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From:
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Newsgroups: sci.space.tech,sci.space.science,sci.answers,news.answers
Subject: Space FAQ 10/13 - Controversial Questions
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Compilation copyright (c) 1994, 1995, 1996 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://www.jsc.nasa.gov/sa/sd/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.
More detailed discussions of the Face, including raw and processed
imagery and discussion of plans for observation by the upcoming Mars
Global Surveyor, are at
http://barsoom.msss.com/education/facepage/face.html
http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars.html#controversy
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
