Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_5/V12_537.TXT

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Subject: SPACE Digest V12 #537

SPACE Digest                                     Volume 12 : Issue 537

Today's Topics:
       Titan IV accelerations (was Re: LLNL Astronaut Delivery)
           Re: Ulysses speeding up rel. to the sun
             Re: orbiting bodies
             Re: LNLL Inflatable Stations
       Re: You Can't Expect a Space Station to be Cheap

Administrivia:

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

Date: 6 Nov 90 21:41:47 GMT
From: [e-mail]  (SERRE GLENN)
Subject: Titan IV accelerations (was Re: LLNL Astronaut Delivery)

The max. sustained g-load for a Titan IV is 4.0g steady-state, +/- 2.0g
dynamic (meaning that transients can reach 6.0g).  This is for preliminary
design use and includes only axial accelerations.

Also, this occurs at Stage I sep, not SRM sep.


--Glenn Serre
[e-mail]

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

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Date: 6 Nov 90 16:34:18 GMT
From: sputnik![e-mail]  (dave warkentin)
Organization: M.I.T.
Subject: Re: Ulysses speeding up rel. to the sun
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
Sender: [e-mail]
To: [e-mail]

In article <[e-mail]>, [e-mail] (Chris Jones) writes:
 > In article <[e-mail]>, sw@cbnewsl
(Stuart Warmink) writes:
 > >
 > >I assumed that velocity w.r.t. to Sun meant *away* from the Sun.
 >
 > No, I think it means as measured from the Sun's frame of reference.
Earth has
 > a velocity w.r.t. the Sun of about 66000 mph.  Ulysses' speed w.r.t.
the Sun
 > immediately after launch did look like that velocity added to
30000mph plus,
 > which is what you would have expected the result to be.  I still have
seen no
 > explanation of how Ulysses gained velocity in the period after the
boost, but
 > I'm almost certain it didn't, and that there was an error in one of
the
 > velocity reports.
 > --
 > Chris Jones    [e-mail]    {world,uunet,harvard}!ksr!clj

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

I doubt it was merely a numerical reporting error, since I seem to
recall a specific statement about the speeding up in one of the updates
(sorry, I can't refer to the exact message.)  At the risk of wasting
bandwidth, I'm reposting a followup to an earlier comment on the
peculiarities of Ulysses's orbit (I suspect the followup wasn't properly
transmitted due to server problems):

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

In article <[e-mail]>, [e-mail] (Steve Masters)
writes:
 > [e-mail] (Stuart Warmink) writes:
 >
 > >Assume that Ulysses was boosted out of Earth orbit in such a
direction
 > >that it was originally at a tangent to the Earth's orbit - not an
 > >unusual direction for a boost to the outer planets. If started of in
such
 > >a direction its velocity w.r.t. the Sun would be 0. As Ulysses
gained
 >                                                  ^^^
 > ...not unless it were launched directly against the earth's orbital
velocity
 > at the earth's orbital speed...Ulysses, upon leaving earth's orbit,
was almost
 > certainly moving close to the earth's orbital velocity (about 18.5
mi/sec,
 > I think) relative to the sun.
 >
 > This doesn't explain an increase in sun-relative speed...are we sure
there isn't
 > a typo?  Unless there is a gravity assist from Venus, there is no
way
to get
 > to Jupiter by dropping closer to the sun (I don't think, anyway :) )
 >
 > Steve Masters    [e-mail]
 > ENSCO, Inc.
 > Melbourne, FL  32940  USA

I too was puzzled by Ulysses's increase in speed, so I performed a few
calculations to see if I couldn't come up with an answer (in the
absence
of more authoritative pronouncements :-).  First of all, the most
obvious transfer orbit from Earth to Jupiter is the ever-popular
Hohmann
transfer - the 1/2 ellipse which is tangent to Earth's orbit at
perihelion and to Jupiter's at aphelion.  Event schedules have been
posted for Ulysses which give the launch date as 10/6/90 and the
Jupiter
encounter date as 2/8/92 for a time of flight of 490 days.  The TOF (in
years) in the Hohmann orbit, though, is .5*(a^1.5), where a is the
semi-major axis in AU.  Jupiter averages 5.2 AU and Earth about 1 AU,
so
a for the transfer would be .5*(1+5.2)=3.1 and the TOF is 2.73 years,
or
997 days! Clearly the Hohmann transfer is not being used.  Presumably
the mission planners wanted to a) shorten the flight time and b) have
more speed for the Jupiter gravity assist, so they launched from Earth
with a velocity greater than that needed for the Hohmann.

