Abstract: If preservation and prosperity
of humanity on the Earth and human settlement of space
are our goals, we should concentrate on a commercial
path to get there. Commercial enterprise has a long
history of fortuitously aiding scientific progress.
We expect radical changes in the cost of earth to
orbit transportation, and in the methods and efficacy
of deep space transportation, within the next two
decades.
A successful space tourism industry, beginning with
suborbital tourism, will greatly drive down the cost
of access to orbit over the next 15 years. Inexpensive
transportation to low Earth orbit is the first requirement
for a great future on the High Frontier. Inexpensive
means the cost associated with a mature transportation
system. A mature system has a cost of three to five
times the cost of the propellant. The first cheap,
reliable and highly reusable rocket engines are just
now appearing in vehicles. With an assured market
and high flight rate, the heretofore glacial progress
in reducing the cost of space transportation is likely
to become rapid. This is the first critical enabling
example of synergy between free market economics and
scientific and technical progress in space. It will
not be the last.
New high power switches and ultracapacitors developed
for the automotive market make possible cheap, robust
and reliable mass driver engines. In space construction,
using masses of nonterrestrial materials make the
gravity tractor technique much more capable than previous
schemes to maneuver asteroids. Ion propulsion will
continue to improve and the first solar sails will
be flown. Advanced robotics will allow remarkable
improvements in productivity. The computing power
available to robots began to follow the exponential
Moore's law less than decade ago. The first commercial
autonomous mobile robots appeared in late summer 2006.
Humans, however, will be required for the foreseeable
future in repair and supervisory roles, particularly
in unstructured settings such as asteroid mines.
The evolution from small tourist stations of the
next decade to large space hotels will make economical
the use of fully closed life-support systems. These
could be considered the first space colonies. Derivatives
of these commercial space hotels may form suitable
Moon and asteroid mining habitats.
Using nonterrestrial materials is a key to opening
the space frontier. Dozens of rendezvous missions
to Near Earth Objects will be needed to assay their
resources and to plan rational NEO diversion. The
development of NEO mining techniques serves two purposes,
raw materials supply and planetary defense. We need
economical trajectories to and from these bodies.
These trajectories must not only be economical in
terms of delta V or time, but in dollars; and in the
time value of money, factors not generally considered
by the OMB.
Satellite solar power stations may be a $500 billion
per year market worldwide and cheap nickel steel from
asteroids may be an enabler of power satellite construction.
One asteroid of the right size and composition in
a suitable orbit could open this market. Platinum
group metals may be an important export, either as
a primary product, or as a byproduct of nickel steel
alloy production. Other products, derived from carbon,
may also be important. The first economical product
from an asteroid mine is likely to be water, for propellant
or life-support and radiation shielding in space hotels.
Keywords: Space Transportation, Asteroid Mining,
Solar Power Satellites, Space Settlement, Private
Space Travel, Space Hotels, Nonterrestrial Materials,
NEO, Composite Tanks, Rocket Engines. PACS: 00
I would like to argue that the human space enterprise
has three interrelated goals; the first is preservation
of the human race. Preservation means two things: first,
it means assured defense against catastrophic comet
and asteroid impacts. Defense against cosmic impacts
is something we must do in space, even if we do nothing
else. Second, preservation means expanding the ecological
range of humankind into the wider universe. Expansion
of ecological range will provide insurance against whatever
other extinction event may come our way. It makes no
difference whether it is thermonuclear war or natural
or artificial pestilence. With an ecological range extending
across the solar system, some humans will almost surely
survive any cataclysm. And thirdly, we would like to
use the energy and material resources of circumsolar
space to ensure prosperity on the Earth. We would not
only like to survive, we would like to thrive. The transmission
of space solar power to the Earth and the delivery of
essential metals to the terrestrial economy promise
to improve living standards globally, to mitigate global
warming, and to increase the sustainable carrying capacity
of our home planet.
There are two senses in which I would like to
use the word trajectory. The first trajectory
is that of a spaceship or probe traveling in space
governed by gravitation, light pressure, and engine
thrust. The second sense of trajectory is the
path of progress in time and space of a commercial
enterprise which would use the first trajectory
to best advantage. The second kind is governed
by the laws of supply and demand and return on
investment and technological capability and, not
least, fiduciary responsibility. To determine
whether the trajectories of the second kind will
be interesting at all, we must examine the reasons
for the present high cost of space transportation.
