Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_5/V15NO534.TXT

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Date: Sat, 12 Dec 92 05:07:08
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #534
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat, 12 Dec 92       Volume 15 : Issue 534

Today's Topics:
                   absolutely, positively overnight
                               DC info
                dialog between D. Goldin and C. Sagan
        Electronic Journal of the ASA (EJASA) - December 1992
           Terminal Velocity of DCX? (was Re: Shuttle ...)

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

Date: 11 Dec 92 00:45:47 GMT
From: Anthony J Stieber <[e-mail]>
Subject: absolutely, positively overnight
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]>, [e-mail] (Anthony J Stieber) writes:
>But they didn't call the SR-71 the Recon-STRIKE-71 before LBJ's mangling for
>nothing.

Yep.  And I also heard about the drone launch accident that downed both
the drone and the host SR-71.  Are the speeds SR-71 craft fly at
considered hypersonic?  In any case release of anything in an
atmosphere at high speeds is problematic.

I suppose that a DC could be used like an ICBM bus and release
ordnance while suborbital above the atmosphere.  Physics packages, etc.
would reenter on their own.  The DC would put some distance between
itself and the payload and either reenter as well or burn some fuel and
take an orbit or two, perhaps for another bombing run.  Bomb deorbit
burn motors would make it easier for a bomber to loiter for days and not
burn fuel to put bombs in a reentry trajectory.  Price is certainly
less than a B-2.

Hmmm, I can see why the Air Force is interested...
--
<-:(= Anthony Stieber    [e-mail]   uwm!uwmcsd4!anthony

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

Date: Thu, 10 Dec 1992 23:27:48 GMT
From: Brad Whitehurst <[e-mail]>
Subject: DC info
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>
>Question about the RL-10:  what intake pressure do its pumps require
>to avoid cavitation?  Hudson emphasizes that reducing this pressure
>is important in designing an SSTO, as lower pressure tanks can be
>lighter.
>
>    Paul F. Dietz

    As a data point, I was flipping through the new Aerospace
America, which gave the rated thrust for the newest RL-10 at a
combustion chamber pressure of 1000 psi.  I suppose one could hazard
some guesses on fuel pressures from that, although not knowing the
pump's pressure ratio, the inlet pressure is still unknown. Just FYI.
    The same issue also notes that composite test tanks have been
built for the NASP effort.  Liquid H2 inside, 250 degrees F on the
outside!

--

Brad Whitehurst    |   Aerospace Research Lab
[e-mail] |   We like it hot...and fast.

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

Date: Thu, 10 Dec 1992 23:10:13 GMT
From: "Loren I. Petrich" <[e-mail]>
Subject: dialog between D. Goldin and C. Sagan
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Richard Ottolini) writes:

>Scattered throughout the evening were references to national politics.
>Sagan joked about Republican party follies.

    I'd like to see some examples.



--
/Loren Petrich, the Master Blaster
/[e-mail]

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

Date: Thu, 10 Dec 1992 22:24:17 GMT
From: Larry Klaes <[e-mail]>
Subject: Electronic Journal of the ASA (EJASA) - December 1992
Newsgroups: sci.astro,sci.space,sci.space.shuttle,sci.misc,alt.sci.planetary

                          THE ELECTRONIC JOURNAL OF
                  THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                      Volume 4, Number 5 - December 1992

                         ###########################

                              TABLE OF CONTENTS

                         ###########################

          * ASA Membership and Article Submission Information

          * Further Analysis of EVA Self-Rescue Data - Adam R. Brody

          * Transparency Films for Astrophotography - Brian G. Segal

                         ###########################

                         ASA MEMBERSHIP INFORMATION

        The Electronic Journal of the Astronomical Society of the Atlantic
    (EJASA) is published monthly by the Astronomical Society of the
    Atlantic, Incorporated.  The ASA is a non-profit organization dedicated
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        Council - Bill Bagnuolo, Bill Black, Mike Burkhead, Frank Guyton,
                  Larry Klaes, Ken Poshedly, Jim Rouse, Tano Scigliano,
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                  Cindy Weaver, Bob Vickers


                             ARTICLE SUBMISSIONS

        Article submissions to the EJASA on astronomy and space exploration
    are most welcome.  Please send your on-line articles in ASCII format to
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        or - ...!decwrl!verga.enet.dec.com!klaes
        or - [e-mail]
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                                DISCLAIMER

        Submissions are welcome for consideration.  Articles submitted,
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    necessarily those of the ASA.  This Journal is Copyright (c) 1992
    by the Astronomical Society of the Atlantic, Incorporated.


                     FURTHER ANALYSIS OF EVA SELF-RESCUE DATA

                                   IAA-92-0385

                                  Adam R. Brody
               Senior Aerospace Engineer/Experimental Psychologist
                                Sterling Software
                            NASA Ames Research Center
                        Moffett Field, California, U.S.A.

              Copyright (c) 1992 by Sterling Software.  Published
              by the International Astronautical Federation (IAF),
              with permission.

        Abstract

        A means for rescuing a stranded Extra-Vehicular Activity (EVA)
    astronaut is necessary to ensure future safe space station operations.
    One promising device is a hand-held thruster similar to the Hand-Held
    Maneuvering Unit (HHMU) from the GEMINI and SKYLAB programs of the
    1960s and 1970s.

        A study was performed in the Virtual Interactive Environment
    Workstation (VIEW) at NASA Ames Research Center.  Three Initial
    (Separation) Velocities (0.5, 1.0, and 1.5 m/s) were crossed with five
    Initial Spin Velocities (0, #177#0.1, #177#0.3) to yield 15 different
    trials.  An Attitude Hold system was also modeled, which, when
    combined with the 15 combinations of separation and spin velocity,
    provided 30 distinct trials.

        Recent examinations of the data reveal that Initial (Separation)
    Velocity and Initial Spin Velocity each produced main effects and
    combined to produce an interaction effect on Solution Time.  Solution
    Time increased with Initial Velocity and absolute Initial Spin
    Velocity.  Final Roll Angle also increased Initial Spin Velocity.
    Attitude Hold Fuel increased with absolute Initial Spin Velocity.
    Interaction effects revealed that main effects were less pronounced
    at the lowest Initial Velocity level.

        Introduction

        There are a number of organizations in the United States
    developing devices to be used to return a stranded EVA astronaut to
    a space station after an accidental separation.  Some of the devices
    merely extend the reach of the stranded crewperson with a pole or
    other apparatus.  These will only work when the separation velocity is
    so small that the crew can unstow and operate the rescue tool before
    s/he drifts further than the instrument's maximum operational range.
    Once this maximum range is exceeded, propulsive techniques must be
    used.

        One possible propulsive device is the Hand-Held Maneuvering Unit
    (HHMU) initially used in the United States' GEMINI program.  Three
    different models (varying by propellant type, total delta-v, and other
    attributes) were developed and used.  Experimentation continued in the
    SKYLAB program.

        The device simulated in the current series of experiments is
    analogous to the HHMU.  However, neither the thruster configuration
    nor the propellant is specified.  The amount of thrust is recorded as
    a thrusting duration.  The thrust force multiplied by the duration
    yields the impulse, which when divided by the system mass, yields the
    change in velocity or delta-v.  This value for delta-v may then be
    used to determine propellant mass for any combination of propellant
    specific impulse and thruster configuration.

        The current study was performed in the Virtual Interactive
    Environment Workstation (VIEW) laboratory at the NASA Ames Research
    Center.  This simulator facility provided the user with a stereoscopic
    visual image of the space station from which s/he has become separated.
    The visual scene was altered not only by the equations of motion
    governing orbital flight, but also by the changes in orientation and
    position of the operator's head.  In this way, an effective EVA
    simulation was realized.

