Good news: Oncology (cancer), immunology, hematology, and "the common cold" turn out to be strongly interrelated subjects; research in all these is moving fast - and a real breakthrough in any one might mean a breakthrough in all.
10. 1950 By the end of this century mankind will have explored this solar system, and the first ship intended to reach the nearest star will be a building.
1965 Our editor suggested that I had been too optimistic on this one - but I still stand by it. It is still thirty - five years to the end of the century. For perspective; look back thirty - five years to 1930 - the American Rocket Society had not yet been founded. Another curve, similar to the one herewith in shape but derived entirely from speed of transportation, extrapolates to show faster - than - light travel by year 2000. I guess I'm chicken, for I am not predicting FTL ships by then, if ever. But the prediction still stands without hedging.
1980 My money is still on the table at twenty years and counting. Senator Proxmire can't live forever. In the last 101/2 years men have been to the Moon several times; much of the Solar system has been most thoroughly explored within the limits of "black box" technology and more will be visited before this year is out.
Ah, but not explored by men - and the distances are so great. Surely they are... by free - fall orbits, which is all that we have been using. But there are numerous proposals (and not all ours!) for constant - boost ships, proposals that require R&D on present art only - no breakthroughs.
Reach for your pocket calculator and figure how long it would take to make a trip to Mars and back if your ship could boost at one - tenth gee. We will omit some trivia by making it from parking orbit to parking orbit, use straight - line trajectories, and ignore the Sun's field - we'll be going uphill to Mars, downhill to Earth; what we lose on the roundabouts we win on the shys.
These casual assumptions would cause Dan Alderson, ballistician at Jet Propulsion Laboratory, to faint. But after he comes out of his faint he would agree that our answers would be of correct close order of magnitude - and all I'm trying to prove is that even a slight constant boost makes an enormous difference in touring the Solar System. (Late in the 21st century we'll offer the Economy Tour: Ten Planets in Ten Days.)
There are an unlimited number of distances between rather wide parameters for an Earth - Mars Earth trip but we will select one that is nearly minimum (it's cheating to wait in orbit at Mars for about a year in order take the shortest trip each way.. . and unthinkable to wait years for the closest approach). We'll do this Space Patrol style: There's Mars, here we are at L - 5; let's scoot over, swing around Mars, and come straight home. Just for drill.
Conditions: Earth - surface gravity (one "gee") is an acceleration of 32.2 feet per second squared, or 980.7 centimeters per second squared. Mars is in or near op position (Mars is rising as Sun is setting). We will assume that the round trip is 120,000,000 miles. If we were willing to wait for closest approach we could trim that to less than 70,000,000 miles .. . but we might have to wait as long as 17 years. So we'll take a common or garden variety opposition - one every 26 months - for which the distance to Mars is about 50 - to 60,000,000 miles and never over 64 million.
(With Mars in conjunction on the far side of the Sun, we could take the scenic route of over 500 million miles - how much over depends on how easily you sunburn. I suggest a minimum of 700 million miles.)
You now have all necessary data to figure the time it takes to travel Earth - Mars - Earth in a constant - boost ship - any constant - boost ship - when Mars is at opposition. (If you insist on the scenic route, you can't treat the trajectory approximations as straight lines and you can't treat space as flat but a bit uphill. You'll need Alderson or his equal and a big computer, not a pocket calculator; the equations are very hairy and sometimes shoot back.)
But us two space cadets are doing this by eyeballing it, using Tennessee windage, an aerospace almanac, a Mickey Mouse watch, and an SR - 50 Pop discarded years ago.
We need just one equation: Velocity equals acceleration times elapsed time: v = at
This tells us that our average speed is 1/2at - and from that we know that the distance achieved is the average speed times the elapsed time: d = 1/2at2
If you don't believe me, check any physics text, encyclopedia, or nineteen other sorts of reference books - and I did that derivation without cracking a book but now I'm going to stop and find out whether I've goofed - I've had years of practice in goofing. (Later - seems okay.)
Just two things to remember:
1) This is a 4 - pieces trip - boost to midpoint, flip over and boost to brake; then do the same thing coming home. Treat all four legs as being equal or 30,000,000 miles, so figure one of them and multiply by four (Dan, stop frowning; this is an approximation ... done with a Mickey Mouse watch.)
2) You must keep your units straight. If you start with centimeters, you are stuck with centimeters; if you start with feet, you are stuck with feet. So we have 1/4 of the trip equals 5280 x 30,000,000 = 1.584 x 1011 feet, or 4.827 x 1012 centimeters.
One last bit: Since it is elapsed time we are after, we will rearrange that equation (d = 1/2at2) so that you can get the answer in one operation on your trusty but - outdated pocket calculator... or even on a slide rule, as those four - significant - figures data are mere swank; I've used so many approximations and ignored so many minor variables that I'll be happy to get answers correct to two significant figures.
This gives us: t = Vd/1/2a
d is 30,000,000 miles expressed in feet, or 158,400,000,000. Set that into your pocket calculator. Divide it by one half of one tenth of gee, or 1.61. Push the square root button. Multiply by 4. You now have the elapsed time of the round trip expressed in seconds so divide by 3600 and you have it in hours, and divide that by 24 and you have it in days.
At this point you are supposed to be astonished and to start looking for the mistake. While you are looking, I'm going to slide out to the refrigerator.
There is no mistake. Work it again, this time in metric. Find a reference book and check the equation. You will find the answer elsewhere in this book but don't look for it yet; we'll try some other trips you may take by 2000 A.D. if you speak Japanese or German - or even English if Proxmire and his ilk fail of reelection.
Same trip, worked the same way, but at only one percent of gee. At that boost I would weigh less than my shoes weigh here in my study.
Hmmph! Looks as if one answer or the other must be wrong.
Bear with me. This time we'll work it at a full gee, the acceleration you experience lying in bed, asleep. (See Einstein's 1905 paper.)
(Preposterous. All three answers must be wrong.)
Please stick with me a little longer. Let's run all three problems for a round trip to Pluto - in 2006 A.D., give or take a year. Why 2006? Because today Pluto has ducked inside the orbit of Neptune and won't reach perihelion until 1989 - and I want it to be a bit farther away; I've got a rabbit stashed in the hat.
Pluto ducks outside again in 2003 and by 2006 it will be (give or take a few million miles) 31.6 A.U. from the Sun, figuring an A.U. at 92,900,000 miles or 14,950,000,000,000 centimeters as we'll work this both ways, MKS and English units. (All right, all right - 1.495 x 1013 centimeters; it gets dull here at this typewriter.)
Now work it all three ways, a round trip of 63.2 A.U. at a constant boost of one gravity, one tenth gravity, and one hundredth of a gee - and we'll dedicate this to Clyde Tombaugh, the only living man to discover a new planet - through months of tedious and painstaking examination of many thousands of films.
Some think that Pluto was once a satellite and its small size makes this possible. But it is not a satellite today. It is both far too big and hundreds of millions of miles out of position to be an asteroid. It can't be a comet. So it's a planet - or something so exotic as to be still more of a prize.