I am skeptical whether the really optimistic versions of nanotechnology are really physically possible. When you get down to the real nanometer scale, you're working with chemical systems rather than 'mechanical' systems. Viruses are tens of nanometers, and they can't really fit in enough stuff to be independently self-replicating. Ribosomes by themselves are on the same scale (~20 - 30 nm).So you'd probably have the same limits as biochemistry - needing a liquid medium and therefore a relatively limited temperature range (between freezing and boiling of your liquid medium), relatively limited energy use (to avoid damaging the molecules), etc. - but maybe with extremely advanced SF tech you could use a supercritical fluid medium and relax the temperature limits somewhat?
Quote from: Vultur on 10/26/2025 07:57 pmI am skeptical whether the really optimistic versions of nanotechnology are really physically possible. When you get down to the real nanometer scale, you're working with chemical systems rather than 'mechanical' systems. Viruses are tens of nanometers, and they can't really fit in enough stuff to be independently self-replicating. Ribosomes by themselves are on the same scale (~20 - 30 nm).So you'd probably have the same limits as biochemistry - needing a liquid medium and therefore a relatively limited temperature range (between freezing and boiling of your liquid medium), relatively limited energy use (to avoid damaging the molecules), etc. - but maybe with extremely advanced SF tech you could use a supercritical fluid medium and relax the temperature limits somewhat?Discussion of nanotech is getting close to off-topic here, but it really is the limiting case for "how cheap". I felt back then that Drexler's diamondoid nanotech was achievable, but we had not figured out the intervening levels of "assemblers" needed to get from micron scale down to atomic scale. The hope was that it did not violate the laws of physics, so eventually a smart enough intelligence would be able to achieve it: a brilliant human, or a very lucky research group, or an advanced AI. That's where the synergy comes in: advanced AI builds advanced production which builds the advanced computing needed for more advanced AI. Also making fusion possible, by any of several routes that depend on the extreme precision provided by the advanced nanotech. Singularity.
If there is some damping effect in the actual real world, then Singularity may not end humanity but limit this advance at a more human level. If so, that nanotech may still be available to drive the cost of all material goods to near zero.
If we wish to continue this "how cheap" discussion here, we will need to set some ground rules on timescale and which technologies we are discussing.
If it's multi-ton orbital contraptions required to develop the tech, then cost is critical. 100 tons at $5k per pound is a billion. At $50.00 a pound it's 10 million. High risk development will depend on lower costs.
Quote from: redneck on 10/26/2025 10:50 pmIf it's multi-ton orbital contraptions required to develop the tech, then cost is critical. 100 tons at $5k per pound is a billion. At $50.00 a pound it's 10 million. High risk development will depend on lower costs.$50/pound is $110/kg, which is at the far upper end of what we're discussing in this thread.F9 launching with a pretty full payload is already cheaper than $5k/pound. 22000 kg for $70M is about $3200/kg or $1450/pound.
Looking in the other direction from the nanotech side to the larger scale question:What metric of 'cheap' are you optimising for?Is that 'cheap' in currency cost? Energy cost? Raw material cost? Is that cheap only relative to the cost of manufacture Earthside (and which country)? If you're manufacturing in space, whose currency are you using? Do launch costs and orbit-to-orbit transfer costs factor in? And if so is that financial or energy costs? etc. These seem like 'obvious' questions because the answers are simple today, because "manufacture on Earth and pay for it in local currency" is the only option available. Once more options are available, things get less simple.
I believe the Depot and Starship Tanker should have pumps to pressurize the gas in the providing tanks and draw excess gas from the receiving tanks. This only needs to be about 1/2 bar differential. This way fuel transfer can be done with no loss. A Howden Roots Tri-RAM Model 409 would be a good choice. It's rather heavy at 152kg and that does not include the electric motor to drive it. A customized version could be built with lighter weight materials and save about 40%. https://www.pdblowers.com/product/roots-tri-ram-model-409/?srsltid=AfmBOopLFBhBcK3PKg3Gjc1eRBZbF3fLMquL_FQVAbf8B3N0U2NNNak0
Quote from: edzieba on 10/27/2025 07:46 amLooking in the other direction from the nanotech side to the larger scale question:What metric of 'cheap' are you optimising for?Is that 'cheap' in currency cost? Energy cost? Raw material cost? Is that cheap only relative to the cost of manufacture Earthside (and which country)? If you're manufacturing in space, whose currency are you using? Do launch costs and orbit-to-orbit transfer costs factor in? And if so is that financial or energy costs? etc. These seem like 'obvious' questions because the answers are simple today, because "manufacture on Earth and pay for it in local currency" is the only option available. Once more options are available, things get less simple.Time opportunity cost turns into a vector equation, as your value is a function of relative orbit, mass, and THEN the functional value of the item itself. Having statites in mercury orbit ready to drop cargo outbound sounds like an amazon model.
American sea-launched orbital launch vehicle. Proposed expendable, water launch, single-stage-to-orbit, liquid oxygen/hydrogen, low-cost launch vehicle designed to carry small bulk payloads to low earth orbit. A unique attribute was that low reliability was accepted in order to achieve low cost.Status: Study 1998-2006. Payload: 1,000 kg (2,200 lb). Thrust: 818.00 kN (183,893 lbf). Gross mass: 130,000 kg (280,000 lb). Height: 43.00 m (141.00 ft). Diameter: 4.00 m (13.10 ft). Span: 4.00 m (13.10 ft). Apogee: 370 km (220 mi).The Aquarius Concept was launch of low-cost supplies on a low-cost vehicle. These would be low-cost, easily-replaced consumables such as water, fuel, food, and air as needed by the International Space Station and military spacecraft. Launch failures would be acceptable since the intrinsic value of the replaceable consumables was low. About one-third of the launches were expected to fail.The lowest-cost vehicle was a single-string, single-stage, single-engine low-margin vehicle built using non-white-glove labor and facilities. Low margins were consistent with a one-third failure. The loss-tolerant payload and vehicle required an appropriate supporting infrastructure. An ocean-based floating launch infrastructure was low-cost and tolerated failures.Orbital retrieval of the payload would be by a space-tug (e.g. the ASTRO vehicle then being developed by the DARPA Orbital Express program, or other vehicles being studied under the NASA Alternate Access to Station study. Practical vehicle sizing led to a ~1 metric ton palletized payload to 200 km circular orbit with 52 deg inclination (Space Station). The cost target: $600K per launch at ~100 launches per year.