        This study demonstrated the viability of using VIEW as an EVA
    simulation facility.  It also revealed separation velocity to be the
    most important factor characterizing a separation scenario with fuel
    consumption, maximum range, and time to reach maximum range increasing
    linearly with separation velocity.  In addition, no significant
    benefits from an attitude hold capability were uncovered (although a
    null effect cannot be proven).  EVA trainers at the Johnson Space
    Center in Houston, Texas, were sufficiently impressed with the study
    that they considered using the facility for astronaut EVA rescue
    training.  This collaboration was precluded by lack of funding.

        Many of the results of this study were presented elsewhere.
    [1, 2, 3]  Space limitations prevented inclusion of all the results;
    additional results are described here.  Also, the stated result that
    no statistically significant solution time effects were found was
    incorrect.  These effects will also be discussed here.

        Method

        One highly-trained subject was used in this study.  The subject,
    situated in the VIEW, experienced sudden separations from the virtual
    space station to which he was previously tethered.  Using hand gestures,
    which commanded the fore and aft firings of a virtual hand-held thruster,

    he effected his returns to the station.  The subject was trained until
    he was able to recover consistently from a variety of separation
    scenarios.

        The subject was presented with an assortment of failure scenarios
    with varying initial velocities, and rotation rates.  The opportunity
    to use attitude hold was allowed on only half the trials.  Since
    preliminary investigations revealed starting location to have less
    of an effect on rescue performance than other input parameters, all
    separations began at the center of mass of the space station.  Motion
    began in the direction of the minus velocity vector.

        Three initial (separation) rates (0.5, 1.0, and 1.5 m/s) were used
    in the study.  These values were selected as appropriate based upon
    separation dynamics tests performed on the KC-135 aircraft.  In these
    tests, test subjects were assisted in achieving the maximum separation
    rates possible; a maximum separation rate of 1.5 m/s (4.5 ft/s) was
    achieved.  The maximum rotation rates were found to be 4.5 RPM (0.47
    rad/s) in roll, 10.1 RPM (1.06 rad/s) in pitch and 5.8 RPM (0.61
    rad/s) in yaw. [4]  The five rotation rates (-0.3, -0.1, 0, 0.1, 0.3
    rad/s) in this study were crossed with the translation rates to yield
    a trial set of 15 different trials.  Initial rates were the same
    about all axes.  Both negative and positive values were used because
    preliminary testing suggested a handedness effect might be present.

        The capability to use attitude hold was added as another factor
    raising the number of distinct trials to 30.  The subject was
    presented with 2 different random orders of these 30 trials in groups
    of 5.  Dependent variables included:  Mission duration, total velocity
    increment, impact velocity, and maximum range from the station along
    all three axes.

        The subject was allowed one attempt at a rescue per trial.  The
    trial was aborted if he passed the station.  These aborted missions
    were immediately reflown.

        The hand-held thruster fired an 8.9 N (2-pound) force along the
    direction of the hand in either the fore or aft direction.  All
    thrusts that were not directed precisely through the center of mass of
    the subject, which was located in the center of the subject's back,
    added rotational motion along one or more axes.

        An 8.9 N (2-pound) thruster requires 31 seconds to accelerate the
    simulated crew mass of 274 kilograms to 1 m/s.  This thrust must be
    through the center of mass to avoid adding rotational motion.  This
    is virtually impossible, so achieving a velocity of 1 m/s typically
    requires more than 31 seconds. [3]

        The simulated space station was located in a 270 nautical mile
    circular orbit around the planet Earth.  Since it was impractical to
    keep up with the rapidly changing design of space station FREEDOM,
    the station was represented by two intersecting 5-meter trusses.  The
    horizontal dimension was 50 meters and the vertical dimension was 100
    meters. [5]

        Results

        A data entry error prevented the discovery of several solution
    time effects that were indeed present.  Initial (separation) velocity
    and initial spin velocity each produced statistically significant main
    effects on solution time.  They also combined for an interaction effect.
    These effects were statistically significant at the five-percent level
    and are discussed here.

