Next month the DSTART team will present the first version of their starship-scale MELiSSA computer simulation at the AgroSpace-MELiSSA workshop in Rome. The simulation allows the team to test the robustness of the MELiSSA system as it travels through deep space across extended periods of time.
DSTART, the TU Delft Starship Team, is bringing together a wide variety of disciplines to perform advanced concepts research for a resilient interstellar space vehicle, to be constructed from a hollowed-out asteroid. The aim is not just to focus on the necessary technology, but also to consider the biological and social factors involved in making such a gargantuan voyage feasible.
If our readers may have noticed this design is almost a polar opposite to the recently posted wisp-craft (photon sails of modest size, having well-under-one-kilogram payloads, supposedly reaching a stunning 5% to 20% of the speed of light before ejecting from the Earth:Sol system). These generation ships are huge. As per the graphic, a substantial amount of the resting mass is the carved out asteroid behind which the generation ship is fabricated.
Why is this? Why so diametrically opposite in scale, mass, design? The article lays out the design criteria, the necessity of having interstellar radiation shielding, as well as front-facing relativistic shielding. And we understand that part of the asteroid becomes reaction mass, stuff to chuck out the anterior, to gain thrust and acceleration. Got that. But why the truly gargantuan scale?
Well, as it turns out, the larger you build a starship, the exponentially larger the reaction mass needed to get it to your drift velocity. And in the end every part of the calculation is a scaling off the accumulated mass, but at the base, the “payload”. In this case, the thriving community of space explorers who — unlike computers, AIs and robotics — need to LIVE. To eat, exercise, work, have fun, sleep, get sick, get well, get old, die and make new people in turn. Many of the ‘’people maintenance’’ functions we can imagine are really pretty easy to turn over to AI powered robotics.
Robotic scullery maids, so called “manservants”, manufacturing ‘bots, surgery ‘bots, exterior repair ‘bots, science ‘bots. Since a large generation ship will have what, thousands(?) of living people to support, there will be rather large scale food production. Large scale pîss and pôop recycling; large scale farming, food fabrication (AKA “cooking”), you name it. Apart from the rate at which brought-aboard-at-launch foodstuffs decompose and degrade (especially to the energetic incoming wash of space radiation), the added mass of ‘throw away food’ (use once, becomes reaction mass?) isn’t likely to keep hundreds-to-thousands of people alive for hundreds-to-thousands of years.
Because if we’re sanguine in our consideration of just how long said asteroid-turned-generation-craft is going to be plying the Heavens to get (say) to some star only 25 light-years distant, If we’re realistic, it’ll definitely take hundreds-to-maybe-a-thousand years. Of course, without discovery or invention of a reactionless, efficient physics defying over-unity drive. (WITH the magic wand, one can do near-anything. The time-thus-asteroid-shielding needs remain similar, but the duration of the trip drops dramatically.)
Finding a path back to my lead idea, the mass of the ship depends on a multiple of the mass of the payload, where the multiple is not a constant. Literally, it is an exponential function. A 75 kilo (12 stone) space genius is going to require how much initial food, how much oxygen, how much water, how much clothing, equipment, bedding, tooling, … etc. But rather like a really large hospital, every person does not need a whole share of each of those things. Yet, taken together, the aggregate of equipment, support, cafeteria outfitting does increase with the number of people.
And if you take ‘’all that people stuff’’ as The Payload, then multiplying out the asteroid fat body in front, the propulsion drives, the photosynthesis tankage, the ancillary and tertiary stuff, the mass grows from wisp-craft to BEAST rather rapidly. Without reactionless space drive technology (the magic wand), without that, speeds of only 1-to–2%-of-lightspeed are within the realm of possible. That speed, and the necessity of slowing down again when the chunk-o-rock craft gets to the target star system. (Actually ‘’flying straight thru’’ is a far better objective – the only necessity is to change course once the whole thing gets there, to aim at another reasonably close system. And so on. Science … over colonization.)
Anyway, read on.