It still seems reasonable to assume (as Stuart did above) that Ulysses
leaves on a path tangent to Earth's orbit, in order to take fullest
advantage of Earth's orbital velocity.  So now we need to find an orbit
which leaves Earth on a certain date tangent to Earth's orbit and which
arrives at Jupiter on another specified date.  According to my
home-made
ephemeris program, Earth was 1.000 AU from the Sun at launch and
Jupiter
will be 5.401 AU from the Sun at encounter, and the angle between these
two points is 145.2 degrees (just using heliocentric longitude and
ignoring Jupiter's latitude at encounter, which I think is about 1
degree).

It turns out, though, that a Keplerian orbit satisfying all these
conditions does not exist!  The one which connects these two points and
is tangent to Earth's orbit takes 558 days.  Assuming no really major
mid-course corrections, we have to through out the assumption that the
departure is tangent to Earth's orbit.  After some trial and error, I
found that if you assume that Ulysses actually does move closer to the
Sun before heading out to Jupiter, you can make the transfer orbit
satisfy the conditions.  This means transfer orbit perihelion doesn't
occur at launch, but some 6.24 days (8.445 degrees true anomaly)
_after_
launch, and so at first speeds up with respect to the Sun before moving
away and slowing down. Using this assumption, I find that Ulysses
reaches Jupiter with enough energy to perform a hyperbolic fly-by
gravity assist maneuver to redirect its velocity vector so than as it
leaves Jupiter's sphere of influence it can be in an orbit with
aphelion
at 5.401 AU, perihelion at 1.374 AU, a period of 6.235 years, and an
inclination to the ecliptic plane of 83 degrees.  This looks fairly
good, since previous postings have mentioned a perihelion of 1.4 AU
(signif. digit?) on 2/5/95 (period of just under 6 years).

A couple of questions remain.  First of all, why didn't they launch
tangent to Earth's orbit?  My tentative answer - that was the nominal
trajectory, but it just so happened that they got it off in the first
half of the launch window, so they adjusted injection conditions so as
not to throw everything else off schedule.  Sky and Telescope (Nov.
'90,
p.498) mentions a 19-day launch window starting on Oct. 5, so the
mid-point would have been Oct. 14-15.  Thus it could well be that they
launched a few days early, thus producing the 6.2 day time to
perihelion.

More importantly - why didn't they put it in a higher inclination?
Perihelion of the solar orbit is 1.4 (maybe 1.374) AU - why didn't they
trade some of that energy to reach a higher angle?

And perhaps most important of all - what does this imply for the
question of when Ulysses was closest to the Sun?  Unfortunately, not
much - I calculate the perihelion distance of the transfer orbit to be
.9949 AU, as opposed to the Earth's .9836, so it was still closer to
the
Sun on Earth than it ever was/will be in orbit.

(N.B. It occurs to me that in the above arguments about the transfer
not
being tangent to Earth's orbit I haven't taken Earth's non-zero flight
path angle into account, but I believe this effect is minor and doesn't
substantially affect the calculations.

A good reference for would-be space cadets:
  Fundamentals of Astrodynamics by Bate, Mueller, and White : ISBN
0-486-60061-0
It is (or was) the USAF Academy textbook on the subject.  It's a Dover
publication, and cost me $5.50 about 10-12 years ago, so it probably
costs a bit more now.)

For those who actually read this far, thanks for letting me put my $.02
in.  Maybe someone with more info can correct/supplement these wild
computations.


--
Dave Warkentin
[e-mail]

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

Date: 6 Nov 90 15:29:05 GMT
From: idacrd![e-mail]  (Robert McGwier)
Subject: Re: orbiting bodies

From article <[e-mail]>, by [e-mail] (Pete Ritter):
>
> Does the Moon rotate about its axis (or any other) as it orbits the Earth?
>

    Yes otherwise the moon (up to libration, nutation, etc.) would
change its face to the earth.


> If a non geo-stationary orbiting body always presents the same face to
> the Earth, does it rotate about its axis (or any other) as it orbits?
>

A spacecraft in orbit without spin appears to rotate as it changes its
position in orbit.  The only way for a spacecraft in <ANY> orbit to
constantly present the same face to you the ground based observer is
to have a spinning. This spinning could get quite complicated if
the orbit is not circular, not geostationary, and you are not at the
center of the earth ;-).


> Does a geo-stationary satellite which always presents the same face to
> its primary rotate about its axis (or any other) as it orbits?
>
>

    Answered above.
Bob
--
____________________________________________________________________________
    My opinions are my own no matter    |    Robert W. McGwier, N4HY
    who I work for! ;-)            |    CCR, AMSAT, etc.
----------------------------------------------------------------------------

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

Date: 7 Nov 90 16:16:48 GMT
From: eru!hagbard!sunic!news.funet.fi!tukki.jyu.fi!jyu.fi![e-mail]  (Otto J. Makela)
Subject: Re: LNLL Inflatable Stations

In article <[e-mail]> [e-mail] ("Allen W. Sherzer") writes:
[...]
   After final testing, the entire Earth Station is deflated and packed
   into a Delta or Titan derived HLV and launched. The crew follows on
   a Delta, Atlas, or the Shuttle. They inflate the station and dock.

