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

y Peter Kokh
I remember Tom Rogers’ audience gripping pep talk
at the banquet at the 1988 International Space Development
Conference in Denver. He foresaw a day when people -
workers, tourists, and settlers - would be the principal item
shipped to space. Indeed, people are the one thing it makes
sense to ship to space rather than produce there from on site
resources. It will be this traffic that opens space. And until this
traffic begins in earnest, probably with tourists, space will
largely be a venue for a token scouting elite, and for Earthbound
armchair voyeur wannabes - like us.
If this proves true, Cheap Access to Space (“CATS”)
solutions developed for large hardware items like space station
modules and communications satellites may very well not
prove optimal for the coming traffic in live-and-wanting-tostay-that-way
bodies. The Space Shuttle was early-on likened
to an all-purpose “pickup truck” for space. That doesn’t make
it qualify as a good bus or highway coach, much less a good
family car. The shuttle and its paper study replacements are in
fact crewed cargo ships, cargo ships that can take along a small
hardy and hardened crew.
While hardware payloads may come in a set range of
sizes, occasional oversized loads being low traffic items, the
optimum size for a people shuttle will change as the sustained
demand and volume of traffic grows. The 29 passenger DC-3
once did just fine. But today, it is often more economical to fly
planes that carry several hundreds at once. The point is that a
CATS solution not amenable to “scaling up” may be an
unhappy choice as a people carrier, even if it does deliver
airline style operation and fast turnaround time.
Shuttle time to orbital destinations is short, shorter
even than the average domestic airlines hop - not counting the
time you may have to sit on the pad prior to taking off! Given
the expected shortness of surface to orbit flights, a high
“packing” density in the cabin may be tolerable. Demand for a
“window seat” may well be higher than that aboard airliners,
given that the scenery will be much less prosaic. That “see one
cloud, see them all; see one farmer’s field, see them all” attitude
will not be common, even for seasoned shuttle travelers.
This demand, if carriers choose to meet it, may place constraints
on cabin design, and may make some SSTO configurations
much more popular than others. Right now, in the early
stages of CATS R&D, such considerations are at the bottom of
the list. But in time, that list will be turned end for end.
Competing SSTO configurations may favor competing
ground-based infrastructure (spaceport launch and land
facilities). In the early days of space tourism, low traffic
volume will bring with it few choices of gateways. If you want
to go, you will not complain about flying to a distant departure
field. But as traffic grows, at first chartered but eventually
scheduled, it will be economical to offer more gateways,
departure points convenient to more population centers or
perhaps at more major airline connection hubs. If that is the
case, SSTO configura-tions that are the less versatile and place
higher and more expensive to meet constraints on spaceport
infrastructure will lose out in competition (all else being equal)
to those that can take off from nearly anywhere and land nearly
anywhere.
The general public will want lower accelerations than
seasoned crews can tolerate. This will be another major design
consideration not currently given much weight. Compromises
are inevitable, however. It could be for example, that the only
way to bring the ticket price down to a mass-use threshold may
be the use of an Earth-bound first stage such as a mag-lev sled
at a high altitude, and preferably low latitude (near equatorial)
“aerospaceport” and there will be few of these if indeed more
than one. Such a development will move orbit-bound traffic in
patterns opposite to the decentralized paradigm suggested
above. The use of piloted piggyback flyback boosters would
also tend to limit gateway choices.
When it comes to moving regular people traffic
between Earth and Lunar orbits, and between lunar orbit and
the lunar surface, still other vehicle configurations may prove
to be the most economical. Thus, even though the McDonnell
Douglas Delta Clipper family configuration is inherently more
versatile when it comes to landing site, not even requiring an
atmosphere, that doesn’t mean that just because it can land and
take of from the Moon (or anywhere else) that it is the most
economical configuration in that specialized environment.
Certainly for Earth-Moon ferry traffic, where we are
concerned with flight times of many hours to a few days, cubic
foot allowance per person will have to be much more generous,
with diversions galore.
And when it comes to Mars, the usual “space shuttle”
pattern will be set on its ear. Instead of a surface-based vehicle
that can get to orbit and then return, we will need, at first at
least, an orbit-based vehicle that can land anywhere (look, ma,
no runaways) and get back to orbit. Who can say, (let’s agree
to have fun here) perhaps for that purpose a saucer-shaped
vehicle may do better than a winged one. After all, it is the
orbit-based “surface shuttle” paradigm that UFO lore invokes.
So while we are supporting CATS, let’s be aware that
the early answers may not prove to be the best answers - we
need to explore all the options if we want not just to open space
to more hardware, but also to more - quantum leaps more -
people.
by Peter Kokh
In the last article, we suggested that it is conceivable
that the least expensive per capita seat to orbit may be a vehicle
that is booster- or track-launched from a high altitude near
equatorial aerospaceport. Let’s play with that idea for a
moment - not with the launch track or other captive booster
stage options- but with candidate sites.
If we look at existing international airports, making
the problematic assumption that our transatmospheric spaceplane
can take off and land within the typical boundaries of
Moon Miners’ Manifesto Classics - Year 10 - Republished January 2006 - Page 83