Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Check out the new SourceForge HTML5 internet speed test! No Flash necessary and runs on all devices. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. ×

Comment Re:Moon- not perfect, but has possibilities (Score 1) 299

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:Its Not If We Could get to the Moon, Its Why? (Score 1) 299

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) 299

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:Does this mean more fuel for thrusters? (Score 1) 58

So if they aren't going to be using the main engine for a major trajectory shift, does this mean that more fuel is available for the thrusters?

Maybe, maybe not ; for a number of possible reasons.

(1) Do the main and attitude drive systems use the same fuels? For the large number of anticipated firings for the attitude thrusters, you'd maybe go for reliably hypergolic fuel/ oxidiser couples (i.e., on contact, they ignite). But for the main engine with only a handful of planned firings you might choose a monoprop with electrical ignition. That question is readily amenable to research.

(2) Is there a cross-feed system from main thruster fuel tanks and pressurisation to attitude thruster fuel tanks and pressurisation? Or, to rephrase the same question - is there a mission-critical need for such a cross-feed? Because if the system isn't absolutely essential, it would have not been designed. Remember that every valve (not "most" but "every") and every joint in a pressurised fluid system is a potential leak point. Again, if you find the plumbing design drawings, it's the work of moments.

It'd be fantastic to get some really good pictures of Europa (life!)

Any life on Europa which isn't considerably more technologically advanced than ours is going to be on the underside of 30-50km of ice. Now, ice pictures can be pretty, but it's a monomineralic rock with a coarse grain due to regular resublimation and/ or refreezing. Even under crossed polars and thick sections, "dull" is going to come to mind. (OK - I've probably done a few hundred thousand rock descriptions more than you. I've a higher "dull" threshold than most people for rocks. But "dull" will come.

and Io (volcanoes!).

Now you're tempting me. But not strongly enough.

Or just put it in a relatively distant parking orbit around Jupiter and (because it's solar powered) let it monitor the Jovian system for (hopefully) decades

Nowhere near enough. Decades isn't remotely good enough. When we're talking about (potentially) wiping out the only other origin of life in the universe from our own ... I'd put the "you fuck with not" time scale at several times the duration of our genus. Ten million years is a reasonable round number to start upwards from.

NASA would seem to agree with me - hence the dive into Jupiter.

Comment Re: No Dragon 2 Soft Landing Yet (Score 3, Informative) 299

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...

Comment Re:Not to be a wet blanket... (Score 1) 299

Yes, wake me up when you've recreated Earth's vast diversity of industrial infrastructure on the moon.

Spacecraft are incredibly complex thing, and you're proposing to build them on a place where you're starting with absolutely nothing. And why? To save launch costs? Yes, launch costs are expensive relative to peoples' everyday experience, but they're only a (ever-diminishing) fraction of the cost of a whole mission.

If you're planning to wait until you can outright build entire spacecraft on the moon, you're planning on pushing Mars missions off by many generations. Even the concept that simple raw, bulk sheet metal of even comparable quality (and thus mass) to that available on Earth will be produced on the moon after two decades of high budget dedicated effort straddles the line between "crazy ambitious" and "crazy". Let alone being able to build it into something of relevance with sufficient reliability, and let alone being able to produce it at a rate that, after factoring in consumables that you have to ship from Earth to keep workers alive and all industrial processes running (consumable feedstocks, maintenance, etc) isn't vastly higher than on Earth.

There is absolutely nothing "cost saving" about operating on the moon; it is a huge money sink, and will continue to be so for generations. The same with Mars. You don't go there to save money, you go there as a very long-term investment in the future.

Comment Re:Too bad we don't have 1977 technologies anymore (Score 1) 58

this is the kind of banal reply I predicted the GP would get. Don't you think everybody and their dogs already know what you wrote?

Shooting an anti-science ignoramus like hcs_$reboot in the arse is generally a positive contribution - to humanity in general and Slashdot in particular. Unlike your utterly useless comment.

Comment Re:No Dragon 2 Soft Landing Yet (Score 1) 299

Well, they did produce that huge carbon fiber tank. Which appears to have failed during one of their pressure tanks. Really, building such a huge rocket out of composites is crazy ambitious (if not just crazy), but my hat goes off to them if they can succeed.

They've also made a mini-Raptor that they've started putting through tests. The fact that they've apparently managed those chamber pressures without corrosion problems so far is very impressive.

It occurred to me the other day that they have an interesting potential "halfway" route to ITS, which is that since they clearly plan to have different variants of the spaceship (cargo, crew, tanker), they could start off with the cargo variant and instead of a cargo fairing, have an interstage and use that to boost an elongated Falcon 9 (like the Falcon Heavy central core). So the spaceship would function as a first stage until it got its own booster so that it could function as a second stage. It'd be a perfect testbed for their new technologies (same construction style and engines as the booster, just smaller), while at the same time boosting SpaceX's launch capabilities into the super-heavy range. They'd want to use more atmosphere-optimized nozzles, but apart from that... it's already designed to handle much greater heat loads as well as full propulsive landings.

