500 MB Nyheder Direkte fra Internet 2/500 MB nyheder direkte fra internet CD 2.iso/start/data/text/faq-1327.txt

Text File | 1995-05-06 | 17KB | 347 lines

Archive-name: space/controversy
Last-modified: $Date: 95/05/01 22:20:08 $

    Compilation copyright (c) 1994 by Jonathan P. Leech. This document may
    be redistributed in its complete and unmodified form. Other use requires
    written permission of the author.

CONTROVERSIAL QUESTIONS

    These issues periodically come up with much argument and few facts being
    offered. The summaries below attempt to represent the position on which
    much of the net community has settled. Please DON'T bring them up again
    unless there's something truly new to be discussed. The net can't set
    public policy, that's what your representatives are for.


    SPACE SHUTTLE MISSION COSTS

    The answer depends heavily on assumptions, some of which are:

    - What costs are being spread over missions?
    - What's the shuttle flight rate?
    - Are figures adjusted for inflation (constant dollars) or not?
    - Is the expense of periodically building replacement orbiters (such
        as Endeavour) included?

    People arguing over shuttle costs on the net are usually arguing from
    different assumptions and do not describe their assumptions clearly,
    making it impossible to reach agreement. To demonstrate the difficulty,
    here are a range of flight cost figures differing by a factor of 35 and
    some of the assumptions behind them (all use 1992 constant dollars).

    $45 million - marginal cost of adding or removing one flight from
        the manifest in a given year.

    $414 million - NASA's average cost/flight, assuming planned flight
        rates are met and using current fiscal year data only.

    $1 billion - operational costs since 1983 spread over the actual
        number of flights.

    $900 million - $1.35 billion - total (including development) costs
        since the inception of the shuttle program, assuming 4 or 8
        flights/year and operations ending in 2005 or 2010.

    $1.6 billion - total costs through 1992 spread over the actual
        number of flights through 1992.

    For more detailed information, see the Aviation Week Forum article by
    Roger A. Pielke, Jr.: "Space Shuttle Value Open To Interpretation", July
    26, 1993, pg. 57.


    WHAT HAPPENED TO THE SATURN V PLANS

    Despite a widespread belief to the contrary, the Saturn V blueprints
    have not been lost. They are kept at Marshall Space Flight Center on
    microfilm. The Federal Archives in East Point, GA also has 2900 cubic
    feet of Saturn documents. Rocketdyne has in its archives dozens of
    volumes from its Knowledge Retention Program. This effort was initiated
    in the late '60s to document every facet of F-1 and J-2 engine
    production to assist in any future re-start.

    The problem in re-creating the Saturn V is not finding the drawings, it
    is finding vendors who can supply mid-1960's vintage hardware (like
    guidance system components), and the fact that the launch pads and VAB
    have been converted to Space Shuttle use, so you have no place to launch
    from.

    By the time you redesign to accommodate available hardware and re-modify
    the launch pads, you may as well have started from scratch with a clean
    sheet design.

    Other references:

    Several AIAA papers delivered in recent years discuss reviving the
    Saturn V. For example, AIAA paper 92-1546, "Launch Vehicles for the
    Space Exploration Initiative". This paper concluded that a revived
    Saturn V was actually cheaper than the NLS vehicle.

    An overview of the infrastructure still available to support production
    of a 1990s Saturn V and how that vehicle might be used to support First
    Lunar Outpost missions can be found in the December 1993 issue of
    _Spaceflight_, published by the British Interplanetary Society.


    WHY DATA FROM SPACE MISSIONS ISN'T IMMEDIATELY AVAILABLE

    Investigators associated with NASA missions are allowed exclusive access
    for one year after the data is obtained in order to give them an
    opportunity to analyze the data and publish results without being
    "scooped" by people uninvolved in the mission. However, NASA frequently
    releases examples (in non-digital form, e.g. photos) to the public early
    in a mission.