        Solution time increased monotonically with initial velocity as
    described in Figure 1.  This effect is intuitive and fits with similar
    effects on fuel consumption, final axial velocity, and maximum range.
    [1, 2, 3]

        This effect was non-linear, however.  Tripling the separation rate
    from 0.5 to 1.5 m/s quadrupled the solution time, for example.  This
    was because the ratio of thrusting time to solution time was lower at
    the two highest separation rates than at 0.5 m/s.  Since proportionately
    less time was spent thrusting at the higher rates, those missions took
    longer than a simple multiple of the fastest response would predict.
    There was more of a "thrust and wait" strategy with the longer missions
    than with the shortest one.  Proportionately more time was spent
    verifying progress at the higher velocity separations than at the
    lower velocity separations.

        Figure Descriptions

        Figure 1:  Initial velocity effect on solution time.  A solution
    time effect was also observed with Initial Spin Velocity as the
    independent variable.  The plot appears as Figure 2.  Fuel consumption
    also increased with initial spin velocity as did maximum range. [1, 2,
    3]  Trials with higher initial spin velocities were more difficult
    from which to recover.

        Figure 2:  Initial spin velocity effect on solution time.
    Separation velocity and spin velocity combined to produce an
    interaction effect on solution time as described in Figure 3.
    Separations at a rate of 0.5 m/s were not affected by spin velocity
    as much as separations at the two higher rates.  Rapid response times
    precluded greater impact of initial spin rate.  The asymmetries in the
    plots are due to a handedness effect.  The thruster commands were sent
    with the right hand only.

        Figure 3:  Separation and spin velocity interaction. Initial spin
    velocity also produced a main effect on final roll angle.  Interaction
    effects with attitude hold, and separation velocity x initial spin
    velocity, and separation velocity x initial spin velocity x attitude
    hold interactions were also present.

        Final roll angle increased with initial spin velocity as described
    in Figure 4.  Since final roll velocity (V spin Xf) remained close to
    initial spin velocity [1, 2, 3] and solution times were greater for
    higher initial spin rates than for lower rates, final roll angle was
    proportional to initial spin velocity.  The more time the subject spun
    at a given rate, the greater the final angle was.

        Figure 4:  Final Roll Angle verses Initial Spin Velocity Two
    interaction effects were observed in the final roll angle data.
    Attitude hold and separation velocity were the disturbing factors
    leading to inconsistent main effects.  When the subject had the
    capability of using attitude hold, the final roll angle was much
    closer to zero than when attitude hold was unavailable.  This effect
    is described in Figure 5.

        Figure 5:  Attitude Hold x Initial Spin Velocity Interaction.
    A two-way interaction between separation velocity and initial spin
    velocity was also discovered.  This effect appears in Figure 6.
    Again, the curve for the 0.5 m/s separation velocity data is more
    shallow and less pronounced than the other curves.  At higher
    separation velocities, the effect of initial spin velocity is
    more prominent.

        Figure 6:  Initial Spin Velocity x Separation Velocity
    Interaction.  A second-order interaction of Separation Velocity x
    Initial Spin Velocity x Attitude Hold was also revealed by the data.
    The effects appear as Figures 7a and 7b for the disabled and enabled
    Attitude Hold conditions respectively.  The use of attitude hold
    greatly reduced the final roll angle.  Again, the curve for the
    0.5 m/s data was shallower than those for the other two.

        Figure 7a:  Second order interaction with Attitude Hold Disabled.

        Figure 7b:  Second order interaction with Attitude Hold Enabled.

        The data from trials in which Attitude Hold was available were
    looked at separately to determine if there were any effects regarding
    number of attitude hold commands or attitude hold fuel used along any
    particular axis.  The Pitch Attitude Hold data appear as a U-shaped
    plot in Figure 8.  More pitch attitude hold fuel was used at greater
    initial spin rates.

        Physically, more fuel is needed to eliminate higher initial spin
    rates than lower rates.  The moment of inertia for the pitch axis
    was 108 kg-m2.  An 8.9 N thruster at the end of a 1-meter moment
    arm produces a torque of 8.9 N-m.  These values yield an angular
    acceleration of 0.08 rad/s2.  At this rate, 1.25 s of thrust are
    required to produce a spin rate of 0.1 rad/s.  Similarly, 3.75 s
    are needed to produce a rate of #177#0.3 rad/s.

