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Comment Re:Catastrophic man-made global warming (Score 2) 269

Perhaps, perhaps not. Venus is still very poorly understood. In its high temperature environment its conditions are largely self-sustaining (preventing the sequestration of CO2 in rock), although it's also unstable, prone to broad temperature and pressure swings. It also appears to have undergone a global resurfacing event about 300-500mya, if that gives a clue as to how unstable the planet as a whole is. ;) We don't know what caused it, or really anything about it. Part of the planet's properties are now a result of it having lost its water rather than being a cause, such as its hard crust. Obviously its lack of a magnetic field is responsible for its loss of water, but we don't know exactly when or why it disappeared (there are of course theories... I had always just assumed it was the slow rotation rate, but the last research I read suggested that not enough to account for it). Other issues as to how Venus ended up as it did may be related to size - although it's only a bit smaller than Earth, that may be the initial factor that set its fate in motion - for example, its lithosphere in general appears to be thicker and higher viscosity on Earth, which could have hindered or prevented plate tectonics, and thus subduction of carbonates.

Either way, it's a mess now at the surface (though rather comfy ~55km up ;) ). And I'm not so sure I buy into some of the proposed ways to fix it (terraforming). For example, some have suggest mass drivers ejecting the atmosphere. Let's just say you can pull it off, and then you start building oxygen in the atmosphere - what happens next? The crust is something like 7-9% FEO; it's going to rust away whatever oxygen you make in short order.

Interestingly, I'd argue that this is possibly the salvation to Sagan's airborne-microbe concept for terraforming Venus. The main criticism is that if you engineered some sort of carbon-sequestering microbe on Venus (or artificial equivalent), you'd end up with a deep surface layer of graphite surrounded by some hugely hot, dense oxygen layer, and the atmosphere would explode. But that would never happen; at Venus surface temperatures and pressures, the surface rocks would rust away the oxygen as fast as it was created, even in tiny quantities, with the wind blowing the dust around to collect at low/eddy areas. So you're laying down bands of carbon and iron oxide as you burn through the planet's iron buffer. Where have we seen this before? Right, Earth, ~2,3 billion years ago, banded iron formations. Just like on Earth, you'd eventually burn through the iron and start to accumulate oxygen. But by then the graphite is already underground, buried in iron dust.

It's not a fast process. But it has precedent. Microbes already rusted at least one planet, and that planet's surface conditions weren't nearly as favorable for rusting as Venus's.

Comment Re:Catastrophic man-made global warming (Score 0, Troll) 269

I don't know how China managed to melt so much arctic ice, leading to the absurd situation that just a couple days before the winter solstice this year I went on a hike through the snowless mountains in Iceland among chirping songbirds digging for worms. All I have to say to China about this is: Best. Conspiracy. Ever. Well played, China. Well played.

Comment Re:News from other countries... (Score 2) 45

Well, when it comes to space budgets....

NASA: $19,3B
ESA: $5,8B
Roscosmos: ~$2B/yr
JAXA: $2,0B
CNSA: $0,5B official / $1,3B est.
ISRO: $1,2B

It's not just US bias that leads to most stories coming from NASA. NASA really does spend the most on space research and exploration, by large margins.

Still, the public perception is that NASA's budget is far more than it actually is.

Comment Re: Note that what's large... (Score 4, Informative) 84

Venus has multiple "tropopauses" and "stratospheres", depending on how you define them. The atmosphere is like a layer cake with multiple convection zones (like Earth's troposphere) separated by areas of dynamic stability (like Earth's stratosphere). And again, ~50-70km is an awfullly long way from the surface, and surface winds are weak. But, there's a lot about Venus that we don't understand.

Comment Note that what's large... (Score 3, Informative) 84

.... is the size, not the intensity. The air moves only slightly faster or slower than the surrounding atmosphere as one passes through the wave.

They weren't expected on Venus, though. Venus's surface is dozens of kilometers down, thick and "soupy" there, transitioning to thinner layers above. It was surprising to see that surface features that far away, in a fluid that can compress, would still make clear phenomena like gravity waves in the high atmosphere.

Comment Am I the only one... (Score 5, Interesting) 129

.... who can't help but cheer at my screen when they nail one of those landings? Now I finally understand how sports fans feel when they watch a game and do the same thing ;)

One thing nobody can deny about them is optimism. ;) Seriously, their IPS numbers are, pardon the pun, out of this world. $200k per booster launch. $500k per tanker launch. I mean, really? Good luck with that. No, seriously, good luck with that; I won't be expecting anything close to that, but please by all means prove me wrong ;) ITS would be a great system to have, I've been playing around with some Venus trajectories with it recently. Looks like it can do a low-energy transit with nearly 300 tonnes of payload from LEO and back again with the same, over 400 if starting at a high orbit - but from an economics perspective the high energy transfers actually make more sense.