    RISKS OF NUCLEAR (RTG) POWER SOURCES FOR SPACE PROBES

    There has been extensive discussion on this topic sparked by attempts to
    block the Galileo and Ulysses launches on grounds of the plutonium
    thermal sources being dangerous. Numerous studies claim that even in
    worst-case scenarios (shuttle explosion during launch, or accidental
    reentry at interplanetary velocities), the risks are extremely small.
    Two interesting data points are (1) The May 1968 loss of two SNAP 19B2
    RTGs, which landed intact in the Pacific Ocean after a Nimbus B weather
    satellite failed to reach orbit. The fuel was recovered after 5 months
    with no release of plutonium. (2) In April 1970, the Apollo 13 lunar
    module reentered the atmosphere and its SNAP 27 RTG heat source, which
    was jettisoned, fell intact into the 20,000 feet deep Tonga Trench in
    the Pacific Ocean. The corrosion resistant materials of the RTG are
    expected to prevent release of the fuel for a period of time equal to 10
    half-lives of the Pu-238 fuel or about 870 years [DOE 1980].

    To make your own informed judgement, some references you may wish to
    pursue are:

    A good review of the technical facts and issues is given by Daniel
    Salisbury in "Radiation Risk and Planetary Exploration-- The RTG
    Controversy," *Planetary Report*, May-June 1987, pages 3-7. Another good
    article, which also reviews the events preceding Galileo's launch,
    "Showdown at Pad 39-B," by Robert G. Nichols, appeared in the November
    1989 issue of *Ad Astra*. (Both magazines are published by pro-space
    organizations, the Planetary Society and the National Space Society
    respectively.)

    Gordon L Chipman, Jr., "Advanced Space Nuclear Systems" (AAS 82-261), in
    *Developing the Space Frontier*, edited by Albert Naumann and Grover
    Alexander, Univelt, 1983, p. 193-213.

    "Hazards from Plutonium Toxicity", by Bernard L. Cohen, Health Physics,
    Vol 32 (may) 1977, page 359-379.

    NUS Corporation, Safety Status Report for the Ulysses Mission: Risk
    Analysis (Book 1). Document number is NUS 5235; there is no GPO #;
    published Jan 31, 1990.

    NASA Office of Space Science and Applications, *Final Environmental
    Impact Statement for the Ulysses Mission (Tier 2)*, (no serial number or
    GPO number, but probably available from NTIS or NASA) June 1990.

    [DOE 1980] U.S.  Department of Energy, *Transuranic Elements in the
    Environment*, Wayne C.  Hanson, editor; DOE Document No.  DOE/TIC-22800;
    Government Printing Office, Washington, DC, April 1980.)


    IMPACT OF THE SPACE SHUTTLE ON THE OZONE LAYER

    From time to time, claims are made that chemicals released from
    the Space Shuttle's Solid Rocket Boosters (SRBs) are responsible
    for a significant amount of damage to the ozone layer. Studies
    indicate that they in reality have only a minute impact, both in
    absolute terms and relative to other chemical sources. The
    remainder of this item is a response from the author of the quoted
    study, Charles Jackman.

    The atmospheric modelling study of the space shuttle effects on the
    stratosphere involved three independent theoretical groups, and was
    organized by Dr. Michael Prather, NASA/Goddard Institute for Space
    Studies.  The three groups involved Michael Prather and Maria Garcia
    (NASA/GISS), Charlie Jackman and Anne Douglass (NASA/Goddard Space
    Flight Center), and Malcolm Ko and Dak Sze (Atmospheric and
    Environmental Research, Inc.).  The effort was to look at the effects
    of the space shuttle and Titan rockets on the stratosphere.

    The following are the estimated sources of stratospheric chlorine:

       Industrial sources:    300,000,000 kilograms/year
      Natural sources:     75,000,000 kilograms/year
      Shuttle sources:      725,000 kilograms/year

    The shuttle source assumes 9 space shuttles and 6 Titan rockets are
    launched yearly. Thus the launches would add less than 0.25% to the
    total stratospheric chlorine sources.

