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Comment Re:...and lunges at you (Score 2) 53

I can just imagine some rogue programmer installing the following on it:

1) As big of a battery pack as it can carry as "payload", strapped to its back.
2) Facial recognition software that measures the number of and distance to any people recorded by its camera
3) Modern neural net, trained by being rewarded when the actions it takes lead to 1) it approaching other people, and 2) people fleeing from it.

' ... and then setting it loose in the streets.

Comment Re:we can't even be bothered to get that right.... (Score 2) 127

Another option apart from orbit is going to L2 and back, if they want to basically "hover" with the moon blocking the Earth, right on the cusp of drifting away from the Earth-Moon system and into a free orbit around the sun. They'd be the first people ever to go there. It's 3.5km/s outbound, 0.6km/s back. Or if they want a long-duration stay (~100d) they can get back by the interplay of the Sun-Earth-Moon system for only 0.1 km/s (in the process going way far away from Earth).. There's probably some such returns with intermediary dV and durations as well.

But obviously a free return trajectory is the lowest energy. If I recall correctly Apollo's burn was ~3.2 km/s

Comment Re:Onward to Venus [Re:Moon- not perfect, but has. (Score 1) 324

That's an old graphic, but yes, we have an excellent artist aboard. Of course, they mostly want to go for what looks the most aesthetically pleasing, while I'm always niggling on the technical details ;) The conversations usually go like,

"But.... you can't have people living there, the ballonets are going to expand into that when they launch the ascent stage... either the ballonets are going to dramatically expand or the habitat is going to dramatically collapse, take your pick. And if you store the ascent stage that close, it's going to destroy the whole habitat if there's a mishap while it's fueled. And how can I possibly fit all of that floor area into the fairing? Plus I don't see any scrubber for ISRU... it's going to need to be big, I'm struggling to get the absorption figures to work for sufficient resource collection with a 4.2 meter prop....." ;) But really, so long as their final graphics don't end up with a giant pirate flag or anything like that, I'm sure we can deal with a bit of "artistic license" :)...

Oh wait a minute, I just noticed your username. Geoffrey.landis? As in, the Geoffrey Landis? Oh wow, hey, we should chat some time. ;) (bare minimum, I at least need to ask for permission to reproduce some figures from a few of your papers). If you get a chance, definitely drop me a line at mQeme@eaQku.neQt (remove Qs to despammify). I actually just dropped by Slashdot as a break in the middle of working on some graphics illustrating non-Hohmann transfer times vs. delta-V between Earth, Mars and Venus, demonstrating the advantage Venus has due to the Oberth effect ;)

Comment Re:Rockets are too expensive (Score 1) 324

1) It's about 7% of what NYC consumes, not 10%. NYC being only a tiny fraction of total US demand, which is in turn just a fraction of world demand. Global electricity production averages around 15 TW.

500MW is a moderate sized power plant. Not even a large one. It's nothing that impressive. Cost of such a plant is 500M-$1,5B, which is nothing by rocketry standards.

2) That's not 500MW to stand idle; that's 500MW to launch 175 tonnes per day. That's 68.5kWh per kilogram. $7 of electricity per kilogram. Oooh, what a terrible waste of power.

3) If that's too much, the larger version uses significantly less per kilogram.

Is there some reason to get so much mass out of this gravity well

Do you seriously have to ask what sort of market there would be for ~$800 tickets to orbit? I'm sorry, but we're not talking "for the wealthy", we're talking for everyone at those prices.

Comment Re:Moon- not perfect, but has possibilities (Score 1) 324

I mentioned that. The discoveries on lunar water are in consistent (for example, non-detection by Kaguya, disputed detection by Deep impact, criticism of Chandrayaan's detection as not being consistent with solid ice (at best small ice particles), etc. But I do agree that on the balance the evidence is pretty compelling that there are places where ice could be recovered/produced. Even if you take the optimistic view on volatiles (not just water), they're clearly not evenly spread, and generally seem to be (as expected) at significant driving distances from lit regions. Workable? Probably. Ideal? Not really. But hey, it's certainly a better outlook than it was a couple decades ago :) I'll be a lot happier though when we have some ground truth on the subject showing CHONPS all in the same general area ;)

Hey, we're thinking along parallel lines!!

