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Subject: SPACE Digest V11 #228

SPACE Digest                                     Volume 11 : Issue 228

Today's Topics:
                 16mm to 35mm
          Re: Observations of STS 36 and its Payload
             Pegasus Stats Repost
             Re: Pegasus, what happened ?
            Re: orbit definitions
               Re: Velikovsky's Theory
          Re: Will we lose another orbiter?
            Re: orbit definitions
               Re: Velikovsky's Theory
----------------------------------------------------------------------

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ReSent-Date: Fri,  6 Apr 90 11:17:50 -0400 (EDT)
ReSent-From: "Todd L. Masco" <[e-mail]>
ReSent-To: Space <[e-mail]>
Date: Tue, 27 Mar 90 14:14:02 EST
From: Mark Ritchie <[e-mail]>
Subject: 16mm to 35mm
X-Envelope-To: [e-mail]

While it is a good idea to refrigerate motion picture film for long term
storage, temperatures much below 0 C make the film brittle.  NASA
does not store its film stock in liquid nitrogen.  As for blowing up 16mm
to 35mm, that is a relatively trivial exercise and any competent film
lab can do it quite quickly.  I would think that the bulk of the time
spent on producing the film was spent in viewing the stock footage and
editing it.  Six million feet of film would take 115 days to view running
non-stop.
I understand the IMAX Corp. is working on another space film, I really
want to see that.  The DREAM... was partly shot on 35mm, the next one
will be all IMAX.  Perhaps someday they might do an OMNIMAX 3-D film,
although Graeme Ferguson has told me that space doesn't have enough
visual depth to make good 3-D.


Mark Ritchie                           | Tel: [phone]
Media Librarian                        | Fax: [phone]
Audio-Visual Centre                    |
University of Waterloo                 | Net: [e-mail]

--------

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

Date: 6 Apr 90 13:19:13 GMT
From: swrinde!zaphod.mps.ohio-state.edu!samsung!sol.ctr.columbia.edu!IDA.ORG!pbs![e-mail]
Subject: Re: Observations of STS 36 and its Payload

In article <[e-mail]>, [e-mail]
    (Daniel Fischer) writes:
>   I haven't seen a reply to Roy Smith's question <16 Mar 90 14:31 GMT> so far,
>            but I think it deserves further thoughts. He had asked:
>> ... an object about 100 feet long and about 100 miles up should subtend about
>> half a minute of arc... With a good scope under good conditions I would guess
>> you should be able to clearly see gross features on the shuttle... one might
>> even be able to peek inside the cargo bay and see what they've got in there...
> On the optical side you are right, the shuttle (or Mir, BTW) should make a nice
> planet-size target. But the big problem is the apparent angular velocity. Here
> are some more 'back-of-the-envelope' calculations. Lets have the shuttle at
> 7000 km from the center of the earth -> its orbit's circumference is 44000 km.
> It takes 90 minutes for that -> 490km/min or 8 km/s. Now at 300km altitude
> directly overhead, you see it go with arctan(8/300)=1.5 degrees per second.
> That means that the shuttle travels 1 arc min in 1/100 sec through your field
> of view or takes about   1 / 2 5 0  s e c  to travel its own length! One would
> have to build a special tracking device to follow it, as no one can track a
> 100'/s-target manually at the x100+ magnification needed. But shouldn't that be
> possible with the current state-of-the-art of amateur telescope making and the
> availibility of precise orbital elements? Has someone tried to do that already?
>

      I was always a  poor  math  student  (not  for  lack  of  trying  or
      interest),  so  take my remarks with a grain of salt, since I may be
      missing something here.  But it seems to me that you're figuring 1.5
      deg/sec  based  on  swinging an arc around your vantage point 300 km
      from the object being observed, in which case it  will  crash  at  a
      nearly  90-degree  inclination  maybe  186  miles  or  so  downrange
      ("nearly" because of the earth's curvature).  If the shuttle is  300
      km  high,  and  maybe  6700  km  from the earth's center, the arc it
      describes would be swung from the earth's center, in which case  the
      1.5  deg/sec  speed would only occur when it is 90 degrees overhead,
      and the radius line passes directly through the  observer.   As  the
      shuttle  "comes  up" from the horizon it will be farther than 300 km
      from the observer and appear to move  more  slowly.   Again,  as  it
      recedes  towards the other horizon it will appear to slow down as it
      gets farther away and the angle of observation decreases from 90.

      Does this sound right to all you engineering and mathematical types?


> +- [e-mail] --- Daniel Fischer --- [e-mail] -+
> | Max-Planck-Institut f. Radioastronomie, Auf dem Huegel 69, D-5300 Bonn 1,FRG |
                                            ^^^^^^^^^^^^^^
      Auf dem Huegel sitzt er spaehend ...

> +----- Enjoy the Universe - it's the only one you're likely to experience -----+

    Disclaimer:  Was weiss ich von der Raumfahrt?

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

Date: 6 Apr 90 22:34:40 GMT
From: agate!volcano.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Pegasus Stats Repost

Pegasus is a three-stage winged [first stage] solid rocket able to launch
600 lbs into a 250nm polar orbit or 900 lbs into a 250nm equitorial orbit.

The vehicle itself is 49.2 feet long, with a diameter of 48 inches and a
wingspan of 22 feet.  It weighs 40,000 pounds at launch and is about the
same shape and size as X-15 rocketplane, which was also launched from the
B-52.  The payload fairing is 46" diameter by 72" long.

The launch costs are estimated at $8 million per launch, or about $10,000
per pound to orbit.  This is unfavorable compared to other launchers on a
per pound basis, but the small total cost remains attractive to those not
needing large payloads.  It is considerably better than other small
launchers.

The launch profile follows:
Launch is from the B-52 mothercraft, flying at 40 thousand feet and Mach 0.8
From here until the seperation of the first stage, the craft is controled
by a set of aerodynamic control fins.  Five seconds after release, the
first stage ignites and the rocket begins a 2.5g pullup.  At about fifty
seconds into the flight the craft reaches max-q [maximum aerodynamic pressure
on the rocket], at about 950 lbs/ft^2 force.  After 81 seconds, the first stage
burns out and seperates.  At this point, the rocket is at 208,000 feet and
moving at mach 8.7.

The second stage is controled by a cold-gas reaction control system which takes
over immediately after the first stage seperates.  At 87 seconds into the
flight, the second stage ignites, thrusting at an angle of 26 degrees above the
horizon.  At this point the craft is at 231,000 feet altitude.  At the 120
second mark the payload fairing seperates from the craft.  At 159 seconds
the second stage burns out, with the craft at 552,000 feet and 17,800fps
velocity.  It is oriented 18.4 degrees above the horizon.

The rocket now enters a coast phase, with no activity.  When it reaches the
470 second point, the rocket is at 248nm altitude and 16,300fps velocity, with
an angle of 1.9 degrees to the horizon.  At this point the third stage ignites,
and burns until 533 seconds, at which point the spacecraft is at 250 miles and
25,000fps velocity [orbital velocity].

Additional variants have already been proposed; DOD is funding a variant using
the first stage of a MX missile to boost the rocket instead of using a B-52
launch.  The reasoning is that this would make an excellent quick reaction
light satelite launcher.


*******************************************************************************
George William Herbert     JOAT For Hire: Anything, Anywhere: My Price
UCB Naval Architecture undergrad: Engineering with a Bouyant Attitude :-)
-------------------------------------------------------------------------------
[e-mail] <= prefered [also [e-mail].. and [e-mail]..]
    Give me a billion dollars and two years and I'll build you a space
    station you'll never forget.
"Pull up!   NO, NOT THAT UP!" CRUNCH

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

Date: 6 Apr 90 05:52:03 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Pegasus, what happened ?

In article <[e-mail]> [e-mail] (David Parkins) writes:
>What happened to Pegasus? I feel like I'm living in a vacume (sp).

Pegasus exploded on impact with the celestial dome, instantly killing
all 25 midges on board.  The supersecret SDI payload disintegrated and
reentered over New York State; one large fragment impacted near Ithaca,
demolishing Carl Sagan's house.  The Air Force declined comment other
than saying "the mission achieved all major objectives."

And by the way, it's spelled Vayqume.  Don't they teach college kids
anything these days?

