[ardillaroja]

How hard would it be to create a gun that produced this new knightship and is that something the community would be interested in doing?

I could imagine it being trivially easy or mind-blowingly hard and have no intuition on what's more likely :)

[dvgrn]

Everyone would be completely floored if someone built a gun for the new knightship. It's likely to be several orders of magnitude harder to find a glider synthesis for the knightship, than it was to find the knightship itself.

To build some intuition on the difficulty, check out the list of spaceships for which a glider synthesis is known: http://conwaylife.com/wiki/Glider_synthesis#Spaceship_synthe... .

Except for the macro-spaceships (some of which are pretty trivial to construct because they're self-constructing anyway!) and the Corderships, which aren't elementary and are made out of easily constructible pieces, the biggest spaceships with known constructions are all far smaller than Sir Robin, and most of them are lower period.

Every time you add a few cells to the size of an active pattern like this, you probably double the total difficulty.

"The task of constructing such a spaceship has been likened to building a Formula-1 race car whilst it's on the track and travelling at 200mph." ( http://www.conwaylife.com/forums/viewtopic.php?f=&p=55205#p5... )

[DonHopkins]

The Universal Constructor [1] running in John von Neumann's 29 state cellular automata [2] is able to construct passive configurations that aren't "powered up" with excited states in them (encoding information and synchronizing activities).

Once it's done building a machine (like a copy of itself, or anything else), it can connect its construction arm up to the "umbilical" plug of the child (like a usb port for downloading data into its storage loop), switch from "execute instructions" mode to "copy instructions" mode, and loop through its own instructions again, injecting a copy of its program into the child's storage loop, which the child can then start executing and eventually pass on to its own child.

It would be impossible to construct a "powered up" machine -- the signals would leak out into the world from the partially constructed machine and cause havoc. So you have to build a passive machine in the "powered down" state, then activate it by injecting a signal and (possibly) downloading instructions.

There are certain unconstructible "garden of eden" configurations (like a real-time crossing gate that looks and acts like an intersection with synchronized stop lights [3, p. 468, fig 3]) that are possible for God to build with a cell editor, but are impossible for a universal constructor to construct, because there is no practical way to inject and synchronize the signals into the machine after it's constructed [4].

But there are constructible "auto initializing" machines [3, p. 474, fig. 17] with one-time initialization circuits that trigger once then deactivate by firing "explosive bolts" when you power them up, bootstrapping all the internal synchronized signals necessary for the machine to operate. But of course they tend to be larger and more complicated than equivalent unconstructible machines.

[1] https://en.wikipedia.org/wiki/Von_Neumann_universal_construc...

>As defined by von Neumann, universal construction entails the construction of passive configurations, only. As such, the concept of universal construction constituted nothing more than a literary (or, in this case, mathematical) device. It facilitated other proof, such as that a machine well constructed may engage in self-replication, while universal construction itself was simply assumed over a most minimal case. Universal construction under this standard is trivial. Hence, while all the configurations given here can construct any passive configuration, none can construct the real-time crossing organ devised by Gorman.

[2] https://en.wikipedia.org/wiki/Von_Neumann_cellular_automaton

[3] http://uncomp.uwe.ac.uk/free-books/automata2008reducedsize.p...

Buckley, William R. (2008), "Signal Crossing Solutions in von Neumann Self-replicating Cellular Automata", in Andrew Adamatzky; Ramon Alonso-Sanz; Anna Lawniczak; Genaro Juarez Martinez; Kenichi Morita; Thomas Worsch, Proc. Automata 2008 (PDF), Luniver Press, pp. 453–503

[4] http://www.molecularassembler.com/KSRM/2.1.4.htm

>2.1.4 Limitations of von Neumann's Cellular Automaton Model

>For instance, one might wish to introduce a new primitive cell state in the system to permit signals to cross without interference. A “wire-crossing” organ can be devised using only the original von Neumann primitive cell types, but this introduces an unnecessary complexity into the machine design process since the organ contains initially active cell states whose creation involves considerable extra care to avoid the propagation of spurious signals. This extra care is especially critical because the cell system, as von Neumann originally constituted it, is highly susceptible to signal errors. (He undoubtedly intended his probabilistic machine model to mitigate this sensitivity and fragility.)

[DonHopkins]

Here's another cool self replicating machine with moveable parts that uses some of the same principles:

https://www.youtube.com/watch?v=09Q5l47jTy8

Self Replication #2

>A simulation of a self replicating programmable constructor in a two dimensional discrete space supporting about two dozen different types of component part. The machine can create new parts out of nothing as it needs them. See www.srm.org.uk for more details.

https://www.youtube.com/watch?v=PBXO_6Jn1fs

Self Replication #3

>A simulation of a self-replicating programmable constructing machine in a simulation environment that supports moveable parts. The machine obtains parts from its environment and uses them to make a duplicate machine. Visit www.srm.org.uk for more information.

http://www.srm.org.uk

>Self-Replicating Machines: Will Stevens. This site is about work related to self-replicating machines that I carried out for my PhD thesis with the Department of Physics and Astronomy at the Open University in the UK between 2004 and 2009. I am interested in physically realistic simulations of self-replicating machines made from simple component parts. On this website you will find an introduction to self-replicating machines, published papers about my research, animations from simulations of self-replicating machines, simulation software that you can download, and links to other work related to self-replication.

For a wildly bold approach to robust computing, with moveable damage-resistant self-repairing parts, check out Dave Ackley's Movable Feast Machine!

http://movablefeastmachine.org/

>The Movable Feast Machine is a robust, indefinitely scalable, computing architecture.

https://news.ycombinator.com/item?id=14236898

>The video "Distributed City Generation" demonstrates how you can program a set of Movable Feast Machine rules that build a self-healing city that fills all available space with urban sprawl, and even repairs itself after disasters!

https://www.youtube.com/watch?v=XkSXERxucPc

>A rough video demo of Trent R. Small's procedural city generation dynamics in the Movable Feast Machine simulator. See http://nm8.us/q for more information. Apologies for the poor audio!

https://www.youtube.com/playlist?list=PLm5k2NUmpIP-4ekppm6Jo...

>Robust-first Computing playlist. Videos introducing and exploring inherently robust computational systems.

https://www.youtube.com/playlist?list=PLm5k2NUmpIP8qwttAS5Ba...

>Movable Feast Machine v2 demos. Presentations and demos of research projects built on the MFMv2 simulator.

[dvgrn]

Von Neumann's 29 states were custom designed to make it easy to construct passive configurations, similar to the way a 3D printer builds things -- one layer at a time.

You can't do that in Conway's Life, because stable patterns in Life aren't necessarily stable when you add one cell at a time. But you can do the next best thing, which is to design circuitry that's made out of small stable "Spartan" pieces -- and then build the pieces one at a time.

Related to this, there's an equivalent for building passive structures and then activating them. In Life you can build a static "one-glider seed constellation". Hit the stable constellation with a single glider, and a few ticks later you have a working spaceship. Example:

http://www.conwaylife.com/forums/viewtopic.php?f=&p=57674#p5...

However, there's no reasonable expectation of figuring out how to build a one-glider seed for the Sir Robin knightship any time soon -- the knightship is way too fast, active, and complex. With current techniques a search for such a thing would likely take millions of years.