In Friday, Heinlein describes a device called a Shipstone, which is essentially a non-rechargeable battery with extremely high energy density. They are manufactured by some proprietary process, which is relevant to the plot, but the book does not give details on what principle the devices are based.

Do these things show up in other works of his, or has he given interviews where he explains them?


2 Answers 2


I can find only brief mentions in the two novels that followed Friday and Job, The Cat Who Walks Through Walls pub. 1985 and To Sail Beyond the Sunset pub 1987. (There is no mention of Shipstones in Job).

For completeness I've listed these below, but they are throwaway mentions that add nothing to the description in Friday. I would guess Heinlein felt he had sufficiently established Shipstones as part of his universe so they needed no further description in subsequent novels.

The closest we get in Friday is:

In studying the Shipstone corporate complex I did not attempt to study Shipstones. The way — the only way — to study Shipstones would be to go back to school, get a Ph.D. in physics, — add on some intense postdoctoral study in both solid state and plasma, get a job with one of the Shipstone companies and so impress them with your loyalty and your brilliance that you are at long last part of the inner circle controlling fabrication and quality.

So they involve plasma physics as well as solid state physics.

The Cat Who Walks Through Walls

Chapter 15:

No magic is involved. An electric catapult is a motor generator. Never mind that it doesn't look like one. In its acceleration phase it is a motor; electric power is converted into kinetic energy. In its decelerating phase it is a generator; the kinetic energy extracted from the capsule is pulled out as electric power and stored in a Shipstone. Then the same energy is taken from the Shipstone to hurt the capsule back to Kong.

Not quite. There are hysteresis losses and other inefficiencies. Entropy always increases; the second law of thermodynamics can't be snubbed. What it most resembles is regenerative braking. There was a time, years ago, when surface cars were slowed and stopped by friction, rudely applied. Then a bright lad realized that a turning wheel could be stopped by treating it as a generator and making it pay for the privilege of being stopped-the angular momentum could be extracted and stored in a "storage battery" (an early predecessor of Shipstones).

Chapter 27:

Starting about 2150 or a little earlier (I saw my first one the year I signed up) supreme swank for an Iowa fanner was to own and drive a working replica of a twentieth-century "automobile" personal transport vehicle. Of course not a vehicle moved by means of internal explosions of a derivative of rock oil: Even the People's Republic of South Africa had laws against placing poisons in the air. But with its Shipstone concealed and a sound tape to supply the noise of a soi-disant "1C' engine, the difference between a working replica and a real "automobile" was not readily apparent.

To Sail Beyond The Sunset

Chapter 20:

"I'm not sure. We were all the way to Olathe before we found a filling-station that also serviced Shipstones. While Hank was trading his stone for a fully charged one, I opened Polly's cage to change her sandbox - she had made a mess and the dragonwagon was stinking."

Chapter 21

"As a starter, try multiplying a thousand miles by two hundred yards, to get square yards, then call it horsepower. Use a ten per cent efficiency factor. Save the surplus power in Shipstones when the Sun is high and bright; use that surplus to keep the roads rolling when the Sun doesn't shine." (I could be glib about it; I had done the arithmetic many times in thirty-four years.)

  • Regenerative braking... every so often, I'm reminded how often Heinlein predicted future technology that they just couldn't execute yet.
    – FuzzyBoots
    Commented Jan 27, 2023 at 17:03
  • 3
    Regenerative braking was quite common on electrified railways of all sizes from the very beginning.
    – Jon Custer
    Commented Jan 27, 2023 at 17:08
  • That is interesting that in The Cat who Walks Through Walls, it is described as being rechargeable. In Friday, I thought part of why the Shipstone corporation was able to maintain its monopoly was that people had to keep buying them. (I may be misremembering)
    – egeorge
    Commented Jan 27, 2023 at 17:31
  • @egeorge I had a look through Friday and while I couldn't find any mention of charging Shipstones I also couldn't find anything to say they couldn't be recharged. Commented Jan 27, 2023 at 17:57
  • They do mention 'inserting the' -- before Daniel is interrupted/shushed. But, then, that's from "from the muckraking history and from other independent sources as I just don't believe the sweetness and light of the company version", and described as "Fictionalized speech attributed to Muriel Shipstone", so may have nothing to do with the actual process.
    – K-H-W
    Commented Jan 27, 2023 at 21:25

A significant point in your question is the assertion that shipstones are “non-rechargeable” batteries. The statements about life-long tiny shipstone batteries mentioned in his stories is easily provable using Ohm’s law. If the device requires say 50 mA, to allow for a safety margin assume 24/7 of the 50mA and say 5VDC output for 200 years. How many AH would the battery need to hold? I’ll let you do the math - assuming these numbers, the device would need to run 4000 hours to equal one KW-Hour.

My point is, a battery can be “life-long” but the same technology can be re-chargeable. My question would be - this afer a lifetime of reading everything he published multiple times - are these assumptions true about Shipstones:

  1. A “density” orders of magnitude higher than any current tech
  2. Once manufactured, these were impervious to any reverse engineering
  3. The specific mechanical lifespan I don’t recall. With current tech requiring many charge cycles, obviously the Shipstones endured far fewer cycles.

I would refer you to TEFL and read the chapter “Tale Of The Adopted Daughter.” Lazarus had some size of portable ShipStone while settling a wilderness area on a still young planet. He was using some kind of hand cranked generator to recharge it, having packed minimal parts for a windmill but lacked raw materials to build it at first. Dora heard him spout off something like “if I only had 5HP of power” and she, not familiar with the expression said “why not mules?” Lazarus had brought a dozen or so genetically enhanced mules on the trip. So they are definitely re-chargeable, elsewhere it’s mentioned about swapping a drained shipstone for a full one.

  • 2
    Hi, welcome to SF&F. The digression about energy density isn't really relevant; you should instead lead with the reference to Time Enough for Love. Your answer would also be much better if you directly quoted the specific bits about the Shipstone.
    – DavidW
    Commented Nov 6, 2023 at 23:37

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