    The effect on ozone is minimal:  global yearly average total ozone would
    be decreased by 0.0065%. This is much less than total ozone variability
    associated with volcanic activity and solar flares.

    The influence of human-made chlorine products on ozone is computed
    by atmospheric model calculations to be a 1% decrease in globally
    averaged ozone between 1980 and 1990. The influence of the space shuttle and
    Titan rockets on the stratosphere is negligible.  The launch
    schedule of the Space Shuttle and Titan rockets would need to be
    increased by over a factor of a hundred in order to have about
    the same effect on ozone as our increases in industrial halocarbons
    do at the present time.

    Theoretical results of this study have been published in _The Space
    Shuttle's Impact on the Stratosphere_, MJ Prather, MM Garcia, AR
    Douglass, CH Jackman, M.K.W. Ko and N.D. Sze, Journal of Geophysical
    Research, 95, 18583-18590, 1990.

    Charles Jackman, Atmospheric Chemistry and Dynamics Branch,
    Code 916, NASA/Goddard Space Flight Center,
    Greenbelt, MD  20771

    Also see _Chemical Rockets and the Environment_, A McDonald, R Bennett,
    J Hinshaw, and M Barnes, Aerospace America, May 1991.


    HOW LONG CAN A HUMAN LIVE UNPROTECTED IN SPACE

    If you *don't* try to hold your breath, exposure to space for half a
    minute or so is unlikely to produce permanent injury. Holding your
    breath is likely to damage your lungs, something scuba divers have to
    watch out for when ascending, and you'll have eardrum trouble if your
    Eustachian tubes are badly plugged up, but theory predicts -- and animal
    experiments confirm -- that otherwise, exposure to vacuum causes no
    immediate injury. You do not explode. Your blood does not boil. You do
    not freeze. You do not instantly lose consciousness.

    Various minor problems (sunburn, possibly "the bends", certainly some
    [mild, reversible, painless] swelling of skin and underlying tissue)
    start after ten seconds or so. At some point you lose consciousness from
    lack of oxygen. Injuries accumulate. After perhaps one or two minutes,
    you're dying. The limits are not really known.

    An expanded discussion of this issue, citing several case studies, may
    be found at

    http://medlib.jsc.nasa.gov/intro/vacuum.html

    References:

    _The Effect on the Chimpanzee of Rapid Decompression to a Near Vacuum_,
    Alfred G. Koestler ed., NASA CR-329 (Nov 1965).

    _Experimental Animal Decompression to a Near Vacuum Environment_, R.W.
    Bancroft, J.E. Dunn, eds, Report SAM-TR-65-48 (June 1965), USAF School
    of Aerospace Medicine, Brooks AFB, Texas.

    _Survival Under Near-Vacuum Conditions_ in the article "Barometric
    Pressure," by C.E. Billings, Chapter 1 of _Bioastronautics Data Book_,
    Second edition, NASA SP-3006, edited by James F. Parker Jr. and Vita R.
    West, 1973.


    HOW THE CHALLENGER ASTRONAUTS DIED

    The Challenger shuttle was not destroyed in an explosion. This is a
    well-documented fact; see the Rogers Commission report, for example.
    What looked like an explosion was fuel burning after the external tank
    came apart.

    The medical/forensic report by Joe Kerwin's team confirmed what was
    already suspected for other reasons: at least some of the crew were not
    only alive, but conscious, for at least a few seconds after the orbiter
    broke up. The forces of the breakup were not violent enough for a high
    probability of lethal injury, and some of the emergency-escape air packs
    had been turned on manually.

    However, unless the cabin held pressure -- which could not be determined
    positively, but seems unlikely -- they almost certainly were unconscious
    within seconds, and did not recover before water impact. They did not
    have oxygen masks (the emergency-escape packs held air, not oxygen, for
    use in pad emergencies) and the cabin apogee was circa 100,000ft.

