THE DEAN DRIVE and other Reactionless Drives

Monday, September 14, 2009

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Years ago I worked for an aerospace company and for a while was involved with efforts to buy a very odd device called the Dean drive. The story is worth preserving.

The Dean Drive


Testing candidate spacedrives

Ion Drives

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Created in 1990. Last revision 2009.



This letter started it: I began to make a reply and ended up writing a short report.


You may be way ahead of me on this one.

Did you notice rec.arts.sf.written is citing you a lot in a current thread on the Dean Drive. Ion Drive may actually work.

Clark E. Myers
e-mail at:
I wouldn't Spam filter you!

I don't read newsgroups and such. No time. I don't know what they're saying about me. Anyone want to find out and tell me?



Back in the 1950's John W. Campbell, Jr., editor of Astounding Science Fiction (which later became Analog Science Fact/Fiction then Analog Science Fiction; I forget just when the name change came) said he had seen a reactionless drive. That is: a gadget that would produce linear acceleration (make something move in a straight line) without interacting with any medium (like air or water) and without losing mass (which is what a rocket does: a rocket throws mass overboard, producing acceleration in the opposite direction. This is described in the rocket equation, which you can read about over in the space papers section of this web site). This is important because rockets have to throw away a LOT of mass (up to 90% of the total craft mass) to get any speed you'd be interested in. Again see my SSTO papers, or consult Willy Ley's books.

In particular, Campbell said he had seen this thing sit on a bathroom scale; it weighed, say, nine pounds when it was at rest. When it was turned on -- by plugging in an ordinary quarter-inch electric drill that was incorporated into the gadget -- gears turned, weights whirled, and the scale indicated a weight of perhaps 8.5 pounds! This is an impressive thrust; if you could apply continuously that much thrust (1/18 g!) in free fall you would be able to colonize the solar system. The Dean Drive would be the key to space travel even if it never produced enough thrust to actually lift itself.

I was then working for a large aerospace company in the Northwest. I didn't think this thing would work, but suppose it did? It would be wonderful. I worked for a retired general, and I convinced him that although the probability of this working was low, the payoff was high, and we ought to try getting it. I was headed to Washington on another trip anyway, so it wouldn't cost much to look. Campbell, though more enthusiast than scientist, was no fool, and was certainly aware of many fraudulent attempts to build a reactionless drive. He may have been fooled this time, or, as he had put forth in a story he had one of his stalwarts write, he may have believed that if the scientists thought such a drive were possible, then they might build one. They wouldn't even try if they thought it impossible.

I never saw the Dean Drive. Harry Stine saw it once. I had a letter of credit which, if countersigned by another company scientist (who was also going East then) and a management type (resident in the DC area), was worth half a million; I was to use that to buy the Dean Drive if we were convinced it actually worked.


We made contact with Dean. Dean wouldn't show us the thing until we gave him the money. We weren't about to hand over the money until we knew it worked. A former Peenemunde rocket scientist associate of mine (this was all in the 1950's) said that some charlatan had built a gadget that sounded a lot like this thing in that it would climb a string and rock like a pendulum, but it was in fact taking advantage of Newton's 3rd law (for every action there is an equal and opposite reaction), not overcoming it. Hitler had been impressed and ordered an investigation, but nothing came of it. Alas, my German associate never saw the Dean Drive. In fact, the late Harry Stine is one of the only two people I ever met who HAD seen it, the other being the late John W. Campbell, Jr.

Why an airplane company would be interested in a weird thing like that ought to be clear. If it worked at all, if it could produce even a tiny amount of linear acceleration from rotary acceleration (that's what it claimed it could do) then space travel isn't at the mercy of the rocket equation, and you won't have to throw most of the ship away to go anywhere.

Dean may or may not have been sincere, but he was certainly hard to deal with. He was so afraid -- or purported to be afraid -- that his gadget would be stolen that he wanted lots of money up front before he'd show it to us. Why he showed it to John and Harry I don't know; it was from their report that I concluded it was worth going back East and trying to buy the thing, and I convinced the General that we ought to put up the money. They decided to make it in a letter of credit valid if signed by me, the other science type, and a finance troop who was instructed to sign if both of us did. We went east, and I now know -- didn't then -- that 3M had sent a team with almost the exact same instructions to try to buy it if they thought it would work.