The prerequisite to achieving these goals is
cheap Earth to orbit transportation. We should
concentrate on an evolutionary, commercial path
to achieve that. The previous approaches, converting
ICBMs and expensive politically motivated projects
to win battles in the Cold War, have failed.
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"Part of the rim including many nearby space
vehicles" (large)
Don Davis - NASA
Space Colony Artwork
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The technical maturity of one or other kind of transportation,
historically, has been critical to the success of new
commercial enterprises. With the immature space transportation
of 2006, the trajectory of commercial enterprises other
than satellite communications and remote sensing, and
the occasional orbital tourist, will be a horizontal line.
The reason is straightforward, with transportation costing
thousands of dollars per kilogram to low Earth orbit,
solar power satellites, and asteroid mining and space
hotels cannot turn a profit. (1) Space settlement will
remain a dream.
It is a sad commentary, as well as an indictment of
government space programs, that a vehicle designed in
Russia more than 50 years ago provides the cheapest
manned flight to low Earth orbit.(2) It is as though
the WWI Sopwith Camel were the most advanced aircraft
flying in 1965. Unfortunately, the past half century's
stagnant Earth to orbit launch cost has convinced people
that high space launch costs are intractable and must
be a necessary result of the challenging physics of
the problem. This high cost is mistakenly viewed by
some as a necessary consequence of ascent to orbit using
chemical rockets.
For most booster designs, the flight rate is so low
that production economies of scale are imperceptible.
An empiric rule of thumb is a 15% reduction in unit
cost for every doubling of the number of units produced.
The absolute cost of space transportation has fallen
by only 30% over the past few decades. That number agrees
with the rule of thumb, and reflects a pitifully low
flight rate.
The High Cost Of Space Transportation
Is A Legacy Of Artillery Rockets
The argument is this: the present high Earth to orbit
launch cost is an artifact of using rocket artillery
in a transportation role. Transportation to low Earth
orbit is expensive because the rocket vehicles have
been expendable. It is plainly impossible to reduce
the cost of transportation below a few thousand dollars
per kilogram if the discarded launch vehicle costs that
much itself. During the Cold War, rocket engines and
structures were optimized to deliver the maximum warhead
mass with a single use. The lack of time during the
Cold War space race forced the conversion of intercontinental
ballistic missiles into manned space launchers.
Incremental Flight Test Saves Money
And Increases Reliability
It is more expensive to design a spaceship that cannot
be incrementally and repeatedly flight tested. Incremental
flight test saves design engineering hours. Aircraft
designers know that it is much cheaper to develop and
flight test a piloted vehicle with all altitude save-
the- vehicle capability than it is to build a series
of vehicles that must be tested to destruction, or ascend
flawlessly to orbit on first flight. (4) Compare the
six million dollar loss of the Falcon 1 twenty-eight
seconds into its maiden flight, because of a minor fuel
leak, to the uneventful landing of the piloted EZ Rocket
following a similar minor problem. Because test flight
opportunities are expensive and hence few, design flaws
may go undiscovered for years. The space shuttle's foam
shedding problem is a case in point.
A corollary is that infant mortality of traditional
launchers is high. Incremental flight testing prevents
early mortality from faulty construction. Every commercial
airliner is test flown to reveal manufacturing defects
so that those can be corrected before the airliner enters
passenger service. Expendable launchers cannot be test
flown before their single mission; therefore, manufacturing
defects must be inspected out. That strategy is expensive
and doesn't work particularly well.
Spaceships must be reliable to be cheap: if vehicles
are unreliable, the replacement costs and insurance
rates make them expensive. Ted Taylor pointed this out
four decades ago. (5) The idea of separating cargo and
people for safety's sake is nonsense; in the commercial
world, cheap transportation must be safe transportation.
The suborbital launch companies understand that the
inexpensive development and high reliability enabled
by incremental flight test are crucial to market success.
Design Requirements Of A Mature
Space Transportation System
The design requirements for a mature space transportation
system, in which each vehicle is to be used thousands
of times, are much different from those of missiles.
Rocket engine lifetimes until recently have been short,
partly by design. Engineering a long lifetime in a missile
really is undesirable since the increased weight needed
to yield a longer service life reduces the warhead mass.
And the rockets themselves are fragile for the same
reason. The more robust structure needed for reuse would
be uneconomical: they are throwaway articles designed
to deliver a warhead and be destroyed in the process.