--
"DO NOT, repeat, DO NOT blow the hatch!"  /)\   Tom Neff
"Roger....hatch blown!"                   \(/   [e-mail]

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

Date: 6 Apr 90 20:20:50 GMT
From: psuvm![e-mail]
Subject: Re: orbit definitions

Organization: Penn State University
Date: Friday, 6 Apr 1990 05:17:00 EDT
From: <[e-mail]>
Message-ID: <[e-mail]>
Newsgroups: sci.space
Subject: Re: orbit definitions
References:  <[e-mail]>

In article <[e-mail]>, [e-mail]
(Bart_Eleveld) says:
>
>Would some kind soul(s) out there post definitions for the various types of
>orbits that are often talked about on the net; e.g., Clarke, geosynchronous,
>geostationary, and any others you might wish to add.  Also, how much more
>energy (in relative terms) does it take to launch a payload to the west, or
>to the poles (N or S) rather than to the east?
Sure...

I'm not too sure on the definition of a Clarke orbit-- it is eaither geosynchro
nous or geostationary. It gets its name from Arther C. Clarke, who proposed
communication satellites in such an orbit.
 A geosynchrounous orbit is one that has the same orbital period as the Earth's
sidereal rotation (23hr56m4sec), but does not have an orbital inclination and
eccentricity of zero. A satellite in such an orbit would weave figure-eights
around a point on the ecliptic when viewed from the ground.

A geostationary orbit is a geosynchronous orbit with an inclination and eccen-
tricity of zero. A satellite in this kind of orbit always appears in the same
spot in the sky (somewhere on the ecliptic).

Launching west is very expensive in terms of propellant; when the rocket starts
out on the ground, it already has an eastward component of velocity equal to
the rotational velocity of the Earth at its launch latitude. To get to orbital
velocity, the difference between the orbital velocity and the rotational
velocity on the ground has to be made up. However, if you want to go westwards,
you have to make the same change in velocity, plus twice the Earth's rotational
velocity at launch.

Going into a polar orbit is also very expensive in propellant. Assuming that
the satellite starts out in a circular orbit of inclination i0 (=28.5 degrees
for Kennedy) then the required velocity change to go to another inclination i1
is
       ____
dV = \/GM/r sin((i1-i0)/2)

where r is the orbital radius, G is the universal gravitational constant, and M
is the mass of the Earth.

To find the amount of propellant needed to perform a velocity change, the
following equation is used


Mp  = Mo(1-exp(-dV/Ue))

Where Mp is the mass of the propellant, Mo is the mass of the satellite before
the velocity is changed, and Ue is the exhaust velocity of the propellant being
used. This assumes that the velocity is changed over a very small period of
time-- if you take your time to change your velocity, you have to burn more
fuel. Putting some numbers in, to go to polar orbit from a 400km high, 28.5
degree inclination orbit, the required velocity change is 3.921 km/sec, and, if
you use hydrogen and oxygen for propellant (best available exhaust velocity for
chemical reactions), 59% of the satellite's initial mass must be propellant. In
other words, if your payload to polar orbit is 100kg, you have to launch 244kg
into the initial circular orbit (100kg of payload + 144kg of propellant).

Mike Williams
[e-mail]

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

Date: 6 Apr 90 15:08:49 GMT
From: MATHOM.GANDALF.CS.CMU.EDU![e-mail]  (Donald Lindsay)
Subject: Re: Velikovsky's Theory

References: <[e-mail]> <[e-mail]>
Organization: Carnegie-Mellon University, CS/RI

In article <[e-mail]> [e-mail]
     (Henk van der Griendt) writes:
>I am interested too to hear from the scientist about Velikovsky's
>theories.
>I know in the past most scientists simply did not like him and did not
>want to take his theories serious.

This question (and any answers!) should go to the "sci.skeptic"
newsgroup. Velikovsky is discussed there at intervals.

As for taking his theories seriously ... they can be flatly disproved
in many independent ways. The only thing left TO take seriously is
their longevity.
--
Don        D.C.Lindsay     Carnegie Mellon Computer Science

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

Date: 6 Apr 90 15:47:37 GMT
From: zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Will we lose another orbiter?

In article <[e-mail]> [e-mail] (Lou Adornato) writes:
>Another big problem: how do you put redundancy into software?  Even with
>harware voting and a backup flight system, a design (or code) error in the
>primary avionics system could destroy the orbiter before the backup
>could take over.