        The data in Figure 8 reveal actual (simulator) values to be fairly
    close to theoretical values.  In some cases, the subject reduced some
    of the pitching himself, thus reducing the amount of time the pitch
    attitude hold was needed.  In other cases, the subject contributed to
    the rotational motion and the attitude hold system had to work harder
    to make up for this addition.

        Figure 8:  Pitch Attitude Hold Fuel.  An interaction effect with
    Separation Velocity and Initial Spin Velocity was also uncovered with
    these data.  Again, the 0.5 m/s data produced the shallowest curve.
    Pitch Attitude Hold fuel increased with separation velocity.

        Figure 9:  Initial Spin Velocity x Separation Velocity Interaction
    for Pitch Attitude Hold Fuel.

        Discussion

        In every interaction effect involving Initial Velocity discussed
    here, and all cases (except final out-of-plane velocity) listed
    elsewhere, [1, 2, 3] the curve for the lowest Initial Velocity was the
    shallowest of the three.  The lower solution times associated with the
    lowest separation velocity (average = 51 s) prevented the curves from
    taking a shape similar to those representing the higher velocity data.
    The solution times were too short to let some of the effects come
    through.  Shorter solution times precluded the development of certain
    effects in other studies also. [6, 7]  There is a qualitative
    distinction between self-rescue from a separation velocity of 0.5 m/s
    and rescue from higher rates.  More research is needed to better
    quantify these effects.

        Preliminary simulation results indicate that a hand-held thruster
    is capable of serving as an EVA self-rescue device.  Its utility is
    greater than any physical extension of the crewmember's body since it
    has a greater range of operation.  Further study, including a flight
    experiment on Space Shuttle Mission STS-49 (May of 1992), will reveal
    more about the capabilities and deficiencies of such a system.

        Other parameters to be examined include thruster magnitude and
    system geometry.  Motion-base carriage and air bearing floor facilities
    can also contribute as described elsewhere. [1, 2, 3]  This is a field
    of study in its infancy and more attention and funding is encouraged.

        References

    1.  Brody, Adam R., R. Jacoby, and S. R. Ellis, "Simulation of
        Extra-Vehicular Activity (EVA) Self-Rescue", SAE Technical Paper
        911574, Warrendale, Pennsylvania, July 1991.

    2.  Brody, Adam R., R. Jacoby, and S. R. Ellis, "EVA Self-Rescue
        Simulation in the Virtual Interactive Environment Workstation
        (VIEW)", Space Safety and Rescue 1990-1991, Science and Technology
        Series, American Astronautical Society, San Diego, California,
        in press.

    3.  Brody, Adam R., R. Jacoby, and S. R. Ellis, "EVA Self-Rescue Using
        a Hand-Held Thruster", JOURNAL OF SPACECRAFT AND ROCKETS, in press.

    4.  Porter, S., "Separation Dynamics Tests," 1989.

    5.  Brody, Adam R., R. Jacoby, and S. R. Ellis, "Man Overboard!  What
        Next?", International Academy of Astronautics IAA-91-584, Paris,
        France, October 1991.

    6.  Brody, Adam R., S. R. Ellis, A. J. Grunwald, and R. F. Haines,
        "Interactive Displays for Trajectory Planning and Proximity
        Operations", JOURNAL OF SPACECRAFT AND ROCKETS, in press.

    7.  Brody, Adam R. and S. R. Ellis, "Effect of an Anomalous Thruster
        Input During a Simulated Docking Maneuver", JOURNAL OF SPACECRAFT
        AND ROCKETS, Volume 27, Number 6, 1990, pages 630-633.

        About the Author -

        Adam R. Brody received S.B. and S.M. degrees in Aeronautics and
    Astronautics from the Massachusetts Institute of Technology (MIT) in
    Cambridge, Massachusetts, and a diploma as a member of the founding
    conference of the International Space University (ISU).  Adam also
    received his M.A. degree in Psychology from San Jose State University
    in California.