Present day rockets could theoretically be reused, if
provision were made for recovery. (6) Their fragile
structure would limit their maximum service life to
tens of flights. Engineering a duty cycle of thousands
of flights, as opposed to the theoretical tens of which
present expendable rockets might be capable, exacts
a mass penalty of about 20%. The Saturn boosters, I
and V, were the first designed explicitly for reuse
and they were designed to be reused fewer than 50 times.
In that sense, they represent the pinnacle of reusable
rocket engineering up to now.
The Importance of New Rocket Technology
Rocket engines for cheap transportation must be designed
for thousands of flights. Rocket engineering has improved
dramatically in the past five years. XCOR has designed
and tested cheap, robust and reliable, high Isp rocket
engines capable of thousands of full duration burns.
The new engines have orders of magnitude better price
performance than Cold War legacy engines. XCOR has also
built a new composite LOX tank which is both stiffer
and stronger than previous designs and capable of thousands
of flights. The new composite LOX tanks weigh 65% as
much as the best previously available tanks. Since the
LOX tank is more than half the typical vehicle weight
excluding the engines, the large weight saving means
increased margin or increased payload. Adoption of this
LOX tank design may increase the payload by a factor
of as much as three. The new tank system is easily repairable,
has a very low thermal coefficient of expansion and
does not burn in high pressure oxygen.
The second major contributor to high space transportation
costs is the low flight rate, since both labor cost
and the capital cost of facilities must be amortized
over a small number of launches. (7) To achieve minimum
cost, we need robust reusable vehicles and a high flight
rate. Southwest Airlines makes money by keeping its
airliners' wheels in the wheel well. Contrast a 747
which flies 500 flights per year and has a ground crew
of twelve with the Space Shuttle which flies once a
year and has a ground crew of twelve thousand.
Mature transportation technologies such as airlines,
shipping lines or trucking companies have the peculiar
characteristic that the transportation price is within
a factor of three to five of the fuel cost. Design,
construction, operator's wages, amortization, depreciation,
profit and insurance comprise 60 to 80 % of the price.
The Zenit booster has a propellant cost of about ten
dollars per kilogram of payload orbited. The idea that
the rocket equation and implied cost of propellant prohibit
reducing launch costs is just false. A mature space
transportation system might be expected to have a cost
per kilogram to orbit of $100-160 since making the vehicles
more robust may increase the required propellant to
a quantity greater than today's most fuel efficient
launchers. That is a fraction of one per cent of space
shuttle costs and a just few per cent of the cheapest
launch available today. It would be useful to point
out that launch demand is predicted to become elastic
at a launch price of $1200 per kilo.
Private Space Transportation Provides
Market Pull
Fermi's Paradox: where are they? The skeptic may say,
"Well, if it is really possible, why hasn't the private
sector done it already?" The new technologies are wonderful
but not sufficient. A problem for companies planning
to build reusable space transportation is that the present
demand for space launch is only a few hundred tons per
year. The greater demand necessary to justify a fully
reusable launcher may not appear rapidly enough to amortize
the development cost, and yield the necessary return
on investment. It appears that the first vehicle will
have to be small, to allow the market to grow, and cheap
to develop and build, to give investors an adequate
ROI. The demand for space flights must increase by orders
of magnitude before the private capital markets will
finance expensive new spaceships. The new launch companies
understand this, too.
Of course, a capitalist has to believe that there
is a market for his product or service. Bankers have
a fiduciary responsibility to their investors to avoid
overly risky investments. Until Dennis Tito's flight
and the successful flights of SpaceShipOne, few people
believed there was a space tourism market. Luckily for
would be space settlers, dynamic American entrepreneurs
have increased the wealth of our society so that now
many people now are able to afford the projected price
of a suborbital flight. Market studies by the Futron
Corp. and others project a vigorous suborbital space
tourism market. With an assured market and high flight
rate, and free market competition, the heretofore glacial
progress in reducing the cost of space transportation
is likely to become rapid.
There will be destinations. Bigelow Aerospace is
testing its prototype orbital hotel that was launched
from Russia a few weeks ago. In many details, not the
least of which is cost, it promises a space habitat
much superior to the ISS. Mr. Bigelow has plans to deploy
a station composed of his modules on the Moon. Lockheed
Martin and Bigelow have undertaken a joint investigation
into the conversion of the Atlas V launcher for private
spaceflight.
