Chassis

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Introduction

The Chassis is entirely non-biological. It consists of a Skeleton broadly based on the natural human model, with a number of improvements and simplifications (e.g. wrist and ankle joints), an outer Integument with a large number of embedded sensors, and a number of internal Compartments with attachment points for the various life-support modules. Variable amounts and types of synthetic Connective Tissue may also be present, serving as padding, insulation, and filling out the overall body shape, as required.

Requirements

Skeleton

The skeleton should be made of a light but strong material. Some form of composite seems a likely candidate. Doesn't have to be all made of the same stuff. Joints and shafts have different requirements, so making them from different materials might make sense.

Standard land-animal model is a good start, but no need to be constrained by it. Is there a need for the double-bone arrangement of the lower limbs, for example, or is that another example of an evolutionary kludge that got 'baked-in' at an early stage? Can it be improved on?

Anchor points for detachable ligaments and muscle-module tendons need to be present.

The joints should be detachable from the shafts of long bones (knees, elbows, etc.), so they can be removed and repaired/replaced separately (joints wear out more often than bones do).

The spine won't need an internal space for a spinal cord, and can probably be simplified, with less segments (vertebrae) than the natural model.

As the bones won't contain marrow, a separate Red Marrow organ module will be needed (see Refactoring).

(diagrams needed)

Strain sensors attached to, or embedded in, the bones would be a good idea. Vibration sensors could be useful too.


Integument

This includes all the outer covering (skin, nails, hair/fur, scales, feathers, ...)

Making the outer skin non-biological is a contentious decision, and presents several challenges. The benefits are that the skin can be made much tougher than natural skin, can have any desired texture and colour, and the ability to include a wide range of sensory capabilities. It also fits in with the general aim of encapsulating all biological parts in synthetic protective coverings.

The main disadvantage is the lack of self-healing ability, so any damage would need to be repaired. Lack of sensitivity would not be an issue (see Sensory Systems).

Different regions of the body have different requirements for the outer covering. Nature has to compromise, and use variations on the same materials (living skin and proteins produced by cells, in combination with a limited set of minerals) for all these requirements. We don't. We have a huge range of possible materials to choose from.

Some regions need very flexible skin (round and near joints), some need tough/hard coverings (e.g. feet), some need high sensitivity (hands), etc. Specialised regions could have completely different properties to others (nails, eye coverings, etc.), and various useful features could be built-in (incorporate tools or tool-sockets into fingers/nails, for example).

The materials used will vary widely. Possibilities range from very hard materials such as ceramics and metals, hard polymers that mimic horn and nails, fibrous sheets similar to leather, through to extremely soft silicone rubbers. Seams of some kind will need to be incorporated (see Access).


Compartments

The skeleton is mainly useful as a set of levers for muscles to move. A secondary role for some bones is protection of internal organs. Attachment of organs is to sheets and strands of connective tissue, and a degree of compartmentalisation occurs in natural bodies, with double-walled membranes surrounding the organs either singly or in groups (pleura, peritoneum, myocardium, etc.).

Organ modules will need to be attached to the chassis, held in stable positions and protected from mechanical damage. Internal compartments made of materials analogous to connective tissue, with various mechanical properties can do this. As with the external skin, access points will need to be built-in to the compartments.


Connective Tissue

This performs various functions in the natural body, including mechanical support, energy storage (adipose tissue) and simple padding.


Access

The main point of the Mk2 body is to be able to easily remove and replace components. To allow this, some way of accessing the interior of the body needs to be provided. Our natural bodies need to be cut open in risky (and painful) surgical procedures to access the inside, but a designed body can have access points built in, which can be opened and closed without causing any damage. Access points need to be compatible with a flexible skin, be watertight, and not interfere with the external aesthetics of the body. Preferably, they should be invisible when closed, or integrate with the body design so as to be unobtrusive.

What Exists Now?

What can be done right now?


What's Next?

What needs doing now?


Brainstorming

  • Eliminate messy joints like wrist and ankle, replace with simple effective designs (seven bones to give 2 degrees of freedom is just ridiculous). Possibly get rid of double-bone idea in lower (distal) limbs, replace with proper rotary joints (@ distal or proximal ends? Or both?)


  • Sheets of elastic 'ligaments' to hold together joints where needed. Probably less of these needed than in biological skeleton.


  • Attachments for bones, ligaments and tendons:

All attachments should be easily unfastened, but strong, and not come unfastened by accident. Some kind of interlock system.

Possible types of fasteners (diagrams needed)
zips, or zip-concept structures

(interlocking tabs with a mechanism for moving the tabs)

hook-and-eye
bolts/screws
velcro
spring-loaded wedges
wedge anchors
expanding screw


  • Synthetic tendons with attachments to muscle modules (tendons could be an integral part of the muscle modules, or separate items with fastenings at each end).


  • Spine redesign. Will not contain spinal cord, can be optimised for strength. No need for so many elements (look @ cervical vs. lumbar spine of giraffe)

What kind of joints in spine?


  • Consequences of non-standard feet/hands? (e.g. extra muscles, coordination, etc.). Feet could certainly do with a redesign, and hands could be better (properly independent finger control, possibly an extra thumb on the outside of the hand)


  • Simplified muscle arrangement? (why do we have so many muscles? Is it necessary? Evolution often produces unnecessary complication, but also redundancy can be good. Need to sort out one from the other, here)


  • Skin Needs to be flexible, have seams or other means of ingress to body, easily replaceable (wear & tear), Sensors. Look & feel. Can have different types on different parts of body if necessary/desired (a lot more variation than in nature)