        Adam is a senior aerospace engineer/experimental psychologist
    for Sterling Software, Palo Alto, California.  Among the NASA Ames
    Research Center organizations with which he has worked are the
    Centrifuge Facility Project Office, Human Interface Research Branch,
    EVA Systems Branch, and the Aerospace Human Factors Research Division.
    Adam is the author of over thirty-five research papers on various
    topics relating to performance aspects of humans in space.  Adam
    pioneered a comprehensive study of the human factors and manual
    control aspects of orbital flight and he developed the Space Station
    Proximity Operations Simulator at Ames for his studies.  He also
    initiated a research program to quantify EVA rescue requirements, and
    created of an orbital trajectory planning tool for the Macintosh
    computer system.

        Adam's research interests include the human factors and manual
    control requirements of space station proximity operations and other
    manned space flight operations.  Recent work includes development
    and simulation of an EVA self-rescue technique using the Virtual
    Interactive Environmental Workstation (VIEW).  Currently, he serves
    as the human factors expert on the systems engineering staff of the
    Centrifuge Facility Project Office at Ames, where he developed the
    Payload Resource In Space Monitor (PRISM) for tracking resources on
    the FREEDOM space station.  He is currently using object-oriented
    rapid prototyping to develop software requirements for the space
    station facility.

        Adam is a member of the Space Operations and Support Technical
    Committee of the American Institute of Aeronautics and Astronautics,
    where he is chairman of the Human Factors, Automation and Robotics
    Sub-committee.  He is also a member of the National Air and Space
    Museum, the Union of Concerned Scientists, a founding sponsor of the
    CHALLENGER Center, and a charter member of the Technology Center of
    Silicon Valley.  His biography is listed in Personalities of America,
    the Dictionary of International Biography, Who's Who of Emerging
    Leaders in America, Who's Who Among Young American Professionals,
    and Who's Who in the West.

        Adam is the author of "Soviet Spacecraft Docking Experience",
    published in the October 1992 issue of the EJASA.

        Adam may be reached through the Internet at either:

        [e-mail] or [e-mail]


                    TRANSPARENCY FILMS FOR ASTROPHOTOGRAPHY

                               by Brian G. Segal

        Reprinted with permission from the March-April 1991 issue of
        NOVA NOTES, the Newsletter of the Halifax Centre of The Royal
        Astronomical Society of Canada (RASC).

        The thought of tools for astrophotography usually brings to mind
    images of huge apertures, fluorite elements, exotic guiders, freezing
    cold cameras bathed in dry ice (usually redundant in Canada), dead
    accurate drive systems, the soft red glow of reticules and tired eyes
    - not to mention those supportive, understanding spouses condemned to
    yet another night of just sitting there in the dark!

        However, given a decent array of hardware, the most important
    consideration facing the aspiring cosmic snapshooter is the choice of
    "weapons", otherwise known as film.  There is a kind of decision
    tree that one must work through:  Black and white or color; print or
    transparency; fine and slow or grainy and fast; Kodak, Fuji, Konica,
    Illford, etc..

        Not surprisingly, many astro-shooters tend to specialize.  Given
    the time it takes to make astronomical images (other than the Moon or
    Sun) and the number of opportunities for total, partial, or incidental
    SNAFUs, simplification is a good strategy.

        Consequently, my astrophotographic odyssey has been mostly
    confined to the use of various transparency (slide) films.  They
    are my medium of choice.  Different ones are suitable for different
    applications.  I have done considerable work with EKTACHROME 400,
    KODACHROME 64, and FUJICHROME 50, 100, 400, and 1600.  I have also
    shot FUJICHROME 400 at an effective exposure value of ISO 800 and
    had it push processed.