The evolution from small tourist stations of the
next decade to large space hotels will necessitate the
incorporation of fully closed life-support systems.
According to a conservative analysis by the Boeing Corporation,
a largely closed life-support system for a low Earth
orbit space hotel should pay for itself within five
years. (8) The resupply mass per day per person is about
3 kg and the total mass of a closed environment life-support
system sized for one person is estimated to be 4 metric
tons. The closed systems have an advantage for low Earth
orbit locations since, in that location, they do not
require massive radiation shielding. Orbital locations
above the Van Allen belts will require massive radiation
shielding. In the case of an asteroid mission that shielding
may be obtained cheaply from the asteroid itself, and
of course, on the Moon the regolith can provide radiation
shielding that is very cheap indeed. The CELS systems
do require, however, some natural or artificial gravity
to separate gases from liquids, and to allow reliable
pumping of liquids from one subsystem to another.
Despite several decades of effort, including several
attempts at a completely closed system sized for people,
a simple, reliable, robust closed environment life-support
system has yet to be developed. Considerable effort
and expense has gone into the design of small systems
to grow plants in zero gravity. Effort has also been
expended on algal bioreactors to remove carbon dioxide,
unfortunately, algae is not an acceptable human food
stuff. NASA has made considerable effort to minimize
the area requirements for food plants. A serious disadvantage
of optimizing for minimum area is that very tight control
over the quantity and quality of nutrients delivered
to the plants is required.
Crop And Animal Waste Recycling
Is The Critical Problem
For Closed Systems Relatively little effort has been
expended on the key problem of converting crop waste
and animal wastes into nutrients suitable for growing
plants. SSI's investigators believe that a largely,
or even wholly biological, closed environment life-support
system will be the optimum choice. It is possible that
we would choose the Haber Bosch process for nitrogen
fixation and/or a backup supercritical water oxidation
unit to recycle refractory crop waste. Both require
high temperature and pressure and generate highly corrosive
chemicals. Those two physicochemical subsystems do offer
the possibility of decreasing required surface area
of the CELS system by about one third.
Prof. William Jewell, SSI's PI for CELSS has been
developing a system at Cornell that would avoid the
need for complicated monitoring systems tuned to precisely
control delivery of nutrient mixtures to plants. It
relies on robust biological systems, in the experience
of the Russians, much more reliable than their artificial
gear. The system would allow the recapture of much of
the chemical energy in the crop wastes. The methane
produced could be used as rocket fuel or as a chemical
feedstock. The waste management subsystems are useful
on Earth to recycle manure and crop wastes on farms
and to produce energy and byproducts. Prof. Jewell has
demonstrated, at a bench level, a digester capable of
returning 85% of the chemical energy in low-quality
hay as high-pressure methane. (9)
It appears obvious that nonterrestrial materials
are key to opening the space frontier.(10) The minimum
cheap rocket transportation cost to low Earth orbit
is an order of magnitude greater than the price of even
the most expensive raw materials in common use. The
Moon's resource potential has not been fully explored,
but, for the purposes of this conference we should also
think about the NEOs. In terms of delta V, some are
the easiest bodies to reach in the solar system. These
bodies taken together contain the full range of elements
and are, in some cases, highly differentiated. (11)
From the examination of meteorites, we have some working
knowledge of their compositions. Many have higher concentrations
of platinum group metals than the best terrestrial ores.
Many contain volatiles that are in short supply on the
Moon. There are at least 20 spectral types and close
rendezvous missions to a representative of each type
should be undertaken to assay their chemical and physical
properties. Physicochemical characterization of NEOs
will allow development of asteroid mining techniques.
The ability to mine NEOs is also implies the ability
to deflect them. The optimum method could be a gravity
tractor (12) with most of the mass of the tractor to
be obtained from the asteroid itself. Using mass drivers
for propulsion instead of ion engines would allow orders
of magnitude greater acceleration as well as much lower
total electrical energy requirement. Whether a private
enterprise could afford the insurance to swing one around
the Moon or persuade the U.N. that it would be safe
to return anything over 30 meters, is hard to say.
The new PanSTARRS telescope array in Hawaii, of which
the prototype saw first light in June, 2006 will increase
the detection rate of NEOs. Most will be main belt asteroids
but tens of thousands will be Earth crossers. Eventually,
one will be found on an Earth impact trajectory. We
need economical trajectories to and from these bodies.