I'm part of a group called Venus Labs that's actually developing the concept further, doing more detailed studies on each component of the concept that Landis presented. :)

Comment Re: Rockets are too expensive (Score 1) 324

First,use an extremely efficient propulsion system like electric propulsion to shed said energy and provide the mundane control needed for the system.

Adding more energy seems unlikely to help.

Second, you can run payloads down the tether at the same time as your run them up the tether. That would keep the energy balance stable.

Again, not a freshman-physics pendulum. We're not talking spherical cows uniformly radiating milk here. The upwards and downwards payloads would be in different places on the tether (except momentarily) and so would each be doing there own thing to complicate the system.

You might find it entertaining to watch some youtube videos of 2- and 3-section pendulum, elastic pendulums, and so on. They don't work and play well with others.

Comment Re:Its Not If We Could get to the Moon, Its Why? (Score 1) 324

Not exactly. Minimum energy trajectories are really undesirable for humans. Fine for cargo, but you get a lot of time cut off the trip with just a relatively small amount of extra delta-V. Seriously, I recommend running out the numbers for fast Hohmann transfers to Mars - assuming aerocapture, it's a major improvement at little cost.

SpaceX, for one, wants fast transits with ITS. And I don't blame them.

Comment Re:Hydrogen is really useful for going places (Score 1) 324

SpaceX's kerosene is a good decision for putting stuff into low earth orbit compared to hydrogen. When you go farther away than that, the hydrogen advantage kicks in. For Low Lunar Orbit and Mars transfer orbit, hydrogen is very useful.

The problem with going further away on hydrogen is that hydrogen is not generally considered a "storable" propellant; it's very hard to manage boiloff. Mild cryogenics like methane (SpaceX's plan) are easier. It allows you to use the same stage for transfer, entry, and launch burns.

Also, the Falcon heavy will need an extra stage to go much beyond geosynchronous orbit

Why? It's a 3-stager (or if you'd rather not count boosters as full stages, 2 1/2). Designed specifically with Mars missions in mind. 3 stages is a good number for kerolox missions to MTO if the stages have a low mass fraction (like SpaceX's do). You could even do it with 2, although it'd cut your payload.

The SLS solid boosters seem ready now.

They're not. You're confusing test firing with completion.

The big SLS first stage will probably be ready in 2 years.

In your dreams. The smallest variant isn't scheduled to fly for 1 1/2 years, and that's assuming that the schedule doesn't slip. That's Block 1, 70 tonnes. Block 1B (again, assuming no schedule slips) isn't scheduled until 2021 - and that's only 105 tonnes. There's three scheduled launches of Block 1B, the last in 2026. The latter being asteroid redirect, which, well, don't hold your breath ;) There are no scheduled launches of Block 2 (130 tonnes).

You have this weird conception of how far along SLS is. They only even finished the test stand for the tank last month.

Comment Re: No Dragon 2 Soft Landing Yet (Score 4, Interesting) 324

What, exactly, is the purpose of hanging in the clouds of Venus ?

What, exactly is the purpose of hanging out in the near-vacuum of Mars?
What, exactly, is the purpose of life?

If you don't agree with the merits of the human race becoming a starfaring civilization centuries from now based on investments made today in getting the ball rolling today, I'm not going to debate that with you. But if you agree with that, then the whole point in expanding offworld is to develop into a multiplanetary species, where demand drives down launch costs and we learn, step by step, to make everything that we need in offworld environments and to become adept at the multi-month journeys between planets. At first, it's a sunk cost. With time, it's increasingly supported by trade. And after long periods of time, it brings the immense resources beyond our planet into our grasp.

If you want to talk about economics on Venus, here's a few for you.

  * Power is immensely abundant. Many technologies that we employ are basically energy costs - to pick an example, isotope enrichment. So once the higher marginal capital cost for doing things on Venus becomes overtaken by the greater energy availability, Venus becomes the logical place to conduct such activities.

  * Deuterium levels are ~240 times higher than on Earth. So depending on the level of enrichment you need and the means by which you return it, if you can return goods for somewhere in the "couple thousand to several tens of thousands of dollars per kilogram" range, it's profitable. Deuterium recovery can be rendered an inherent part of nighttime fuel cell power storage, since electrolysis has an excellent enrichment factor.