        The slower films have been used exclusively for solar photography
    and some lunar when the Moon is at least at first quarter phase.  The
    only limiting factor in this situation is the mechanical stability of
    your system.  The exposures have to be made on the long side, compared
    with the focal length of the lens.  A prime focus shot of the Sun taken
    on an unstable 2000 mm scope will blur at the slightest vibration unless
    you can shoot at 1/2000th of a second, which is unlikely.  If you are
    looking at shutter speeds of from one second to 1/500th of a second,
    you had better have a real solid mount and lock up your camera's mirror
    if it is an SLR system.

        I have had good results with KODACHROME 64 and both FUJICHROME 50
    and 100 when shooting the Sun with a Thousand Oaks full aperture solar
    filter.  Effective focal lengths of up to 25,000 mm through eyepiece
    projection have yielded surprisingly good results on calm days.
    Naturally at the higher magnifications various factors come into play,
    including the amount of glass in the system, the seeing, and the care
    taken by the photographer.

        I have also used both EKTACHROME 400 and FUJICHROME 400 for this
    type of photography.  The trade off is a cooler color cast and a lot
    more grain, especially during the longer exposures.  Generally, we are
    told, slow films have better reciprocity characteristics than faster
    ones:  There seems to be some substance to that claim.  However, you
    do achieve between a two to three-stop advantage, which translates to
    faster shutter speeds and less camera shakes - in theory, anyway!

        I have also used pushed FUJICHROME 400 for lunar shots using a
    1000 mm f/11 Maksutov.  The results were surprisingly good and allowed
    me to photograph an almost full Moon without a drive.

        Deep sky work is a very different challenge.  All but the
    brightest objects require relatively long exposures (to a daytime
    photographer, anything longer than a few seconds is very long).  Even
    with the very fast print films (ISO 3200), ten minutes would be a
    minimum exposure for the majority of diffuse and faint objects.  As
    film speed decreases, exposure length grows exponentially.  Each stop
    represents a doubling of exposure time as the ISO value is reduced.

        Each doubling of exposure time increases the risk of any number of
    problems, from the gradual accumulation of dew or frost to unfortunate
    happenstance - like sneezing your head into the eyepiece, resulting in
    possible eye damage and shaking the optics.

        As any slide presentation will demonstrate, various emulsions have
    very different characteristics.  There are some factors which will
    influence the choice of films.  While EKTACHROME 400 tends to bring
    out certain red nebular emissions very effectively, it suffers from
    a lower contrast than its FUJICHROME 400 cousin.  In fact, the sky
    background tends to a kind of purplish cast while the FUJI retains
    very black skies over fairly long exposures.

        Naturally the seeing and general sky conditions have to be
    comparable, but certainly my experience over a range of targets and
    nights has confirmed this situation.  I do find, however, that the
    FUJI requires more exposure for certain objects, particularly
    planetaries.

        FUJICHROME RSP 1600 is the fastest transparency film in the FUJI
    line.  Its optimum rated value is ISO 1600, although it can be pulled
    to ISO 800 or pushed to ISO 3200.  Although KODAK makes EKTACHROME
    P800/1600, a film that makes similar claims, in fact its optimum
    rating is ISO 800 with a one or two-stop push possible.  The fact that
    the FUJI product is "comfortable" at 1600 means that the one-stop push
    to 3200 is asking less of the film.  As push processing does have both
    color shift and granular effects on the final image, the less push,
    the better.

        I have used the RSP 1600 in daylight as well as night time
    photography and can attest to its quality.  It has surprisingly fine
    grain characteristics and although rather high in contrast compared to
    a slower chrome film, its color response is quite good.  The higher
    contrast level is a plus in astrophotography.  The skies in exposures
    of up to forty minutes stay quite blue-black with very good color
    range in the stars and gasses.  You will have to be careful of
    several things, though:

        GUIDING:  Very sensitive emulsions gather light at an alarming
    speed.  Any deviations in guiding are preserved obviously and
    mercilessly for all time within seconds.  With ISO 400 films a bit of
    wander due to periodic drive error or distractions of one sort or
    another can be recovered from with little or no evidence. However, a
    quick glimpse at a meteor at the wrong moment with ultra-fast film can
    leave a lasting memory on the emulsion.

