SAR Technology Incidental to an NEA Flyby
American
From: http://www.spacefuture.com/archive/the_technical_and_economic_
feasibility_of_mining_the_near_earth_asteriods.shtml:
Application of celestial mechanics shows that (i) simple es-
timates of "global minimum" delta-v can be made; (ii) low-
energy opportunities occur at approx 2-yearly intervals, for
many NEAs; (iii) long synodic periods militate against mul-
tiple-return mining missions; (iv) Earth-return hyperbolic
velocity should be kept low; (v) high-eccentricity targets
require Hohmann transfers, and a short mining season at
aphelion; (vi) low-eccentricity targets may use continuous-
thrusting propulsion, and extended mining season. There is a
growing subset of targets that are intermittently accessible
for an outbound delta-v of under 6 km/s, and offering return
departure delta-v under 2 km/sec.
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How to acquire the spectral data? SAR mapping "flybys" utiliz-
ing a data set similar to the Lunar Prospector Gamma Ray Spec-
trometer revealed that the spectrometer was expected to be 2.5
to 8 times better (w.r.t. peak intensity) than the NaI data
from the Apollos. A higher-Z Bismuth Germinate (BGO) crystal
increases the filtering, or stopping power of gamma rays, and
returns two sets of data for the GRS at 32 second intervals:
"... a BGO spectrum from 0.3 to 9 MeV in each coincidence
(rejected) and anticoincidence (accepted) with the plastic shell.
In principle the accepted spectrum is the cleanest, since all
full energy BGO photopeaks will deposit no energy in the plastic.
However, there is additional information in the rejected spectrum
which can be used to good advantage with respect to
background reduction.
The rejected data consists of gamma rays that had one or more
Compton scattering events in the plastic, in addition to the
partial peak energy deposited in the BGO. This scattering process
mimics the Compton scattering of the elemental spectral emission
lines from the lunar regolith before the gamma rays reach the
LP spacecraft, and so are similar to the continuum background
spectrum which rides below the elemental line spectrum. As such,
a properly scaled version of the rejected spectrum can be sub-
tracted spectrum to reduce continuum spectrum background from the
lunar surface. This second data set was not available in previous
measurements for use in such background reductions."
(From Monte Carlo Simulation of the Gamma Ray Spectrometer Per-
formance on Lunar Prospector, Robert E. McMurray, Jr., Marie C.
Grimmer, William C. Feldman, G. Scott Hubbard, and Steven D.
Zins, NASA Ames Research Center, Moffett Field, CA 94035, Naval
Postgraduate School, Monterey, CA 93943, Los Alamos National
Laboratory, Los Alamos, NM 87545, from the 1997 IEEE Nuclear
Science Synposium, Anaheim, CA p. 602)
For GAMS (Geosynchronous Asteroid Mapping Satellites, an orbital
period is established to yield a ground track in x km. per y
seconds (per 32 second data set). The data sets are binned into
square kilometer pixel bins over the maximum surface area. Dynamic
x-ray imaging provides the resources necessary for rapid processing
(on the order of 8 ms per 7936 pixel channels) for monochromatic
photons. Monochromatic photons are single frequency time-over-
threshold photons with uniform pulse intensity. The scintillation
detector is tuned for reception of single frequency emitted
photons. I have a list of detector specific properties for
transition frequencies of precious metals) that utilize PSPMT
(Position Sensi-tive Photomultiplier Tubes) yielding a hit (with
pulse height and frequency) perform geosynchronization of
coordinates transmission to an orbital or earth-based GAMS mapping
facility. The mapping facility then chooses a destination for the
mining vessel and transmits new programming instructions for
the rendezvous.
However, I do agree with the M.J. Sonter's link describing the
types of propulsion available, utilizing a "steam rocket" with
"solar thermal power is advantageous for extracting metals other than
precious, however considering the time constraints for organizing
such a mission for this alone is not sufficient enough to pay for
the entire mission - the operation would have to require carefully
selecting a landing site to include both primary and precious metals
in order to justify the cost.
Josh
be returned to Earth orbit is water. It will be many decades before
platinum will pay for itself, but water is currently going for around
$5000/kg in LEO. Once there is an orbital hotel, the Case For Water can
be made. Following that logic, if you are already going to extract
water, why not use it outright instead of reproscessing it several
times into LH2. Performance is only part of the game, economic and
servicability factors will reign in a large-scale transport system.
josh
American
Your proposition is correct, assuming there is no cheap
earth-to-orbit technology, which seems to presently be
the case; a political stranglehold on most all of the
presently available technology, particularly for nuclear
propulsion, w/o recognition being given to the less and
non-lethal types, which would enable speedier delivery
of the water ices from places like Europa, which would
justify most or all of the mission priorities that you
are stipulating.
Space hotels - good idea for way stations to the
asteroids, but lousy servicing contract for some escape
to an orbital "Disneyworld". I imagine that somewhere along
the line there would be a greater need established for what
is the more important business, rather than the sightseeing.
One could compete the earth-to-orbit technology with
the orbit-to-orbit technology by assuming that nobody
at an orbital hotel could recieve "Europan" ice w/o
being involved in some part of the mining operation,
even if it involves a "sightseeing tour" to the asteroids.
Josh
hospitals and high-stakes gene research in space, zero-G sports,
freefall casinos. Despite station-keeping needs, LEO is a good starting
location, my own view is that the larger tankfarms will be in HEEO
ellipses and the first truly large space structures at Earth-Moon L1. I
want to see all this and much more in my life, and the key to that is
water.
I'm not going to fully analyze it now, but there is a strong argument
for NEO mining as the way to get water. Phobos is my personal strongest
candidate, with water (and VR tele-ops) as it's first export product.
American robotics have become advanced enough, in my humble opinion, to
drive the profitability sweet-spot toward somewhat higher costs-per
pound. The old number was considered $600/lb - I'm arguing that even
Falcon I's projected price could now produce profitable mining
ventures. When there are dozens of people on-orbit at any time, where
ever it comes from water will be the commodity in demand.
Yes, I'd spend half my time on an asteroidal tour as a miner, as long
as there was fun-time as well.
We're discussing the Phobos-First concept here: