SSTO's would have made possible Arthur C. Clarke's vision of 2001.

                                                      Copyright 2012 Robert Clark

Space Travel: The Path to Human Immortality?
Space exploration might just be the key to human beings surviving mass
genocide, ecocide or omnicide.
July 24, 2009
On December 31st, 1999, National Public Radio interviewed the futurist and science fiction 
genius Arthur C. Clarke. Since the author had forecast so many of the 20th Century's most 
fundamental developments, the NPR correspondent asked Clarke if anything had happened 
in the preceding 100 years that he never could have anticipated. 'Yes, absolutely,' Clarke 
replied, without a moment's hesitation. 'The one thing I never would have expected is that, 
after centuries of wonder and imagination and aspiration, we would have gone to the moon ... 
and then stopped.'
http://www.alternet.org/news/141518/space_travel:_the_path_to_human_immortality/

  I remember thinking when I first saw 2001 as a teenager and could 
appreciate it more, I thought it was way too optimistic. We could
never have huge rotating space stations and passenger flights to orbit
and Moon bases and nuclear-powered interplanetary ships by then.

 That's what I thought and probably most people familiar with the space
program thought that. And I think I recall Clarke saying once that the
year 2001 was selected as more a rhetorical, artistic flourish rather
than being a prediction, 2001 being the year of the turn of the
millennium (no, it was NOT in the year 2000.)

 However, I've now come to the conclusion those could indeed have been 
possible by 2001. I don't mean the alien monolith or the intelligent computer, 
but the spaceflights shown in the film.

 It all comes down to SSTO's. As I argued previously [1] these could
have led and WILL lead to the price to orbit coming down to the $100
per kilo range. The required lightweight stages existed since the 60's
and 70's for kerosene with the Atlas and Delta stages, and for
hydrogen with the Saturn V upper stages. And the high efficiency
engines from sea level to vacuum have existed since the 70's with the
NK-33 for kerosene, and with the SSME for hydrogen.

 The kerosene SSTO's could be smaller and cheaper and would make
possible small orbital craft in the price range of business jets, at a
few tens of millions of dollars. These would be able to carry a few
number of passengers/crew, say of the size of the Dragon capsule. But
in analogy with history of aircraft these would soon be followed by
large passenger craft.

 However, the NK-33 was of Russian design, while the required
lightweight stages were of American design. But the 70's was the time
of detente, with the Apollo-Soyuz mission. With both sides realizing
that collaboration would lead to routine passenger spaceflight, it is
conceivable that they could have come together to make possible
commercial spaceflight.

 There is also the fact that for the hydrogen fueled SSTO's, the
Americans had both the required lightweight stages and high efficiency
engines, though these SSTO's would have been larger and more
expensive. So it would have been advantageous for the Russians to
share their engine if the American's shared their lightweight stages.
 For the space station, many have soured on the idea because of the ISS 
with the huge cost overruns. But Bigelow is planning on "space hotels"
derived from NASA's Transhab[2] concept. These provide large living
space at lightweight. At $100 per kilo launch costs we could form
large space stations from the Transhabs linked together in modular
fashion, financed purely from the tourism interests. Remember the low
price to orbit allows many average citizens to pay for the cost to LEO.

 The Transhab was developed in the late 90's so it might be
questionable that the space station could be built from them by 2001.
But remember in the film the space station was in the process of being
built. Also, with large numbers of passengers traveling to space it
seems likely that inflatable modules would have been thought of
earlier to house the large number of tourists who might want a longer
stay.

 For the extensive Moon base, judging from the Apollo missions it might
be thought any flight to the Moon would be hugely expensive. However,
Robert Heinlein once said: once you get to LEO you're half way to
anywhere in the Solar System. This is due to the delta-V requirements
for getting out of the Earth's gravitational well compared to reaching
escape velocity.

 It is important to note then SSTO's have the capability once refueled
in orbit to travel to the Moon, land, and return to Earth on that one
fuel load. Because of this there would be a large market for passenger
service to the Moon as well. So there would be a commercial
justification for Bigelow's Transhab motels to also be transported to
the Moon [3].

 Initially the propellant for the fuel depots would have to be lofted
from Earth. But we recently found there was water in the permanently
shadowed craters on the Moon [4]. Use of this for propellant would
reduce the cost to make the flights from LEO to the Moon since the
delta-V needed to bring the propellant to LEO from the lunar surface
is so much less than that needed to bring it from the Earth's surface
to LEO.

 This lunar derived propellant could also be placed in depots in lunar
orbit and at the Lagrange points. This would make easier flights to
the asteroids and the planets. The flights to the asteroids would be
especially important for commercial purposes because it is estimated
even a small sized asteroid could have trillions of dollars worth of
valuable minerals [5]. The availability of such resources would make
it financially profitable to develop large bases on the Moon for the
sake of the propellant.

 Another possible resource was recently discovered on the Moon: uranium
[6]. Though further analysis showed the surface abundance to be much
less than in Earth mines, it may be that there are localized
concentrations just as there are on Earth. Indeed this appears to be
the case with some heavy metals such as silver and possibly gold that
appear to be concentrated in some polar craters on the Moon [7].

 So even if the uranium is not as abundant as in Earth mines, it may be
sufficient to be used for nuclear-powered spacecraft. Then we wouldn't
have the problem of large amounts of nuclear material being lofted on
rockets on Earth. The physics and engineering of  nuclear powered
rockets have been understood since the 60's [8]. The main impediment
has been the opposition to launching large amounts of radioactive
material from Earth into orbit above Earth. Then we very well could
have had nuclear-powered spacecraft launching from the Moon for
interplanetary missions, especially when you consider the financial
incentive provided by minerals in the asteroids of the asteroid belt.


    Bob Clark





REFERENCES
1.)The Coming SSTO's.
http://exoscientist.blogspot.com/2012/05/coming-sstos.html

2.)TransHab.
http://en.wikipedia.org/wiki/TransHab

3.)Private Moon Bases a Hot Idea for Space Pioneer.
by Leonard David, SPACE.com's Space Insider Columnist
Date: 14 April 2010 Time: 02:23 PM ET
http://www.space.com/8217-private-moon-bases-hot-idea-space-pioneer.html

4.)Mining the Moon's Water: Q & A with Shackleton Energy's Bill Stone.
by Mike Wall, SPACE.com Senior WriterDate: 13 January 2011 Time: 03:57 PM ET
http://www.space.com/10619-mining-moon-water-bill-stone-110114.html

5.)Riches in the Sky: The Promise of Asteroid Mining.
Mark Whittington, Nov 15, 2005
http://www.associatedcontent.com/article/11560/riches_in_the_sky_the_promise_of_asteroid_pg2.html?cat=58

6.)Uranium could be mined on the Moon.
Uranium could one day be mined on the Moon after a Japanese spacecraft
discovered the element on its surface.
By Julian Ryall in Tokyo 4:58PM BST 01 Jul 2009
http://www.telegraph.co.uk/science/space/5711129/Uranium-could-be-mined-on-the-Moon.html

7.)Silver, Gold, Mercury and Water Found in Moon Crater Soil by LCROSS Project.
Catherine Dagger, Oct 22, 2010
http://www.associatedcontent.com/article/5922906/silver_gold_mercury_and_water_found_pg2.html?cat=15

8.)NERVA.
http://en.wikipedia.org/wiki/NERVA