        FOGGING:  Ultra-high speed films are very susceptible to ambient
    light, whether from city lights, celestial background light, or that
    yard light your neighbor has installed across the valley just to make
    your observing that much more of a challenge!  The message is to be
    in a dark place and wait *patiently* for astronomical twilight to
    surrender to real night!

        With any transparency processing it is a good idea to write those
    three important words "DO NOT CUT" on the envelope.  Although I always
    take the precaution of exposing the first frame in daylight to give
    the processors a reference frame, I much prefer to cut and mount my
    own slides for two reasons:

        1 - I use a mini-cassette recorder for note-taking during a
    session.  All of the data is subsequently preserved frame by frame.
    Thus, when the film comes back, I simply turn on the tape and review
    the strip of film to my own commentary.  As I cut and mount the
    slides, the information is recorded in indelible ink on the mount.
    You cannot count on the processor to sequentially mount your slides:
    They do screw up at times!

        2 - There are, alas, always shots that do not make it.  Why
    bother having them mounted?

        Another transparency material that is often overlooked is black
    and white negative film.  A negative tonal "slide" can be quite
    dramatic and add another dimension to projectable images.

        Whatever the application you may have planned for your
    astrophotography, transparency films offer a variety of choices and
    possibilities.  If you decide that you have an image that simply must
    be printed, you can always go the route of reversal printing and have
    a large internegative made.  Thus, the versatility of transparency
    films makes them an attractive option for astrophotography.

        Related EJASA Articles -

        "Astrophotography the Easy Way", by Harry Taylor - October 1991

        "Telescopes: A Novice's Guide", by Steven M. Willows - March 1992

        About the Author -

        Brian G. Segal is a visual artist living in Antigonish, Nova
    Scotia, Canada, where he has operated a ceramic design studio with
    his wife, Julia, for the past sixteen years.  In addition, Brian is
    a professional commercial photographer specializing in still life
    and product, architectural, and corporate/industrial photography.

        Brian's hobby is astrophotography, which he tackles with a twenty-
    centimeter (eight-inch) Meade SCT, a bunch of hardware, various slide
    films, and the clear, very dark skies of his rural location - whenever
    it decides to clear up, that is!  Brian is also a member of the
    Executive Committee of the Halifax Centre of the Royal Astronomical
    Society of Canada (RASC).

        Brian's Internet address is: [e-mail]


      THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC

                        December 1992 - Vol. 4, No. 5

                           Copyright (c) 1992 - ASA

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

Date: 11 Dec 92 01:31:58 GMT
From: Pat <[e-mail]>
Subject: Terminal Velocity of DCX? (was Re: Shuttle ...)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Josh 'K' Hopkins) writes:
>[e-mail] (Gary Coffman) writes:
>
>>I support the DC-X tests. The data developed may be useful in later
>>vehicles and the cost is not excessive. Like the X-15, however, I
>>doubt it's design will scale to commercial products. How many airliners
>>are derived from the X-15? The SR71 is the only manned vehicle that vaguely
>>resembles the X-15 and it's flight systems are entirely different. And
>>it's being retired as not cost effective for it's mission.
>
>Actually, I think shuttle derived a fair amount of value from the X-15 research
>even if it doesn't look the same.  In addition saying that the SR-71 is being


I imagine that the X-15, set up a huge amount of data for the NASP as well
as the STS.  the X-15 also probably provided test data for the ICBM
re-entry vehicle design.  i think NASA programs such as SABER?, HL-20,
...  pulled data from the X-15.  the X -15 also procided a lot of data
on RCS systems,  redundant system design and thermal stress design.

The only reason commercial products did not come out of the entire plane
was that we decided to run away from space during the Nixon administration.

Goldin was just on TV, talking abou;the X-15, and how 25 years ago we
stepped away from the cutting edge.  now if we had kept pushing forward,
instead of deciding that attacking small asian countries was a more
noble purpose for the US,  we would have regular trips to mars by now.

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

End of Space Digest Volume 15 : Issue 534
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