The trajectories must not only the economical in terms
of delta V, but also eventually in dollars. NASA and
the OMB do not generally consider the time value of
money. If we are successful in our quest to expand the
ecological range of the human race, the time value of
money will be an additional factor in calculating trajectories.
In 1968, Peter Glaser proposed that solar power satellites
to beam energy from geostationary orbit to the Earth
could be a major economic boon from advanced space technology.
(13) Solar power from space is one of the few technologies
that appear to be able to produce the quantity of high-quality
electric power needed to bring a first world standard
of living to all inhabitants of our planet. To illustrate
the size of the potential market, the worldwide cost
to build electric power stations is projected to exceed
$500 billion annually for the next quarter century.
Former astronaut Dr. Philip Chapman calculates that
ground launched power satellites could be economical
at a price of $200 per kg. In 1974, Gerard K. O'Neill
proposed using the resources of the Moon to build solar
power satellites in geostationary orbit to supply energy
to the Earth. (14) According to his analysis, and confirmed
by subsequent work at the Space Studies Institute, the
capital cost of a system based on nonterrestrial resources
could be much lower than the capital cost of an Earth
launched power satellite system. One 80 meter nickel
steel asteroid would provide enough metal to construct
ten five gigawatt solar power satellites. Or a handful
of O'Neill Island One space colonies.
In summary, radically cheaper Earth to orbit transportation
is on the horizon. The near term economic driver is
private space travel; longer term drivers are likely
to be space solar power and asteroidal metals. CELSS
has a near term economic benefit and will enable long
duration operations far from Earth, including permanent
settlement. New technologies, many under commercial
development for terrestrial applications, and the invisible
hand of the free market will make things even cheaper.
So that the words of the poet, Alfred, Lord Tennyson:
"Men, my brothers, men the workers, ever reaping
something new:
That which they have done but earnest of the things
that they shall do:
For I dipt into the future, far as human eye could
see,
Saw the Vision of the world, and all the wonder that
would be;
Saw the heavens fill with commerce, argosies of magic
sails,
Pilots of the purple twilight dropping down with costly
bales;"
may soon represent more than dreams.
The author would like to acknowledge the insights of
Eric Anderson, Philip Chapman, Len Cormier, Samuel Dinkin,
Freeman Dyson, Peter Glaser, Jeff Greason, Klaus Heiss,
William Jewell, John S. Lewis, Ed Lu, John Mankins,
Hans Moravec, Rusty Schweikart, Henry Spencer, Gordon
Woodcock and Edward Wright.
1. Commercial Space Transportation Study, NASA Langley
May, 1994
2. Futron Corp., Space Transportation Costs: Trends
in Price per Pound to Orbit, 1990-2000 Sept. 6, 2002
3. General Public Space Travel and Tourism, Volume 2
Workshop Proceedings NASA CP 1999209146 Feb., 1999
4. " Reducing the Cost of Space Transportation" AAS
Science and Technology Series Vol. 21, 1969
5. T.Taylor, Propulsion of Space Vehicles in R.Marshak:
Perspectives in Modern Physics, New York 1966
6. Lockheed internal study9-2006 proposes reuse of Atlas
V booster as part of a study examining the feasibility
of an Atlas V tourist vehicle
7. B. Kutter, Commercial Launch Services: An Enabler
for Launch Vehicle Evolution and Cost Reduction, Lockheed
Martin Space Systems Company
8. E. Gustan and T. Vinopal, Regenerative Life Support/
Controlled Ecological Life Support System Contract NAS
2-11148, November, 1982 Boeing Aerospace Co.
9. Prof. Wm. Jewell, personal communication
10. K.E. Tsiolkowskii, "Dreams of Earth and Sky" 1895
11. J.S.Lewis and M.Matthews, "Resources of Near Earth
Space" Univ. of Arizona Press April, 1994
12. E.Lu and S. Love, Gravity tractor for Towing Asteroids,
Nature, vol. 438, 10 Nov, 2005
13. P.Glaser, Power from the Sun, Its Future, Science
vol.162, no. 3856, 1968 pp. 857-861
14. G.K.O'Neill, Space Colonization and Energy Supply
to the Earth, Science, vol. 190, no 4218, Dec 5,1975
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