Expanded Universe

AFTERWORD

Santa Claus, Arizona, is still there; just drive from Kingman toward Boulder Dam on 93; you'll find it. But Mrs. Santa Claus (Mrs. Douglas) is no longer there, and her gourmet restaurant is now a fast - food joint. If she is alive, she is at least in her eighties. I don't want to find out. In her own field she was an artist equal to Rembrandt, Michelangelo, and Shakespeare. I prefer to think of her in that perfect place where all perfect things go, sitting in her kitchen surrounded by her gnomes, preparing her hearty ambrosia for Mark Twain and Homer and Praxiteles and others of her equals.

THE ANSWERS

(to Problems on Pages 334 - 338)

N.B.: All trips are Earth parking orbit to Earth parking orbit without stopping at the target planet (Mars or Pluto). I assume that Hot Pilot Tom Corbett will handle his gravity - well maneuvers at Mars and at Pluto so as not to waste mass - energy - but that's his problem. Now about that assumption of "flat space" only slightly uphill: The Sun has a fantastically deep gravity well; its "surface" gravity is 28 times as great as ours and its escape speed is 55 + times as great - but at the distance of Earth's orbit that grasp has attenuated to about one thousandth of a gee, and at Pluto at 31.6 A.U. it has dropped off to a gnat's whisker, one millionth of gee.

(No wonder it takes 21/2 centuries to swing around the Sun. By the way, some astronomers seem positively gleeful that today Pluto is not the planet farthest from the Sun. The facts: Pluto spends nine - tenths of its time outside Neptune's orbit, and it averages being 875,000,000 miles farther out than Neptune - and at maximum is nearly 2 billion miles beyond Neptune's orbit (1.79 x 10 miles) - friends, that's more than the

ROUND TRIP BOOST

COMPARISON OF ELAPSED TIME

Earth - Mars - Earth - Earth - Pluto - Earth

@1 gee

4.59 days vs. 4.59 weeks

@ 10 gee

14.5 days vs. 14.5 weeks

@ 100 gee

45.9 days vs. 45.9 weeks

@ 1/1000 gee

145 days vs. 145 weeks

distance from here to Uranus, nearly four times as far as from here to Jupiter. When Pluto is out there - l 865 or 2114 A.D. - it takes light 6 hours and 50 minutes to reach it. Pluto - the Winnuh and still Champeen! Sour grapes is just as common among astronomers as it is in school yards.)

- and the rabbit is out of the hat. You will have noticed that the elapsed - time figures are exactly the same in both columns, but in days for Mars, weeks for Pluto - i.e., with constant - boost ships of any sort Pluto is only 7 times as far away for these conditions as is Mars even though in miles Pluto is about 50 times as far away.

If you placed Pluto at its aphelion (stay alive another century and a quarter - quite possible), at one gee the Pluto round trip would take 5.72 weeks, at 1/to gee 18.1 weeks, at 1/too gee 57.2 weeks - and at 'Iiooo gee 181 weeks, or 3 yrs & 25 wks.

I have added on the two illustrations at 'Iwoo of one gravity boost because today (late 1979 as I write) we do not as yet know how to build constant - boost ships for long trips at 1 gee, 1/10 gee, or even 1/too gee; Newton's Third Law of Motion (from which may be derived all the laws of rocketry) has us (temporarily) stumped. But only temporarily. There is E = mc2, too, and there are several possible ways of "living off the country" like a foraging army for necessary reaction mass. Be patient; this is all very new. Most of you who read this will live to see constant - boost ships of 1/10 gee or better - and will be able to afford vacations in space - soon, soon! I probably won't live to see it, but you will. (No complaints, Sergeant - I was born in the horse & buggy age; I have lived to see men walk on the Moon and to see live pictures from the soil of Mars. I've had my share!)

But if you are willing to settle today for a constant boost on the close order of magnitude of 1/1000 gee, we can start the project later this afternoon, as there are several known ways of building constant - boost jobs with that tiny acceleration - even light - sail ships.

I prefer to talk about light - sail ships (or, rather, ships that sail in the "Solar wind") because those last illustrations I added (l/t000 gee) show that we have the entire Solar System available to us right now; it is not necessary to wait for the year 2000 and new breakthroughs.

Ten weeks to Mars ... a round trip to Pluto at 31.6 A.U. in 2 years and 9 months... or a round trip to Pluto's aphelion, the most remote spot we know of in the Solar System (other than the winter home of the comets).

Ten weeks - it took the Pilgrims in the Mayflower nine weeks and three days to cross the Atlantic.

Two years and nine months - that was a normal commercial voyage for a China clipper sailing out of Boston in the last century ... and the canny Yankee merchants got rich on it.

Three years and twenty - five weeks is excessive for the China trade in the 19th century.. . but no one will ever take that long trip to Pluto because Pluto does not reach aphelion until 2113 and by then we'll have ships that can get out there (constant boost with turnover near midpoint) in three weeks.

Please note that England, Holland, Spain, and Portugal all created worldwide empires with ships that took as long to get anywhere and back as would a Vtooo - gee spaceship. On the high seas or in space it is

not distance that counts but time. The magnificent accomplishments of our astronauts up to now were made in free fall and are therefore analogous to floating down the Mississippi on a raft. But even the tiniest constant boost turns sailing the Solar System into a money - making commercial venture.

Now return to page 338.

"Tomorrow we again embark

upon the boundless sea."

- Horace, Odes