I noticed a lot of people were confused about why Musk wanted the trips to be so short and was willing to sacrifice so much payload to do so - many assumed it had to do with radiation or something. But the issue is, when your craft costs so much but your launch costs are cheap, you can't have it spending all of its time drifting in deep space, you need to get it back for a new mission as soon as possible. There's a balancing point, in that if you try to go too fast, you reduce useful payload below the point of making up for it with going faster - but a minimum energy trajectory is just not optimal when the ratio between launch costs and transit vehicle cost is so extreme. I come up with the same thing from Venus as they were getting for Mars, although for the Venus case you end up aerobraking to a highly elliptical orbit rather than to the surface for ISRU refill (you need ISRU, but for the ascent stages, so it's not realistic to do so for the return stage in the nearer term). So for Venus they get no refill like on Mars, but they also don't have to do a powered landing nor do an ascent on return - it's six of one, half a dozen of the other. Both are quite accessible with it.

Comment Re:Great strides (Score 1) 129

It depends what you mean by "refurbishing"; each element is different.

The solid rocket boosters, for example, suffered a hard impact into salt water. They then had to be fished out of the water. And of course you don't just "refill" a SRB, they have to be taken apart and recast, then put back together.

The ET is disposable, and had to be rebuilt from scratch.

The orbiter was legitimately reusable, but with design flaws.

I don't blame the shuttle program - they were sort of pigeonholed into this dead end by circumstances. The concept came about during the heyday of the Apollo Programme, when NASA budgets were serious. It was supposed to be a much more reusable, much more maintainable, and somewhat smaller system. It was supposed to then have a huge flight rate supporting all of these big projects that were on NASA's docket, including a permanent moon base and a huge manned orbital station dwarfing ISS, which was supposed to replace Skylab.

But of course, Vietnam and the realities of having soundly trounced the USSR in the space race led to their budgets being slashed, which pushed the program into ever more untenable positions until it was nothing more than a jobs programme. Forget full flyback reusability of all parts. Forget the titanium frame for the shuttle, which would have let it run hot and thus not required so sensitive of a TPS. Go begging for money and be forced to modify the design to meet Air Force requirements, pushing you into an inferior design position. On and on.

If I'd fault them for anything, it'd be for going straight for a full reusable workhorse rather than a small-scale pilot programme first. But those were the days of optimism. Optimism which only recently seems to start being regained.

Either way, the Falcon boosters are a very different beast. A vertical soft landing is hugely different from the SRBs, yet the thermal issues are far easier than with the Shuttle. And the Merlins were designed from the start under the principle of preventing the need for a full teardown. That doesn't mean that they will be cheap to reuse. But it does mean that they have the possibility of it.

I do think SpaceX had a rather clever strategy, in that while their goal was reusable, they made a rocket that in the process was cheap as a disposable. So they could get volume and flight history while working on getting the kinks out. They may have flown too close to the sun with the densified propellants and (externally) unlined COPVs, but obviously, with a company like this, their whole existence is to push the envelope.

Comment Re: Awesome (Score 3, Insightful) 129

Most of Europe agrees with you. And even the US agrees with you up through high school plus with various forms of assistance for college, including state-subsidies, particularly for state colleges, and federal subsidies (direct subsidies, tax credits, and tax breaks), roughly $80B/year each. Pell grants alone cost the government $35B.

Comment Re:No Gut no Glory (Score 1) 67

To be clear:

  * Getting the failure rate down in the lower tenths of a percent or better is what they need to be able to ~10x their launch rate and still be economically viable, since a pad explosion will leave them stuck for just as long and scare off just as high a percentage of their customers whether they're launching 12 a year or 120.
  * SpaceX wants to have reliability like airplanes, and has talked about this frequently.
  * What they want to achieve, and what they need to achieve, are not the same thing. They do not need to achieve airplane-like reliability for the Falcon 9 to be viable.
  * That said, if they ever want to achieve their ultimate IPT plans, they absolutely will need airplane-like reliability. Because they're calling for ~1000 launches per booster on that thing with a turnaround cost of ~200k. They really cannot have anything go wrong with it.

Comment Re:No Gut no Glory (Score 1) 67

It most certainly would be extreme reliability by the standards of the launch industry. The only ones that have better reliability than that that don't have nearly a statistically significant enough number of launches under their belt to assert that. Aka, "they haven't had a failure yet but nowhere near the several hundred launches required to assert a lower fraction of a percent or better failure rate".

We're not talking about airplane reliability here, we're talking about economics (the title of the article is "SpaceX Accident Cost it Hundreds of Millions"). Airplane-like reliability is for the future. We're living in the present.

All COPVs use an inner liner. The problem with SpaceX's COPVs is that they have no outer liner to separate the carbon fibre from the LOX. Outer liners are optional. SpaceX didn't use one. They lost a rocket because of it. They're going to keep trying doing without one. I really hope it doesn't cost them another. CF and LOX aren't fast friends.

Comment Re:Permission? (Score 1) 63

It's hard enough to find affordable LOX dewars. Seems like little ones cost about as much as big SUV-sized tanks. Everyone has LN2 dewars for sale, but you don't put LOX in a LN2 dewar as a general rule unless you're absolutely positive it has no organics (and preferably no silicone) in it, or certain metals. Otherwise it can get a bit... "explodey". The simpler, all-stainless LN2 dewars usually don't have lids, which with LOX would be just plain stupid. You can find used LOX converters online for very cheap, but they generally only will take LOX in, you can only get GOX out.

What I'm saying is if anyone happens to run into an affordable LOX dewar, drop me a line.... ;)

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