  * Venus's lavas appear to be highly differentiated, and there's a great degree of chemical weathering and atmospheric processing, which can be another resource enrichment process. So concentrations of high value ores far greater than are found on Earth are not unrealistic. There are a couple dozen elements whose values are worth exporting at realistic launch costs several decades from now.

  * Even simple rocks from offworld have great value (collectors, luxury goods, etc). It's not theoretical - people really do pay huge sums for offworld items. Their value will of course depend first the abundance of their export (if you export 100kg per year, you can sell for 10x more per kg than if you export 10000kg per year, which you can sell for 10x more per kg than if you export 1000000kg per year...). If you're selling in small quantities, the value could be in the millions of dollars per kilogram. Venus's surface atmosphere is dense enough that you can outright dredge loose rocks.

  * The size of the market and sensitivity to export quantity also depends on their aesthetics (aka, moving more from the collectors market into the larger luxury goods market). This means minerals that are durable and aesthetically pleasing. What we've sampled so far of Venus's surface fits that bill - gabbro (sold as "black granite" - large crystalled, dark, hard rock, forms excellent slabs), anorthosite (rare on Earth, often associated with labradorite, which is an iridescent bluish-purple semiprecious to precious mineral), troctolite (rare, olivine (peridot)-rich relative of anorthosite and gabbro - looks like this when cut and polished), etc. It's one thing for your typical sheikh or dotcom millionaire to say "my yacht's countertop is made from the finest tuscan marble." It's another to say "my yacht's countertop is from freaking Venus." You're looking at a very large market in the 4 figure/kg range, a reasonable market in the 5 figure/kg range, and a small but decent market in the 6 figure/kg range.

  * Venus's apparently high levels of repeated differentiation, in conditions very different from Earth, likely mean that some minerals, including gemstones, that are rare or nonexistent on Earth exist there, potentially even abundantly. The gem market on Earth is massive, and always looking for something new to set their gems apart and boost their value. The value per kg of gemstones makes even the most expensive rockets look cheap - a single diamond of a rare type can auction for upwards of the cost of an entire Falcon Heavy launch.

  * On the opposite side of a spectrum, once a colony is "mostly" self-sufficient, it can justify imports just by "telecommuting". If a colony can sustain itself by, say, 80% of people working domestically, with the import-needs of the whole colony averaging out to 5kg per person annually, and a telecommuter's salary can pay for the import of more than 25kg of goods, then the colony is on a whole running cashflow positive just from telecommuting labour.

  * Part of the goal of people like Musk is cost reduction so that travel between planets becomes an option for anyone, including those just looking for the experience. Look at how many people risk their lives and spend a good chunk of $100k every year trying to climb Everest. On Venus you can skydive into hell, to a surface where you can fly, around mountains covered in things like tellurium or pyrite frosts and snows, where cliffs are steeper and higher than Earth's crust can physically support and where riverbeds have been carved by unknown substances, most likely exotic lavas like natrocarbonatites (looks like oil, flows like water, and glows crimson at night). Of course, your habitat itself is big enough to support skydiving indoors. Tourism becomes most definitely an option.

  * Meanwhile, people to whom the concept of living a pioneer life is appealing - making things with your hands, harvesting and processing plants, even things like homemade soaps and paper - can afford to sell their homes and go live that life if they so choose. The overwhelming majority of people won't choose that life; the fraction will be very small. But a very small fraction of billions of people is still a lot of people. A reasonable "budgeting" scheme for a colony to sustain itself would be to require everyone to purchase a round trip ticket and prepay (before each launch window) their share of the colony's imports; if they can't afford their share of the next launch window's imports, then they leave at the next launch window. Also included would be an agreement that they would conduct a share of the colony's labour, with them also making a down payment to cover the costs of bringing in (subsidized) labour if they don't have a job there (or are fired for failure to actually work); so long as they continue to do their job, they only have to cover the cost of their share of the imports. More well-to-do people could just opt to keep paying the labour cost every year so that they don't have to work. By contrast, people who don't have the means to afford a trip on their own could go there for the job opportunities. And there would be a wide range of work - agricultural, food preparation / processing / storage, laboratory, medical / dental, construction, maintenance, manufacturing, refining, remote piloting of surface vehicles, janitorial, and on and on.

Now, concerning space in general: If you think humanity should just wait, or forget about that altogether - you're certainly entitled to that belief. But otherwise...

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