MMM Classics Year 10: MMM #s 91-100 - Moon Society

such an orbiting cryogenic fuel depot, using spent Shuttle
External Tanks, could be set up phase by phase. Most of the
liquid Hydrogen and liquid Oxygen needed would be “scavenged”
from residual amounts left in other ETs reaching orbit.
There are two logical orbital locations in either case
(tankers used serially, permanent filling stations): in the International
Space Station yards, and in low equatorial orbit.
The latter would be far more useful, being more reachable,
with less fuel, from most locations, and at maximum window
frequency. An equatorial filing station alone makes sense for
payloads bound for geosynchronous Clarke orbit or beyond, for
the Moon, Mars, or elsewhere in the ecliptic-hugging Solar
System. Building a refueling station in Alpha Town for vehicles
and payloads intended for deep space would be a lot like
putting a gateway for Europe-bound Americans in Patagonia.
Kick Motor “Tugs for Hire” - Orbitug Inc.
The idea of an orbital transfer tug, manned or not, has
been investigated for incorporation into Space Station operations.
But as we have just seen, given the Station’s intended
high inclination (51°) orbit, such a tug would be much more
useful in low equatorial orbit.
While the former might be agency operated, heaven
forbid, the later is a prime entrepreneurial commercial opportunity.
Tugs could be launch company owned and operated
(Lockheed Martin, McDonnell Douglas, Boeing North
American, Arianespace, Energiya, etc.), or time-share pool
operated, or perhaps leased by independent operators. Of the
major contractors, Arianespace, able to launch from a 6°N site
in French Guiana, has a big advantage.
Legislation to insure the commercial option may no
longer be needed but was proposed more than a decade ago in
the “Space Cabotage Act.” Cabotage means the “coastal” trade
in cargo, after John Cabot, the British explorer of the North
American Coast (c. 1497). “Coastal’ is appropriate as Earth’s
true “space coast” is not Brevard County, Florida but LEO to
GEO orbitspace.
Tug fees would of course reflect weight and delta v
required for the orbital transfer. But they would also reflect
whether the payload to be boosted was delivered to the tug
home base (filing station) or whether the tug had to go fetch it
in some other orbit first. Tug return to base fuel expenditures
would also have to be paid by the shipper. Now if these fees in
total are appreciably lower than the alternative cost of bringing
along a one-use throwaway pre-fueled kick motor, we have a
viable entrepreneurial space business opportunity.
Tug services would be “by appointment” and reservation
only, at least until traffic grew large enough to attract
speculative operators, able to “earn a living” through payloads
of opportunity.
Nor does the opportunity exist just for traditional
chemical rockets. Tether operated momentum boosters,
possibly solar powered, could easily carve out a number of
high traffic niches
Manned tugs would be useful for carrying replacement
parts to already orbiting satellites needing repair. If this
service can be profitably provided in a timely fashion at less
cost to the satellite owner than the procurement and launching
of a replacement satellite, we have another prime commercial
opportunity. Such a manned tug would be a natural comple-
ment to a commercially owned and operated station or industrial
park facility in equatorial orbit, serving as home “port”.
Refueling prices could come down once made on
Luna fuels are available in quantity and quality. We are talking
about lunar liquid oxygen, silane (SiH4, a methane analog and
hydrogen “extender”), and possibly powdered aluminum or
liquid hydrogen aluminum slurry fuels.
Each of these “enhanced CATS” scenarios wait on a
steady growth in traffic to become economically viable. For
low Earth orbit is only “halfway to anywhere in the Solar
System” [Robert A. Heinlein]. Orbital Filing Stations and Tugs
for Hire may be where we will find our CATS price-reducing
solutions in this theater of operations.
Earth to Moon & Earth/Moon to Mars
by Peter Kokh
Propulsion Questions
LANTR: (Liquid oxygen [LOX] Augmented Nuclear Thermal
Rocket) — In Moon Miners’ Review #18, JAN ‘96, Editor
Mark Kaehny reprinted an article by Dr. Stan Borowski of
NASA-Lewis, about a very promising new propulsion
concept which could cut Earth-Moon transit time down to a
day, and delivery more cargo to boot.
If total transit time is drastically cut, then the mass of
shipboard facilities needed to keep passengers amused and
content should be less. Less ship mass per capita [per fare]
means less fuel needed per fare, or cheaper passage.
NIMF: (Nuclear rocket using Indigenous Martian Fuel)
In Moon Miners’ Manifesto # 30 NOV ‘89, we reported on
Dr. Robert Zubrin’s concept for manufacturing both getaround
Mars exploration fuel and return-home fuel from
Mars’ atmosphere, instead of bringing it along from Earth.
This scenario would cut drastically the size and mass of a
ship or expedition needed to put a given crew and amount of
equipment on Mars.
AEROBRAKE: a ship configuration that can present a
large cross-section to the atmosphere upon entry or grazing,
allowing it to dump momentum without firing retrorockets.
Ships returning to Earth or Earth orbit from the Moon or
Mars, and ships headed for Mars or Mars orbit can benefit
from aerobraking. But this is an economic plus only if any
extra mass needed to provide an aerobraking profile is less
than the mass of fuel that would be burned in firing
retrorockets. Thus it is a nice idea that presents design
challenges.
Dividing & Conquering “Delta-V”:
Shuttle-Ferry-Shuttle Rendezvous
At first blush, Moon Direct and Mars Direct - the idea
of transferless passage from one planetary surface all the way
to another - is as mentally comfortable to those of us breast-fed
Moon Miners’ Manifesto Classics - Year 10 - Republished January 2006 - Page 86