Comment Re: No Dragon 2 Soft Landing Yet (Score 1) 299

He's first going to have to learn how to launch that fast. That's one area where SpaceX hasn't had much success - getting its launch turnaround times down. Hopefully they will in the future. Also, since an explosion takes them out for half a year or more (regardless of turnaround times), they better up their reliability by an order of magnitude or more, since each increase in launch rate means more possible rockets that can fail. And of course they want the ITS booster to have a service life of 1000x launches, which means an immensely high reliability.

Anyway, SpaceX's big goal is to have their satellite service give them a nearly unlimited demand for launches in the coming decade, as well as a correspondingly huge income from global sales of satellite net / communications services - and to funnel those profits into ITS. Time will tell... but there's certainly no shortage of ambition.

Comment Re:Not Happening Anytime Soon (Score 3, Insightful) 299

That's the biggest concern I have. People tire of ongoing expenses. ISS seemed neat at first; now everyone hates it. Why would a moon base fare differently?

Long-term presences in space need to very quickly cut ties with earth, on order of greatest resource dependencies down to smallest resource dependencies. Aka, first things like oxygen, propellant, etc, then to industrial chemicals, of increasingly smaller quantities, with increasingly diversified manufacturing facilities, with very complex/low volume chemical feedstocks and manufacturing processes coming last. Cutting all ties is a process that would take centuries. But you can start with the low hanging fruit, bit by bit, and keep stockpiles of everything needed for maintenance that you can't produce locally.

Unfortunately, running counter to this is expansion. Because if you double the size of your operations, you also double your resource demands. So you need to improve resource independence at a faster rate than you grow.

Part of the problem with the moon is that it's just not a great place for ISRU. Volatiles are rare. We've never even sampled any moon that aren't depleted in volatiles, although there's some data to suggest that various volatiles might be scattered in permanently shaded areas (all of them, in the same place? That's a good question). Surface mineral diversity is limited - primarily light, non-volatile elements. Oxygen is at least widely abundant, but locked up tightly. And while the moon offers short transit times, it's surprisingly not that advantageous concerning delta-V. You can't aerocapture there, landing is fully powered (no parachute deceleration), and to get there you have to already be on such a high apogee orbit that it's not much more energy to go into a Mars transfer. Gravity is less and night is two days long. There are a couple "maybe" peaks of eternal light, but that doesn't mean that they're colocated with volatiles; the last I looked into it it looked like the closest suggested find of water was dozens of kilometers away from the nearest such peak, which would be quite the commute (and thus low throughput / high wear).

The moon is certainly the "cautious" option; emergency returns / resupplies are easy there, and communication fast. Its main value appears to be a testing ground for systems while minimizing risk. But it's not a very appealing place from a settlement perspective.

Of course, I prefer Venus to Mars, but that's neither here nor there ;) I'd like to see a parallel program for both, as the same sort of booster and transfer stage can be used for both, so it's only habitat / ascent stage development costs that are doubled. And once you get past the differences in feedstock sources, production industrial processes converge (Venus advantaged by the higher power availability and easier ability to get rid of heat - excepting in the case of cryogenics, where Mars holds the advantage)

Comment Re:Younger astronauts (Score 1) 299

One, there would be howls of protest. Two, you're not taking that argument to its logical end. You should only send pygmy women by that logic.

Women do consume less resources (by a good margin on average) and take up less space, but if I recall correctly are more vulnerable to radiation-related disease. So it's a tossup depending on what factors are constraining your mission architecture.

Comment Re:Rockets are too expensive (Score 4, Interesting) 299

I have read the book, and it's an absurd degree of wishful thinking. Just ignoring the huge number of things that they just gloss over or omit outright, the materials technology they're talking about is about two orders of magnitude away from what we actually have, and might even be physically impossible. Measurements of individual carbon nanotubes (let alone bundles, let alone bulk fibres) don't approach the strengths being talked about there. Colossal carbon tube does better on an individual tube basis, but again, we're nowhere even close to the materials tech required. And for what? For a massive, very low throughput, tiny safety margin, most-failure-modes-unaccounted-for, low-power-efficiency means of access to space? Colour me unimpressed.

If you want something better, I recommend looking into Lofstrom loops (launch loops). Current materials tech, high efficiency, high throughput per unit mass, no orbit restrictions, and works even on tidally locked bodies.

Comment Re:Rockets are too expensive (Score 4, Interesting) 299

Quite true. The materials technology required is about two orders of magnitude away from actual materials technology, for starters. And among the countless other problems with space elevators, they're not actually all that efficient. Laser power beaming over those distances works out to single-digit transfer efficiencies, and microwave power beaming even less (microwave power beaming to space can be efficient, but only if the receiving antenna is huge). And no, you can't regularly hang things or run power wires up a space elevator - the mass of the cable has to be vanishingly small.

Active-suspended structures, such as Lofstrom loops, are a much better choice. Power transfer efficiency can be greater than 50% and current materials technology should be sufficient. They can also be designed to shoot payloads into any orbit (unlike space elevators), and work independent of the properties of the body in question, as well as having far greater throughput per unit mass. There's really no reason to choose a space elevator over a Lofstrom loop.

Slashdot Top Deals

The only thing worse than X Windows: (X Windows) - X

Working...