This just means you need fast switchover to backups, or a system designed
so that slow switchover is tolerable.  It can be done.

Redundancy in software is not at all impossible; the shuttle already has
that in its main computers.  Four of the computers are for primary control,
running the same software.  The fifth runs radically different software,
written by a different group using a very different structure, which is
solely charged with getting the orbiter down safely.  One does have to be
careful, because it's all too easy for common failure modes to creep into
software even when it's independently written, but there is nothing about
the idea that is inherently impossible.
--
Apollo @ 8yrs: one small step.|     Henry Spencer at U of Toronto Zoology
Space station @ 8yrs:        .| uunet!attcan!utzoo!henry [e-mail]

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

Date: 6 Apr 90 21:37:39 GMT
From: zephyr.ens.tek.com!wrgate!mrloog![e-mail]  (Dan Tilque)
Subject: Re: orbit definitions

[e-mail] (Henry Spencer) writes:
>
>Geosynchronous    Any orbit synchronized with the rotation of the Earth, i.e.
>orbit        with a period which is some multiple or divisor of 24 hours.
>        Often used sloppily to mean geostationary.
>
>Geostationary    The 24-hour equatorial orbit, where a satellite appears to
>orbit        hang motionless in the sky.  Most comsats are found here,
>        as are an assortment of others that want a constant view
>        of the Earth (early-warning satellites, some weather sats)
>        or just easy communications in high orbit (some astronomy
>        satellites).

There's a variation on the Geostationary orbit but I'm not sure if it
has a name.  I suppose it could be called a Geosynchronous, but it's
more specific than the definition of geosynchronous that Henry gives.

The orbit is 24-hour but has a non-zero inclination.  From the ground
it would appear to move up and down on a daily basis while staying over
the same meridian.

I'm not sure how much it's used now, but as the geostationary orbit
slots get filled up I can see that some applications that don't require
continuous communication with the satellite could use it.  The idea
here would be that it would only communicate with the ground when it's
not near the equator.  Thus it could have virtually the same longitude
as a comsat and without interfering with it.

Another advantage is that, if you can live with the inclination of the
launch site, it should take less delta-V to get to than a true
geostationary orbit.  This advantage may be wiped out if you then have
to add a scan platform which keep the instruments pointed correctly on
a 24-hour basis.

---
Dan Tilque    --    [e-mail]

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

Date: 3 Apr 90 08:01:01 GMT
From: mcsun!hp4nl!dnlunx!spex1![e-mail]  (Henk van der Griendt)
Subject: Re: Velikovsky's Theory

[e-mail] (Tom Neff) writes:

>The burden of proof is on Velikovsky, not the rest of the world.  Until
>conventional explanations prove incapable of explaining conditions on
>Mars, Jupiter and Venus -- something that ain't happened yet -- we don't
>need to adduce comets emitting themselves from Jupiter and careening all
>over the Solar System to explain things.

1st: Velikovsky died some time ago. So his burden is over.
2nd: Since when do conventional explanations exist for the conditions on
     the planets ( or am I ignorant ?).

>Velikovsy's "theories" belong more to the sociocultural history of
>Russian mysticism than to cosmogeny or physics.  Their enduring
>popularity among the Fort-and-Fuller crowd is a monument to the tenacity
>of good old American trailer park know-nothing-ism.  Personally I'm a
>*real* big fan.

3rd: How do you come to your conclusion about Russian mysticism?
4th: What is a Fort-and-Fuller crowd (remember, I am a european) ?
     What has that to do with trailers?
5th: Of what are you a fan?


>I note in passing that VELIKOVSKY is a clever anagram for ELVIS YVOKK,
>which well-read para-students will recognize as The King's Atlantean
>name before he was lowered to Earth from a Crystal UFO in the Tennessee
>backwoods back in 1951.  What does the Air Force know about this???? and
>why won't so called scientists admit it???!  :-)
>--

6th: If they are anagrams, it could be the other way round:
     Velikovsky was born in the 19th century under that name if I am well
     informed, and started to publish long before 1951.

So why did you write that ?

Greetings from Holland.
--

================================================================================
|    Henk van der Griendt            E-mail: [e-mail] (internet)|
|    Speech Processing EXpertise centre        [e-mail]    |

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

End of SPACE Digest V11 #228
*******************