Question: what would the crew go up in, if not the Shuttle ?  I was under
the impression that the Apollo capsules were the last crew transport
devices built before the Shuttle became available.  Would some be
(re)built for this purpose only ?  Sounds expensive...
--
   /* * * Otto J. Makela <[e-mail]> * * * * * * * * * * * * * * * * * * */
  /* Phone: [phone], BBS: [phone] (CCITT, Bell 24/12/300) */
 /* Mail: Kauppakatu 1 B 18, SF-40100 Jyvaskyla, Finland, EUROPE         */
/* * * Computers Rule 01001111 01001011 * * * * * * * * * * * * * * * * */

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

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Date: 26 Oct 90 17:52:31 GMT
From: usc!samsung!umich!sharkey!cfctech!teemc!fmeed1![e-mail]  (Russ Cage)
Organization: Ford Motor Co., Electronics Div., Dearborn, MI
Subject: Re: You Can't Expect a Space Station to be Cheap
References: <[e-mail]>, <[e-mail]>, <[e-mail]>
Sender: [e-mail]
To: [e-mail]

In <[e-mail]> [e-mail] (Charles Frank Radley) writes:
>Sorry about the double spacing, but the editor on this system
>does it every time I try to upload a pre-prepared message.

If you are ASCII-uploading to a Unix system, strip linefeeds on upload.

>  I thought the HLV would be reusable....There is some psychology
>involved, Shuttle exists, HLV does not.   There is a risk in
>betting that a non-existent HLV will work.  Once again, the
>problem of credibility.

There is no risk in betting that the Titan and Delta motors will
fire, that SRB's will provide thrust (with an occasional failure),
and that fuel tanks will hold fuel.  The risk is that they might
exhibit new and unwelcome behavior when bolted together, which
is a rather small risk.  The costs of refurbishing an entirely
new vehicle based on brand-new technology in order to use it
over again are much riskier to any proposition depending on
economics.  (And you SHOULD know that.)

>+ Does Freedom figure in the cost of developing the Shuttle in
>+ their costing?
>
>They don't have to because Shuttle exists and its development is
>previously paid for.
>
>+ they also use subsidized numbers.
>
>The tapayer is subsidizing himself ?  I do not understand.

Is your mis-understanding the result of not reading the previous
material posted to this newsgroup, or deliberate?

Shuttle's operating costs relating to Fred are not entirely charged
to Fred.  The taxpayer is subsidizing the Fred launch and operations
budget with the Shuttle budget, to make the former less outrageous.
After this is paid for, how much space science, materials science
and life science will get done (the avowed purpose of Fred)?

>+ This HLV will cost less than ONE shuttle flight to  develop.
>+It will lift twice what the Shuttle lifts for a quater to half
>+the launch costs.
>
>Sounds good.   Good enough to get private venture
>capital.....right ?   So why don't they just go do it ?  Why do
>they want the taxpayer to underwrite it ?

You really aren't listening, are you?

The answer is, they don't.  They just won't build it without a
customer (sensible, no?).  The taxpayer is NOT underwriting
anything, the taxpayer is BUYING something (and paying on
delivery); vendor's risk.  Do you understand the difference?

>+ Besides, they plan to fly it 20 times. Maybe somebody else can
>+ also use it. However even at one use it will be far far cheaper
>+ than using the Shuttle.
>
>Now you have taken the bait......who is going to pay for those 20
>flights ?

Uh, people who look at the pricetag and find it attractive?
Remember, the development is PAID FOR by the first launch.
Additional launches are just gravy.

> Not at all, SSX is also 90 % off the shelf.  And for a traffic
>projection of 20 flights will be cheaper than an expendable HLV.

Show me anything like SSX which has flown even 2 flights, and
come within a factor of 2 of its cost target.

> + Given the cost of the NASA ACRV this comes as no suprise. Why
>+ not just buy a Soyuz?
>
>Because that opens other questions, like why not launch Freedom
>or LLNL using Energia ?

Excellent idea!  Why not?  }:->

It does bring up the question:  Is Fred a welfare program for the
aerospace contractors, or a platform for science work?  If the
former, we should put it in the HHS budget.  If the latter, we
should look at buying from whoever is cheapest and most dependable.
If that is the Soviets, so be it.
--
Russ Cage    Ford Powertrain Engineering Development Department
Work:  itivax.iti.org!cfctech!fmeed1!cage   (CHATTY MAIL NOT ANSWERED HERE)
Home:  [e-mail]  (All non-business mail)
Member:  HASA, "S" division.

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

End of SPACE Digest V12 #537
*******************