It may be that Dean thought that with at least two potential buyers (there's some evidence of a third but I don't know who it was) he could play tight and up the price. Perhaps he could have -- I'd have recommended far more than half a million if it worked -- but he wasn't going to get any takers until he showed the darn thing, and he wouldn't DO that. Oh. He also wanted a promise of a Nobel Prize. In my case I was perfectly willing to promise it. Of course I had no idea how I'd go about getting it for him, but I suspected that if he really could overcome Newton's third he'd have no trouble on that account.

Anyway, nothing came of it all. If it worked I never saw it work, and neither did the 3M team. The original device as described by Campbell and Stine was never found after Dean died, and the thing described in the patent doesn't work and isn't, according to Stine, what Dean showed as a working device.

My own conclusion is that the thing didn't work. It would sit on a scale and vibrate enough that it appeared to lose weight, but that has to do with pendular motion and resonance with the scale springs. The same kind of thing will climb a string. It seems to lose weight, but it doesn't. I think Dean built the same gidget that excited Hitler, although I doubt that Dean ever knew of the earlier device.

Harry Stine was convinced that he had seen a reactionless drive, and that one could be built. He was so convinced of that that I got a small grant from the Vaughn Foundation (about 3 grand as I recall) to pay the travel expenses of Possony, Harry Stine, Bob Forward, and some other people to meet to discuss what, if anything, ought to be done just in case this worked. Our conclusion was that nothing could be done: none of us knew how to build it, the gadget was lost, and we had only Harry's impression (he made no actual tests other than observation) that it had ever worked. There wasn't anything we COULD do, and the probabilities were very low that there was anything worth doing. Harry, for the record, disagreed, but he didn't have any suggestions on what to do beyond keeping an open mind. He died convinced that the Dean Drive worked.

Every now and then people come up with ways to move weights around in a non-circular path, usually several weights out of phase with each other, and get excited because there is an apparent weight loss. In every case it turns out to be an artifact of the system for measuring the weight. Others put the thing in water, and it appears to move and thus they think since there is no water coming in or out and no oars, it must be producing acceleration. It's not, of course: it's the same effect as bobbing a bobsled, taking advantage of different accelerations of the weights in different directions interacting with friction and resonating with the medium. After all, water has inertia too.

The conclusion of our brief conference on the Dean Drive was given by the late Robert Forward: Theories are fine, but what's needed is a demonstration. A repeatable demonstration: a new data point. Until we have that, it's all speculation.


If anyone does have a candidate device for producing reactionless acceleration -- that is, linear acceleration without throwing mass overboard and without reacting with a medium such as air or water -- the first test is to suspend it on two wires attached so that the plane of the two wires is normal to the direction of thrust-- that is, make a swing and put your gadget on it facing in the normal direction of travel of the swing. Now turn it on. If it will hang non-vertically, get interested. Now cover it with a plastic garbage bag and see if it will still hang non-vertically. If it will still do so, turn it off, and if it settles to a vertical angle, and you can do this repeatedly, and it hasn't lost any mass during the experiments, call your local physics professor. Or call me. I'll take care of notifying the Swedish Academy. But until it will do that, I don't need to look at it…


Ion drives work. Bob Forward showed me one at Hughes some years ago, and I recently met the Hughes Research scientist who was in charge of that project. I used a form of ion drive in my story "Tinker" which is in the (probably out of print) collection "High Justice." And is now incorporated in EXILE -- AND GLORY!!

Alas, real ion drives have nothing to do with the magical "ion drives" of early Star Trek episodes. A real ion drive produces very low thrust but it does it extremely efficiently, with ISP of up to 20,000 or so. ISP is "specific impulse" and is a pure number derived from calculating pounds of thrust per pound of fuel per second. If you make that calculation all the units cancel out. The best chemical rockets have ISP of about 400. See the SSX papers for more detail.

Anyway, thanks for reminding me of all this. Time I put the story on this web site.



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