    The circa 200MPH water impact was most certainly violent enough to kill
    them all. It smashed the cabin so badly that Kerwin's team could not
    determine whether it had held pressure or not. Their bodies then spent
    several weeks underwater. Their remains were recovered, and after the
    Kerwin team examined them, they were sent off to be buried.

    The Kerwin report was discussed in Aviation Week and other sources at
    the time. World Spaceflight News printed the full text.


    USING THE SHUTTLE BEYOND LOW EARTH ORBIT

    You can't use the shuttle orbiter for missions beyond low Earth orbit
    because it can't get there. It is big and heavy and does not carry
    enough fuel, even if you fill part of the cargo bay with tanks.

    Furthermore, it is not particularly sensible to do so, because much of
    that weight is things like wings, which are totally useless except in
    the immediate vicinity of the Earth. The shuttle orbiter is highly
    specialized for travel between Earth's surface and low orbit. Taking it
    higher is enormously costly and wasteful. A much better approach would
    be to use shuttle subsystems to build a specialized high-orbit
    spacecraft.

    [Yet another concise answer by Henry Spencer.]


    THE "FACE ON MARS"

    There really is a big rock on Mars that looks remarkably like a humanoid
    face. It appears in two different frames of Viking Orbiter imagery:
    35A72 (much more facelike in appearance, and the one more often
    published, with the Sun 10 degrees above western horizon) and 70A13
    (with the Sun 27 degrees from the west). The feature, about 2.5 km
    across, is located near 9 degrees longitude, +41 degrees N latitude,
    near the border between region Arabia Terra and region Acidalia
    Planitia.

    Science writer Richard Hoagland has championed the idea that the Face is
    artificial, intended to resemble a human, and erected by an
    extraterrestrial civilization. Most other analysts concede that the
    resemblance is most likely accidental. Other Viking images show a
    smiley-faced crater and a lava flow resembling Kermit the Frog elsewhere
    on Mars. There exists a Mars Anomalies Research Society (see address for
    "Mars Research" below) to study the Face.

    Due to the unfortunate loss of the Mars Observer mission, this issue
    will remain open for future missions. In the meantime, speculation about
    the Face is best carried on in the altnet group alt.alien.visitors, not
    sci.space.* or sci.astro.

    Two images of the Face are available in

    ftp://explorer.arc.nasa.gov/pub/SPACE/FAQ/
        Files 33a72pr, 33a72pr.GIF, 70a13pr, 70a13pr.GIF

    These have been subjected to considerable image processing, and so
    should not be used for scientific purposes, just casual viewing.

    Some references:

    V. DiPeitro and G. Molenaar, *Unusual Martian Surface Features*, Mars
    Research, P.O. Box 284, Glen Dale, Maryland, USA, 1982. $18 by mail.

    R.R. Pozos, *The Face of Mars*, Chicago Review Press, 1986. [Account of
    an interdisciplinary speculative conference Hoagland organized to
    investigate the Face]

    R.C. Hoagland, *The Monuments of Mars: A City on the Edge of Forever*,
    North Atlantic Books, Berkeley, California, USA, 1987. [Elaborate
    discussion of evidence and speculation that formations near the Face
    form a city]

    M.J. Carlotto, "Digital Imagery Analysis of Unusual Martian Surface
    Features," *Applied Optics*, 27, pp. 1926-1933, 1987. [Extracts
    three-dimensional model for the Face from the 2-D images]

    M.J. Carlotto & M.C. Stein, "A Method of Searching for Artificial
    Objects on Planetary Surfaces," *Journal of the British Interplanetary
    Society*, Vol. 43 no. 5 (May 1990), p.209-216. [Uses a fractal image
    analysis model to guess whether the Face is artificial]

    B. O'Leary, "Analysis of Images of the `Face' on Mars and Possible
    Intelligent Origin," *JBIS*, Vol. 43 no. 5 (May 1990), p. 203-208.
    [Lights Carlotto's model from the two angles and shows it's consistent;
    shows that the Face doesn't look facelike if observed from the surface]


NEXT: FAQ #11/13 - Space activist/interest/research groups & space publications