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Technology / Re: soundproofing in a 3d printed house?

« on: 08/05/2021 14:40:15 »

    The OP idea of evacuating a small space between walls of each room seems like quite a good one to me.  Previous replies have already mentioned the obvious problems, benefits and practical requirements.  It seems that a partial vacuum would be more realistic since it will reduce the forces on the cavity walls.  No-one has mentioned that the OP idea would also help with heat insulation in addition to sound insulation.

    A hybrid of methods to help with sound insulation is probably going to be more realistic.  Janus has already mentioned one practical idea - the use of staggered studs.  The 3-D printer could also be programmed to produce sound-cancelling patterns on the walls.  Typically small pyramid shapes are placed on the wall under the principle that sound reflects off these surfaces and the superposition of waves will be destructive, annihilating the sound.  If you don't want to look at walls with this sort of pattern then you can put the pattern on the inside surface of the cavity walls.

   I expect there are many things that could easily be adjusted and improved for a 3D printed house but I suppose the short term concerns are just building quickly and cheaply.  Any extra material (to increase strength of the walls or create patterns) would only increase cost and production time.  There also seems to be a limited serviceable lifetime for such houses and a need to minimize any repairs or regular maintenance.  A vacuum cavity wall is very likely to develop a leak and require maintenance and this may defy the original purpose and design brief for this new technology.

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Technology / Re: Is it possible to tow a rocket into space from space?

« on: 16/08/2020 04:21:46 »

towing rockets from space

Trying to tow something when there is a big difference in velocity is problematic.
- The original post imagines a spaceship in orbit, traveling 11km/second
- Which tries to tow a "stationary" space probe on the ground, which is moving perhaps 1km/second due to the Earth's rotation
- This requires a towline which is incredibly strong and light, and yet incredibly resilient to withstand a sudden change in speed of 10km/second
- We are talking about something much more "stretchy" than spider silk, here!   

towing rockets from space

There is one area where towing objects in space has been actively investigated: diverting near-Earth asteroids.

You can use a "big bang" approach, and try to smash something into the asteroid
- But that risks turning a dinosaur-killing 10km asteroid (which devastated life over the whole Earth)
- into 10 to 1000 smaller asteroid pieces, each of which could devastate life on 10% of the Earth. Not a real "win".
See: https://en.wikipedia.org/wiki/Double_Asteroid_Redirection_Test

A gentler solution has advantages (if you have enough advance warning to prepare).
- It does mean that you need to rendezvous with the asteroid/comet, ie match orbits, so there is a low relative velocity.
- Then you can try towing, pushing or just "being there" to exert a gentle force on the entire asteroid.
- If the asteroid/comet is a loose pile of rocks (as some of them seem to be), push won't work well, and towing won't work unless you enclose the comet in a net.
- But the "gravity tractor" idea has the space probe exert a gentle gravitational force on the whole asteroid, which will divert its course (if you do it for long enough)

So you don't have large differences in speed, and just exert a slow, steady force over many years.
See: https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#Asteroid_gravity_tractor

Providing enough fuel to exert this steady force is is a problem in itself, which is why some of the asteroid-diversion proposals suggest using solar power.
See: https://en.wikipedia.org/wiki/Asteroid_impact_avoidance#Focused_solar_energy