actually be relatively
> common for the moon to be in the field of view.

Yup -- the moon is fairly common, although a lunar eclipse
should be pretty darn rare.

> My question is: how often and how much does the US (and the Europeans,
> Japanese too) move their geostationary satelites? I know that the US
> coverage was in pretty bad shape for a while following 1986 (the Year of
> the launch failure). There were no more GOES in the pipeline and GOES NEXT
> wasn't ready yet.
>
> So what is the situation now for moving satelites to optimize coverage
> based on season?
> and how rigorous is the station keeping while a satelite is being kept fixed
> at its assigned longitude?
>

I'm pretty sure that the one GOES in 1986 was moved to cover
Pacific storms better.  It was at 108 west longitude when it
picked up the eclipse image, having been moved from 98 west.

Shag

--
----------------------------------------------------------------------
       Rob Unverzagt        |
  [e-mail]   |       Tuesday is soylent green day.
[e-mail] |

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End of Space Digest Volume 16 : Issue 539
------------------------------